Evaluation of Recovery Technologies for the Grosmont Carbonate Reservoirs

Starting in the 1970s, Union Oil Company of Canada (Unocal), in partnership with Canadian Superior and the Alberta Government, conducted a series of exploratory field tests in the bitumen-saturated carbonate rocks of the Grosmont Formation. These tests applied thermal recovery technologies, including steam drive and cyclic steam stimulation (CSS), that were in their early stages of development. Significant amounts of production and observational data were obtained. Although some results were encouraging, activities in Grosmont were eventually stalled in the mid 1980s as economic attention was shifted to Cold Lake and Athabasca Cretaceous siliclastic reservoirs. Since then, in situ bitumen recovery, 3D seismic, horizontal well and surface processing technologies have matured significantly. In light of the enormous resources (406 billion barrels) hosted within the Grosmont Formation, it is pertinent to ask whether those new technologies are applicable for carbonate reservoir development.To answer this question, we studied data from the Unocal pilots conducted in the Grosmont C and augmented it with recent laboratory tests on newly acquired Grosmont C cores. The previous pilot CSS results were encouraging, with the cycle steam-tooil ratio as low as 3.65 and a peak rate of 440 bbls/d from a single vertical well. With subsequent cycles the ratio of the produced fluid to the injected fluid increased, signifying the injected energy was retained and more effective in later cycles. The operation strategy of the Unocal pilots and its implementation were not optimal and we believe that this could be improved with modern techniques.Based on our new understanding of the Grosmont Formation and specifically the Grosmont C, a numerical model was created and verified with production data. Model results indicate that the application of SAGD will be a commercially viable recovery process for Grosmont carbonate reservoirs and that low pressure injection (below 3500kPa) would be desirable. The laboratory tests not only support these conclusions but also suggest that performance of the applicable thermal processes can be enhanced with the addition of solvent. A SAGD/solvent pilot test is planned to start up in late 2010. This pilot will be critical to the development of exploitation strategies applicable to Grosmont carbonate bitumen resources.

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“…The results from these tests were previously reported [9]. The results from these tests were previously reported [9].…”

Section: Simulation Studies On Warm Solvent Testmentioning

confidence: 86%

Evolving Recovery Technologies Directed Towards Commercial Development of the Grosmont Carbonate Reservoirs

et al. 2010

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“…A review by Edmunds et al (2009) showed that the high bulk permeability of fractured and vugular Grosmont Unit makes it an attractive target for steam recovery as well as non-thermal solvent technology based on gravity drainage. Warm solvent soak tests in laboratory on Grosmont cores, performed by Jiang et al (2010), showed nearly 50% bitumen recovery. A comparison of cyclic steam stimulation (CSS) in both Clearwater oil sands and Grosmont carbonates by Ezeuko et al (2012) indicated that the response of carbonates is completely different than that of oil sands and is very sensitive to the fracture network and steam injection pressure.…”

Section: Past Experience In Grosmontmentioning

confidence: 98%

Bitumen Recovery by the SOS-FR (Steam-Over-Solvent Injection in Fractured Reservoirs) Method: An Experimental Study on Grosmont Carbonates

2013

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The recovery of 1,600,000 cp bitumen from very heterogeneous carbonate reservoirs in the Grosmont unit in Albert is a great challenge. Steam injection alone may not be efficient due to the heterogeneous nature of the reservoir caused by natural fractures at different scales. Recent cold solvent studies showed limited recovery because of low diffusion coefficient and by-passing matrix oil. The hybrid use of steam and solvent could be an option to overcome some of these challenges. We adapted the previously introduced SOS-FR (Steam-Over-Solvent Injection in Fractured Reservoirs) method and conducted twelve experiments using preserved core samples from the Grosmont formation. The temperature used can be qualified as hot water injection thereby reducing the cost of heating the reservoir.The method applied in this study is based on soaking rather than continuous injection. The samples were immersed in hot water (90 o C) first to mimic low temperature pre-steaming to condition the reservoir for solvent injection. This was followed by a solvent soaking period under varying conditions (duration, solvent type, etc.). Heptane and the distillate obtained from a heavy oil upgrading facility were used as solvents. Finally, the core samples were soaked in hot water again. Oil recoveries varied between 40% and 90% OOIP with a mean value of 68%. Asphaltene precipitation as a percentage of OOIP was measured between 6.5wt% and 33wt%. The oil recovery and asphaltene precipitation depended on the solvent type, the solvent exposure duration, the position of matrix rock (horizontal or vertical), and the duration and number of solvent/hot water cycles. Most importantly, the last phase (hot water immersion) yielded substantial recovery of solvent diffused into matrix oil by applying a temperature value close to the boiling point of the solvent. The solvent retrieval was extremely fast and varied between 62% and 82% of the solvent diffused into the core during solvent exposure. Experimental observations look promising for further applications as indicated by the high recovery values. The important aspects are that the solvent from readily available distillates used for transportation of heavy oil are very responsive and the temperature requirement for final hot water injection applied to retrieve solvent was less than 100 o C. Solvent retrieval was extremely quick and reasonably high which is more likely to make the process economic.

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“…Field and laboratory cold-solvent-soak experiments were performed to evaluate the cold-solvent potential for the Grosmont carbonates (Edmunds et al 2009). Recently, Jiang et al (2010) conducted one warm-solventsoak experiment with butane for a Grosmont carbonate core, and achieved a 50% recovery while keeping the experimental conditions at 50 C temperature and 400-kPa pressure. These conditions mean that butane was in the vapour phase (vapour pressure of butane at 50 C is approximately 500 kPa).…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Bitumen Recovery From Fractured Carbonates Using Hot Solvents

Pathak

Babadagli

Edmunds

2013

Journal of Canadian Petroleum Technology

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With the decrease in conventional oil and gas reserves throughout the world and an ever-increasing demand for fossil-fuel-based energy and resulting high oil prices, focus has been shifting to unconventional and heavy oil and bitumen. Grosmont carbonates in northern Alberta have been estimated to contain at least 300 billion bbl of heavy oil or bitumen. However, recovering this oil is extremely difficult because of the complexity associated with carbonate reservoirs in general (e.g., the Grosmont unit is known to possess a triple-porosity system of matrix, fractures, and vugs, on the basis of core studies). The second problem is the fluid itself, which is highly viscous bitumen that is immobile at reservoir conditions. To extract this bitumen from heterogeneous carbonate rock, both heat and dilution using solvents may be needed. This paper reports the results and analysis of hot-solvent experiments conducted on original Grosmont carbonate cores.Three experiments were conducted using propane and one using butane as solvent. After heating the entire system containing the core sample, solvent gas was injected. The rock was allowed to soak in the hot solvent for a long time. The experimental temperature and pressure were decided on the basis of the results of our earlier work that suggested they be slightly above the saturation line of the particular solvent. An attempt was made to keep the conditions close to the saturation conditions of the solvent being used to maximize the dilution and, hence, the recovery. The oil produced was analyzed for viscosity and asphaltene content. The results in terms of recovery, the degree of dilution, and upgrading achieved suggested that butane was a better solvent for this bitumen. Finally, the optimum conditions for operation of the hot-solvent process were verified for Grosmont carbonates.

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Evaluation of Recovery Technologies for the Grosmont Carbonate Reservoirs

Cited by 29 publications

References 2 publications

Evolving Recovery Technologies Directed Towards Commercial Development of the Grosmont Carbonate Reservoirs

Evolving Recovery Technologies Directed Towards Commercial Development of the Grosmont Carbonate Reservoirs

Bitumen Recovery by the SOS-FR (Steam-Over-Solvent Injection in Fractured Reservoirs) Method: An Experimental Study on Grosmont Carbonates

Experimental Investigation of Bitumen Recovery From Fractured Carbonates Using Hot Solvents

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