Abstract
The natural gas pool is made by the accumulation of natural gas originated from the decomposition of a large amount of dispersed organic mater in the sedimentary rocks. Generally the natural gas from a large gas pool has high percentage of CH4, C2, … and H2S. Ar in natural gas from Neogene Tertiary is mostly derived from atomosphere. In older sedimentary rocks a large amount of He is generated by radioactive decay from U and Th in rocks.
It is presumed that the reserve of a gas pool is large in case the ratioes of He/CH4 and He/Ar in natural gas are relatively small in connection with the absolute age of the gas producing sedimentary formations.
The writer supposes that the content of heavy hydrocarbon in a gas pool largely depends on the environment of deposition of the source rocks, and partly depends on the physical condition (such as temperatuae and pressure) given to those rocks.
Generally speaking, we can expect the existence of large natural gas deposits in the region which has been protected against the strong effect of the atomospheric circulation.
