Basin-range coupling relationship and prediction of favorable targets for ultra-deep subsalt exploration in the Tarim Basin, Northwest China

Abstract

The Tarim Basin holds significant geological interest due to its complex basin-range coupling relationship and promising prospects for hydrocarbon exploration. The basal Cambrian in this basin records all tectonic movements of surrounding plates and influences the distribution of source rocks, reservoirs and caprocks. Its morphological evolution not only reflects changes of the uplift-depression framework but also indicates the migration pathways of hydrocarbons. Based on seismic profile interpretations, the structural morphologies of the basal Cambrian and active faults in various geological periods are obtained and related to regional plate tectonics. Furthermore, favorable targets for ultra-deep hydrocarbon exploration are predicted by identifying structural hinge zones. The results show that, (1) the initial amalgamation of the Tarim Plate with South Kunlun Terrane in the southwest at the end of the Middle Ordovician led to uplift of the Southwestern Depression, Bachu uplift, and Tazhong uplift, with the formation of NW-SE-trending boundary faults, (2) the amalgamations of the Tarim Plate with South Kunlun Terrane in the southwest, and Altun-Qilian Terrane in the southeast, as well as the bidirectional subduction of the South Tianshan Ocean in the north at the end of the Ordovician led to uplift of the Southwestern Depression, Bachu uplift, Tazhong uplift, southeastern basin, and Tabei Uplift, with the development of the Bachu-Tazhong fault system trended NW-SE, Madong back-thrust fault system trended NE-SW, and Tabei fault system trended E-W, (3) the amalgamation of the Qaidam Block and Tarim Plate in the southeast and the continued subduction of the South Tianshan Ocean in the north at the end of the Silurian led to uplift in the Madong structural belt, Gucheng low uplift, Tadong low uplift, Shuntuoguole low uplift, and Tabei Uplift, with a large-scale reactivation of the Madong back-thrust fault system and small-scale activities of the Bachu-Tazhong and Tabei fault systems, (4) the closure of both the North and South Tianshan Oceans in the Carboniferous and the intense uplift of the Tianshan orogenic belt in the Permian in the north, as well as the amalgamation of the Tarim Plate with Tianshuihai Terrane in the southwest, led to the development of the Tabei Uplift, Shuntuoguole low uplift, Awati sag, northwestern Bachu uplift, Tazhong uplift, and Southwestern Depression, with the strong activities of the Tabei and Bachu-Tazhong fault systems, and weaker activity of the Madong back-thrust fault system, (5) the amalgamations of the Tarim Plate with North Qiangtang Block, South Qiangtang Block, and Lhasa Block during the Mesozoic in the southwest led to uplift of the Southwestern Depression, Bachu uplift, Tazhong uplift, and Tadong low uplift, with the strong activity of the Bachu-Tazhong fault system, (6) the remote effect resulting from the collision between the Indian and Eurasian plates in the Cenozoic led to significant uplift of the Bachu uplift and varying degrees of subsidence in other basin areas, with intense fault activities in the southwestern, northwestern, and northern regions. Based on the distribution of Middle-Lower Cambrian source rock, reservoir, and caprock, the favorable targets for ultra-deep subsalt exploration include the central-eastern Tazhong uplift, central Lunnan low uplift, central Shuntuoguole low uplift, southwestern Markit slope, northwestern Yecheng sag, and northwestern Bachu uplift.