非均质高压气藏动态储量评价方法

A new method for evaluating the dynamic reserves of high-pressure heterogeneous gas reservoirs

非均质高压气藏动态储量评价存在两大问题:(1)对于高压气藏而言,岩石弹性能量不可忽略,不考虑岩石弹性能量计算的动态储量相对于考虑岩石弹性能量所计算的动态储量,误差高达30%;(2)储层非均质性强,连通程度存在差异导致传统物质平衡法不适应,动态储量难以准确计算。针对以上问题,结合四川盆地安岳气田磨溪区块下寒武统龙王庙组气藏的地质与动态特征,应用最小二乘法确定并评价岩石有效压缩系数;划分连通单元,根据连通单元的特点有针对性地选取相应的动态储量计算方法,形成了以连通单元的划分为基础,实测压力梯度约束下的流压折算与全生命周期压力历史拟合相结合,全生命周期不稳定试井分析法、现代产量递减分析法与异常高压物质平衡法综合应用的非均质气藏动态储量评价方法,并对不同方法的适用性及影响结果准确性的因素进行评价,为非均质高压气藏动态储量评价提供了技术参考。

There are two problems in the evaluation of dynamic reserves of high-pressure heterogeneous gas reservoirs. First, rock expansion of high-pressure gas reservoirs should not be ignored. The error between the dynamic reserves without considering rock expansion and the one with rock expansion is up to 30%. Second, the reservoirs have strong heterogeneity and different connectivities, so the traditional material balance method is unsuitable for the accurate calculation of dynamic reserves. Accordingly, effective rock compressibility was determined and evaluated by using the least square method based on the geological and dynamic characteristics of Lower Cambrian Longwangmiao Formation gas reservoir in Moxi block, ofAnyue Gasfield Sichuan Basin. Then, connected units were divided, and their corresponding dynamic reserve calculation method was selected according to the characteristics of each unit. Thus, a new method for evaluating the dynamic reserves of high-pressure heterogeneous gas reservoirs was developed depending on the divi- sion of connected units. For this method, the reduced flowing pressure under the constraint of measured pressure gradient is combined with the history matching of lifecycle pressure, and lifecycle transient well test analysis method, modern production decline analysis method and abnormal high pressure material balance method are applied comprehensively. Finally, the applicability of each method and the factors affecting the calculation accuracy were evaluated. The study results provide technical reference for the evaluation of dynamic reserves of high-pressure heterogeneous gas reservoirs.