Abstract

During the last decades colloidal dispersion gels (CDG) have been applied as an EOR method, providing sweep improvement in reservoirs with unfavourable mobility ratio. Our core flood results also indicate an improved microscopic sweep or microscopic diversion by CDG. This paper investigates the oil mobilization properties of nano-sized silica particles in comparison to nano-sized CDG particles and discusses the underlying mechanisms of microscopic flow diversion.

Improved microscopic displacement efficiency has traditionally been coupled to changes in capillary number. However, this approach is insufficient to describe processes like low salinity injection, colloid dispersion gels, and microbial enhanced oil recovery.

This paper presents a new concept of EOR by improved microscopic displacement defined as microscopic diversion. This method involves pore blocking and diversion of injection fluids. Multi-phase flow experiments using nano-sized silica particles attempts to investigate the effect (inelastic) nano-sized fines migration can have on oil mobilization by microscopic diversion.

The oil mobilization properties were investigated by core floods using well-defined nano-sized silica particles in comparison with injection of CDG, polymer or silica particles dispersed in a polymer solution. Core floods were performed on water-wet Berea sandstone cores with permeabilities of approx. 500 mD. The comparison of inelastic silica particles, polymer solutions and nano-sized CDG particles allowed an evaluation of the importance of viscoelastic properties for microscopic diversion.

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