The Promise of Heavy Oil
Date: 01/07/2008
With high oil demand and prices, and production of most conventional-oil reservoirs in decline, industry focus in many parts of the world is shifting to exploitation of heavy oil.
Six to nine trillion barrels, or more than two-thirds of the world's oil resources, are heavy viscous crudes that are challenging to produce and refine. Heavy oil promises to play a major role in the future of the oil industry.
Many countries are moving to increase their production, revise reserves estimates, test new technologies and invest in infrastructure to ensure optimal exploitation of their heavy-oil resources.
The article "Highlighting Heavy Oil" in the Summer 2006 issue of the Schlumberger Oilfield Review journal describes how heavy-oil deposits are formed and reviews methods for producing them. These include open-pit mining, cold heavy oil production with sand (CHOPS), and thermally assisted technologies such as steamflooding, cyclic steam stimulation and steam-assisted gravity drainage (SAGD).
Selecting the best recovery method for a particular reservoir entails a comprehensive study of fluid properties, rock mechanics, production simulation and surface facilities.
In one example, BP Exploration (Alaska) Inc. and Schlumberger conducted a screening study to assess methods for producing the billions of barrels of high-viscosity oil in BP's Ugnu sands in the North Slope of Alaska. In addition to addressing production outcomes, the study emphasized greenhouse gas handling and minimal heat loss to overlying permafrost to bring heavy-oil developments in line with BP's Green Agenda.
To confirm the economic potential of discovery wells, companies perform drillstem tests, which produce fluid, measure pressure and flow rate, and collect fluid samples. Conducting such tests is challenging in heavy-oil reservoirs, because the fluid is viscous and formations often are unconsolidated.
To overcome these challenges, Schlumberger engineers devised a testing scheme that integrates high-resolution pressure and temperature sensors for monitoring fluid phase behavior, electrical submersible pumps for fluid lifting, multiphase flowmeters for flow-rate measurements and separators for phase separation and sampling.
In one case, Devon Energy used the system to characterize a heavy-oil reservoir in the Macaé formation in the Campos basin offshore Brazil. Increased accuracy of flow-rate data resulted in a more confident drillstem test interpretation.
Monitoring fluid flow in heavy-oil reservoirs is important for optimizing recovery methods, especially when heat is required to reduce viscosity and mobilize fluids.
In a reservoir-surveillance example, Total E&P Canada installed an optical-fiber distributed temperature sensing (DTS) system along a pilot SAGD production well to monitor temperature during production startup in the Joslyn field in Alberta, Canada. The continuous set of measurements provided by DTS instrumentation helped clarify the well's performance.
Read the article in its entirety by visiting the Oilfield Review Web site. Clients are invited to register as premium content users to access this and other recent articles in Oilfield Review.
Reference
Alboudwarej H, Felix F, Taylor S, Badry R, Bremner C, Brough B, Skeates C, Baker A, Palmer D, Pattison K, Beshry M, Krawchuk P, Brown G, Calvo R, Cañas Triana JA, Kundu D, Hathcock R, Koerner K, Hughes T, López de Cárdenas J and West C: "Highlighting Heavy Oil," Oilfield Review 18, no. 2 (Summer 2006): 34–53.
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