A Low-Density Direct Emulsion (DE) System has been Successfully Formulated for Mature Depleted Fields

Abstract

A low-density direct emulsion (DE) system has been successfully formulated to minimize formation damage in mature depleted fields. Key objectives for the DE system are to provide all the functions of traditional reservoir drill in fluids (RDF) in terms of efficient cutting suspension and carrying characteristics, effective fluid loss control and friction coefficient, while minimizing overbalance on depleted formations. Excessive overbalance on the formation would potentially cause severe losses and could result in formation damage, with negative impacts on the environment, and an increase in overall fluid cost. This novel oil-in-water DE system consists of a dispersion with oil as the internal phase, and water as the external phase. It targets densities less than 8.17 lb/gal to minimize overbalance on the formation while providing all the benefits of an emulsion system – enhanced friction reduction, effective fluid-loss control, superior rheology for hole cleaning and minimal ECD, and effective clay inhibition. Numerous attempts of using DE systems in oil field drilling fluids have been made in the past. However, DE systems have never been fully accepted in industry due to difficulties maintaining the emulsion stability and its sensitivity to common contaminants. A novel thermodynamically stable DE system has been successfully formulated and used to drill a well with no excessive losses or emulsion stability issues. The paper will present a detailed study of the laboratory development of the DE system along with field application data and lessons learned.