Petroleum Engineering 406

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./(0.052TVDint)MW
• or
• EMW Total Press. /(0.052TVDint)

5
Equivalent Mud Weight

• Examples
• KWM
• ECD - Equivalent Circulating Density
• ECD Ann. Fric./(0.052TVD)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)0.052TVDcasing 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)0.052TVDcasing 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

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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

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

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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

15
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 8.6-9.0 ppg

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Drillers Method

• Pressure at Top of Kick-Px

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Drillers Method

• Surface Casing Pressure - CP
• CPPx-0.052MWx
• Pressure at casing seat - Pseat
• PseatCP0.052MWDseat
• where the bubble is below the casing seat
• PseatPB-0.052MW(D-Dseat)
• where the bubble is above the casing seat

19
Wait Weight Method

• Pressure at Top of Kick-Px

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Wait Weight Method

• Surface Casing Pressure - CP
• CPPx-0.052MWx
• Pressure at casing seat - Pseat
• PseatCP0.052MWDseat
• where the bubble is below the casing seat
• PseatPB-(0.052MWD)
• -0.052MW1(D-D-DSEAT)
• 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. Press _at_ Various Depths
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Reaction of Gas in a Wellbore

• Boyles Law
• PVconstant
• Charles Law
• V/Tconstant
• Avagadros Law
• PVnRT
• Real Gas Law
• PVZnRT

• PV/ZT nR
• P1V1 P2V2
• Z1T1 Z2T2
• V2 P1V1Z2T2
• P2Z1T1

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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

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Reaction of Gas in Wellbore
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Reaction of Gas in Wellbore
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Gas Migration
30
Gas Migration
MASP