The positive prospect of coal-derived gas in the Yingjisu Sag, Tarim Basin, China

摘要

Coal-derived gas determined by stable carbon isotopes were found in Well HYC 1 in the Yingjisu Sag, which brings a new dawn for gas exploration in this sag. Thermal maturity of the source rocks ranges 0.50%–0.65%. According to the traditional views that industrial oil/gas accumulations can only be formed if the thermal maturity of the source rocks is over 0.70%, so the recoverable resources of coal-derived gas were only 24.5?×?109?m3, and there was no drilling in the last 15 years. TheTOCvalues of the Jurassic coal-measure mudstone, carbonaceous mudstone, and coal in the Yingjisu Sag are similar to those in the Kuqa Depression. Both of them belong to medium quality source rocks; hence the potential of gas generation and accumulation is good. In the Yingjisu Sag, the Jurassic residual thickness is 1000–2000?m. The distribution area with the maximum thickness of coal is basically overlapped with the distribution areas with the maximum thickness of carbonaceous mudstone and dark mudstone. The continuous distribution area is about 8000?km2, which should be the richest and the most favorable exploration area for the coal-derived gas resource, wherein gas fields will be discovered in the future.