Damage Mechanism Study and Injection Water Optimization of Low Permeability Reservoirs in Wushi Depression

In order to understand the water sensitive damage mechanism of low permeability water sensitive reservoirs in Wushi region and better choose the injection water source, reservoir characteristics were studied by means of casting thin sections, scanning electron microscopy, image analysis and whole rock analysis. Due to the low content of clay and expansive clay minerals in reservoir, the water sensitivity damage mechanism of reservoirs in Wushi region was different from the conventional ones. It was concluded that the damage mechanism of reservoir water sensitivity in Wushi region was mainly based on the internal surface hydration process, which has a certain degree of infiltration hydration process, namely the microscopic "velocity sensitivity" phenomenon. On the basis of mechanism analysis, the compatibility of water injection in low permeability reservoir was studied by using reservoir compatibility experiment and clay swelling suppression experiment. When considering the water flooding and the scaling between injection water and formation water, the influence of swelling and migration of clay minerals on permeability damage can be evaluated. Therefore, the optimization guidance of injection water source can be provided and the risk of reservoir damage is to be reduced.