Accumulation conditions, key exploration and development technologies for Keshen gas field in Tarim Basin

The Keshen gas field is located in the central part of Kuqa depression in Tarim Basin, and is another large gas field discovered after Kela2 gas field. Since the breakthrough in 2008, a number of large and medium scale gas reservoirs including Keshen2, Keshen5 and Keshen8 have been discovered in Keshen gas field. These gas reservoirs are characterized by ultra-depth, ultra-high pressure, ultra-low porosity and permeability, high temperature and pressure. With natural gas geological reserves of nearly trillion cubic meters and production capacity of nearly 100×108m3, the Keshen gas field is the main natural gas producing area in Tarim oilfield. The Keshen gas field is located in imbricate thrust structures in the Kelasu structural belt of Kuqa depression. Its structure includes the supra-salt overburden, the ductile salt rheological layer and the large wedge-shaped thrust body composed of the pre-salt faulted anticline group. The thick delta sandstones of Cretaceous Bashijiqike Formation are widely distributed in Keshen gas field, which formed the superior reservoir-caprock assemblage with the overlying Paleogene thick gypsum-salt bed. Oil and gas in Triassic and Jurassic source vertically migrate along the fault system in Late Himalayas, break through the thick Cretaceous mudstone, and laterally transported along the fracture system of the pre-salt reservoirs, thus forming anticline and fault-bend high-pressure reservoir groups. The three-dimensional seismic acquisition and processing technology for complex mountain areas, the compacted salt-related structural modeling technology, and the fractured low-porosity sandstone reservoir evaluation technology have laid a foundation for the implementation of exploration targets in Keshen gas field. Logging acquisition and evaluation technology for high temperature, high pressure, ultra-deep and low-porosity sandstone gas reservoirs, and efficient development technology for fractured tight sandstone gas reservoirs provide technical supports for efficient exploration and development and rapid production of Keshen gas field. © 2021, Editorial Office of ACTA PETROLEI SINICA. All right reserved.