6.Monitoring Well Control

Instituto Superior TécnicoUniversidade de Lisboa

Masters in Petroleum Engineering 2014-2015

Drilling Engineering Course

José Pedro Santos Baptista

Mining and Geological Engineering Msc.Petroleum Engineering Msc.

Drilling Engineering Course

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6. Well Control and Monitoring

Well control

Causes and Assessment, Kill methods

Monitoring

Drilling Engineering Course 2014-2015 Masters in Petroleum Engineering


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Causes of incidents


Inadequate fulfilment of standards and procedures

Inadequate response from the rig personnel (training and skills)

Poor management (leadership of the person in charge)

Inadequate work practices

Inadequate well design

No compliance with the drilling parameters (trends)


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Causes of incidents


Poor alignment/integration with/of the service providers

Poor risk management and management of change (lessons learnt)

Poor communication between stake holders in the drilling process

Lack of communication/clarification of the operations (work instr.)


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Kick and Blowout


“A flow of formation fluids into the wellbore during drilling operations. The kick is physicallycaused by the pressure in the wellbore being less than that of the formation fluids, thus causingflow.”

MW is Too Lowhydrostatic pressure exerted on the formation by the fluid column may be insufficientto hold the formation fluid in the formation (if the mud density is suddenly lightenedor is not to specification to begin with, or if a drilled formation has a higher pressurethan anticipated, underbalanced kick)

Dynamic and Transient Fluid Pressure EffectsMotion of the drillstring or casing, effectively lower the pressure in the wellborebelow that of the formation(induced kick)


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Kick and Blowout


“Uncontrolled flow of formation fluids from a well. An uncontrolled flow of formation fluidsfrom the wellbore or into lower pressured subsurface zones (underground blowout).”

Uncontrolled flows cannot be contained using previously installed barriers and requirespecialized services intervention.

A blowout may consist of water, oil and gas flow or a mixture of these.

May occur during all types of well activities and are not limited to drilling operations.

In some circumstances it is possible for the well to seal itself with rock fragments fromcollapsing formations downhole (well bridge over).


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Kick and Blowout


“Uncontrolled flow of formation fluids from a well. An uncontrolled flow of formation fluidsfrom the wellbore or into lower pressured subsurface zones (underground blowout).”


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Kick Causes


1 – Failure to keep the hole full of proper fluid weight

2 – Drilling into zones of known pressure with low MW

3 – Drilling into unexpected abnormal formation pressures

4 – Lost Circulation

5 – Unloading mud by pulling the BHA (swab)

6 – Mud Weight high enough to drill but not to trip (low ECD)


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Kick Causes – Low density Fluids


Causes

Dilution of the drilling fluidsWeighting material settling outElimination of weighingGas/oil saltwater cutting

Prevention

Diligence in the mud pitsInvestigation of any MW reductionMaintaining mud properties (monitoring parameters)


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Kick Causes – Abnormal Formation Pressure


Causes

Permeable barrier or rapid deposition sealing fluids inUplift of a normally pressure zoneCharged up zone due to channelling

Prevention

Seismic data and offset well analysis (study of drilling logs)Pore pressure detection technology and monitoringMonitor Cavings (cuttings)


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Kick Causes – Not Keeping the Hole Full


Causes

Not monitoring the displaced volume of mud displaced by the drill string

Prevention

Proper use of Trip Tanks and Trip SheetsMud logging unit (pipe displacement monitoring)Pump stroke counter (strokes to fill the well when POOH)Pit volume monitoring (total volume of mud active sys.)Monitoring the well all the time (i.e logging ops.)


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Kick Causes – Lost Circulation


Causes

Formations prone to take fluidHigh MWSurge pressuresHigh ECD

Prevention

Monitoring/maintenance of mud propertiesGood surge pressure estimationCope with fluid losses before resuming drilling opsConsidering setting intermediate casingMonitor flowManage ECD in low clearance annulus


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Kick Causes While Tripping


The great majority of well control incidents are reported while tripping in or out of the hole!!

Loss of ECD, Swabbing, Not filling the Well, Surging/Loss circulation, less focus of the drillingcrew, insufficient MW

A trip tank is essential to keep the hole full while tripping (most important rig device used in kickprevention), as is a trip sheet to monitor the displacement done by pipe movement

From 30-100 bbl capacityDetect maximum volume variations of ½ bbl

Re-circulating Trip TankGravity Trip Tank


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Kick Causes While Tripping


The great majority of well control incidents are reported while tripping in or out of the hole!!


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Well Control Stages


Primary Well Control Use of drilling/completion fluids weight to provide sufficienthydrostatic pressure to prevent an influx of formation fluids (kick)

Secondary Well Control Closing the safety valves (if any) and the BOP and implementing akick control method to kill the well with a “kill mud weight”

Tertiary Well Control Relying on the strength of the formations to contain the wellborefluid flowPlugs (barite, cement, gunk), well capping or relief well


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Barriers


Primary Barrier

Consists of a homogeneous mud column with a hydrostatic overbalance on the PP

Secondary Barrier

Consists of a cemented casing, wellhead, pipe ram or annular preventer and adrillstring with a Kelly valve or check valve

The principle of a double barrier system should be in place during testing, completions, workovers and plugging and abandonment of a well


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Blow Out Preventer


y

Kill Line Choke Line

VR Plug


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Blow Out Preventer


Annular BOP (Hydrill)

Seals on any object that is run on the wellboreSize: 7’1/16 – 29’1/2Pressure 2000-20000 psi


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Blow Out Preventer


Pipe Ram

Fits specific pipe sizesNeed the pipe to be in place to make a sealOnly holds pressures from below


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Blow Out Preventer


Shear/Blind Ram

Cuts the drill pipe (5’’) and seals the hole

Can seal on open hole w/ top seal and side packers

Emergency equipment


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Blow Out Preventer


Hydraulic Accumulator

Choke Manifold

Kill Line


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Blow Out Preventer


Choke Manifold

A series of high pressure valves, used to lower the pressure of the well head, with several lateraloutlets (lines)

Attached to the BOP stack with a choke line (helps to maintain back pressure, preventing furtherinflux) and allows the fluid to be diverted

The choke can be operated manually or remotely ( usually on the rig floor, choke panel)

This manifold is connected to the mud gas separator


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Blow Out Preventer


Mud Gas Separator (MGS)


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Flow Monitoring


Flow inside the well should be monitored at all times but especially after all the drilling breaks,when tripping : off bottom, at the lowest casing shoe, prior to pulling DCs through the BOP stack

If the well flows even when the muds ceased to pump, then: SHUT-IN THE WELL

The well may flow due to underbalanced U-Tube, fracture flow back or due to ballooning. if theflow is not being caused by the above mentions reasons

SHUT-IN THE WELL!


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Constant Bottom Hole Pressure


There are two main models to maintain well control

Drillers method Wait and Weight method

All well control methods should be thought before hand by measuring/determining

Slow circulating rates (SCR)Determine friction lossesMeasure FL at rates we plan to pumpTest Several rates (ig. 20, 30, 40 spm)Test with all rig mud pumps

Pre-calculate pipe and hole capacities

Pre fill a Kill Sheet


26Drilling Engineering Course 2014-2015 Masters in Petroleum Engineering


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Drillers method

Step 1: Circulate the gas kick out maintaining the bottom hole pressure constant (original mud)

The casing pressure will be constant until the kick volume is out of the hole

Step 2: Circulate Kill Mud Weight (KMW) in maintaining the bottom hole pressure constant

Circulation pressure decreases from the initial circulation pressure to final circulationpressure (while heavier muds fill up the drill pipe)

Final circulation will have constant pressure until the kill mud reaches the surface


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Drillers method


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Wait and Weight Method

Circulate gas out of the hole with the Kill Mud Weight (KMW) maintaining the bottom holepressure constant

This is done with only one circulation where pressure decreases from initial circulating pressure(while heavier muds fills up the drill pipe)


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DM Versus W&W method


Drillers Method

Pro’sLess calculations are required, simpler methodCirculation can start immediately (reducing gas migration)Removes influx and stabilises pressure fasterBest option if weighting agent is limited

Con’sRequires at least two circulationsUnder certain circumstances the shoe pressure will be higherTwo circulations might cause damage to the well control equipment


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Pro’sCreates lower pressures on casing shoeIn a long OH section, it is the least likely method to induce lost circulationRequires one less circulation, less damage to well control equipmentMost used method (standard)

Con’sRequires longest waiting period before circulating, if hole section is long cuttings maysettle and plug the annulusGas migration is a problem while the density of the system is increased


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Engineer’s Method


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Swiss Cheese Model


Engineer’s Method


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Swiss Cheese Model


Engineer’s Method


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Swiss Cheese Model


r’s Method


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Swiss Cheese Model


r’s Method

38Drilling Engineering Course 2014-2015 Masters in Petroleum Engineering

End of Well Control and Monitoring

Next Chapter: 7. Exercises

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6.Monitoring Well Control

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