雪峰山西侧构造演化和构造格局对区域油气成藏条件的控制

本文对雪峰造山带北西缘及其北西侧隔槽式褶皱带的区域构造演化和构造格局与油气关系进行了总结和探讨,主要认识如下:震旦纪-早古生代的被动大陆边缘盆地(Z1-O1)和前陆盆地(O2-S)背景下形成了3套主要生储盖组合。主要烃源层牛蹄塘组早奥陶世开始排烃(油)、三叠纪末排烃(气)基本结束;五峰-龙马溪组晚古生代中期开始排烃(油),白垩纪末排烃(气)基本结束。晚奥陶世后期的都匀运动形成了雪峰造山带北缘隆起和黔中隆起(为大型圈闭),中侏罗世或中三叠世以前的油气多由周边凹陷区向这两个隆起区运移、聚集,严重影响到凹陷区中生代圈闭内天然气成藏潜力和规模。受排烃历史控制,隔槽式褶皱带内中生代圈闭构造有可能形成以五峰-龙马溪组为烃源的较大规模上组合气藏;以牛蹄塘组为烃源的下组合和中组合一般难以成藏,但在黔中隆起带有可能形成次生气藏。最后,基于构造和油气演化特征,探讨了研究区油气成藏远景,并提出了油气勘探方向建议。

Control of tectonic evolution and tectonic framework on the hydrocarbon accumulation in the western side of the Xuefeng Mountain

The authors studied the relationships between the tectonic evolutions and hydrocarbon on the north-west margin of Xuefeng Orogen Belt and in the trough like fold belt on the northwestern side of the margin, and reached the following conclusions. Three principal source-reservoir-caprock assemblages were formed in Simi-an-Early Paleozoic tectonic settings of passive continental margin basin (Z1-O1) and foreland basin (O2-S). The hydrocarbon migration of the main source rock in Niutitang Formation began in Early Ordovician and almost end-ed in latest Triassic. The hydrocarbon migration of Wufeng Formation and Longmaxi Formation began in middle Later Paleozoic and almost ended in latest Cretaceous. The northwest margin uplift of Xuefeng Orogen Belt and the Central Guizhou Palaeouplift were formed in Duyun Movement in later Late Ordovician. The hydrocarbon mi-grated from surrounding depression area to the two uplifts and accumulated before Middle Jurassic or Middle Tri-assic, which reduced significantly natural gas reservoir-forming potential and scale of Mesozoic traps in depres-sion area. Controlled by hydrocarbon migration histories, larger gas reservoirs of the upper assemblage derived from Wufeng Formation and Longmaxi Formation can be formed in the Mesozoic traps in the trough like fold belt,and it was generally difficult for the gas reservoirs of the middle and lower assemblage derived from Niutitang For-mation to be formed, while larger secondary gas reservoir of the middle and lower assemblage can be formed in the Central Guizhou Palaeouplift. In the end, based on the tectonic and hydrocarbon evolutions, the authors probed into oil-gas accumulation prospect, and made their suggestions for oil-gas exploration direction.