鄂尔多斯盆地上古生界海陆过渡相页岩气聚集条件及有利区预测

Preliminary analysis of marine-continental transitional shale gas accumulation conditions and favorable areas in the Upper Paleozoic Ordos basin

以鄂尔多斯盆地海陆过渡相富有机质泥页岩为研究对象,分析野外露头和岩心观察、采样、地化参数和物性参数等测试资料,研究富有机质泥页岩的沉积相、厚度及分布、有机质类型及含量、热成熟度、孔隙度等页岩气成藏条件.结果表明:鄂尔多斯盆地上古生界石炭—二叠系海陆过渡相富有机质泥页岩主要发育在沼泽相和三角洲相,常与煤层、灰岩、致密砂岩等互层,纵横向变化快,单层厚度小,累计厚度大,有机碳含量相对海相、陆相泥页岩较高.有机质类型以腐殖型为主,有机质热成熟度处在成气高峰阶段,有利于页岩气的形成.综合页岩气藏评价的各项指标信息,预测鄂尔多斯盆地石炭—二叠系海陆过渡相页岩气藏最有利发育区位于盆地东部神木—绥德—延长一带的山西组、盆地北部乌审旗—杭锦旗—东胜—神木与鄂托克旗—盐池一带的太原组及盆地东北部靖边—横山—榆林—神木一带的本溪组,虽然各组地层埋深较大,但多与煤层、致密砂岩层互层,形成页岩气、煤层气和致密砂岩气叠置成藏,具有较大的勘探与开发潜力.

Based on the analysis of observations and samplings of outcrops and cores,and the text of geochemical parameters and physical parameters,we probed into the accumulation conditions of organic-rich shale,such as sedimentary facies,thickness and distribution,organic matter type and content,maturity and porosity.C-P marine-continental transitional organic-rich shale in Ordos basin distribute in marsh and delta which has the characteristics of rapid vertical-lateral variation,diminutive individual thickness,huge cumulative thickness and high TOC.Organic-rich shales usually interlay in coal beds,limestone and tight sand.Their organic matter type is mainly humic and maturity is at the stage of massive gas generation which helps shale gas generate.According to the comprehensive information,Shanxi formation through Shenmu-Suide-Yanchang in the east,Taiyuan formation through Wushenqi-Hangjiqi-Dongsheng-Shenmu and Etuokeqi-Yanchi in the north and Benxi formation through Jingbian-Hengshan-YulinShenmu in the northeast are favorable areas of C-P marine-continental transitional shale gas resources in Ordos Basin.The formation depth is large,but with the interbedded coal seams and tight sandstones so that shale gas,coal bed methane and tight sandstone gas reservoir are stacked.It has a favorable exploration and development potential.