WHD1井五峰组-高家边组页岩气地质条件初析

Initial analysis of shale gas geological conditions of Wufeng-Gaojiabian Formation in well WHD1

WHD1井位于下扬子地块沿江隆凹褶断带,为安徽省境内巢湖地区首口针对上奥陶统五峰组-下志留统高家边组下段目的层位的页岩气地质调查井。通过钻探、录井、测井以及实验分析等方法,对WHD1井及周边区域奥陶系-志留系地层发育,黑色页岩厚度分布、生烃条件、储集条件以及含气条件等特征有了新的认识。研究结果表明,WHD1井自上而下钻遇志留系坟头组、高家边组、奥陶系五峰组、汤头组、宝塔组、庙坡组、牯牛潭组、大湾组以及红花园组等地层。该井首次最大程度地揭露了高家边组地层厚度1119.18m,其中五峰组-高家边组下段富有机质页岩(wTOC>1%)厚度为43.90m,优质页岩(wTOC>2%)厚度为17.95m,有机质类型为Ⅰ型,有机质丰度评价为中-好等级,有机质成熟度为过成熟早-中期生干气阶段,具有丰富的物质基础和生气条件。储层条件方面,五峰组-高家边组下段富有机质页岩有机质孔隙度发育,解吸气可点燃,脆性矿物含量较高,以上特征均表明该套层位在储集空间、含气潜力以及后期压裂可改造性方面均具有较好的储层条件。WHD1井的钻探证明,该地区的五峰组-高家边组下段黑色富有机质页岩具有一定的页岩气勘探潜力。

Well WHD1 is located in the uplifting-depression fold and thrust belt in Lower Yangtze plate, which is the first shale gas geological investigation well for the Upper Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation in Chaohu, Anhui Province. By using drilling, logging and experimental analysis methods, a new insight into the development of Ordovician-Silurian formation as well as the organic-rich black shale thickness distribution, gas-generating, gas preservation and gas-bearing conditions is offered. The results show that well WHD1 drills into the Silurian Fentou and Gaojiabian Formation, the Ordovician Wufeng, Tangtou, Baota, Miaopo, Guniutan, Dawan and Honghuayuan Formation from top to bottom. The well reveals the Gaojiabian Formation thickness as 1 119.18 m for the first time. The organic-rich shale( w TOC >1%) thickness and excellent shale( w TOC >2%) thickness in the lower member of Wufeng-Gaojiabian Formation are 43.90 m and 17.95 m, respectively, which are characterized with Ⅰ type organic matter, abundant organic carbon content and over-mature dry gas evolution stage. The lower member of Wufeng-Gaojiabian Formation obtains the abundant matter basis and favorable gas-generating conditions. As for the reservoir conditions, the shale in the aimed formation develops plenty of organic pores and contains rich brittle minerals. The gas collected from the shale pores and cracks can be ignited. All of these imply that the lower member of Wufeng-Gaojiabian Formation possesses better reservoir conditions in view of the reservoir space, gas-bearing potential and later fracturing reconstruction. Consequently, well WHD1 shows that the organic-rich shale in the lower member of Wufeng-Gaojiabian Formation in this area has certain shale gas exploration potential.