Abstract: Simulation of Hydrocarbon Maturation and Migration of Eocene Source Rocks in Jiyang Lacustrine Basin, PRC

Shenbiao Yang

Jiyang lacustrine basin is located in the northeastern China, and is the onshore part of the Bohai Bay sedimentary province. A large volume of hydrocarbons has been discovered within the basin during the past three decades.

The major source rock in the basin is the lacustrine shale in the lower part of the Shahejie Fm (Eocene). Three-dimensional simulation of hydrocarbon maturation and migration, using specially designed simulator, reveals three distinct stages of thermal maturation: the immature, mature, and high mature stages. The immature stage is characterized by low hydrocarbon concentration in the source rock (<200 ppm), low vitrinite reflectance (<0.3), and low saturated/aromatic hydrocarbon ratio. The burial depth of the source rock is generally less than 2200 meter with temperature being less than 93°C. The source rock in a mature stage has higher hydrocarbon concentration. The temperature for this stage ranges from 93°C to 122°C, corresponding to burial depths of 2200-3000 eters. The high mature stage is characterized by higher hydrocarbon concentration, and high vitrinite reflectance (0.9-1.0). The burial depths range from 3000 to 3800 meters with temperatures of 122°C to 150°C.

The simulation demonstrates that, during five stages of sedimentary compaction, primary hydrocarbon migration occurs in the hydraulic fracture zone during the 3rd stage and is mainly caused by fluid displacement. Based on the simulation, a total of 46.5 billion tons of hydrocarbon was generated and 9 billion tons migrated out of the source rocks. The volume of gas generated is about 5 × 10¹³ cubic meters, which gives a gas reserve of 555 billion cubic meters.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994