Pore-Scale Study of the Flow of Oil and Water through Polymer Gels

Al-Sharji, Hamed Hamoud; Grattoni, Carlos A.; Dawe, Richard A.; Zimmerman, Robert W.

doi:10.2118/56738-ms

Cited by 68 publications

(50 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This scenario is consistent with that suggested in Ref. 20. To test this hypothesis, we analyzed the largest oil blob (at S or after gel placement) as if it were a porous medium (i.e., with the oil representing the pore space, and everything outside the oil blob acting as "rock").…”

Section: In Polyethylene Additional Oil Was Not Trapped During Subsesupporting

confidence: 71%

Conformance Improvement Using Gels

Seright¹

2004

View full text Add to dashboard Cite

This report describes work performed during the third and final year of the project, "Conformance Improvement Using Gels." Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts "clean up" times for oil productivity when production wells are returned to service after application of a polymer or gel treatment.X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gelripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions.Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation.We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4) using combinations of high and low molecular weight (Mw) polymers, (5) using secondary crosslinking reactions, (6) injecting un-hydrated polymer particles, and (7) incorporating particulates. All of these methods showed promise in some aspects, but required performance improvements in other aspects. All materials investigated to date showed significant performance variations with fracture width. High pressure gradients and limited distance of penetration are common problems in tight fractures. Gravity segregation and low resistance to breaching are common problems in wide fractures. These will be key issues to address in future work.Although gels can exhibit disproportionate permeability reduction in fractures, the levels of permeability reduction for oil flow are too high to allow practical exploitation in most circumstances. In contrast, disproportionate permeability reduction provided by gels that form in porous rock (adjacent to the fractures) has considerable potential in fractured systems. ix iv EXECUTIVE SUMMARYThis report describes work performed...

show abstract

Section: In Polyethylene Additional Oil Was Not Trapped During Subsesupporting

confidence: 71%

Conformance Improvement Using Gels

Seright¹

2004

View full text Add to dashboard Cite

show abstract

“…Careful, objective analysis of the Daqing CDG field data suggest no credible, unambiguous improvement of the "CDG" flood over the normal polymer flood (especially see Tables 13 and 15 and Figs 3 ,4,10,and 11 in Ref. 116).…”

Section: Daqing Field Results Are Consistent With Nomentioning

confidence: 99%

“…The viscosity of a given concentration of anionic polymer (e.g., HPAM) is much lower in saline solutions (e.g., an ASP formulation) than in fresh water (e.g., used during the Daqing polymer floods). [2][3][4][5][6] Thus, the concentrations and expense for polymer may be unusually high when applying ASP flooding after a polymer flood.…”

Section: Mobility Control During Asp Floodingmentioning

confidence: 99%

“…[1][2][3][4][5] This disproportionate permeability reduction (or "relative permeability modification") is essential if polymers or gelants are placed in production wells without protecting hydrocarbon-productive zones. 6 With existing polymers, gels, and technology, disproportionate permeability reduction may have its greatest value when treating production wells that intersect a fracture or fracturelike features.…”

Section: Optimizing Disproportionate Permeability Reduction Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Seright¹

2007

View full text Add to dashboard Cite

DEDICATIONThis report is dedicated to Dr. Jerry Casteel, who recently retired after many years of government service. During his time with the DOE's National Petroleum Technology Office, Jerry consistently played an extremely constructive part in overseeing our research. While our government is often criticized for wasteful spending and flighty funding of ill-considered projects, Jerry was a great role model, illustrating the very best of our public servants. Being highly competent (both technically and managerially), he provided a voice of moderation and charted a steady long-term course for solving some of the nation's most difficult energy problems. We will miss his insights, his vision, his dedication to advancing petroleum engineering, and his friendship.iii ABSTRACT This final technical progress report describes work performed from October 1, 2004, through May 16, 2007, for the project, "Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling."We explored the potential of pore-filling gels for reducing excess water production from both fractured and unfractured production wells. Several gel formulations were identified that met the requirements-i.e., providing water residual resistance factors greater than 2,000 and ultimate oil residual resistance factors (F rro ) of 2 or less. Significant oil throughput was required to achieve low F rro values, suggesting that gelant penetration into porous rock must be small (a few feet or less) for existing pore-filling gels to provide effective disproportionate permeability reduction. Compared with adsorbed polymers and weak gels, strong pore-filling gels can provide greater reliability and behavior that is insensitive to the initial rock permeability.Guidance is provided on where relative-permeabiliy-modification/disproportionate-permeabilityreduction treatments can be successfully applied for use in either oil or gas production wells. When properly designed and executed, these treatments can be successfully applied to a limited range of oilfield excessive-water-production problems.We examined whether gel rheology can explain behavior during extrusion through fractures. The rheology behavior of the gels tested showed a strong parallel to the results obtained from previous gel extrusion experiments. However, for a given aperture (fracture width or plate-plate separation), the pressure gradients measured during the gel extrusion experiments were much higher than anticipated from rheology measurements. Extensive experiments established that wall slip and first normal stress difference were not responsible for the pressure gradient discrepancy. To explain the discrepancy, we noted that the aperture for gel flow (for mobile gel wormholing through concentrated immobile gel within the fracture) was much narrower than the width of the fracture.The potential of various approaches were investigated for improving sweep in parts of the Daqing Oil Field that have been EOR targets. Possibilities included (1) gel treatments that are directed at channeling through fractures,...

show abstract

“…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. The program was organized into two major tasks: (1) In-depth Treatment of Matrix Rock from Injection Wells, and (2) Treatment of Production Wells to Control Water Production.…”

Section: Introductionmentioning

confidence: 99%

Development of Polymer Gel Systems to Improve Volumetric Sweep and Reduce Producing Water/Oil Ratios

Willhite¹,

McCool²,

Green³

et al. 2005

View full text Add to dashboard Cite

Gelled polymer treatments are applied to oil reservoirs to increase oil production and to reduce water production by altering the fluid movement within the reservoir. This report describes the results of a 42-month research program that focused on the understanding of gelation chemistry and the fundamental mechanisms that alter the flows of oil and water in reservoir rocks after a gel treatment. Work was conducted on a widely applied system in the field, the partially hydrolyzed polyacrylamide-chromium acetate gel. Gelation occurs by network formation through the crosslinking of polyacrylamide molecules as a result of reaction with chromium acetate. Pre-gel aggregates form and grow as reactions between chromium acetate and polyacrylamide proceed. A rate equation that describes the reaction between chromium acetate and polymer molecules was regressed from experimental data. A mathematical model that describes the crosslinking reaction between two polymer molecules as a function of time was derived. The model was based on probability concepts and provides molecular-weight averages and molecular-weight distributions of the pre-gel aggregates as a function of time and initial system conditions. Average molecular weights of pre-gel aggregates were measured as a function of time and were comparable to model simulations. Experimental methods to determine molecular weight distributions of pre-gel aggregates were unsuccessful. Dissolution of carbonate minerals during the injection of gelants causes the pH of the gelant to increase. Chromium precipitates from solution at the higher pH values robbing the gelant of crosslinker. Experimental data on the transport of chromium acetate solutions through dolomite cores were obtained. A mathematical model that describes the transport of brine and chromium acetate solutions through rocks containing carbonate minerals was used to simulate the experimental results and data from literature. Gel treatments usually reduce the permeability to water to a greater extent than the permeability to oil is reduced. This phenomenon is referred to as disproportionate permeability reduction (DPR). Flow experiments were conducted in sandpacks to determine the effect of polymer and chromium concentrations on DPR. All gels studied reduced the permeability to water by a greater factor than the factor by which the oil permeability was reduced. Greater DPR was observed as the concentrations of polymer and chromium were increased. A conceptual model of the mechanisms responsible for DPR is presented. Primary features of the model are (1) the development of flow channels through the gel by dehydration and displacement of the gel and by re-connection of pre-treatment, residual oil volume and (2) high flow resistance in the channels during water flow is caused by significant saturations of oil remaining in the channels. A similar study of DPR was conducted in Berea sandstone cores. Both oil and water permeabilities were reduced by much smaller factors in Berea sandstone cores than in similar treatm...

show abstract

Pore-Scale Study of the Flow of Oil and Water through Polymer Gels

Cited by 68 publications

References 9 publications

Conformance Improvement Using Gels

Conformance Improvement Using Gels

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Development of Polymer Gel Systems to Improve Volumetric Sweep and Reduce Producing Water/Oil Ratios

Contact Info

Product

Resources

About