Fundamental PVT Calculations for Associated and Gas/Condensate Natural-Gas Systems
- Robert P. Sutton (Marathon Oil Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- June 2007
- Document Type
- Journal Paper
- 270 - 284
- 2007. Society of Petroleum Engineers
- 1.10 Drilling Equipment, 4.6 Natural Gas, 4.1.5 Processing Equipment, 5.8.8 Gas-condensate reservoirs, 4.1.2 Separation and Treating, 5.4.3 Gas Cycling, 5.2 Reservoir Fluid Dynamics, 4.6.2 Liquified Natural Gas (LNG), 5.2.2 Fluid Modeling, Equations of State, 5.2.1 Phase Behavior and PVT Measurements, 4.3.4 Scale, 5.1.8 Seismic Modelling, 5.3.2 Multiphase Flow
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Problems with existing procedures used to estimate gas pressure/volume/temperature (PVT) properties are identified. The situation is reviewed, and methods are proposed to alleviate these problems. Natural gases are derived from two basic sources: associated gas, which is liberated from oil, and gas condensates, where hydrocarbon liquid, if present, is vaporized in the gas phase. The two gases are fundamentally different in that a high-gravity associated gas is typically rich in ethane through pentane, while gas condensates are rich in heptanes-plus. Additionally, either type of gas may contain nonhydrocarbon impurities such as hydrogen sulfide, carbon dioxide, and nitrogen. Failure to distinguish properly between the two types of gases can result in calculation errors in excess of those allowable for technical work. Sutton (1985) investigated high-gravity gas/condensate gases and developed methods for estimating pseudocritical properties that resulted in more-accurate Z factors. The method is suitable for all light natural gases and the heavier gas/condensate gases. It should not be used for high-gravity hydrocarbon gases that do not contain a significant heptanes-plus component. The original Sutton database of gas/condensate PVT properties has been expanded to 2,264 gas compositions with more than 10,000 gas-compressibility-factor measurements. A database of associated-gas compositions containing more than 3,200 compositions has been created to evaluate suitable methods for estimating PVT properties for this category of gas. Pure-component data for methane (CH4), methane-propane, methane-n-butane, methane-n-decane, and methane-propane-n-decane have been compiled to determine the suitability of the derived methods. The Wichert (1970) database of sour-gas-compressibility factors has been supplemented with additional field and pure-component data to investigate suitable adjustments to pseudocritical properties that ensure accurate estimates of compressibility factors. Mathematical representations of compressibility-factor charts commonly used by the engineering community and methods used by the geophysics community are investigated. Generally, these representations/methods are robust and have been found suitable for ranges beyond those recommended originally. Natural-gas viscosity, typically estimated through correlation, has been found to be inadequate for high-gravity gas condensates, requiring revised procedures for accurate calculations.
Since its publication, the Standing and Katz (1942) (SK) gas Z-factor chart has become a standard in the industry. Several very accurate methods have been developed to represent the chart digitally. The engineering community typically uses methods published by Hall and Yarborough (1973, 1974) (HY), Dranchuk et al. (1974) (DPR), and Dranchuk and Abou-Kassem (1975) (DAK). These methods all use some form of an equation of state that has been fitted specifically to selected digital Z-factor-chart data published by Poettmann and Carpenter (1952). The geophysics community typically uses a method developed by Batzle and Wang (1992) (BW). Recently, Londono et al. (2002) (LAB) refitted the chart with an expanded data set, resulting in a modified DAK method. They provided two equations: one fit to an expanded data set from the SK Z-factor chart and another that included pure-component data.
A general gas Z-factor chart, such as the one developed by Standing and Katz (1942), is based on the principle of corresponding states (Katz et al. 1959). This principle states that two substances at the same conditions referenced to critical pressure and critical temperature will have similar properties. These conditions are referred to as reduced pressure and reduced temperature. Therefore, if two substances are compared at the same reduced conditions, the substances will have similar properties. In the context of this paper, the property of interest is the gas Z factor. Mathematically, the SK chart relates Z factor to reduced pressure and reduced temperature.
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Abd-El Fattah, K.A. 1997. New GasPseudocritical Property Equations Developed. Oil & Gas J. (2 June1997) 144-145.
Audonnet, F. and Padua, A.A.H. 2004.Viscosity and Density of Mixtures of Methane and n-Decane from 298 to 393 K andup to 75 MPa. Fluid Phase Equilibria, 235-244. DOI: 10.1016/j.fluid.2003.10.017.
Batzle, M. and Wang, Z. 1992. SeismicProperties of Pore Fluids. Geophysics (November 1992) 1396-1408. DOI: 10.1190/1.1443207.
Borges, P.R. 1991. Correction ImprovesZ-Factor Values for High Gas Density. Oil & Gas J. (4 March 1991)55.
Bradley, H.B., ed. 1987. PetroleumEngineering Handbook, Chapter 39. Richardson, Texas: SPE.
Brown, G.G. and Holcomb, D.E. 1940. TheCompressibility of Gases, Part II—Gaseous Mixtures. The PetroleumEngineer (February 1940) 23-26.
Brown, G.G., Katz, D.L., Oberfell, G.G.,and Alden, R.C. 1948. Natural Gasoline and the Volatile Hydrocarbons.Tulsa: NGAA.
Canet, X., Baylaucq, A., and Boned, C.2002. High-Pressure (up to 140 MPa) Dynamic Viscosity of the Methane+DecaneSystem. Intl. J. Therm. (November 2002) 1469-1486. DOI: 10.1023/A:1020781715494.
Carr, N.L., Kobayashi, R., and Burrows,D.B. 1954. Viscosity of Hydrocarbon Gases Under Pressure. Trans., AIME201: 264-272.
Coats, K.H. 1985. Simulation of Gas CondensateReservoir Performance. JPT 37 (10): 1870-1886.SPE-10512-PA. DOI: 10.2118/10512-PA.
Coats, K.H. and Smart, G.T. 1986. Application of a Regression-Based EOSPVT Program to Laboratory Data. SPERE 1 (3): 277-299.SPE-11197-PA. DOI: 10.2118/11197-PA.
Dean, D.E. and Stiel, L.I. 1965. TheViscosity of Nonpolar Gas Mixtures at Moderate and High Pressures. AIChEJ. (May 1965) 526-532. DOI: 10.1002/aic.690110330.
Dempsey, J.R. 1965. Computer RoutineTreats Gas Viscosity as a Variable. Oil & Gas J. (16 August 1965)141-143.
Dranchuk, P.M. and Abou-Kassem, J.H.1975. Calculation of Z Factors For Natural Gases Using Equations of State.J. Cdn. Pet. Tech. (July-September 1975) 34-36.
Dranchuk, P.M., Islam, M.R., and Bentsen,R.G. 1986. A Mathematical Representation of the Carr, Kobayashi and BurrowsNatural Gas Viscosity Correlations. J. Cdn. Pet. Tech. (January-February1986) 51-56.
Dranchuk, P.M., Purvis, R.A., andRobinson, D.B. 1974. Computer Calculation of Natural Gas CompressibilityFactors Using the Standing and Katz Correlations. London: Institute ofPetroleum Technical Series, No. IP74-008: 1-13.
Drohm, J.K., Trengrove, R.D., andGoldthorpe, W.H. 1988. On theQuality of Data From Standard Gas-Condensate PVT Experiments. Paper SPE17768 presented at the SPE Gas Technology Symposium, Dallas, 13-15 June. DOI:10.2118/17768-MS.
Eilerts, C.K. 1959. Phase Relations ofGas-Condensate Fluids, Vol. II, 764-770. Monograph 10, Bureau of Mines,American Gas Association.
Elsharkawy, A.M. 2003. PredictingVolumetric and Transport Properties of Sour Gases and Gas Condensates UsingEOSs, Corresponding State Models, and Empirical Correlations. Pet. Sci.Tech. 21 (11-12): 1759-1787. DOI: 10.1081/LFT-120024560.
Elsharkawy, A.M. and Elkamel, A. 2000. Compressibility Factor for Sour GasReservoirs. Paper SPE 64284 presented at the SPE Asia Pacific Oil and GasConference and Exhibition, Brisbane, Australia, 16-18 October. DOI:10.2118/64284-MS.
Elsharkawy, A.M., Hashem, Y.Kh., andAlikhan, A.A. 2000. Compressibility Factor for GasCondensates. Paper SPE 59702 presented at the SPE Permian Basin Oil and GasRecovery Conference, Midland, Texas, 21-23 March. DOI:10.2118/59702-MS.
Engineering Data Book,9th edition, Section 16. 1972. Tulsa: GasProcessors Suppliers Association.
Eslami, H. 2001. Prediction of theDensity for Natural Gas and Liquefied Natural Gas Mixtures. AIChE J.(November 2001) 2585-2592. DOI: 10.1002/aic.690471121.
Gonzalez, M.H., Eakin, B.E., and Lee,A.L. 1970. Viscosity of Natural Gases, Monograph on API Research Project65. Washington, DC: American Petroleum Institute.
Hall, K.R. and Yarborough, L. 1973. A NewEquation of State for Z-Factor Calculations. Oil & Gas J. (18 June1973) 82-85, 90, 92.
Hall, K.R. and Yarborough, L. 1974. Howto Solve Equation of State for Z-Factors. Oil & Gas J. (18 February1974) 86-88.
Joffe, J. 1947. Compressibilities of GasMixtures. Ind. Eng. Chem. (July 1947) 837-838. DOI: 10.1021/ie50451a007.
Jossi, J.A., Stiel, L.I., and Thodos G.1962. The Viscosity of Pure Substances in the Dense Gaseous and Liquid Phases.AIChE J. 8 (1): 59-62. DOI: 10.1002/aic.690080116.
Katz, D.L., Cornell, D., Kobayashi, R. etal. 1959. Handbook of Natural Gas Engineering. New York City:McGraw-Hill Book Co.
Kay, W.B. 1936. Density of HydrocarbonGases and Vapors at High Temperature and Pressure. Ind. Eng.Chem. (September 1936) 1014-1019. DOI: 10.1021/ie50321a008.
Kenyon, D.E. and Behie, G.A. 1987. Third SPE Comparative SolutionProject: Gas Cycling of Retrograde Condensate Reservoirs. JPT39 (8): 981-997. SPE-12278-PA. DOI: 10.2118/12278-PA.
Knapstad, B., Skjolsvik, P.A., and Oye,H.A. 1990. Viscosity of the n-Decane-Methane System in the Liquid Phase.Ber. Bunsenges Phys. Chem., 1156-1165.
Lawal, A.S., Van derLaan, E.T., andThambynayagam, R.K.M. 1985. Four-Parameter Modification of theLawal-Lake-Silberberg Equation of State for Calculating Gas-Condensate PhaseEquilibria. Paper SPE 14269 presented at the SPE Annual TechnicalConference and Exhibition, Las Vegas, Nevada, 22-26 September. DOI:10.2118/14269-MS.
Lee, A.L. 1965. Viscosity of LightHydrocarbons, Monograph on API Research Project 65. Washington, DC:API.
Lee, A.L., Gonzalez, M.H., and Eakin,B.E. 1966. The Viscosity of NaturalGases. JPT 18 (8): 997-1000; Trans., AIME,237. SPE-1340-PA. DOI: 10.2118/1340-PA.
Lee, J. and Wattenbarger, R.A. 1996.Gas Reservoir Engineering, 334. Textbook Series, SPE, Richardson,Texas.
Lemmon, E.W., McLinden, M.O., and Friend,D.G. 2005. Thermophysical Properties of Fluid Systems. In NIST ChemistryWebBook, NIST Standard Reference Database Number 69, ed. P.J. Linstrom andW.G. Mallard. Gaithersburg Maryland: National Institute of Standards andTechnology. http://webbook.nist.gov.
Li, Q. and Guo, T.M. 1991. A Study on theSupercompressibility and Compressibility Factors of Natural Gas Mixtures. J.Pet. Sci. Eng., 235-247. DOI: 10.1016/0920-4105(91)90016-G.
Lohrenz, J., Bray, B.G., and Clark, C.R.1964. Calculating Viscosities ofReservoir Fluids From Their Compositions. JPT 16 (10):1171-1176; Trans., AIME, 231. SPE-915-PA. DOI:10.2118/915-PA.
Londono, F.E., Archer, R.A., andBlasingame, T.A. 2002. SimplifiedCorrelations for Hydrocarbon Gas Viscosity and Gas Density—Validation andCorrelation of Behavior Using a Large-Scale Database. Paper SPE 75721presented at the SPE Gas Technology Symposium, Calgary, 30 April-2 May. DOI:10.2118/75721-MS.
Lucas, K. 1981. Chem. Ing. Tech.53: 959-960.
Matthews, T.A., Roland, C.H., and Katz,D.L. 1942. High Pressure Gas Measurement, Part I, The Density of Natural Gas.Refiner & Natural Gasoline Manufacturer (June 1942)58-63.
Piper, L.D., McCain, W.D. Jr., andCorredor, J.H. 1993. Compressibility Factors for NaturallyOccurring Petroleum Gases. Paper SPE 26668 presented at the SPE AnnualTechnical Conference and Exhibition, Houston, 3-6 October. DOI:10.2118/26668-MS.
Poettmann, F.H. and Carpenter, P.G. 1952.The Multiphase Flow of Gas, Oil, and Water Through Vertical Flow Strings withApplication to the Design of Gas Lift Installations. Drill. and Prod.Prac., API, 257-317.
Poling, B.E., Prausnitz, J.M., andO'Connell, J.P. 2001. The Properties of Gases and Liquids, 5th edition,Chapters 5 and 9. McGraw-Hill.
Prausnitz, J.M. and Gunn, R.D. 1958.Pseudocritical Constants from Volumetric Data for Gas Mixtures. AIChE J.(December) 494. DOI: 10.1002/aic.690040421.
Reamer, H.H., Olds, R.H., Sage, B.H., andLacey, W.N. 1944. Phase Equilibria in Hydrocarbon Systems. Methane-CarbonDioxide System in the Gaseous Region. Ind. Eng. Chem. (January1944) 88-90. DOI: 10.1021/ie50409a019.
Reservoir FluidDatabase. 2003. Houston: GeoMarkResearch.http://www.rfdbase.com.
Sage, B.H. and Berry, V.M. 1971. PhaseEquilibria in Hydrocarbon Systems Behavior of the Methane-Propane-nDecaneSystem, Monograph on API Research Project 37. Washington, DC:API.
Sage, B.H. and Lacey, W.N. 1950.Thermodynamic Properties of the Lighter Paraffin Hydrocarbons andNitrogen, Monograph on API Research Project 37. Washington, DC:API.
Sage, B.H. and Lacey, W.N. 1955. SomeProperties of the Lighter Hydrocarbons, Hydrogen Sulfide, and CarbonDioxide, Monograph on API Research Project 37. Washington, DC:API.
Sage, B.H. and Reamer, H.H. 1941.Volumetric Behavior of Oil and Gas From the Rio Bravo Field. Trans.,AIME 142: 179-191.
Standing, M.B. 1981. Volumetric andPhase Behavior of Oil Hydrocarbon Systems, 9th printing. Richardson, Texas: SPE.
Standing, M.B. and Katz, D.L. 1942.Density of Natural Gases. Trans., AIME 146:140-149.
Starling, K.E. and Ellington, R.T. 1964.Viscosity Correlations for Nonpolar Dense Fluids. AIChE J. (January)11-15. DOI: 10.1002/aic.690100112.
Stewart, W.F., Burkhardt, S.F., and Voo,D. 1959. Prediction of Pseudocritical Parameters for Mixtures. Paper presentedat the AIChE Meeting, Kansas City, Missouri, 18 May.
Sutton, R.P. 1985. Compressibility Factors forHigh-Molecular-Weight Reservoir Gases. Paper SPE 14265 presented at the SPE Annual Technical Conference andExhibition, Las Vegas, Nevada, 22-26 September. DOI:10.2118/14265-MS.
Whitson, C.H. and Torp, S.B. 1983. Evaluating Constant-Volume DepletionData. JPT 35 (3): 610-620. SPE-10067-PA. DOI:10.2118/10067-PA.
Wichert, E. 1970. Compressibility Factorof Sour Natural Gases. M. Eng. thesis. Calgary: University ofCalgary.
Wichert, E. and Aziz, K. 1972. CalculateZ's for Sour Gases. Hyd. Proc. (May 1972) 119-122.
Yang, T., Chen, W.D., and Guo, T.M. 1997.Phase Behavior of a Near-Critical Reservoir Fluid Mixture. Fluid PhaseEquilibria, 183-197. DOI: 10.1016/S0378-3812(96)03163-9.