中国大多数用于建设盐穴储气库的盐层品位低、不溶物含量高(15%~50%),溶腔时不溶物大量沉积导致造腔速率低、有效储气空间受限。创新地提出小间距定向排卤井高效造腔技术方案,以小间距的定向井与常规直井相连,作为造腔和注气排卤期间的出卤井,可大幅增大有效溶蚀面积、提高造腔速率,同时可排出不溶沉渣体空隙中的卤水用于储气、增大腔体有效储气空间。提出流动自上部自由空间注水管口到下部沉渣体空隙出水管口、沉渣体覆盖壁面溶解速率系数等于空隙率等关键假设,首次建立了小间距定向排卤井高效造腔模拟溶解—沉积数学模型,并以 C++ 语言开发了相应造腔模拟软件。示范算例对比显示，小间距定向排卤井造腔技术方案相较于常规单井造腔方案，造腔效率提高了30%,并可充分溶蚀利用沉渣体以下的盐层,提高盐层利用率15%;同时具备直接利用沉渣体内部空隙储气的井型基础,有效储气体积提高63%。小间距定向排卤井工艺相较于传统单井单腔,在增加少量投资的情况下大幅降低单方工作气投资。研究成果可为高不溶含量盐层的盐穴储气库建设提供新思路及技术指导。

In China, most salt layers suitable for gas storage construction are characterized by low grade and high insoluble content(15%~50%). During solution mining, the massive deposition of insoluble substances leads to low cavern formation rates and reduced effective gas storage volume. To address this issue, a novel small-spacing directional well connection technology was proposed. This approach connects a directional well with a conventional vertical well at a small spacing, utilizing the directional well as a brine drainage well during both cavern formation and gas injection operations. This configuration significantly increases the effective dissolution area by expanding flow channels, enhances cavern formation rates, and enables brine drainage from sediment voids for gas storage, thereby expanding effective gas storage space. Based on key assumptions, including the flow field from the water injection port in the upper free space to the brine discharge port in the lower sediment voids, and the equivalence of the dissolution rate coefficient of sediment-covered walls to porosity, a dissolution-deposition mathematical model for simulating this small-spacing directional well connection technology was established for the first time. Corresponding cavern formation simulation software was developed using C++. Demonstration case comparisons reveal that the proposed solution achieves a 30% improvement in cavern formation efficiency compared to conventional single-well methods, a 15% increase in salt layer utilization through enhanced dissolution of sub-sediment salt layers, and a 63% expansion of effective gas storage volume by directly utilizing pore spaces within sediment deposits. Compared to traditional single-well single-cavern approaches, this small-spacing directional well technology significantly reduces unit working gas investment costs with only marginal additional capital expenditure. The research findings can provide new ideas and technical guidance for the construction of salt cavern gas storage facilities in salt layers with high insoluble content.