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*TVD int )+MW –or EMW = Total Press. /(0.052*TVD int )

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 Volume pumped PressurePressure Leak-Off Fracture Initiation Fracture Extension Casing Test

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

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

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

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 = ppg

Drillers Method Pressure at Top of Kick-P x

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

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

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

Nomenclature

Examples

Surface Casing Pressure

Ann. Various Depths

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

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

Reaction of Gas in Wellbore

Gas Migration

MASP