多夹层盐矿地下储气库气体渗漏评价方法

Gas leakage assessment method of underground gas storage in multi-interlayer salt mine

我国盐穴地下储气库一般建设于富含泥质夹层的湖相沉积盐岩中,由于泥质夹层的孔隙率和渗透率均大于盐岩,因此其渗透性能对储气库的密闭性起控制作用。夹层的沉积特性一般沿水平展布,据此建立多夹层盐穴储气库渗漏分析理论模型。依据某储气库泥岩夹层的孔渗测试数据,并结合实际运行参数进行天然气渗漏计算。再利用以上研究成果分析气体渗漏范围和泄漏量的影响因素及变化规律,并对储气库选址及设计中的几个关键参数展开适用性评价,如储库离盐矿边界及断层的安全距离、相邻储气库安全矿柱宽度等。研究表明:泥质夹层孔隙压力的变化趋势表现为沿径向先急剧降低,而后趋于稳定;某时刻气体渗流范围和泄漏量由夹层渗透参数、渗透介质以及初始孔隙压力共同决定;渗流的影响范围随着时间的增加而逐渐增大,最终也趋于稳定。研究结果可为多夹层盐穴储气库选址、设计及密封性评价提供理论和技术支撑。

In China, the gas storage in underground salt cavern is normally built in the lacustrine sedimentary salt rock, which is rich in muddy interlayers. Since the permeability and porosity of muddy intedayers are higher than those of salt rock, the sealing of the gas storage is determined by the permeability of muddy interlayers. In this study, a new theoretical model is established for the seepage analysis of bedded salt cavern gas storage. This model is based on the sedimentary characteristics of mudstone interlayer, which is horizontally distributed. Natural gas leakage is also calculated by using the porosity-permeability testing data and the actual operation parameters of the mudstone in a gas reservoir. According to the above results, this study analyzes the influencing factors and change regularities of gas leakage and seepage range. Furthermore, an applicability evaluation is given by considering several key parameters in siting and designing the gas storage reservoir, such as safe distance from salt cavern to salt mine boundary or faults, safe Salt pillar width of adjacent storage and some others design indexes of rock salt gas storage. The analytical results show that pore pressure in the muddy interlayer firstly decreases sharply along the radial direction, and then tends to be stable. Gas seepage range and leakage at a certain time are determined by the permeability parameters of the interlayer, permeability media and the initial pore pressure together. The influencing range of seepage gradually increases with time elapsing, and eventually becomes stable as well. Hence, this study can provide theoretical and technical support for the location, design and sealing evaluation of multi-interlayers salt cavern gas storage.