四川盆地泸州地区五峰组-龙一_(1)亚段页岩气地质特征与富集高产主控因素

Geological characteristics and main controls on enrichment and high yield of shale gas in Wufeng Formation-Long 1_(1) submember,Luzhou area,Sichuan Basin

近年来,四川盆地泸州地区上奥陶统五峰组-下志留统龙马溪组龙一_(1)亚段多口页岩气井测试获得高产气流,展示了该区良好的页岩气勘探开发前景。为了更好地推进该区页岩气高效勘探与精细开发,以泸州地区五峰组-龙一_(1)亚段富有机质页岩段为研究对象,分析了小层和沉积微相纵横向展布特征、不同沉积微相页岩储层品质差异性,明确了研究区优势页岩沉积微相和页岩气富集高产主控因素。研究结果表明:①泸州地区五峰组-龙一1亚段可细分为五峰组、龙一_(1)^(1)小层、龙一_(1)^(2)小层、龙一_(1)^(3)小层、龙一_(1)^(4)小层5个层段,其岩性、电性、生物化石等特征具有分段性;②研究区五峰组-龙一_(1)亚段共发育9种沉积微相,其中强还原泥质硅质陆棚、强还原含粉砂硅质陆棚、强还原粉砂质钙质-硅质陆棚为最优势沉积微相,页岩具有高有机碳含量、高孔隙度、高含气性、高脆性的“四高”特征,主要发育于龙一_(1)亚段1~3小层;③深水沉积强滞留环境是优质页岩发育和高产的基础,异常高压和高含气量是高产的保障,有效压裂效果是实现高产的关键。

In recent years,high yield has been acquired from the Upper Ordovician Wufeng Formation-the first submember of first member of the Lower Silurian Longmaxi Formation(Long 1_(1)submember)in shale gas wells,Luzhou area,revealing promising prospects in shale gas exploration and development.So,taking the organic-rich shales of Wufeng Formation-Long 1_(1)submember in this area as examples,we discussed the extension of minor layers and microfacies together with the quality difference of shale reservoirs with different microfacies in an effort to better promote both efficient exploration and fine development in Luzhou area.And then,the predominant microfacies and the main controls on shale gas enrichment and high yield were made clear.Results show that,(i)Wufeng Formation-Long 1_(1)submember can be subdivided into Wufeng Formation,Long 1_(1)^(1),Long 1_(1)^(2),Long 1_(1)^(3)and Long 1_(1)4,which individually represent their own characteristics in lithology,electric property and fossil;(ii)totally,there developed 9 microfacies from Wufeng Formation to Long 1_(1)submember,among which,strongly reduced argillaceous siliceous shelf,strongly reduced silty siliceous shelf,and strongly reduced silty calcareous-siliceous shelf function as the most dominant microfacies,where shale features four highs in TOC,porosity,gas content and brittleness.And it is mainly developed in Long 1_(1)^(1),Long 1_(1)^(2)and Long 1_(1)^(3);and(iii)the strongly restricted setting of deepwaters is the foundation for the extension of quality shale with high yield,abnormal pressure and rich gas content as the guarantee,and effective fracturing as the key,respectively.