Accumulation Mechanism And Enrichment Law Of Chang7 Tight Oil In Huai Shu Zhuang Area,Ordos Basin

In order to deeply study the enrichment law and accumulation mechanism of the Chang 7tight oil of the Triassic Yanchang Formation in the Huaishuzhuang area of the Ordos Basin,based on previous research results,this paper uses geological,well logging,core,geochemical analysis and other data,It mainly conducts comprehensive research from the aspects of source rock characteristics,oil-gas accumulation time and tight coupling relationship of reservoir,migration mode and direction,and enrichment conditions.The main achievements and understandings are as follows:The average thickness of Chang 7 source rock in Huaishuzhuang area is 45 m;the total organic carbon?TOC?mass fraction averages 5.94%;the hydrocarbon generation potential?S₁+S₂?averages 13.1 mg/g;the organic matter types are?and?₁The main type of source rock is mainly low-grade aquatic organisms and contains some higher plants.The water body is a reducing environment when deposited;the reflectance of vitrinite is 0.76%on average,and C₃₁1 hopane 22S/?22R+22S?,20RC₂₉???/????+????and???C₂₉20S/?20S+20R?averaged0.52,0.62and0.49,respectively,reflecting the evolution of organic matter into the oil generation peak.On the plane,the central and northwest ministerial 7 source rocks in Huaishuzhuang District are thicker and have stronger hydrocarbon generation capacity.Based on the correction of the organic matter content of the Chang 7 source rock,the combined logging curve method,sonic-density intersection chart method,and porosity identification method were used to identify the cause of the paleo-overpressure in the Yanchang Formation.The main reason for the abnormally high pressure in the Chang 7 oil layer group is hydrocarbon-generating expansion,and the undercompaction has no obvious characteristics in this area.Combined with the analysis of burial history,it is believed that the source rocks of Chang 7 Member in Huaishuzhuang area have experienced the pressure evolution process of"tight reservoir formation-hydrocarbon source pressurization and overpressure formation-high-quality reservoir pressure relief".The secondary migration force of Chang 7 tight oil is mainly the conduction of the abnormal pressure generated by the supercharging of hydrocarbon generation in the reservoir,and the migration resistance is mainly the capillary resistance of the tight reservoir.The oil and gas migration channel is a sandstone transport system controlled by pores and micro-fractures,and macro-fractures play little role in the migration of the Chang 7 oil layer.The uniform temperature distribution of inclusions is between 95 and 130?,and it is in the form of a single peak and a broad peak.The history of single well burial thermal evolution and the history of reservoir compaction reveals that Chang 7 tight oil is first dense and then accumulates,which is manifested as a vertical and short-distance lateral migration of the lower-generation and upper reservoirs.The oil and water distribution characteristics of Chang 7 tight oil are complex,the oil moisture difference is not obvious,and there is no bottom water.The reservoir type is mainly tight lithological reservoir;the enrichment law of Chang 7 tight oil is controlled by the source rock,sand body distribution,Reservoir properties and interlayer distribution;among them,the source rock has a certain effect on the enrichment of Chang 7 tight oil;the thickness of the sand body is positively correlated with the thickness of the oil layer,indicating that the thickness of the sand body is the main controlling role of the Chang 7 tight oil.;Reservoir physical properties and oil level display also show a positive correlation,indicating that the reservoir physical properties are also the main control factor for the enrichment of Chang 7tight oil;the interlayer interlayer plays a local plugging role,so that Chang 7 tight oil can be Geo-rich accumulation is also one of the main controlling factors for Chang 7 tight oil.