Stability Analysis of Cavern Collapse in Fractured-Cavity Oil Reservoirs

Yanzhi Ding, Qiangyong Zhang (), Wen Xiang, Bin Wang, Xinrui Lyu and Longyun Zhang
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Yanzhi Ding: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan 250100, China
Qiangyong Zhang: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan 250100, China
Wen Xiang: School of Civil Engineering, Shandong University, Jinan 250100, China
Bin Wang: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan 250100, China
Xinrui Lyu: Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
Longyun Zhang: Logistics Department, Shandong University, Jinan 250100, China

Sustainability, 2023, vol. 15, issue 8, 1-18

Abstract: Fractured-vuggy oil reservoirs, with the decrease of formation pressure during the exploitation process, lead to the collapse of caverns or the closure of sizeable fractured oil channels, which seriously affects oil well production and the recovery rate of oil reservoirs. True three-dimensional geomechanical model tests were carried out to avoid the impact of cave collapse and fracture closure on oil well production. Taking the Tahe Oilfield in Xinjiang area of China as the engineering background, we researched the collapse failure mechanism of the karstic caves in fractured-cavity oil reservoirs and the evolution of fracture closure through a true three-dimensional geomechanical model test and the numerical simulation software RFPA. The collapse failure modes of caverns with and without prefabricated cracks were revealed, along with the displacement and stress changes during cave collapse and the mechanism of cave collapse failure. Our study revealed the mechanism of the interaction between cracks and the cave. The research results show that prefabricated cracks reduce the roof of the cave’s bearing capacity, making the karst cave collapse with incomplete cracks. The impact of the collapse is much smaller than the cavern without prefabricated cracks. The crack closure extends from the near end to the far end. The research results will provide necessary theoretical support for the large-scale safe extraction of deep petroleum resources, increase oil production in China, and have important theoretical significance and engineering application value.

Keywords: geomechanical model test; numerical simulation; caves in fractured-cavity oil reservoirs (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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