四川盆地北部大隆组页岩气地质条件及勘探潜力

Geological Conditions and Exploration Potential of Shale Gas in Dalong Formation in Northern Sichuan Basin

王明筏 文虎 倪楷 付小平 杨鸿飞

WANG Mingfa WEN Hu NI Kai FU Xiaoping YANG Hongfei

中国石化勘探分公司, 四川 成都 610041

SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

以最新钻井LB1井、7个野外露头剖面及部分老井资料为依托，探讨了四川盆地北部大隆组优质页岩的平面及纵向展布规律，认为优质页岩的展布受沉积相控制，呈NW—SE走向。在广元—旺苍地区发育盆地相，泥页岩厚度较小（10~20 m）；盆地相两边发育深水陆棚相，泥页岩厚度较大（20~45 m）；外围依次发育浅水陆棚或斜坡相，泥页岩厚度逐渐变小（0~15 m）。从斜坡相到陆棚相，再到盆地相，呈现出灰质逐步减少，硅质含量逐渐增加的特征，泥页岩厚度呈先大（深水陆棚相）后小（盆地）的趋势。另外，对LB1井地化特征、储层微观特征开展研究，并与已突破的焦石坝、丁山、东溪地区志留系页岩对比，分析认为，四川盆地北部大隆组优质页岩具有高有机碳、高含气量、有机质类型好、成熟度适中及可压性好等特点。根据高有机碳的特点，认为无定形体有机质的广泛发育是高有机碳含量的基础，缺氧硫化环境是保存的关键。根据高含气量的特点，认为含气性和比表面积具有较好的相关性，而对比表面积贡献较大的主要是有机质含量。最后评价了中国石化矿权内大隆组勘探潜力，认为资源量较大，值得进一步开展工作。

On the basis of the latest Well LB1 and 7 outcrops data and data of some old wells, the study evaluates the horizontal and vertical distribution law of high-quality shale of Dalong Formation in northern Sichuan Basin. It is considered that the distribution of high-quality shale is controlled by sedimentary facies and shows NW-SE trend. Basin facies have developed in Guangyuan-Wangcang Area with small shale thickness(10~20 m); deep-water shelf facies have developed on both sides of the basin facies, and the thickness of shale is relatively bigger(20~45 m); shallow-water shelf or slope facies have developed in the periphery, and the thickness of shale gradually becomes smaller(0~15 m). From slope facies to shelf facies, then to basin facies, the content of calcareous decreases and the content of silica increases gradually; the thickness of shale is bigger first (deep-water shelf facies) and then smaller (basin facies). In addition, the geochemical characteristics and reservoir microscopic characteristics of Well LB1 are studied, then compared with the Silurian shale fields in Jiaoshiba, Dingshan and Dongxi areas. It is concluded that the high quality shale of Dalong Formation has the characteristics of high organic carbon content, high gas content, good kerogen type, moderate maturity and good compressibility. It is considered that the extensive development of amorphous organic matter is the controlling factor of high organic carbon contentand the anoxic sulfide environment is the key to preservation. The characteristics of high gas content is due to a good correlation between gas content and the specific surface area, and the main contribution of the specific surface area is the content of organic matter. Finally, we have found that the resources of Dalong Formation in SINOPEC mining right have great exploration potential, which is worthy of further exploration.

10.11885/j.issn.1674-5086.2020.11.05.01