Abstract Time-lapse seismic monitoring is a key component in the geological sequestration of greenhouse gases. Currently, a lack of understanding of the influence of injected CO 2 on rocks’ geophysical signatures is reported. Using a novel ultrasonic experimental system, we measured the variations in the longitudinal (P) and transverse (S) elastic wave speeds of a CO 2 -saturated porous medium at different pressure and temperature conditions around the CO 2 critical point. The results show that both P- and S-wave speeds, corrected to seismic frequencies, decreased by more than 4.5% across the CO 2 gas to liquid and gas to supercritical states, primarily as a consequence of CO 2 density increase. This study provides a-20 firm basis for the use of seismological methods in monitoring sequestered CO 2 ; although the abruptness, and hence remote seismic detectability, depends on which phase boundary is crossed. Further, these measurements also allow us to compare observations to frequency-dependent wave propagation theory. The observed wave speeds mostly align with those calculated at 1 MHz using the Biot theory for both CO 2 and H 2 O saturated states. However, the observed and calculated wave speeds diverge above the phase transition in some of the tests, possibly due to the kinetics of the phase transition within a porous medium. As such, aside from the direct utility in providing information on the expected seismic responses, the CO 2 provides a highly tunable fluid that can be advantageous for experimental studies.

Abstract Geothermal energy has the potential to reduce both the production costs and greenhouse gas emissions associated with oil sands production in the Western Canada sedimentary basin (WCSB) in Northern Alberta. This is currently being investigated through the Helmholtz-Alberta Initiative, which is a research collaboration between the Helmholtz Association of German Research Centres and the University of Alberta. The primary area of interest is in the Athabasca oil sands where the WCSB is relatively thin and the Phanerozoic sedimentary succession is thinning toward the northeast and subcropping onto the Canadian shield. Beneath the Athabasca oil sands, the Precambrian basement is at a depth of 0.5 km (0.31 mi) and can be studied by the analysis of the geophysical logs and core and rock chip samples from a deep 2.4 km (1.49 mi) well drilled into the granitic basement rocks. A second study area is located around Peace River, where the WCSB is about 2 km (1.24 mi) thick, and data from the Phanerozoic section are being analyzed. The research is focused on an evaluation of potential heat sources for oilsands processing in areas with existing leases. Revised maps of the temperature at the top of the Precambrian basement confirms that temperatures greater than 60 degrees C could be found within the sedimentary strata in the Peace River oil sands area. This temperature will be found in the crystalline Precambrian basement beneath the Athabasca oil sands. Extraction of heat will require the development of engineered geothermal systems with artificial porosity created and fluids circulated at depth. The economics of this process appear favorable, and additional research will define the feasibility of this type of heat production in more detail.

Abstract The architectural complexity of a paleovalley ~350 m deep has been revealed by acquisition and conventional processing of a high-resolution seismic-reflection survey in northern Alberta, Canada. However, processing degraded much of the high quality of the original raw data, particularly with respect to near-surface features such as commercial methane deposits, and that motivated use of additional processing algorithms to improve the quality of the final images. The additional processing includes development of a velocity model, via tomographic inversion, as the input for prestack depth migration (PSDM); application of a variety of noise-suppression techniques; and time-variant band-pass filtering. The resulting PSDM image is of poorer quality than the newly processed time-reflection profile, thus emphasizing the importance of a good velocity function for migration. However, the tomographic velocity model highlights the ability to distinguish the materials that constitute the paleovalley from the other surrounding rock bodies. Likewise, the reprocessed seismic-reflection data offer enhanced spatial and vertical resolution of the reflection data, and they image shallow features that are newly apparent and that suggest the presence of gas. This gas is not apparent in the conventionally processed section. Consequently, this underscores the importance of (1) ensuring that primarily high-frequency signals are kept during the processing of near-surface reflection data and (2) experimenting with different noise-suppression and elimination procedures throughout the processing flow.

The front matter contains the title page, copyright page, table of contents, about the editors, preface, and acknowledgments.

Heavy Oil as an Important Resource for the Future With more than 87 million barrels of oil being consumed worldwide every day, oil has come to be the life-blood of modern civilization. It is cheap, relatively easy to procure and use, and has become addictive in terms of its flexibility in enhancing our lives in multiple applications. First and foremost, we are dependent on oil for transportation because more than 90% of transportation energy comes from oil. In addition, oil provides a feedstock for pharmaceuticals, agriculture, plastics, clothing, mining, electricity, and several other products that we use in our everyday lives. Almost all goods are connected to oil in one way or another; we are all dependent on oil and gas more than any other resource, yet not many of us think about this dependence. Oil exploration and production has fueled world economic growth over the last century, and it has reached a stage where the economy of several nations is dependent on the exports of oil to the international market. Global demand for oil is now outstripping supply growth and the importance of this crucial commodity is such that companies engaged in oil exploration and production or transportation have dwarfed those in every other commodities sector. Some important aspects to keep in mind are that oil and gas are absolutely critical to the operation of today's industrial society, essential for sustained economic growth in the industrialized world, and key to progress in nations working their way toward prosperity. This translates into a growing demand for oil and gas, much of it coming from developing nations with low levels of energy use per capita.

Introduction With a high demand of hydrocarbon worldwide, conventional oil production is quickly approaching its peak. Inevitably, heavy oil and bitumen (ultraheavy oil) will emerge as “new” (so-called unconventional) hydrocarbon resources because of their tremendous potential. Currently, more than 50% of Canada’s oil production is from heavy oils (Alboudwarej et al., 2006; Hinkle and Batzle, 2006). Such heavy oils are highly viscous, difficult to move in reservoirs, and much more expensive to produce. In addition to mining and other cold production methods, many different techniques (e.g., thermal, chemical, or in situ combustion, etc.) have been applied to mainly reduce viscosity and assist the heavy-oil production. None of these techniques have matured completely yet, and engineering developments are occurring rapidly. These techniques remain expensive in terms of energy and resources used (lots of water) and in terms of efficiency and overall environmental impact. The steam-assisted gravity drainage (SAGD) technique is a current popular technique. In a steam chamber, more than 60% of oil in place can be produced (Caruso, 2005; Gupta, 2005). However, on a reservoir scale, efficiency can be low (approximately 15% with different resources). Clearly, seismic techniques hold great potential for assisting reservoir characterization and recovery monitoring. Monitoring has been demonstrated successfully in several fields [Cold Lake (Eastwood et al., 1994) and Duri Field, Indonesia (Jenkins et al., 1997)]. However, to be effective, we must understand the seismic properties of the heavy oils and the heavy-oil sands. This understanding of in situ properties is the key to bridging the seismic response to reservoir properties and changes. Schmitt (2004) provided a general review of rock physics as related to heavy-oil reservoirs. Here, we examine the seismic properties of heavy oils in detail.

Introduction Rocks filled with heavy oil do not comply with established theories for porous media. Heavy oils demonstrate a blend of purely viscous and purely elastic properties, also referred to as viscoelasticity. They have a nonnegligible shear modulus that allows them to support shear-wave propagation depending on frequency and temperature. These oils behave as solids at high frequencies and low temperatures and as fluids at low frequencies and high temperatures. The solid-like properties of heavy oils violate Gassmann’s equation, the most common and widely used fluid-substitution technique in the industry. Few instances of elastic property modeling for heavy-oil-saturated rocks have been reported. Most previously reported work has involved modeling without comparison with measured data, or modeled results on simple grain-fluid aggregates with comparison to measured ultrasonic data. We have modeled the viscoelastic properties of heavy-oil-saturated rock samples using the Hashin—Shtrikman (HS) bounds and the frequency-dependent complex shear modulus of the heavy oil. The two studied rock samples are very different in terms of lithology and consolidation state. In our exercise, we have extended the HS bounds to incorporate complexities such as intragranular porosity and the contribution of heavy oil to rock matrix properties. By considering the complex shear modulus of the heavy oil in our HS calculations, we have been able to estimate attenuation. We also tested the applicability of Ciz and Shapiro’s (2007) form of the generalized Gassmann’s equations in predicting the saturated bulk and shear moduli of the heavy-oil-saturated rock samples.

Introduction Heavy oil has recently become an important resource as conventional oil reservoirs have limited production and oil prices rise. More than 6 trillion barrels of oil in place have been attributed to the world's heaviest hydrocarbons (Curtis et al., 2002). Therefore, heavy-oil reserves account for more than 3 times the amount of combined world reserves of conventional oil and gas. Of particular interest are the large heavy-oil deposits of Canada and Venezuela, which together may account for approximately 55%–65% of the known less than 20° American Petroleum Institute (API) gravity oil deposits in the world (Curtis et al., 2002). Heavy oils cover a large range of API gravities, from 22° for the lightest heavy oils to less than 10° for extra-heavy oils. This wide range of values means that heavy oils vary greatly in their physical properties. Thus, extensive research is required before the properties of heavy oil can be properly understood. Several prevailing issues are seen repeatedly in various fields around the world, including how to make measurements on unconsolidated sandstone cores, production of sand with oil and its effect on formation, exsolution gas drive of heavy oil, understanding the control of viscosity and other physical properties of heavy oils, and monitoring of steam recovery processes. Simply, the high viscosity of heavy oils limits its extraction by traditional methods

Introduction 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.

Introduction This case study explores rock physical properties of heavy-oil reservoirs subject to the steam-assisted gravity drainage (SAGD) thermal-enhanced recovery process (Butler and Stephens, 1981; Butler, 1998). Previously published measurements (e.g., Wang et al., 1990; Eastwood, 1993) of the temperature-dependent properties of heavy-oil saturated sands are extended by fluid substitutional modeling and wireline data to assess the effects of pore fluid composition, pressure, and temperature changes on the seismic velocities of unconsolidated sands. Rock physics modeling is applied to a typical shallow McMurray formation reservoir (135–160 m depth) encountered within the bituminous Athabasca Oil Sands deposit in Western Canada to construct a rock-physics-based velocity model of the SAGD process. Although the injected steam pressure and temperature control the fluid bulk moduli within the pore space, the effective stress-dependent elastic frame moduli are the most poorly known yet most important factors governing the changes of seismic properties during this recovery operation. The results of the fluid substitution are used to construct a 2D synthetic seismic section to establish seismic attributes for analysis and interpretation of the physical SAGD process. The findings of this modeling promote a more complete description of 11 high-resolution, time-lapse, 2D seismic profiles collected over some of the earliest steam zones.