Oil & Natural Gas Projects
Exploration and Production Technologies
Development of Shallow Viscous Oil Reserves on the North Slope
This project was selected in response to DOE's Oil Exploration and Production
solicitation DE-PS26-01NT41048, Round 2 (focus area: Reservoir Efficiency Processes).
The focus area addresses access to oil not recoverable by conventional methods.
Researchers may develop unconventional recovery methods such as gas flooding,
heavy oil recovery, the use of chemicals, reservoir simulation, or microbes.
The project was designed to develop tools to find optimum solvents, injection
schedules, and well architecture for a water-alternating-gas (WAG) oil recovery
process for the Alaska North Slope's shallow, viscous oil reservoirs.
University of Houston
The results of the research established the EOR methods that will yield the
greatest recovery from the North Slope's heavy oil reservoirs. It determined
- Carbon dioxide injection works better than injection of Prudhoe Bay natural
gas liquids (NGL).
- Simulation modeling demonstrated the best strategy for timing and volume of
- Although sweep efficiency may decrease somewhat, horizontal wells were found
to deliver more heavy oil than vertical wells. The factors that influence horizontal
well performance were identified and can be used to plan horizontal wellbores
and predict recovery.
- The use of electromagnetic heating of the reservoir can double the recovery
of heavy oil.
An economic method of recovery for the enormous heavy oil resources on the
North Slope has been the goal of North Slope operators for years. The technologies
and strategies for heavy oil recovery developed by the project to optimize
production through WAG injection via horizontal wellbores will significantly
increase heavy oil production.
The combination of new technologies and a better understanding of what methods
work best in Alaskan heavy oil reservoirs can stimulate increased heavy oil
production on the North Slope and provide continued flow on the Trans-Alaska
Pipeline System (TAPS).
The disposal of CO2 via injection in an EOR project will be an added environmental
benefit as sequestration of a greenhouse gas.
Prudhoe Bay and Kuparuk River fields on Alaska's North Slope are the largest
oil fields in North America. Heavy oil presents the largest potential for
undeveloped reserves from these North Slope fields. The reservoirs are the
largest undeveloped heavy oil accumulations in North America, but recovery
has proved a daunting challenge for North Slope operators. The producing formations
lie at depths of 3,000-5,000 ft in a region of deep permafrost, which causes
the heavy oil to become extremely viscous.
The North Slope fields have been exploited since the 1970s; both Prudhoe
Bay and Kuparuk River fields are now in decline. Over 20% of the Nation's
oil supply is carried by TAPS, but production declines have reduced the volume
carried by 25% from its peak capacity. Further declines in production will
make TAPS uneconomic to operate unless new resources can be developed to offset
the decline restore pipeline throughput. The estimated resource of heavy oil
on the North Slope recoverable with current technology is 10-20 billion barrels.
Waterflood pilots have been attempted in two North Slope heavy oil reservoirs:
West Sak starting in 1984 and Schrader Bluff in 1991. Initial well productivity
of 300 barrels of oil per day (19 API gravity) was considered low by North
The goal of this research project was to develop new technology to increase
well productivity as well as reservoir recovery efficiency. WAG injection
processes and modern well architectures can be effective in recovery of the
high-viscosity deposits at West Sak and Schrader Bluff. Several gas streams
are available for the WAG process on the North Slope that contain NGL and
Heavy oil samples from three North Slope reservoirs-West Sak, Schrader Bluff,
and Ugnu (the extra-heavy crude)-were studied to determine the optimal means
to increase recovery. The goal was to develop tools to find the most efficient
solvents and establish an injection schedule and well architecture for a WAG
process that would be economic for North Slope shallow, heavy oil reservoirs.
The research focused on corefloods, analysis of sweep efficiency, compositional
simulation, wettability, relative permeability analyses, and streamline-based
simulations of WAG processes and the effect of potential chemical changes.
Simulation results confirmed that injection of CO2-NGL is superior to produced
Prudhoe Bay natural gas-NGL. Aromatic solvents (toluene and decalin) were
found to work better than non-aromatic solvents, such as cyclohexane. The
chemical and solvents tests found that adhesion properties of asphaltenes
are responsible for the mixed wettability problems in the reservoirs. A streamline
module was developed that can be incorporated into existing finite difference-based
compositional simulator models for waterflood, gas flood, and WAG flood predictions.
The laboratory studies combined with field analysis indicated that horizontal
wells increase recovery significantly over the use of vertical wells but that
sweep efficiency may decrease. Electromagnetic heating as a means of well
stimulation was found to be capable of doubling oil recovery.
A 5-spot, high-pressure cell was constructed to evaluate sweep efficiency
of miscible WAG floods. WAG displacement processes reduced bypassing as compared
with the use of gas floods, and improved oil recovery in core experiments.
As the WAG ratio decreased and the slug size was increased, oil recovery improved.
The 5-spot, high-pressure cell constructed to evaluate sweep efficiency of
miscible WAG floods on Alaskan North Slope viscous oil reservoirs.
Current Status (October 2005)
Project completed on schedule.
Final report available at www.netl.doe.gov.
Project Start: September 26, 2001
Project End: September 25, 2004
DOE Contribution: $594,250
Performer Contribution: $150,000 (20% of total)
NETL - Jim Barnes (firstname.lastname@example.org or 918-699-2076)
University of Houston - Kishore Mohanty (email@example.com or 713-743-4331)