鄂尔多斯盆地东缘煤层气勘探开发历程与启示

Exploration and development process of coalbed methane in eastern margin of Ordos Basin and its enlightenment

  • 摘要: 鄂尔多斯盆地东缘煤层埋深变化较大,不同埋深的煤层气成藏特征及储层改造方式差别较大。目前煤层气勘探开发深度逐渐从1 000 m以浅延伸到2 000 m以深,为了研究不同埋深条件下煤层气资源高效勘探开发理论技术,系统梳理回顾了鄂尔多斯盆地东缘近30年的勘探开发实践,按照地质认识转变、技术发展、勘探工作量、勘探成果和产气量变化,将鄂尔多斯盆地东缘煤层气勘探开发历程分为3个阶段:浅层煤层气勘探阶段,在“浅层富煤区构造高点富集”理论指导下,寻找“煤层埋深小于800 m、煤层厚度大、高含气量、构造高点”目标,发现韩城WL1井区气田;浅–中深层煤层气规模勘探阶段,以“水动力控气–构造调整–缓坡单斜”成藏理论指导,优选“埋深小于1 500 m、水动力封闭条件好、煤层厚度大、高含气量、缓坡单斜及正向构造”甜点,发现保德、临汾煤层气田,转变储层改造理念,实现韩城构造煤有效增产改造;深层煤层气勘探突破阶段,提出“温压控气、高饱和”成藏模式,指导2 000 m以深煤层气的勘探突破。在此基础上,重点剖析了典型区块的煤层气赋存、富集特征和目标方向,总结了鄂尔多斯盆地东缘煤层气勘探开发获得的3点启示:保存条件是保德区块浅层煤层气富集成藏的重要因素;3类顶板间接压裂射孔模式支撑了韩城构造煤增产改造;“地质–工程”甜点评价助推了大宁−吉县深层煤层气勘探突破。

     

    Abstract: The buried depth of coal seam in the eastern margin of Ordos Basin changes greatly, and the characteristics of coalbed methane reservoir formation and reservoir reconstruction methods vary greatly with different buried depths. At present, coalbed methane exploration gradually extends from a shallow area of 1 000 m to a deeper area of 2 000 m. To study the theory and technology of efficient exploration and development of coalbed methane resources under different burial depths, this paper reviews the exploration and development practices in the eastern margin of Ordos Basin in the past 30 years. According to the changes of geological knowledge, technological development, exploration workload, exploration achievements and gas production,the process of coalbed methane exploration and development in the eastern margin of Ordos Basin is divided into three stages In the first stage of exploring shallow coalbed methane(CBM), under the guidance of the theory of “enrichment of tectonic highs in shallow coal-rich areas”, the gas field in Hancheng WL1 well area is discovered,with coal seam burial depth less than 800 m, large coal seam thickness and high gas content. In the second stage of. shallow-scale of deep coal bed methane exploration, Under the guidance of “hydrodynamic gas control-tectonic adjustment-gently sloping monocline” formation theory, we selected the sweet spots with “burial depth less than 1 500 m, good hydrodynamic closure conditions, large coal seam thickness, high gas content, gently sloping monocline and positive tectonics”, and discovered the coal-bed methane fields in Baode and Linfen, changing the concept of reservior transformation, and realized the effective production enhancement and transformation of Hancheng tectonic coal. In the breakthrough stage of deep CBM exploration, the reservoir formation model of “temperature -pressure controlled gas and high saturation” is put forward to guide the exploration breakthrough of CBM in depth of more than 2 000 m. On this basis, the occurrence, enrichment characteristics and target direction of coalbed methane in typical blocks are analyzed, and three enlightenments from coalbed methane exploration and development in the eastern margin of Ordos Basin are summarized: Preservation conditions are important factors for enrichment and accumulation of shallow coalbed methane in Baode block; Three types of indirect roof fracturing and perforating modes support the coal seam stimulation in Hancheng structure; The “geology-engineering” sweet spot evaluation boosts the exploration breakthrough of deep coalbed methane in Daning-Jixian Block.

     

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