EOR: Past, Present and What the Next 25 Years May Bring

Abstract

Abstract The paper presents an analysis of worldwide EOR activities and trends for the mid-term future. The focus of the paper is on EOR production levels and the corresponding number of projects within each major EOR technology group: thermal, gas flooding, chemical and other methods. Most EOR activities are in North America where the conventional oil production decline is now well established and EOR is one of a few remaining options for additional oil production. In the United States, the unfavorable economic climate of the late 1980's caused the number of new EOR projects to decline rapidly, followed by the corresponding leveling of oil production and even a modest EOR production decline in 2002. Thermal recovery continues to provide the largest, although it is declining fraction of EOR production. In the long-term, thermal recovery methods may play an increasingly important role in the recovery of the huge heavy oil and tar sands resources. Gas flooding continues to gain momentum and shows promise for further gains. Chemical flooding projects suffered from declining interest and negligible production rate. Fluid diversion via permeability modification control offers considerable near-term potential. It is likely that EOR-produced oil in the United States has already reached its peak level and that it will increase above the current production rates only at substantially higher and stable oil prices. World's EOR production peak is likely to occur 30–35 years after the onset of global oil production decline, or in mid 2060's. Definitions There is much confusion around the usage of the term EOR and especially the term IOR. Ref. 1 describes the effort to reach agreement on the definitions to clarify communications by forming an industrial committee under the auspices of the SPE. This paper adheres to that proposed definition, Fig.1. Enhanced oil recovery (EOR) refers to reservoir processes that recover oil not produced by secondary processes. Primary recovery uses the natural energy of the reservoir to produce oil or gas. Secondary recovery uses injectants to re-pressurize the reservoir and to displace oil to producers. Enhanced oil recovery processes target what's left. They focus on the rock/oil/injectant system and on the interplay of capillary and viscous forces. EOR in Perspective Just how did EOR evolve and what has been its share of oil production? In this regard it is helpful to note the current distribution of oil production by primary, secondary and tertiary (EOR), in the United States, which has remained without change for at least 15 years, Fig.2. Only 37 percent of oil produced in the United States comes from primary methods. Secondary methods of waterflooding and gas pressure maintenance contribute the lion's share of 51 percent. About 12 percent is produced by tertiary methods, also known as EOR. Worldwide oil production by EOR is now 2.9 million barrels per day, or 3.7 percent of world's total oil production, Fig. 3.