Nanosized Particles for Enhanced Oil Recovery

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 129933, ’Nanosized Particles for EOR,’ by Tormod Skauge, SPE, Sverre Hetland, Kristine Spildo, SPE, and Arne Skauge, SPE, Uni CIPR, prepared for the 2010 SPE Improved Oil Recovery Symposium, Tulsa, 24-28 April. The paper has not been peer reviewed. Colloidal-dispersion gels (CDGs) have been used in enhanced oil recovery (EOR) to provide sweep improvement in reservoirs exhibiting an unfavorable mobility ratio. Coreflood results indicate an improved microscopic sweep or microscopic diversion by CDG. A new concept of EOR by improved microscopic displacement is defined as microscopic diversion. This method involves pore blocking and diversion of injection fluids. Introduction In most successful field applications involving CDGs, oil production increased and the water/oil mobility ratio decreased. There are few systematic studies regarding the detailed mechanisms of the CDG process. Most studies focused on the propagation of CDG in porous media and the gelation process. The gelation behavior of CDG systems was studied, with the aim of understanding the performance of CDG with respect to in-depth permeability modification. Recently, coreflood data were published that report improved microscopic displacement by use of pregenerated CDGs. The objective and properties of the conventional approach from the 1990s targeted mainly macroscopic-sweep improvement, while the more-recent approach with pregenerated colloid particles has defined two classes of CDG. Here, pregenerated colloid particles are in the range of 100 nm. These solutions also have been called linked-polymer solutions and attempt to improve the microscopic-displacement efficiency in addition to the macroscopic sweep. The purpose of this work was to investigate mechanisms for microscopic diversion by comparing the oil-mobilization properties of inelastic nanosized silica particles with those of CDG. Nanosized silica particles provide an environmentally friendly alternative to polymer or CDG flooding, thus lowering the threshold for implementation, particularly in offshore environments. Oil mobilization was investigated in a series of Berea-coreflood experiments. A porous medium is a complex structure of pore bodies and throats with a range of sizes. Any material dissolved or dispersed in water may adsorb onto the solid surface. When a polydisperse solution of particles flows through a porous medium, particles with a size larger than or equal to the throat size will be trapped. This mechanism, which leads to blocking of narrow pore throats by larger CDG particles, is known as mechanical entrapment or straining.