上扬子地台北缘下寒武统牛蹄塘组海相页岩气地质条件及勘探潜力

基于野外露头和钻井岩芯采样分析,对上扬子地台北缘下寒武统牛蹄塘组黑色页岩分布特征、地球化学特征、储层特征、含气性特征及顶底板条件等进行系统研究,并与中国南方地区下寒武统海相页岩展开对比分析,明确页岩气成藏地质条件和勘探潜力。结果表明:上扬子地台北缘下寒武统牛蹄塘组页岩发育且厚度大,具有"四高一中"特点,即高脆性、高总有机碳、高孔隙度、高含气量、适中热演化程度,显示良好的页岩气形成地质条件;相比中国南方地区下寒武统海相页岩,上扬子地台北缘牛蹄塘组页岩具备足够的生烃物质基础和较高的脆性,并且富有机质页岩厚度大,热演化程度低,孔隙度和含气量高,勘探效果较好;综合考虑优质页岩的厚度、埋深、保存等条件,认为回军坝-麻柳镇一带是上扬子地台北缘牛蹄塘组海相页岩气下一步勘探的最有利地区。

Geological Conditions and Exploration Potential of Lower Cambrian Niutitang Formation Marine-facies Shale Gas in the Northern Margin of Upper Yangtze Platform,China

Based on the analysis results of field outcrops and drilling cores, the Lower Cambrian Niutitang Formation black shale in the northern margin of Upper Yangtze platform was systematically studied and compared with the strata in southern China, including the characteristics of distribution, geochemistry, reservoir, gas-bearing and the conditions of roof and floor. Then, the geological conditions and exploration potential of shale gas accumulation were clarified. The results show that the shale is developed with large thickness and characteristics of high brittleness, high TOC, high porosity, high gas content and moderate thermal evolution, showing good conditions for shale gas development;compared with Lower Cambrian marine-facies shales in southern China, the Niutitang Formation shale in the northern margin of Upper Yangtze platform has quite sufficient hydrocarbon-generating materials and high brittleness, but thicker shale, lower thermal evolution, higher gas contents and porosity, indicating better prospects for shale gas exploration;considering the thickness, depth and preservation conditions of good quality shale comprehensively, the Huijunba-Maliuzhen area is the favorable exploration for the marine-facies shale gas of Niutitang Formation in the northern margin of Upper Yangtze platform.