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Petroleum Engineering 406 Lesson 3 Well Control

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

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

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

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

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

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

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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*TVD casing seat

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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*TVD casing seat

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Kick Tolerance Maximum ppg kick - Maximum mud weight increase on a kick prior to formation fracture =(EMW-MW)*TVD shoe /TVD well Assumes zero pit gain

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Kick Tolerance Maximum Kick Volume

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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

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

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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

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

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Kick Types Prediction kick types –Density of gas =1-2 ppg –Density of oil = 6-8 ppg –Density of salt water = ppg

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Drillers Method Pressure at Top of Kick-P x

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Drillers Method Surface Casing Pressure - CP –CP=P x *MW*x Pressure at casing seat - P seat –P seat =CP+0.052*MW*D seat –where the bubble is below the casing seat –P seat =P B *MW*(D-D seat ) –where the bubble is above the casing seat

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Wait & Weight Method Pressure at Top of Kick-P x

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Wait & Weight Method Surface Casing Pressure - CP –CP=P x *MW*x Pressure at casing seat - P seat –P seat =CP+0.052*MW*D seat –where the bubble is below the casing seat –P seat =P B -(0.052*MW*D’) –-[0.052*MW 1 *(D-D’-D SEAT )] –where the bubble is above the casing seat

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Nomenclature

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Examples

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Surface Casing Pressure

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Ann. Various Depths

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Reaction of Gas in a Wellbore Boyle’s Law –PV=constant Charles’ Law –V/T=constant Avagadro’s Law –PV=nRT Real Gas Law –PV=ZnRT PV/ZT = nR P 1 *V 1 = P 2 *V 2 Z 1 *T 1 Z 2 *T 2 V 2 = P 1 *V 1 *Z 2 *T 2 P 2 *Z 1 *T 1

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

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Reaction of Gas in Wellbore

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Gas Migration

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MASP

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