Parasequence set division, lithofacies paleogeography and sandbody distribution of Donghe sandstone Member in Tarim Basin

Donghe sandstone is the most important hydrocarbon exploration horizon of marine clastics in Tarim Basin, which is widely distributed in the whole basin. To further solve sandbody correlation and sedimentary facies distribution in Donghe sandstone, this stratum was studied and explored as a set of sandbody. Using more than 110 wells in the whole basin and the seismic section of key regions, the Late Devonian-Early Carboniferous Donghetang Formation-Bachu Formation in Tarim Basin were divided as a sequence, and Donghe sandstone Member-bioclastic limestone Member was subdivided into I-IV parasequence sets with regional correlations, reconstructing lithofacies paleogeography and sandbody distribution with a parasequence set as the unit. Parasequence sets I-II are low stand system tract, and parasequence sets III-IV are transgressive system tract. The early low stand system tract of parasequence set I was restricted to the west part of southwestern Tarim Basin, dominated by shoreface-foreshore subfacies. The late low stand system tract of parasequence set II was located in the central and western of Tarim Basin, dominated by wide foreshore and shoreface subfacies; littoral foreshore-shore face subfacies are widely developed in the north Tarim-central Tarim-Bachu area, and the central Tarim Basin mainly shows shoreface-transitional zone subfacies; the southwestern Tarim Basin is dominated by offshore shallow sea mudstones. The deposition range of early transgressive system tract in parasequence set III expanded. North Tarim-Bachu area is dominated by littoral foreshore-shoreface subfacies, and littoral-facies sandbar is developed in the central Tarim Basin; the vast areas in the basin are dominated by offshore shallow sea subfacies mudstone. The deposition range of late transgressive system tract in parasequence set IV reached the maximum. The central Tarim Basin is dominated by wide carbonate platform facies, and restricted-semi-restricted platform facies are mainly developed in the southwestern Tarim. The northern Tarim is dominated by mixed shallow sea facies, and littoral coastal sandbars are developed in the Yuenan-Yangwu-Lungu well area. Sandbody distribution in Donghe sandstone in the whole basin is mainly controlled by sea level rise, paleohigh or ancient landform, provenance, etc., and the proposed model of sandbody distribution in the parasequence set framework provides guidance for and is also verified by production drilling.