异常高压页岩气物质平衡方程及储量计算

Material Balance Equation for Abnormally High-pressure Shale Gas Reservoirs and Calculation of Reserves

异常高压页岩气藏岩石压缩系数不是一个定值,随着地层压力下降,岩石压缩系数不断变小。异常高压页岩气藏在利用物质平衡方程进行动态储量评价时,应该考虑这一特性。以常规物质平衡方程为基础,考虑页岩压缩系数的连续变化,考虑页岩气的吸附解吸过程,建立了考虑页岩压缩系数连续变化的异常高压页岩气藏物质平衡方程,适用于异常高压页岩气藏动态储量评价。实例计算表明:异常高压页岩气藏岩石压缩系数对动态储量评价影响明显,考虑岩石压缩系数影响的物质平衡方程动态储量计算的结果较不考虑岩石压缩系数影响时的低14%;建立的考虑岩石压缩系数随有效应力变化的物质平衡方程较岩石压缩系数为定值的物质平衡方程动态储量计算结果高6.5%;建立的新物质平衡方程考虑了异常高压页岩气藏岩石压缩系数的连续变化,能够反映异常高压页岩气藏岩石弹性能量不断下降这一特性,计算结果更准确,更符合实际。

The rock compressibility of shale gas reservoirs with abnormally high pressure was not a constant,the compression coefficient of rock became smaller and smaller with the decrease of formation pressure.So it should be considered when calculating the dynamic reserves through the material balance equation.On the basis of the conventional gas reservoir material balance equation,a new material balance equation considering the continuous change of rock compressibility and shale gas desorption was established for abnormally high pressure shale gas reservoirs.The new material balance equation was suitable for dynamic reserves evaluation of abnormally high pressure shale gas reser-voirs.The calculation example shows that the rock compressibility of abnormally high pressure gas reservoir has obvious influence on dynamic reserves evaluation;the dynamic reserves calculated by the material balance equation considering the rock compressibility are 14%lower than those without considering the rock compressibility.The dynamic reserves calculated by the new established material balance equation considering the continuous change of rock compressibility are 6.5% higher than those calculated by the material balance equation considering the rock compressibility as a constant.The new established material balance equation can reflect the elastic energy change of abnormally high pressure shale gas reservoirs;the dynamic reserves calculated by the new material balance equation are more accurate and more practical.