Structural Models in Ultra-Deep Layer of the Kuqa Salt-Bearing Fold-Thrust Belt, West China

Summary The Kuqa fold-thrust belt is a typical salt-bearing fold-thrust belt in the world with a great successful exploration of the natural gas in the subsalt layer which buried depth over 7000m. The total natural gas resource is over 2×1012m3. The substantial tectonic movements influenced the distribution and evolution of structural traps in the subsalt layer with strong and complex deformed structures such as salt tectonics, thrust, and fold systems. We build the structural models for KFTB from the supra salt layer to the basement, including Fold-thrust systems, salt tectonics, strike-slip fault systems, and paleo-uplifts, based on field observation, 2D/3D seismic data interpretation, deep drilling wells analysis, and analogue experiment. 4 tectonic layers were recognized, Paleogene salt layer and Paleozoic paleo-uplifts play an important role in layered, segmental deformation not only from orogenic belt to basinward but also from basin margin to basin center. Furthermore, the various deformation and evolution processes of the fault fracture systems and their influence on ultra-deep layer reservoirs were revealed for hydrocarbon exploration. Tensional fracture zones and accommodation fracture zones in a single faulted anticline are favorable places for natural gas exploration.