Research On Heterogeneous Distribution And Major Controlling Factors Of Hydrocarbons In Tanan Depression,Tamsag Basin

Hydrocarbon heterogeneous distribution is the universal law in oil and gas bearing basin,further research on the heterogeneity and controlling factors of the distribution of hydrocarbon,especially figuring out the heterogeneous distribution of hydrocarbon in complex reservoir by detailed description of reservoir,may provide evidence for fine exploration,rolling development and reservoir evaluation.Overall,it has great significance on the improvement of exploration and development comprehensive benefits.In view of the existing problems in rolling exploration and development of Tanan depression,based on the fine dissection of proven reservoir,this paper depicts a systematic summarization of hydrocarbon distribution features in several scales,and presents a deep analysis of the controlling factors of different scales of the hydrocarbon heterogeneous distribution.Consequently the pattern of hydrocarbon heterogeneous distribution is established,and conduct the rolling exploration and development.The hydrocarbon heterogeneous distribution in Tanan depression has several scales,and different scales of hydrocarbon heterogeneous distribution have different expressive characteristics.The characteristics of hydrocarbon heterogeneous distribution in the scale of depression mainly presents as the difference among the hydrocarbon distribution,the degree of hydrocarbon enrichment and reservoir types in different oil bearing series in the vertical direction and different zones in the horizontal direction.The characteristics of hydrocarbon heterogeneous distribution in different fault blocks mainly presents as the difference among the oil-bearing area,reserve scale,reserve abundance and oil well productivity.The characteristics of hydrocarbon heterogeneous distribution in fault blocks mainly presents as the petroliferous difference between interlayer in the vertical direction and layers in the horizontal direction.The hydrocarbon heterogeneous distribution in the scale of depression is controlled by hydrocarbon,fault structure and sedimentary system.Based on the comprehensive analysis of source rock thickness,organic matter abundance,organic matter type and degree of thermal evolution of organic,it is clear that the distribution of effective source rock in Tanan depression,the heterogeneity of effective source rock controls the difference between hydrocarbon enrichment in different oil bearing series in the vertical direction and the planar hydrocarbon distribution pattern.Based on the research of characteristic of faulted structure in Tanan depression,this paper concludes that the difference of structural development and evolution of various structural belts controlled the difference of tectonic deformation and structural styles,which ultimately determine the trap and reservoir types in different zones.The matching relationship between fault active stage and hydrocarbon generation and expulsion period controlled the vertical accumulation layer system and hydrocarbon enrichment degree.Besides,this paper makes clear the types and distribution of sedimentary systems in different oil bearing series of Tanan depression,and the sedimentary system determines the development degree and the distribution law of the reservoir,moreover it also controls the reservoir size and distribution.The hydrocarbon heterogeneous distribution between the fault blocks is mainly controlled by fault sealing ability and difference of reservoir facies as a result of sedimentary micro-facies and diagenetic facies.The lateral sealing capacity of faults is evaluated by SGR and faults displacement pressure.It is shown that fault sealing ability determines the effectiveness of traps,and then affects the difference of hydrocarbon-filling degree between the fault traps.Due to the difference of the distance to sedimentary source,hydrodynamic condition and the environment of tectonic and diagenesis evolution,there is much difference about sedimentary micro-facies,lithofacies,diagenesis and diagenetic facies between different fault blocks in Tanan depression.The different sedimentary and diagenetic facies decide the difference of reservoir space type,microscopic pore structure and reservoir physical properties in fault blocks,and then control the difference of hydrocarbon enrichment and oil well productivity.Reservoir heterogeneity is the main factor affecting the hydrocarbon heterogeneous distribution in fault blocks.It is shown that inter-layer heterogeneous influence the inter-layer different enrichment by the heterogeneity experiment.Plain heterogeneity affects the different enrichment on the plain so that there is higher oil and gas abundance and oil well productivity in areas of higher reservoir quality index.Microscopic pore structures affect the difference of oiliness in reservoir and the formation and distribution of oil-water transitional zones in low permeability and tight reservoirs.On basis of the summary about heterogeneous distribution characteristics and major controlling factors,the heterogeneous distribution pattern of hydrocarbon between different fault blocks in Tanan depression was established.It includes the independent distribution pattern of outside-source conventional reservoir controlled by faults,the continuous distribution pattern of outside-source tight reservoir controlled by sedimentary facies and diagenetic facies,the continuous distribution pattern of inside-source tight reservoir controlled by sedimentary facies and diagenetic facies,the overlaying distribution pattern of near-source composite reservoir controlled by inter-layer heterogeneous.Potential area of progressive exploration was put forward and the precise reserve evaluation on the proved fault blocks was carried out which would be useful to guide the efficient rolling development of Tanan oilfield.