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Oil Material Balance

Oil Material Balance. Outline:. Generation of Material balance equation. Havlena and Odeh Method. Reservoir Drive mechanism. Solution Gas Drive. Gas Cap Drive. Water Drive. Compaction Drive. Generation of Material Balance Equation. Generation of Material Balance Equation.

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Oil Material Balance

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  1. Oil Material Balance

  2. Outline: • Generation of Material balance equation. • Havlena and Odeh Method. • Reservoir Drive mechanism. • Solution Gas Drive. • Gas Cap Drive. • Water Drive. • Compaction Drive.

  3. Generation of Material Balance Equation

  4. Generation of Material Balance Equation

  5. Generation of Material Balance Equation • Expansion of oil plus originally dissolved gas. Liquid expansion: N(Bo-Boi) Liberated gas expansion: N(Rsi-Rs)Bg

  6. Generation of Material Balance Equation • Gas cap expansion:

  7. Generation of Material Balance Equation • Connate water expansion and pore volume reduction.

  8. Generation of Material Balance Equation

  9. Havlena and Odeh method

  10. Reservoir Drive Mechanisms • Solution gas drive • Gas cap drive • Water Drive • Compaction drive

  11. Solution gas Drive(above the bubble point)

  12. Exercise 1: • Determine the fractional oil recovery during depletion down to the bubble point for the following reservoir:

  13. Solution: • Average compressibility of the oil: • Fractional Recovery:

  14. Solution Gas Drive (below the bubble point) • Below the bubble point pressure gas will be liberated from the saturated oil. • Since gas compressibility is 2-3 times greater in order of magnitude, oil and water compressibility are usually neglected.

  15. Exercise 2: • The reservoir described in exercise 1 will be produced down to an abandonment pressure of 900 psi.

  16. Solution:

  17. Solution:

  18. Solution: • Conclusion: To increase the primary recovery as much as gas as possible should be kept in the reservoir.

  19. Gas Cap Drive • For a reservoir in which gas cap is the dominant drive mechanism and compaction and water influx are negligible material balance equation reduces to the following equation:

  20. Exercise 3: • The initial oil volume in a gas cap reservoir is estimated to be 115×10^6 stb. Np and cumulative gas oil ratio is provided in the following table. The size of the gas cap is uncertain and it is estimated to be m=0.4. Do you agree with this number?

  21. Solution: • Havlena and Odeh method is used. F , Eo and Eg are calculated in the following table.

  22. Solution:

  23. Solution: • If there is an uncertainty in the value of N, then the other form of Odeh equation can be applied to estimate both N and m.

  24. Natural Water Drive • A drop in the reservoir pressure due to the production of fluids cause the aquifer water to expand and flow into the reservoir. • High vertical permeability. • Steady state aquifer. • Unsteady state aquifer( time lag effect)

  25. Natural Water Drive • If there is no initial gas cap in reservoir and compaction effect is ignored:

  26. Natural Water Drive

  27. Compaction Drive • Withdrawal of liquid or gas from a reservoir results in fluid pressure reduction and consequently increase the grain pressure. • Reservoir will compact under higher grain pressure.

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