南黄海盆地“三明治”结构的页岩气保存条件探讨

Discussion on preservation conditions of shale gas with“Sandwich”structure in South Yellow Sea basin

为了促进南黄海盆地中-古生界页岩气勘探的早日突破,开展了美国福特沃斯盆地巴奈特页岩气藏、四川盆地页岩气藏以及贵州潜在页岩气藏保存条件的对比研究。结果显示,"三明治"结构的保存条件在页岩气成藏中至关重要,其中,"三明治"结构是指泥岩/页岩层与其顶、底板的灰岩/白云岩层构成的一种很好的储-盖组合。结合下扬子中-古生界发育特征以及南黄海崂山隆起所具有的古生代构造变形弱且隆起两侧边缘存在逆冲断层封堵等条件认为,南黄海盆地下寒武统和二叠系很可能存在"三明治"结构的页岩气保存条件,是南黄海页岩气获得突破的关键层段;而崂山隆起两侧边缘很可能是页岩气钻探的首选目标。

In order to look for Mesozoic-Paleozoic shale gas in the South Yellow Sea basin,a comparative evaluation of preservation conditions is performed among the Barnett shale gas reservoirs in the Fortworth basin of USA,Jiaoshiba shale gas reservoirs in the Sichuan basin and potential shale gas reservoirs in the Guizhou Province.Results show that the so-called＂Sandwich＂structure is of great importance for shale gas accumulation and preservation.The＂Sandwich＂structure is a kind of special reservoir-cap rock assemblage which consists of a limestone or dolomite cap and a limestone or dolomite base with a sequence of mudstone or shale layer in the middle.It is observed that the Mesozoic-Paleozoic strata in the Lower Yangtze,in particular the Laoshan uplift,are characterized by weakly deformed Paleozoic with thrust fault sealing on both flanks of the uplift.＂Sandwich＂structure may exist in the lower Cambrian and Permian strata for shale gas preservation and accumulation.Breakthrough of shale gas exploration is expectable in the South Yellow Sea.The margins of both flanks of the Laoshan uplift will be the preferred targets for shale gas drilling.