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TAMU - PemexOffshore Drilling

Lesson 4Blowout Preventers

and Their Control

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Lesson 4 - Blowout Preventers and Their Control

The BOP Stack Hydraulic Connectors Kill and Choke Valves BOP Controls

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Blowout Preventers and Their Control

Control Pods & Shuttle Valves Redundancy Accumulator Capacity

Requirements Backup for BOP Controls

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Major Changes in BOP Equipment for Subsea Use:

1. The size of the BOPs is increased.

2. External hydrostatic pressure at the ocean floor must be considered.

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Major Changes in BOP Equipment for Subsea Use:

3. Hydraulics have become more important in reaction times, because the longer flow lines increase thepressure drop,

while the larger BOPs require more fluid to operate than their land counterparts.

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Major Changes in BOP Equipment for Subsea Use:

4. To avoid the pressure drop in the return lines, the hydraulic fluid is vented to the sea. This requires a fluid that is non-polluting as well as non-corrosive, yet has low viscosity, and is a good lubricant,

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Major Changes in BOP Equipment for Subsea Use:

4 (cont’d.) and can mix with water of high mineral content.

5. The philosophy of stack arrangement, especially the location of the kill and choke lines has been changed.

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Major Changes in BOP Equipment for Subsea Use:

6. Pressure drop in the long choke line influences well control procedures.

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CHOKE AND KILL LINES

MARINE RISER CONNECTOR

INTEGRAL MARINE RISER JOINTS

TELESCOPIC JOINT

CONNECTOR

BOP STACK UNITIZATION GUIDE FRAME SYSTEMS

FLEX JOINTS

TEMPORARY GUIDE BASE

CONNECTOR

WELLHEAD HOUSING

GUIDE STRUCTURE

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A Subsea Blowout

Preventer Stack

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Subsea Blowout

PreventerEquipment

Failsafe Valve

Figure 11-1

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Figure 5-1. Cameron U-type ram blowout preventer.

High pressure, close around pipe, usually for one size pipe only, hang pipe - 600k

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Annular Blowout Preventer.

STEEL FINGERS

CLOSING PORT

OPENING PORT

RUBBER SEAL

ANNULAR PISTON

Close around pipe of any size, open hole. Used for stripping and snubbing, often 2 EA

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Annular Blowout Preventers in Operation

Illustrations and Diagrams

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Annular: Element Partly Closed

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Annular: Stripping Out

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Annular: Stripping In

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Complete Shutoff

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Annular Preventer Closing Pressure, psig

Wel

lbo

re P

ress

ure

, p

sig Shaffer

spherical BOP with 5” D.P.

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The GL Hydril

Blowout Preventer

Figure 5-7

Piston

The preferred Hydril for subsea. Hydrostatic due to mud -> open. Compensate

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Secondary Chamber to RiserThe mud may plug off the opening...

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Secondary Chamber to Open Chamber

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Secondary Chamber to Close Chamber

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Shear Rams

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Mandril Type

Hydraulic Connector

Dog

Cam

Piston

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Collet Type Hydraulic Connector

Collet Finger

Cam

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Fail-Safe Kill and Choke Valve

* Spring loaded

* Hydraulic pressure

* Two in series

* Same WP as BOPs

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Configurations of kill/choke

line outlets for conventional

four-ram stack

Figure 5-12Examples

Wellhead Connector

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Schematic of a

hydraulic control system.

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Hydraulic Subsea BOP

Control System

Hose Bundle

Pod (2 EA)

Accumulators

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Typical hose bundle for hydraulic system.

5/16” Pilot Lines

1/4” Pilot Lines

Figure 5-15

Power Fluid Line 1”+

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Typical

1. Hydraulic Hose

2. Multiple-Conductor Electric Cable

(faster - better for deep-water wells)

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Electro-Hydraulic Hose Bundle - cont’d

3. Protective Inner Cover 4. Strength Member5. Outer Protective Jacket (Optional)

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Pilot Line Attachment

Power Fluid

To Function

Pilot Valve- Poppet Type Vent

Opening

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BOP Control

Pod

* Pilot valves* Pressure regs.* Retrievable* Two for Redundancy

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Accumulator

- BladderType.

BLADDER

TAPERED VALVE

GAS CHARGE PORT

INLET/OUTLET

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Fig. 5-19 Shuttle valve

POWER FLUID TO FUNCTION

POWER FLUID FROM POD

SEAL

Directs power fluid to function. Isolates inactive pod. Lines from valve to pod not redund.

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Redundancy between pods on a stack.

Shuttle valve

Pilot valves

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Flow Paths to close rams from driller’s panel.

Fig. 5-22

Driller’s Handle; Air signal to Hydraulic unit; pressurize pilot line; pilot valve at pod, power fluid -->

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Flow paths to open rams from the driller’s panel.

Fig. 5-23

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44

1,465

0.577

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Example: 1,000 ft of water

Precharge pressure is 1,000 psi above ambient

Pc = 15 + 1,000 + 0.45 * water depth = 1,465 psia

P = 15 + 3,000 + 0.45 * water depth = 3,465 psia

577.0P

P1.F.V C

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Friction Losses

Pressure losses caused by friction in the plumbing is a major source of decreased reaction times.

Fluid flow is difficult to define and various books have been

written on the subject.

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Fanning or Darcy Equation

A simple approach can be taken by considering the friction losses as described by the Fanning or Darcy equation that may be expressed as:

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2

D

q L fKF

50 gal in 30 sec => 100 gal/min 10 gal in 8 sec => 75 gal/min

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Where:

conversionunit for constant Kdiameter lineDrate flowq

length lineLline in the lossfriction F

Re offunction factor,friction f

5

2

D

q L fKF

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And Where:

Dv

number sReynold'Re

D = line diameterV = fluid velocity = fluid density = fluid viscosity

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Figure 5-25. BOP Stack SchematicConnected by clamps. Stresses from Tension, bending and pressure. Frequent stack testing.

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Figure 5-26. Pressure

Differentials Acting on Preventer.

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See text

Example Calculations

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Tension at the ball joint, kips

All

ow

able

Op

erat

ing

Pr e

ssu

re,

psi

g

For a fixed ball joint angle, the maximum tension at the ball joint decreases as press. incr.

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Surface Unit- Acoustic backup for BOP control

Figure5-295-29

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Example from the GOM

3,200 ft

300 ft of 36”csg, jet -in

2,300 ft of 20”csg, run in 24” hole

WL

ML

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3,200 ft300 ft of 36”csg, jet -in

WL

ML

Jetting-in the 36” Conductor

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Drilling a 24” Hole

3,200 ft300 ft of 36”csg

WL

ML

24” Hole

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Running the 20”Casing

3,200 ft

2,300 ft of 20” csg.

WL

ML

24” Hole

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Cementing the 20”Casing

3,200 ft

Drillpipe

WL

ML

24” Hole