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Abstract

A considerable portion of current world oil production comes from mature fields and the rate of replacement of the produced reserves by new discoveries has been declining steadily over the last few decades. To meet the growing need for economical energy throughout the world, the recoverable oil resources in known reservoirs that can be produced economically by applying advanced IOR and EOR technologies will play a key role in meeting the energy demand in years to come.

This paper presents a comprehensive review of EOR projects. Specifically, the paper presents an overview of EOR field projects by reservoir lithology (sandstone, carbonate, and turbidite formations) and offshore versus onshore fields. More than 1,500 field projects are reviewed and summarized to evaluate feasibility of EOR technologies. Another area of growing interest is the combination of near-well-bore and in-depth conformance technologies with chemical EOR technologies such as SP and ASP. However, these are in early stages of evaluation. Examples of numerical simulations combining chemical conformance and EOR technologies are presented showing the potential of this recovery strategy in waterflooded reservoirs. Impacts of carbon capture cost and volatility of oil and carbon-credit markets on CO2-EOR projects based on anthropogenic sources is also addressed.

Based on this review, it is evident that thermal and chemical EOR projects dominate in sandstone formations while gas and water-based recovery methods dominate carbonate, turbidite, and offshore fields. The review also shows the growing trend of CO2 (from natural sources), high-pressure air injection (HPAI), and chemical flooding including in-depth conformance field projects in the U.S. and abroad.

CO2-EOR / sequestration in offshore fields and chemical EOR processes offshore (e.g., polymer-based methods) and onshore, including heavy crude oil reservoirs, are some of the opportunities identified for the next decade based on preliminary evaluations and proposed or ongoing pilot projects. The critical review will help to identify the next challenges and opportunities in EOR. Hybrid schemes combining IOR/EOR as well as CO2-EOR/sequestration can be ranked on the basis of adequate simulation procedures.

Introduction

EOR activity has experienced an increasing interest in recent years in spite of crude oil price decline since 2008. CO2-EOR in the Permian Basin and thermal methods, especially in Canada, continue to be the most dominant EOR field applications documented in the literature. However, chemical EOR methods have shown an increase in pilot tests and a few large field implementations including the combination of chemical EOR methods with conformance technologies.

In the U.S., chemical and thermal EOR projects have been in constant decline from the mid 1980s to 2005 (Figure 1). However, EOR gas injection projects have shown a steady trend since the mid 1980s and a growing trend since year 2000, especially with the increase of CO2 projects. Indeed, since 2002 EOR gas injection projects outnumber thermal projects for the first time in the last three decades. However, thermal projects have shown a slight increase since 2004 due to the increase of High Pressure Air Injection (HPAI) projects in light oil reservoirs. Chemical EOR methods still have not captured a nigh level of interest from operating oil companies with only two projects reported in 2008 (Aalund, 1988; Bleakley, 1974, Leonard, 1982, 1984 and 1986; Matheny, 1980, Moritis, 1990, 1992, 1994, 1996, 1998, 2000, 2002, 2004, 2006 and 2008; Noran, 1976 and 1978). However, there is an increase in EOR chemical projects in the U.S. and abroad that have not been documented in the literature for different reasons that will be summarized later in the paper.