陆相湖盆沉积有机质富集机理研究进展

有机质富集机理的研究对于寻找优质烃源岩、评价盆地的含油气远景具有重要的意义,尤其在日益受到人们重视的页岩气、致密气、油页岩等非常规资源的勘探开发影响下,其研究就显得愈来愈重要和紧迫。而有机质富集机理总体研究程度并不高,对于陆相湖盆有机质的研究相对更为薄弱。以陆相湖盆为研究对象,开展大量国内外关于有机质富集机理的调研,从有机质的生产、有机质分解与保存、有机质的稀释作用三个方面系统总结了陆相湖盆有机质富集的控制因素,并对湖泊与海洋有机质形成的差异性进行了对比分析。研究表明,湖盆有机质的生产受地区光照率、营养盐供给、湖盆地貌、气候环境、湖泊水介质条件、藻类季节性勃发、自养型细菌等的影响;有机质分解与保存受水体分层、细菌生物、无机矿物、水介质条件、黏土矿物、沉积速率等的影响;有机质的稀释作用受沉积速率的影响,并最终得出湖盆中有机质的含量实际上是“有机质生产-有机质分解-有机质稀释”三者相互作用的结果。提出今后值得进一步关注和亟待深入研究的两个方向:自养型细菌在何种环境条件下可以创造高有机质生产力以及不同的水介质条件对有机质分解与保存的影响。

Research Progress of the Enrichment Mechanism of Sedimentary Organics in Lacustrine Basin

The research of enrichment mechanism of organic matter has great significance in exploring high-quality hydrocarbon source rock and evaluating oil and gas potential in a basin, which becomes more and more important and urgent under the great influence of the exploration and development of unconventional hydrocarbon resources such as shale gas, tight gas and oil shale. However, the overall research degree of organic matter enrichment mechanism is not high, and the research of lacustrine organic matter is relatively lower. With terrestrial basin as the object of the research, based on a detailed investigation of organic matter enrichment mechanism, this paper summarizes systematically the main controls on organic matter enrichment of terrestrial basin from the following aspects including organics production, organics decomposition and preservation, dilution effect of sedimentation on organics, furthermore, the differences of organic matter formation between marine and terrestrial basin are compared and discussed. The research indicates that lacustrine organic production is affected by area illumination rate, nutrient supply, basin topography, climate, aqueous media conditions, seasonal blooming algae, and autotrophic bacteria, etc.; lacustrine organic decomposition and preservation is subject to water stratification, bacterial biomass, inorganic mineral, aqueous medium condition, clay minerals, sedimentation rate, and so on; lacustrine dilution effect of sedimentation on organics is influenced by sedimentation rate. Finally, the paper makes a conclusion that total organic matter content of a terrestrial basin is actually a mutual interaction result of “organics production-organics decomposition-organics dilution”. At the end of this paper, two research areas worthy of paying more attention and in-depth study of this area in the future are put forward, which include, in what condition can autotrophic bacterium yield high productivity, and the impacts of different aqueous medium conditions on organics decomposition and preservation.