Study of the Wellbore Instability Mechanism of Shale in the Jidong Oilfield under the Action of Fluid

Xiaofeng Xu, Chunlai Chen, Yan Zhou, Junying Pan, Wei Song, Kuanliang Zhu, Changhao Wang () and Shibin Li
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Xiaofeng Xu: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Chunlai Chen: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Yan Zhou: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Junying Pan: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Wei Song: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Kuanliang Zhu: Institute of Drilling and Production Technology, Petro China Jidong Oilfield Company, Tangshan 063000, China
Changhao Wang: School of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China
Shibin Li: School of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China

Energies, 2023, vol. 16, issue 7, 1-12

Abstract: Wellbore instability is the primary technical problem that restricts the low-cost drilling of long-interval horizontal wells in the shale formation of the Jidong Oilfield. Based on the evaluation of the mineral composition, structure and physicochemical properties of shale, this paper investigates the mechanical behavior and instability characteristics of shale under fluid action by combining theoretical analysis, experimental evaluation and numerical simulation. Due to the existence of shale bedding and microcracks, the strength of shale deteriorates after soaking in drilling fluid. The conductivity of the weak surface of shale is much higher than that of the rock matrix. The penetration of drilling fluid into the formation along the weak surface directly reduces the strength of the structural surface of shale, which is prone to wellbore collapse. The collapse pressure of the shale formation in the Nanpu block of the Jidong oilfield was calculated. The well inclination angle, azimuth angle and drilling fluid soaking time were substituted in the deterioration model of rock mechanics parameters, and the safe drilling fluid density of the target layer was given. This work has important guiding significance for realizing wellbore stability and safe drilling of hard brittle shale in the Jidong Oilfield.

Keywords: wellbore stability; rock strength deterioration; shale formation; oil-based drilling fluid (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: 2023
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