Characterization of Crosslinked Gel Kinetics and Gel Strength by Use of NMR
- Laura B. Romero-Zeron (U. of New Brunswick) | Florence M. Hum (U. of Calgary) | Apostolos Kantzas (U. of Calgary)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- June 2008
- Document Type
- Journal Paper
- 439 - 453
- 2008. Society of Petroleum Engineers
- 2 Well Completion, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 3 Production and Well Operations, 5.8.5 Oil Sand, Oil Shale, Bitumen, 2.2.3 Fluid Loss Control, 4.6 Natural Gas, 4.1.2 Separation and Treating, 1.6 Drilling Operations
- 4 in the last 30 days
- 1,301 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 10.00|
|SPE Non-Member Price:||USD 30.00|
Highly crosslinked gels are used in high-permeability reservoirs to achieve appropriate fluid-loss control during well completion and workover operations. Crosslinked gels are also used to shut off unwanted gas and/or water influx into production wells and to improve the conformance of the near-wellbore injection profile in naturally fractured or high-permeability reservoirs. In all these applications, the appropriate design of the gel treatment is critical to ensure an efficient gel placement. Important variables of gel systems are gel rheology and gel strength during and after the gelation reaction is completed.
The rheology of gels and gelation rates is commonly determined by rheometry or, in a qualitative mode, through bottle testing with well-known gel-strength codes (i.e., Sydansk's code). Rheological measurements can be time-consuming, while bottle testing can lead to an inconsistent gel description as a result of the subjective nature of the gel-strength code. This paper evaluates the use of low-field nuclear magnetic resonance (NMR) as a nonintrusive technique to monitor gelation rates and to characterize gel strength. Because of the nonintrusive nature of this technique, it could be considered to be a better alternative to conventional rheological measurements and common qualitative methods, such as gel-strength codes. In addition, NMR could offer faster and more accurate gel-strength characterization and gelation monitoring compared to rheological methods. Furthermore, it can be used in porous media. NMR parameters are predicted and calibrated conducting concentration sweeps of polymer, crosslinker, and brine, as well as gelation-time sweeps. This then allows for a standardized method for gel characterization.
The findings of this work include a preliminary assessment of the use of different techniques, such as low-field NMR, rheometry, and bottle testing, for monitoring the gelation reaction and gel strength of partially hydrolyzed polyacrylamide chromium [(HPAm)/Cr(III)] acetate gel. The experimental results also include the initial identification of the gel point for different formulations of the gel system using low-field NMR.
Gels are swollen polymer networks that possess the cohesive properties of solids and the diffusive transport properties of liquids. If some of the bonds holding the gel network together can "make and break," the gel is called reversible. If the bonds do not dissociate, the gel is called permanent. A permanent gel tends to carry the history of its formation in its structure, and it is best described as a crosslinked system of clusters. Clusters range from small, starlike molecules to large, heavily crosslinked, and fairly concentrated microgel cores (Silberberg 1989).
Water-based gels can be obtained by crosslinking linear flexible water-soluble polymers by use of transition-metal ions. These gels are highly elastic, with 98 to 99% water content trapped in the 3D polymer structure of the gel (Vossoughi 2000). Water-based gels exhibit a wide range of static and dynamic physical properties that make them suitable for numerous applications in the oil and gas industry (te Nijenhuis et al. 2003), such as plugging off lost-circulation zones during drilling operations, hydraulic fracturing to stimulate the production of oil and gas formations, controlling excessive water- and gas-production problems, and plugging depleted wells at the end of their economic life (Menjivar 1986; Kabir 2001).
Currently, the most widely used polymer-gel-forming compositions use either HPAm or an acrylamide copolymer and Cr(III) crosslinker (Bryant et al. 1997). This network system has been studied extensively both in the laboratory and in the field. The reliable performance of this hydrophilic-gel system in field applications requires the appropriate understanding of its physical-chemical properties and its viscoelastic behavior, as well as the interrelation of these two aspects (te Nijenhuis et al. 2003). Previous studies have mainly addressed the establishment of gelation kinetics (te Nijenhuis 2003; Menjivar 1986; Prud'homme et al. 1983; Shu 1989; Sydansk 1988; Tackett 1989; Lockhart 1994; Lockhart and Albonico 1994) and the evaluation of the rheological behavior and mechanical properties of a given gel system (Chauveteau et al. 2000; Kakadjian et al. 1999; Liu and Seright 2000; Broseta et al. 2000a; Grattoni et al. 2001; te Nijenhuis 1997).
The polymer and crosslinker usually are mixed in surface facilities, pumped downhole through coiled tubing, and injected into the formation over a depth of several feet. For the operators, gelation time, or gel point, and gel consistency after gel placement in the formation are the two most important parameters to control. The time at which the gel is "set" is known as "gel point." At this point, the solution just transforms into a gel (te Nijenhuis et al. 2003), or the crosslinking reaction begins (Seymour and Carraher 1988). Gel point, which corresponds to a sudden rise in viscosity, must be long enough to enable placement of a sufficient gel volume before gelation starts: Early network formation is undesirable (te Nijenhuis et al. 2003; Broseta et al. 2000a). Consequently, the rate at which this 3D gel is formed determines how far the solution can be pushed into the rock formation and away from the injection well before gelation occurs (Prud'homme et al. 1983). Gel consistency is related to the maximum pressure drop the gel can sustain within the porous media (Broseta et al. 2000a).
The gelation reaction of HPAm/Cr(III) acetate gels and the determination of gel point and the strength of this polymer network have been commonly studied by visual observation through bottle testing by use of a strength-code table (Sydansk 1988), through the evaluation of yield stress, or by rheological monitoring of the gelation.
This paper evaluates the use of low-field NMR as a nonintrusive technique to monitor gelation rates and to characterize gel strength. The main advantage of using low-field NMR is that it allows a simple, accurate, and fast determination of fluid physical properties, such as viscosity. Furthermore, its nondestructive attribute makes possible the characterization of polymer gels without disruption of the network structure, and it can be applied in rock formations under characteristic shear rates of gel flowing through porous media (Bryan et al. 2002b). Finally, it offers the possibility of downhole evaluation of gelation with certain well completions.
This study aims to verify the hypothesis that there is a relationship between NMR bulk relaxation rate and the density of the crosslinked network in HPAm/Cr(III) acetate gels. Thus, monitoring gel formation using low-field NMR enables the determination of gel point (the point at which crosslinking begins) (Seymour and Carraher 1988), gel strength, and the onset of gel syneresis. Three techniques are used in this work to evaluate the crosslinking process of an aqueous HPAm/Cr(III) acetate gel: bottle testing, rheometry, and low-field NMR relaxation. The characterization of the gel system is performed as a function of polymer, crosslinker, and salinity concentration.
The first part of this paper presents a brief literature review on gelation kinetics, basics of the rheological characterization of gels, and the fundamental aspects of low-field NMR theory. The second part of this work summarizes the experimental procedures and results and presents interpretation and discussion of the experimental findings.
|File Size||2 MB||Number of Pages||15|
Bartosek, M. et al. 1994. Polymer Gels for ConformanceTreatments Propagation on Cr(III) Crosslinking Complexes in Porous Media.Paper SPE 27828 presented at the SPE/DOE Symposium on Improved Oil Recovery,Tulsa, 17-20 April. DOI: 10.2118/27828-MS.
Broseta, D., Marquer, O., Blin, N., and Zaitoun, A. 2000a. Rheological Screening ofLow-Molecular-Weight Polyacrylamide/Chromium(III) Acetate Water ShutoffGels. Paper SPE 59319 presented at the SPE/DOE Improved Oil RecoverySymposium, Tulsa, 3-5 April. DOI: 10.2118/59319-MS.
Broseta, D., Marquer, O., Zaitoun, A., Baylocq, P., and Fery, J.-J. 2000b.Shear Effects onPolyacrylamide/Chromium(III) Acetate Gelation. SPEREE 3 (3):204-208. SPE-64500-PA. DOI: 10.2118/64500-PA.
Bryan, J., Kantzas, A., and Bellehumeur, C. 2002a. Viscosity Predictions for Crude Oilsand Crude Oil Emulsions Using Low Field NMR. Paper SPE 77329 presented atthe SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 29September-2 October. DOI: 10.2118/77329-MS.
Bryan, J., Manalo, F.P., Wen, Y., and Kantzas, A. 2002b. Advances in Heavy Oil and WaterProperty Measurements Using Low Field Nuclear Magnetic Resonance. Paper SPE78970 presented at the SPE International Thermal Operations and Heavy OilSymposium and International Horizontal Well Technology Conference, Calgary, 4-7November. DOI: 10.2118/78970-MS.
Bryan, J. Mirotchnik, K., and Kantzas, A. 2003. Viscosity Determination ofHeavy Oil and Bitumen Using NMR Relaxometry. J. Cdn. Pet. Tech.42 (7): 29-34.
Bryant, S.L., Bartosek, M., Lockhart, T.P., and Giacca, D. 1997. Polymer Gelants for High TemperatureWater Shutoff Applications. SPEJ 2 (4): 447-454.SPE-36911-PA. DOI: 10.2118/36911-PA.
Chauveteau, G. 1986. Fundamental Criteria in Polymer Flow Through PorousMedia. In Water-Soluble Polymers, ed. J.E. Glass, 228-267. Washington,DC: American Chemical Society.
Chauveteau, G., Omari, A., Tabary, R., Renard, M., and Rose, J. 2000. Controlling Gelation Time andMicrogel Size for Water Shutoff. Paper SPE 59317 presented at the SPE/DOEImproved Oil Recovery Symposium, Tulsa, 3-5 April. DOI: 10.2118/59317-MS.
Chiappa, L. et al. 2003. Polymer Design for RelativePermeability Modification Treatments at High Temperature. Paper SPE 80202presented at the SPE International Symposium on Oilfield Chemistry, Houston,5-7 February. DOI: 10.2118/80202-MS.
Eriksen, O.I. et al. 1997. GelFormation and Thermal Stability of Gels Made From Novel Water-Soluble Polymersfor Enhanced Oil Recovery Applications. Paper SPE 37247 presented at theSPE International Symposium on Oilfield Chemistry, Houston, 18-21 February.DOI: 10.2118/37247-MS.
Gales, J.R., Young, S., Willhite, G.P., and Green, D.W. 1994. Equilibrium Swelling and SyneresisProperties of Xanthan Gum/Cr(III) Gels. SPE Advanced TechnologySeries 2 (2): 190-198. SPE-17328-PA. DOI: 10.2118/17328-PA.
Grattoni, C.A., Al-Sharji, H.H., Yang, C., Muggeridge, A.H., and Zimmerman,R.W. 2001. Rheology andPermeability of Crosslinked Polyacrylamide Gel. Journal of Colloid andInterface Science 240 (2): 601-607. DOI: 10.1006/jcis.2001.7633.
Hurd, C.B. and Letteron, H.A. 1932. Studies on Silica Acid Gels.J. Phys. Chem. 36 (2): 604-615. DOI: 10.1021/j150332a016.
Jin, H., McCool, C.S., Willhite, G.P., Green, D.W., and Michnick, M.J. 2003.Propagation of Chromium(III)Acetate Solutions Through Dolomite Rock. SPEJ 8 (2): 107-113.SPE-84941-PA. DOI: 10.2118/84941-PA.
Kabir, A.H. 2001. ChemicalWater and Gas Shutoff Technology—An Overview. Paper SPE 72119 presented atthe SPE Asia Pacific Improved Oil Recovery Conference, Kuala Lumpur, 8-9October. DOI: 10.2118/72119-MS.
Kakadjian, S. Rauseo, O., and Mejias, F. 1999. Dynamic Rheology as a Method forQuantify Gel Strength of Water Shutoff Systems. Paper SPE 50751 presentedat the SPE International Symposium on Oilfield Chemistry, Houston, 16-19February. DOI: 10.2118/50751-MS.
Kantzas, A., Todoruk, T., Manalo, F., and Langford, C.H. 2001. A KineticModel of Imbibition in Soils. Paper SCA 2001-27. International Symposium of TheSociety of Core Analysts, Murrayfield, Edinburgh, U.K., 17-19 September.
Liu, J. and Seright, R.S. 2000. Rheology of Gels Used for ConformanceControl in Fractures. Paper SPE 59318 presented at the SPE/DOE Improved OilRecovery Symposium, Tulsa, 3-5 April. DOI: 10.2118/59318-MS.
Lockhart, T.P. 1994. ChemicalProperties of Chromium/Polyacrylamide Gels. SPE Advanced TechnologySeries 2 (2): 199-205. SPE-20998-PA. DOI: 10.2118/20998-PA.
Lockhart, T.P. and Albonico, P. 1994. New Chemistry for the Placement ofChromium(III)/Polymer Gels in High-Temperature Reservoirs. SPEPF9 (4): 273-279; Trans., SPE, 297. SPE-24194-PA. DOI:10.2118/24194-PA.
Menjivar, J. 1986. Use of Gelation Theory to Characterize Metal Cross-LinkedPolymer Gels. In Water-Soluble Polymers, ed. J.E. Glass, 209-226.Washington, DC: American Chemical Society.
Moradi-Aragui, A., Bjornson, G., and Doe, P.H. 1993. Thermally Stable Gels forNear-Wellbore Permeability Contrast Corrections. SPE Advanced TechnologySeries 1 (1): 140-145. SPE-18500-PA. DOI: 10.2118/18500-PA.
Prada, A., Civan, F., and Dalrymple, E.D. 2000. Evaluation of Gelation Systems forConformance Control. Paper SPE 59322 presented at the SPE/DOE Improved OilRecovery Symposium, Tulsa, 3-5 April. DOI: 10.2118/59322-MS.
Prud'homme R.K., Uhl, J.T., Poinsatte, J.P., and Halverson, F. 1983. Rheological Monitoring of theFormation of Polyacrylamide/Cr+3 Gels. SPEJ 23 (5): 804-808.SPE-10948-PA. DOI: 10.2118/10948-PA.
Sanders, G.S., Chambers, M.J., and Lane, R.H. 1994. Successful Gas Shutoff With PolymerGel Using Temperature Modeling and Selective Placement in the Prudhoe BayField. Paper SPE 28502 presented at the SPE Annual Technical Conference andExhibition, New Orleans, 25-28 September. DOI: 10.2118/28502-MS.
Selb, J., Biggs, S., Renoux, D., and Candau, F. 1996. Hydrophobic andElectrostatic Interactions in Water-Soluble Associating Copolymers. InHydrophilic Polymers, ed. J.E. Glass, 251-278. Washington, DC: AmericanChemical Society.
Seymour, R. and Carraher, C. 1988. Polymer Chemistry: AnIntroduction. New York City: Marcel Dekker.
Shu, P. 1989. Gelation Mechanism of Chromium(III). In Oil-FieldChemistry, ed. J. Borchardt and T. Yen, 137-144. Washington, DC: AmericanChemical Society.
Silberberg, A. 1989. Gelled Aqueous Systems. In Polymers in AqueousMedia, ed. J.E. Glass, 3-14. Washington, DC: American Chemical Society.
Suematsu, K. 2002. Recent Progress in Gel Theory:Ring, Excluded Volume, and Dimension. Advances in Polymer Science156: 137-214. DOI: 10.1007/3-540-45141-2_3.
Sydansk, R.D. 1993. Acrylamide-Polymer/Chromium(III)-CarboxylateGels for Near Wellbore Matrix Treatments. SPE Advanced TechnologySeries 1 (1): 146-152. SPE-20214-PA. DOI: 10.2118/20214-PA.
Sydansk, R.D. 1988. NewConformance-Improvement-Treatment Chromium(III) Gel Technology. Paper SPE17329 presented at the SPE Enhanced Oil Recovery Symposium, Tulsa, 16-21 April.DOI: 10.2118/17329-MS.
Tackett, J. 1989. Characterization of Chromium(III) Acetate in AqueousSolution. Applied Spectroscopy 43 (3): 490-499. DOI:10.1366/0003702894202986.
te Nijenhuis, K. 1997. Thermoreversible Networks: Viscoelastic Propertiesand Structure of Gels. Secaucus, New Jersey: Springer Verlag.
te Nijenhuis, K. 2001. Crosslink Nature in Cr(III)-Polyacrylamide Gels. Macroml. Symp.171 (1): 189-200. DOI:10.1002/1521-3900(200106)171:1<189::AID-MASY189>3.0.CO;2-2.
te Nijenhuis, K., Mensert, A., and Zitha, P.J. 2003. Viscoelastic behaviour ofpartly hydrolysed polyacrylamide/chromium(III) gels. RheologicalActa 42 (1-2): 132-141. DOI: 10.1007/s00397-002-0264-9.
Tsau, J.S., Liang, J.T., Hill, A.D., and Sepehrnoori, K. 1992. Re-Formation of Xanthan/Chromium GelsAfter Shear Degradation. SPERE 7 (1): 21-28; Trans.,SPE, 293. SPE-18506-PA. DOI: 10.2118/18506-PA.
Tung, N.P., Hung, P.V., Vinh, N.Q., and Long, B.Q.K. 2001. Research of Polyacrylamide GelApplication for Water Shutoff in High Temperature Fractured Granite BasementReservoirs. Paper SPE 72120 presented at the SPE Asia Pacific Improved OilRecovery Conference, Kuala Lumpur, 6-9 October. DOI: 10.2118/72120-MS.
Vossoughi, S. 2000. Profile modificationusing in situ gelation technology—a review. Journal of Petroleum Scienceand Engineering 26 (1-4): 199-209. DOI:10.1016/S0920-4105(00)00034-6.
Winter, H.H. 2002. The Critical Gel. Structure and Dynamics on Polymerand Colloidal Systems, R. Borsali and R. Pecora (Eds.). Series:Mathematical and Physical Sciences, Kluwer Academic Publishers, Dordrecth, TheNetherlands, 439-470.
Winter, H.H. and Mours M., 1997. Rheology of Polymers NearLiquid-Solid Transitions. Advances in Polymer Science 134:165-234. DOI: 10.1007/3-540-68449-2.
Zaiton, A., Rahbari, R., and Kohler, N. 1991. Thin Polyacrylamide Gels for WaterControl in High-Permeability Production Wells. Paper SPE 22785 presented atthe SPE Annual Technical Conference and Exhibition, Dallas, 6-9 October. DOI:10.2118/22785-MS.