Study on the Mobility and Flow Mechanism of Aquifer Water in Carbonate Gas Reservoirs

AbstractWater invasion is one of the most critical constraints on developing carbonate gas reservoirs, with a significant impact on gas well production. Therefore, it is crucial to establish a correct experimental model of water invasion to study the mobility and flow mechanism of aquifer water. In this study, three-full-diameter core was selected from Longwangmiao carbonate gas reservoirs. Then, the experimental evaluation methods and process of aquifer water mobility are established and conducted, and the effects of different parameters on the mobility of aquifer water are analyzed. The results show that the mobility of aquifer water is affected by the pore compressibility of formation rock and its elastic expansion. The proportion of movable water per unit drawdown pressure is 0.1%/MPa, which has little relationship with the production pressure difference. The formation drawdown pressure is the key factor controlling the mobility of the aquifer water. The greater the formation drawdown pressure, the higher the proportion of movable water in aquifer water, and the stronger the degree of water invasion. The cumulative movable water accounted for 6%-9% of the aquifer water in the development of carbonate gas reservoirs, and the final movable water production is related to the abandonment pressure. The aquifer water did not flow initially with drawdown pressure, but there was a critical drawdown pressure with the value of 10 MPa to 13 MPa, and it has a negative association with reservoir permeability. The finding of this study can help for better understanding the concept of water invasion in formation water-bearing reservoirs, and these results can fill the gaps in the mobility conditions and flow mechanisms of aquifer water and provide technical reference for optimizing water-invasion carbonate gas reservoir development.