Research paperEffects of carrier bed heterogeneity on hydrocarbon migration

- Concretions along bedding planes cause stratigraphic heterogeneity in reservoir.
- Such heterogeneity results in peculiar oil migration pathways and accumulations.
- Simulation shows the effects in Donghe Sandstone reservoir, Tarim Basin.

Reservoir/carrier bed heterogeneity is a common geological phenomenon. This study applied a hydrocarbon migration model based on the invasion percolation theory to simulate the formation of hydrocarbon migration pathways in heterogeneous carrier beds. The results indicate that the pathways and hydrocarbon accumulations in reservoirs may differ from conventional models when continuous low-permeability layers occur as networks within reservoirs. Such low-permeability layers may have formed through depositional or diagenetic processes within reservoir rocks at variable scales. Oil-bearing reservoir in Donghe Sandstone in Hadexun Oilfield in northern Tarim Basin, China, was analyzed to demonstrate the forming mechanisms of substantial tilting of oil-water contact. Donghe Sandstone is a quartz sandstone deposited in an open marine shoreface-shelf environment during a major transgression in Early Carboniferous. . Major diagenetic products are abundant tabular concretions along bedding planes and cross laminae. The low-permeability concretions serve as fluid flow barriers which compartmentalize the Donghe Sandstone reservoir. As a result, the oil-water contacts and the saturation of oil in the reservoir appear irregular and tilted in Hadexun Oilfield and neighboring regions.