Research On Hydrocarbon Accumulation Rule Of Chang 6 Extra Low Permeability Reservoir In X13 Well Area Of Zhidan Oilfield,Ordos Basin

The paper taking the Triassic Chang 6 oil reservoir set in X13 well area of Zhidan oilfield as the research objective.Guided by geological theories and made full use of the data of logging,drilling,experimental analysis,logging display,well testing and early production test to study the characteristics of Chang 6 extra low permeability reservoir.After fine division and then contrast the formation to establish the stratigraphic frame of this area.To summary the characteristics of the formation and the evolution characteristics of the structure.Summarize the types of sedimentary micro facies and extension of sedimentary facies belt.Research on the physical characteristics of the reservoirs and the distribution characteristics of the cap rock to find out the dominant region of the reservoir and the most developed area of cap rock.After finishing these work,combined with its basic geological conditions to find out the distribution characteristics of oil and gas in space and to summary the main controlling factors of oil and gas enrichment.The results show that the formation in this area are completed and stability.The altitude of the east formation is higher than the west formation.Nose-shaped uplift and domal structure developed in some areas and the structural evolution is inherited.The Chang 6 reservoir located in delta front sub-facies,it can be divided into four sedimentary micro facies:underwater distributary channel,mouth bar,distal bar,underwater interdistributary bay.In this area,material source comed from NNE direction.The reservoir is mainly composed of fine sandstone and with low permeability and poor physical property.It belongs to extra low permeability reservoir.The oil reservoirs in Chang 6₁ and Chang 6₂ formation are well developed,but Chang 6₄ reservoirs are poor.The distribution of reservoir is strictly controlled by the sedimentary facies.The area with good physical property is mostly concentrated in the area of main sand body,most oil and gas enrichment areas are concentrated in the good area of the reservoir property.Sedimentary facies and reservoir physical property are the main controlling factors of oil and gas enrichment.Nose-shaped uplift can direct the area of oil and gas enrichment very well,the lateral blocking effective of the cap rock can contribute to accumulate oil and gas in reservoir.