The Reservoir Evaluation Of Lower Cretaceous In Helong-Lanjia Reversal Tetonic Belt,Dehui Fault Depression

The Helong-Lanjia reversal tectonic belt of Dehui fault depression is located in the southeast of Songliao Basin.The exploration area is about 400 square kilometers.The gas production of some exploratory wells has reached the level of industrial air flow,but the overall exploration level of the target layer is low.It is necessary to evaluate the reservoir of the target layer,and to find out the characteristics and distribution of the high quality reservoirs in each layer,so as to provide a favorable exploration target area for the oilfield development evaluation.On the basis of core observation,related logging data and stratigraphic calibration,the standard layer and standard well are established.Next we made stratigraphic division and comparison of the lower Cretaceous strata in the study area.Then we establish a comparative section skeleton network.To combine the logging data and seismic data,for making the layars in the study area perfectly integrated.At last,to complete the establishment of the fine stratigraphic model in the whole region.Through the fine interpretation of seismic data in the study area,to combine the structure and fracture,and reference to the regional geological background,to analyze the structure and fracture evolution of the study area from horizontal to vertical.It is recognize that the tectonic movement in the study area is generally weakening,but in the period of structural inversion was generally enhanced,in the vertical direction.And there are differences in activity intensity between different periods and different tectonic zones.Horizontally,the activity of the Buhai area is the strongest in the sedimentary period,and the weakest in the Lanjia area.The inversion is the strongest in the area of inversion,and the inversion degree is weaker in the Lanjia and Helong areas.It is found that the main facies of the lower Cretaceous are braided river delta,meandering river delta,fan delta and lacustrine facies,but only partial subfacies of each type are exist,through the comprehensive study of core observation,electrical relationship and seismic data.The braided river delta is the dominant facies,in which the distributary channel of the braided river delta plain and the subaqueous distributary channel of the braided river delta front are the main microfacies of the excellent reservoir in this area.According to the analysis of laboratory data,the diagenesis of the study strata is studied.It is found that the structural maturity and compositional maturity of rocks in the study area are immature.The main pore types are dissolved intergranular pores and dissolved grain pores.The throat is mainly micro and fine throat,and the coordination number of throat is very low.The physical property of the reservoir is controlled by various control factors.The depositional factors are the most important factors that affect the physical properties of reservoirs.The mechanical compaction during consolidation diagenesis makes the physical properties gradually worse.A part of diagenesis can improve the physical properties of reservoirs,while the other part will result in poor physical properties.On the whole,the effect of diagenesis is not significant.Faults and fractures generally only improve the physical properties of local reservoirs,but have little effect on the overall improvement.By using the K-means cluster analysis method and combining with the actual situation in study area,we select five parameters of porosity,permeability,shale content,sandstone thickness and sedimentary facies,for the comprehensive evaluation of the reservoir,and draw the map of the reservoir plane.We analyse the reservoir forming model,main controlling factors and the geological conditions of reservoir formation,and determine the evaluation index and predict the favorable zone,combining the exploration field and the exploration direction analysis.We found that the favorable reservoir area of the Shahezi formation is limited in the northwest and southeast of the study area,the Yingcheng formation is only scattered around the southeast of Deshen 35 well in the southeast and northeast of the study area,and the enrichment area is relatively limited,the Denglouku formation is relatively wide,and the dominant reservoirs are mainly distributed in the middle and southeast of the study area.