Pore-Pressure Estimation by Use of Mechanical Specific Energy and Drilling Efficiency
- Reza Majidi (BP) | Martin Albertin (BP) | Nigel Last (BP)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- June 2017
- Document Type
- Journal Paper
- 97 - 104
- 2017.Society of Petroleum Engineers
- MSE, Mechanical Specific Energy, Pore Pressure, d-exponent, Drilling Efficiency
- 11 in the last 30 days
- 838 since 2007
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Estimates of formation pore pressure before and while drilling are important inputs for well planning and operational decision making.
A method is proposed to determine pore pressure from a combination of downhole drilling-mechanics parameters and in-situ rock data with the concept of mechanical specific energy (MSE) and drilling efficiency (DE). This pore-pressure estimation method (termed DEMSE) is based on the theory that energy spent at the bit to remove a volume of rock is a function of in-situ rock strength and the differential pressure that the rock is subjected to during drilling.
A work flow is provided that illustrates the steps required to estimate pore pressure from drilling parameters and rock-mechanics data by use of the DEMSE method. Pore pressure estimated from the DEMSE method is compared with pore-pressure estimates derived through a conventional sonic log that is based on empirical technique for a deepwater well in the Gulf of Mexico (GOM). Pore-pressure estimates from the DEMSE method generally agree in magnitude and trend with the pore-pressure estimates derived from sonic-log data. The results of the DEMSE method have also been compared with pore-pressure estimates from the classical d-exponent (dXc) approach to highlight the advantages of DEMSE over traditional dXc methods.
Finally, the importance of using downhole vs. surface data for pore-pressure estimation purposes, specifically torque measurements at the bit, is illustrated through a field example. These findings suggest that downhole drilling-mechanics data, when properly used, can provide reliable independent estimates of pore pressure in real time at the bit and can be used for post-well-analysis to assist with constructing pore-pressure forecasts.
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