Abstract
Hydraulic fracturing is an important technology for the stimulation of oil and gas reservoirs. Conventional fracturing technology based on “sand-carrying” faces some challenges such as sand plugs; incompatibility with the well completion method; damage to the reservoir caused by the incomplete gel-breaking of the fracturing fluid; solid proppants inefficiently turning the corner in complex fracture networks, and so on. In this paper, a novel self-generated proppant fracturing fluid system is proposed to solve the above problems caused by “sand-carrying”. The advantage of the fracturing fluid system is that in the whole process of fracturing, no solid proppants will be injected. The fracturing fluid itself will transform into solid proppants in the induced fractures under high temperatures to resist fracture closure stress. The fluid system consists of two kinds of liquids. One is the phase change liquid (PCL), which occurs as a liquid−solid phase change at high-formation temperatures to form a solid proppant. The other is the non-phase change liquid (NPCL), which controls the dispersity of the PCL in the two-phase fluid system. The main building block of the PCL is confirmed to be the bisphenol-A diglycidyl ether-type epoxy resin, whereas the NPCL is mainly composed of surfactants. The viscosity, phase-change temperature, and time of the fracturing fluid system are, respectively, about 30 mPa·s, 80 °C, and 20 min.