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Heterogeneous Characteristics of Hydrocarbon Previous HitMigrationNext Hit: Observations, Controlling Factors, and Consequences

Xiaorong Luo1, Likuan Zhang1, Qianjin Liao2, Dunqing Xiao2, Junqing Su2, Shuqin Yuan2, and Changhua Yu2
1Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing, China
2Research Center of Exploration and Development, Dagang Oilfield Company, CNPC, Tianjin, China

Carriers are important linkages for hydrocarbon Previous HitmigrationNext Hit and accumulation in a petroleum system. Oil and gas migrate commonly along narrow and zigzag pathways in porous media, even in those “homogeneous” media at a macro-scale. A Previous HitmigrationNext Hit simulator based on percolation theory, which couples the fluid potential as driving force with capillary pressure as resistance, may satisfactorily explain Previous HitmigrationNext Hit processes in heterogeneous media. In macro-scale homogeneous carriers, Previous HitmigrationNext Hit pathways are generally perpendicular to equal-potential lines, but locally the pathways are irregular because of the influence of micro-heterogeneity. The irregularity of these pathways depends on the difference between competing driving force and capillary pressure. When numerous pathways formed in a Previous HitmigrationNext Hit-accumulation system, the flux of migrating hydrocarbons varies among these pathways. In macro-scale heterogeneous carriers, the irregularity of Previous HitmigrationNext Hit pathways are exacerbated. Hydrocarbons tend to migrate in carriers where the hydraulic conductivity is relatively large. For example, when two carriers of different conductive capacities abut against an open fault, hydrocarbons fill the fault opening first, then find the carrier with the least resistance to migrate. These pathways differ from those predicted by fluid potential.

Faults and fluvial sand-bodies combine to form extremely heterogeneous carriers in the Oligocene petroleum system in Chengbei Step-Fault Zone, Bohaiwan Basin, China. The Previous HitmigrationNext Hit behavior in this system was studied by classifying the carrier-fault Previous HitpathwayNext Hit combinations into 14 types. The simulation results show that the discovered oil accumulations are clearly associated with dominant pathways.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas