Oil and gas geochemistry and petroleum systems of the Fort Worth Basin
Oil and gas geochemistry and petroleum systems of the Fort Worth Basin
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DOI：
10.1306/11030606014
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发表时间：
2007-04-01
期刊：
影响因子：
3.5
通讯作者：
Pollastro, Richard M.
中科院分区：
文献类型：
--
作者：
Hill, Ronald J.;Jarvie, Daniel M.;Pollastro, Richard M.
详细的生物标志物和轻烃地球化学证实，密西西比海巴内特页岩是德克萨斯州中北部沃斯堡盆地石油的主要烃源岩，尽管可能有其他来源的贡献。生物标志物数据表明，主要的生油巴内特页岩相是海相的，并在异常高压、强烈上升流、正常盐度条件下沉积。对两个露头样品和七口威尔斯井岩屑的分析表明，巴内特页岩有机相存在变异性，可能存在其他石油亚族。轻烃分析表明，一些储层中有明显的陆源凝析油输入，导致许多原油具有陆源和海陆混合轻烃特征。轻烃数据表明，一个次生的，凝析生成源相含有陆源或混合陆源-海相有机质。生物标志物分析未揭示的次生烃源岩的指示强调了整合生物标志物和轻烃数据以确定石油源岩的重要性。沃斯堡盆地的天然气是热成因的，似乎与来自巴内特页岩的石油共生，尽管有些天然气也可能来自石油裂解。同位素数据表明生物气的贡献较小。除了宾夕法尼亚弯曲群中的储层（其包含的气体跨越所观察到的成熟度的整个范围）之外，这些气体似乎是地层分离的，较年轻的储层包含较少的成熟气体，而较老的储层包含较多的成熟气体。我们不能排除沃斯堡盆地内的其他源单元（如史密斯威克页岩）是当地重要石油源的可能性。
Detailed biomarker and light hydrocarbon geochemistry confirm that the marine Mississippian Barnett Shale is the primary source rock for petroleum in the Fort Worth Basin, north-central Texas, although contributions from other sources are possible. Biomarker data indicate that the main oil-generating Barnett Shale facies is marine and was deposited under dysoxic, strong upwelling, normal salinity conditions. The analysis of two outcrop samples and cuttings from seven wells indicates variability in the Barnett Shale organic facies and a possibility of other oil subfamilies being present. Light hydrocarbon analyses reveal significant terrigenous-sourced condensate input to some reservoirs, resulting in terrigenous and mixed marine-terrigenous light hydrocarbon signatures for many oils. The light hydrocarbon data suggest a secondary, condensate-generating source facies containing terrigenous or mixed terrigenous-marine organic matter. This indication of a secondary source rock that is not revealed by biomarker analysis emphasizes the importance of integrating biomarker and light hydrocarbon data to define petroleum source rocks. Gases in the Fort Worth Basin are thermogenic in origin and appear to be cogenerated with oil from the Barnett Shale although some gas may also originate by oil cracking. Isotope data indicate minor contribution of biogenic gas. Except for reservoirs in the Pennsylvanian Bend Group, which contain gases spanning the complete range of observed maturities, the gases appear to be stratigraphically segregated, younger reservoirs contain less mature gas, and older reservoirs contain more mature gas. We cannot rule out the possibility that other source units within the Fort Worth Basin, such as the Smithwick Shale, are locally important petroleum sources.