Influence Of The Upper Paleozoic Faults On Hydrocarbon Accumulation Conditions In The Northern Ordos Basin

Based on the understanding and absorption of previous exploration and research results,this paper integrates geology,earthquake,drilling,logging,remote sensing,gravity and aeromagnetic and other materials,applying modern structural geology,sedimentology,Geophysical and geochemical methods,based on the characteristics of fault system and its dynamic evolution,combined with the quantitative analysis of fault development characteristics and lateral sealing and the research results of various reservoir elements,to deeply understand the influence of the Upper Paleozoic faults on hydrocarbon accumulation conditions in the northern Ordos Basin,and improving the reservoir-forming modes associated with faults.First,using the identification of seismic sections and electromagnetic profile,combined with the Upper Paleozoic faults reflected by the anomalous regions on the gravity and magnetic data,the distribution of the basin basement fault zone identified by the aeromagnetic data and the response of the faults identified by remote sensing data on the surface,in the northern part of the basin.89 large faults were identified and divided into three categories according to the extension distance of the fracture.Three fault zones are defined on the plane according to the fracture direction.The profile characteristics of the fault are divided into two types: the active marginal type of the basin in the Hangjinqi area and the stable slope type in the basin of the Tabamiao area.The former is characterized by the Boerjianghaizi fault,the Wulanjilinmiao fault and the Sanyanjing fault.The segmental connection between the three main faults is dominated by soft joints,and the fault has the characteristics of inheritance development;The faults that develop in the southwestern part of the Tabamiao area are typical,mostly high-angle faults with small or no fault distance.Then,by analyzing the regional tectonic setting in the process of basin formation and evolution,and taking the three main faults in Hangjinqi area as the typical,the average growth index of fracture,the average drop of the fracture,the average activity rate and the average extension rate are calculated,and the balance of the trunk fracture is made.section.The results show that the fault tectonic evolution in Hangjinqi area has long-term,multi-period and cyclicality.The fault activity matches the regional tectonic background,and has experienced four scenes before and after,the long-term compression of the late Carboniferous Taiyuan-Late Triassic extension period,the extension of the Middle Jurassic Yan'an period-Duolu period,and the Middle Jurassic period.-Early Cretaceous extrusion,early Cretaceous extension.Finally,combined with the current oil and gas reservoir exploration results,the evolution process of the fracture structure affects the distribution and extent of sediment deposition,and the later activities of the fracture improve the reservoir properties after reservoir formation and form during the fault activity.A trap directly related to the fracture.The data of lateral sealing analysis shows that most of the fractured sections have good lateral opening and can be used as a passage for natural gas migration.The analysis of hydrocarbon generation,migration and accumulation process shows that there are two main ways of oil and gas accumulation related to faults.One is that natural gas is formed south of the fault,transported by the reservoir sand body to the fractured lower plate,and through the fracture.The channel acts to move to the trap of the upper disc.The other is that after the natural gas is formed in the Shanxi Formation and the Taiyuan Formation,it is transported to the Lower Shihezi Formation reservoir by the fracture channel.