修正的产量不稳定法预测页岩气动态储量

页岩气具有特殊的地质和储层特征,而常规气藏的储量计算方法并未考虑吸附气体解吸引起的压缩系数改变,因此,常规气藏储量计算方法难以准确预测页岩气藏的动态储量,而产量不稳定法比较适用于计算低孔、低渗、压力恢复速度缓慢页岩气藏的动态储量。为此,考虑吸附气体解吸对压缩系数和气体偏差因子的影响,引入吸附气体拟偏差因子和综合压缩系数对产量不稳定法进行了修正,利用修正后的产量不稳定法预测页岩气的动态储量。实例计算表明,忽略吸附气体解吸会导致预测的动态储量偏小,修正产量不稳定法预测的页岩气动态储量比产量不稳定法高21.9%。 

Prediction of Dynamic Reserves of Shale Gas with Modified Flow Rate Transient Approach

Shale gas is an unconventional reservoir,which is widely distributed all over the world;it has an increasing proportion in natural gas production in recent years.Shale gas reservoirs have very low porosity and permeability,and main features of the well test are low or no productivity as well as slow pressure buildup.In addition,the presence of adsorbed gas is another major feature of shale gas reservoirs.Due to special geological and reservoir characteristics,and compression coefficient change caused by desorption of adsorbed gas has not been taken into account when estimating shale gas reserves with conventional calculating method.So,it is difficult to accurately predict the dynamic reserves of shale gas in that way,but rate transient analysis is more suitable for the estimation of shale gas reserves with low porosity,low permeability and slow pressure buildup.Thus,considering effect of desorption of the adsorbed gas on the compression coefficient and gas deviation factor,this approach introduces the adsorbed gas deviation factor and the compression coefficient to modify rate transient analysis to predict dynamic reserves of shale gas reservoir.Examples show that ignorence of desorption produced by adsorbed gas will lead to lower value of predicting dynamic reserves,but the predicting dynamic reserves of shale gas by modified rate transient analysis is more 20% than that calculated by original calculating method.