Reservoir Life Extension
One hundred forty years after the discovery of oil and the birth of the U.S. oil and gas industry, petroleum resources remaining in the ground are still double the amount producers have extracted.
Recovering these remaining oil and gas resources poses formidable technical and financial challenges.Many oil fields are in danger of being abandoned, even though they retain one-half to two-thirds of their original oil.
The high capital cost of drilling wells and the difficulty of restoring production leases makes it unlikely that abandoned fields will ever be reopened, even if future oil prices increase significantly. Premature abandonment of wells, in effect, permanently cuts off access to valuable oil assets.
By the year 2015, an estimated one-half of the gas produced in the U.S. is projected to come from low permeability and other unconventional reservoirs. In many reservoirs producing natural gas, previously unrecognized gas-producing zones can be brought into production, thereby extending the life of these gas reservoirs.
DOE, in partnership with the U.S. oil and gas industry, supports the development of innovative and cost-effective technologies that can recover oil and gas from hard to produce resources and extend the productive life of domestic reservoirs.
By encouraging advances in oil and gas recovery technologies and facilitating their transfer to producers, DOE can help increase production from U.S. oil and gas resources, help to slow the rate of premature abandonment, and reduce our reliance on energy imports.
Lower-cost, advanced technologies and efficient development strategies, if widely applied by the Nation's oil and gas producers, are estimated to be capable of increasing the yield of tertiary oil recovery by up to one million barrels of oil per day, and the annual yield of natural gas by up to 6 Tcf per year by the year 2015.
Typically, only about one-third of the oil discovered can be produced economically. Production at most petroleum reservoirs includes three distinct elements: primary, secondary, and tertiary recovery.
Tertiary oil recovery is also known as improved oil recovery (IOR), or enhanced oil recovery (EOR).Primary recovery refers to oil production when energy stored in the reservoir is sufficient to drive the oil through reservoir rock into a wellbore.
As reservoir pressure declines with oil production rates, additional oil can be recovered using secondary recovery techniques. One such technology, waterflooding, displaces the oil and drives it to the wellbores of the producing wells.
Oil displacement in the reservoir is incomplete, however, even with secondary recovery processes. Tertiary oil recovery technologies – such as thermal, gas-miscible, chemical, or microbial methods - can provide additional production.
Such technologies potentially could lead to substantially higher average recovery efficiency, approaching 50 percent of the "original-oil-in-place" in reservoirs that have "discovered but unrecovered" oil.
Although improved oil recovery technologies have significant potential to extend reservoir life, and have been successfully demonstrated in the laboratory and in the field since the early 1960s, their historically high cost has limited their widespread application.
In the last decade, however, dramatic improvements in analytical and assessment tools have led to a greater understanding of reservoir geology and the physical and chemical processes governing multi-phase flow in porous media.
This understanding has led to the development of new technologies for reservoir life extension.
Enhancing Gas Production:
Problems associated with more efficient or complete gas recovery are somewhat different. In low permeability formations, natural fractures create channels for gas to flow through the rock formation to production wells.
However, they often cause gas to drain in irregular, elongated patterns, reducing the overall amount of gas that can be produced. In addition, natural fractures are not often intersected by vertical production wells.
Current laws regarding the spacing of production wells often limit the recovery of gas. In Colorado, research by DOE, industry, and others has helped to change the well spacing to increase the amount of gas that can be recovered.
Research conducted by the Texas Bureau of Economic Geology, on behalf of DOE and the Gas Research Institute, has also demonstrated that current production practices fail to recover a large portion of the gas-in-place.
Even after 50 years of commercial production, substantial infield reserve growth exists in bypassed, incompletely drained, and untapped reservoir compartments, not to mention deeper pool potential in many fields.
The DOE natural gas recovery program focuses on a more complete haracterization of complex heterogeneous reservoirs to afford a more precise placement of new wells and recompletions in existing wells.
The $115 million Reservoir Class Field Demonstration Program enabled 29 projects that are expected to result in 500 million barrels of oil by 2002. The current market value of that oil is $6 billion (at $12/barrel). The 6 Tcf per year of additional gas recovery that is projected with advancements in technologies is worth $9 billion annually (at $1.50 per Mcf).
Individual projects within the Reservoir Life Extension Program are selected for their potential application through-out the domestic oil and gas industry. Research dollars are focused on those oil and gas reservoirs that have vast resource estimates, or are threatened by premature abandonment.
Geologic class was chosen as the mechanism for clustering the oil and gas reservoirs immediately available for technology application. This assumes that reservoirs in the same geologic classes will experience similar technical barriers, and as a result, technology that has been successfully field tested for one reservoir in a geologic class should be suitable for another reservoir in a field of the same geologic class.
Industry cost-sharing is almost 60 percent for reservoir class field demonstration and secondary gas recovery projects, which are conducted at actual producing sites.
Source: United States Energy Information Administrati
© 2000 Mena Report (www.menareport.com)