Sedimentary Microfacies And Single Sandboby Characterization Of Chang 611 Reservoir Group In Sai160 Dense Well Area Of The Ansai Oilfield,Ordos Basin

The Sai 160 dense well area of the Ansai Oilfield is a shallow water deltaic deposit,and the sandboby is dominated by channel deposition and mouth bar deposition,which has the characteristics of contiguous distribution.However,the poor correspondence between injection and production in the development process indicates that the internal configuration and stacking pattern of the contiguous sand body are complex.Based on modern sedimentation and numerical simulation,combined with core,logging and dynamic data,the sedimentary facies and sand bodies of Chang 611 oil-bearing formation in Sai 160 dense well area of Ansai oilfield are analyzed in detail.It is determined that the study area is a typical meandering river shallow water delta deposit,which develops four sedimentary microfacies : underwater distributary channel,mouth bar,sheet sand and tributary bay.The internal sand body configuration characteristics were clarified,the sand body evolution stages in the study area were divided,and a 3d geological model was established.Mainly made a few achievements and understanding :1.The sub-layer division scheme of Chang 611 oil-bearing formation in the study area was proposed.The single sand body stages of more than 180 wells in the study area were divided.The Chang 611 oil group was further divided into seven sub-layers : Chang6-1-1-2-1,Chang 6-1-1-2-2,Chang 6-1-1-2-3,Chang 6-1-1-2-4,Chang 6-1-1-3-1,Chang6-1-1-3-2,Chang 6-1-1-3-3.2.According to the data of core and logging curve,four sedimentary microfacies of distributary channel,mouth bar,sheet sand and tributary bay are identified in the study area.3.Determined to be the model of river-bar symbiosis according to the profile configuration,that is,a single river controls a single mouth bar.4.Using the idea of vertical staging and lateral demarcation,the architecture analysis of contiguous single sand body in the study area was realized.In the study area,six types of identification marks of delta front reservoir architecture boundary are established,namely,phase change,thickness difference,elevation,curve shape,oil and gas bearing property and progradation.The single configuration is tracked by profile tracking to determine the boundary of single configuration sand body.And summed up the study area sedimentary microfacies combination in the lateral and vertical 9 kinds of configuration superposition style.5.The quantitative knowledge base of configuration unit is established.A total of 212 single mouth bars were developed in the 7 small layers of the study area.The length of the mouth bar is distributed between 350.9-1428.3 m,with an average of 688.3 m;the width is distributed from 115.3 to 471.5 m,with an average of 254.9 m.The thickness distribution is 0.7-9.5 m,with an average of 4.2 m.The width of underwater distributary channel is 49-218 m,with an average of 103.1 m.Thickness distribution in 0.9-9m,an average of 4.4m.6.Combined with the production dynamics and architecture analysis results,the injection-production correspondence analysis and evaluation were completed.The analysis shows that after the water injection of the water injection well in the study area,the water often flows preferentially along the river channel,and it is difficult to spread to the mouth bar area on the side edge,forming a local high permeability dominant channel and water flooded area,which needs to be blocked.Because there is no injection well or no perforation in the well,the energy supplement of the oil well is insufficient,and the local remaining oil is enriched.The injection or perforation can be used to improve the injection and production system and improve the oil and gas recovery.7.The model of Chang611 oil group in Sai 160 dense well area of Ansai Oilfield is established by using the method of 2D section reconstruction of 3D model.The accuracy of the model is high after testing,and it also provides a reference for the subsequent oilfield development.Based on sedimentology and sequence stratigraphy,this study uses modern sedimentary correlation method and sedimentary numerical simulation method to determine the sedimentary model of the study area and dissect the configuration.The dynamic verification shows that the anatomical results are accurate,which provides guidance for the excavation of remaining oil in Ansai Oilfield.