Study on the damage and control method of fracturing fluid to tight reservoir matrix

Abstract

Hydraulic fracturing technology is the most effective stimulation method to develop hydrocarbons in tight reservoirs, but the invading of fracturing fluid into the reservoir matrix often causes permeability damage, resulting in reducing the effectiveness of the stimulation treatments. Therefore, in this paper, for tight cores with permeability of 0.10 × 10−3μm2, 0.05 × 10−3μm2 and 0.01 × 10−3μm2, the damage laws were studied through flow experiments. The results are as follows: taking cores with the permeability of 0.05 × 10−3μm2 as an example, the damage rate of water-sensitivity damage, water-locking damage, and solid-phase damage were 12%, 10% and 9%, respectively, indicating that water-phase damage was the major damage; as the initial core permeability decreases, the water-sensitivity damage rate and water-locking damage rate increase, while the solid-phase damage rate decreases slightly, but the total damage rate increases. In addition, the control methods of liquid-phase damage caused by the invading fracturing fluid were studied, and the results are as follows: increasing the flowback volume is effective to control water-locking damage, but has no obvious effect to water-sensitivity damage; for polymer clay stabilizer, the relative molecular weight (when changing from 1 × 104 to 11 × 104) affect the effect of water-sensitivity damage (the permeability damage rate increased by 141% for cores with the permeability of 0.05 × 10−3μm2), indicating that the molecular weight of clay stabilizer should be fully considered; for surfactant-based cleanup additive, when the oil/water interfacial tension (IFT) was reduced from 1.26 mN/m to 0.26 mN/m, the core damage rates were reduced by 44%, 36% and 34%, respectively, indicating that the reduction of IFT was beneficial to water-locking damage control. This paper is useful for further studying the damage law of fracturing fluid to tight reservoir and the control method of water-phase damage, and provide some references for the efficient development of tight hydrocarbon resources.