Preliminary study of the relationship between the suspected mud diapir and natural gas hydrate in the Qiongdongnan Basin, Northern South China Sea

Based on the tectonic and deposition characteristics, regional geophysical survey as well as hydrocarbon exploration of Qiongdongnan Basin, the development and evolution, and distribution features of the suspected mud diapir, the relationship between the suspected mud diapir and natural gas-hydrate are studied. The results show that the suspected mud diapir, the gas chimney and natural gas-hydrate are mainly distributed in the conjunction area between uplifts and sags, as well as the central of sags, what's more, there are overlapping area in geography between suspected mud diapir and natural gas-hydrate. Biogenic gas and sub-biogenic gas derived from organic matter in shallow layer, as well as thermal gas derived from organic matter in deep strata accumulate in the temperature and pressure stable zone through the gas supply and migration and accumulation system which comprised the suspected mud diapir, the gas chimney, or faults and fractures, and natural gas-hydrate come into being, which show that gas supply system that is composed of suspected mud diapir and gas chimney has space-time coupling configuration relationship with accumulation of natural gas-hydrate. It is forecast that there are three accumulation models of natural gas-hydrate, including self-sourced diffusion biogenic gas and sub-biogenic gas accumulate in place by way of “self-generation and self-bearing”, foreign sourced thermal gas accumulate offsite through faults and fractures by way of “lower-generation and upper storage”, foreign sourced thermal gas accumulate in offsite place through mud diapir and gas chimney by way of “lower-generation and upper storage”. © 2015, Science Press. All right reserved.