L10-Causes of Kicks, Detection Techniques & Equipments [Compatibility Mode]

7/28/2019 L10-Causes of Kicks, Detection Techniques & Equipments [Compatibility Mode]

1/49


2/49

A kick is the term used to describe the inflow of formationfluid into the wellbore during drilling operation.

This arises due to the formation ressure bein reaterthan the hydrostatic pressure imposed by the mud column.

This can happen in a normal or abnormally pressuredformations.

A kick may be primarily composed of salt water, oil, naturalgas or a combination of the fluids. The influx of formationfluid may arise for a variety of reasons

e se n c u e :

2


3/49

Ca u s e s o f K i c k s

3


4/49

Ma or Causes

Swabbing; Not keeping the hole full;

K i c k s o ccu r r i n g d u r in g d r i l l i n g o p e r a t i o n s most often.

K i c k s g en e r a l l y o c c u r d u r in g t r i p s with the influx occurring

full. Swabbing is the result of the piston effect of the drillpipe

due to excessive trip speed resulting in instantaneous vacuum

4

.


5/49

u u w

.m a y o c cu r d u e t o :

Penetration of an abnormall ressured zone

Accidental dilution of the mud by fluid addition atsurface

Dilution of mud b influx from an a uifer ex osed toopen hole;

Gradual mud density reduction due to gas cut andfailure to degas the mud at surface;

Improper mud mixing and poor quality control inmeasurement.

5


6/49

Low Level of Drillin Fluid ColumnNot keeping the hole full

Two conditions may lower

annulus. These are:

Failure to fill the holeduring a trip;

Lost circulation during

6


7/49

Hole Fill During Trips

,volume. Monitoring of the volume of mud filling the hole is done with the use of

the Trip tank or Possum Belly Tank. The trip tank is a small mud pit (Approx.

50bbls) separate from the active pits. This trip tank is fully equipped with a

vo ume gauge a can e mon ore rom r g oor or mu oggers conso e. n

monitoring the trip, the driller must calculate the theoretical mud volumedisplaced by one or five stands of drillpipe. During the trip, the driller then

measures the actual mud volume um ed into the hole for each stand of i e

pulled.

Lost CirculationLost circulation is the loss of substantial quantity or whole mud into the formation. It

may occur as a result of:

Mud loss to cavernous or vugular formation;

Mud loss to fractures opened by excessive annulus pressure. This may be due to

annular blockage, surge pressures, excessive hydraulics, pressures imposed to

break mud gel strength.

7

Lost circulation will result in insufficient mud column and thus reduction in bottom

hole pressure. Kick due to lost circulation can be a major well control problem. If thewell cannot be shut in, an underground blow out can occur.


8/49

w

Sw a b b i n g i s t h e r ed u c t i o n o f b o t t o m h o l e p r e s s u r e ca u se d b y u p w a r d p i p e m o v em e n t - r e su l t i s r e d u c e d o o m o e p r e s s u r e . g r p sp e e ca n e a o

i n s t a n t a n e o u s v a cu u m b e l o w t h e b i t . Th e sw a b p r e s su r e d e p e n d s o n :

Pipe velocity; Bit and/or BHA balling; Clearance between pipe and hole - the smaller the annular

cross section, the greater the swabbing action;

- ,swabbing action.

8


9/49

P r e Re co r d e d K i c k D a t a

9


10/49

ax mum or ng as ng ressure

The casing and blowout preventer (BOP)are es gne or e eren expec epressures during each drilling phase.

.

The pressure requirements are based on

caused by a gas kick.

10


11/49

MAASP(Maximum Allowable Annular Surface Pressure)

This is the annular pressure at the surface that correspondsto the pressure at the weakest point of the hole. Thefracture gradient at the last casing shoe traditionallydefines the weakest point. The MAASP represents the

annulus pressure which may be expected to result in loss of.

MAASP = 0.052 x (Frac ) x Dw

Frac = Fracture pressure at shoe equivalent mud wt in ppg

= current mud weight in ppg / Dw = TVD of weakest point

11


12/49

g apac y or e g ng u

Although this data does not appear in theworksheet it is im ortant as it defines thenumber of circulation cycles necessary to regainprimary control with given change of mud. The

rig capacity depends on total reserves of,

maximum rate of addition to system. Themaximum rate of addition is measured in Ib/min

.available on rig.

12


13/49

S stem Pressure Losses at SlowPump Rate

To control circulating a kick out of the hole without the risk ofcausing a second influx or losses from breaking down theorma on w excess ve annu ar pressures s ow a c rcu a ng ra e(SCR) is used. of the well. This is is dependent on the rig, but thisis usually about 20 or 30 strokes per minute. This slow rate must

be taken:

At the start of each tour;

If the mud weight changes;

After bit changes;

Every 500 ft drilled.

13


14/49

Example 1:

= .

Casing shoe TVD = 4000 ft

Estimated fracture pressure = 6200 psi

Annular pressure losses = 350 psi

=

Calculate MAASP.

14


15/49

Solution:

ann.

Equivalent mud wt.= 2350/(0.052x4000) = 11.3 ppg

Fracture press. Gradient = 6200/(0.052x4000)= 29.8 ppg

Frac = 29.8 11.3= 18.5

= =

15


16/49

Height of Influx

Height of influx, ft = pit gain, bbl annular capacity, bbl/ft

Ex am p le 1

Determine the height, ft, of the influx using thefollowing data:

Pit gain = 20 bbl(Dh = 8.5 in. Dp = 6.5)

S o l u t i o n

Height of influx, ft = 20 bbl 0.029 14 bbl/ftHeight of influx = 686 ft

16


17/49

arre s o n ux oppos e = a n arre s oppos e

Hei ht of influx o osite DP ft= Barrels o . DP Annular Ca acit

Ex am p l e 2

eterm ne t e e g t n t, o t e n ux us ng t efollowing data:

Pit gain = 20 bbl

Hole size = 8.5 in.

Drill collar OD = 6.5 in. ; Drill collar length = 450 ft

Drill pipe OD = 5.0 in.

17


18/49

So lu t i o n 2

18


19/49

19


20/49

Estimated Type of Influx

Influx weight= mud wt ((SICP SIDPP)/height of influx X 0.052)

then:1 3 ppg = gas kick

=7 9 ppg = saltwater kick

Question 3

Determine the type of the influx using the following data:

- =

Shut-in drill pipe pressure = 780 psi

Mud weight = 15.0 ppg

20


21/49

Pit gain = 25 bbl

Hole size = 8.5 in.

Drill collar OD = 7 in. ; Drill collar length = 250 ft

Drill pipe OD = 5.5 in.

So lu t i o n 3

The influx is saltwater kick

(influx weight = 8 ppg)

21


22/49

22


23/49

Kick DetectionThe single most important step to blowout prevention isclosing the blowout preventers when the well kicks. The

working life. It ranks with keeping the hole full of fluid as amatter of extreme importance in drilling operations.(Chevron Well Control Manual)

Be prepared and maintain a kick control Work Sheet at all

times.

A kick can occur at any time during the drilling of a well. To preventany major catastrophe therefore, early detection of a kick is essential

to primary well control. As a primary precaution, it is important forall personnel including the mud logger to be always in a state of readiness. Certain pre-kick information must be collected and

23

.pressures data. A kick control Work Sheet (see Appendix) must be

maintained for this purpose.


24/49

There are a number of indicators that provide early warningof kick occurrence - positive kick indicators are:

Mud pit level/flow Increase;

Incorrect hole fill up during trip; Decrease in standpipe pressure/Increase in pump rate;

ncrease ecrease n r s r ng we g

Potential indicators are:

Increase in penetration rate; Lost circulation; Chan es in as levels mud densit and conductivit

24


25/49

Po s i t i v e K i c k I n d i c a t o r s

25


26/49

. u eve ow ncrease

.the influx of formation fluid displaces the mud in theannulus, the pit level would increase in the active mudtanks. There would also be evidence of increase inre urn ow ra e ogge . e e ec veness o pgain/flow increase depends on:

Mud fluid base and rheology; Minimum sensitivity of the measuring systems

But remember Gas kicks are more difficult to detectthan oil /water due to its compressibility ...

26


27/49

. ncorrec -up ur ng r ps

If the hole does not take the correct volume ofmud for the volume of pipe pulled from the hole

the well bore

maintaining independent records of volume takento fill the hole for every 5 stands

If the hole fill is not correct go back to bottomand circulate bottoms up to check what is at the

27


28/49

The U-Tube Analo

28


29/49

3. Decrease in Stand i e Pressure Increasein Pump Rate

- .fluid into the annulus creates an imbalance

resulting in a decrease in hydrostatic pressure in. ,gravity helps move drilling fluid down the hole,requiring less energy from the pump. This will

29


30/49

. ncrease ecrease n r s r ng e g

Any influx into the wellbore from the formationreduces the buoyancy of the annular drilling fluid.

change in weight as an increase in drill string

weight.

For very large kicks, fluid may enter the annuluswith enough force to cause a decrease in

indicated string weight.

30


31/49

Po t e n t i a l K i c k I n d i c a t o r s

31


32/49

1. Increase in Penetration Rate(Drilling Break)

A marked increase in rate of penetration (ROP) may indicate

either changes in the type of formation being drilled or areduction in the differential between the mud pressure and poreressure. Generally, the following parameters affect the ROP:

Rock type; Formation bulk density/porosity;

Differential pressure; Hydraulics; Weight on bit; Rotary speed;

porosity change. Drilling rate tends to

decrease with depth. Thus when a

drilling break occurs, it may be an

Personnel/equipment. evidence of transition to an abnormalzone. It is crucial at this point to stopdrilling and check for flows.

32


33/49


34/49

3. Chan es in Gas Levels MudDensity/Conductivity

more of the following sources: - Liberated gas which is the measured gas from the return mudflow, released from the pore spaces of the drilled cuttings. It is

e so-ca e ac groun gas ur ng c rcu a on. ere soverbalance, and the ROP is constant with flow rate, this liberatedgas;

Produced Gas enters the wellbore from adjacent permeable.when ROP is constant is evidence of produced gas;

Recycled gas is the gas recirculated into the hole. It appears ondetection equipment as an increase in background levels;

additives; Connection gas and trip gas are short duration gas peaks

caused by swabbing action.

34


35/49

3. Chan es in Gas Levels MudDensity/Conductivity

Depending on sensitivity level surface monitors should detect a

relatively steady level of gas extracted from mud during normaldrilling. This background gas level may show occasional

variations depending on penetration rate, mud pumping rate,

hydrocarbon content of section drilled. Under normal conditions,

the background gas should remain within about 50% of local.

they are significant or not. Thorough inspection of gas monitoring

systems and calibration as part or routine maintenance exercise

35


36/49

Connection and trip gas are most common while

that pressures are near balance, making foroptimum ROP. Swabbing is the main cause ofconnection/trip gas as it creates negativei erentia pressure. . E ects o gas expansion at

surface are varied. Evidence includes:

Rapid fall in flow line mud density; Increase in return flow; Mud it level increase

Rapid increase in total gas or hydrocarbon levels.

36


37/49

W e l l Co n t r o l Eq u i p m e n t s

37


38/49

Well Kill Circulating System

38


39/49

Prevention

System

39


40/49

BOP

Stack inVariousOperation

al Modes

40


41/49

Annular Preventer

... consists of an annularrubber sealing element which,when pressure is applied,c oses aroun e r p pe orkellySince pressure can be applied

ro ressivel the annularpreventer can be made toclose on any size or type ofdrillpipe

may allow a small leakage offluid and permit the pipe to berotated within the annular

through, - slowly!

41


42/49


43/49

Ram Preventers

Pipe rams: These have semi-circular openings that match thediameter of the pipe being used. A drillstring comprising different

, - - ,sets of pipe rams to accommodate both sizes of pipe. These are alsooperated hydraulically, and close around the tubing portion of drillpipe when used.

Blind rams: These are designed to close off the hole when no pipe

is in the hole. If they are shut on drill pipe, they will flatten the pipe,.

Shear rams: These are a form of blind rams that are designed tocut drill i e when closed. This will result in the dro in of the

drillstring below the BOP stack unless the stack is designed in such away as to have a set of pipe rams below the shear rams on which atool joint can be supported. They will stop the flow from the well.

rams and the annular preventer have failed.

43


44/49

Choke and Kill Lines

After the BOP is closed, high-pressure fluid can be released

at carefully controlled rates by use of a hydraulicallycontrolled valve (choke valve). The choke line carries

.goes through the poor-boy de-gasser which removes thefree gas. It then returns to the pits for treatment andfurther de-gassing with the vacuum de-gasser

The kill line is used to introduce heavy drilling fluid to thewell through a check-valve on the BOP in order to controlhigh formation pressures. It fills the borehole from the top

ns ea o us ng e r p pe o e ore o e rom ebottom). It is also used to fill the annulus when pipe isbeing tripped out

44


45/49

Other Components

Diverter SystemIn certain cases, it may be necessary to allow the well to blowout in a controlled

manner rather than be shut-in. This is common in shallow sections due to

insufficient casing to contain a kick. In these circumstances, a diverter system

will be used. This is a relatively low pressure system, often using the annularpreventer to seal off the annulus below the flow line. The diverter line will then be

the rig.

Kell CocksThe BOP stack can only be used to stop the flow of fluids from the annulus.

Additional valves are used to stop the flow within the drillstring. These valves

include kelly cock valves and internal blowout preventers.

.

valves may be installed as a permanent part of the drillstring or just when a kickoccurs. They can be automatic or manually controlled and they consist of subs

with valves that may be of a spring loaded ball type, a flapper valve type, or dart

type.

The drawback of these valves is that while preventing a blowout up the string

they prevent the shut-in drillpipe pressure from being monitored. 45


46/49

Choke Manifold

choke manifold. This manifold must be able to work under a variety of

conditions, such as high pressure, with oil, gas, mud and water, and be

capable of withstanding the effects of abrasive solids (sand and shale) in the

c u s. e man o s ou e capa e o con ro ng e we us ng one o

several chokes and be able to divert flow to one of several areas, such as

reserve pits, burn pits, or degassers. Since vibrations occur during kill

o erations, the manifold must be securel anchored down, with as few bends

as possible to prevent washouts under high pressure flow conditions.

AccumulatorThe system used for closing the BOP's is a high pressure hydraulic fluidaccumulator. Hydraulic fluid is stored under pressure, the pressure being

provided by stored nitrogen. When hydraulic oil is forced into the accumulator

, , ,

potential energy. When the BOP's are activated the pressured oil is released,either opening or closing the BOP's. Hydraulic pumps replenish the

accumulator with the same amount of fluid that was used to operate the BOP.

ccumu a ors common y ave m n mum wor ng pressures o ps an

maximum working pressures of between 1500 and 3000 psi.

46


47/49

Closing the

The Blowout Preventer

(BOP) Stack

Closes the annulus

Has multiple redundancies

47


48/49

Drill Pipe Side

The top valve is a FULL

OPENING SAFETY VALVE.Installed on the drill pipe when

a kick is taken while tripping.

The lower valve is an INSIDE

BOP - it is potentiallyDANGEROUS and its use

should be avoided!

48


49/49

continued

To provide permanent protection in ther p pe w en an ng a c a r ng

float valve should be used.

-immediately above the bit.

49

L10-Causes of Kicks, Detection Techniques & Equipments [Compatibility Mode]

Documents

Transcript of L10-Causes of Kicks, Detection Techniques & Equipments [Compatibility Mode]