Sedimentary facies of the Chang6-Chang10 intervals in Heshui-Ta’erwan area, Ordos Basin

Abstract：Genetic types of sedimentary sand bodies affect oil and gas exploration in the Heshui-Ta’erwan area of Ordos Basin. Based on outcrop and core characteristics analysis, combined with well logging data, the authors recognized various types of sedimentary facies of the Chang6-Chang10 intervals in the study area, i.e., normal delta, braided delta, lacustrine system and slump fan, and made a detailed discussion on the subfacies. The turbidite and sandy debris flow sediments are the major gravity flow deposition systems. The primary braided delta deposits came from the southwest, the minor normal delta deposits came from the northeast, and the slump fan developed in the middle. The study area experienced transgression and regression during the deposition of Chang6-Chang10 intervals. The southwestern braided delta kept retrograding and slump fan developed in the front in deep water ultimately. The northeastern normal delta deposits are found mainly in the Chang6 and Chang8 intervals. It is revealed that source rocks developed in the Chang7 interval, and both underwater distributary channels in the Chang6 and Chang8 interval and gravity flow sediments in the Chang7 and Chang6 interval are potential exploration targets.