State of the art of enhanced oil recovery

Enhanced oil recovery (EOR) tecniques, either chemical, miscible or thermal, aim at improving recovery efficiency over and above that achievable with conventional methods by increasing sweep efficiency and/or reducing residual oil saturation. Although each EOR method has its own range of application, these methods are to a large extent complementary and thus together cover a wide range of reservoir conditions. In spite of the considerable effort spent on research and field testing during the last 30 yr, enhanced oil recovery techniques are, on the whole, still very much in a stage of development. Most successful so far have been thermal recovery methods, particularly those employing steam. It is important to realize that EOR methods always have to be tailored very carefully to the specific conditions of the reservoir where they are to be applied. This also means that extensive field testing is a prerequisite for large-scale application.