Abstract

Polymer flooding is the most commonly tested chemical EOR strategy worldwide. The method aims at improving the macroscopic sweep efficiency by reducing the mobility ratio, the viscous fingering and the permeability in high-perm streaks. Although a number of on-shore field trials have been performed, polymer flooding is still rarely used for offshore fields. The logistics and facility requirements make the operational design and execution more challenging in an offshore environment. The decision of conducting an offshore polymer EOR field trial must be supported by a strong technical evaluation (laboratory and simulation studies) and thorough operational field trial design that aims at targeting the different challenges to reduce risk and uncertainty and increase the likelihood of success. We present the logistical, technical and operational aspects of the design of an offshore polymer flood.

In this paper we present a procedure to minimize risk and reduce uncertainty by initial laboratory tests and continuous monitoring of key parameters when conducting the field trial. We address the logistical considerations and facility requirements related to polymer solution storage, polymer integrity, chemical additives, mixing, handling and real-time quality control. All necessary and critical parameters to be monitored are described herein. We describe the possible drag reduction induced by the polymer in the tubing, the near-wellbore shear effect on the injectivity and the pressure gauge setup essential to make a quantitative trial evaluation. We also discuss the potential impact of the polymer on the produced oil-water mixture and a way to mitigate polymer-induced emulsification via demulsifiers. Various operational conditional ‘what-if' scenarios are considered to provide a tailor made solution for each of them. Finally, we show how inter-well tracer tests can be used to evaluate polymer EOR trials wrt. macroscopic sweep improvement.

Currently, very few papers describe both operational and technical aspects, and very few papers suggest practical procedures for offshore polymer floods. With the increased focus on offshore EOR implementation due to production decline and reservoir maturation, this paper aims at providing a practical guideline and a best practice operational workflow for the design, execution and evaluation of offshore polymer EOR field tests.

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