Li Jiayan, Zhang Kun, Cheng Ning, Xing Zhicheng, Wang Song, Wang Bin, Liang Tianbo
CNPC Engineering Technology Research Institute of Xinjiang Oilfield Company, Karamay 834000, China.
State Key Laboratory of Oil and Gas Resources and Prospecting, China University of Petroleum at Beijing, Beijing 102249, China.
ACS Omega. 2022 Feb 13;7(7):5921-5928. doi: 10.1021/acsomega.1c06140. eCollection 2022 Feb 22.
The upper Wuerhe formation in the Mahu-1 play is a tight conglomerate reservoir that has characteristics of low porosity and low permeability. During the early stage of field development, it has been noticed that horizontal wells typically have a high flowback ratio and an extremely low oil production rate during the early production, and this is likely attributed to the water-rock interaction that causes the closure of generated hydraulic fractures. In this study, a stabilizer and its dosage in a fracturing fluid are optimized, and its effect on clay antiswelling and rock stabilization is evaluated. Experimental results indicate that a mixture of a salt and an inorganic cationic polymer can effectively inhibit the water-rock reaction by minimizing the clay swelling and compressing the electric double layer on the rock surface. The antiswelling rate of montmorillonite can reach 93.56%, and that of the reservoir rock powder can reach 75.32%. Meanwhile, Brazilian splitting tests are conducted to evaluate the mechanical property change of reservoir rocks before and after being submerged in fracturing fluids with different stabilizers. Compared to 4% KCl, which is currently used in the field, the new formula can enhance the breakdown pressure by more than 10% without increasing the cost. The findings of this work provide a solution for fracturing water-sensitive reservoirs and also establish a set of laboratory methods for optimizing stabilizers as fracturing fluid additives.
玛湖1井区上乌尔禾组为致密砾岩油藏，具有低孔低渗特征。在油田开发早期，发现水平井投产初期返排率高但产油极低，这可能是由于水岩相互作用导致人工水力裂缝闭合所致。本研究对压裂液中的稳定剂及其加量进行了优化，并评价了其对黏土防膨和岩石稳定的作用。实验结果表明，盐与无机阳离子聚合物复配能通过抑制黏土膨胀、压缩岩石表面双电层，有效抑制水岩反应。蒙脱石防膨率可达93.56%，储层岩粉防膨率可达75.32%。同时，开展巴西劈裂试验，评价了不同稳定剂压裂液浸泡前后储层岩石力学性能变化。与现场目前使用的4%KCl相比，新配方在不增加成本的情况下，可使破裂压力提高10%以上。本研究成果为水敏性储层压裂提供了解决方案，也建立了一套优化稳定剂作为压裂液添加剂的室内方法。
