Overview: EOR/IOR (January 2007)

Abstract

Reserves are a key factor for any oil company. This year's EOR issue highlights field projects that increased reserves by use of enhanced oil recovery. Economic incremental-oil production from field projects that used three different technologies [CO2 huff ‘n’ puff, mobility-control polymer, and steam-assisted gravity-drainage (SAGD)] is discussed. Daqing Oilfield Co. Ltd., People's Republic of China, has several papers discussing its commercial polymer flood. An SPE Advanced Technology Workshop on chemical flooding in Daqing concluded with Daqing stating that 25% of its production results from polymer injection—250,000 B/D. One paper stated, "Unquestionably, the application is successful, and the accumulated output has exceeded 70 million tonnes" (more than 500 million bbl of oil). Of interest is a closely spaced pilot to expand the polymer flood to marginal reservoirs. The strategy was injection of different-molecular-weight polymers in a staged manner, from low to high molecular weight, into zones with permeabilities appropriate for the injected polymer. Reported oil rates increased 1.8 times in confined production wells. Ultimate oil recovery beyond waterflood was 11.7%, of which 5.2% resulted from polymer flooding. Sixteen CO2 huff ‘n’ puff projects were conducted on different wells in the Forest Reserve oil field in Trinidad and Tobago over the last 20 years. CO2 from an ammonia plant was injected into either inactive or poor oil producers. Average slug size was 1 MMscf of CO2 per foot of sand, with a 3- to 5-day soak period. Multiple huff ‘n’ puff cycles were effective in more than half the wells, with the second to fourth cycle being the most productive for the majority of wells. Oil-rate improvements from nothing to up to 60 times pre-CO2-injection values were observed. During the startup and early operation of horizontal SAGD wells, it is important to understand the flow distribution of bitumen and water along the horizontal reservoir interval. If this distribution is understood, the distribution of steam, injected either at the heel or toe of the steam injector, can be adjusted to optimize the startup and early operation of the SAGD pair. Total E&P Canada permanently installed optical fiber along its first Joslyn SAGD production well to monitor the temperature profile continuously during startup and production. Thus, good engineering, technology, and a willingness to try different approaches can increase reserves in very large as well as smaller applications. EOR/IOR additional reading available at the SPE eLibrary: www.spe.org SPE 101202 "Study of High-Concentration Polymer Flooding To Further Enhance Oil Recovery" by Yang Fulin, Daqing Oilfield Co. Ltd., et al. SPE 100117 "Application of Smart-Well Technology to the SACROC CO2 EOR Project: A Case Study" by J. Brnak, Kinder Morgan Production Co. LP, et al. SPE 100346 "Suplacu de Barcau Field—A Case History of a Successful In-Situ Combustion Exploitation" by A. Panait-Patica, Petrom S.A., et al.