Chang 6 Gravity Flow Sand Body Structure And Prediction Of Dominant Sand Body In Heshui Area Of Ordos Basin

In order to study the sedimentary scale of sandy debris flow with different thickness and scale formed by deepwater gravity flow in the deep lake area and the superimposed structure of sand bodies.In this paper,the Chang 6 formation in the Heshui area of the southwestern Ordos Basin was selected,and the tight sandstone under the microscope was observed by casting sheet,scanning electron microscope and energy spectrum analysis.The dominant sand bodies were classified according to the type of sand body superimposed and the direction of stress.High pressure mercury injection,constant velocity mercury injection,and nuclear magnetic resonance were used.The technology analyzes the micro pore structure of dominant sand bodies in tight reservoirs.Combined with well logging,core,and physical data,the sedimentary microfacies,physical property distribution,and test data have finally been used to advantage the Chang 6 formation in the Heshui area.The distribution of sand bodies was statistic and favorable area predictions were made.A total of the following knowledge was gained:The Chang 6 reservoir in Heshui area has a variety of gravity flow sedimentary facies with different deposition modes.The most important is the lake floor fan deposition model from the northeast.The southwest has developed landslide deposits due to slope breaks mode.The rock types of Chang 6 reservoir in the study area are mainly feldspar sandstone and lithic feldspar sandstone,with low component maturity.After undergoing compaction,cementation and dissolution,the porosity is 9.46% and the permeability is 0.194 mD.It is in the middle stage of the middle stage A to the middle stage of the diagenetic stage B.It mainly develops the intergranular pore phases ofillite and chlorite cement,Illite and chlorite cement the dissolving phase.According to the thickness of sand body deposition and superposition,it can be divided into four major types: continuous superposition type,interval superposition type,lateral spike type and sand-mud interlayer type.The stress direction of the sedimentary sand body and the connection degree of each single sand body can be divided into stable type,swing type and migration type.Classification of different types of dominant sand bodies using high-pressure mercury pressure,constant-speed mercury pressure,and nuclear magnetic resonance technology.Among them,continuous and spaced-stack sand bodies have positive skewness in high-pressure mercury pressure;The larger the pore-throat radius ratio of the medium-dominant sand body,the larger the throat radius;the dominant sand body is in a right-biased bimodal shape in NMR.According to the plane sedimentary microfacies,physical property distribution,and favorable area prediction of Chang 6 reservoir,class I region,class II region,and class ? region are divided,and relevant analysis and evaluation are performed using test data.