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This lesson delves into essential well control concepts in petroleum engineering, focusing on equivalent mud weights (EMW), casing seat tests, kick tolerance, and gas behavior in wellbores. You'll learn to calculate EMW, understand different kick types such as gas, oil, and water kicks, and the implications of kick tolerance. The lesson includes various methods like the Drillers and Wait & Weight methods, alongside important nomenclature from real gas laws. These principles are crucial for ensuring safety and efficiency in drilling operations.
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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 • 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)
Equivalent Mud Weight • Examples: • KWM • ECD - Equivalent Circulating Density • ECD = Ann. Fric./(0.052*TVD)+OWM • Frac gradient • Pore pressure, etc
Casing Seat Tests • We test casing seats to: • Determine max pressure that formation can withstand • Determine if we have a good cement job
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
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
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
Kick Tolerance • Maximum ppg kick - Maximum mud weight increase on a kick prior to formation fracture • =(EMW-MW)*TVDshoe/TVDwell • Assumes zero pit gain
Kick Tolerance • Maximum Kick Volume
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
Kick Types • Gas Kicks, cont. • Barite settling in OB mud • Solubility of gas masks kick indicators • Flammability of gas • Slugging of gas at choke
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
Kick Types • Water kicks • not flammable • very little expansion • lower SICP than gas or oil • But, there is still usually some gas present.
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
Drillers Method • Pressure at Top of Kick-Px
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
Wait & Weight Method • Pressure at Top of Kick-Px
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
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
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
Gas Migration MASP
