Hydrocarbon generation characteristics and signification of source rock in different oil-rich depressions in the eastern part of the Bohai Sea

Abstract

There are numerous oil-rich depressions in the eastern part of the Bohai Sea, which have a large hydrocarbon generation potential.Due to differences in the formation and development of these depressions, the thermal evolution and hydrocarbon generation and expulsion characteristics of the source rocks in different depressions and intervals are quite different.By studying the burial history, thermal history, and hydrocarbon generation and expulsion history of multiple sets of source rocks in three oil-rich depressions in eastern Bohai Sea, this paper determines the source rock generation, hydrocarbon expulsion timing and evolution characteristics of the Bozhong Depression, Bodong Depression and Miaoxi Depression.The results indicate that: ① The thermal evolution of source rocks in individual tectonic units in the eastern Bohai Sea has a general end of "high in the west and low in the east".The earliest hydrocarbon generation time in the Bozhong Depression is 34.4 Ma, while that for the Bodong and Miaoxi depressions are 30.8 Ma and 14.2 Ma, respectively.The earliest hydrocarbon expulsion time of the Bozhong Depression is 27.8 Ma, while that for the Bodong and Miaoxi depressions are 20.9 Ma and 6.7 Ma, respectively; ② The source rock in the Bozhong Depression has a relatively high degree of thermal evolution, and now it mainly provides natural gas to the reservoirs, which provides a gas source for the formation of natural gas reservoirs and condensate gas reservoirs in the Bozhong area.The degree of thermal evolution in the Bodong Depression and Miaoxi Depression gradually decreases, which provides a large amount of oil source for the reservoirs.The marginal areas of the basin are mainly oil reservoirs.

Keywords

• oil-rich depression
• source rock
• hydrocarbon and expulsion characteristics
• basin modeling
• eastern part of the bohai sea