鄂尔多斯盆地神木及周缘上古生界页岩气成藏条件分析

神木及周缘地区矿藏资源丰富,上古生界页岩气同样具有巨大的勘探潜力,但整体上缺乏对页岩气形成演化进行的系统分析,制约了下一步开发进程。在观察野外地质露头的基础上,根据神木地区的地质、钻井、测井、录井等资料开展了山西组页岩气成藏地质条件动态研究。结果表明:山西组泥页岩富含有机质,分布广泛,厚度较大,具有良好的有机地球化学指标和生烃潜力;与Barnett页岩对比,脆性矿物比重偏低,孔隙度较低,但均高于页岩气成藏参数的下限值;页岩气的形成聚集主要在晚侏罗世—早白垩世就地完成;晚白垩世回返抬升过程产生的断裂活动造成气体向上发生泄漏逸散,压力降低引起吸附气散失从而表现为整体页岩含气量较低;研究区域后期构造相对稳定,对页岩气藏保存有利。不同岩性互层组合构成的多旋回性使得山西组页岩中存在较强的烃浓度封闭作用以及砂岩夹层中的孔隙为游离态的页岩气提供储集空间,进一步增强了该区页岩气的储存能力。通过成藏条件基础研究可为勘探开发目标优选提供地质依据,页岩气的突破可以弥补陕北能源基地传统油气能源的产量。

Shale gas accumulation conditions and stages of Upper Paleozoic in Shenmu area and its periphery, Ordos basin

Mineral resources is very rich in Shenmu area and shale gas of Upper Paleozoic also has great exploration potential.Due to overall lack of systematically analysis on formation and evolution of shale gas,thus restrict next exploitation step in site Research and development of shale gas can play an important role in enhancing the production of clean energy in the northern part of Shanxi Province. Through geochemical,seismic,drilling,well logging and gas logging data ,this paper studies the geological conditions for shale gas accumulation of Shanxi Formation. The results proved that organic-rich shale distributes widely and has huge thickness.The shale has excellent organic geochemical parameters and hydrocarbon generation potential,Compared with Barnett shale,percentage of quartz and feldspar is low and the porosity is relatively small,but both above lower limit value. Formation and accumulation of Shanxi Formation shale gas mainly occurred in place during the Late Jurassic and Early Cretaceous. The gas escaped and dissipated at the uplift and denudation stage after the Early Cretaceous As a result,measured gas content in adsorbed state decreased because of lower pressure at the same time. It is favorable for the preservation of shale gas in the later time while geological structure is relative stable in Ordos Basin. The hydrocarbon concentration sealing has effect caused by lithologic interbedding and sandstone inter layers provide more space for free gas,thus further improving the storage ability of reservoir in the study area.Enhancing the research of accumulation conditions has great significance on unconventional hydrocarbon development to provide a theoretical basis and guide direction for exploitation target optimization in coal-bearing basin .We will achieve many things at one stroke for transformation and upgrading of clean energy base in Northern Shanxi.