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Energy Storage Fracturing Based on a Slick-Water System in Tight Oil Reservoirs


The difficulty in fracture extension in a plastic formation and the strong water sensitivity caused by high sensitive minerals are one of the prevalent problems in tight oil reservoirs. It is important to take into account both a fracture effect and formation protection together.

In this study, a novel horizontal well energy-storage fracturing technology is proposed to improve the fracture effect. Energy-storage SRV fracturing is forming a fracture network system by the method of multi-segment fractured horizontal wells with large displacement and injection rates, combined with a new slick-water system (slick-water + gel) and a proppant technology. Wells are shut-in after fracturing to maintain reservoir energy. Water/oil replacement can improve the well production and the ultimate recovery of tight reservoirs. The slick-water system can reduce the pump liquid friction and oil-water interfacial tension, and prevent swelling, migration and plugging of clay minerals. Based on this slick-water system, an energy-storage fracturing technique improves fracture opening and replenish formation energy effectively. To be specific, complex network fractures can be generated by means of large displacement due to an increase in static pressure in fractures; porcelain granules of different sizes support main fractures and branch fractures with the injection of a large amount of liquid, thus improving the fracture conductivity.

The results show that a stable oil production reaches 5-8 t/d by energy-storage SRV fracturing in tight oil reservoirs. Compared with conventional fracturing (1.5-2 t/d), the oil production has been improved by more than 2.5 times. Chlorine in wells is presented earlier by the new slick-water system with the energy-storage SRV fracturing, and the flowback rate once starting to produce oil is low. It is beneficial for water-oil displacement and maintaining the reservoir energy. Guar gum concentration in this slick-water system reduces from 0.4%-0.5% to 0.3%-0.4%. The amount of chemicals is reduced greatly than in conventional fracturing. In this way, the gel is formed with lower damage and costs. In general, energy-storage SRV fracturing with this slick-water system keeps good balance between SRV fracturing and formation protection, which is more applicable in increasing oil production in tight oil reservoirs.