L11-Leak Off Test, Kick Tolerance & Kick Circulation Methods

7/28/2019 L11-Leak Off Test, Kick Tolerance & Kick Circulation Methods

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Leak-Off Test & Kick Circulation Methods

Arun S Chandel

Assistant Professor. . .

09997200339

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Leak-Off TestLeak Off Test is conducted in order to find the fracture gradient of

maximum equivalent mud weight that should be applied to the wellduring drilling operations.

roce ureLeak Off Test (LOT) guide line procedures are as follows:

1) Drill out new formation few feet, circulate bottom up and collectsam le to confirm that new formation is drilled to and then ull strininto the casing.

2) Close annular preventer or pipe rams, line up a pump, normally a

cemen pump, an c rcu a e roug an open c o e ne o ensure asurface line is fully filled with drilling fluid.


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3) Gradually pump small amount of drilling fluid into well withconstant pump stroke. Record total pump strokes, drill pipe pressureand casing pressure. Drill pipe pressure and casing pressure willincrease continually while pumping mud in hole. When plot a graph

, ,

graph will demonstrate straight line relationship. When pressureexceeds formation strength, formation will be broken and let drillingfluid permeate into formation, therefore a trend of drillpipe/casing pressure will deviate from straight line that meanformation is broken and is injected by drilling fluid. We may call

pressure when deviated from straight line as leak off test pressure.

4) Bleed off pressure and open up the well. Then proceed drillingoperation.


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Leak-Off Test Calculations

Leak off test pressure can be calculated into equivalent mud weight inppg as formula below:

Leak off test in equivalent mud weight (ppg)

={(Leak off test pressure in psi) 0.052 (Casing Shoe TVD in ft)}

+(current mud weight in ppg)

=(Leak off test pressure in psi)

(Casing Shoe TVD in ft)


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Leak off test pressure = 1600 psi

Casing shoe TVD = 4000 ft

Mud weight = 9.2 ppg

=1600 psi 0.052 4000 ft + 9.2ppg ppg = 16.9

Pressure gradient = 1600 4000 = 0.4 psi/ft


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Question


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Solution


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Normal Procedure followed when a Kick is

Encountered

1) Pick up the kelly and note the position of tool jointsn re a on o e r ng spoo s.

2) Stop the pumps.

3) Open the choke line.

4 C ose t e annu ar preventer or ram preventers.

5) Close the choke.

6) Record the pit gain.

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7) Record the SIDP and SICP when they stabilize.


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Circulating out a Kick

For a well to be killed successfully, the pressure in the formationmust be kept under control during the entire kill operation. The onlyexce tion is in cases when the maximum allowable annular ressurewill be exceeded. The simplest method of doing this is to control thedrillpipe pressure by running the kill pump at a constant rate andcontrolling the pressure by regulating the choke on the choke line.

Two basic techniques are -

The Drillers method - 2 circulations; The Engineers or Wait and Weight method - 1

circulation;

pressure, particularly at the shoe.

One more techni ue called as Concurrent method

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is also used.


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Drillers Method (2 Circulations)

The Drillers Method requires two circulations.

T h e F i r s t C i r c u l a t i o n

e rs c rcu a on o e r er s e o s per orme us ng e

original mud. Co n s t a n t B H P i s m a i n t a i n e d b y h o l d i n g c i r c u l a t i n g d r i l l p i p e p r e s s u r e c o n s t a n t t h r o u g h t h e f i r s t c i r c u l a t i o n . Thechoke is o ened sli htl at the same time the um s are started u tothe kill rate. When the pumps have reached kill rate, the choke ismanipulated to maintain the Initial Circulating Pressure (ICP) on the

drillpipe.,

drastically if the kick is gas.If the kick is saltwater the annular pressure will drop slightly.When the influx has been circulated out, the pumps are stopped and

the choke closed. At this time, the two surface pressures (SIDP &SICP) should be the same.During the first circulation, the influx is circulated out with the original

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.formation pressure, the well is killed by circulating a heavier mud (kill

mud) in a second circulation.


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T h e S e c o n d C i r c u l a t i o n

Step 1: The Kill mud is pumped in the drillpipe. As with the irstcirculation, the choke is opened and the pump speed increased tothe kill rate (with the annulus pressure kept constant).

until the kill mud has reached the bit. As kill mud begins to fill thesystem, the drillpipe pressure will decrease from the initialcirculating pressure to the final circulating pressure.

Step 2: When kill mud reaches the bit, it is good practice to shut-in the well. The drillpipe pressure should fall to zero; if it doesn't, afew more barrels should be um ed to ensure that the kill mud hasreached the bit. If the drillpipe pressure is still greater than zerowhen the pump is stopped and the choke closed, the kick controlfigures should be rechecked. When satisfied, pumping is restarted,

displaces the mud in the annulus. When the kick fluids and originalmud have been displaced, the choke should be wide open. Thepump should be shut down and both SIDP & SICP should read

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zero. If so, the well should then be observed for flow.


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T o h o l d c o n s t a n t B H P d u r i n g t h e s e c o n d c i r c u l a t i o n , o n e o f

w o p r o c e u r e s s e m p o y e . a s n g p r e s s u r e s e

c o n s t a n t w h i l e p u m p i n g k i l l m u d f r o m s u r f a c e t o b i t , a n d

d r i l l p i p e p r e s s u r e i s h e l d c o n s t a n t t h e r e a f t e r u n t i l k i l l m u d

i s o b s e r v e d r e t u r n i n t o t h e s u r f a c e .

A l t e r n a t e l y , d u r i n g s e c o n d c i r c u l a t i o n , a d r i l l p i p e p r e s s u r e

s c h e d u l e c a n b e c a l c u l a t e d a n d f o l l o w e d w h i l e p u m p i n g k i l l

u u , u

c o n s t a n t t h e r e a f t e r .

T h e k i c k i s n o w k i l l e d a n d m u d s h o u l d b e c i r c u l a t e d t o

c o n d i t i o n t h e h o l e , a n d a t t h e s a m e t i m e t h e t r i p m a r g i n ( i f

a n y ) s h o u l d b e a d d e d .

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Engineers or Wait and Weight Method

This is usually a more effective method of killing a kick than the driller'smethod, if time is not a prime concern. Kill mud is pumped into thedrillpipe as soon as it is ready, which tends to reduce the high annularpressures assoc a e w gas c s. e same s u - n proce ures are

used as outlined in the previous section.

Ste 1:When all the calculations have been erformed the muddensity is raised immediately to the calculated kill mud density. Whenthe kill mud volume is ready, the pumps are started and the choke

slowly opened, while keeping the annular pressure constant until the.

as to decrease the drillpipe pressure until the kill mud reaches the bit,at which point the final circulating pressure is reached.

Step 2: Pumping is continued, holding the drillpipe pressure constantby adjusting the choke. When the kick fluids have been displaced, andfurther volume has been displaced equal to the pipe volume, the SIDP

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. .T h e k i c k i s n o w k i l l e d a n d f u r t h e r c i r c u l a t i o n s c a n b e p e r f o r m e d

t o c o n d i t i o n t h e h o l e a n d t o a d d a n y t r i p m a r g i n .


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Figure shows diagrammatically the displacement of the

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, ,using the engineers method.


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Drillers Method Vs W&W Method

1. Drillers method is preferred in wells where holestability is a problemN o n - c i r c u l a t i n g w e l l i s m i n i m i z e d .

2. Drillers method is preferred for Old rigs which havelimited fluid mixing capability-c o n t i n u o u s m i x i n g t o m a k e k i l l m u d m a y r e s u l t i n e x c e s s i v e s u r f a c e

a n d s h o e p r e s s u r e s d u e t o g a s e x p a n s i o n .

.well kill operation if using Drillers method b i t n o z z l e p l u g g i n g.

. method if kill mud is prepared at a faster rate.

5. W&W method results in lower annular pressure,particularly at shoe- d e p e n d s o n l o c a t i o n o f g a s

b u b b l e a n d d r i l l s t r i n g v o l u m e . 18


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Dynamic Kick Controlwe on e y

For use in controlling shallow gas kicks

No competent casing seat

-conductor

Do not shut well in!

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Dynamic Kick Control

(higher ECD)2. Increase mud densit

0.3 #/gal per circulation

complete circulation

4. If still flowin re eat 2-4.

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Conventional Kick Control

Shut in well for pressure readings.

(a) Remove kick fluid from wellbore;

ep ace o mu w we g mu

.

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Drillers Method - Constant Geometry

Well Data:

Depth = 10,000 ft.

Hole size = 12.415 in. (constant)Dri Pipe = 4 1 2 O.D., 16.60 t

Surface Csg.: 4,000 ft. of 13 3/8 O.D. 68 lb/ft

. . .

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Drillers Method - Constant Geometry

Additional Information re uired:

Kick Data:

Original mud weight = 10.0 #/gal

Shut-in annulus press. = 600 psiShut-in drill pipe press. = 500 psi

Kick size = 30 bbl (pit gain)

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ConstantSIDPP = 500 psi

SICP = 600 psi

Geometry.

DP OD

= 4.5 in

n a

conditions:Kick has ust 4,000 ft

Hole dia= 12.415 in

entered thewellbore Annular

Ca acit

have stabilized = 0.13006bbl/ft

231 ft

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,BHP = 5,700 psig


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Successful Well Control

1. At no time durin the rocess of

removing the kick fluid from thewellbore will the pressure exceed the

4 the casing

the wellhead equipment

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Successful Well Control

2. When the process is complete the wellbore iscomp e e y e w a u o

sufficient density (kill mud) to control theformation ressure.

Under these conditions the well will not flow when the .

.

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Calculations

-

Casing seat pressure

e g t o c

Density of kick fluid

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Calculate New Bottom Hole Pressure

PB = SIDPP + Hydrostatic Pressure in DP

=

+ 0.052 * 10.0 * 10,000

= ,

PB = 5,700 psig

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Calculate Pressure at Casing Seat

P = P +P -, . . ,

= SICP + 0.052 * 10 * 4,000

= 600 + 2,080

P4,000 = 2,680 psig

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Calculate EMW at Casing Seat

This corresponds to a pressure gradient of

psi/ft670.0psi680,2 =

Equivalent Mud Weight (EMW) =,

ft/psi670.0.

)gal/lb)(ft/psi(

052.0

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( mud = 10.0 lb/gal )


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Calculate Initial Height of Kick

Annular capacity per ft of

hole:

L)DD(

4

v2

P

2

Hx =

bbl

gal*in12*)5.4415.12(

3

322 =

bbls/ft0.13006 =

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Calculate Height of Kick

o e,oo omacoe g

bbl30V

B .bbl/ft0.13006v

x

B ===

ft231 =hB

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Calculate Density of Kick Fluid

The bottom hole pressure is the pressure at thesurface plus the total hydrostatic pressure betweenthe surface and the bottom:

Annulus Drill String

P SICP P P SIDPP PB MA KB MD= + + = +

600 0052 10+ . *

+ = +*(10,000-231) P 500 (0.052*10*10,000)KB

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, ,KB+ + = +


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Density of Kick Fluid

=P psKB

20 .231*052.0

KB =

(must be primarily gas!)

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Circulate Kick Out of Hole

NOTE:

The bottom hole pressure is

kept constant while the

the hole!

In t is case

BHP = 5,700 psig

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Annular

GeometryDrillers Method.

Conditions When Top ofKick Fluid Reaches theSurface

36BHP = const.


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Top of Kick at Surface

As t e ic ui moves up t e annu us, it expan s. I

the expansion follows the gas law, then

VPVPRTnZRTnZ BBB000

=

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I norin chan es due to com ressibilit factor Zand temperature, we get:

hvPhvP

BB00

=

=

hPhP.e.i BB00 =

Since cross-sectional area = constant

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.)constv(v B0 ==


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We are now dealing two unknowns, P0 and h0. Wehave one equation, and need a second one.

BHP = Surface Pressure + Hydrostatic Head

, = o KO MA

5,700 = P + 20 + 0.052 * 10 * (10,000 - h )

- - = - *BB hP

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, , o .oP


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231*5700*52.0PP4802

00 =

2

00 =

684,684*4480480P

2

0

+=

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ps,0 ==


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y, r r

A kick is NOT a blowout.

Most blowouts are due to human error inhandling a kick.

The fundamental principle in well control isCONSTANT BOTTOM HOLE PRESSURE

u e we n us ng e orSHUT IN using the annular BOP.

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Im ortant Princi lescontinued

Control a kick with the bit on bottom.

pressures.

Use Measured Depth (MD) for volumes andsp acemen s.

Establish pore pressure by recording the shut indrill pipe pressure.

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Im ortant Princi lescontinued

Maintain constant bottom hole pressure by-

us the casing pressure.

Assume and desi n for a as kick unlessthe reservoir fluid is known.

Gas is more difficult to handle - primarily

due to large expansion during circulatingout a kick. (Boyles Law: P1V1 = P2V2)

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If You Get it Wrong!

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L11-Leak Off Test, Kick Tolerance & Kick Circulation Methods

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Transcript of L11-Leak Off Test, Kick Tolerance & Kick Circulation Methods