川东南二叠系龙潭组煤系储层压裂模拟与成缝特征

doi:10.3969/j.issn.1672-7703.2024.06.012

摘要/Abstract

摘要： 四川盆地东南部綦江地区二叠系龙潭组煤系储层正处于勘探初期，复杂岩性下的压裂品质及页岩、石灰岩和煤岩互层条件下水力压裂成缝特征尚不清晰，相关认识有待深化。针对上述问题，通过室内实验、压裂物理模拟及数值模拟手段研究了龙潭组煤系储层的压裂品质及水力压裂成缝特征。研究认为：不同区域龙潭组储层在纵向岩性、矿物组分、岩石力学参数及地应力参数方面的差异明显，整体上脆性矿物含量低、脆性差，不同岩性之间水平应力差达到2～6MPa，裂缝穿层难度大。物理模拟实验结果表明，由于岩性界面及应力差异系数的影响，龙潭组同时存在T 形缝、钝化缝及穿层缝3 种裂缝形态，但裂缝形态主要受岩性界面强度影响；数值模拟成缝特征显示，压裂排量、黏度及起裂位置对裂缝扩展形态影响明显，优选页岩及泥岩夹石灰岩、页岩层段进行压裂，同时确保排量在12m³/min及以上、压裂液黏度在25mPa·s 左右，有利于促进裂缝穿层扩体。

关键词: 四川盆地, 綦江地区, 龙潭组, 煤系地层, 压裂, 裂缝特征

Abstract: At present, it is in an early exploration stage of coal measure reservoir in the Permian Longtan Formation in Qijiang area, southeastern Sichuan Basin. There is a lack of clear understanding of fracturing quality of complex lithologies and fracture propagation characteristics of interbedding of shale, limestone, and coal rock, which needs to be further studied. In response to the above issues, experimental tests, fracturing physical simulation, and numerical simulation are conducted to analyze the fracturing quality and fracture propagation characteristics of Longtan Formation reservoir. The results show that there are significant differences in lithology, mineral composition, rock mechanical and in-situ stress parameters vertically of Longtan Formation reservoirs in various regions, and the reservoir is characterized by low brittle mineral content and poor brittleness as a whole, with the horizontal stress difference reaching up to 2–6 MPa between different rock types, making it difficult to propagate transverse fractures. The physical simulation result shows that due to the influence of lithologic boundary and stress difference coefficient, three types of fractures are observed in Longtan Formation, i.e., T-shaped fractures, passivation fractures, and transverse fractures, and the fracture pattern is mainly controlled by the strength of lithologic boundary. The numerical simulation of fracture propagation characteristics shows that the displacement, viscosity, and fracture initiation position have a significant influence on fracture propagation pattern. On this basis, the shale interval and mudstone interval intercalated with limestone and shale layers are optimally selected, and fracturing operation is implemented with a displacement of higher than 12 m³/min and a fracturing fluid viscosity of about 25 mPa·s to promote the transvers propagation of hydraulic fractures.

Key words: Sichuan Basin, Qijiang area, Longtan Formation, coal measure strata, hydraulic fracturing, fracture characteristics

中图分类号:

TE122.2

左罗, 张旭东, 陈作, 贾长贵, 孙海成, 李双明, 徐胜强. 川东南二叠系龙潭组煤系储层压裂模拟与成缝特征[J]. 中国石油勘探, 2024, 29(6): 157-169.

Zuo Luo, Zhang Xudong, Chen Zuo, Jia Changgui, Sun Haicheng, Li Shuangming, Xu Shengqiang. Fracturing simulation and fracture propagation characteristics of coal measure reservoirs in the Permian Longtan Formation in southeastern Sichuan Basin[J]. China Petroleum Exploration, 2024, 29(6): 157-169.

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