体积压裂裂缝前端粉砂分布规律试验研究

Experimental Study on Silt Distribution Law at the Front end of Fractures in Volume Fracturing

张衍君 葛洪魁 徐田录 黄文强 曾会 陈浩

ZHANG Yanjun GE Hongkui XU Tianlu HUANG Wenqiang ZENG Hui CHEN Hao

中国石油大学（北京）非常规油气科学技术研究院，北京 102249 中国石油新疆油田分公司吉庆油田作业区，新疆吉木萨尔 831700 成都理工大学能源学院，四川成都 610059

Unconventional Oil and Gas Science and Technology Institute, China University of Petroleum (Beijing), Beijing, 102249, China Jiqing Oilfield Region of PetroChina Xinjiang Oilfield Company, Jimusar, Xinjiang, 831700, China College of Energy, Chengdu University of Technology, Chengdu, Sichuan, 610059, China

粉砂在致密储层体积压裂中的作用尚未明确，其在裂缝前端的分布规律仍不清楚。为此，建立了利用动态滤失分析仪评价体积压裂裂缝（文中简写为“体积裂缝”）前端粉砂分布情况的模拟试验方法，在描述缝面形貌的基础上研究了粉砂的分布规律及影响因素。试验发现，携砂液在体积裂缝中逐渐滤失，滤失达到平衡后滞留在缝端的粉砂其分布差异很大；同时，随着滤失时间增长缝内压力逐渐升高，后达到稳定状态。最长运移距离和稳定压力能合理表征粉砂在裂缝前端的分布特征。缝端开度增大、缝面粗糙度减小、压裂液黏度升高，粉砂最长运移距离增加；粉砂粒度越小，最长运移距离越大。缝端开度越小、缝面粗糙度越大、黏度越高、粉砂粒度越小，缝内稳定压力越高。研究结果表明，压裂施工时添加粉砂能够封堵裂缝前端，提高缝内压力，抑制裂缝在某一方向过快增长，增加缝网复杂度。

The role of silt in volume fracturing of tight reservoirs is not yet clear, and so it is with its distribution law at the front end of the fracture. For this reason, a dynamic fluid loss analysis device was used to establish a simulation test method for the distribution of silt sand at the front end of volume fracturing fractures (hereinafter referred as “volume fractures”), and the distribution law and influencing factors of silt were studied on the basis of fracture surface morphology description. It is found by experiments that the sand-carrying fluid was gradually lost in the volume fractures, and the distribution of silt retained at the fracture front end was largely distinct after the fluid loss reached equilibrium. Meanwhile, the pressure in the fractures was gradually elevated and then became stable as the fluid loss continued. The distribution of silt at the front end of fractures can be reasonably characterized by the maximum transport distance and stable pressure. The maximum transport distance increases with widening aperture of the fracture front end, lowering roughness of fracture surfaces, and increasing fracturing fluid viscosity. Small particle size of silt also increases the maximum transport distance. In addition, the stable pressure in the fractures increases as the aperture of fracture front end decreases, the roughness of fracture surfaces increases, the fracturing fluid viscosity increases, and the particle size of silt decreases. The results demonstrate the addition of silt during fracturing can raise the pressure in fractures after plugging their front ends and restrain the fractures from growing too fast in a certain direction, thereby increasing the complexity of the fracture network.

国家科技重大专项项目“延安地区陆相页岩气勘探开发关键技术”课题4“非均质陆相页岩气储层改造配套工艺技术”（编号：2017ZX05039-004）资助

https://doi.org/10.11911/syztjs.2021065