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页岩气藏资源评价和开发的关键基础资料——等温吸附曲线,通常是通过容量法等温吸附实验获取的,决定其准确与否的关键是选择合适的气体状态方程来计算吸附/解吸气量。为此,针对不同气体状态方程对页岩气相态描述差异较大的情况,设计了简易、方便的气体状态方程优选评价实验装置和实验方案,该方法避开了对气体体积的频繁计算所带来的实验误差,仅通过测试不同状态下的压力即可评价气体状态方程的适用性,其原理和设备操作简单,计算方便。对实验结果的分析结论表明:(1)不同气体状态方程对甲烷的相态描述均有不同程度偏差,且压力越高偏差越大,页岩等温吸附实验中必须优选合适的气体状态方程来计算吸附气量和解析气量;(2)低压下(小于10 MPa)宜选用SRK方程、高压下(大于10 MPa)宜采用RK方程来计算甲烷气田相态变化;(3)总体上,结合我国页岩气藏埋藏较深、压力多在20 MPa以上的实际情况,RK方程能更好地计算出甲烷气田的相态变化特征,从而满足页岩等温吸附实验的需要。
The key basic data for evaluation and development of shale gas reservoir-isothermal adsorption curve, is usually obtained by isothermal adsorption experiments of volumetric method. The key to determine whether it is accurate or not is to select suitable gas equation of state to calculate adsorption / desorption gas volume. For this reason, a simple and convenient gas equation of state equation optimization experimental apparatus and experimental scheme are designed for different gas state equations to describe the phase state of shale gas greatly. The method avoids the frequent calculation of gas volume To the experimental error, only by testing the pressure in different states to evaluate the applicability of gas state equation, the principle and equipment is simple, easy to calculate. The analysis of the experimental results shows that: (1) The equation states of different gases have different degrees of deviation for the phase description of methane, and the higher the pressure, the greater the deviation, the shale isothermal adsorption experiments must be the appropriate gas equation of state to calculate (2) The SRK equation should be used under low pressure (less than 10 MPa), and RK equation should be used to calculate the phase change of methane gas under high pressure (> 10 MPa). (3) In general, The gas reservoir is buried deeper and the pressure is more than 20 MPa. The RK equation can better calculate the phase change characteristics of the methane gas field, so as to meet the needs of shale isothermal adsorption experiments.