China's conventional and unconventional natural gas resources: Potential and exploration targets

Abstract

A series of significant breakthroughs in exploring conventional and unconventional natural gas resources have been achieved in new strata and new domains. However, the quality of the increased reserves has declined with the entry of unconventional resources into the reserves sequence. Therefore, the potential of conventional and unconventional natural gas resources as well as important exploration regions of the remaining natural gas resources need to be clarified, and favorable directions need to be established. On the basis of oil and gas exploration results, discoveries in petroleum geology, and exploration data of the past 10 years acquired by PetroChina, an entire system of resource assessment for conventional and unconventional oil and gas resources has been established. The fourth round of resource assessment has been systematically executed. The results indicate that the total conventional natural gas resources of China are 78 × 1012 m3, which shows an increase of 8 × 1012 m3 over the results of the third round of resource assessment. Unconventional resources include four types of resources: tight gas, shale gas, coalbed methane, and natural gas hydrates. Among them, tight gas reservoirs make up 21.86 × 1012 m3 (Jiyang, Dongpu, Nanxiang, Subei, and others were excluded from the assessed regions). In addition, shale gas, coalbed methane, and natural gas hydrate reservoirs make up 80.21 × 1012 m3, 29.82 × 1012 m3, and 153.06 × 1012 m3, respectively. The remaining resources for onshore conventional natural gas are distributed mainly in four significant domains, which are lithology–strata (clastic rock), marine carbonatites, foreland thrust belts, and complex tectonic belts. Of these, marine carbonatites and foreland thrust belts are the dominant domains. The resources for offshore natural gas are concentrated mainly in three domains, which are offshore structures, organic reefs, and lithology in deep water. The total remaining natural gas resources in marine carbonatites, foreland, lithology–strata, complex tectonic belts, and the South China Sea amount to 59.83 × 1012 m3, which is 94% of the remaining natural gas resources in China. Based on this assessment, favorable targets are selected including 10 targets for conventional resources, 4 for tight gas, 4 for coalbed methane, and 6 for shale gas.