POM_C Kongsberg Simrad Seaflex

Program Operation Manual

P7009/C 1

Program Operation Manual Kongsberg Simrad SeaFlex

Riser Management System

Kongsberg Simrad SeaFlex RMS / Development Driller I

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Document revisions Rev Date Written by Checked by Approved by

A 20.09.02 M. Hklie B 04.10.02 B.Tveraaen M. Hklie C 13.08.03 K. Abelsen M. Hklie D


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Contents

1 GLOSSARY ................................................................................................................... 7

2 SYSTEM OVERVIEW ................................................................................................ 12

3 USER INTERFACE..................................................................................................... 21

4 SYSTEM OPERATING PROCEDURES .................................................................. 31

5 MAIN RMS INITIALISATION PROCEDURES.................................................... 34

6 CO-ORDINATE SYSTEMS AND UNITS............................................................... 52

7 ADVISORY AND MONITORING FUNCTIONS ................................................. 55

8 CALIBRATION FACILITIES.................................................................................... 82

Appendix I List of tags

Table of Figures Figure 1 RMS System Configuration................................................................................. 15

Figure 2 Schematic overview of instrumentation systems utilised by RMS................... 18

Figure 3 Example display ................................................................................................... 22

Figure 4 Display organisation ............................................................................................ 23

Figure 5 Menu bar ............................................................................................................... 23

Figure 6 Alarm indicator display ....................................................................................... 24

Figure 7 Alarm summary.................................................................................................... 26

Figure 8 Export Alarms & Events....................................................................................... 27

Figure 9 View Alarms & Events ......................................................................................... 27

Figure 10 Riser make-up view for riser modelling ........................................................... 36

Figure 11 View of riser joint data for a particular joint (Typical) .................................... 38

Figure 12 Static Calculator view and control .................................................................... 41

Figure 13 Edit current profiles dialog box......................................................................... 41

Figure 14 Position plot view based on static calculator.................................................... 43

Figure 15 Riser shape plot based on static calculator ....................................................... 44

Figure 16 Well constants dialog box .................................................................................. 45


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Figure 17 Operational limits user interface ....................................................................... 46

Figure 18 Override and back-up sensor data dialog box.................................................. 49

Figure 19 Operational mode............................................................................................... 50

Figure 20 Reference headings for riser components......................................................... 54

Figure 21 Main data view ................................................................................................... 56

Figure 22 Position plot view............................................................................................... 57

Figure 23 Subwindow with ReposData view.................................................................... 58

Figure 24 Mini Position PlotView ...................................................................................... 59

Figure 25 Top Tension view................................................................................................ 60

Figure 26 Tensioner Pull view............................................................................................ 61

Figure 27 Tensioner Stroke view........................................................................................ 62

Figure 28 Telescopic Joint stroke view............................................................................... 63

Figure 29 Subwindow view of telescopic joint stroke, mean and instantaneous ........... 64

Figure 30 Flex joint Angles view. ....................................................................................... 65

Figure 31 Inclination view .................................................................................................. 66

Figure 32 Riser loads display.............................................................................................. 67

Figure 33 Mean Riser loads and utilisation for selected joints......................................... 68

Figure 34 Connector capacity envelope and actual loading (X)....................................... 69

Figure 35 Time To Go. Note that the case identifier is given by the SDPM system and the text in the plots above are for illustration purpose only..................................... 71

Figure 36 Time To Go: Riser Limits. Note that the case identifier is given by the SDPM system and the text in the plots above are for illustration purpose only. ............... 72

Figure 37 Time To Go: Riser Shape. Note that the case identifier is given by the SDPM system and the text in the plots above are for illustration purpose only. ............... 73

Figure 38 Time To Go: Rig drift-off trajectory Note that the case identifier is given by the SDPM system and the text in the plots above are for illustration purpose only........................................................................................................................................ 73

Figure 39 The Select Tags for HTV dialog box .................................................................. 78

Figure 40 Historical Trend Viewer..................................................................................... 79

Figure 41 Execution Control ............................................................................................... 83

Figure 42 Calibrate BOP Inclinometer display.................................................................. 85

Figure 43 Calibrate TJ Inclinometer display...................................................................... 86

Figure 44 Calibrate Wire Lengths display. ........................................................................ 88

Figure 45 Correction of wire lengths for upper riser angle.............................................. 89

Figure 46 Tensioner Pull correction ................................................................................... 90


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Document history Rev.A Issued for internal check Rev.B Issued for FAT Rev C Issued for SW release


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1 GLOSSARY

Abbreviations ARA Acoustic Riser Angle system

BOP Blow-out Preventer

CCW Counter-clockwise

Cd Drag coefficient

CG Centre of Gravity

CSAi Cross sectional internal area of a pipe

CW Clockwise

DGPS Differential GPS

Dhyd Hydrodynamic diameter

DP Dynamic Positioning

DPC DP Controller

ERA Electrical Riser Angle system

EDS Emergency Disconnect Sequence

GPS Global Positioning System

HPR Hydroacoustic Position Reference

HTV Historical Trend Viewer

IRJ Instrumented Riser Joint

LFJ Lower Flex Joint

LFJA Lower Flex Joint Angle

LMRP Lower Marine Riser Package

LRJ Lowermost Riser Joint

MRU Motion Reference Unit

OD Outer diameter

OS Operator Station

PMS Power Management System

RKB Rotary Kelly Bushing

RMS Riser Management System

POM Program Operation Manual


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RPM Revolutions Per Minute

SDP Simrad Dynamic Positioning

SDPM Simrad Dynamic Position Mooring

SJ Slip Joint (Telescopic Riser Joint)

SMYS Minimum yield strength of steel

SR Support Ring (Tension Ring)

STD Standard deviation

SVC Simrad Vessel Control

TJ Telescopic Joint (Slip Joint)

TOE Tension Offset Envelope

UF Usage Factor, i.e. the allowable utilisation of the material minimum yield stress.

UFJ Upper Flex Joint

UFJA Upper Flex Joint Angle

UPS Un-interruptible Power Supply

UR Utilisation Ratio; the utilisation of the allowable stress

URJ Upper Riser Joint

UTM Universal Transverse Mercator

VRS Vertical Reference System

Wth Wall thickness of pipe

RMS and Marine Terminology

Bearing The horizontal direction of one terrestrial point from another, expressed as the angular distance from a reference direction, clockwise through 360.

In the RMS context, bearing is more specifically used as the horizontal direction of an inclination. E.g., if a vessel is inclined to East, the inclination is said to have a true nautical bearing of 90 degrees.

Cartesian system A co-ordinate system where the axes are mutually perpendicular straight lines.


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Co-ordinate system Geographic positions may be referenced to different co-ordinate systems: Cartesian or geodetic.

Datum Mathematical description of the shape of the earth (represented by flattening and semi-major axis).

Geodetic system A mathematical way of dealing with the shape, size and area of the earth or large portions of it.

Heading The horizontal direction in which a vessel actually points or heads expressed in angular units from a reference direction, usually from 000o at the reference direction clockwise through 360o.

Inclination Angular deviation from vertical. In RMS context, used to denote the tilt of a BOP stack, a riser or a floating vessel.

Rated load The maximum tensile load that a riser coupling are allowed to operate with.

Reference origin The reference point of the first position-reference system that is selected and accepted for use with the system. The origin in the internal co-ordinate system.

Relative bearing The bearing of an object relative to the vessels heading.

Relative wind The speed and relative direction from which the wind appears to blow with reference to the moving vessel.

Transponder In this document, this is the physical reference of a position-reference system. For example: for an HPR system this means any deployed transponder; e.g. differential angle transponder at lower flex joint

True bearing Bearing relative to true north.


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Windows Terminology

Check box A small square box that appears in a dialog box and that can be turned on and off. A check box contains a tick mark when it is selected and is blank when it is not selected.

Choose To perform an action that carries out a command in a menu or dialog box. See also Select.

Click To press and release a trackball button, without moving the cursor. If no trackball button is specified, the left button is assumed.

Command A word or phrase, usually found in a menu, that you choose in order to carry out an action.

Command button A rectangle with a label inside that describes an action, such as OK, Apply or Cancel.

When chosen, the command button carries out the action.

Cursor The pointer symbol that is displayed on the screen and that can be moved with the trackball.

Dialog box

Dialog box A box that appears when the system needs additional information before it can carry out a command or action. See also Check box, Command button, List box, Option button and Text box.

Double-click To perform Click action twice.

Drag To press and hold down a trackball button while moving the trackball. For example, you can move a dialog box to another location on the screen by dragging its title bar.


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Greyed Describes a command or option that is listed in a menu or dialog box but that cannot be chosen or selected. The command or option appears in grey type.

List box A box within a dialog box containing a list of items. If the list of available items is longer than the displayed list box, the list box will have a vertical scroll bar that lets you scroll through the list. A list box may be closed when you first see it. Selecting the down arrow next to the first item in the list will display the rest of the list.

Menu A group listing of commands. Menu names appear in the menu bar beneath the caption bar. You use a command from a menu by selecting the menu and then choosing the command.

Option button A small round button appearing in a dialog box (also known as a "radio" button). You select an option button to set the option, but within a group of related option buttons, you can only select one. An option button contains a black dot when it is selected and is blank when it is not selected.

Option button group A group of related options in a dialog box. Only one button in a group can be selected at any one time.

Point To move the cursor on the screen so that it points to the item you want to select or choose.

Select To indicate the item that the next command you choose will affect. See also Choose.

Text box A box within a dialog box in which you type information needed to carry out a command. The text box may be blank when the dialog box appears, or it may contain text if there is a default option or if you have selected something applicable to that command. Some text boxes are attached to a list box, in which case you can either type in the information or select it from the list.


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2 SYSTEM OVERVIEW

Scope of this manual This Program Operation Manual (POM) describes the System Software of the RMS. The following main aspects are covered:

Monitoring and Advisory Module System overview

User interface

Initialisation procedures and riser modelling

Operating procedures

Calibration procedures

Telescopic Joint inclinometer hook-up

The RMS system The Kongsberg Simrad SeaFlex Riser Management System (RMS) is a computerised system enabling on-line monitoring of riser responses and vessel behaviour relevant for safe operation of the Marine Drilling Riser system.

The RMS is integrated with the Kongsberg Simrad Dynamic Position Mooring (SDPM) system and gives advice on recommended position setpoint and safe areas in order to keep riser flex joint angles and connector forces within acceptable limits.

The RMS also monitors safety margins for emergency disconnect scenarios in terms of a time estimate for available time for the operator to initiate the emergency disconnect procedure.

System objectives and functions The primary objectives of the RMS are to maximise operability and maintain safety of marine drilling riser operations.

The following "undesirable event scenarios" are considered:


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High internal wear of the riser and flex joints, due to the rotating drill string; which could eventually lead to riser penetration and loss of well control

Bending and fatigue of the through-riser equipment, near the flex joints, in drilling or non-drilling mode

Excessive tension, bending and shear in the wellhead or LMRP connectors.

Bending and shear in the wellhead or LMRP and BOP connectors that may obstruct connector release

Stroke-in or stroke-out of the telescopic joint or riser tensioners, which could severely damage the riser system and/or the wellhead

Loss of tension in the riser, excessive flex joint angles and riser buckling

Excessive tension in the riser, wear of tensioners and riser

Loss of station (drift-off, mooring line break) with riser connected, emergency disconnect

To avoid and/or control such events, the following functions have been implemented:

The top and bottom riser flex joint angles are monitored. Alarms are triggered when flex joint angles exceed given limits, e.g. defined by acceptable wear or equipment stress. Alarms are tri-state, green/yellow/red.

The flex joint angles are input to the RMS vessel position optimisation module, which displays a recommended vessel position set point and the safe area around it. As long as the Rotary Kelly Bushing (RKB) is kept inside the safe area, the flex joint angles will be within the limits specified by the operator. The RMS provides this information for three operational modes: Drilling, Non-Drilling and Prepare-for-Disconnect, each defined with a separate set of operational limits by the operator.

Monitoring of the stroke of riser telescopic joint and tensioners. This includes statistical analysis of the stroke history, to determine when there is a risk of a full stroke in/out. Alarm indicators are lit if there is a certain risk of a stroke-out or stroke-in.


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Monitoring of the tensioner pull forces, and calculation of the total riser top pull. Applying the riser weight and geometry data contained in the riser model, the tension distribution along the riser all the way down to the wellhead is calculated. Alarm indicators are lit if top or bottom tension violates the high/low limits specified by API RP 16Q for marine drilling risers.

A Time-To-Go simulation function. This is a computer simulation of a vessel drift-off or a transient vessel motion due to anchor line break, based on the Kongsberg Simrad Vessel Motion Prediction module when in DP-mode or the PM Online Consequence analysis in PM-mode. RMS uses the predicted vessel excursions to determine the riser responses and at what point in time the operational limits will be violated. Boundary conditions and environmental conditions are taken from on-line measurements and represent the present operational conditions. At pre-set intervals, this simulation will execute automatically, and estimate the time available for a safe emergency disconnect for the most critical failure modes.

System configuration The system configuration is described in Figure 1 on the next page.


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Figure 1 RMS System Configuration


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System principles The RMS system principles are described in the following sections.

Sources of input data The RMS program is dependent on a high number of input data that must be available and have correct values in order to produce useful and reliable results. It is therefore emphasised that all user-defined input data be carefully entered and double-checked. A number of default values are provided to reduce the amount of keyboard entries. However, also default values should be evaluated, and updated as required.

The input data can be divided in classes as follows:

On-line sensor data

Manual input set-up data

Manual override of sensor signals

System calibration and configuration settings

All the required sensor signals are received via the SDPM network. The sensor data-sampling rate is 1 Hz. Further; data for the riser system must be entered manually by the operator to define the riser configuration for a specific well.

The RMS system has been configured for operation onboard the Development Driller I. The configuration settings include the vessel geometry, tensioner geometry, and other vessel constants, which shall not normally require user intervention. The configuration settings are not detailed herein.

Both when defining input parameters, and reading output displays, the user must observe the units and co-ordinate systems that the input/output data are referred to.

In certain cases (e.g. in case of dubious or absent sensor signals) the operator may want to override a sensor signal by a user-defined value or by back-up sensor if available. The RMS has provisions to do this for most of the sensor signals. Using this option requires that the operator has reliable information to enter in place of sensor data that the information is updated as required.


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On-line sensor data During system operation, the following input data shall be available via SDPM.

BOP Control System: BOP stack inclination, LRJ inclinations and, mud pressures representing the mud pressure in the main riser bore.

Simrad Dynamic Positioning Mooring (SDPM) System: Vessel motions including vessel motion predictions, vessel and wellhead positions and heading.

Tension Control System: Tension and Stroke.

Upper riser inclinometer (Hydril)

A schematic overview of the instrumentation systems utilised by RMS is given in Figure 2.


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Figure 2 Schematic overview of instrumentation systems utilised by RMS

Stroke and pull from tensioners

Rig position, heading and motions from SDPM

Telescopic joint inclinometer (HYDRIL)

Lower riser inclinometer

Stack inclinometer and mud pressure


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The riser model The RMS system is based on a riser model, which contains a mathematical description of the riser, including characteristics such as geometry, weight and buoyancy distribution, top tension, mud weight, hydrodynamic properties and structural strength data.

The riser model has to be tailored for each particular well with respect to the actual water depth and deployment sequence of various riser joint types. In order to facilitate the generation of the riser model, all necessary data for each particular riser joint type have been stored in the system at the delivery of the RMS.

A simple graphical user interface provides the operator with a tool to stack the various riser joint types upon each other in the desired sequence to define riser space out for the actual well. Weight and geometry properties for the riser string are update instantaneously.

Manual set-up data In addition to the riser model described above, a number of field/operation dependent set-up data must be entered by the system operator before commencement of operation of the RMS at a new location. The set-up data can be divided into the following groups:

Operational limits: Limits that trigger the different alarm levels for the monitored riser parameters.

Well constants: Water depth, orientation of BOP etc.

Calibration: (See next section)

Some default values are given and the values may be changed as required. During program start-up, the user can select to read and edit the riser model and the set-up data from an existing data file. Therefore, it is not required to enter a great amount of set-up data every time the program is started.

Every time the program is stopped intentionally or when changes to the set-up data have been introduced, the user has the opportunity to save the current set-up data in a new file, for later use.


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Calibration and configuration settings At delivery of the RMS, most of calibration and configuration settings have been properly set up and adjusted for optimal performance of the system. These settings shall normally be maintained from well to well unless some of the sensors that are interfaced to the RMS have been replaced, moved or adjusted in some way or another.

The Calibration facilities comprise unit conversions, co-ordinate transformations, offsets and initialisation procedures.

One exception is the tensioner stroke measurements, which have to be re-calibrated each time one or more of the tensioner wires have been re-terminated or when adjustments affecting the total wire lengths have been made.

Execution control parameters: Constants affecting time averaging and extreme value prediction.


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3 USER INTERFACE This section gives an overview of the RMS operator station and the user interface.


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The operator station The RMS operator station includes a display screen for monitoring and operation of the system. The operator station will include a keypad for numeric input and a track ball and for normal operator intervention during operations this will be sufficient. For saving or renaming files the normally hidden alphanumeric keyboard must be used.

The operator station will be similar to the SDPM-OS and reference is made to the Operator Manual for the SDPM for more details.

Display organisation The display interface uses standard Microsoft Windows NT operating features such as menus and dialog boxes.

Figure 3 Example display


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The display is divided into a number of predefined areas as shown below.

MENU BAR

ALARM INDICATOR

SUBWINDOW 1

MAIN VIEW

SUBWINDOW 2

DATE/ TIME

USER LEVEL OPERATION MODE PROGRAM MODULE

ALARM

Figure 4 Display organisation

Menu bar The menu bar provides command menus that allow you to access the available dialog boxes and display views.

Figure 5 Menu bar

Alarm indicator The alarm indicator contains alarm lamps for the most important monitored riser parameters and lamps that indicate valid or non-valid data from the interfaced control and instrumentation systems.

The left row with square alarm indicators lit yellow or red when the respective operational limits are exceeded. These indicators include the flex joint angles, tension and stroke. Normal status is green.


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The right row with circular alarm indicators represents the status of the data communication with the external systems. Normal status is green. When an external system transmits non-valid data for one or more parameters, the alarm status turns yellow. When an external system transmits non-valid data for all parameters, the alarm status turns red. The alarm status will also be red when the communication with the external system is down.

Figure 6 Alarm indicator display

Main view The main view shows the selected display main views. Clicking View on the menu bar gives access to the main display views and subwindows. The available main display views will be explained in detail in chapter 7.

Subwindow 1 and 2 Graphic and numeric data are displayed in the subwindows. The subwindows are available under the View menu. The same display views are available in both subwindows. Any combination of different views can be selected in the two subwindows.

The available display views in the subwindows will be explained along with the monitoring functions in chapter 7.

Date and time Current system date and time information is displayed in the lower left corner.


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User level The RMS has three user levels in order to protect the system set-up and configuration parameters from unauthorised or unintended changes during operation. The user level can be changed by clicking in this area followed by the entering of user name and password in the dialog box that appears.

The three user levels have been defined as follows:

1. Normal user No access to Edit, Calibrate and Exit menus

2. Set-up user No access to Calibrate menu

3. Super user Access to all menus

Alternatively click Log-in or Log-out on the File menu as desired.

Passwords can be assigned to the different users.

Operational Mode This area denotes the selected operational mode, i.e. Drilling, Non-Drilling or Prepare for disconnect. Change of operational mode is performed by clicking Mode on the main menu and select the desired mode. Different operational limits may be defined for each operational mode by selecting the Operational Limits menu under the Edit menu.

Program Module By clicking in this area the RMS software version and vendor information will appear.

Alarms This area will turn intermittent red when alarms are triggered. The number combination X/Y indicates number of active alarms, X, and number of unacknowledged alarms, Y.

The area will turn intermittent red if any yellow or red alarm in the alarm indicator area lit.


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By clicking in this area an alarm summary will appear on the screen with information indicating the situation that caused the alarm. The alarm summary displays the parameters tag name and a reference list for all tag names where alarm limits have been defined are included in Appendix I.

The alarm log includes different Alarm States as follows:

NORMAL

DISCRETE

LO LO

LO

HI

HI HI

The DISCRETE alarm state is accompanied by a short description of what caused the alarm. The other alarm states indicate the limit value that has been exceeded. The actual LOLO, LO, HI and HIHI limit values are listed in the tag list in Appendix I.

Figure 7 Alarm summary

You acknowledge an alarm by clicking the red ACK button.

You close the alarm summary by clicking OK.

If you want to export alarms and events to file, select Export Alarms & Events from the File menu. The view shown in Figure 8 below will then be displayed. You here get the option to export directly to file or view the alarms and events on screen, as shown in Figure 9.

Note that the angle unit in the alarm summary is radians.


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Note that if an alarm has been triggered and the event that caused the alarm has returned to normal state, the message in the Alarm Summary View is automatically removed even if the operator has not acknowledged it. However, a complete track of all alarms and events can be found by use of the Export Alarms & Events function described above.

Figure 8 Export Alarms & Events

Figure 9 View Alarms & Events

Dialog boxes Data entry is achieved using dialog boxes initiated from menu items, or by clicking on graphical symbols in the display views.

Dialog boxes pop up in the display area but you can move them as required.


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The dialog boxes may contain information that the operator can change, and results and information that are fixed. All data that can be changed by the operator will have a white background or there will be small arrows in front of the alphanumeric field to scroll text entries or increase/decrease numerical values.

For white fields without the small arrows, numerical data are typed in directly by use of the keypad. For white fields with the small arrows, numeric data can be changed by scrolling the arrows up or down. Alternatively, data can be typed in directly.

For fields with text and the small arrows in front, all available selections will pop up when you click in the text field.

Data you enter in a dialog box are not taken into account until you confirm the input by clicking Apply or OK.

If you click Apply, the changes that you made are applied and the dialog box remains displayed.

If you click OK, the changes that you made are applied and the dialog box is removed from the display.

Click Cancel to close the dialog box without action.

Display views Types of information displayed The RMS display views consist of graphic and alphanumeric information. Some of the views contain buttons that allows the operator to view additional information or to enable or disable sensors that are not in use or that provide invalid data.

All main views and subwindow views are selected from the submenu under the View menu.

Changing axes on plots and scrolling tables You can change the scale of the axes of most plots by clicking and marking one of the numbers on the axis you want to change. Enter a new number and the axis will change the scale accordingly.

Some of the plots also have a sliding bar to use as a zooming device. Drag the indicator to zoom in and out or, simply click on the desired range and the indicator shifts to this position.

Some of the plots have a reset button (R-button) that can be used to re-scale the plot if you have changed the scale of the axes.


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Some of the numerical displays have large tables of data where only a certain portion can be displayed on the screen. E.g. the riser make-up plan under the Edit menu. These tables are equipped with a sliding bar to scroll up and down.

Available main views The following display views are available:

PositionPlot Shows the vessels position and heading together with the BOP position and orientation, recommended position and allowable area for vessel positioning.

TJ Stroke Shows the time series for the mean and present telescopic joint stroke together with alarm limits. The display also contains numeric data.

Top Tension Shows the actual riser top tension and latest time history together with alarm limits.

Tensioner Pull Shows the tensioner pull for each individual tensioner cylinder, both graphic and numeric. Buttons for enabling/disabling tensioners in use/not in use.

Tensioner Stroke Shows the tensioner stroke for each individual tensioner cylinder, both graphic and numeric. Buttons for enabling/disabling tensioners in use / not in use.

Flex Joint Angles Shows magnitude and direction of lower and upper flex joint angles. Button for selecting time history view for flex- joint angles.

Riser Loads Displays the effective tension diagram for the whole riser length and the bending moment distributions for the upper and lower part of the riser.

Connector Loads Displays the actual LMRP and BOP connector loads in their respective capacity envelopes. Horizontal X-mas tree connector loads included if present.

Time To Go Shows details of vessel drift off and riser response time histories for anchor line break and blackout events.


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A selection of SDPM views will also be available on the RMS-OS. The SDPM view is activated by clicking the SDPM-OS icon on the auto hide taskbar.

Available subwindow views The subwindows in the View menu contains the following views:

Main Data Presents a numeric summary of all main data such as flex joint angles, top tension, stroke, time to go estimate, mud density and LMRP connector tension.

Mini Position Plot Presents a small view similar to the main PositionPlot view.

TJ Stroke Presents small view of the time history of the mean and instantaneous telescopic joint stroke.

Inclinations Numeric display of mean inclinations of BOP stack, LRJ, Telescopic Joint and vessel inclinations in a global co-ordinate system together with vessel heel and trim.

Repos Data Presents numeric data for actual vessel offset from well head and recommended reposition vector.

Riser Loads Table Numeric display of riser pipe stresses and riser coupling loads and utilisation ratios for selected riser joints.


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4 SYSTEM OPERATING PROCEDURES This section provides procedures for starting and stopping the system.


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RMS program start-up To start the RMS operating station (OS) and program, perform the following steps:

Power-up the RMS-OS. This will initiate an autostart of the RMS software and the related SDPM software.

If you have exited the RMS you can restart RMS by double-clicking the RMS program icon on the desktop.

You will be prompted to specify a set-up file. By default, the most recently saved set-up file will be suggested. If you click Cancel you start with a blank set-up file with default values.

You will also be asked whether you want to continue storing data onto the existing database or to initiate a new. If the RMS has been stopped during a drilling operation and restarted again you may want to continue with the present database. If you are starting a new operation you should click Cancel and follow the instructions on the screen to initialise a new database and store or delete the old database

After a while the program shows the default display views. Check that all the indicator lamps in the upper right corner of the Alarms Indicator display are green. This to ensure that the program receives input from all the connected systems.

Auto log in has been initiated for the lowest user level. In order to log in at a higher user level, click Log in on the File menu.

For proper RMS program function, it is required that the SDPM and SVC systems are running.

The operator may swap SDPM views and RMS views by selecting processes on the Windows NT task bar.


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RMS program shut-down Prior to program shutdown, it is recommended to check the present set-up data first. When the program terminates it will attempt to save the current settings onto a set-up file for later use.

The shutdown procedure is as follows:

Click Exit on the File menu.

Specify file in which to save current set-up. It is recommended to use a name identifying the location and date/time. If the user selects Cancel, no error message appears and no set-up file is saved.

It is not possible to overwrite an existing file.

Storing to the Database will automatically be shut down and the database closed.

Press Quit when the dialog box below occurs. This will finalise the shut down process.


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5 MAIN RMS INITIALISATION PROCEDURES This section provides procedures for set-up and initialisation of the RMS system for a particular well.


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Set-up Once the RMS software is up and running it will be necessary for the operator to go through the Edit menu. The riser model and all necessary data to configure the RMS for a new well are entered via submenus under Edit on the menu bar.

Edit contains the following sub menus:

Make-up User interface for riser modelling and static riser calculations.

Manual Settings User interface for entering, enabling and disabling user defined sensor data and back-up sensors.

Well Constants User interface for entering of data relevant for the particular well operation such as water depth, BOP orientation and horizontal X-mas tree height and connector capacities if present.

In addition, calibrations according to the procedures in Section 8 should be performed as required.

Entering a riser make-up plan Click Make-up on the Edit menu and the make-up dialog box pops up. Here, the operator can enter a new riser make-up plan, or modify the make-up plan loaded from an existing set-up file.


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Figure 10 Riser make-up view for riser modelling

Use the pointing device to click on the miniature up/down scroll arrows at the white control arrays. Select Number off and Joint Type, for each joint type to be included in the riser string. The riser stack-up shall be defined in a top-down sequence.

Start at the bottom row, by entering 1 and scrolling to the BOP type. Proceed with adding one LMRP, and then by adding riser joints in bottom-up sequence (adding number off and type as you go) all the way up to and including the telescopic joint.

The vessel operational draught used for required riser length calculation must be entered manually.

At the bottom end of the view, note the indicators displaying True Make-up Length and Required Make-up Length. The difference between these is displayed as Theoretical Stroke, and reflects the telescopic joint stroke that would result, for the user-defined riser make-up and water depth, and the specified vessel draught.

As you go on adding joints, the True Make-up Length will, of course, increase, and the Theoretical Stroke is reduced. The Theoretical Stroke is calculated with no regard to riser stretch, temperature or pressure expansion, or sagging due to current or vessel offset. It is mainly intended as a tool for input consistency check.


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As riser joints are added, the submerged weight of the riser is updated and displayed. The user has to specify the mud weight to be used in the calculations.

Note that vessel draught and the mud weight entered by the operator in the Make-up view will have no effect on the monitoring functions of the RMS.

The submerged weight is displayed for:

The riser alone (from lower flex joint up; for connected mode evaluation)

The riser plus LMRP (useful for estimating hang-off weight)

Furthermore, the top tension alarm limits are displayed:

The Dynamic Tension Limit (DTL) according to API RP 16Q. (Upper Red limit)

90% of DTL, max. permissible utilisation, Ref. API RP 16Q (Upper Yellow limit)

Tmin, minimum safe top tension, with safety margins according to API RP 16Q (Lower Yellow limit)

Tsrmin, minimum top tension to prevent riser buckling, assuming no tensioner failure (Lower Red limit)

In the planning phase, it may be useful to check the feasibility of a given riser and buoyancy configuration by selecting the maximum permissible mud weight for the actual well.

Riser joint inventory All riser joint properties have been specified at delivery of the RMS based on specifications given by the customer. To inspect the riser joint properties that are stored in the RMS set-up file click View Joint Definition button in the Make-up view. Changes in the riser joint inventory are normally not anticipated but can be performed in co-operation with the RMS vendor.

The list of information stored for a typical riser joint is shown on the next page. The desired joint type is selected by clicking in the green box at upper left. For abbreviations see chapter 1.


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Figure 11 View of riser joint data for a particular joint (Typical)

Explanation of the joint data:

Joints available Number of joints of this type available onboard

Length Effective make-up length of joint type

Dry weight Dry weight in air of joint type

Subm. Wt. Submerged weight in sea water (water filled)

Buoy. Dry Wt. Dry weight in air of buoyancy modules on this joint type

Buoy. Net Uplift

Net uplift force of buoyancy modules on their joint type

CSAi Ri&K&C Internal cross sectional area of main riser pipe + choke and kill lines.

CSAi aux. lines Internal cross sectional area of auxiliary lines

OD Main Pipe Outer diameter of main riser pipe for structural calculations

Wth. Main Pipe Wall thickness of main riser pipe for structural calculations


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OD K/C lines Not used in this program version

Wth.K/C lines Not used in this program version

D hyd Hydrodynamic diameter

Cd Drag coefficient to be used together with D hyd

Ca Added mass coefficient to be used together with D hyd

Mass W-filled Mass of water filled riser for dynamic calculations

Gap Not used in this program version

SMYS Specified minimum yield strength of main riser pipe

Rated Load Rated load of riser connectors.

Static calculator The riser make-up user interface has a button, which gives access to the static calculator tool. The ability of the present make-up to fulfil the operational criteria can be checked by use of the static calculator tool. Flex joint angles and stroke can be calculated for different current profiles both in connected and free-hanging mode.

Click on the Static Calculator button and the Static Calculator control box will appear on the screen, see figure below. The screen is arranged with input data such as top tension, offset and mud weight at the top, current profiles in the middle and results in lower part of the screen.

The static calculator uses the riser model that has been entered in the make-up plan. Dependent on whether you are interested in the connected mode or one of the free hanging modes, additional input data has to be specified as follows:


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Mode Input parameter

Connected Free hanging

Riser contents density

Specified Specified

Top tension Specified Calculated

Offset to well head / lower riser end

Specified Calculated

Current profile Specified Specified

Three different current profiles can be pre-defined by the operator, i.e. A, B and C. Current velocity and direction (force direction) are specified at up to 10 elevations. Elevations are given as fraction of the specified water depth with 0% at bottom and 100% at the surface. The current profiles can be entered or changed by the operator by clicking the button Edit Current Profiles. The tables are then open for entering of values. The profile to be used for the analysis is selected by ticking it of in the circular box above the desired condition.

When all input data have been specified, the results will be shown in the table for the three configurations: Connected, Free Hanging with BOP and Free Hanging without BOP.


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Figure 12 Static Calculator view and control

Figure 13 Edit current profiles dialog box

Some of the results may have a slightly different interpretation for the different configurations as explained below.


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Connected

Result Meaning

Upper Riser Inclination Equal to flex joint angle with zero heel and trim

Lower Riser Inclination Equal to flex joint angle with zero stack inclination

Riser Stroke Estimated telescopic joint stroke including elastic elongation and sagging.

Offset N / E Echo of input only

Top Tension Echo of input only

Mud Density Echo of input only

Recommended Offset N/E Offset relative to well position

Differential Stroke N/A

Free Hanging

Result Meaning

Upper Riser Inclination Equal to flex joint angle with zero heel and trim

Lower Riser Inclination Inclination of BOP or LMRP

Riser Stroke Estimated telescopic joint stroke including elastic elongation and sagging. Assuming BOP/LMRP at the onset of connector disconnect

Offset N / E Calculated offset of lower end of BOP or LMRP relative to RKB

Top Tension Calculated submerged weight of riser with contents

Mud Density Echo of input only

Recommended Offset N/E N/A

Differential Stroke Estimated difference in stroke when going from the free hanging mode to the connected mode with its specified offset and tension. Positive differential stroke means stroke in on telescopic joint.


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Plotting of results The results from the static calculations can be presented and viewed in two different plots. First a plot similar to the PositionPlot view can be displayed where the vessel is shown at the entered offset together with the allowable areas defined by the circles and the recommended position.

Figure 14 Position plot view based on static calculator

Further, the resulting riser shape can be displayed as shown below. The shape plot is available both for connected and free hanging riser. The actual views are selected using the control box on the top of the display.


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Figure 15 Riser shape plot based on static calculator

Well constants Enter the well-specific (site-specific) data by clicking Well Constants on the Edit menu as follows:

Water depth (from MWL to wellhead datum)

Well/BOP orientation in the nautical co-ordinate system. This information is used to transform the measured BOP inclinations into the global co-ordinate system.

Further calibration and checks of the instrumentation systems are performed under entries on the Calibration menu, see section 9.


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Figure 16 Well constants dialog box

Horizontal X-mas tree When a horizontal X-mas tree is present, data for the tree can be entered in the well constants dialog box. These data are:

Height

Submerged weight

Maximum pressure capacity for the connector (structural)

Maximum effective tension capacity for the connector (structural)

Maximum bending moment capacity for the connector (structural)

Pressure limit (pressure rating)

Moment limit (max allowable bending moment)

NOTE Note that the maximum connector pressure and bending moment capacities given above represents the intersections with the zero effective tension line in the capacity envelope diagram. The maximum allowable pressure and bending moment capacities may be less when leakage criteria are governing and are defined as the Pressure and Moment limits.


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Operational limits The operational limits determine when alarms are triggered and affect the repositioning advice. The operator should carefully check and enter proper operational limits for the actual operations to be performed.

Click Operational Limits on the Edit menu. Enter the operational limits in the dialog box.

Operational limits can be entered for four different operational modes. Selection of operational limits for each mode should be in accordance with API RP 16Q or with company specific procedures and experience.

To view and edit the operational limits for a specific mode, select mode by toggling the radio buttons in the upper left corner of the dialog box.

Figure 17 Operational limits user interface

Operational limits are entered for the following parameters for each operational mode:


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Lower flex joint mean angle Yellow and Red alarm limits

Lower flex joint predicted extreme angle Yellow and Red alarm limits

Upper flex joint mean angle Yellow and Red alarm limits

Upper flex joint predicted extreme angle Yellow and Red alarm limits

Mud density Yellow and Red alarm limits

Riser pipe usage factor (UF)

Riser coupling rated load (this parameter is read from the joint definition file)

Utilisation ratio of riser components and connectors (UR) Yellow and Red

The operational limits apply to the mode that is selected in the mode display to the left. Changing modes in this display does not affect the operating mode selected for the operation in the Mode menu.

An explanation of the concept of usage factors (UF) and utilisation ratios (UR) is as follows.

The usage factors determine how much of the minimum yield strength that is allowed to be used according to the design code, e.g. API. Normally the usage factor is set equal to 0.67 for normal operation. Hence the allowable stress is (minimum yield strength) times the UF. The utilisation ratio determines how much of the allowable stress is being utilised. An UR of 1 indicates that the allowable stress is fully used and normally a red alarm should be triggered. To get a pre-warning a yellow alarm can be set to trig at an utilisation ratio of e.g. 0.8.

Due to the way the LMRP and Wellhead connector load capacities are defined, the usage factors may not be changed and is taken equal to 0.67.

Time To Go limits For the Time To Go functionality a separate set of limitations are defined for the lower and upper flex joint angles together with the telescopic joint stroke.

These limits shall reflect the maximum values that these parameters are allowed to reach during a drift-off or break of an anchor line fracture event in order to perform a safe emergency disconnect.


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Time needed for disconnect shall represent the actual time needed to perform an emergency disconnect procedure. This is the time needed from the EDS button is pressed until the connector unlatches and separates from the BOP. This limit should be carefully considered based on data for the actual BOP control system and mode of operation.

Note that there is only one set of Time To Go limits that can be defined. This set is used independent of the selected operational mode.

Manual Settings Click Manual Settings on the Edit menu to access the user interface for override data. Override data may be used when problems with non-valid data from sensors occur and when alternative information can be obtained from other sources or from back-up sensors.

Most of the parameters that are available as on-line sensor data can optionally be set as a static "override" value by the operator. If override is enabled, the program will use the user-defined value.

To enable override values press the green Sensor button and it changes to the orange Override button. Then press Apply or OK. To go back to sensor data, press the orange Overrride button followed by Apply or OK. When override is enabled for a parameter, all numeric displays of this parameter will have an orange background colour to indicate that the RMS uses manually entered data.


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Figure 18 Override and back-up sensor data dialog box

Back-up sensor data From the Manual Settings view the back-up sensors for the lower flex joint angle can be enabled by selecting the yellow or blue pod.

Mode of operation In order to provide useful results, the user must set the operational mode of the program equal to the operational mode of the riser. Click Mode on the menu bar to change the operating mode. Select one of the four options that are available in the dialog box that pop up:


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DRILLING

NON-DRILLING I

NON-DRILLING II

PREPARE FOR DISCONNECT

Figure 19 Operational mode

In Drilling Mode, the program calculates the position where the angles in both flex joints are such that utilisation of the permissible angle is equal in both ends, and such that the angles are as small as possible.

Non-Drilling Mode I and II are similar, except that other, user-defined limits (given in the Operational Limits dialog box) are applied. In these modes, the requirements to flex joint angles can be set to reflect the actual type of operation (i.e. running of casing, production tubing etc.)

The Prepare for Disconnect Mode is selected for optimising the rig position prior to disconnecting the riser from the wellhead. In this mode, the essential issue is to keep the lowermost riser joint vertical. This will minimise horizontal shear in the BOP stack. This is assumed the most favourable condition when the BOP or LMRP connector is to be released.

The non-drilling modes can be utilised for e.g. optimised deployment of long and rigid tools, e.g. a tubing hanger landing string. In such cases, it is essential to keep flex joints as straight as possible during passage of the tool. Thus, first the upper flex joint (UFJ) must be kept straight, then the lower flex joint (LFJ). The procedure is as follows:


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Before deploying e.g. the landing string, click Operational Limits on the Edit menu and set the UFJ yellow alarm to zero. The LFJ yellow alarm limit should typically set to 2-4 degrees.

Move the vessel to the recommended position

Run landing string through UFJ and down into the riser. Carefully watch the UFJ angle during this stage as the yellow alarm for the UFJ angle will lit continuously during this stage.

Click Operational Limits on the Edit menu and set the UFJ yellow alarm limit to typically 2-4 degrees, and set the LFJ yellow alarm limit to zero

Move the vessel to the new recommended position.

Run landing string through LFJ and down into the BOP. Carefully watch the LFJ angle during this stage as the yellow alarm for the LFJ angle will light continuously during this stage.

For retrieval, reverse the procedure.

Saving the set-up file

The set-up file contains the riser make-up plan, water depth and operational limit settings. The operator may want to save the current set-up data onto a file. This can be done by clicking Save Setup file on the File menu. When exiting RMS the user is prompted for saving the set-up file that is currently in use.


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6 CO-ORDINATE SYSTEMS AND UNITS This section described the co-ordinate systems and units used by the RMS system.


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Units The units of measurements of all input and output parameters are displayed together with the value. The main basis for selecting units has been the SI system but other units have been used where this is considered appropriate according to common practice.

Some conversion constants have been provided below for some commonly used units.

Conversion between [ppg] and specific weight [t/m3]:

To convert from [t/m3] to [ppg], multiply value by 8.3454.

To convert from [ppg] to [t/m3], multiply value by 0.11982.

E.g., seawater has specific weight 1.025 [t/m3], which corresponds to 1.025 * 8.3454 8.5540 ppg

Conversion of angles between [degrees] and [radians]:

To convert from [degrees] to [radians], multiply value by 0.017453.

To convert from [radians] to [degrees], multiply value by 57.2958.

Conversion of pressures between [kPa] and [bar]:

To convert from [kPa] to [bar], multiply value by 0.01.

To convert from [bar] to [kPa], multiply value by 100.0

Conversion of pressures between [kPa] and [ksi]:

To convert from [kPa] to [ksi], multiply value by 1.4503810-4.

To convert from [ksi] to [kPa], multiply value by 6894.76


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Co-ordinate systems The program requires continuous input of inclinations of the BOP, the lowermost riser joint (LRJ), the uppermost riser joint (telescopic joint), and the vessel itself. The orientations of the sensors at these four levels generally do not coincide. Therefore the inclinations are transformed from local sensor co-ordinates into a common global co-ordinate system.

The vessel heading is measured by the SDPM system and is input to the program. The vessel heading is measured clockwise from UTM Grid North.

The orientation of the BOP, the riser and the Telescopic Joint Inclinometer have to be entered as Well Constants to RMS to relate the inclinations given in local co-ordinate systems to the nautical co-ordinate system or relative to the vessel bow.

These orientations or reference headings are defined below:

Figure 20 Reference headings for riser components

Y B

BOP reference heading, relative yellow and blue pod

X

Y Telescopic joint inclinometer reference axis is the X axis.


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7 ADVISORY AND MONITORING FUNCTIONS This chapter describes the various advisories and monitoring functions of the RMS.


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Introduction The various monitoring functions have their own main view under the View menu. In addition, some of them have additional data views that can be selected from one of the two Subwindow menus on the View menu.

There is a subwindow that gives a summary of main data. Click MainData on one of the Subwindow menus and the following view is shown.

Figure 21 Main data view

In which:

UFJ Angle: Present mean upper flex joint angle

LFJ Angle: Present mean lower flex joint angle

TJ Stroke: Present mean telescopic joint stroke

Top tension: Present riser top tension

LFJ Tension: Present tension in lower flex joint

LMRP Connector Tension: Present tension in LMRP connector

Mud density: Present mud density

Time To Go: Estimate on worst case available time for a safe disconnect, in case of loss of station due to black out or anchor line breakage under prevailing conditions.


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More details may be found in the chapters explaining the various monitoring functions.

Optimum vessel position monitoring Click PosPlot on the View menu. The main display now shows an overhead view of the vessel. The actual vessel position is indicated by the small black circle representing the RKB. Safe areas for the LFJ and UFJ angles are defined by the circles and the recommended position in terms of new set point are shown with a green square.

There are generally two safe circles, and the RKB should be located inside both circles. The thick-line blue circle encompasses the RKB positions where the lower flex joint angle (or in Disconnect Mode: The lower riser joint inclination) will be acceptable.

Figure 22 Position plot view


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The thin-line blue circle encompasses the RKB positions where the upper flex joint angle will be acceptable. The circle diameters depend on the specified Yellow alarm angles for the selected operational mode. You may wish to toggle the modes to check the effect.

Select Repos Data from one of the Subwindow menus. The view displays the present off-set relative to the well, the vessel-repositioning vector (move vessel), i.e. the distance to move the vessel in easterly and northerly directions from the present position in order to reach the recommended position. In addition the recommended offset relative to the well is given.

Negative signs means west and south respectively.

Figure 23 Subwindow with ReposData view

To display the small-scale position plot view in one of the subwindows, click Mini Position Plot on one of the Subwindow menus.


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Figure 24 Mini Position PlotView

Riser top tension monitoring Click Top Tension on the View menu and the Top Tension view displays:

The instantaneous riser top tension (corrected for fleet angle)

The mean riser top tension (running average)

The Dynamic Tension Limit (DTL) according to API RP 16Q. (Upper Red limit)

90% of DTL, max. permissible utilisation, Ref. API RP 16Q (Upper Yellow limit)

Tmin, minimum safe top tension, with safety margins according to API RP 16Q (Lower Yellow limit)

Tsrmin, minimum top tension to prevent riser buckling, assuming no tensioner failure (Lower Red limit)


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Figure 25 Top Tension view.

In order to view the top tension time history for up to 12 hours, click the History Plot button.

Tensioner pull monitoring Click Tensioner Pull on the View menu. For each of the twelve tensioners, the Tensioner Pull view presents the current pull force, both in graphic and digital format.

Also, this view contains selector buttons for which tensioners that shall contribute to the top pull. By default, all twelve tensioners will contribute. However, in certain cases (e.g. tensioner overhaul) one may want to disregard the pull signal for a pair of tensioners. Thus, selector buttons have been included, by which any one pair of tensioners can be disabled by pushing the appropriate button.

The numbering of the twelve tensioners is shown below.


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Figure 26 Tensioner Pull view

In order to view the last 20 minutes time history of the tensioners click on the History Plots button.

Tensioner stroke monitoring Click Tensioner Stroke on the View menu to get to the tensioner stroke view. For each of the twelve tensioners, the Tensioner Stroke view presents the current tensioner stroke, both in graphic and digital format.

The view contains Enable/Disable buttons to include or exclude tensioners in the back-up estimate of upper flex joint angle based on the stroke measurements. Exclusion of tensioners may be useful when tensioners are not in use or if the stroke signal is corrupt. By default, all twelve tensioners will contribute.


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Figure 27 Tensioner Stroke view

The tensioner strokes are used to calculate the telescopic joint stroke. In order to provide reliable results for these parameters it is necessary to perform a calibration each time the length of a tensioner wire has been changed for some reason, i.e. re-termination or adjustments at the dead end or at the riser end. How to perform this calibration is explained in section 9.

Telescopic joint stroke monitoring Click TJ Stroke on the View menu. The telescopic joint stroke view contains:

Minimum possible telescopic joint stroke, corresponding to first tensioner stroke-out (lower blue dotted line)

Maximum possible telescopic joint stroke, corresponding to first tensioner stroke-in (upper blue dotted line)

Instantaneous telescopic joint stroke value

Mean telescopic joint stroke (running average)


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The telescopic joint stroke is derived from the tensioner strokes. In case of unrealistic stroke values you should examine the tensioner strokes and if necessary perform a re-calibration of the tensioner strokes. See previous section.

Figure 28 Telescopic Joint stroke view

The yellow alarm will be initiated when the mean stroke value plus or minus 3 times the present standard deviation exceeds the upper or lower stroke limits respectively. The red alarm will be initiated when the mean stroke value plus or minus 2 times the present standard deviation exceeds the upper or lower stroke limits respectively. In this way the yellow/red lines reflect the statistical variation in the measured stroke due to the actual environmental conditions (heave). This approach is aiming to provide a consistent safety level in all environmental conditions.

This variable stroke margin feature may be explained as follows: In the case of a very calm sea, and little rig heave, the program will allow the tensioners to stroke almost to the collapsed or fully extended state, before Yellow or Red alarms are triggered. This is because statistical analysis of the stroke shows that very low stroke margins are required to keep the probability of full stroke-out/stroke-in at a reasonably low level.


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However, in high seas with a lot of rig heave and a lot of dynamic stroke, the dynamic stroke range will grow proportionally to the standard deviation of the stroke. In very high seas, the dynamic stroke ranges may grow until it becomes impossible to keep the high/low stroke indicators inside the permissible range. In such cases, disconnect should be considered.

To view stroke time histories of up to the 12 last hours, click the History Plots button.

It is also possible to view the telescopic joint stroke in one of the subwindows. Click TJ Stroke on one of the Subwindow menus and the view containing the instantaneous stroke together with the averaged stroke together with the stroke limits will be displayed as shown below.

Figure 29 Subwindow view of telescopic joint stroke, mean and instantaneous

Flex joint angles monitoring Click Flex Joint Angles on the View menu and the averaged upper and lower flex joint angles are displayed in a polar plot view. Also, the user defined Yellow and Red alarm limits are plotted as yellow and red circles. Flex joint bearing is defined as the bearing of the top object minus the bearing of the lower object, i.e. UFJ angle bearing is Rig bearing - Slip joint bearing and LFJ angle bearing LRJ bearing - BOP bearing.


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Figure 30 Flex joint Angles view.

Time histories of the last 20 minutes for the instantaneous angles and mean angles are shown in the lower part of the view.

To view time history plots of the mean flex joint angles for up to the 12 last hours, click the History Plots button.

In connection with flex joint angle monitoring it may be of interest to the operator to view the inclinations of the BOP stack, the lower riser joint (LRJ), telescopic joint (TJ) and the vessel. In order to do so, click Inclinations on one of the Subwindow menus. The operator can select to view the inclinations in the global co-ordinate system, the vessel system or the BOPs system of axes, see section 6.


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Figure 31 Inclination view

Riser loads monitoring Click Riser Loads on the View menu to display the effective tension diagram for the whole riser length and the bending moment diagrams for the lower and upper part of the riser. The bending moment diagrams for the riser is based on the moment introduced in the flex joints due to their rotational stiffness and how the moment decays based on the actual tension/stiffness ratio.

Riser pipe stresses and riser coupling loads are calculated and checked for the following cross sections that are considered to be the most critical:

Telescopic joint outer barrel joint (pipe and coupling)

Uppermost bare joint (pipe and coupling)

Lowermost riser joint (pipe and coupling)

The R-buttons in the display is for easy re-scaling of the axes.


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Figure 32 Riser loads display

The cross sectional loads and utilisation ratios are displayed in two subwindow displays. Click Riser Loads on one of the Subwindow menus to view the response and utilisation ratios for the three selected riser joints and couplings. Note that bending moment information is only available for the telescopic joint.

Note that the loads represent only the mean static loading and that dynamic response due to waves or vortex shedding is not included. This is because the dynamic response amplitudes are not known or measured along the riser.

The utilisation ratio shall be in the range of 0.0 1.0 and equal to 1.0 when fully utilised. The utilisation ratio is linked to the usage factors that are entered under Operational Limits as shown below.

UR=eq/(y*UF)

Where:

UR : Utilisation ratio (0.0 1.0)

UF : Usage factor ( e.g. 0.67)

eq : Equivalent stress based on measured response

y : Yield strength of material


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Figure 33 Mean Riser loads and utilisation for selected joints

Connector loads monitoring Connector loads is viewed by clicking Connector Loads on the View menu. The view shows the capacity envelopes of the LMRP connector, the BOP connector and the X-mas tree connector if present in the riser make-up. The capacity envelopes reflect the actual tension in the connectors and the actual bending moment and pressure combination is presented as an asterisk in the envelope. The numeric values are displayed to the right of the diagrams.

As long as the asterisk is located to the lower left of all limiting solid lines in the diagram, the utilisation of the connector is acceptable.

Note that the connector loads only represent the mean static loads and that dynamic response due to waves or vortex shedding is not included.

The red lines indicate the red alarm limit and the black dashed lines indicate the yellow limit. The yellow and red alarm limits can be changed by the operator in the Operational Limits menu.

The capacity envelopes are described by the data entered under Operational Limits.


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Figure 34 Connector capacity envelope and actual loading (X).

Time To Go monitoring When operating in DP mode the Time to Go function predicts the available time for the operator to initiate disconnect in case of drift off caused by a blackout or a worst single failure event. The DP system identifies the worst single failure that causes the most severe drift-off/loss of station scenario. The DPs Motion Prediction module performs an estimate of the resulting drift-off path history for the vessel. This vessel drift-off path is transferred to RMS where the riser response history during the drift-off scenario is calculated.


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When operating in PM mode the Time to Go function predicts the available time for the operator to initiate disconnect in case of loss off station caused by a break in an anchor line. The PM Online Consequence Analysis checks the moored vessels ability to maintain its position after a single line break The vessel transient motion path caused by a line break is transferred to RMS where the riser response history during the transient motion is calculated. If one of the preset Time to Go limits for stroke or riser angles will be violated for a line break incident, the Time to Go function gives an estimate on how many seconds the operator has to initiate an emergency disconnect in case the actual line really broke.

The limiting response values for flex joint angles and stroke in case of a drift-off event are defined in the Operational Limits view under the Edit menu. Here also the time necessary to perform the disconnect procedure is given.

The time to go estimate is given in number of seconds until one of the critical response values has reached their critical value less the number of seconds to perform the emergency disconnect sequence. The time necessary to perform the emergency disconnect sequence is entered under the Operational limit menu as the time from when the EDS button is pressed until the connector unlatches and separates form the BOP.

The analysis is repeated automatically every 3 5 minutes and the present worst case Time to Go estimate is presented in the Main Data view in one of the Subwindows.

In order to view the details of the time to go analysis, click Time To Go on the View menu.

This view contains graphic presentation of the worst case time to go estimates calculated the last hour. Tabulated detailed results of the most recent worst case Time to Go estimates are presented together with the time of calculation, case identifier, Time to Go value and which limit that was exceeded. The case identifier is generated by the SDPM system and transferred to the RMS. The view gives an echo of the response limits that are currently in force.

Further details for the last four Time to Go calculations can be examined in three additional views, accessed through the buttons Limits, Shape and Path.


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Figure 35 Time To Go. Note that the case identifier is given by the

SDPM system and the text in the plots above are for illustration purpose only.

The Time To Go Limits view display riser responses such as stroke and flex joint angles. From the dialog box you can select which failure mode you want to examine. In the lower left of the view actual limits in terms of angles, stroke and time for the disconnect procedure are summarised. Based on the actual top tension, the critical lower flex-joint angle with respect to bending moments in the LMRP and BOP connectors are automatically calculated.


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Figure 36 Time To Go: Riser Limits. Note that the case identifier is given

by the SDPM system and the text in the plots above are for illustration purpose only.

The Time To Go Shape and Time To Go Path views display the estimated riser shape histories and vessel drift-off trajectories respectively.


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Figure 37 Time To Go: Riser Shape. Note that the case identifier is given

by the SDPM system and the text in the plots above are for illustration purpose only.

Figure 38 Time To Go: Rig drift-off trajectory Note that the case

identifier is given by the SDPM system and the text in the plots above are for illustration purpose only.


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The time to go analysis ignores vessel and riser motions due to waves. In order to compensate for this, the Dynamic factor defined in the Execution control view under the Calibration menu is used. In a conservative manner the significant dynamic amplitude is added to the response. The significant dynamic amplitude is taken as the currently measured standard deviation for the actual response process multiplied by the dynamic factor.


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8 HISTORICAL DATABASE The RMS stores a large number of data during operation. These data can be inspected during and after a operation period. This Section describes how data from the current and previous operations can be accessed, viewed or exported.


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Introduction The data from the current operation are stored in a database under the directory C:\RMS\DATA. When RMS is started the operator is asked whether he will continue storing data to the existing database or whether he will start a new database and store or delete the old one.

If the operator selects Continue, the new data will be appended to the existing database. If the operator selects New, he is prompted to save the old RMS database or not.

If the operator answerYes he should give it a name indicating the well or block name. The old database will then be moved to the directory C:\RMS\saved with the name given by the operator. A new database will be started under the C\RMS\DATA directory.


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It is recommended that RMS be restarted when RMS has been set-up properly for a new well and after all set-up files and calibration files have been stored properly. At start-up the operator should then start storing data to a new database and store or delete the old one.

After a well operation has been finished and the riser is being retrieved the RMS should be exited and the DATA directory renamed to e.g. the name of the well or block.

Viewing Historical Data RMS must run both to view data stored in an old database or the data currently stored in the database. To view old data, the stored database (all files) has to be copied from its location under the C:\RMS\saved directory to the C:\RMS\DATA directory. This means that it is only recommended to view an old database when the RMS is not used for monitoring during a riser operation. When starting the RMS to view an old database, select Continue when prompted for Continue or New at start-up of RMS. The RMS will then actually append new data to this database, but these data will be of no interest in this case.

The Historical Trend Viewer (HTV) is launched from the Calibrate menu. The user level must be Super User to get access to the Calibrate menu.

When HTV is opened from the Calibrate menu the Select Tags for HTV dialog box appears, Figure 1. If the HTV is already open, select File>Select Tags to display the dialog box.

The complete tag list is enclosed in Appendix I The database contains both raw data and calibrated/and transformed data. Normally, the most interesting data in the RMS database will be the tags with Inn or Out in their names.


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Select the tags you want to display in the Available Tags list box and click the Add button to display them in the Tags to Display list box on the right. HTV can display up to eight tags at a time.

View configuration information about a tag by selecting it in the Tags to Display list box and clicking the Tag Information button.

Click the OK button when finished and the Historical Trend Viewer display is launched, see Figure 40. If the display disappears, click the Historical Trend Viewer on the Windows task bar to get the view on top of the RMS main view.

Figure 39 The Select Tags for HTV dialog box


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10

2 1

3

8 6 4

5 7

9

11

12

13

Figure 40 Historical Trend Viewer

The functions of the HTV is illustrated in Figure 40 where:

1. Stop time

2. Start time

3. Y-axis displays

4. Full scale button

5. Auto scale Y button

6. Scrolling tool

7. Zoom button

8. Cursor Movement tool

9. Trend display

10. Plot legend

11. Panning buttons

12. Time axis

13. Cursor display

The panning button functions are described in Error! Reference source not found.


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Table 1 Panning button functions

Button Name Description

|< Retrieve oldest data

Displays first available page of data

Forward one-half page

Moves the display forward by half of the current time span.

>> Forward to closest point

Centres the display around the closest point to the right of the time span. If there is no data in the next time span, it skips to the start of data.

>| Most recent data Displays the most recent available page of data.

Changing the HTV Time Axis and Time span You can select and enter the time and date on the x-axis of the historical trend on the HTV directly. However, the HTV responds immediately to any change you make. If you want to make manual edits to both the start and stop time on the time axis, you can select the Viewer>Time & Date option. When you select this option, the following dialog box appears and you can enter the start and stop time of the data displayed in the trend.


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The Time span pull-down menu displays the amount of relative time between the start and end points of the time axis. To change the amount if time between these points, you either can manually re-enter data in the start or end point on the time axis, or use the Time span pull-down menu.

By default, the Time span contains the values 1:00, 5:00, 10:00, and 30:00 (minutes). Select Enter New in Time span if you want to enter a different amount of data to display.

Viewing an HTV Tag Value at a Specific Point in Time The Data Display table on the HTV shows the tags displayed in the trend, the tag description, and, for analog tags, the engineering units associated with the tag. The two rightmost columns show the values of the tags ate the two cursor locations in the trend. For discrete tags, the values in these columns are either On or Off. To move cursors, drag the triangles at the bottom of the trend display.

Exporting HTV Data to a Spread Sheet From the HTV, select File>Export. The HTV exports the information currently displayed in the trend to a tab-delimited file. A dialog box prompts you for the name and location for the file to create.

The HTV resamples data in periodic intervals so that all tags have the same number of data points. The frequency defaults to a value according to the frequency of the data in the historical files. If you want to override this value, enter the frequency you want in the dialog box.


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9 CALIBRATION FACILITIES The Calibrate menu is only available to the highest user level and should normally remain unchanged after the system has been commissioned.


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Execution control In this control view parameters that affects calculation of mean and extreme values are defined.

Click Execution control on the Calibration menu to enter this control dialog box.

Figure 41 Execution Control

The Execution parameters consist of the following:

Averaging period for mean upper and lower flex joint angles is the time span in seconds over which the moving average of the flex-joint angles is calculated.

Averaging period for mean stroke is the time span in seconds over which the moving average of the stroke is calculated

Dynamic factor influences the estimation of extreme values and is used for flex-joint angles estimated extremes and to account for dynamic amplitudes in the Time To Go estimates. Should be set in the range 2 4. A high value is conservative.


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Inspection of data received by the RMS Click DataIn on the Calibrate menu to view the flow of sensor data from the SDPM and SVC systems to the RMS-OS. The view contains a complete dump of all raw data provided by:

Kongsberg Simrad DP,

Tensioner Control system,

BOP Control system,

The view is mainly intended to check received data against data submitted by the different systems in order to make sure that the interfaces are working properly.

Inspection of data transmitted by the RMS Click DataOut on the Calibrate menu to view the flow of data from the RMS to the SDPM system.

The view is mainly intended to check the data received by the SDPM against data submitted by the RMS in order to make sure that the interfaces are

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POM_C Kongsberg Simrad Seaflex