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Difference between revisions of "Pore pressure prediction using seismic"

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Revision as of 11:52, 17 September 2013

Drilling engineers require estimates of the fluid pressures that they are likely to encounter in any given well to anticipate mud weights required to maintain optimal drilling rates and safety. In addition, the locations of anomalous pore-pressure regions are of interest in exploration because they often:

  • Correlate with highly productive “sweet” spots in otherwise tight gas sands;[1]
  • Provide constraints on basin evolution;[2][3]
  • May correspond to density of open fractures, including bedding-plane fractures.[4]

Seismic velocities for pore pressure prediction

Because seismic velocities correlate with effective pressure in the formation, sufficiently precise estimates of velocity obtained from seismic observations can be used to determine pore pressure. In the absence of dense well control, interval velocities derived from stacking velocities are used to estimate pore pressure. These interval velocities are compared with a general trend of velocities in the region (Fig. 1), and a pore pressure volume is developed for use by drilling engineers,[5][6][7][8] as shown in Fig. 2. Acoustic impedance volumes obtained from seismic trace inversion can also be used to identify and detect anomalous pore pressure regions. In any case, calibration to local velocity-pressure profiles is required. Without this calibration, the pore-pressure indicator is relative rather than absolute, although some empirical relationships exist.[9] The resolution of pore-pressure volumes obtained from seismic interval velocities is fairly coarse, compared to velocities used in detailed migration or tomography, which are somewhat more detailed, as shown by the example in Fig. 3. To meet the need for fine-scale predictions of pore-pressure ahead of the bit, new or improved methods for obtaining reverse VSP data, using the drill bit as a seismic source, and VSP data that uses logging-while-drilling techniques are being developed.[10][11][12]

References

  1. Surdam, R.C., Iverson, W., and Jiao, Z. 1996. Natural Gas Resource Characterization Study of the Mesaverde Group in the Greater Green River Basin, Wyoming: A Strategic Plan for the Exploitation of Tight Gas Sands. Final report, Contract No. GRI 96/0220, Gas Research Inst., Chicago.
  2. Osborne, M.J. and Swarbrick, M.E. 1997. Mechanisms for Generating Overpressure in Sedimentary Basins: A Re-evaluation. AAPG Bull. 81 (6): 1023.
  3. Japsen, P. 1998. Regional Velocity-Depth Anomalies, North Sea Chalk: A Record of Overpressure and Neogene Uplift and Erosion. AAPG Bull. 82 (11): 2031.
  4. Pisetski, V.B. 1999. The Dynamic Fluid Method: Extracting Stress Data from the Seismic Signal Adds a New Dimension to Our Search. The Leading Edge 18 (9): 1084.
  5. Kan, T-K., Kilsdonk, B., and West, C.L. 1999. 3D Geopressure Analysis in the Deepwater Gulf of Mexico. The Leading Edge 18 (4): 502.
  6. 6.0 6.1 6.2 Sayers, C.M., Johnson, G.M., and Denyer, G. 2000. Predrill Pore Pressure Prediction Using Seismic Data. Presented at the IADC/SPE Drilling Conference, New Orleans, Louisiana, 23-25 February 2000. SPE-59122-MS. http://dx.doi.org/10.2118/59122-MS.
  7. Dutta, N., Gelinsky, S., Reese, M. et al. 2001. A New Petrophysically Constrained Predrill Pore Pressure Prediction Method for the Deepwater Gulf of Mexico: A Real-Time Case Study. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September–3 October. SPE-71347-MS. http://dx.doi.org/10.2118/71347-MS.
  8. 8.0 8.1 Huffman, A.R. 2001. The Future of Pore-Pressure Prediction Using Geophysical Methods. Presented at the Offshore Technology Conference, Houston, Texas, 30 April-3 May. OTC-13041-MS. http://dx.doi.org/10.4043/13041-MS.
  9. Eaton, B.A. 1975. The Equation for Geopressure Prediction from Well Logs. Presented at the Fall Meeting of the Society of Petroleum Engineers of AIME, Dallas, 28 September–1 October. SPE 5544. http://dx.doi.org/10.2118/5544-MS.
  10. Miranda, F. et al. 1996. Impact of Seismic ‘While Drilling’ Technique on Exploration Wells. First Break 14 (2): 55.
  11. Kulkarni, R., Meyer, J.H., and Sixta, D. 1999. Are Pore-Pressure Related Drilling Problems Predictable? The Value of Using Seismic Before and while Drilling. Paper presented at the 1999 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Houston, 31 October–5 November.
  12. Underhill, W., Esmersoy, C., Hawthorn, A. et al. 2001. Demonstrations of Real-Time Borehole Seismic From an LWD Tool. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September-3 October. SPE-71365-MS. http://dx.doi.org/10.2118/71365-MS.

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See also

Subsurface stress and pore pressure

Methods to determine pore pressure

Pore pressure prediction using acoustic logging

Pore fluid effects on rock mechanics

PEH: Geomechanics Applied to Drilling Engineering

PEH:Reservoir Geophysics