科研之友
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摘要
Water invasion is a normal state during the depletion development of bottom water gas reservoirs. How water invasion influences the development performance of gas reservoirs and the recovery factor is the focus and difficulty of gas reservoir development. In this paper, the experimental process with multiple pressure measuring points between inlet and outlet is designed according to the structural characteristics of gas reservoirs and the invasion characteristics of bottom water. A long core with multiple pressure measuring points is used to simulate the depletion development dynamic process of low-permeability bottom water gas reservoirs. In addition, the water invasion performance and laws of homogeneous and vertically heterogeneous bottom water gas reservoirs and its influences on recovery factors are studied. And the following research results are obtained. First, the invasion performance of bottom water during the depletion development of homogeneous gas reservoir is obviously affected by reservoir permeability. When the permeability is about 0.1 mD or lower, the invasion of bottom water is very slow, and the supplement effectiveness of water energy is insufficient, so the abandonment pressure is dependent on permeability and the recovery factor is little influenced. On the contrary, the higher the permeability, the faster the water invasion, the more effective the water energy, the earlier the water breakthrough, the higher the abandonment pressure and the greater the decrease of recovery factor. Second, the water invasion performance of vertically heterogeneous bottom water gas reservoir is controlled by the superposition mode of reservoirs with different permeabilities. If the tight reservoir is close to the bottom water, the water invasion speed slows down effectively, the abandonment pressure decreases and the recovery factor increases. On the contrary, the water invasion speed is increased, the abandonment pressure is high and the recovery factor is low. In conclusion, the recovery factor calculation model of bottom water gas reservoirs derived from the material balance equation can accurately fit the development performance and recovery factor of cores. The case of gas reservoir development verifies the effectiveness of the recovery factor model to predict the gas invasion and development performance and recovery factor of bottom water gas reservoirs.
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