Abstract: Kelameili gas field with reservoirs of about 100 billion cubic meters was found in Dinan swell, but in Dibei swell just small scale gas pool is found now and no great breakthrough has been made. The comprehensive evaluation of source rocks indicates that its Carboniferous source rocks with wide distribution, high organic matter abundance and high maturity should be of more intensive hydrocarbon generation potentials. The source rocks of Dishuiquan formation of Lower Carboniferous are dominated by II2-III organic matter types, while Batamatineishan formation of Upper Carboniferous by III type. The study suggests that natural gas in Dibei swell should come from the Carboniferous source rocks characterized by high revolution degree and mixed with autochthonous gas or lowmaturity gas from Jurassic coal measures near the reservoir. It is this that brings about heavier ethane carbon isotope and lighter methane carbon isotope in Jurassic gas. The source rocks of upper part of the Carboniferous in Dibei swell are in low maturity, reflecting its hydrocarbon should come from the source rocks in the Carboniferous in Dibei swell deep and Beimian sag deep.

Key words: Junggar basin, Dibei swell, source rock, natural gas