Petroleum Migration and Accumulation Models Revisited from a Reservoir Engineering Perspective

Liu, Keyu¹; Tang, Xuan²; Rashid, Abdul¹; Wei, Xiaofang³
¹Earth Science and Resource Engineering, CSIRO, Beijing, WA, Australia.
²China University of Geosciences, Beijing, China.
³State Laboratory of Enhanced Oil Recovery, Research Institute of Petroleum Exploration and Development, Beijing, China.

Conventional petroleum migration and hydrocarbon accumulation has been investigated in the laboratory and field, principally by considering the interaction between the capillary and buoyancy force within carrier beds and under seals. The best oil migration pathways are generally believed to be the highly porous and permeable beds within a petroleum system. The best seals are considered to be the low permeable rocks. Oil migration and accumulation in rock formations of low porosity and permeability (e.g. tight sandstone) would require an unusually large driving force or oil column height and is thus rarely considered. Apart from the pore-throat size, oil-water interfacial tension and reservoir wettability can also play important roles in controlling the capillary force. The latter two parameters are often not considered. In reality, oil migration pathways and seals may have a range of wettabilities from strongly water-wet through mixed-wet to strongly oil-wet. The reservoir fluid compositions and properties (e.g. viscosity, density and interfacial tension) are dynamic (varying with P/T) and change within a petroleum system. We investigated the hydrocarbon migration and accumulation mechanisms using a petroleum engineering approach by evaluating various factors affecting hydrocarbon migration and accumulation using glass bead columns, rock and fluid characterization techniques under subsurface conditions and core flooding experiments. The key parameters investigated include: (1) viscosity changes; (2) wettability alteration; (3) interfacial tension variations with P/T conditions. Other petroleum engineering aspects examined include (1) relative permeability, (2) imbibitions, (3) Capillary Numbers and (5) mobility ratios. The experiments have shown that these factors can significantly affect hydrocarbon migration and accumulation. For example, oil was found preferably migrating through and/or accumulating in relatively tight regions with a favorable wettability. Therefore these petroleum engineering factors should be included in the conventional petroleum migration and accumulation models, especially when investigating the unconventional petroleum system (e.g. tight sandstone oil).

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012