The steam assisted gravity drainage (SAGD) process has been successfully tested in field pilots, and commercial applications are currently underway by a number of oil companies. The process yields higher oil rates and faster reservoir depletion, as compared to other in situ oil recovery processes. Current developments of the SAGD process are aimed at improving oil rates, improving oil-to-steam ratios "OSR," reducing energy, and minimizing water disposal requirements. In addition to SAGD, progress has been made in the development of solvent injection processes. These processes result in lower oil rates and energy, requirements as compared to SAGD. At the present time, limited field results are available for the solvent processes to allow for adequate evaluation of field performance. A novel approach for combining the benefits of steam and solvents in the recovery of heavy oil and bitumen has been undertaken at the Alberta Research Council (ARC). A newly patented Expanding Solvent-SAGD "ES-SAGD" process has been developed. The process has been successfully field-tested and resulted in improved oil rates, improved OSR, and lower energy and water requirements as compared to SAGD. The paper discusses the concept and laboratory testing of the ES-SAGD process. Introduction The most promising in situ thermal recovery technology is the SAGD process. In this process, two horizontal wells separated by a vertical distance are placed near the bottom of the formation. The top horizontal well is used to inject steam and the bottom well is used to collect the produced liquids (formation water, condensate, and oil). Following the success of the UTF project at Fort McMurray, Alberta, a number of field pilots are in progress in other heavy oil reservoirs in western Canada (Alberta and Saskatchewan), and around the world. These pilots tested the use of surface accessed horizontal wells and extended SAGD applications to problem reservoirs. These reservoirs often have lower permeabilities, are deeper, have bottom water transition zones, with initial gas-saturated "live" oil and top water/gas caps. In Alberta, the success of these pilots has led to a number of commercial SAGD projects that are currently underway. Current developments of the SAGD process at ARC are aimed at improving oil rates, improving OSR, reducing energy, and minimizing water disposal requirements. Progress has been made in the development of combined steam-solvent injection processes, a novel approach for combining the benefits of steam and solvents in the recovery of heavy oil and bitumen. A newly patented(1) Expanding Solvent-SAGD "ES-SAGD" process has been successfully field-tested, and has resulted in improved oil rates and OSR, and lower energy and water requirements as compared to conventional SAGD. The ES-SAGD concept and laboratory testing using the high pressure/high temperature experimental facilities at ARC are presented in this paper. The ES-SAGD Concept Figure 1 illustrates the ES-SAGD concept. In this concept, a hydrocarbon additive at low concentration is co-injected with steam in a gravity-dominated process, similar to the SAGD process. The hydrocarbon additive is selected in such a way that it would evaporate and condense at the same conditions as the water phase.

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The uniqueness of the steam assisted gravity drainage (SAGD) recovery process lies in the salient role of moving condensing boundaries and counter-current flows. Process effectiveness depends on the balance between rising steam and draining oil-condensate emulsions. Reservoir permeability, well completion and effective drainage-pumping of oil-condensate emulsions can affect such balance. A new, non-steady state, laboratory steam-front dynamic tracking technique was used in measuring steam-liquid counter-current and co-current flows for different permeabilities and initial gas saturations. Steam chamber ceiling propagation rates (process initialization and growth) were determined for different injection and reservoir conditions. The paper highlights critical factors that control steam-oil emulsion counter-current flow and rate of propagation of the steam chamber. In addition, the CMG STARS numerical model was used to simulate SAGD counter-current flows and determine sensitivities to different parameters. Introduction The concept of the SAGD process was developed by Butler et.al.(1) In this concept, two horizontal wells are placed near the bottom of the reservoir and separated by a distance. Figure 1a illustrates the application of the SAGD process in very viscous oil (bitumen) reservoir. The top horizontal well (an injector) is located at a distance of about 5 m above the bottom well (the producer). The process consists of two distinctive phases. An initialization phase, where in most cases, conduction heating in the space between the two wells is chosen for initialization of gravity. FIGURE 1a: Illustration of the initialization and growth phases of the SAGD process in paired horizontal wells (Available in full paper) During this phase, steam is circulated in the tubing and out of the annulus. Initial breakthrough between the wells will generally occur in a localized region. Proper initialization procedures are required to bring the entire length of a well pair into active drainage. In general, the initialization phase is slow and oil rates during this phase are low. Nasr et. al.(2) reported results on two strategies for accelerating the initialization phase of the SAGD process: first, by using inter-well channels, and second, the injection of a hydrocarbon additive (naphtha) with steam. Following the initialization phase, after the oil in the inter-well region becomes mobile enough; the second phase (the growth phase) of the process can be started. During this phase, steam is injected into the top horizontal well and production fluids are obtained from the bottom well. Pressure drop along the horizontal well bore causes a slope in the steam chamber along the well as illustrated in Figure 1a. Improvement of the process during this phase requires improving the growth rate of the steam chamber and as a result improving oil drainage rates. Figure 1b shows a cross-section perpendicular to the well bores shown in Figure 1a and illustrating fluids flow in the steam chamber. Two types of flow exist. One at the ceiling of the steam chamber (ceiling drainage) and the other along the slopes of the steam chamber (slope drainage). Along the slopes of the chamber, mobilized oil accumulates in a progressively thicker layer. However, at the ceiling, oil moves away from the front immediately after mobilization.

Canada has declining reserves of conventional oil, but vast reserves of heavy oil and bitumen. Over 90% of the world's heavy oil and bitumen trapped in sandstones and carbonates are deposited in Canada and Venezuela. Up to 80% of estimated reserves could be recovered by in-situ thermal operation. The current in-situ thermal technologies such as cyclic steam stimulation (CSS), steam flooding and steam-assisted gravity drainage (SAGD) are energy intensive and use large quantities of fresh water. Increasing pressure of environmental concerns and the threat of a carbon tax will make it imperative to find new oil extraction technologies that are less energy intensive and that use less water. Combining technologies in the form of hybrid steam-solvent processes offer the potential of higher oil rates and recoveries, but at less energy and water consumption than processes such as SAGD. At the Alberta Research Council, new hybrid steam-solvent processes have been undergoing development in recent years. The Expanding Solvent-SAGD (ES-SAGD)(1–2), is aimed at improving and extending SAGD performance by solvent addition to steam. The improvements include higher and faster drainage rates, lower energy and water requirements and reduced green house gas (GHG) emissions. The Thermal Solvent Hydrid process focuses on combining solvent with a small amount of steam in a VAPEX (vapour extraction) process (3–4). This process offers the potential of higher rates than cold solvent VAPEX at less energy consumption than SAGD. Hybrid steam-solvent processes, when fully developed, will extract oil at lower cost than SAGD and will also open currently marginal resources for exploitation, increasing oil reserves. This paper presents and discusses the principal concepts and key parameters for the new hybrid steam-solvent processes and compares expected performance to SAGD. Introduction The goal of this paper is to provide a summary of the hybrid steam-solvent processes developed at the Alberta Research Council (ARC), which include ES-SAGD and thermal solvent hybrid and provide some laboratory and field examples of these and other steam-solvent hydrid processes developed in recent years. The hybrid steam-solvent processes results at ARC illustrated the potential to develop an improved process that will significantly reduce energy, water and GHG intensity as compared to SAGD, therefore reducing operating cost while maintaining economic oil recovery rates. ES-SAGD laboratory experimental results in Athabasca illustrate 17–30% increase in oil production over that from SAGD, for the same amount of steam injected. This indicates an improvement in oil-steam ratio (OSR) by the same magnitude. More importantly, the experimental results indicate that the time required to produce the same amount of oil in ES-SAGD could be half that of SAGD. Such accelerated oil production results in significant increase in oil rates and reduction (∼50%) in steam requirements. As a consequence, natural gas burning, water requirement and GHG emissions would be reduced. This is quite significant given the large production volumes from commercial SAGD projects. The thermal solvent hybrid experimental results at ARC provided data for comparison of the process with other low energy intensity processes, like thermal solvent reflux and VAPEX(3–4). Expanding Solvent SAGD (ES-SAGD) Concept and Principles of ES-SAGD In ES-SAGD recovery process(1,2), a solvent or a solvent mixture is co-injected with steam in a hybrid process, as opposed to the injection of only steam in the SAGD process or only solvent in the VAPEX process. In the ES-SAGD process, the solvent or solvent mixture additive, whose vapourization thermodynamic behaviour is similar, or close, to that of water thermodynamic behaviour for a given reservoir condition is considered the most appropriate.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractCanada has declining reserves of conventional oil, but vast reserves of heavy oil and bitumen. Over 90% of the world's heavy oil and bitumen trapped in sandstones and carbonates are deposited in Canada and Venezuela. Up to 80% of estimated reserves could be recovered by in-situ thermal operation. The current in-situ thermal technologies such as cyclic steam stimulation (CSS), steam flooding and steamassisted gravity drainage (SAGD) are energy intensive and use large quantities of fresh water. Increasing pressure of environmental concerns and the threat of a carbon tax will make it imperative to find new oil extraction technologies that are less energy intensive and that use less water. Combining technologies in the form of hybrid steam-solvent processes offer the potential of higher oil rates and recoveries, but at less energy and water consumption than processes such as SAGD.At the Alberta Research Council, new hybrid steam-solvent processes have been undergoing development in recent years. The Expanding Solvent-SAGD (ES-SAGD) (1-2) , is aimed at improving and extending SAGD performance by solvent addition to steam. The improvements include higher and faster drainage rates, lower energy and water requirements and reduced green house gas (GHG) emissions. The Thermal Solvent Hydrid process focuses on combining solvent with a small amount of steam in a VAPEX (vapour extraction) process (3)(4) . This process offers the potential of higher rates than cold solvent VAPEX at less energy consumption than SAGD.Hybrid steam-solvent processes, when fully developed, will extract oil at lower cost than SAGD and will also open currently marginal resources for exploitation, increasing oil reserves. This paper presents and discusses the principal concepts and key parameters for the new hybrid steam-solvent processes and compares expected performance to SAGD.