2DSeismic

NaviPac 2D Seismic Author : Ole Kristensen Company: EIVA a/s Date: 15-3-2007

NaviPac 2D Seismic Page 2

File: C:\EIVA\NAVIPAC\MANUALS\NEW\APPENDIX\2DSEISMIC.DOC Page 2 of 22

Created by Ole Kristensen Created on 15-3-2007

Introduction This document illustrates the features utilized by NaviPac when it comes to 2D seismic surveys – which go from streamer positioning, shot control, UKOOA data recording and data editing

Contents NaviPac 2D Seismic ..................................................................................................................1 Revision table.............................................................................................................................2 1 Working scenario ...............................................................................................................2 2 NaviPac online handling ....................................................................................................5

2.1 Streamer positioning ..................................................................................................6 2.2 Tail-buoy and gun positioning ...................................................................................9 2.3 Distance shooting.....................................................................................................10 2.4 Shot control..............................................................................................................11 2.5 Recording.................................................................................................................12 2.6 UKOOA P2/94.........................................................................................................13 2.7 EOL report ...............................................................................................................14

3 NaviEdit data cleaning.....................................................................................................15 3.1 Header editing..........................................................................................................16 3.2 Sensor editing...........................................................................................................17 3.3 Streamer data ...........................................................................................................18 3.4 Receiver groups .......................................................................................................19 3.5 UKOOA P1/90.........................................................................................................20

4 EIVA Software solution...................................................................................................22

Revision table Date Who Comment 14-9-2006 OKR Document created based on a.o. show from OI2006 and

information from client documentation. 15-9-2006 JBL Checked – no comments 15-9-2006 JUS OK 15-9-2006 OKR Added small conclusion section – version 1.0

completed

1 Working scenario The EIVA software is used on several vessels for 2D seismic, and the reference list covers among other

• GeoSeas/Pacific Exploration: Odin Explorer See http://www.petra.com.my/pdf/Odin.pdf#search=%22odin%20explorer%22

http://www.petra.com.my/pdf/Odin.pdf#search=%22odin%20explorer%22




• NCS Subsea: US 15 Licenses used mainly for seismic operations See http://www.ncs-subsea.com/PDFs/2DSeismicNavigationSystemBrochure.pdf

• Geological Survey of Sweden (SGU): Ocean Surveyor See http://www.sgu.se/sgu/en/index.html

• University Of Bergen – Håkon Mosby • Norwegian Institute of Marine Research: G.O. Sars

See http://www.imr.no/ • University Of Aarhus • Geoscience Australia • Dokuz Eylul University • Marine Exploration Partners AS • Unidad De Technologia • Upstream Petroleum

Common to these scenarios is that they perform seismic shooting, streamer and source positioning and data reporting using the EIVA NaviPac and NaviEdit generic software modules:

This document describes a real scenario based on the installation onboard Odin Explorer:

NaviPac Navigation & Data

Acquisition Planning & Acquisition

NaviEdit Editing & Reporting

Data Editing & Exporting

http://www.ncs-subsea.com/PDFs/2DSeismicNavigationSystemBrochure.pdf

http://www.sgu.se/sgu/en/index.html

http://www.imr.no/




The vessel is equipped with

• Multiple GPS receivers for vessel positioning • Gyro and motion sensor for 3D offset compensation • Digicourse dynamic streamer positioning • Remote GPS for Tailbuoy and gun positioning • Deep sea echosounder • Air gun control • Syntrak 960 seismic recording system • Syntron source control system

Schematic overview:

Rough data flow:

Centre of near group

Centre of source

Centre of stern

Navigation reference

point

Last active group

Channel 360 Channel 1

Tailbuoy

4500m 25.7m 69.3m 50.0m 50.0m Approx 117m

20m

100.0m

20m

20m

CMP




We will in the following section describe how this is handled in the EIVA software suite.

2 NaviPac online handling The role of NaviPac onboard a seismic vessel do not differ much from any other survey operation – NaviPac utilizes fives major roles

• Planning • Navigation • Integration • QC and Control • Recording

At first level the operator or administrator uses the Helmsman’s Display to generate survey plans – either by drawing them by mouse, entering fix coordinates or importing external definition files. NaviPac supports various line types including great circles. The planning module can be performed on any computer running Windows as this part of the software is license free. The first key to success is to get a reliable vessel positioning system. To do this NaviPac utilizes multi LOP input, advanced Kalman filter technique for blunder rejection and full 3D compensation and ends up with the best suited result (weighted least square algorithm) for the vessel reference position. After that the system can calculate good results for streamer position, Gun, FRG, COS, CMP etc. as discussed in later sections.




A very important role onboard is system integration, where NaviPac reads all sensors onboard, timetag them in uniform reference and distribute the data to any other system onboard that might need it (autopilot, seismic recording, remote vessel control, ..). The data output library consists of more than 75 various drivers – and if that’s not sufficient then we offer a fully generic solution where the operator defines exactly his own layout. The system integration includes also inter vessel communication so you may receive and deliver information in multi vessel operations. The major role in any survey operation is quality- and survey control – here we see the Helmsman’s Display, shooting control and various time series windows as a major role player. This is discussed further in section 2.3 and 2.4. Finally – no survey without any data! The NaviPac LogData module records the data in standard and generic formats, as the system optimizes it for the exact needs to guarantee that everything needed is there at the end of the day. This is discussed further in section 2.5 and 2.6.

2.1 Streamer positioning In the most advanced setup the streamer is equipped with compasses and depth sensors (birds). NaviPac supports interfacing of the standard Digicourse streamer positioning system. NaviPac accepts both binary and ASCII format with up to 32 birds







The operator may configure each bird individually, define FRG and CMP. During the survey the system calculates the streamer shape by combination of vessel CRP, tow point, vessel heading and compass data. The result is displayed on the Helmsman’s Display, and on special bird control window (ASCII and graphical data presentation)




Having performed streamer position NaviPac utilizes also feather angle monitoring – that is continuous comparison of streamer angle towards the current line bearing. The result can be view in ASCII, as graphs and recorded like any other data sources.

2.2 Tail-buoy and gun positioning Beside the streamer NaviPac also allows definition and positioning of various other objects (offsets) on the streamer:

• Tail-buoy: The simplest solution is naturally obtained via the end of the streamer – but this is normally not that accurate. Alternatively you may put a remote GPS (dGPS) on the buoy – and get the interfaced, displayed and recorded. Online comparison of streamer and GPS based data (continuous range/bearing tracking) gives furthermore excellent QC information

• GUN: The position of the gun(s) is not critical to NaviPac handling – but might be to the seismic recording system. The position can be obtained in NaviPac as manual layback, range measurements or dGPS receivers.




• COS: The centre of source (COS) is defined as either the gun position or some defined reference between the guns. It can be obtained directly like the gun position or as a combined position with local coordinate system as reference.

• FRG: The first receiver group (FRG) is defined as part of the Digicourse setup, as it’s defined as a distance from the tow point. NaviPac uses average of the user defined number of compasses performs a range/bearing calculation along this line. In certain scenarios you might observer that this point isn’t located on the streamer.

• CMP: The common midpoint (CMP) is defined as part of the Digicourse setup, as it’s defined as the point between the FRG and the COS

All the above objects exist as standard components in NaviPac – the position can be displayed, recorded and distributed to external systems if required.

2.3 Distance shooting The most important issue in the seismic operation is the distance shooting. In NaviPac this is defined as kilometer points (kp) along the line. The operator defines the interval along the line (for example 12.5 meters) – where to start and stop, how to map kp to event numbers, number of run-ins, and most important which object (vessel reference, COS, ...) must control the shooting. It must be considered very carefully which object to use, as the accuracy of the shooting depends highly on the quality of the controlling position! When a survey line active NaviPac calculates the position of the controlling object at each cycle. Based on the selected runline it calculates the current kp and the kp speed (how fast does the vessel move along the line (SAL)) – this is not necessarily the same as SMG – but hopefully close! Based on the current SAL and kp the system calculates when the next shoot are expected. If that value is small compared to the cycle time (1 second as default) then it defines a system interrupt on the expected time – if it’s still far away it will just wait-and-see. The Windows interrupt will then occur when NaviPac expects the vessel to be at the point – based on load of computer this can be obtained with 1-2 ms accuracy. NaviPac will generate a trigger to the shoot control and register the exact time. At next ordinary cycle (when we have received data from all sensors) NaviPac continue the event calculation and figure out exact where the vessel was at the time. This information will then be recorded and delivered to external systems like seismic recording system.




During the shooting process the operator may get graphical display of shoot points, information about shoot accuracy (observed vs. expected distance) and access small event log report.

2.4 Shot control NaviPac can be configured to output a trigger exactly when the system expects to be at the wanted position. Due to the nature of Windows computes this is generated as a single character output on a serial port.




Most systems require a more hardware related contact closure output instead. This may be handled via the EIVA TriggerBox.

The box can be configured with up to 4 individual outputs with individual forms. Details may be found in special EIVA document.

2.5 Recording NaviPac supplies a dedicated survey recording system LogData which based on input from NaviPac records data in various data formats

• General Format: Includes raw data messages and interpreted data. Most often used for debugging and advanced documentation.




• Survey Format: Generic survey recording special designed for processing in NaviEdit. Recommended for 2D seismic!

• Custom Format: Full flexible recording where operator may design exact recording layout.

• Event logging: Special event recording in simple ASCII file. Primarily for simple operations

• ASCII outputs: All NaviPac outputs may be routed to disk and thus act as recording system.

Data recording for 2D seismic will normally consist of survey format defined with all cycles (to allow inter event information in the UKOOA export)

2.6 UKOOA P2/94 NaviPac includes an exporter from the survey data to raw P2/94 format as required by most clients. Based on current setup the system generates a UKOOA header definition and guides the operator through the definition of all items:




The survey files may then be converted right after EOL and handed over to the clients QA for further inspection. It is the plan to expand this to be an automated process right after EOL has been reached.

2.7 EOL report NaviPac includes an automated end-of-line reports which generates statistics on most incoming data. The data is available in zipped ASCII format and reports may be generated in various forms:




3 NaviEdit data cleaning The processing step in the EIVA suite is covered by the NaviEdit product. First of all the system reads all survey data into a SQL database and utilizes full data management via the JobPlanner.




Each component can be controlled individual (or in combination) as each block is identified by runline-name and object name as illustrated above. The use of SQL database gives the end user an excellent way to manage huge datasets, and they may easily extract data on their own by the usage of SQL scripts. EIVA a/s will at any time deliver table definition layout if required. The major idea in NaviEdit is to allow the operator to get rid of all error sources – both man-made and instrument noise.

3.1 Header editing The most common error is man-made due to entering wrong offsets, selecting wrong geodesy etc. NaviEdit includes a general header editor where the operator may control and change all this in one go:




3.2 Sensor editing The first level of data editing will be based on sensor data editing, where operator via advanced filters, de-spiking, smoothing and the human eyes validates and cleans data is required.




3.3 Streamer data The same editing techniques may be used on the streamer data.




Compass and depth may be validated and edited for each bird. At the end this results in a new streamer position being calculated. As a special QA option the operator may redo the comparison between streamer and GPS based tail buoy calculation.

3.4 Receiver groups Before exporting data to the seimic processing system the operator may define (and redefine) the streamer layout. InNaviEdit this goes both for

• Birds • Receiver groups




3.5 UKOOA P1/90 The final stage in the NaviEdit data handling is exporting the processed result in the standard UKOOA P1/90 format.







4 EIVA Software solution The NaviPac & NaviEdit solution for 2D seismic operation has been developed in close contact with our clients – especially thanks to the crew on Odin Explorer and the NCS Subsea experts who has helped us a lot. This has resulted in a very robust and well functioning solution, which operates day after day all around the world. EIVA a/s continues to evolve the solution – and any comments or feedback you may provide is highly appreciated – your information helps us improve the system.

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2DSeismic