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Petroleum Engineering 406

Petroleum Engineering 406. Lesson 3 Well Control. Read. Well Control Manual Chapter 7-8 Homework 2 Due Jan. 30, 2001. Content. Equivalent Mud Weights - EMW Casing Seat Tests Kick Tolerance Differences in Kick Types Reaction of Gas in the Wellbore. Equivalent Mud Weight.

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Petroleum Engineering 406

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  1. Petroleum Engineering 406 Lesson 3 Well Control

  2. Read • Well Control Manual • Chapter 7-8 • Homework 2 Due Jan. 30, 2001

  3. Content • Equivalent Mud Weights - EMW • Casing Seat Tests • Kick Tolerance • Differences in Kick Types • Reaction of Gas in the Wellbore

  4. Equivalent Mud Weight • EMW - the total pressure exerted at a given depth expressed in ppg equivalent • EMW = Surf. Press./(0.052*TVDint)+MW • or • EMW = Total Press. /(0.052*TVDint)

  5. Equivalent Mud Weight • Examples: • KWM • ECD - Equivalent Circulating Density • ECD = Ann. Fric./(0.052*TVD)+OWM • Frac gradient • Pore pressure, etc

  6. Casing Seat Tests • We test casing seats to: • Determine max pressure that formation can withstand • Determine if we have a good cement job

  7. Casing Seat Tests • LOT - Leak-Off Test • Measure the fracture pressure at casing seat • or, Maximum pressure the formation can withstand prior to fracture Fracture Initiation Pressure Leak-Off Fracture Extension Casing Test Volume pumped

  8. Casing Seat Tests • PIT - Pressure Integrity Test (FIT) • Determine if the casing seat can withstand a pre-determined pressure • Test Pressure = (EMW-MW)*0.052*TVDcasing seat

  9. Kick Tolerance • Maximum Casing Pressure - MCP • Maximum Allowable Annular Surface Pressure - MAASP, MASP • Maximum Casing pressure that the formation can withstand prior to fracture • = (EMW-MW)*0.052*TVDcasing seat

  10. Kick Tolerance • Maximum ppg kick - Maximum mud weight increase on a kick prior to formation fracture • =(EMW-MW)*TVDshoe/TVDwell • Assumes zero pit gain

  11. Kick Tolerance • Maximum Kick Volume

  12. Kick Types • Gas Kicks • Rapid expansion as gas circulated through choke • Mud gas separators and flare lines used • Gas migration problems • Higher SICP than others

  13. Kick Types • Gas Kicks, cont. • Barite settling in OB mud • Solubility of gas masks kick indicators • Flammability of gas • Slugging of gas at choke

  14. Kick Types • Oil Kicks • Flammable but not as explosive as gas • Density greater than gas-lower SICP • Very little expansion as kick reaches surface • But, there is almost always some gas present

  15. Kick Types • Water kicks • not flammable • very little expansion • lower SICP than gas or oil • But, there is still usually some gas present.

  16. Kick Types • Prediction kick types • Density of gas =1-2 ppg • Density of oil = 6-8 ppg • Density of salt water =8.6-9.0 ppg

  17. Drillers Method • Pressure at Top of Kick-Px

  18. Drillers Method • Surface Casing Pressure - CP • CP=Px-0.052*MW*x • Pressure at casing seat - Pseat • Pseat=CP+0.052*MW*Dseat • where the bubble is below the casing seat • Pseat=PB-0.052*MW*(D-Dseat) • where the bubble is above the casing seat

  19. Wait & Weight Method • Pressure at Top of Kick-Px

  20. Wait & Weight Method • Surface Casing Pressure - CP • CP=Px-0.052*MW*x • Pressure at casing seat - Pseat • Pseat=CP+0.052*MW*Dseat • where the bubble is below the casing seat • Pseat=PB-(0.052*MW*D’) • -[0.052*MW1*(D-D’-DSEAT)] • where the bubble is above the casing seat

  21. Nomenclature

  22. Examples

  23. Surface Casing Pressure

  24. Ann. Press @ Various Depths

  25. Boyle’s Law PV=constant Charles’ Law V/T=constant Avagadro’s Law PV=nRT Real Gas Law PV=ZnRT PV/ZT = nR P1*V1=P2*V2 Z1*T1 Z2*T2 V2 = P1*V1*Z2*T2 P2*Z1*T1 Reaction of Gas in a Wellbore

  26. Reaction of Gas in a Wellbore • Circulating gas from wellbore • Given: • Depth =16,000’ • BHT =300oF • BHP =12480 psi • MW =15.0 ppg • Surf. Temp =140oF • Drilled up 1 cu.ft. of gas

  27. Reaction of Gas in Wellbore

  28. Reaction of Gas in Wellbore

  29. Gas Migration

  30. Gas Migration MASP

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