渝东南盆缘转换带金佛斜坡常压页岩气富集模式

近期,渝东南盆缘转换带金佛斜坡新完钻的页岩气井在上奥陶统五峰组—下志留统龙马溪组获得高产气流,地层压力系数为1.18,实现了该地区常压页岩气勘探的重大突破。为了评价该类型页岩气藏的勘探开发潜力,以钻井、物探和试气等资料为基础,解剖金佛斜坡页岩气藏基本地质特征和页岩气富集规律,总结常压页岩气富集高产主控因素,建立页岩气富集模式,并预测该区常压页岩气勘探开发有利目标区。研究结果表明:①该区优质页岩具有生气条件好、硅质矿物含量高、储层物性好、含气量高等特征,具有较大的页岩气勘探开发潜力;②常压页岩气富集高产具有"沉积相供烃控储、构造运动控保定富、地应力场控缝控产"的"三元控气"规律;③斜坡型目的层上倾方向发育封闭性反向逆断层遮挡有利于在断下盘形成较好的保存单元,随着埋深和离剥蚀边界距离的增大,页岩气富集程度和单井产量增高。结论认为,该研究成果丰富了常压页岩气地质理论,为中国南方复杂构造区尤其是斜坡型常压页岩气勘探开发提供了支撑。

Enrichment model of normal-pressure shale gas in the Jinfo slope of the basin-margin transition zone in Southeast Chongqing

Recently, the newly drilled shale gas well in the Jinfo slope of the transition zone along the margin of the southeast Chongqing Basin produced a high-yield gas flow from the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation with a formation pressure coefficient being up to 1.18, demonstrating a great breakthrough in the exploration of normal pressure shale gas in this area. In order to evaluate the exploration potential of this type of shale gas reservoirs, this paper analyzed the basic geological characteristics and the shale gas enrichment rules of shale gas reservoirs in the Jinfo slope based on drilling, geophysical exploration and test data. Then, the main factors controlling the enrichment and high yield of normal-pressure shale gas were summarized, and the shale gas enrichment model was established. Finally, the favorable target area for the exploration and development of normal-pressure shale gas in this area was predicted. And the following research results are obtained. First, the high-quality shale in this area is characterized by good gas generation conditions, high siliceous mineral content, good reservoir physical properties and high gas content, presenting a greater shale gas exploration potential. Second, the enrichment and high yield of normal-pressure shale gas follows the rule of "three-factor gas control", i.e., sedimentary facies controlling hydrocarbon supply and reservoirs, tectonic movement controlling preservation and enrichment, and in-situ stress field controlling fractures and production. Third, the sealing capacity of the sealing reverse thrust fault which is developed in the updip direction of the slope-type target layer is conducive to the formation of a good preservation unit in the fault footwall. As the burial depth and the distance from the denudation boundary increase, the shale gas enrichment degree and the single-well production rate increase. In conclusion, the research results enrich the geological theory of normal-pressure shale gas and provide support for the exploration and development of normal-pressure shale gas in the complex tectonic areas, especially in the slopes, in southern China, .