Characterization of Partially Formed Polymer Gels for Application to Fractured Production Wells for Water-Shutoff Purposes

Sydansk, R.D.; Xiong, Yongqiang; Al-Dhafeeri, Abdullah M.; Schrader, Richard; Seright, R.S.

doi:10.2118/89401-ms

Cited by 28 publications

(18 citation statements)

References 18 publications

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“…More recently, it has been reported that certain relatively strong WSO gels impart RPM/DPR to fluid flow within gel-filled fractures. 45 However, because such relatively strong gels also significantly reduce the permeability to oil flow in fractures, these gels are better characterized as total shutoff gels than as RPM/DPR gels. DPR is only of value for water-shutoff treatments applied to production wells.…”

Section: Guidelines For Relative Permeability Modification Treatmentsmentioning

confidence: 99%

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Seright¹

2007

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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,...

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Section: Guidelines For Relative Permeability Modification Treatmentsmentioning

confidence: 99%

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Seright¹

2007

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“…Partially formed gels exhibit lower pressure gradients and may be able to penetrate into even tighter fractures. 34 Of course, gelants (i.e., gel formulations before reaching the gelation time) flow readily through virtually any open fracture and most porous media of moderate to high permeability. Incidentally, micro-fine cements have been used in place of more coarsely ground cements (e.g., Class H) to allow penetration into tighter voids and fractures.…”

Section: Yield Stressmentioning

confidence: 99%

“…Gels can be placed in fractures as gelants, 37 formed gels, 27,38 or partially formed gels. 34,35 Gelants (the fluid solution of crosslinker and polymer that exists before gelation) flow readily into fractures and medium to high permeability rock, exhibiting relatively low pressure gradients. However, gelants often experience problems with gravity segregation in fractures.…”

Section: Gelant/gel Properties During Placementmentioning

confidence: 99%

“…45 illustrates the differences in effective viscosities (in a 1-mm-wide fracture) for gelants, formed gels, and an intermediate category-partially formed gels. 34,35 (The x-axis plots the time from gelant preparation until injection into a fracture core.) For our 1X Cr(III)-acetate-HPAM gelant, the effective viscosity in the fracture was roughly 20 cp-the same value shown by a polymer solution that contained 0.5% HPAM, but no crosslinker.…”

Section: Gelant/gel Properties During Placementmentioning

confidence: 99%

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Conformance Improvement Using Gels

Seright¹

2004

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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...

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“…It is estimated that the total cost to separate, treat and dispose of this water is about USD 50 billion per year. Water can flow into wellbore as a result of either near wellbore problems or reservoir-related problems (Seright 2000;Sydansk 1990;Sydansk et al 2005). The mechanism that contributes to undesired water production needs be fully understood before appropriate measures can be taken.…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation and application of modified urea–formaldehyde resin water shutoff agent

Liu¹,

Zhou²,

Wu³

et al. 2016

J Petrol Explor Prod Technol

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Because of bad cement job quality, water is one big problem that causes reduction in oil production, higher water cut and lower eventual oil recovery. Usually the main way to solve this problem would be to use a cement nonselective water shutoff agent. But this agent has small plugging radius, big field test risk, poor resistance to acid/ alkali and pollutes the formation seriously. Therefore, one effective shutoff agent which can lower pollution from the formation must be developed. Making use of a large number of experiments and hard work, the curing agent, thickening agent and solid filling material are chosen. In this way modified urea-formaldehyde resin water shutoff agent is developed. The formula is as follows: 0.1-0.35 % curing agent GH-1, 0.1-1 % thickening agent KYPQ and 10-20 % solid filling material CT-1. Its performance such as curing time, viscosity and plugging strength is also studied in laboratory. Its curing time is controllable from 12 to 1200 min and the viscosity is flexible from 30 to 10,000 mPa s. Injecting this new shutoff agent into sand packs whose permeability is 7 lm 2 , the displacement pressure is up to 7 MPa. After maintaining at 70°C in an oven for 8 h, the breakthrough pressure is more than 20 MPa and the plugging ratio is more than 99 %. This water shutoff agent is successfully used in 25 oil wells. Three typical wells are chosen as examples to plug channeling or bottom water. The result of pilot test shows that the cumulative quantity of oil is 14,711 tons and the water cut rises slowly.

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Characterization of Partially Formed Polymer Gels for Application to Fractured Production Wells for Water-Shutoff Purposes

Cited by 28 publications

References 18 publications

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

Conformance Improvement Using Gels

Performance evaluation and application of modified urea–formaldehyde resin water shutoff agent

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