Study On Heterogeneity Of Lacustrine Source Rocks And Evaluation Of Hydrocarbon Generation Potential

Study on heterogeneity of source rocks is not only the key to assess the hydrocarbon generation potential of an area,but also a hot spot of source rocks detailed evaluatio n.Yanchi-Dingbian Area is situated in the northwestern region in the Ordos Basin,far away from lake-basin center.Affected by source origin,primary productivity and so on,source rocks in this area have different organic geochemical characteristics and hydrocarbon generation potential with source rocks in deep lacustrine.This paper,taking the Chang-7 source rock of Yanchi-Dingbian Area in the late Triassic in Ordos Basin as a research object,based on well logging data,mud logging information,tested and analysed data,etc,emphatically discusses macroscopic heterogeneity of Chang-7 source rock in inorganic mineral and organic matter.The inorganic mineral heterogeneity is mainly manifested in inorganic mineral compositio n changes,while the lateral and vertical variations in abundance of organic matter,organic matter types,thermal maturity,embody the organic matter heterogeneity.And then,this article discusses the controlling factors about heterogeneity of Chang-7 source rock.On the basis of it,different hydrocarbon generation kinetic models are established in differe nt regions and their application to source rock evaluation.Taking the Well Yan 56 as an example,this paper is focused on analyzing the vertical variations in mineral composition.The general up-section increase in feldspar content is associated with a decrease in quaterz content and a slightly change between clay minerals and other minerals.Combining with the abundance of organic matter and hydrogen index,there are not significant correlation between clay minerals content,feldspar content,quaterz content and those parameters.The thickness of the Chang-7 Formation is reduced from southwest to northeast in the study area.Samples of the Chang-7 section have high organic matter abundances.Base on the evaluation standard of organic matter abundance for lacustrine source rocks,most samples of the Chang-7₃ interval show“very good”quantities of organic matter and hydrocarbon potential,being the most profitable interval among the Chang-7 interva ls.The organic matter is dominated by type?,with only a few samples in the type?.The thermal evolution stage of Chang-7 source rock in the study area reach the maturity stage,with slight variation in lateral.There is a strong positive correlation between total organic content and hydrogen index among analysed samples.The variation among inorganic minerals are largely influenced by sedimentary facies in study area;the paleoproductivity and source origin are crucial to the organic carbon accumulation;there isn't obvious relationship between the redox condition,clay content and the total organic carbon.Through detailly analyzing heterogeneity of source rock in the study area,differe nt hydrocarbon generation kinetic models established by Petromod Software in differe nt areas,are carried out to assess the total resources among the Chang-7 intervals.The total oil yield of the Chang-7 intervals is 19.71×10⁸ t.That making great and little contribut io n to the total resources is respectively the Chang-7₃ interval and the Chang-7₁ interval.In terms of hydrocarbon generation intensity among different the Chang-7 intervals,it is also reduced from southwest to northeast in the study area.