Exploration and Production Technologies

Transformation of Resources to Reserves: Next Generation Heavy Oil Techniques

DE-FC26-04NT15526

Project Goal
In broad terms, the goals of the research are to improve understanding of primary and thermal heavy oil recovery mechanisms so that recovery efficiency increases and heavy oil that is not producible by conventional means becomes accessible. The objective is to provide the technical understanding required to bring more heavy oil reservoirs into economic production, so that resources are utilized with minimum environmental impact and the amount of oil remaining at abandonment is reduced.

Performer 
Stanford University, Stanford, CA

Results 
Results to date include the following:

  • A review of the knowledge base with respect to thermal well completions found that significant technology is available for development in cold environments.
  • The development and validation of a semianalytical model for cyclic steaming in horizontal wells.
  • An understanding of the role that hydraulically fractured wells might play in thermal recovery processes.
  • Experiments that analyze foam generation mechanisms in micromodels reinforce prior work that asserted “snap off” as a dominant foam generation mechanism.
  • Chemical analysis of heavy and viscous oils displays considerable variation in acid and base numbers. These differences appear to be indicators of oils that present favorable recovery characteristics by heavy oil solution gas drive.

Benefits 
This research will increase the utilization of heavy oil resources and significantly improve recovery efficiency. The project seeks to show how the maximum volume of heavy oil is recovered without the addition of heat to the reservoir. This will reduce, and in some cases eliminate, the total amount of heat needed for EOR, resulting in significant cost savings and environmental benefits. An additional benefit to industry is that the mechanism for academia-industry interaction is active and involves regular exchange of ideas through meetings, advance copies of papers and reports, and informal contact. This significantly reduces the cycle time between research idea, research result, and assimilation of results by industry into its workflow.

Background
The United States relies more extensively on imported oil year by year. Yet the current situation has emerged not because the America lacks substantial oil and gas resources. Rather, we have not been successful at developing cost-effective production techniques that allow us to convert known resources into reserves. A case in point is heavy oil. Estimates place the total heavy oil resource (less than 20° API gravity) in the United States at 200 billion barrels of oil. At current consumption rates, this resource represents about 45 years of total oil supply for the United States. It is also noteworthy that the total amount of all heavy hydrocarbon resources in the Western Hemisphere (including heavy oil, tar sands, and oil shale) is well in excess of 5.5 trillion barrels. The oil resource of the Middle East is estimated as 1.4 trillion barrels.

The chief problem with heavy oil is economic exploitation of the resource. Heavy oils are thick and viscous, resulting in low-productivity wells. Thermal recovery, and steam injection in particular, is tremendously successful because heat thins heavy oils. Nevertheless, conventional steam injection candidates are limited to onshore, relatively shallow, thick, permeable, and homogeneous sands where benign surface conditions exist. A suite of heavy oil recovery methods is needed to address recovery across the broad range of heavy oil viscosity.

Summary 
The primary project tasks center on the areas of cold production and thermal recovery.

The objective of the cold production task is to develop a conceptual model for heavy oil solution gas drive and to translate this conceptual model into a numerical model. Experiments will be conducted using representative crude oils in sands, undertaking physical measurements as well as model development to further the interpretation of experiments and to provide a means of scaling from laboratory to field conditions.

The objective of the thermal recovery task is to lay the technical foundations of successful thermal recovery processes for heavy oil in arctic or offshore conditions. Key components of this effort are cyclic steam injection and mobility control of steam using aqueous foams. The rationale is that when viewed solely from a reservoir perspective, thermal EOR—and most likely steam injection in particular—is clearly the preferred option. Heating reduces oil viscosity substantially, thereby improving flow rates and speeding ultimate recovery. The presence of permafrost to depths of roughly 2,000 feet, however, leads most to summarily discount thermal recovery for arctic conditions. This task makes a complete case for thermal oil recovery by considering everything from well completions through mobility control.

Current Status (July 2007) 
The project has been completed and a Final Report has been submitted. Significant progress was made in the area of cold production experiments and chemical analyses using crude oil from West Sak oilfield on Alaska’s North Slope. Research on this experimental system has examined the role of initial water saturation on oil recovery during primary, solution gas drive. Theoretical aspects leading to the prediction of cold production results have also been completed. Efforts in the area of mobility control of steam using aqueous surfactants with wells in a gravity drainage geometry are also complete.

Funding 
This project was selected in response to DOE’s Oil Exploration and Production solicitation DE-PS-04NT15450-3C, November 4, 2003. Due to reductions of funding for the Oil Research Program, this project was terminated.

Project Start: October 1, 2004 
Project End: June 30, 2007

Anticipated DOE Contribution: $533,221 
Performer Contribution: $134,562 (20 percent of total)

Contact Information
NETL - Sue Mehlhoff (sue.mehlhoff@netl.doe.gov or 918-699-2044)
Stanford U. - Anthony Kovscek (kovscek@pangea.stanford.edu or 650-723-1218)

Publications
Transformation of Resources to Reserves: Next Generation Heavy Oil Techniques, Semi-Annual Technical Progress Report. Reporting Period Oct. 1, 2004-Mar. 31, 2005.

Transformation of Resources to Reserves: Next-Generation Heavy Oil Techniques, Semi-Annual Technical Progress Report for the period October 1, 2005-April 30, 2006.

Transformation of Resources to Reserves: Next-Generation Heavy Oil Technologies, Semi-Annual Technical Progress Report for the period April 1, 2005-September 30, 2005.

Fluid production from core tests using crude oil with low- and high-acid number. In the high-acid number case (b), significant gas production occurs as relatively small, foam-like bubbles.

Oil production from sandpack depletion tests using recombined West Sak oil. Initial water saturation is 0. The chart displays appreciable cold, primary recovery.

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