petroleum engineering 406
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Petroleum Engineering 406. Lesson 4 Well Control. Read. Well Control Manual Chapter 9 Homework 2 Due Feb. 3, 1999. Content. Development of Abnormal Pressure Properties of Normally Pressured Formations Properties of Abnormally Pressured Formations Casing Seat Selection. - PowerPoint PPT PresentationTRANSCRIPT
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Petroleum Engineering 406
Lesson 4
Well Control
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Read
• Well Control Manual– Chapter 9
• Homework 2 Due Feb. 3, 1999
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Content
• Development of Abnormal Pressure
• Properties of Normally Pressured Formations
• Properties of Abnormally Pressured Formations
• Casing Seat Selection
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Knowledge of Pore and Fracture Pressures Leads to:
• More effective well planning
• Maximize penetration rates with balanced drilling
• Safer and more economical selection of casing points
• Minimize trouble due to lost circulation and kicks
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Knowledge of Pore and Fracture Pressures Leads to:
• Better engineered production and test equipment
• Better understanding of local geology and drilling hazards
• More accurate analysis of drilling data and electric logs
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Normally Pressured Formation
Fluids Squeezed out with compaction
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Abnormal Formation Pressures
• Due to:– Incomplete compaction– Diagenesis– Differential Density in Dipping Formations– Fluid Migration– Tectonic Movement– Aquifers– Thermal Effects
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Incomplete compaction
Fluids trapped in place
Fluids begin to support overburden
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Diagenesis
• At 200oF to 300oF Clays undergo chemical alteration. Montmorillonite clays dehydrate and release some of the bound water into the space already occupied by free water, increasing pressure
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Differential Density in Dipping Formations
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Fluid Migration
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Tectonic Movement - Uplifting
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Tectonic Movement - Faulting
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Aquifers
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Thermal Effects
• Theories– Increased temperature with depth and chemical
reactions cause increased pressures– Increased pressures caused increased
temperatures
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Salt Formations
Depth
Pressure Gradient
Pore press. gradient
Overburden gradient
Salt formation
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Shale Properties used to Predict Pore Pressures
• Shales are used because:– Most pressure transition zones occur in
relatively thick shales– Properties of clean shales are fairly
homogeneous at any depth, and can be predicted with some degree of accuracy.
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Shale Properties used to Predict Pore Pressures
• Shales are used because:– A deviation from the expected can be
interpreted as a change in pressure gradient– Detecting these deviations in low permeability
shales gives an early warning prior to drilling into pressured permeable formations, thus avoiding kicks.
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Normally Pressured Shales
• Porosity - Decreases with depth
• Density - Increases with depth
• Conductivity - Decreases with depth
• Resistivity - Increases with depth
• Sonic travel time - Decreases with depth
• Temp. gradient - Relatively constant
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Abnormally Pressured Shales
• Porosity - Higher than expected
• Density - Lower than expected
• Conductivity - Higher than expected
• Resistivity - Lower than expected
• Sonic travel time - Higher than expected
• Temp gradient - Increases
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Porosity Density Conductivity Sonic
Shale Density
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Temperature gradient - Increases
Depth
Temperature
Normal Trend
Top of Geo-pressure
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Pore Pressure Prediction Occurs:
• Prior to drilling
• During drilling
• After drilling
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Before Drilling
• Offset mud records, drilling reports, bit records, well tests
• Geological Correlation
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Before Drilling
• Open Hole Logs from offset wells
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Before Drilling
• Seismic data
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During Drilling
• Kick - SIDPP and HSP in DP can give accurate measurement of formation pore pressure
• LOT - gives accurate measurement of fracture pressure
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During Drilling
• Correlation of penetration rate to offset logs
• Changes in shale penetration rate
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During Drilling
• Shale density Change– Mercury pump– Mud balance
• Fill mud balance with clean shale until it balances at 8.33 ppg
• Fill the balance cup with water and determine total weight
• Calculate shale bulk density:– SBD=8.33/(16.66-Total Weight)
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During Drilling
• Shale density Change - Density column
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During Drilling
• Mud gas content change
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During drilling
• Shale cutting change
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During Drilling
• Mud chloride change
• Increase in fill on bottom
• Increase in drag or torque
• Contaminated mud
• Temperature change
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During Drilling
• Abnormal trip fill-up behavior
• Periodic logging runs
• Drill-stem tests
• MWD or LWD tools
• Paleontology
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During Drilling
• dc-exponent
– P=K*(W/D)d*Ne
• P=penetration rate of shale
• K=formation drillability
• W=weight on bit
• D=bit diameter
• N=rotary speed
• d=bit weight exponent
• e=rotary speed exponent
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During Drillingd-exponent and dc-exponent
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During Drilling
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After Drilling
• Log evaluation
• Flow tests
• BHP surveys
• Shut-in pressure tests
• Analysis of mud reports, drilling reports, and bit records