相变自生固相压裂液及施工工艺优化

常规水力压裂存在摩阻高、易砂堵、设备磨蚀、残渣伤害等难以避免的问题。针对上述问题，提出一种全新的相变自生固相压裂技术，即：向地层中注入由相变压裂液、非相变压裂液组成的自生固相压裂液体系。在地层温度条件下，相变压裂液通过相变由液态转变为固态，代替陶粒、石英砂等支撑剂，非相变压裂液占据的空间在其返排后形成具有高导流能力的流动通道。压裂液体系在水力裂缝内的流动形态、铺置长度、填充率受注入工艺影响较大，研究不同工艺下的自生固相压裂液体系流动形态、铺置长度、填充率，对提高该技术成功率具有重要意义。文章建立了一套自生固相压裂液体系流动分布数学模型，模拟不同工艺下的流动形态、铺置长度、填充率，模拟结果表明：相变压裂液形成的固体支撑剂能够有效支撑裂缝；随着注入液量的增加，相变压裂液前缘距离井眼越远；冻胶可以降低滤失量，形成更长的铺置长度和更高的填充率；顶替液不能过量，防止形成饺子状裂缝。

Optimization of Phase-transition in-situ Generated Solid-phase Chemical Fracturing Stimulation

Conventional hydraulic fracturing has some unavoidable problems, such as high friction, easy sand plugging, equipment abrasion and reservoir damage. In view of the above problems, a new fracturing technology, phase-transition insitu generated solid-phase chemical fracturing technology ( IGSCF) , is proposed. Inject insitu generated solid-phase chemical fracturing fluid system ( IGSCFF) consisting of phase-change fracturing fluid ( PCFF) and non-phase-change fracturing fluid ( NPCFF) into formation. Under formation temperature conditions, PCFF changes from liquid to solid through phase-transition, replacing ceramsite and quartz sand. The space occupied by NPCFF forms a high conductivity flow channel after it flows back. The flow pattern, placement distance and filling rate of IGSCFF in hydraulic fractures are greatly influenced by the injection schedule. It is important to study the flow pattern, placement distance and filling rate of IGSCFF under different schedules to improve the success rate of this technology. In this paper, a mathematical model of flow distribution of IGSCFF is established to simulate the flow pattern, placement distance and filling rate under different schedules. The simulation results show that the solid proppant formed by PCFF can effectively prop the fractures; with the increase of injection fluid volume, the farther the front of the PCFF is from the borehole; pre-pad can reduce the filtration volume, form a longer placement distance and a higher filling rate; displacement fluid can not be excessive to prevent the closing of fractures and formation of dumpling-shaped fractures.