陆相页岩气的地质研究进展及亟待解决的问题——以延长探区上三叠统延长组长7段页岩为例

中国陆相页岩气的开发还处在探索阶段,究其根本原因在于地质理论尚未取得突破,由此导致其开发缺乏理论指导。为此,基于陆相页岩气的地球化学特征、地质条件及勘探工程生产实践,以延长探区上三叠统延长组长7段页岩为例,归纳总结了目前在该研究领域已取得的主要地质认识:成因类型多样;地球化学参数综合决定页岩含气量;砂质纹层对改善页岩储集物性具有重大贡献;页岩气的赋存需要"盖层条件",其赋存形式多样并存在先后顺序。同时指出了当前陆相页岩气在地质特征及成藏机理方面亟待解决的问题:陆相页岩的生油气机理,对储层赋存空间的认识,对页岩气赋存相态进行精确定量,温压系统的演变对地层压力、气体赋存作用的影响等。地质评价方面有待解决的问题包括页岩气定义对资源结构的影响,资源评价中关键参数的取值,勘探靶区的优选等。上述问题的解决,将有助于突破制约陆相页岩气地质研究理论的瓶颈,推动陆相页岩气的勘探开发。

Progress in and challenges to geologic research of terrestrial shale in China:A case study from the 7th member of the Upper Triassic Yanchang Fm in the anchang exploration block,Ordos Basin

The terrestrial shale gas development is still in its infancy in China and no breakthrough has ever been made in the relevant geological theories. In view of this, in a case study from the 7^th member of the Upper Triassic Yanchang Fm in the Yanchang exploration block in the Ordos Basin, we first summarized the current main understandings of the geologic conditions concerning terrestrial shale gas plays, such as multiple genetic types, geochemical parameters determining shale gas content, sandy laminar critical in improving reservoir property of shale, seals essential to the preservation of shale gas, and multiple shale gas storage patterns with a certain order of priority. The challenges facing the study of geologic features and reservoiring mechanisms of terrestrial shale gas are as follows: hydrocarbon generation mechanism, reservoir space, accurate quantification of phase behaviors of shale gas, as well as the influences of temperature pressure system evolution on formation pressure and gas storage. And other challenges to geologic evaluation include the influences of shale gas definition on resource structure, value assignment of key parameters in resource evaluation, and the selection of target areas. The successful resolution of all above problems will help break the bottleneck in current geologic research and improve exploration and development of terrestrial shale gas in China.