赣西北武宁地区新开岭组页岩含气潜力新认识

New Understanding of Xinkailing Formation Shale Gas-Bearing Potential in Wuning Area,Northwest Jiangxi

鉴于赣西北武宁地区新开岭剖面附近一口水井钻遇新开岭组黑色页岩新鲜样品,开展了相关实验分析并对该层位页岩含气潜力进行了评价;通过岩心观察、有机地球化学分析、矿物组成分析、扫描电镜观察、比表面积分析以及等温吸附等研究方法,对武宁地区新开岭组页岩的生气条件和储集条件进行了研究,并分析了其含气潜力。研究结果表明,武宁地区新开岭组黑色页岩样品有机质类型为Ⅰ型和Ⅱ型,w(TOC)介于1.18%～3.11%之间,平均为2.11%,Ro平均为2.99%,处于过成熟早期-中期阶段,生气条件较好;宏观裂缝上高角度剪切裂缝、层间页理缝以及成岩收缩缝发育,微观孔隙上有机质孔隙、黏土矿物粒间微裂缝、粒间溶蚀孔隙以及矿物间孔隙发育,储集空间类型丰富,储集条件较好,且脆性矿物含量高易于后期压裂改造,储层条件较好;吸附气量介于2.12～3.47m3/t之间,具有较好的吸附能力。武宁地区新开岭组与中上扬子地区龙马溪组关键参数的对比分析表明,武宁地区新开岭组具备形成页岩气的有利条件,页岩气资源潜力较大。

A water well,located beside the Xinkailing section,firstly exposed the characteristics of the Xinkailing Formation marine shale before being weathered in Wuningarea,Northwest Jiangxi.This paper studies the gas generation conditions,the reservoir conditions and the gas-bearing potential by core observation,organic geochemic alanalysis,mineralogical analysis,SEM,surface area analysis and isothermal adsorptions.The results show that the Xinkailing Formation black shale has better gas-generating conditions and organic matter types are Ⅰ and Ⅱwith the TOC ranging from 1.18%to 3.11%,averaging 2.11%and the Ro 2.99%in average,meaning the early-middle stage of the over-maturity.Besides,the Xinkailing Formation black shale has better reservoir conditions and there is abundant reservoir space including macro-cracks and micro-pores and the high content of brittle minerals infavor of the late fracturing.The Xinkailing Formation black shale possessesa bette radsorption capacity with the adsorptiona mount ranging from 2.12to 3.47m^3/t.The comparison between the key parameters of the Xinkailing Formation in Wuning area and those of the Longmaxi Formation in the middle-upper Yangtze area indicates that the Xinkailing Formation has the favorable conditions for the accumulation of shale gas and the great shale gas resource potential.