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韩文龙,李 勇,王 力,等. 柿庄北煤层气区块煤层压裂裂缝扩展规律及影响因素[J]. 煤炭科学技术,2024,52(S1):1−10. doi: 10.12438/cst.2023-0517
引用本文: 韩文龙,李 勇,王 力,等. 柿庄北煤层气区块煤层压裂裂缝扩展规律及影响因素[J]. 煤炭科学技术,2024,52(S1):1−10. doi: 10.12438/cst.2023-0517
HAN Wenlong,LI Yong,WANG Li,et al. Fracturing fracture propagation law of coal seam and its influencing factors in the Shizhuang North Block[J]. Coal Science and Technology,2024,52(S1):1−10. doi: 10.12438/cst.2023-0517
Citation: HAN Wenlong,LI Yong,WANG Li,et al. Fracturing fracture propagation law of coal seam and its influencing factors in the Shizhuang North Block[J]. Coal Science and Technology,2024,52(S1):1−10. doi: 10.12438/cst.2023-0517

柿庄北煤层气区块煤层压裂裂缝扩展规律及影响因素

Fracturing fracture propagation law of coal seam and its influencing factors in the Shizhuang North Block

  • 摘要: 揭示煤层气储层压裂裂缝扩展规律及影响因素,对于制定压裂工艺及高效开发煤层气资源具有重要的意义。利用沁水盆地柿庄北煤层气区块的钻井取心、测井、井下节理观测、压裂施工及微震监测等数据,系统分析了水力压裂裂缝扩展规律及影响因素。研究结果表明,研究区主要采用清水压裂液,压裂施工曲线可分划为上升型、下降型、平稳型和波动型4类;微震监测表明压裂裂缝走向主要在37°~55°和42°~70°,压裂裂缝网络长度范围在69.5~157.5 m,宽度在35~68.5 m。I型地应力(σv>σH>σh)状态下,压裂裂缝容易沿着垂向扩展,多数压裂曲线为下降型或稳定型;II型地应力(σH>σv>σh)状态下,压裂裂缝扩展方向相对单一,多数为单一形状的垂直裂缝,裂缝网络宽度较小;III型地应力(σH>σh>σv)状态下,压裂裂缝沿水平方向扩展,裂缝形态复杂。侧压系数λ与压裂裂缝网络长度呈正相关关系,与宽度呈负相关,若λ大于0.3,压裂裂缝网络长度常大于90 m。压裂裂缝扩展到节理(裂隙)时能够出现穿越、沟通和俘获3种类型;其中沟通型压裂效果较好,多数煤层气井具有高产稳产的特点;穿越型的压裂裂缝延展长度有限,俘获型的压裂裂缝多数与节理(裂隙)重合,这2类压裂井的产气效果较差。随着原生+碎裂结构煤占比的增大,压裂裂缝网络长度逐渐增大,宽度逐渐减小;当原生+碎裂结构煤厚度占比小于40%,压裂裂缝网络长度难以超过110 m。上述成果可为煤层压裂改造提供理论基础及地质保障。

     

    Abstract: It is of great significance to reveal the law of fracturing fracture propagation and influencing factors in coalbed methane (CBM) reservoirs for the formulation of fracturing technology and the efficient development of CBM resources. In this paper, the data of core drilling, well logging, downhole observation, fracturing construction and microseismic monitoring in Shizhuangbei CBM block, Qinshui Basin, China, are used to systematically analyze the hydraulic fracturing fracture propagation law and influencing factors. The research results show that clean water fracturing fluid is mainly used in the study area. According to the change in construction pressure, the fracture curves can be divided into four types: descending, stable, ascending, and fluctuating. Hydraulic fracture strikes are mainly N37°–55°W and N42°–70°E, with lengths varying between 69.5 and 157.5 m and heights of 35 to 68.5 m. In the type I stress state(σv>σH>σh), the fracturing fractures tend to expand vertically, and most fracturing curves are descending or stable. In the type II in-situ stress state(σH>σh>σv), the propagation direction of fracturing fractures is relatively single, and most of them are vertical fractures of a single shape. The width of the fracture network is small. Under the type III in-situ stress state(σH>σv>σh), the fracturing fractures expand along the horizontal direction, and the fracturing fractures have more complex shapes. The principal stress difference coefficient (λ)is positively correlated with the length of the fracture network and negatively correlated with the width. For fracturing fracture lengths >90 m, the λ is higher than 0.3. The hydraulic fractures can be communicated, penetrated, or captured by natural fractures. The effect of communication fracturing is better, and most coalbed methane wells have the characteristics of high and stable production. The extension length of the penetrated fracturing fractures is limited, and most of the captured fracturing fractures overlap with joints. The gas production effect of penetrated and captured fracturing wells is poor. With the increase of the proportion of primary and cataclastic coal thickness, the length of the fracture network gradually increases and the width gradually decreases. For fracturing fracture lengths >110 m, the proportion of primary and cataclastic coal thickness is higher than 40%. The research results provide a theoretical basis and geological guarantee for coal seam fracturing reconstruction.

     

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