| The Pengyang-Pingliang area locates in the southwestern margin of the Ordos Basin.in recent years,Triassic Yanchang Formation and the Jurassic Yan'an Formation reservoirs in the Mesozoic strata have been discovered in the east of Gansu Province,and they have been gradually developed.Based on the part of wells and the 2D seismic data,this study launch the analyze of Triassic and Jurassic of structure,deposition,formation and ancient landform.To research the controll factors and the distribution law of favorable traps in this area.Paper based on seismic and logging data,by making synthetic seismogram,well seismic calibration and reverse calibration,we achieved the unification of drilling stratification and seismic horizon,and analyzed the geological significance of seismic reflection mark layer.Based on the seismic and well logs reflection characteristics to analysis and interpretation key horizons.Yanan and chang7 formation can form four kinds of reflection features: Weak reflection,a peak and two valleys,a valley and two peaks and upper peak.The seismic reflection types and characteristics of the Yan'an Formation are related to the thickness of the stratum itself and the thickness of the coal bed,When the thickness is 40-60 m,which can form strong reflection characteristic of a peak and two valleys;When the thickness is 60-80 m,which can form strong reflection characteristic of a valley and two peaks;When the thickness greater than 80 m,which can form strong reflection characteristic of the upper peak and lower valley.Seismic reflection characteristics at the bottom of the chang7 are related to shale thickness,When the thickness is less than five meters,which can form weak reflection characteristic;When the thickness is five-ten meters,which can form strong reflection characteristic of upper valleys;When the thickness is ten-thriy meters,which can form strong reflection characteristic of upper peaks.The study area is close to the western margin thrust belt.It is strongly influenced by the late Triassic movement,which forms the characteristics of the highest in the northwest.In the end of the Triassic period,the strata were uplifted and denuded to form an unconformity of gully and ridges.According to the analysis of the two-dimensional seismic faults and the three-dimensional neighborhood study area,the research area is divided into three groups: NWW,NEE and NS.And the north-south fault is the western marginal thrust belt fault,with long extension and large fault distance.Other faults are reverse faults or vertical shift faults.The target layer of oil and gas wells in the study area are mainly located in the Chang 3 and Chang 4+5 of the Yanchang Formation,Through the analysis of seismic section,structural map and Yan'an formation residual thickness map,The vast majority of oil and gas production wells are related to the control of the residual paleotopography.The wells are located near the high and high points of the paleo-geomorphology and are controlled by the paleo-geomorphology.Only some oil production wells are controlled by the structure and lithology.The Yan'an formation residual thickness map has the most significant residual paleo-geomorphology in the reaction extension group,and it is more intuitive for oil and gas accumulation.The most production wells are located on the Yan'an Formation thickness reduction zone,during the migration of oil and gas to the northwest high parts,the reservoirs in the upper residual strata of the extension group are captured and aggregated,This reservoir,which is located high in paleo-geomorphism between the ancient valleys,actually belongs to the unconformity-reducing reservoir at the end of the extension group.Combined with the Chang 7 source rock thickness maps,tectonic maps,paleogeomorphograms and sand body distribution,it is possible to predict favorable trap-forming trap areas.This cognition has a certain guiding significance for exploration of the reservoir in this area... |
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