Sand Body Architecture And Horizontal Well Parameter Optimization Of Tight Reservoir Of Chang 7 Member In Dongrengou Oil Block,Dingbian

In this paper,the Yanchang formation Chang 7 member of Triassic in Dongrengou oil block,Ordos Basin,was taken as an example to study the sand body architecture of tight reservoir of the shallow-water delta front.And the key parameters optimization of fracturing horizontal well based on the sand body architecture were explored by using the analog and modeling technology,combination of geological and engineering.Some conclusions were obtained as follows:?1?Dominant sedimentary microfacies distribution laws and basic reservoir characteristics of Chang-7 were defined in research area.The dominant sedimentary microfacies were underwater distributary channel and mouth bar,through core observation and well logging facies analysis,basing fine isochronous thin stratigraphic framework.And it mainly distributed in Chang 7_1-1,Chang 7_2-1 and Chang 7_3-1 thin layer.Three dominant microfacies plane combination types were summarized guided by the shallow-water delta deposition model,includes interlaced main underwater distributary channel,continuous mouth bar and single band end subaqueous branching channel.Experimental results show that it has strong heterogeneity,poor physical property and low fluid availability of the tight reservoir,with average porosity of 8.86%,average permeability of 0.668 m D,and average movable fluid saturation of 40.8%.The movable fluid mainly occurs in the submicron pore space with pore throat radius between 0.1?m and 0.5?m.?2?The sand body architecture characteristics of the tight reservoir in shallow-water delta front were systematically studied.Single sand body was identified by means of the electric measuring curve of dense well pattern,then 5 types of lateral boundary identification marks in subaqueous distributary channel single sand bodies and 3 types in mouth bar single sand bodies are summarized in total,according with the principle of"vertical staging,lateral demarcation and multidimensional verification".The identification marks will be used as the basis of architecture anatomy.The type of sand body architecture of the tight reservoir in Chang 7 member was firstly divided of Dongrengou oil block,according to the identification marks,based on the study and evaluation of dominant sedimentary microfacies.Including six types of isolated underwater distributary channel?R-I?,lateral stacked underwater distributary channel?R-II?,vertical stacked underwater distributary channel?R-III?,isolated mouth bar?MB-I?,lateral spliced mouth bar?MB-II?,and lower residual mouth bar upper river?R-MB?.The dominant target sand bodies of horizontal well are mainly the types of R-I,R-II,MB-I and MB-II.On the basis of fine characterization of the single sand body,the three-dimensional parameters of single sand body are quantitatively characterized,and the quantitative model of the main sand body architecture was established of the shallow-water delta front.The thickness of the subaqueous distributary channel single sand body is mainly distributed between 2m?9m,and the width is mainly distributed between 100m?350m,with an average width-to-thickness ratio of 45.The quantitative statistical relationship between the thickness?H?and width?W?was established,W=28.982×H+81.461.While the length and width of the mouth bar single sand body are mainly distributed between 3m?10m and 400m?1800m respectively,with an average length-to-thickness ratio of 191.The quantitative statistical relationship between the thickness?H?and length?L?was established,L=139.81×H^1.164.It can be used to predict the size of the single sand body in other areas with known sand body thickness,based on the established quantitative model.?3?An optimization method was established for determining the key parameters of fracturing horizontal well of Chang-7 in Dongrengou oil block,Dingbain.By optimizing the target sand bodies of horizontal Wells,considering the heterogeneity,rhythm of reservoirs and the geological characteristics of different architecture,the quantitative geological geometric models were established of three main types of sand body?A:isolated underwater distributary channel,B:vertically superimposed underwater distributary channel,C:isolated mouth bar?.Using the reservoir numerical simulation technology to optimize the key parameters of fracturing horizontal well in the research area,the optimization scheme was proposed,Further.And an optimization method for determining the key parameters of fracturing horizontal well was established of Chang-7 in Dongrengou oil block,Dingbian,for the first time.The recommended horizontal segment of horizontal well for class A is about 600m in length,100m in spacing between artificial fractures,and 80m in half-length of artificial fractures.And the recommended horizontal segment length of class B is about 700m,the artificial fractures spacing is 100m,the half-length of artificial fractures is 80m.And the recommended horizontal segment length of class C is about 900m,artificial fractures spacing is 100m,the half-length of artificial fractures is 80m.The above optimization scheme of the key parameters for fracturing horizontal well of main sand body,is helpful for effective development of the tight reservoir of Chang 7 member in research area.In conclusion,the key parameters optimization technology based on sand body architecture of fracturing horizontal well development is an important technical exploration for improving the fine development of oil and gas reservoirs and promoting the integration of geology and engineering.