*Teknik Pemboran IIWell Control ConceptsKonsep-konsep Pengendalian Sumur

*Well Control Concepts The Anatomy of a KICK Kicks - Definition Kick Detection Kick Control (a) Dynamic Kick Control (b) Other Kick Control Methods * Drillers Method * Engineers Method

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*Causes of Kicks

*Causes of Kicks

*Causes of Kicks

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*What?What is a kick?

An unscheduled entry of formation fluid(s) into the wellbore

*Why?Why does a kick occur?

The pressure inside the wellbore is lower than the formation pore pressure (in a permeable formation).pw < pf

*How?How can this occur? Mud density is too low Fluid level is too low - trips or lost circ. Swabbing on trips Circulation stopped - ECD too low

*What ?What happens if a kick is not controlled?

BLOWOUT !!!

*Typical Kick Sequence1. Kick indication2. Kick detection - (confirmation)3. Kick containment - (stop kick influx)4. Removal of kick from wellbore5. Replace old mud with kill mud (heavier)

*Kick Detection and ControlKick DetectionKick Control

*1. Circulate Kick out of holeKeep the BHP constant throughout

*2. Circulate Old Mud out of holeKeep the BHP constant throughout

*Kick DetectionSome of the preliminary events that may be associated with a well-control problem, not necessarily in the order of occurrence, are:

1. Pit gain;

2. Increase in flow of mud from the well

3. Drilling break (sudden increase in drilling rate)

*Kick Detection5. Shows of gas, oil, or salt water

6. Well flows after mud pump has been shut down

7. Increase in hook load

8. Incorrect fill-up on trips4. Decrease in circulating pressure;

*Dynamic Kick Control[Kill well on the fly]For use in controlling shallow gas kicks

No competent casing seat No surface casing - only conductor Use diverter (not BOPs) Do not shut well in!

*Dynamic Kick Control1. Keep pumping. Increase rate! (higher ECD)2. Increase mud density 0.3 #/gal per circulation3. Check for flow after each complete circulation4. If still flowing, repeat 2-4.

*Conventional Kick Control{Surface Casing and BOP Stack are in place}Shut in well for pressure readings.

(a) Remove kick fluid from wellbore;

(b) Replace old mud with kill weight mudUse choke to keep BHP constant.

*Conventional Kick Control1. DRILLERS METHOD

** TWO complete circulations **

Circulate kick out of hole using old mud

Circulate old mud out of hole using kill weight mud

*Conventional Kick Control2. WAIT AND WEIGHT METHOD

(Engineers Method)

** ONE complete circulation **

Circulate kick out of hole using kill weight mud

*Drillers Method - Constant GeometryInformation required:

Well Data:Depth = 10,000 ft.Hole size = 12.415 in. (constant)Drill Pipe = 4 1/2 O.D., 16.60 #/ftSurface Csg.: 4,000 ft. of 13 3/8 O.D. 68 #/ft(12.415 in I.D.)

*Drillers Method - Constant GeometryKick Data:Original mud weight = 10.0 #/gal Shut-in annulus press. = 600 psiShut-in drill pipe press. = 500 psiKick size = 30 bbl (pit gain)Additional Information required:

*Constant Annular Geometry.

Initial conditions: Kick has just entered the wellborePressures have stabilized

*Successful Well Control1. At no time during the process of removing the kick fluid from the wellbore will the pressure exceed the pressure capability of

the formation the casing the wellhead equipment

*Successful Well Control2. When the process is complete the wellbore is completely filled with a fluid of sufficient density (kill mud) to control the formation pressure.

Under these conditions the well will not flow when the BOPs are opened.

3. Keep the BHP constant throughout.

*CalculationsFrom the initial shut-in data we can calculate:

Bottom hole pressure Casing seat pressure Height of kick Density of kick fluid

*PB = SIDPP + Hydrostatic Pressure in DP = 500 + 0.052 * 10.0 * 10,000 = 500 + 5,200

PB = 5,700 psig Calculate New Bottom Hole Pressure

*Calculate Pressure at Casing SeatP4,000 = P0 + DPHYDR. ANN. 0-4,000 = SICP + 0.052 * 10 * 4,000 = 600 + 2,080

P4,000 = 2,680 psig

*This corresponds to a pressure gradient of

Equivalent Mud Weight (EMW) =Calculate EMW at Casing Seat( rmud = 10.0 lb/gal )

*Annular capacity per ft of hole:Calculate Initial Height of Kick

*Calculate Height of KickhB

*Calculate Density of Kick FluidThe bottom hole pressure is the pressure at the surface plus the total hydrostatic pressure between the surface and the bottom:Annulus Drill String

*Density of Kick Fluid(must be primarily gas!)

*NOTE: The bottom hole pressure is kept constant while the kick fluid is circulated out of the hole!

In this case BHP = 5,700 psigCirculate Kick Out of Hole

*Constant Annular Geometry Drillers Method.

Conditions When Top of Kick Fluid Reaches the SurfaceBHP = const.

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*Top of Kick at SurfaceAs the kick fluid moves up the annulus, it expands. If the expansion follows the gas law, then

*Top of Kick at SurfaceIgnoring changes due to compressibility factor (Z) and temperature, we get:

Since cross-sectional area = constant

*Top of Kick at SurfaceWe are now dealing two unknowns, P0 and h0. We have one equation, and need a second one.BHP = Surface Pressure + Hydrostatic Head5,700 = Po + DPKO + DPMA 5,700 = Po + 20 + 0.052 * 10 * (10,000 - hO )

5,700 - 20 - 5,200 = Po - 0.52 *

*Top of Kick at Surface

*401,200502,000/402,0008001,100401,200 + 8002,000800 / (0.052 * 14,000)1.1013.514.61,200 * 14.6 / 13.51,298 psi

*502,000bbls2001,29800051015203040253545

* Csg DS DS CsgPressure When CirculatingStatic Pressure First Circulation Second CirculationDrillPipe PressureDrillersMethod

* Csg DS DS CsgCasing Pressure Volume Pumped, StrokesDrillpipe Pressure DrillersMethod

*165432EngineersMethod