This project had two objectives: 1) to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, and 2) to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

Program
This project was selected in response to DOE's Oil Exploration and Production solicitation DE-PS26-01NT41048, focus area Reservoir Efficiency Processes.

New Mexico Petroleum Recovery Research Center
New Mexico Institute of Mining and Technology
Socorro, NM

Fractures (either natural or artificially induced) often cause excess water production and reduced oil recovery efficiency, especially during waterfloods and other IOR projects; they also constitute a channeling and water-production problem that has a high potential for successful treatment by gels and certain other chemical blocking agents. Especially in fractured production wells, gels can substantially diminish water production if the gel can reduce permeability to water much more than to oil. Studies were needed to 1) determine the correct mechanism(s) for the disproportionate permeability reduction, 2) identify conditions that maximize the phenomenon, 3) find materials and methods that make the phenomenon predictable and controllable, and 4) establish a methodology to determine how much gelant should be injected in a given fractured production well.

Project Results
This project 1) identified the mechanism for why some gels can reduce permeability to water more than to oil, 2) established the mechanism for propagation of formed gels in fractures and proposed a more credible mechanism for filter-cake formation in fractures, and 3) established a web site that allows anyone to view the state of the art in water-shutoff technology using gels.

Benefits
Understanding the mechanisms by which gels reduce water and oil production helps increase the reliability of gel treatments during water-shutoff efforts in field applications. Researchers developed a web site that details many different types of water shutoff problems and provides a water shutoff strategy with relevant field examples and important information about the properties of polymers, gelants, and gels-what they can and cannot do, where and how gel treatments should (and should not) be placed, and how to assess the effectiveness of the gel treatment. This site can be accessed at http://baervan.nmt.edu/randy/. A search engine is included that covers all the project's reports and publications, including annual reports from 1990 forward.

Bettering the performance of gels in shutting off water production in improved oil recovery (IOR) operations boosts oil production and ultimate reserves recovery while benefiting the environment through mitigating the handling and disposal of large volumes of produced water.

Project Summary
X-ray computed microtomography (XMT) was used to understand why gels reduce permeability to water more than that to oil. That work revealed that "strong" Cr(III)-acetate-HPAM gels formed in virtually all aqueous pore spaces. For normal pressure gradients, water injected after gel placement was forced to flow through the gel itself, experiencing microdarcy permeabilities. In contrast, even for relatively low-pressure gradients, oil injection destroyed gel or reduced the gel volume so as to enhance oil permeability (relative to water flow). During subsequent water flow (after oil flow and after gel placement), the gel trapped much higher levels of residual oil (relative to the Sor before gel placement)-thus again providing a permeability to water that was much less than that to oil.

This three-year project was completed September 30, 2004.

Publications 
Seright, R.S., Conformance Improvement Using Gels, Annual Technical Progress Reports, U.S. DOE Report DOE/BC/15316-2, 4, and 6, September 2002, September 2003, and September 2004. 

Sydansk, R.D., Al-Dhafeeri, A.M., Xiong, Y., and Seright, R.S., Polymer Gels Formulated with a Combination of High- and Low-Molecular-Weight Polymers Provide Improve Performances for Water-Shutoff Treatments of Fractured Production Wells, SPE Production & Facilities, November 2004, 19(4), 229-236.

Seright, R.S., Lane, R.H., and Sydansk, R.D., A Strategy for Attacking Excess Water Production, SPE Production and Facilities, August 2003, 158-169. 

Seright, R.S., An Alternative View of Filter-Cake Formation in Fractures Inspired by Cr(III)-Acetate-HPAM Gel Extrusion, SPE Production and Facilities, February 2003, 65-72.

Seright, R.S, Liang J., Lindquist, B.W., and Dunsmuir, J.H., Characterizing Disproportionate Permeability Reduction Using Synchrotron X-Ray Computed Microtomography, SPE Reservoir Evaluation & Engineering, 5(5), October 2002, 355-364.

$1,226,875

$612,518 (33.3% of total)

NETL - Jerry Casteel (jerry.casteel@npto.doe.gov or 918-699-2042)
PRRC - Randy Seright (randy@prrc.nmt.edu or 505-835-5571)