自支撑相变压裂技术室内研究与现场应用

为了解决常规水力压裂普遍存在的砂堵、残渣伤害、设备磨损、裂缝远端难以得到有效支撑等问题，提出了一种自支撑相变压裂技术，即：向储层注入由相变流体和非相变流体组成的相变压裂液体系，在地层温度的刺激下，相变流体发生相变，由液体变为固体的相变支撑剂颗粒从而支撑水力裂缝，而非相变流体占据的空间在其返排后则成为油气高速流动的通道；在此基础上，进行了材料性能评价、工艺参数优化和现场应用。研究结果表明：①在30 ℃下，相变压裂液体系是一种无固相的液体，流动性好，随着温度的升高，逐渐生成相变支撑剂颗粒；②相变流体相变时间可调，能够适合不同温度的储层；③在不同配方、不同剪切速度条件下，相变压裂液体系能够形成粒径介于0.1～5.0 mm的相变支撑剂；④裂缝导流能力与粒径大小呈正比，导流能力优于石英砂和陶粒。现场应用效果表明，缝长及导流能力优化、注液排量设计、温度场模拟计算等配套手段进一步完善了自支撑相变压裂技术体系，能够有效地指导自支撑相变压裂现场实施。结论认为，现场应用的成功，验证了该项技术的可行性，可以为储层改造提供一种新的压裂技术。

Laboratory study and field application of self-propping phase-transition fracturing technology

Conventional hydraulic fracturing technology generally has the problems of sand plugging, residue damage, equipment wear and difficult effective propping at the far end of the fracture. In this paper, a kind of self-propping phase-transition fracturing technology (SPFT) is proposed to solve these problems. That is to inject the phase-transition fracturing fluid system (PFFS) composed of phase-transition fluid (PF) and non-phase-transition fluid (NPF) into the reservoir. Under the action of formation temperature, phase transition from liquid to solid of PF occurs, and chemical-phase-transition proppant (CP) particles are generated to prop the hydraulic fractures. After NPF flows back, its occupied space serves as a high-speed flow channel of oil and gas. Finally, material performance evaluation, technological parameter optimization and field application were carried out. And the following research results were obtained. First, at 30 ℃, PFFS is a kind of solid-free liquid with good fluidity. And with the increase of temperature, CP particles are formed gradually. Second, the phase transition time of PF is adjustable, so it is suitable for reservoirs with different temperatures. Third, PFFS can generate CP with a particle size of 0.1–5.0 mm under the conditions of different formulas and different shear speed. Fourth, the fracture conductivity is directly proportional to the particle size, and the conductivity of CP is higher than that of quartz sand and ceramsite. Field application results show that the supporting means (such as fracture length and conductivity optimization, injection rate design, and temperature field simulation and calculation) further improve the SPFT system and can provide effective guidance for the field application of self-propping phase-transition fracturing. In conclusion, the success of field application confirms the feasibility of SPFT and it can be used as a new fracturing technology for reservoir stimulation.