Research On Mechanism Of Crosslinked Emulsified Fracturing Fluid Filtration Reducing And Rock Stability

Hailar Basin is the biggest petroliferous basin which is outside Songliao basin and belonging to Daqing region. With the process of exploration and development, it become the new supplier for Daqing Oilfield keeping 50 million tons output. There are 3813×104 tons reserves can be controled and the proven reserves are 3324×104 tons, but the difficulties of hydraulic fracturing in tuffaceous rocks of Xing'anling Group reservoirs are high water sensitivity of rock and early screen-out of hydraulic fracturing, so fracturing often fail. Therefore, we studied the initial crack and crack extension of tuffaceous reservoir, starting with characteristics of rock mechanics, mineralogy and rock hydrolization. We also applied emulsified fracturing fluid systems to improve the compatibility by reducing filtration and increasing stability. All stimulations go on smoothly and always achieve better production.The purpose of this research is to develop the crosslinked emulsified fracturing fluid system by studying the ability of filtration reducing and the stability of rock, which is lower cost and better effect .According to the actual conditions of Xing'anling Group Reservoir of Hailar Oil Field we studied the ability of filtration reducing and the stability of rock to reduce the cost of crosslinked emulsified fracturing fluid. The results of laboratory experiment were as follows:1. As oil-in-water emulsified fracturing fluid was crosslinked, emulsion viscosity and the fluidity changed macroscopically, but microcosmicly clusters were dispersed into individual oil droplet. This showed that the oil in crosslinked emulsified fracturing fluid were homogeneously dispersed into the water, with the emulsion viscosity increasing and the fluidity reducing, the system became more stable, which led to oil and water uniformly fluid to the reservoir , so the filtration was reduced.2. The research of film forming mechanism of oil-in-water emulsified fracturing fluid indicated that the rock had no membrane internally, only the fracturing fluid film in the rock surface, so that fracturing fluid filtration performance reduced.3. Through studying thickening effect and comparing the filtration property before and after crosslinked, static filtration experiment indicated the filtration reduced significantly after crosslinked. Therefore, lower fracturing fluid filtration was due to viscosity increase of crosslinked emulsified fracturing fluid.4. The research indicated that the seepage velocity of two-phase flow was lower than single-phase flow , along with the resistance effect of Jiamin effect, the fracturing fluid filtration was reduced effectively.5. The research of rock stability indicated that by adding a number of quaternary ammonium salt, neutralization and adsorption made the dilatability and disintegration of clay restrained, thereby, the rock was more stable. It was the remarkable ability of crosslinked emulsified fracturing fluid that ensured the fracturing success in Xing'anling Group Reservoirs.