Study On Chang 8 Sedimentary System And Sand Body Distribution Of Yanchang Formation In Pengyang-Hudong Area

The Yanchang Formation in the southwest of the Ordos Basin has very rich oil and gas resources and is the main area for increasing reserves and production in recent years.It is of great significance to clarify the basin sedimentary system and sand body distribution rules for future oil and gas exploration.On the basis of regional geological background analysis,this paper uses core thin section data,field outcrop profiles,geochemical data and other basic data,according to the latest theories such as sedimentology,sedimentary petrology,paleontological stratigraphy,mineral petrology,etc.,combined with the latest research area.Based on the research results,the study area was finely compared and divided,and the vertical and horizontal characteristics of the stratum were clarified.Through the analysis of light minerals,rock fragments,heavy mineral assemblages,paleo-flow direction,and rare earth element distribution model,the main provenance supply direction of the study area is determined;on the basis of the description of petrological characteristics,combined with the regional tectonic evolution background,the sedimentary system is clarified and divided Sedimentary microfacies,and then analyze the characteristics of sedimentary facies and each microfacies from single well to continuous well to plane distribution;through fine identification and characterization of single sand body,vertical and horizontal comparison of composite sand body,description of sand body plane distribution characteristics,and then The sedimentary facies system and sand body distribution characteristics of Chang 8oil layer formation in the Pengyang-Hudong area are clarified.The results show that the Chang 8 oil layer group in the Pengyang-Hudong area contains 2 to 3 secondary cycles,and the stratum can be subdivided into two sub-members,Chang 8₁and Chang 8₂,and the thickness of each layer in the study area is relatively stable;The Chang 8 oil layer group is affected by two main provenances,the southwest-trending Longxi ancient land and the Qinling fold belt,the western corridor area and the near-proven sea source paleo-uplift;the Chang 8 oil layer group in the study area mainly develops a set of shallow-water braided river deltas Sedimentary,braided river delta sedimentary facies can be further subdivided into two sub-facies of shallow water braided river delta plain and shallow water braided river delta front.The corresponding sedimentary model map of Chang 8;the overall distribution trend of the sand bodies of the Chang 8 oil layer group in the study area shows the characteristics of converging from the southwest and west directions to the northeast of the study area.There are 9 main sand bodies in Chang 8₂.There are 10 main sand bodies developed in Chang 8₁.The overall thickness of the sand bodies in the study area is relatively large,and the sand bodies have good connectivity.Chang 8₁and Chang 8₂have good inheritance.The study of the study area is expected to provide reliable geological basis for finding favorable reservoir sand bodies in Chang 8 oil formation in Pengyang-Hudong area.