Moderate Collapse in a Shale Cap of a Nearly Depleted Reservoir

Kai Zhao, Jiyong Han, Liangbin Dou and Yongcun Feng
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Kai Zhao: College of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China
Jiyong Han: College of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China
Liangbin Dou: College of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China
Yongcun Feng: Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, Austin, TX 78712, USA

Energies, 2017, vol. 10, issue 11, 1-15

Abstract: Reservoir depletion will cause the safe equivalent circulation density ( ECD ) operating window of drilling fluids to narrow, or even disappear. Previous studies have proposed a set of two specific casings at the top and bottom of the depleted reservoir, respectively, or conducted wellbore strengthening to increase fracture pressure, but these will cause a waste of time and costs, or differential pressure sticking. Aiming at resolving this problem, a novel concept and evaluation method of moderate collapse in the shale cap was developed and case calculations were performed. The results show that the degree of collapse is different for wells drilled in different types of fault regimes, and it can be controlled by optimizing the well trajectory. The collapse pressure within the shale cap was decreased due to reservoir depletion, and when a certain degree of collapse was acceptable, the collapse pressure can be even lower and a safe operating window will appear which can be beneficial to optimizing the casing program and drilling design. The research results provide a theoretical basis and new design idea for successfully and economically drilling into new untapped reservoirs in deeper horizons through depleted zones in the future.

Keywords: reservoir depletion; moderate collapse; shale cap; safe operating window (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2017
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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