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Petroleum Engineering 406

Petroleum Engineering 406

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Petroleum Engineering 406

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  1. Petroleum Engineering 406 Lesson 4 Well Control

  2. Read • Well Control Manual • Chapter 9 • Homework 2 Due Feb. 3, 1999

  3. Content • Development of Abnormal Pressure • Properties of Normally Pressured Formations • Properties of Abnormally Pressured Formations • Casing Seat Selection

  4. 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

  5. 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

  6. Normally Pressured Formation Fluids Squeezed out with compaction

  7. Abnormal Formation Pressures • Due to: • Incomplete compaction • Diagenesis • Differential Density in Dipping Formations • Fluid Migration • Tectonic Movement • Aquifers • Thermal Effects

  8. Incomplete compaction Fluids trapped in place Fluids begin to support overburden

  9. 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

  10. Differential Density in Dipping Formations

  11. Fluid Migration

  12. Tectonic Movement - Uplifting

  13. Tectonic Movement - Faulting

  14. Aquifers

  15. Thermal Effects • Theories • Increased temperature with depth and chemical reactions cause increased pressures • Increased pressures caused increased temperatures

  16. Salt Formations Pressure Gradient Depth Pore press. gradient Overburden gradient Salt formation

  17. 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.

  18. 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.

  19. 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

  20. 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

  21. Porosity Density Conductivity Sonic Shale Density

  22. Temperature gradient - Increases Depth Normal Trend Top of Geo-pressure Temperature

  23. Pore Pressure Prediction Occurs: • Prior to drilling • During drilling • After drilling

  24. Before Drilling • Offset mud records, drilling reports, bit records, well tests • Geological Correlation

  25. Before Drilling • Open Hole Logs from offset wells

  26. Before Drilling • Seismic data

  27. During Drilling • Kick - SIDPP and HSP in DP can give accurate measurement of formation pore pressure • LOT - gives accurate measurement of fracture pressure

  28. Correlation of penetration rate to offset logs Changes in shale penetration rate During Drilling

  29. 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)

  30. During Drilling • Shale density Change - Density column

  31. During Drilling • Mud gas content change

  32. During drilling • Shale cutting change

  33. During Drilling • Mud chloride change • Increase in fill on bottom • Increase in drag or torque • Contaminated mud • Temperature change

  34. During Drilling • Abnormal trip fill-up behavior • Periodic logging runs • Drill-stem tests • MWD or LWD tools • Paleontology

  35. 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

  36. During Drilling d-exponent and dc-exponent

  37. During Drilling

  38. After Drilling • Log evaluation • Flow tests • BHP surveys • Shut-in pressure tests • Analysis of mud reports, drilling reports, and bit records