Abstract:

By contrast and analysis of natural gas composition and carbon isotope characteristics between high temperature and high pressure(hthp) zone of middledeep strata,normal pressure zone and pressure transition zone of shallow strata in the central diapir district, and combined with the feature of diapiric activity, natural gas accumulation process and its composition distribution discipline are studied in this paper. The results indicate that, controlled by the intensity of diapir activity, natural gas accumulation process is much different from the D1-1 diapir core to diapir affected areas. The accumulation process at diapir cores was early accumulation, late destruction and refilling, while when it get to diapir affected areas, this phenomenon presents early accumulation but slight late destruction, and thus, diapir affected areas had perfectly preserved early filled mature coaltype natural gas. Furthermore, the distribution of natural gas composition and carbon isotope from diapir core to diapir affected areas is also well-regulated. With the increase of distance from diapir cores, the content of methane increases and carbon dioxide decreases, and carbon isotope of both methane and carbon dioxide decrease (maturity decreases) too. Obviously, it dominantly had accumulated rich organic caused CO₂ in diapir affected areas while inorganic caused CO₂ in diapir cores.

Key words: gas filling process, high temperature and high pressure zone, D1-1 diapir district, Yinggehai Basin