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In order to reduce water locking/aqueous phase trapping damage caused by drilling completion and fracturing acidizing operation of tight sandstone gas reservoir in Ke Keya structure, and improve infiltrating conditions of reservoir gas phase to achieve business development effect, in view of reservoir characteristics of tight sandstone gas reservoir, the water locking/aqueous phase trapping damage mechanism and effect factors are analyzed. By means of natural core of the tight sandstone gas reservoir in Ke Keya structure, the method for using methanol hybrid simulated formation water saturation has been established different core water saturation, and studied the effect of time and depth of capillary imbibitions formation water and other factors on reservoir, permeability and water locking/aqueous phase trapping damage, as well as the effect of water saturation variation on reservoir permeability and water locking/water phase trapping index in different methanol concentration water saturation. Two experimental methods for adopting three groups of different permeability, porosity cores has been made separately damage evaluation experiments, the results obtained are consistent. The experimental results show that the reservoir water saturation is less than 20%, and has the strongest effect of water phase trapping. With the reservoir water saturation increasing, aqueous phase trapping effect gradually decreases while water locking effect gradually increases, gas phase permeability is significantly decreased, and the water saturation ranging from 0 to 40% greatly drops. When the reservoir water saturation is more than 60% of the critical value, the water locking damage is increased, and the permeability of matrix becomes very small, and even loss of percolation capacity. Experimental results have guiding significance for controlling reasonably water saturation of tight sandstone gas reservoirs in Ke Keya structure, and provides reference for inhibiting water locking/aqueous trapping damage in low permeability gas reservoirs. |
