Abstract

Design of micellar floods is largely based on laboratory experiments, which are usually un-scaled. This paper describes scaling criteria for the process, derived from the basic flow equations, using Dimensional Analysis and Inspectional Analysis. The derivations are based on three phase (oleic, emulsion. and aqueous), six-component (oil, water, surfactant, polymer, monovalent ion, and divalent ion) flow in a porous medium. The general scaling criteria were simplified for core floods, and verified by micellar floods in scaled models. Model and prototype were geometrically scaled Berea cores. Prototype performance was predicted using the model results and compared with the actual prototype results. Good agreement was obtained in most cases between the actual and predicted oil production histories, showing the validity of the scale-up.

The scaling criteria derived can be used for designing a micellar flood. Implications of partial scaling are discussed for field applications.

Introduction

Micellar flooding process is one of the proven chemical recovery methods for the tertiary recovery of light oils. The process consists in injecting a micellar solution slug (5–10% rock pore volume) and a polymer buffer (40–50% pore volume), followed by continuous injection of water (drive water). Micellar solutions are surfactant stabilized oil-water micro emulsions. Often, they also contain co-surfactants, such as alcohols, for viscosity control, and salts to improve solution properties. Micellar solutions are effective in increasing the Capillary Number, which is crucial for the mobilization and recovery of tertiary oil. Polymer buffer, usually a dilute polymer solution (about 500 ppm), provides mobility control behind the displacement front so that most of the residual oil is mobilized and banked before the drive water dissipates the micellar slug.

The process has been evaluated in thirty field tests1 and was found to be technically successful, having a process efficiency (oil recovered-to-slug volume ratio) of 3–4. Recently, Thomas et al.2 showed that process efficiency can be improved to 12–15 through the use of multiple slugs and graded slugs instead of a single micellar slug. Economics of the process remain unattractive, mainly due to the cost of chemicals and the initial expense in the development of the process for a particular field, as well as low oil prices (< $20/bbl). Chemicals that is better adapted to reservoir conditions, and laboratory studies representative of field conditions will improve the economic feasibility of the process. Laboratory results based on scaled model experiments will reduce the risk in extending them to field. Scaling criteria derived for the process were discussed in a previous paper2.

MATHEMATICAL MODEL

The micellar flooding process can be described mathematically for simplified situations, e.g. considering the oil (o) to be one component, surfactant (s) another, and water (w), polymer (p), monovalent ions (m), and divalent ions (d) similarly single components. The concentration of a particular component in a given phase is expressed as a mass fraction Cphase, component. Diffusion and dispersion is assumed to occur in the case of surfactant (s), polymer (p), monovalentions (m), and divalent ions (d). It is assumed that the coordinate axes are oriented in the direction of flow.

This content is only available via PDF.
You can access this article if you purchase or spend a download.