Controlling factors for large gas field formation in thrust belt of Kuqa coal derived hydrocarbon fo

Kuqa depression is a foreland basin developed with Mesozoic-Triassic-Jurassic coal-bearing formation. The research results of the coal-derived hydrocarbon foreland basins in Kuqa depression indicated that the coal-bearing formation can be the rich sources for generating gas because of their thickness and rich source rocks with gas-generating predominant kerogen. Although the foreland thrust belt mainly acting in compression is very complicated, integral large structural traps can be formed. Moreover, the thrust belt can act as the passage for communication with deep source rocks. The high quality gypsolish and gypseous mudstone cap rock developed in the upper formation is the key for the formation of the large gas field. The late formation of reservoirs in the large gas fields depended on the hydrocarbon-generating history controlled by the foreland basin and the developing process of foreland thrust belt.