辽河盆地大民屯凹陷古近系沙河街组页岩气成藏地质条件研究

辽河盆地大民屯凹陷厚层暗色富有机质泥页岩的沉积特征研究和地球化学数据分析结果表明,大民屯古近系凹陷古近系沙河街组发育湖泊和扇三角洲沉积。在扇三角洲中的沼泽地带,发育富有机质的碳质泥岩。暗色泥岩主要产生于半深湖-深湖环境中,具有厚度大、连续性强、分布广的特点。泥岩中的干酪根类型主要以腐泥腐殖质型(II2)和腐殖型(III)为主,利于产气。有机质成熟度(Ro)平均为0.8%~1.3%,有机质处于低熟-成熟阶段。TOC平均为3%~8.46%,有机质丰度较高。脆性矿物总量达到29.0%~51.7%,有利于页岩气的开采。页岩气类型主要为热成因页岩气和生物化学成因页岩气。在页岩气成藏的地质因素分析基础上,综合研究认为,荣胜堡洼陷和三台子洼陷是沙河街组页岩气富集的有利区域。

Geological conditions of shale gas accumulation from Paleogene Shahejie Formation in damintun depression of Liaohe Basin

The results of the research of sedimentary geochemical characteristics and geochemical data of thick layer of dark and organic- rich shale show that lacustrine，fan dalta facies are present in the Paleogene Shahejie For- mation． The dark mudstone mainly deposited in deep to semi- deep lacustrine environments with the characteristics of large thickness，good continuity and wide distribution． The types of kerogen in mudstone are mainly II 2 and III， which is advantageous to the gas generation． The maturity of organics (Ｒo) is 0. 8% ～1. 3%，which is in low- mature to mature situation． The TOC is 3% ～8. 46%，with high abundance of organic matter． Contents of brittle minerals is 29. 0% ～51. 7%，which is the advantage of exploitation of shale gas． The shale gas is mainly biogenic and hydrothermal origin in type． Combined with the achievement in research area，comprehensive analysis of the factors of geological factors of shale gas accumulation suggests that the Ｒongshengbao depression and the Santaizi depression serve as the favorable area for the shale gas exploration in the Damintun depression．