Outcrop Field Geological Modeling In The 8 Member Of Shihezi Formation Of The Ordos Basin

Outcrop research is more intuitive,accurate,relatively complete and verifiable than underground.By selecting an outcrop which is comparable with the main gas bearing section of Sulige demonstration area,a geological model can solve the problem that can approximate the underground geological conditions can be established,the model to predict the scale and plane distribution of single genetic sand body in the case of large gas well spacing.The traditional sedimentary facies analysis mainly carries out the study of the size of the sedimentary microfacies association(the reservoir structure unit limited by the 5 stage configuration interface),which is less studied for the 3 and 4 level interface limited reservoir structural units.These low-level reservoir structural units have very important control action on the distribution and development effect of oil and gas.According to the above problems,the Fugu Tianshengqiao section is selected as the research area of this paper,the high resolution sequence stratigraphic study was carried out for the 8 Member of the Lower Shihezi Formation in Fugu Tianshengqiao section,and the isochronous sequence stratigraphic framework is established.In the isochronous frame,the architecture analysis of river facies sand body is carried out,and the combination of lithofacies and section structure is used to identify and divide the architecture elements of the outcrop section,and the spatial superposition mode is analyzed of the 8 sections of Shihezi Formation.Finally,a three-dimensional sedimentary microfacies model is established by using deterministic modeling.Through above work,the following conclusions have been made:(1)Through the observation and measurement of the outcrop section of the study area,the sequence boundary is identified and the sequence stratigraphic division scheme of the 8 Member of Shihezizu Formation of the Fugu Tianshengqiao section is determined according to the classification scheme of the base level cycle level of the continental basin.Taking the short-term cycle sequence as an isochronous stratigraphic correlation unit,the study area of 8 Member of Shihezizu Formation can be divided into 2 long-term cycles,4 medium-term cycles and 12 short-term cycles.(2)Through the geological survey of the 8 Member of lower Shihezi Formation of the outcrop in the study area,it is believed that the braided river deposits are developed in the lower 8 Member of Shihezi Formation and the upper 2 sections of 8 Member of Shihezi Formation,and the upper 1 section of the 8 Member of Shihezi Formation are deposited in the meandering river.There are 4 major categories and 13 small types of lithofacies.(3)In the isochronous frame,the architecture analysis of 8 Member of Shihezi Formation is carried out,On the basis of the identification of the sedimentary characteristics,according to the characteristics of the lithofacies combination and the profile structure,7 configuration units are identified,which are channels,the longitudinal bars,transverse bars,diagonal bars,point bars,Fall silt layer,and the flood plain deposit.The way of superposition of sand bodies is vertically distributed in the form of overlapping and lateral bridging.(4)By establishing the structural model of the sequence SSC8 in the study area,it is clear that the stratum is a monoclinic structural feature,and the north-east to south-west inclined stratum.On the basis of the division of the architecture unit of the outcrop section,the sequence SSC8 sedimentary microfacies model is established by the deterministic modeling method,which can clearly define the scale of the single sand body and the regularity of the plane distribution,and better reflect the spatial superposition relation of the sand body.