含水层型地下储库惰性气体作垫层气数值模拟

以廉价的惰性气体代替天然气作为含水层型地下储气库垫层气时,不同气体之间的相互掺混会影响回采气的质量,因此,确定储库内气体浓度动态分布情况非常重要.通过建立气水渗流模型及气体扩散模型,采用有限元法,对封闭边界条件储库的建库及工业运行过程进行模拟,分别对单井注氮单井注采天然气及从边缘井注氮中心井注采天然气这两种情况下,储库压力、含水饱和度、气体浓度的动态变化情况进行分析.单井情况下,停止回采时,回采气中氮气浓度达9.665%,说明由于对流及扩散作用,氮气与天然气存在一定程度的混合.多井情况下,停止回采时,氮气浓度只有0.094%,说明多井注采可以有效抑制天然气与氮气的混合.

Simulation on use of inert cushion gas in underground gas storage reservoir in aquifer

Aiming at the influence of the mixing of two gases caused by the substitution of inert gas for part of the cushion on the quality of withdrawn gas in the underground gas storage reservoir in aquifer,models on gas-water flow and gas diffusion were developed. The construction and commercial operation were simulated with the finite element method. The pressure distribution,water saturation and percentage of natural gas and inert gas were analyzed respectively in two conditions:nitrogen injection and natural gas withdrawal from a single well,nitrogen injection from border wells and natural gas injection and withdrawl from the center well. Results show that in the single-well condition,the percent of nitrogen in withdrawn gas reaches 9.665% when the gas withdrawal completes,which demonstrates the occurrence of a certain degree of mixing between the nitrogen and natural gas; in the multi-well condition,the percent of nitrogen in withdrawn gas is 0.094% when gas withdrawal completes,which demonstrates that the multi-well process can restrain the mixing between different gases effectively.