Transport Relationships in Porous Media as a Model for Oil Reservoir Rocks

Abstract

There is growing fear that world oil reserves are depleting fast due to the current energy demand, and future energy needs. Recently, there has been a call for radical shifts in investment towards cleaner and more efficient energy technologies. However, most of these renewable energy alternatives are still at infant stages of research. Thus, the more conventional hydrocarbon oil is still the most logical option. Oil recovery efficiency is heavily influenced by the structure of void space that oil occupies within the reservoir rocks. In general, less than 50 % of oil is recoverable from the source rock, and thus the understanding of oil entrapment (bound volume index) is essential in prediction of economical potential of an oil reservoir. The bound volume index is the non-movable fluid volume in oil reservoirs. Reservoir rocks are chemically and geometrically heterogeneous. In this study, model catalyst support pellets with similar chemical and geometrical properties to oil reservoir rocks, but with more homogeneous chemistry were investigated. In this thesis, novel multi-technique approaches have been used to understand the transport relationships in porous media. The mechanisms of entrapment and distribution of the irreducible non-wetting phase within porous media was investigated with mercury porosimetry. Mercury entrapment is strongly dependent on the structural (voidage fraction, pore size, and pore size distribution) as well as on topological (connectivity and tortuosity) properties of porous media. The pore size distribution (PSD), a measure of pore length, and pore connectivity were determined by gas sorption. PGSE NMR was used to study the heterogeneity and tortuosity of the samples. In addition, PSGE NMR was used to study the kinetics of adsorption in porous media, and thus elucidate the relationships of liquid connectivity, and molecular exchange between liquid and vapour phases. In general, mercury entrapment occurred at larger mesopore radii, and was present at all experimental time-scales. In addition, mercury entrapment was found to increase with increased variance in the PSD. PGSE NMR kinetic studies revealed that tortuosity decreased with an increased liquid connectivity and there was enough evidence to suggest molecular exchange between the liquid and vapour phases. Furthermore, the tortuosity of fully saturated samples increased with an increased mercury entrapment.

Date of Award	1 Apr 2011
Original language	English
Awarding Institution	University of Bath
Supervisor	Sean Rigby (Supervisor)