Chapter 5: Measuring and Monitoring Heavy-oil Reservoir Properties
Kevin Wolf, Tiziana Vanorio, Gary Mavko, 2010. "Measuring and Monitoring Heavy-oil Reservoir Properties", Heavy Oils: Reservoir Characterization and Production Monitoring, Satinder Chopra, Laurence R. Lines, Douglas R. Schmitt, Michael L. Batzle
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The level of interest in heavy-oil and bitumen reservoirs has dramatically increased in recent times. Increased production of these reservoir types has stimulated research on the properties of these reservoirs under various conditions to aid in the initial characterization of the reservoir and monitor production strategies in situ utilizing seismic data. Rock physics provides the crucial link between the physical properties of the reservoir and seismic properties that can be remotely measured; however, to this point there is not a robust model that can be used to predict or infer the properties of heavy-oil or bitumen sands from seismic data, nor is there sufficient experimental data to calibrate such models. We present a methodology to characterize and monitor heavy-oil reservoirs by inverting converted-wave seismic data to obtain P-to-S converted-wave elastic impedance (PSEI) estimates as a function of angle. By examining these data in “PSEI space” (crossplots of PSEI values obtained at different angles), we can infer the conditions in the reservoir and possibly relate them to physical properties of the reservoir through a reliable rock physics model. This methodology points out the need for better defined rock physics models that need to be calibrated to a large, robust data set. Experimental measurement of heavy-oil sands is challenging, and to meet these challenges, we have designed an ultrasonic pulse transmission system that has been optimized for use with heavy-oil sand samples. These samples provide several unique challenges in the laboratory that are not typically encountered when measuring traditional hard rocks such as carbonates or sandstones. Although the system has several specialized components, we will focus on the design of the transducers used in the system. The transducers are uniquely designed so that they closely match the impedance of the bitumen sand over a wide temperature range, resulting in sharp first arrivals while maximizing the received amplitude.
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Heavy oil is an important global resource with reserves comparable to those of conventional oil. As conventional resources get thinner, attention is being focused on heavy oil and bitumen, which hold the promise of becoming useful fuels. Already more than 1 million barrels of oil are being produced from the oil sands in Canada; heavy oil represents half of California’s crude oil production in the United States and is a major production in Mexico. With demand for global energy soaring, heavy oil will undoubtedly be an important resource to be exploited in a big way in the near future.
The SEG Development and Production Committee held its Heavy Oil Forum in Edmonton, Alberta, in July 2007. This was a joint research forum cosponsored by the Canadian Society of Exploration Geophysicists (CSEG) and SEG and hosted by the University of Alberta. Preceding the forum, a field trip took the participants to the vast Athabasca Oil Sands region where they observed the outcrops, open pit mining, and steam injection operations, followed by a tour of the steam-assisted gravity drainage projects. Topics of the well-attended forum included the definition of heavy oil; where is heavy oil found; how it is produced; heavy-oil reservoir characterization; fluid and rock properties; electrical, tilt, and gravity techniques; borehole, surface seismic measurements; and microseismicity.