分段压裂用可溶球的研制

水平井分段压裂是包括页岩气在内的致密储层增产改造的主要技术措施,而目前主流的分段压裂工具中,水平井裸眼分段工具、套管滑套分段工具及大通径桥塞等都需要投球去打开分段滑套或暂时堵塞通道,投入管柱内的球也需要通过钻磨成碎屑才能排出管柱,其作业既费时又有风险。为此,根据现场需要,采用氢还原包覆技术先制备可溶球复合金属材料粉体,再通过粉末冶金法研制了金属基可溶性压裂球,并完成了室内模拟实验可溶解压裂球密度为1.8~2.0 g/cm~3,耐温150℃,抗压强度可达70MPa以上:应用现场压裂返排液浸泡考察其在规定时间下的溶解速度,一般溶解时间为10 d;模拟了目前分段压裂的井下环境(温度、压力)下压裂球的承压能力。结论认为,所研制的可溶解压裂球的承压性能和溶解性能能满足目前的分段压裂井下环境的需要,应根据溶解环境的不同来调整溶解速度。其免钻特性为水平井压裂工艺技术的发展提供了新的技术途径。

Research and development of soluble ball for staged fracturing

Horizontalwell staged fracturing is a main stimulation method for tight reservoirs (including shale gas reservoirs). At present, the staged fracturing tools include mainly horizontal-well open hole staged tools, sliding sleeve staged tools and large-bore bridge plugs. When they are put into operation, it is necessary to drop balls to open the sliding sleeve or the temporarily-plugged channel. However, the balls inside the pipe strings cannot be drained out until they are drilled and milled into fragments, and this process is hazardous and long. According to field requirements, the composite metal powder for soluble balls was prepared by means of hydrogen reduction coating technology. Then, metal-based soluble fracturing ball was developed by using the powder metallurgy and tested in lab simulation experiments. The soluble fracturing ball has a density of 1.8–2.0 g/cm³, temperature resistance of 150℃ and compressive resistance over 70 MPa. The dissolving rate of soluble fracturing balls in the stipulated period (generally 10 days) was investigated after being soaked in the fracturing flowback fluid which is applied in field. Finally, the pressure resistance of fracturing balls was simulated at downhole pressure and temperature of current staged fracturing. It is concluded that the soluble fracturing ball developed in this paper can meet the requirements of the downhole environment of current staged fracturing wells in terms of pressure resistance and solubility. And the dissolving rate should be adjusted according to the dissolution environment. This soluble fracturing ball can be drained out without being milled, so this research provides a new idea for the development of horizontal-well fracturing technologies.