This project will develop aperture-tolerant, chemical-based methods to reduce water channeling through voids (e.g., fractures, vugs, karst) during hydrocarbon production. The project’s two tasks will incorporate analyses of selected field applications to evaluate the efficacy and mechanism of action for different gel-treatment approaches. The objective of the first task is to develop materials that can be effectively placed and will consistently minimize water flow through voids with a wide range of apertures. The objective of the second task is to develop methods to minimize water entry into voids from the surrounding rock; this task requires chemicals (i.e., gels, polymers) that predictably and controllably reduce the permeability to water much more than that to hydrocarbon.

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

Fractures, vugs, karst, and similar void channels often cause excess water production and poor sweep efficiency in waterflooded reservoirs. In both hydraulically and naturally fractured reservoirs, void channels often allow injected fluids to flow directly between water injection and production wells. This problem is especially important for EOR projects, where high-value fluids are injected along with or in advance of the water. In production wells, void channels often extend into an aquifer—thus exacerbating water production. In many cases, gels have effectively mitigated channeling through fractures, fracture-like features, and voids. Gels have reduced channeling through fractures in waterfloods and gas floods. Gels also have reduced water production in wells where fractures, fracture-like features, and voids connect to an underlying aquifer. Although many gel treatments have been quite successful, important questions exist concerning how best to design and implement them. Current methods are very sensitive to the aperture of the fracture or void. Unfortunately, these apertures are usually not known in field applications. Thus a particular need exists for treatments that are not sensitive to the aperture of the fracture or void.

Results 
Successful developments from this project will provide substantial improvements over existing gel treatment technologies, whose reliability currently depends critically on the aperture of the void channel. The results from this work also could be applied to gas shutoff problems (e.g., CO2 channeling) and to other enhanced oil recovery (EOR) processes where channeling of expensive injection fluids is a concern.

Benefits 
By developing a blocking technology that is insensitive to the aperture of the void channel, the application of chemical blocking agents will become more reliable and widespread and will result in improved reservoir sweep efficiency and reduced water production. By reducing or eliminating wastewater from oil and gas production, we can reduce its impact on the environment in the form of salt water leaks or spills and simultaneously achieve economic benefits. In the United States alone, if only a 1% reduction in water production is achieved, $50–100 million could be saved annually.

Summary 
Project objectives entail two parallel activities. One effort will develop gel-based materials that readily penetrate a predictable distance into voids and then “set up” to effectively resist washout in voids with a wide range of apertures (e.g., fracture widths). Within this activity, researchers will investigate blocking-agent placement and washout properties as a function of 1) gelant/formed-gel composition and placement rate, 2) secondary crosslinking reactions that strengthen the gel after placement, and 3) reactive and non-reactive particulate compositions.

The second effort will utilize polymers and gels that selectively damage porous rock to inhibit water flow into voids. If water does not enter the void, it won’t channel to production wells. This effort will include 1) pore-level studies using X-ray computed microtomography to confirm the mechanism for disproportionate permeability reduction and 2) mechanistic corefloods to identify conditions of maximum disproportionate permeability reduction and reproducibility. Both tasks will involve laboratory and theoretical studies and analyses of selected field applications to evaluate the various gel treatment approaches.

(July 2007) 
The final report has been submitted and approved.

Funding 
This project was selected in response to DOE’s Oil Exploration and Production, Reservoir Efficiency Processes, Solicitation DE-PS26-04NT15450-3A, February 2, 2004.

$524,383 

$173,046 (33 percent of total)

NETL - Betty Felber (betty.felber@netl.doe.gov or 918-699-2031) 
NM PRRC - Randy Seright (randy@prrc.nmt.edu or 505-835-5571)

Publications 
Seright, R.S., “Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling,” annual technical progress report submitted to DOE, October 2006.

Seright, R.S., “Clean Up of Oil Zones after a Gel Treatment,” SPE 92772, paper presented at the 2005 SPE International Symposium on Oilfield Chemistry, Houston, TX, February 2-4, 2005.

Seright, R.S., “Optimizing Disproportionate Permeability Reduction, SPE 99443, presented at the 15th SPE/DOE Improved Oil Recovery Symposium, Tulsa, OK, April 2006.

Wang, Y., and Seright, R.S., “Correlating Gel Rheology with Behavior during Extrusion through Fractures,” SPE 99462, paper presented at the 15th SPE/DOE Improved Oil Recovery Symposium, Tulsa, OK, April 2006.

Sydansk, R.D. and Seright, R.S., “When and Where Relative Permeability Modification Water-Shutoff Treatments Can Be Successfully Applied,” SPE 99371, paper presented at the 15th SPE/DOE Improved Oil Recovery Symposium, Tulsa, OK, April 2006.

Seright, R.S., Prodanovic, M., and Lindquist, W.B., “X-Ray Computed Microtomography Studies of Fluid Partitioning in Drainage and Imbibition Before and After Gel Placement: Disproportionate Permeability Reduction,” SPE Journal, June 2006, pp. 159-170.

Seright, R.S., “Clean-Up of Oil Zones After a Gel Treatment,” SPE Production & Operations, May 2006, pp. 237-244.