准噶尔盆地玛湖凹陷下二叠统风城组烃源岩热演化及沉积古环境评价

近期准噶尔盆地玛湖凹陷南斜坡地区多口探井钻遇风城组厚层烃源岩,为重新认识玛湖凹陷风城组烃源岩带来了契机,搜集玛湖凹陷南部、北部5口重点探井资料,经分析取得了以下认识:(1)风城组烃源岩在玛湖凹陷内广泛发育,综合玛北、玛南地球化学参数表明其为一套Ⅱ型优质烃源岩;(2)综合现今地温、热解、生物标志物、族组分等参数,认为玛湖凹陷及其周缘地区4 350 m以深的风城组烃源岩处于成熟阶段,4 800 m以深处于高成熟演化阶段,玛湖凹陷风城组烃源岩大范围处于生油高峰期;(3)综合多个生物标志物参数,玛北地区风城组烃源岩为咸化还原沉积,玛南地区风城组二段烃源岩为咸化半还原沉积,风三段烃源岩为半咸化-半还原沉积,陆源有机质输入较多。研究区风城组沉积古环境总体表现出早中期咸化、晚期淡化,北部咸化还原程度高于南部的规律。研究结果对玛湖凹陷风城组后续致密油、页岩油勘探部署提供了理论依据。

Thermal and Paleoenvironment Evolution of the Fengcheng Formation of Permian in Mahu Depression,Junggar Basin

Several exploration wells were recently drilled into the thick hydrocarbon source rock of Fengcheng Formation in the southern slope of Mahu Depression in the Junggar Basin, which brings an opportunity to reveal the source rocks there. This study collected data from five key exploration wells in the southern and northern Mahu Depression, and obtained the following findings: (1) the Fengcheng Formation source rocks are widely distributed in Mahu Depression, and the northern and southern Mahu Depression geochemical parameters show that the source rocks are of II-type and high-quality; (2) based on current geothermal, pyrolysis, biomarkers and group compositions, the Fengcheng Formation source rocks around the Mahu Depression entered mature and highly-mature stage at below 4,350 m and 4,800 m, respectively, and have entered the oil generation peak widely; (3) integrating multiple biomarker parameters, the Fengcheng Formation source rocks in northern Mahu Depression were deposited in a saline and reducing environment, and the source rocks of the Fengcheng Formation (2^nd member) in southern Mahu Depression were deposited in a saline and semi-reducing environment, whilst the 3^rd member (also in southern Mahu Depression) were deposited in a brackish and semi-reducing environment, and adsorbed more terrigenous organic matter. Paleoenvironment of the local Fengcheng Formation is featured by salinization (early) and desalinization (end), and the degree of salinity and reduction in the north is higher than that in the south. This study provides a theoretical basis for the subsequent exploration and deployment of tight oil and shale oil for the Fengcheng Formation in Mahu Depression.