Quantitative evaluation of the contribution of water-based fracturing fluids damage mechanism in tight sandstone reservoirs in the eastern margin of Ordos Basin

Water-based fracturing fluids usually lead to complex compound damages in tight sandstone reservoirs. Due to the lack of quantitative evaluation methods for the damage mechanism, there exists an unclear understanding of the main controlling factors of damages, which results in lack of precise scientific basis for the optimization of fracturing fluids. In order to quantify the contributions of different damage mechanisms, the tight sandstone cores with similar physical properties from the eastern margin of Ordos Basin were selected. Using simulated formation water, distilled water, active water of fracturing fluid, and filtrate of fracturing fluid gel breaking fluid as experimental fluids, parallel experiments of water phase reflux in gas flooding were carried out. By measuring the changes in core permeability before and after gas flooding, quantitative separation of four types of damage mechanisms, namely water locking, water sensitivity, chemical adsorption and fine particle migration, has been achieved. Research results show that under similar physical property conditions, the permeability damage rates caused by the experimental fluid from large to small are as follows:fracturing fluid gel breaking filtrate,fracturing fluid active water, simulated formation water and distilled water. In this area, water-based fracturing fluid damages in tight sandstone is dominated by water blocking(with an average contribution of about 71%), followed by adsorption of the fracturing fluid (with an average contribution of about 11%), while water sensitivity damage and fine particle migration damage are relatively weak. Based on the quantitative evaluation, targeted optimization directions for fracturing fluids are proposed. The core matrix permeability damage rate is reduced to 9.12% in the study area. This method can provide methodological reference for the precise evaluation of fracturing fluid damage and the targeted design of fracturing fluids in tight sandstone and other similar reservoirs.