颗粒与纤维在水力裂缝内封堵机理的可视化实验研究  

Visualization study on the plugging mechanism of fibers and particulates in the hydraulic fracture

作　　者：刘颖 杨晨 史涛 LIU Ying;YANG Chen;SHI Tao(College of Water Resources,North China University of Water Resources and Electric Power,Zhengzhou 450045,China;School of Water Conservancy,North China University of Water Resources and Electric Power,Zhengzhou 450045,China;Development Department,Tarim Oilfield Company,PetroChina,Korla 841000,China)

机构地区：[1]华北水利水电大学水资源学院,郑州450046 [2]华北水利水电大学水利学院,郑州450046 [3]中国石油塔里木油田公司开发处,库尔勒841000

出　　处：《石油科学通报》2022年第2期196-203,共8页Petroleum Science Bulletin

基　　金：河南省高校科技创新人才支持计划(21HASTIT010);河南省重点研发与推广专项(202102310261);河南省高校青年骨干教师培养计划(2020GGJS093)联合资助。

摘　　要：水力压裂过程中为了提高缝网的复杂程度,常在压裂过程中注入可降解的纤维和颗粒,通过对已有裂缝的暂时封堵迫使新裂缝开启并在延伸过程中转向。但是由于目前对纤维与颗粒在水力裂缝内的封堵形成机理仍不明确,制约了暂堵转向压裂效果的进一步提升。因此,本文建立了水力裂缝内封堵的可视化实验系统,对纤维与颗粒在5 mm宽裂缝内的封堵过程进行了直接观测。实验发现封堵过程起始于纤维在裂缝壁面上的吸附,吸附的纤维不断聚集形成封堵带,封堵带膨胀到一定程度后开始捕捉流过的颗粒并填充到纤维的孔隙中,封堵带在扩张的同时变得均匀密实,从而加速了封堵形成过程,最终形成全面封堵。实验结果说明纤维开启了封堵过程,仅仅依靠2 mm粒径的颗粒是无法形成封堵的,但是颗粒可以在封堵后期大幅度加快封堵进程并承担缝内的压差,因此建议在实际的暂堵过程中应该先加入纤维,待到压力明显升高后再加入颗粒。最后,分别固定颗粒和纤维的浓度为1%,考察了另一组分浓度变化时5 mm宽裂缝中的封堵表现,发现封堵形成时间随着暂堵剂浓度的增加而减少,但是当纤维和颗粒的浓度高于1.0%时,其浓度的提高对封堵效率的影响变得十分有限。因此,综合考虑封堵效率和材料成本,对于5 mm宽的水力裂缝,颗粒和纤维的最优质量浓度建议均取为1.0%。To enhance the complexity of fracture networks during hydraulic fracturing,degradable fibers and particulates are often injected into the pre-existing fractures as diverters to form temporarily plugging,initiate new fractures and make them deflect during extension.However,the plugging mechanism of fibers and particulates in hydraulic fracture is still not clear,which restricts the further improvement of the effect of the diverting hydraulic fracturing.Therefore,a visualized experimental system was built in this paper to observe the plugging process in a 5 mm wide hydraulic fracture.Through the experiments,it was found that the plugging process starts from the attachment of fibers on fracture faces,then the attached fibers keep gathering to form plugged zones,the plugging zones capture the flowing particulates to fill into the pores between fibers,accelerate the plugging process and plug the fracture eventually.The results indicated that the fibers could initiate the plugging process,since the plugging can be formed not only by the 2 mm-diameter particulates.The particulates could accelerate the following plugging process and withstand the pressure difference by acting as the skeleton of the plugged zones.It was suggested that fibers should be injected into the hydraulic fracture first and the particulates should to be injected into the hydraulic fracture when the pressure rises obviously.Finally,the concentration of fibers and particulates were fixed as 1%separately,and the plugging performance in a 5 mm wide fracture was investigated when the concentration of another component changes.It was found that the plugging forming time decreased with the increase of the diverters’concentration.However,when the concentration of fiber or particulate is higher than 1.0%,the influence of the concentration on the plugging efficiency becomes very limited.Therefore,considering the plugging efficiency and material cost,it was recommended that the optimal mass concentration of particulates and fibers should be 1.0%for a width

关 键 词：纤维 颗粒 水力裂缝 封堵 可视化 

分 类 号：TE357.1[石油与天然气工程—油气田开发工程]