深层超深层页岩气水平井缝口暂堵压裂的裂缝调控模拟

Simulation of fracture control during fracture-opening temporary plugging fracturing of deep/ultra deep shale-gas horizontal wells

深层超深层页岩气井压裂时,受深部地层应力非均质性和“密簇”布缝的联合影响,多簇压裂中的水力裂缝难以同步起裂扩展,同时缝间强干扰作用加剧了裂缝非均衡延伸程度,矿场实践证实缝口暂堵压裂工艺可以有效调控多簇裂缝非均衡延伸,而构建深层超深层页岩气水平井缝口暂堵压裂裂缝调控模拟方法,可提高暂堵工艺实施效果。为此,基于岩石力学、弹性力学、流体力学和裂缝扩展理论、水平井分簇压裂中流量分配方程和暂堵球封堵方程,建立了深层超深层页岩气缝口暂堵压裂的裂缝扩展模型及调控模拟方法,并以中石化川东南丁山—东溪构造深层页岩气井为例,模拟了暂堵压裂中暂堵球数量、暂堵次数和时机对暂堵调控的影响,分析了暂堵球对裂缝扩展形态和SRV展布影响。研究结果表明:①缝口暂堵可以显著促进多簇裂缝均衡延伸,模拟证实暂堵球数量、暂堵次数和暂堵时机对裂缝调控具有重要作用;②随暂堵球数量增多,缝网体积先增大后减小,存在最优暂堵球数量;③当暂堵次数较多,可提高暂堵转向工艺容错率,但需要适量增多暂堵球数量;④当暂堵时机适当时,各簇裂缝均衡扩展,缝网体积达到最大值。结论认为,该暂堵裂缝调控模拟方法对完善暂堵压裂优化设计、提高矿场工艺实施水平,有效开发深层超深层页岩气具有重要意义。

When deep/ultra-deep shale gas well fracturing is carried out,multi-cluster fracturing can hardly realize synchronous initiation and propagation of hydraulic fractures due to the combined effects of heterogeneity of deep in-situ stress and"dense cluster"fracture arrangement,and the strong interference between fractures aggravates the unbalanced fracture propagation degree.Field practice proves that the fracture-opening temporary plugging fracturing technology can effectively control the unbalanced propagation of multiple fractures.In addition,the application effect of temporary plugging process can be improved by developing a method for simulating fracture control during fracture-opening temporary plugging fracturing of deep/ultra-deep shale-gas horizontal wells.Based on rock mechanics,elasticity mechanics,fluid mechanics and fracture propagation theory,combined with the flow distribution equation of horizontal-well multi-cluster fracturing and the plugging equation of temporary plugging balls,this paper establishes a fracture propagation model and a fracture control simulation method for the fracture-opening temporary plugging fracturing of deep/ultra-deep shale gas horizontal wells.Then,the influences of the number of temporary plugging balls and the times and timing of temporary plugging on temporary plugging control are simulated,and the influences of temporary plugging balls on fracture propagation morphology and SRV(stimulated reservoir volume)distribution are analyzed by taking Sinopec's one deep shale gas well in Dingshan-Dongxi structure of southeast Sichuan Basin as an example.And the following research results are obtained.First,fracture-opening temporary plugging can significantly promote the balanced propagation of multiple fractures,and the simulation confirms that the number of temporary plugging balls and the times and timing of temporary plugging play an important role in fracture control.Second,as the number of temporary plugging balls increase,the SRV increases firstly and then decreases,so there is an optimal number of temporary plugging balls.Third,increasing the times of temporary plugging can improve the fault tolerance rate of temporary plugging and diverting process,but it is necessary to increase the number of temporary plugging balls appropriately.Fourth,when the timing of temporary plugging is appropriate,the balanced propagation of multiple fractures is achieved and the maximum SRV is reached.In conclusion,this method is of great significance to optimizing the design of temporary plugging fracturing,improve the implementation level of field process and develop deep/ultra deep shale gas efficiently.