3 1 well control

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Network of Excellence in Training Basic Well Control © COPYRIGHT 2001, NExT All Rights Reserved Basic Well Control • Lecture Contents; – Lecture Objectives, – Introduction, – Primary Control, – Warning Signs of Kicks, – Secondary Control, – Well Killing Procedures, – Kill Sheet © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Lecture Objectives – At the end of this lecture YOU will be able to: • Define the term “kick”, • State warning signs of a kick, • Describe the drawback of uncontrolled kicks, • State primary and secondary control procedures, • List well killing procedures and the various calculation to fill-up the well control work sheet © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Introduction; – In simple terms, kick occur when the formation pressure exceeds the mud hydrostatic pressure, – The resultant negative differential pressure is forced into the wellbore, – If the flow of the kick is controlled then the well is killed, – Blow-out occurs when the kick (influx) is uncontrolled, – The rig crew must be alert all times in order to take immediate action to bring the well under control © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Introduction; – Uncontrolled Kick ! © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Introduction; – And result result ! © COPYRIGHT 2001, All Rights Reserved Basic Well Control Causes of Kicks  Tripping Drilling into an overpressured zone Failure to fill hole Inadequate mud weight Gas cut mud Lost circulation © COPYRIGHT 2001, All Rights Reserved Basic Well Control A study of 55 blowouts during a 10-year period lists the following primary causes of blowouts: Cause % of Total Failure to keep hole full 42 Insufficient Mud weight 15 Lost Circulation 22 Swabbing 16 Other © COPYRIGHT 2001, All Rights Reserved Basic Well Control Mud hydrostatic pressure Pf Pressure Changes During A Kick © COPYRIGHT 2001, All Rights Reserved Basic Well Control Mud hydrostatic pressure New heavy mud Pf Pressure Changes During A Kick 10 © COPYRIGHT 2001, All Rights Reserved Basic Well Control Annular Gas Expansion: Conclusions • Gas expands as it rises (Boyle’s Law) • Gas Pressure reduces as it rises • Gas height increases, mud height decreases • P must rise to compensate if BHP stays the same an 40 © COPYRIGHT 2001, All Rights Reserved Basic Well Control Annulus Pressure Rises Annulus pressure rises when circulating out a gas kick because gas expansion reduces the height of mud in the annulus 41 © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Well Killing Procedure; – Drillers Method • This method is executed in two circulation, • The well is kept closed-in while the pressures stabilize, • One circulation to expel the influx, ( meanwhile kill mud weight is prepared), • The second circulation with the kill mud is pumped around the wellbore to kill well 42 © COPYRIGHT 2001, All Rights Reserved Basic Well Control Features of The W&W Method • Wellbore and surface pressures are generally lower with the Wait-andWeight method, particularly if the influx contains gas • The maximum pressure exerted on the last casing shoe, which is assumed to be the weakest point in the hole, is lower with the Wait-andWeight method as long as the open hole annular volume is larger than the drillstring capacity, 43 • The well is under pressure for © COPYRIGHT 2001,the All Rights Reserved Basic Well Control The disadvantages of W&W method: • It requires the longest waiting time prior to circulation • If the annulus was full of cuttings at the time the kick was taken there may be a danger of packing off • Gas migration may become a problem while waiting for the mud to be weighted up 44 © COPYRIGHT 2001, All Rights Reserved Basic Well Control Differences between Methods Wait & Weight • • • • Completed in one circulation Lower pressures on the wellbore Takes less time overall The preferred method in most cases Drillers Method • • • Completed in two circulations Higher pressures on casing shoe Must be used in HPHT wells 45 © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Secondary Control; – Example: • While drilling 1/2” hole at 8000’ TVD, a pit gain of 10 bbls occurs The well is shut-in and the following pressures were recorded: – SIDPP = 600 psi, – SICP = 800 psi • The BHA consists of 600’ of 3/4” OD DC, plus 1/2” DP Last casing shoe is at 7000’, • Mud weight is 10.2 ppg, fracture gradient is 0.765 psi/ft • Identify; the influx, calculate MAASP, and kill mud weight using 200 psi overbalance 46 © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Secondary Control; – Answer: • MAASP = ( 0.765 - 0.5304 ) x 7000 = 1642 psi, • Annular space between DC and OH = 0.0191 bbl/ft, • Influx height; Hi = V / A = 10 / 0.0191 = 524 ft, • Influx type; Gi = Gm - [ (SICP - SIDPP ) / Hi ] = 0.5304 - [ ( 800 - 600 ) / 524 ] = 0.148 psi/ft (gas), • Kill mud weight; Gk = Gm + [ (SIDPP + S ) / D ] = 0.5304 + [ (600 + 200 ) / 8000] = 0.6304 psi/ft, = 12.12 ppg 47 © COPYRIGHT 2001, All Rights Reserved Example Well Depth 7560' MD / TVD 13 3/8” casing shoe at 6000' MD / TVD.  A leak-off test was carried out at the 13 3/8” shoe using a mud weight of 10.0 ppg A surface pressure of 1400 psi was recorded Bit Size 12 ¼” Drill pipe 5” 19.5 lb/ft capacity=0.01776 bbl/ft Drill Collars 8” x 13/16”~ x 530' capacity=0.0080 bbl/ft Drill pipe / Casing annulus capacity=0.1293 bbl/ft Drill pipe / Open hole annulus capacity=0.1215 bbl/ft Drill Collar / Open hole annulus capacity=0.0836 bbl/ft Well is shut in with the following data SIDPP : 550 psi, SIC : 680 psi, Kick Volume : 25 bbls Mud Weight in use is 11.0 ppg Pump is a National 12-P-160, using ½” liners Pump output is 0.119 bbl/stroke Slow Circulating Rate Pressure is 500 psi at 30 spm 48 © COPYRIGHT 2001, All Rights Reserved Basic Well Control What is the formation pressure ? What is the kill mud weight required to balance formation pressure?    What is the initial circulating pressure?   What is the final circulating pressure, once the kill mud has reached the bit? What is the gradient of the influx? 49 © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Kill Sheet 50 © COPYRIGHT 2001, All Rights Reserved Basic Well Control (1) What is the kill mud weight required to balance formation pressure? ANSWER (2) How many strokes will be required to pump kill mud from the surface to the bit? ANSWER (3) ppg _ _ strokes.  How many strokes are required to pump from the bit to the casing shoe? ANSWER _ strokes (4) What is the total annular volume? ANSWER : barrels (5) What is the MAASP at the time the well is shut in? ANSWER (6) What is the new MAASP once the kill mud has been circulated around the well? ANSWER 51 (7) psi psi What is the initial circulating pressure? ANSWER _ psi © COPYRIGHT 2001, All Rights Reserved Basic Well Control (8) What is the final circulating pressure, once the kill mud has reached the bit? ANSWER (9) psi What is the gradient of the influx? ANSWER - psi/ft  (10) Approximately how long will it take to circulate around the well at 30 spm? ANSWER _ minutes  (11) The well is shut in What is the drillpipe pressure drop per 100 strokes as kill mud is being pumped to the bit?   ANSWER psi/100 stroke 52 © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Now you should be able to: – Define the term “kick”, – State warning signs of a kick, – Describe the drawback of uncontrolled kicks, – State primary and secondary control procedures, – List well killing procedures and the various calculation to fill-up the well control work sheet 53 © COPYRIGHT 2001, All Rights Reserved Network of Excellence in Training Basic Well Control End of Lecture © COPYRIGHT 2001, NExT All Rights Reserved ... action to bring the well under control © COPYRIGHT 2001, All Rights Reserved Basic Well Control Introduction; Uncontrolled Kick ! â COPYRIGHT 2001, All Rights Reserved Basic Well Control • Introduction;... and secondary control procedures, • List well killing procedures and the various calculation to fill-up the well control work sheet © COPYRIGHT 2001, All Rights Reserved Basic Well Control • Introduction;...Basic Well Control • Lecture Contents; – Lecture Objectives, – Introduction, – Primary Control, – Warning Signs of Kicks, – Secondary Control, – Well Killing Procedures, –
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