多夹层盐矿水采沉渣空隙特征与储气能力评价

在低品位、多夹层盐矿地层中建设地下储库，利用水采溶腔（盐穴）底部不溶物沉渣空隙储气有望较大幅度扩大储气库库容，但需要开展沉渣空隙储气可行性和适用性评估。首先，采用不溶物沉渣制备大尺寸CT扫描试样，构建了沉渣空隙三维重构模型，定性分析了沉渣空隙尺寸和空隙连通性，发现沉渣空隙尺寸大且连通性好；其次，采用自主研制的盐矿水采沉渣储气试验装置，利用不溶物小颗粒和夹层垮塌大尺寸块体混合堆积样品进行注气排卤试验，测定注气排卤前后沉渣空隙率，分析了沉渣空隙率变化的原因；最后，建立沉渣空隙体积预测模型，提出了盐腔采动空间和沉渣可排卤水体积的计算公式。通过考虑盐层不溶物小颗粒连续堆积，又考虑夹层垮塌大尺寸块体无序堆积，计算了沉渣堆积体积及可排卤储气体积，计算结果与现场采卤数据吻合较好。该研究可为评价低品位、多夹层盐矿沉渣空隙储气能力提供参考。

Pore characteristics and volume capacity evaluation of insoluble sediments for gas storage in multi-interbedded salt formations

Constructing the underground gas storages in low-grade, multi-interbedded salt formations and using the pore space of the insoluble sediments at the bottom of the salt caverns excavated by solution mining to store natural gas are expected to greatly expand the storage capacity of the salt cavern. However, it is necessary to evaluate the feasibility and applicability of the insoluble sediments for gas storage. Firstly, large-size samples were prepared with insoluble sediments for computed tomography scanning, and the size and connectivity of the pores of the insoluble sediments were analyzed qualitatively based on the three-dimensional reconstruction models. Results demonstrated that the pores of the insoluble sediments have large size and adequate connectivity. Secondly, a self-developed experiment device of salt cavern insoluble sediments by solution mining was adopted to carry out the experiments of gas injection and brine displacement. The small insoluble particles and large-size interlayer blocks were mixed for preparing insoluble sediment samples, the porosities of which were measured before and after the experiments of gas injection and brine displacement, and the reasons for the change of porosity were analyzed. Finally, a prediction model of the pore volume of the insoluble sediments was established, and the theoretical equations of the mining space of salt cavern and the volume of the brine which can be discharged from the insoluble sediments were proposed. By considering the continuous accumulation of small insoluble particles and disordered accumulation of the large-size collapsed interlayer blocks, the mining space and drainable brine volume of the insoluble sediments were calculated, respectively, which were in good agreement with the field data of solution mining. This study can provide references for evaluating the volume of pore space of insoluble sediments for gas storage in low-grade, multi-interbedded salt formations.