Parametric Investigation of WAG Floods Above the MME
- Leonardo Bermudez (University of Texas at Austin) | Russell Taylor Johns (University of Texas at Austin) | Harshad Champaklal Parakh (University of Texas at Austin)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- June 2007
- Document Type
- Journal Paper
- 224 - 234
- 2007. Society of Petroleum Engineers
- 5.3.1 Flow in Porous Media, 5.4 Enhanced Recovery, 5.4.1 Waterflooding, 5.6.4 Drillstem/Well Testing, 5.5.1 Simulator Development, 5.3.2 Multiphase Flow, 5.2.1 Phase Behavior and PVT Measurements, 5.4.2 Gas Injection Methods, 4.6 Natural Gas, 5.7.2 Recovery Factors, 4.3.4 Scale, 5.4.3 Gas Cycling, 5.5 Reservoir Simulation, 5.2 Reservoir Fluid Dynamics, 5.4.9 Miscible Methods
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Water-alternating-gas floods (WAG) are commonly used to improve sweep efficiency in heterogeneous reservoirs. There has been little reported in the literature, however, on the effectiveness of WAG processes where the gas is enriched above the minimum miscibility enrichment composition (MME). This paper examines how to optimize WAG processes for enriched gasfloods above the MME, particularly as a primary recovery method. Compositional simulations of x-z cross-sections are used to quantify the effects of WAG parameters, numerical dispersion, level of enrichment, and heterogeneity on local displacement efficiency and sweep efficiency.
The main conclusions of this research show that the richer the gas above the MME, the fewer the number of WAG cycles required for maximum oil recovery at a given WAG ratio. Another significant observation is that overenrichment above the MME improves recovery the most when the largest permeability layers are at the bottom of the reservoir. Continuous slug injection performs better than WAG when the largest permeability layers are at the bottom of the aquifer, richer gases are used, and the vertical to horizontal permeability ratio is small.
Gas enrichment is one of the important optimization variables in WAG enriched-gas floods.Recoveries from slimtube experiments with continuous gas injection often give a sharp bend at the minimum enrichment for miscibility (MME). Above the MME, slimtube recoveries do not increase significantly with enrichment. The optimum enrichment required to maximize recovery on a pattern scale in the field, however, is likely different from the MME. The difference in the optimum enrichment may be largely the result of greater mixing in the reservoir than exists in slimtubes. In addition, enrichment may impact sweep efficiency in 2D displacements. Oil and gas mixing in a reservoir can include mechanisms such as molecular diffusion, mechanical dispersion, gravity crossflow, viscous crossflow, and capillary crossflow. WAG in particular causes significant mixing of reservoir and injected fluids, depending on the total volume of the gas injected (slug volume), the WAG ratio, and the number of gas cycles or WAG frequency.
There are several reasons why recovery could increase for gas enrichments above the MME. First, the density and viscosity of the gas will increase with enrichment, which may improve sweep efficiency. Second, mixing can cause an otherwise multicontact miscible flood (MCM) to develop some two-phase flow (Johns et al. 1993; Walsh and Orr 1990; Pande and Orr 1989; Lake 1989). Richer gases mix closer to the critical locus in the two-phase zone, which causes a smaller and slower lean gas bank. A smaller lean gas bank could improve sweep efficiency. Last, richer gases, which mix near the critical locus, decrease "miscible residual oil?? by increasing the velocity of the trailing evaporation fronts.
|File Size||2 MB||Number of Pages||11|
Bermudez, L. 2002. Effect of Mixing on Gas Floods Above the MME Using Slugand WAG Injection. MS thesis. Austin, Texas:University of Texas atAustin.
Chang, Y. 1990. Development and Application of an Equation of StateCompositional Simulator. PhD dissertation. Austin, Texas:University ofTexas at Austin.
Chang, H.L., Lo, T.S., Ring, W.W., and Weisbrod, K.R. 1993. The Effects of Injectant-EnrichmentLevel on Oil Recovery in Horizontal, Gravity-Tongue-Dominated Enriched-GasDrives. Paper SPE 26084 presented at the SPE Western Regional Meeting,Anchorage, Alaska, 26-28 May. DOI: 10.2118/26084-MS.
Fayers, F.J. and Lee, S.-T. Crossflow Mechanism by Gas Drive inHeterogeneous Reservoirs. Paper SPE 24934 presented at the SPE AnnualTechnical Conference and Exhibition, Washington DC, 4-7 October. DOI:10.2118/24934-MS.
Giraud, A., Thomere, R., Gard, J., and Charles, M. 1971. A Laboratory Investigation Confirmsthe Relative Inefficiency of True Miscible Drives, and Outlines New Conceptsfor Maximizing Oil Recovery by Gas Injection. Paper SPE 3486 presented atthe Annual Fall Meeting of the Society of Petroleum Engineers of AIME, NewOrleans, 3-6 October. DOI: 10.2118/3486-MS.
Haajizadeh, M., Narayanan, R., and Waldren, D. 2001. Modeling Miscible WAG Injection EORin the Magnus Field. Paper SPE 66378 presented at the SPE ReservoirSimulation Symposium, Houston, 11-14 February. DOI: 10.2118/66378-MS.
Jarrell, P.M., Fox, C.E., Stein, M.H., and Webb, S.L. 2002. PracticalAspects of CO2 Flooding. SPE Monograph Vol. 22. Richardson,Texas: Society of Petroleum Engineers.
Jensen, J., Lake, L.W., Corbett, P.W.M., and Goggin, D.J. 2003.Statistics for Petroleum Engineers and Geoscientists. Englewood Cliffs,New Jersey: Prentice-Hall.
Jerauld, G.R. 1997. GeneralThree-Phase Relative Permeability Model for Prudhoe Bay. SPERE12 (4): 255-263. SPE-36178-PA. DOI: 10.2118/36178-PA.
Jerauld, G.R. 1998. A CaseStudy in Scaleup for Multicontact Miscible Hydrocarbon Gas Injections.Paper SPE 39626 presented at the SPE/DOE Improved Oil Recovery Symposium,Tulsa, 19-22 April. DOI: 10.2118/39626-MS.
Johns, R.T., Fayers, F.J., and Orr, F.M. 1994. Effect of Gas Enrichment andDispersion on Nearly Miscible Displacements in Condensing/VaporizingDrives. SPE ATS 2 (2): 26-34. SPE-24938-PA. DOI:10.2118/24938-PA.
Johns, R.T., Sah, P., and Subramanian, S.K. 2000a. Effect of Gas Enrichment Above theMME on Oil Recovery in Enriched-Gas Floods. SPEJ 5 (3):331-338. SPE-65704-PA. DOI: 10.2118/65704-PA.
Johns, R.T., Sah, P., and Solano, R. 2000b. Effect of Dispersion on LocalDisplacement Efficiency for Multicomponent Enriched-Gas Floods Above theMME. Paper SPE 64725 presented at the SPE International Oil and GasConference and Exhibition in China, Beijing, 7-10 November. DOI:10.2118/64725-MS.
Lake, L.W. 1989. Enhanced Oil Recovery. First edition. EnglewoodCliffs, New Jersey: Prentice Hall.
Lantz, R.B. 1970. RigorousCalculation of Miscible Displacement Using Immiscible ReservoirSimulations. SPEJ 15 (6): 192-202; Trans., AIME,249. SPE-2594-PA. DOI: 10.2118/2594-PA.
Lim, M.T. 1993. Field-Scale Modeling of Multiple Contact Miscible ProcessUsing Horizontal Wells in Heterogeneous Reservoirs. PhD dissertation. Austin,Texas: University of Texas at Austin.
Lim, M.T., Pope, G.A., Sephernoori, K., and Soni, Y. 1997. Grid Refinement Study of aHydrocarbon Miscible Gas Injection Reservoir. Paper SPE 38060 presented atthe SPE Asia Pacific Oil and Gas Conference and Exhibition, Kuala Lumpur, 14-16April. DOI: 10.2118/38060-MS.
Mahadevan, J., Lake, L.W., and Johns, R.T. 2002. Estimation of True Dispersivity inField Scale Permeable Media. Paper SPE 75247 presented at the SPE/DOEImproved Oil Recovery Symposium, Tulsa, 13-17 April. DOI: 10.2118/75247-MS.
Pande K.K. 1992. Effects ofGravity and Viscous Crossflow on Hydrocarbon Miscible Flood Performance inHeterogeneous Reservoirs. Paper SPE 24935 presented at the SPE AnnualTechnical Conference and Exhibition, Washington DC, 4-7 October. DOI:10.2118/24935-MS.
Pande, K.K. and Orr, F.M., Jr.: 1994. Effect of Viscous Crossflow onMiscibility Development in a Two-Layer Flow System: Part I—Ternary VaporizingGas Drives. SPE ATS 2 (2): 7-16. SPE-19668-PA.DOI: 10.2118/19668-PA.
Parakh, H. 2004. Simulation Study of Miscible Gas Injection for Gas EnrichedAbove the Minimum Miscibility Enrichment. MS thesis. Austin, Texas: Universityof Texas at Austin.
Peng, D.Y. and Robinson, D.B. 1976. A New Two-Constant Equation of State.Industrial and Engineering Chemistry Fundamentals 15 (1): 59-64.DOI: 10.1021/i160057a011.
Sanchez, N.L. 1999. Managementof Water Alternating Gas (WAG) Injection Projects. Paper SPE 53714presented at the SPE Latin American and Caribbean Petroleum EngineeringConference, Caracas, 21-23 April. DOI: 10.2118/53714-MS.
Solano, R., Lee, S.-T., Ballin, P.R., and Moulds, T.P. 2001a. Evaluation of the Effects ofHeterogeneity, Grid Refinement, and Capillary Pressure on Recovery forMiscible-Gas Injection Processes. Paper SPE 71602 presented at the SPEAnnual Technical Conference and Exhibition, New Orleans, 30 September-3October. DOI: 10.2118/71602-MS.
Solano, R., Johns, R.T., and Lake, L.W. 2001b. Impact of Reservoir Mixing inEnriched-Gas Drives Above the Minimum Miscibility Enrichment. SPEREE4 (5): 358-365. SPE-73829-PA. DOI: 10.2118/73829-PA.
Stalkup, F.I. 1987. Displacement Behavior of theCondensing/Vaporizing Gas Drive Process. Paper SPE 16715 presented at theSPE Annual Technical Conference and Exhibition, Dallas, 27-30 September. DOI:10.2118/16715-MS.
Stalkup, F.I. 1998. Predictingthe Effect of Continued Gas Enrichment Above the MME on Oil Recovery inEnriched Hydrocarbon Gasfloods. Paper SPE 48949 prepared for presentationat the SPE Annual Technical Conference and Exhibition, New Orleans, 27-30September. DOI: 10.2118/48949-MS.
Stalkup, F.I. 1990. Effect ofGas Enrichment and Numerical Dispersion on Enriched-Gas-Drive Prediction.SPERE 5 (4): 647-655; Trans., AIME, 289.SPE-18060-PA. DOI: 10.2118/18060-PA.
Stalkup, F.I., Lo, L.L., and Dean, R.H. 1990. Sensitivity to Gridding of MiscibleFlood Predictions Made with Upstream Differenced Simulators. Paper SPE20178 presented at the SPE/DOE Enhanced Oil Recovery Symposium, Tulsa, 22-25April. DOI: 10.2118/20178-MS.
Stone, H.L. 1973. Estimation of Three-Phase Relative Permeability andResidual Oil Data. J. Can. Pet. Tech. 12 (4): 53-61.
Walsh, B.W. and Orr, F.M. Jr. 1990. Prediction of Miscible FloodPerformance: The Effect of Dispersion on Composition Paths in Ternary Systems.In Situ 14 (1): 19-47.
Yuan, H. and Johns, R.T. 2005. Simplified Method for Calculation ofMinimum Miscibility Pressure or Enrichment. SPEJ 10 (4):416-425. SPE-77381-PA. DOI: 10.2118/77381-PA.