Microfacies characteristics and depositional evolution of typical wave-dominated littoral deposits – A case of Carboniferous ‘Donghe sandstones’ in Hudson Oilfield, Tarim basin, NW China

Hudson Oilfield, which located in the northern Uplift of Tarim Basin, is considered to be the largest whole-shaped oilfield in China, and the extensive Carboniferous 'Donghe sandstones', one of the most important marine sandstones units for oil and gas exploration in Tabei Uplift, constitutes the main reservoir. However, not all this sandstones are with good physical properties, and hence, the sedimentary characteristics and depositional evolution is believed to be critical to prediction of reservoir. It is determined that wave-dominated clastic littoral deposits with no barrier are the main depositional environment based on the modern sedimentary theory and related data analysis including ancient landform characteristics. And transitional zone, shoreface, foreshore, backshore and dune are considered as the five subenvironments. Through data of high resolution dipmeter logging and imaging logging, different sedimentary structures and other facies marks observed from cores of research regions are demarcated, and thirteen microfacies are further identified. Based on the detailed microfacies types, the evolution process of Carboniferous 'Donghe sandstones' can be divided to four main periods, in which, early highstand systems tract (HST) deposits in Period 1-2, and late HST deposits in Period 3-4.