Depositional Evolution and Microfacies Characteristic of the Carboniferous Donghe Sandstone in Hudson Oilfield
Hudson Oilfield located in the northern uplift of tarim basin is the largest whole-shaped desert oilfield in China, with a main reservoir of the carboniferous donghe sandstone. Combined with modern sedimentary theory, data analysis and the ancient landform characteristic of research area, determined that the depositional environment of the donghe sandstone is wave-dominates shoreline deposits with no barrier. Shoreface, foreshore and backshore were considered as three sedimentary subfacies of this depositional environment. Twelve major sedimentary structures observed from core of research region were demarcated through high resolution dipmeter logging and imaging logging data. According to these twelve major structure and other facies marks, identified nine microfacies. Sedimentary evolution of donghe sandstone can be divided into four periods. Early HST deposited in period 1-2, and late HST deposited in period 3-4. The relative sea level initially rose in the first period, when foreshore and backshore successively deposited towards land of the area (NE). Foreshore beach was made up of beach ridge and swale. It was mainly affected by water erosion and of relatively higher maturity of architecture and compositional. Backshore was made up of beach dam and backshore beach, facies distributed paralleling to the shoreline; normal and storm deposits made up backshore beach. The second period was the main rise period of relative sea level. Large size of shoreface appeared in the southwest of research area, foreshore and backshore moved towards land. End of the second period, the maximum flooding surface occurred and shoreface distribution range reached its peak. The shore facies had a zonal distribution along the ancient coast zone. The third period was the initially descent period of the relative sea level, sedimentary facies began to migrate towards sea (SW); the fourth period was the main decline period of the relative sea, sedimentary facies continue seaward migration, at the same time erosion happened in the original side towards land, and erosion area appeared in the northeast and southeast. End of the fourth period, falling range of sea level reach the maximum and distribution range of shoreface, foreshore and backshore decreased. Sedimentary facies reached the maximum degree of migration towards sea, while erosion range reached the maximum in the study area. Only part of donghe sandstone remained in the west part of the research area.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014