The geology of natural gas in the People's Republic of China: A review

Commercial accumulations of natural gas in China have been generated by mar ine carbonates in Proterozoic and Palaeozoic cratonic basins, and by lacust rine shales and coal measures in Mesozoic-Cenozoic continental basins. Thes e accumulations occur in reservoir rocks of various types. The Chinese natu ral gas industry lias developed rapidly over the past two decades, and prov ed reserves of gas have increased accordingly. To date, 138 gasfields and 1 10 gasfields with oil-rims have been found in China. Based on its geological and geochemical characteristics, natural gas can be divided into three principal types: (i) biogenic (bacterial and biodegrade d) gas::(ii) wet associated gas, sourced from either sapropelic or humic or ganic matter; and (iii) dry thermal gas, likewise sourced from sapropelic o r humic OM. Each type of gas has its own characteristics in terms of generation, migrat ion, accumulation and distribution. Bacterial gas is concentrated in Quater nary strata for example, in the Qaidam Basin of NW China; biodegraded,gas o ccurs in shallow strata in the eastern oil provinces, often in association with tar mats. Associated gas occurs mainly in Mesozoic-Cenozoic continenta l basins, whereas dry thermal gas is generally confined to Proterozoic and Palaeozoic cratonic basins, especially in West China. Proterozoic and Palae ozoic gas resources make up about one-half of the Chinese total, and are se t to become a major exploration target in the future.