Well Control for drilling engineers

7/27/2019 Well Control for drilling engineers

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WELL CONTROL

1



Introduction to Drilling Well Control

Describe primary and secondary well control

Explain the mechanism of a kick List causes of kicks

Explain shut-in procedure

Explain the two well control methods commonly used

Describe the working of annular and ram preventers

Describe the layout of the choke manifold and control panel

Explain the function of the closing unit

Identify mud/gas separator

Learning Objectives

2




Primary Control

Vertical depth = 10,000’

Mud weight10 ppg

Hydrostatic pressure on bottom of hole10 x 0.052 x 10,000 = 5,200 psi

Overbalance = 5,200 – 5,000 = 200 psi

Formation pressure = 5,000 psi

Hydrostatic pressure

of the mud column

prevents flow of

formation fluid into

the wellbore if it is

equal to or greater

than the formation

pressure

3




A kick is an influx of

formation fluid into

the wellbore whenthe formation

pressure exceeds

the hydrostatic

pressure of the mud

column. The

intruding fluid could

be liquid or gas.

Formation pressure = 5,500 psi

Influx enters wellbore(Kick is taken)

Hydrostatic pressure on bottom of hole10 x 0.052 x 10,000 = 5,200 psi

Overbalance = 5,200 – 5,500 = -300 psi

Well is shut-in to prevent a blow out

Drill string is still full of 10.0 ppg mudDrill pipe pressure represents magnitudeof underbalance.Mud weight required to just balance the

formation pressure:

Old MW + 300/(10,000 x 0.052) = 10.0 + 0.6

Vertical depth = 10,000’

A Kick

300 psi 500 psiShut-in drillpipe pressure

Shut-in casing pressureHigher than SIDPP due toinflux in part of the annulus

4




Calculation of Kill Mud Weight

)(0.052)(TD

SIDPPOMWKMW

TVD +=

325

0.052 x 8,000 = 12.28, say 12.3 ppg

Add trip margin of 0.5 ppg

New Mud Weight for drilling = 12.3 + 0.5 = 12.8 ppg

)(0.052)(TD

SIDPPOMWKMW

TVD +=

Example:

True Vertical Depth (TD)= 8,000 feetOld Mud Weight (OMW) = 11.5 ppg

Shut In Drill Pipe Pressure (SIDPP) = 325 psi

Kill Mud Weight (MW) = 11.5 +

5




Causes of Kicks

Failure to keep the hole full while tripping out

Unexpected formation pressure

Low density fluid

Lost circulation

Swabbing

Mechanical failure

Human error

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http://slidepdf.com/reader/full/well-control-for-drilling-engineers 7/26Introduction to Drilling Well Control

Shut-In Procedure

Kick detected while drilling Space out

Stop pumps

Close uppermost applicable BOP

Record SIDPP, SICP, pit gain, time

Kick detected while tripping

Stab full opening safety valve, close same

Space out

Close uppermost applicable BOP

Record SICP, pit gain, time

Prepare to strip to bottom

7



Well Control Methods

Driller’s Method:

The influx (kick) is circulated out of the hole

immediately after the well is shut in. Kill weight

mud is pumped in the second circulation

Wait & Weight Method:

With the influx in the well, kill weight mud is

prepared at the surface and pumped in to circulate

out the kick and kill the well in one circulation

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Driller’s Method -Example

500

SHUT-IN

700

500

SHUT-IN

500

1500

START

PUMP

700

1500

1800

1500

CIRCULATE INFLUX OUT

800

First Circulation

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500

500

1500

START

PUMP

500

1100

500

1100

0

0

KWM TO

BIT

KWM TO

SURFACESHUT-IN

SHUT DOWN

0

Driller’s Method -Example

Second Circulation

10



500

SHUT-IN

700

KWM TO

BIT

1500

START

PUMP

700

1400

705

1200

715

1100

720

200

STROKES

600

STROKES

Wait & Weight Method -Example

Kill Weight Mud to Bit

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1100

KWM TOBIT

720

SHUT

DOWN

1100

GAS TO

SURFACE

1500

1100

100

1100

0

0

0

GAS OUT KWM TO

SURFACE

Wait & Weight Method -Example

Kill Weight Mud to Surface

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Pipe Ram

Pipe Ram

Blind Ram

Annular

Surface Application

Main considerations:

• Size – inside diameter• Pressure rating

• Ram sizes

Typical Blow Out Preventer (BOP) Stack

To Choke

ManifoldKill Line

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Typical Blow Out Preventer (BOP) Stack

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Hydril GK – Annular Preventer

• 1200 psi normaloperating pressure

• 1500 psi maximumoperating pressure

• Highly wellboreassisted

Piston

Indicator

Hole

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Cameron type “U” Ram Preventer

Manual Locking Screw

Bonnet Bolt

Operating Piston

Intermediate Flange(Larger for shear rams)

Bonnet

Ram Change Piston

Ram Assembly

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Choke Manifold

O Normally Open

C Normally Closed

Master

C O

C

C

C

O

O

C C

O

C C

C

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Pipe Ram

Pipe Ram

Blind Ram

Annular




Typical Mud/Gas Separator

Outlet of the choke manifold is

connected to a mud/gas separator

The mud/gas separator is designed

to provide effective separation of

the mud and gas circulated fromthe well by venting the gas and

returning the mud to the mud pits

via gravity feed

Small amounts of entrained gas may

remain in the mud and can beremoved by the degasser located at

the mud pits

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Remote Choke Control Panel

Manualhydraulicpumpandhandle

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BOP Operating Unit

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Remote Operating Station

API RP 53 2nd Edition

Minimum of one remote control

panel should be provided along

with the main hydraulic control

manifold.

The controls should be clearly

marked

One station should be locatednear the Driller’s console and the

other should be located a safe

distance from the wellbore nearan escape route

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Jackup Drilling Rig

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After a Blowout

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Introduction to Drilling Well Control24

After a Blowout




Barge Rig Blowout

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Introd ction to Drilling Well Control

Land Rig After a Blowout

26

Well Control for drilling engineers

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