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Oil formation volume factor

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The oil formation volume factor (FVF) relates the volume of oil at stock-tank conditions to the volume of oil at elevated pressure and temperature in the reservoir. Values typically range from approximately 1.0 bbl/STB for crude oil systems containing little or no solution gas to nearly 3.0 bbl/STB for highly volatile oils.

Correlations for calculating FVF

Tables 1 and 2[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] summarize thirty correlations for saturated crude oil systems that have been identified in the literature. For saturated systems, gas is liberated as pressure is reduced below the bubblepoint. This results in a corresponding shrinkage in oil volume, as shown for all of the methods in Fig. 1. The rather large number of correlations preclude the identification of individual methods. The results show a relatively narrow range of oil FVF values determined by all of the correlation methods.

  • Fig. 1 – Gas saturated oil FVF correlation results vs. solution GOR.

    Fig. 1 – Gas saturated oil FVF correlation results vs. solution GOR.

These correlations determine FVF based on the following function.

RTENOTITLE....................(1)

Solution GOR accounts for the largest change in FVF. Increases in temperature, crude oil gravity, and gas gravity provide a small increase in FVF.

Statistical analysis of correlation performance

Recent studies[35][36][37][38] provide statistical analyses for bubblepoint oil FVF correlations and provide recommendations based on their findings; however, none of these references examines the full set of correlations. Al-Shammasi[31] compiled a databank of 1,345 data points from the literature that was combined with 133 data points from the GeoMark Research database[39] to yield a total of 1,478 data points. These data were used to rank the accuracy of the oil FVF correlations. The ranges and distribution of these data can be found in Table 3 and Fig. 2. Table 4 summarizes correlation performance. The results are sorted by absolute average relative error, which provides a means to rank the methods.

  • Table 3

    Table 3

  • Table 4

    Table 4

  • Fig. 2 – Distribution of data used to prepare PVT correlations.

    Fig. 2 – Distribution of data used to prepare PVT correlations.

Impact of gravity and GOR

The data were further grouped to examine the impact of crude oil gravity and GOR on consistency of the correlations. Methods proposed by Al-Marhoun,[23] Al-Shammasi,[31] Farshad et al.,[24] and Kartoatmodjo and Schmidt[20][21][22] showed reliability over a wide range of conditions. The author has experienced good results from both the Standing[2] and Glasø[6] correlations, although they may not have ranked highly with this data set. Fig. 3 summarizes these methods.

  • Fig. 3 – Selected oil FVF correlations.

    Fig. 3 – Selected oil FVF correlations.

Cautions in use of correlations

The correlations were tested against the other parameters used in the derivation of the methods:

  • Crude oil API gravity
  • Gas gravity
  • Temperature

Several methods use multiple equations valid for specified ranges of crude oil gravity. Discontinuities, which are summarized in Fig. 4, can result from the use of this technique to develop a correlation. Furthermore, FVF should increase with increasing API gravity. Fig. 4 shows methods that exhibit nonphysical results.

  • Fig. 4 – Oil FVF vs. crude oil API gravity.

    Fig. 4 – Oil FVF vs. crude oil API gravity.

FVF should increase with increasing solution gas gravity. Fig. 5 shows that a number of correlations predict results opposite to this trend. Correlations listed in Figs. 4 and 5 should be used with caution to avoid problems associated with discontinuities or nonphysical behavior. Limitations imposed by data used in the correlation’s development should be followed.

  • Fig. 5 – Oil FVF vs. solution gas gravity.

    Fig. 5 – Oil FVF vs. solution gas gravity.

  • Table 1

    Table 1

  • Table 2

    Table 2

Nomenclature

Bob = oil formation volume at bubblepoint pressure, bbl/STB
T = temperature, T, °F
γAPI = oil API gravity
γg = gas specific gravity, air=1
Rs = solution GOR, scf/STB

References

  1. ↑ Standing, M.B. 1947. A Pressure-Volume-Temperature Correlation for Mixtures of California Oils and Gases. API Drilling and Production Practice (1947): 275-287.
  2. ↑ 2.0 2.1 Frick, T.C. 1962. Petroleum Production Handbook, Vol. II, Chap. 18-19. Dallas, Texas: Society of Petroleum Engineers Cite error: Invalid <ref> tag; name "r2" defined multiple times with different content
  3. ↑ Elam, F.M. 1957. Prediction of Bubble Point Pressures and Formation Volume Factors from Field Data. MS thesis, University of Texas at Austin, Austin, Texas.
  4. ↑ Vazquez, M.E. 1976. Correlations for Fluid Physical Property Prediction. MS thesis, University of Tulsa, Tulsa, Oklahoma.
  5. ↑ Vazquez, M. and Beggs, H.D. 1980. Correlations for Fluid Physical Property Prediction. J Pet Technol 32 (6): 968-970. SPE-6719-PA. http://dx.doi.org/10.2118/6719-PA
  6. ↑ 6.0 6.1 Glasø, Ø. 1980. Generalized Pressure-Volume-Temperature Correlations. J Pet Technol 32 (5): 785-795. SPE-8016-PA. http://dx.doi.org/10.2118/8016-PA
  7. ↑ Labedi, R.M. 1982. PVT Correlations of the African Crudes. PhD thesis. 1982. . PhD thesis, Colorado School of Mines, Leadville, Colorado (May 1982).
  8. ↑ Labedi, R.M. 1990. Use of Production Data to Estimate the Saturation Pressure, Solution Gor, and Chemical Composition of Reservoir Fluids. Presented at the SPE Latin America Petroleum Engineering Conference, Rio de Janeiro, Brazil, 14-19 October. SPE-21164-MS. http://dx.doi.org/10.2118/21164-MS
  9. ↑ Owolabi, O.O. 1984. Reservoir Fluid Properties of Alaskan Crudes. MS thesis, University of Alaska, Fairbanks, Alaska (May 1984).
  10. ↑ Al-Marhoun, M.A. 1985. Pressure-Volume-Temperature Correlations for Saudi Crude Oils. Presented at the SPE Middle East Oil Technical Conference and Exhibition, Bahrain, 11–14 March. SPE-13718-MS.
  11. ↑ Obomanu, D.A. and Okpobiri, G.A. 1987. Correlating the PVT Properties of Nigerian Crudes. J. Energy Resour. Technol. 109 (4): 214-217. http://dx.doi.org/10.1115/1.3231349
  12. ↑ Al-Marhoun, M.A. 1988. PVT Correlations for Middle East Crude Oils. J Pet Technol 40 (5): 650–666. SPE-13718-PA. http://dx.doi.org/10.2118/13718-PA
  13. ↑ Asgarpour, S., McLauchlin, L.L., Wong, D. et al. 1989. Pressure-Volume-Temperature Correlations For Western Canadian Gases And Oils. J Can Pet Technol 28 (4): 103. PETSOC-89-04-08. http://dx.doi.org/10.2118/89-04-08
  14. ↑ Al-Najjar, H.S., Al-Soof, N.B.A., and Al-Khalisy, K.M. 1988. Correlations For Bubble-Point Pressures, Gas Oil Ratios And Formation Volume Factors For Iraqi Crude Oils. Journal of Petroleum Research (June 1988): 13.
  15. ↑ Ahmed, T. 1989. Hydrocarbon Phase Behavior, Vol. 7. Tulsa, Oklahoma: Contributions in Petroleum Geology and Engineering, Gulf Publishing Company.
  16. ↑ Abdul-Majeed, G.H., Salman, N.H., and Scarth, B.R. 1988. An Empirical Correlation For Oil FVF (Formation Volume Factor) Prediction. J Can Pet Technol 27 (6): 118. PETSOC-88-06-10. http://dx.doi.org/10.2118/88-06-10
  17. ↑ Dokla, M.E. and Osman, M.E. 1992. Correlation of PVT Properties For UAE (United Arab Emirates) Crudes. SPE Form Eval (March 1992): 41.
  18. ↑ Petrosky, G.E. Jr. 1990. PVT Correlations for Gulf of Mexico Crude Oils. MS thesis. 1990. . MS thesis, University of Southwestern Louisiana, Lafayette, Louisiana.
  19. ↑ Petrosky, G.E. Jr. and Farshad, F. 1998. Pressure-Volume-Temperature Correlations for Gulf of Mexico Crude Oils. SPE Res Eval & Eng 1 (5): 416-420. SPE-51395-PA. http://dx.doi.org/10.2118/51395-PA
  20. ↑ 20.0 20.1 Kartoatmodjo, R.S.T. 1990. New Correlations for Estimating Hydrocarbon Liquid Properties. MS thesis, University of Tulsa, Tulsa, Oklahoma.
  21. ↑ 21.0 21.1 Kartoatmodjo, T.R.S. and Schmidt, Z. 1991. New Correlations for Crude Oil Physical Properties, Society of Petroleum Engineers, unsolicited paper 23556-MS.
  22. ↑ 22.0 22.1 Kartoatmodjo, T. and Z., S. 1994. Large Data Bank Improves Crude Physical Property Correlations. Oil Gas J. 92 (27): 51–55.
  23. ↑ 23.0 23.1 Al-Marhoun, M.A. 1992. New Correlations For Formation Volume Factors Of Oil And Gas Mixtures. J Can Pet Technol 31 (3): 22. PETSOC-92-03-02. http://dx.doi.org/10.2118/92-03-02
  24. ↑ 24.0 24.1 Frashad, F., LeBlanc, J.L., Garber, J.D. et al. 1996. Empirical PVT Correlations For Colombian Crude Oils. Presented at the SPE Latin American and Caribbean Petroleum Engineering Conference, Port of Spain, Trinidad and Tobago, 23–26 April. SPE-36105-MS. http://dx.doi.org/10.2118/36105-MS
  25. ↑ Macary, S.M. and El-Batanoney, M.H. 1992. Derivation of PVT Correlations for the Gulf of Suez Crude Oils. Proc., 11th EGPC Petroleum Exploration and Production Conference, Cairo, Egypt, Vol. 1, 374.
  26. ↑ Omar, M.I. and Todd, A.C. 1993. Development of New Modified Black Oil Correlations for Malaysian Crudes. Presented at the SPE Asia Pacific Oil and Gas Conference, Singapore, 8-10 February. SPE-25338-MS. http://dx.doi.org/10.2118/25338-MS
  27. ↑ Omar, M.I., Daud, M.E., and Raja, D.M.A. 1993. New Correlation For Determining Bubble Point Oil FVF (Formation Volume Factor). Presented at the 1993 Asian Council Petroleum Conference, Bangkok, Thailand, 2–6 November.
  28. ↑ Almehaideb, R.A. 1997. Improved PVT Correlations for UAE Crude Oils. Presented at the Middle East Oil Show and Conference, Bahrain, 15-18 March. SPE-37691-MS. http://dx.doi.org/10.2118/37691-MS
  29. ↑ Elsharkawy, A.M. and Alikhan, A.A. 1997. Correlations for predicting solution gas/oil ratio, oil formation volume factor, and undersaturated oil compressibility. J. Pet. Sci. Eng. 17 (3–4): 291-302. http://dx.doi.org/10.1016/S0920-4105(96)00075-7
  30. ↑ Khairy, M., El-Tayeb, S., and Hamdallah, M. 1998. PVT Correlations Developed for Egyptian Crudes. Oil Gas J. 96 (18): 114.
  31. ↑ 31.0 31.1 31.2 Al-Shammasi, A.A. 2001. A Review of Bubblepoint Pressure and Oil Formation Volume Factor Correlations. SPE Res Eval & Eng 4 (2): 146-160. SPE-71302-PA. http://dx.doi.org/10.2118/71302-PA
  32. ↑ Levitan, L.L. and Murtha, M. 1999. New Correlations Estimate Pb, FVF. Oil Gas J. 97 (10): 70.
  33. ↑ Velarde, J., Blasingame, T.A., and McCain Jr., W.D. 1997. Correlation of Black Oil Properties At Pressures Below Bubble Point Pressure - A New Approach. Presented at the Annual Technical Meeting of CIM, Calgary, Alberta, 8–11 June. PETSOC-97-93. http://dx.doi.org/10.2118/97-93
  34. ↑ Dindoruk, B. and Christman, P.G. 2001. PVT Properties and Viscosity Correlations for Gulf of Mexico Oils. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-3 October. SPE-71633-MS. http://dx.doi.org/10.2118/71633-MS
  35. ↑ Elsharkawy, A.M., Elgibaly, A.A., and Alikhan, A.A. 1995. Assessment of the PVT correlations for predicting the properties of Kuwaiti crude oils. J. Pet. Sci. Eng. 13 (3–4): 219-232. http://dx.doi.org/10.1016/0920-4105(95)00012-7
  36. ↑ Mahmood, M.A. and Al-Marhoun, M.A. 1996. Evaluation of empirically derived PVT properties for Pakistani crude oils. J. Pet. Sci. Eng. 16 (4): 275-290. http://dx.doi.org/10.1016/S0920-4105(96)00042-3
  37. ↑ Robertson, C.J. 1983. Comparison of Revised PVT Properties with Published Correlations. Internal Report, Marathon Oil Company, Houston, Texas (April 1983).
  38. ↑ Al-Fattah, S.M. and Al-Marhoun, M.A. 1994. Evaluation of empirical correlations for bubblepoint oil formation volume factor. J. Pet. Sci. Eng. 11 (4): 341-350.
  39. ↑ GeoMark Research. 2003. RFDbase (Reservoir Fluid Database), http://www.RFDbase.com.

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See also

Oil fluid properties

Oil density

Gas formation volume factor and density

PEH:Oil_System_Correlations

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