Oil & Natural Gas Projects
Exploration and Production Technologies
Development of Polymer Gel Systems to Improve Volumetric Sweep and Reduce
Produced Water/Oil Ratios
The research goals are to improve the effectiveness of polymer gels to increase
volumetric sweep efficiency of fluid displacement processes and to reduce water
production in production wells. Improvements in these areas have the potential
to slow the rate of decline in oil production from existing wells and increase
the ultimate oil recovery from existing reservoirs.
University of Kansas Center for Research
Project researchers have accomplished the following:
- Development of a mathematical model that simulates polymer crosslinking processes.
- Kinetic study of the reaction between chromium acetate and polyacrylamide.
- Development of a mathematical model that simulates the transport of chromium
acetate through carbonate rocks.
- Experimental study of the effect of gelant composition and oil/water pressure
gradients on disproportionate permeability reduction (DPR).
The mathematical model and accompanied data describing the formation and growth
of pre-gel aggregates is a major advancement in the fundamental understanding
of the placement of gelants in oil reservoirs. Additionally, the role of carbonate
dissolution on the in-depth propagation of gelants is more clearly known,
and a mathematical model was developed to simulate the chemistry. These tools
allow for the improvement of current gel systems and the development of new
systems that can be applied in the field. Reduced water production from improved
systems reduces operating costs for the oil producer and mitigates environmental
concerns of large volumes of produced water. Lower operating costs extend
the life of reservoirs, resulting in increased oil recovery.
Polymer gels are being used to improve volumetric sweep efficiency in oil
recovery displacement processes and to control water flow in oil production
wells. However, the potential exists for significant improvement in these
processes with corresponding increases in oil recovery and large reductions
in operating costs due to decreased water handling.
The application of gels to improve volumetric sweep efficiency is limited
by the lack of gel systems that can be used for in-depth treatment, i.e.,
by an inability to have the gels penetrate large distances into the reservoir
away from the treated well. Researchers have demonstrated that the formation
and growth of pre-gel aggregates is a major factor that inhibits deep penetration
of gels into reservoir rock. One task of this project was to develop a mathematical
model of the aggregate growth. A second problem during the placement of gelants
occurs in carbonate reservoirs where fluid-rock interactions interfere with
the gelation chemistry. Researchers studied the role of carbonate dissolution
on the in-depth propagation of gelants.
Water production in production wells can be reduced by using gel systems
that exhibit DPR. The mechanism producing this beneficial phenomenon has been
elusive for several investigators. The project performer has developed a conceptual
model of DPR. Development of this model allows the opportunity to develop
systems that can be used to control water flow without significantly affecting
oil flow into a production well
DPR is the phenomenon whereby a gel treatment in a porous medium reduces the
water permeability by a greater factor than the oil permeability is reduced.
A conceptual model that describes mechanisms responsible for DPR was developed
from flow experiments. The model's main features are a) flow channels through
the gels are formed during the injection of oil that removes a significant
portion of the gel volume by partial displacement and dehydration of the gel;
b) high oil saturations in the channels during water flow causes the water
permeabilities to be reduced by significant factors; and c) during oil flow,
oil saturates most of the channel volume, resulting in a much smaller reduction
of the oil permeabilities. Experimental results of the effects of gelant composition
and flow rates of water and oil on DPR are presented.
A mathematical model was developed that simulates the chemical reactions
where polymer molecules are crosslinked to form a three-dimensional network
or gel. The model was based on statistical probabilities of reactions and
yields information on various molecular-weight quantities as functions of
conversion of reactive sites and time. Incorporated in this model are results
of a kinetic study of the reaction of chromium acetate and polyacrylamide,
currently the most commonly used gel system. A second mathematical model was
developed that describes the fluid-rock interactions that occur during flow
of gelant components through carbonate rocks.
Current Status (August 2005)
A six-month, no-cost extension to a three-year project extended the termination
date to December 31, 2005.
Project Start: July 1, 2002
Project End: December 31, 2005
Anticipated DOE Contribution: $ 691,443
Performer Contribution: $ 499,913 (42% of total)
NETL - Betty Felber (email@example.com or 918-699-2031)
U. of Kansas - G. Paul Willhite (Willhite@ku.edu or 785-864-2906)
Two annual reports submitted to DOE for the periods July 1, 2002, to June
30, 2003 (November 2003) and July 1, 2003, to June 30, 2004 (December 2004).
Ganguly, S., Willhite, G.P., Green, D.W., and McCool, C.S., Effect of Flow
Rate on Disproportionate Permeability Reduction, SPE 80205, SPE International
Symposium on Oilfield Chemistry, Houston, TX (February 5-7, 2003).
Jin, H., McCool, C.S., Willhite, G.P., Green, D.W., and Michnick, M.J., Propagaton
of Chromium(III) Acetate Solutions Through Dolomite Rock, SPE Journal, 8,
June 2003, pp. 107-113.
Jain, R., McCool, C.S., Green, D.W., Willhite, G.P., and Michnick, M.J.,
Reaction Kinetics of the Uptake of Chromium(III) Acetate by Polyacrylamide,
scheduled for publication in SPE Journal, December 2005.
Nguyen, T., Green, D.W., Willhite, G.P., and McCool, C.S., Effect of Composition
of a Polyacrylamide-Chromium Acetate Gel on the Magnitude of Gel Dehydration
and Disproportionate Permeability Reduction, SPE 89404, SPE/DOE Fourteenth
Symposium on Improved Recovery, Tulsa, OK, April 17-21, 2004.
Cheng, M., Wang, C., McCool, C.S., Green, D.W., and Willhite, G.P., Modeling
of Pre-Aggregate Growth During the Gelation of a Polyacrylamide-Chromium(III)
Acetate Gel System Using the Theory of Branching Processes, SPE 93354, SPE
International Symposium on Oilfield Chemistry, Houston, TX (February 2-4,