川东北地区三叠-侏罗系陆相烃源岩评价及油源对比

通过系统的有机地球化学分析, 对川东北陆相地层主力烃源岩进行了系统评价, 对油、源进行了精细对比, 查明了非常规油气的成藏特征。分析认为陆相地层须家河组、自流井组和千佛崖组发育大量有效烃源岩甚至优质烃源岩, 有机质丰度较高, 各地区各层系TOC平均值介于0.41%~2.99%之间, 有机质类型主要为Ⅱ, Ⅲ型, 处于成熟?过成熟阶段(Ro介于 1.3%~2.0%之间), 具有良好的生烃潜力, 可成为该区中、下侏罗统 非常规油气的主力烃源岩。经油源对比及成藏特征分析, 发现中、下侏罗统陆相非常规油气来源于陆相烃源岩, 未显示海相油气来源, 说明由于陆相储层异常致密, 导致油气运移困难而源内或近源成藏。其中, 元坝?阆中地区千佛崖组的油气来自于自流井组烃源岩, 自流井组的油气来自于自流井组及须家河组两套烃源岩。宣汉?达县地区的油气来自于须家河组烃源岩。下侏罗统泥页岩具备页岩气形成的条件, 中、下侏罗统致密砂岩具备致密砂岩油形成的条件。

Evaluation of Terrestrial Hydrocarbon Source Rocks and Oil Source Correlation in Triassic and Jurassic in Northeastern Sichuan

Through systematic organic geochemistry analysis, the main hydrocarbon source rocks of terrestrial formation in northeastern Sichuan are systematically evaluated, sources of oil are determined by carefully comparison of geochemical characteristics between source rocks and oil, and accumulation characteristics are identified. Analysis results indicate that terrestrial formations, such as Group Xujiahe, Ziliujing and Qianfoya, develop vast effective, even rich source rocks with high organic matter abundance, and the average TOC values of different districts and groups range from 0.41% to 2.99%. Type Ⅱ and type Ⅲ are widely distributed, and source rocks are high mature to over mature with Ro ranging from 1.3% to 2.0%. Generally, hydrocarbon source rock of terrestrial formation in northeastern Sichuan has high hydrocarbon generation potential, which could be favorable main source rocks of middle and lower Jurassic terrestrial unconventional oil and gas in research area. Comparison of geochemical characteristics between source rocks and oil and accumulation characteristics analysis demonstrate that middle and lower Jurassic terrestrial unconventi onal oil and gas are generated from terrestrial sources with few marine sources, which proves that oil and gas migration difficulty caused by the extremely tight terrestrial reservoirs leads to in-source or near-source accumulation. Oil and gas in group Qianfoya are from Ziliujing source rocks and that in group Ziliujing are from both Ziliujing and Xujiahe source rocks in Yuanba-langzhong. Oil and gas are all from Xujiahe source rocks in Xuanhan-daxian. Lower Jurassic shale can fill the requirements for shale gas, while middle and lower Jurassic tight sandstone can fill the requirements for tight sandstone oil.