延安地区陆相页岩气动态储量计算方法研究

Dynamic reserves calculation method of continental shale gas in Yan’an Area

针对延安地区陆相页岩气储层压力低、吸附气含量高以及压恢测试难导致的动态储量预测难这一问题,在传统流动物质平衡法的基础上,运用油气渗流理论和油气藏工程方法,建立了适合延安地区陆相页岩气动态储量计算的流动物质平衡模型,并结合实际生产资料,评价了实际陆相页岩气井的动态储量。结果表明:1)传统流动物质平衡法忽略了天然气压缩系数(C_(g))和黏度(μ_(g))在生产过程中的变化,而这种变化在延安地区陆相页岩气低压、高吸附量的条件下极为显著;2)忽略页岩气降压过程中μ_(g)C_(g)的变化以及吸附气解吸效应,将导致预测的动态储量偏低;3)以延安地区某陆相页岩气井为例,利用建立的评价方法预测得到该井动态储量为2.2×10^(7)m^(3),比传统方法高10%;同时也表明该井所在的区域具有一定的开发前景。该研究对于延安地区陆相页岩气生产制度制定和产量预测具有重要的指导意义。

According to the difficulty in dynamic reserves prediction induced by the low pressure,high adsorbed gas content and hard pressure-up test of continental shale gas in Yan’an Area,this paper use the gas percolation theory and reservoir engineering method to establish a flow material balance model suitable for the calculation of dynamic reserves of continental shale gas in Yan’an Area on the basis of traditional flow mass balance method.Furthermore,combined with actual production data,the dynamic reserves of actual continental shale gas wells are evaluated.The results showed that:1)The traditional flow mass balance method ignores the variations of gas compression coefficient(C_(g))and viscosity(μ_(g))during the production process,which are very significant under the conditions of low pressure and high adsorption capacity of continental shale gas in Yan’an Area;2)Ignoring the change of μ_(g)C_(g) and the desorption effect of adsorbed gas during the step-down process of shale gas will lead to a low predicted dynamic reserve;3)Taking a continental shale gas well in Yan’an Area as an example,the dynamic reserves of this well are predicted to be 2.2×10^(7) m^(3) by using the established method,which is 10%higher than that of the traditional method.Meanwhile,it also shows that the area where the well is located has certain development prospects.The study has important guiding significance for the production system and production prediction of terrestrial shale gas in Yan’an Area.