Chemical EOR Potential for Heavy Oil in the United States
Large volumes of heavy oil are present in the United States lower 48, mostly in California and along the Gulf coast and in lesser amounts in other basins throughout the country. Over the past decade, several estimations suggested that the U.S. heavy oil resources exceed 100 billion bbls (excluding Alaska), of which only about 10 to 15% has been produced. Due to the high viscosity of heavy oil, primary production yields poor recovery and EOR techniques are generally considered as an option to increase recovery. Thermal recovery techniques by steam injection are by far the most commonly used methods in heavy oil fields. However, thermal methods are not suited when the reservoir is thin or at depth greater than 4500 ft, due to heat loss to adjacent beds or in the well bore. On the other hand, Chemical EOR methods such as polymer flooding and ASP (Alkaline-Surfactant-Polymer) were not considered until recently as viable options for heavy oil, because of the high viscosity of the oil. However, recent field applications of polymer flood using horizontal wells have proven successful for oil as viscous as several thousands of centipoises. Based on these considerations, we investigated the potential for chemical EOR in the U.S. (excluding Alaska) by screening heavy oil fields not suited for thermal recovery and fitting a set of criteria desired for polymer flooding and ASP. These criteria include oil viscosity, permeability, thickness, depth, temperature and recovery factor. Our estimate, based on a heavy oil database published by the U.S. Department of Energy (2004) suggests that more than 200 fields representing over 6 billion bbls of heavy oil in place are potential candidates for chemical EOR in the U.S. This paper presents our screening method, the heavy oil basins in the U.S. that could be suitable for chemical EOR and summarizes relevant EOR field applications in heavy oil reservoirs.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014