China Petroleum Exploration ›› 2024, Vol. 29 ›› Issue (5): 136-147.DOI: 10.3969/j.issn.1672-7703.2024.05.011

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Technology and result evaluation of well cementing sliding sleeve single-cluster hole fracturing for continental shale oil reservoir

Zhao Xianzheng1,Jin Fengming2,Chen Changwei2,Jiang Wenya2,Han Wenzhong2,Liu Xuewei2,Tang Jizhou3,Xu Jing2,Chai Gongquan2,Zhang Shilin4,Sheng Mao5,Yin Qiwu2   

  1. 1 CNPC Consulting Center; 2 PetroChina Dagang Oilfield Company; 3 Tongji University; 4 CNPC Bohai Drilling Engineering Co., Ltd.;5 China University of Petroleum (Beijing)
  • Online:2024-09-14 Published:2024-09-14

Abstract: In Cangdong Sag in Bohai Bay Basin, the continental shale in the second member of Kongdian Formation (Kong 2 member) has great variation in lithology and high heterogeneity, and shale oil production of horizontal wells is significantly different by applying traditional fracturing technologies. In view of these problems, core section with a length of 500 m in Well G108-8 has finely been described, and well cementing sliding sleeve fracturing technological test in Well GY5-1-9H and comparative fracturing simulation experiments between multicluster hole and single-cluster hole have been conducted, which enable to summarize the adaptability, mechanism, and fracturing construction experience of single-cluster fracturing technology for continental shale oil in fault basins. The study results show that the uniformity of fracture initiation by using well cementing sliding sleeve single-cluster hole fracturing has significantly been improved by 1.65-2.04 times compared to bridge plug multi-cluster hole fracturing, overcoming the failure of fracture opening in some clusters due to competitive fracture initiation, as well as problems of casing deformation caused by fluid fingering advance and frac-hit in some clusters. The process of bridge plug pumping and perforation is eliminated when applying well cementing sliding sleeve single-cluster hole fracturing technology, so the construction process is more continuous. A maximum of 11 stages of fracturing construction have continuously been operated in one day, with a construction pressure reduction of 20%–30%, and the number of fracturing trucks decreased from 20 to 9. In Well GY5-1-9H, this technology has been applied to implement single-cluster hole fracturing for 79 stages and 987 m, with a sliding sleeve spacing (cluster hole spacing) of 12.5 m. After fracturing, the cumulative oil production in the first year was 10128 t, and the predicted ultimate recoverable reserves (EUR) were 3.77×104 t, setting a record for the highest cumulative oil production and single well EUR of the normalized per kilometer section in shale oil horizontal well in China, which was 1.34-3.15 times that of multi-cluster hole fracturing wells in the same oil enrichment zone; It has also been applied in Shulu Sag in Jizhong Depression, and the steady pressure and production have been achieved in shale oil horizontal wells for over 300 days. This technology delivers useful reference for the development of highly homogeneous continental shale oil in China.

Key words: well cementing sliding sleeve, single-cluster hole fracturing, shale oil, horizontal well, fault basin

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