具有补给气的异常高压有水凝析气藏物质平衡方程建立及应用

Application and Derivation of Material Balance Equation for Abnormally Pressured Gas Condensate Reservoirs with Gas Recharge Capacity and Water Influx

物质平衡法是计算气藏地质储量、水侵量、补给气量的有效方法之一.具有补给气的异常高压有水凝析气藏是气藏开发中最复杂的类型之一,兼具异常高压气藏、凝析气藏和补给气的边底水气藏的特性.综合考虑开发过程中的凝析油析出,岩石、束缚水和凝析油弹性膨胀,水相挥发,凝析气相中水蒸气增多,水溶气溢出,边底水的推进及外来气补给等复杂物理现象,根据物质平衡原理,推导了具有补给气的异常高压有水凝析气藏物质平衡方程,并运用相对海明距离及关联度理论,以驱动指数均方差、比拟压力与采出程度偏差指数和综合目标函数为分析因素,分析了各组合方案贴近程度及相似程度,挑选最佳组合方案并确定出地质储量、补给气量及水侵量,同时计算了水体倍数.实例计算表明:中国西北某凝析气藏地质储量为66.80×108 m3,如果忽略凝析油,计算地质储量偏大,误差高达91.77%,其次是水侵、弹性膨胀和气侵的影响,误差分别为75.75%、23.95%和12.87%,而溢出水溶气为2.69%与水蒸气为1.65%,影响较小,但也不可忽略.

Material, laalance equation is an effective approach to estimate the OGIP, water influx, and gas recharge capacity in condensate gas reservoirs. The condensate gas reservoir with gas recharge capacity, abnormally high pressure, and edge and bottom water-drive is one of the most complicated reservoirs which include the features of condensate gas, pressure-dependent parameters and water influx. In this study, a new material balance equation for this reservoir was derived which considering retrograde condensation, the expansion of rock, bounded water and condensate oil, the phase change of vapor and dissolved gas, water and gas influx.. The theories of Haiming Distance and relevance is used to analyze the mean square error of drive index, deviation index between pseudo pressure ratio and recovery, and generalized objective function. Based on the analysis of relative similarity degree and closeness coefficient, we chose the optimization scheme, and calculated the OGIP, gas recharge, water influx, and the aquifer volume. Based on the case study in condensate gas reservoir in Northwest China, a calculated reserve is 66.80×10^8m3. We investigated and analyzed the parameters sensitivity by calculating the errors in the assumption of those parameters not included. The error of reserve estimation is up to 91.77%0 if oil condensate is not considered. Other parameters also have some effect such as water influx, the expansion and gas recharge. Respectively, the errors are 75.75%, 23.95% and 12.87 %. The effect of gas escape from the dissolution and vapor is not significant but cannot be neglected, the errors are 2.69 of escaped gas and 1.65% of vapor.