Guidelines for the Proper Application of Critical Velocity Calculations
- Robert P. Sutton (Marathon Oil Company) | Stuart A. Cox (Marathon Oil Company) | James F. Lea (PLTech LLC) | O. Lynn Rowlan (Echometer Company)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- May 2010
- Document Type
- Journal Paper
- 182 - 194
- 2010. Society of Petroleum Engineers
- 3.1 Artificial Lift Systems, 4.1.5 Processing Equipment, 2.3.4 Real-time Optimization, 2.2.2 Perforating, 4.1.2 Separation and Treating, 5.2.1 Phase Behavior and PVT Measurements, 3 Production and Well Operations, 5.9.2 Geothermal Resources, 3.1.8 Gas Well Deliquification, 5.3.2 Multiphase Flow, 5.2 Reservoir Fluid Dynamics, 4.6 Natural Gas
- Production and Operations
- 12 in the last 30 days
- 1,707 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 5.00|
|SPE Non-Member Price:||USD 35.00|
Critical velocity calculations in the form of charts or simple equations are frequently used by field personnel to evaluate a gas well's flowing conditions to determine if the well is experiencing liquid-loading problems. Literature detailing the critical velocity necessary to keep a gas well unloaded suggests using the conditions at the top of the well as an evaluation point. This is convenient for personnel conducting the evaluation because wellhead pressure and temperature data are readily available. A number of situations exist where the use of the wellhead as the evaluation point can lead to erroneous conclusions. The most obvious situation occurs with a change in geometry downhole when a tapered tubing string is run in a well or when the tubing is set above the perforations. In these instances a more robust evaluation results from using conditions at the bottom of the well and the downhole tubing geometry. Other conditions exist where the use of downhole conditions provides a better evaluation point. The assumptions used in the development of the standard, simplified form of the critical velocity equations and charts may not be appropriate for downhole application. In these cases, the fundamental equations must be used. The calculation of critical velocity requires knowledge of pressure, temperature, produced fluids, and pressure/volume/temperature (PVT) properties. The determination of critical rate requires the same properties with the addition of pipe diameter. The required PVT properties, including surface tension and density for both the gas and liquid phases, are reviewed. Correlations to calculate water/gas surface tension were found to have excessive error, so a new, more accurate method is presented. This paper provides recommendations for the use of a surface or a downhole evaluation point is more appropriate for the determination of the minimum critical gas velocity in a well.
|File Size||1 MB||Number of Pages||13|
Abdul-Majeed, G.H. and Abu Al-Soof, N.B. 2000. Estimation of gas-oilsurface tension. J. Pet. Sci. Eng. 27 (3-4): 197-200.doi: 10.1016/S0920-4105(00)00058-9.
Belfroid, S.P.C., Schiferli, W., Alberts, G.J.N.m Veeken, C.A.M., andBiezen, E. 2008. Prediction Onsetand Dynamic Behaviour of Liquid Loading Gas Wells. Paper SPE 115567presented at the SPE Annual Technical Conference and Exhibition, Denver, 21-24September. doi: 10.2118/115567-MS.
Bukacek, R.F. 1955. Equilibrium Moisture Content of Natural Gases. ResearchBulletin 8, Institute of Gas Technology, Chicago, Illinois.
Coleman, S.B., Clay, H.B., McCurdy, D.G., and Norris, H.L. III. 1991a. A New Look at Predicting Gas-WellLoad-Up. J. Pet Tech 43 (3): 329-333; Trans.,AIME, 291. SPE-20280-PA. doi: 10.2118/20280-PA.
Coleman, S.B., Clay, H.B., McCurdy, D.G., and Norris, H.L. III. 1991b. Understanding Gas-Well Load-UpBehavior. J. Pet Tech 43 (3): 334-338; Trans.,AIME, 291. SPE-20281-PA. doi: 10.2118/20281-PA.
Coleman, S.B., Clay, H.B., McCurdy, D.G., and Norris, H.L. III. 1991c. The Blowdown-Limit Model. J.Pet Tech 43 (3): 339-343; Trans., AIME, 291.SPE-20282-PA. doi: 10.2118/20282-PA.
Coleman, S.B., Clay, H.B., McCurdy, D.G., and Norris, H.L. III. 1991d. Applying Gas-Well Load-UpTechnology. J. Pet Tech 43 (3): 344-349; Trans.,AIME, 291. SPE-20283-PA. doi: 10.2118/20283-PA.
Danesh, A. 2001. PVT and Phase Behaviour of Petroleum ReservoirFluids, second impression, No. 47. Amsterdam, The Netherlands: Developmentsin Petroleum Science, Elsevier Science B.V.
Firoozabadi, A. and Ramey, H.J. Jr. 1988. Surface Tension ofWater-Hydrocarbon Systems at Reservoir Conditions. J. Cdn. Pet. Tech. 27 (May-June): 41-48.
Glasø, Ø. 1980. GeneralizedPressure-Volume-Temperature Correlations. J. Pet. Tech. 32 (5): 785-795. SPE-8016-PA. doi: 10.2118/8016-PA.
Gray, H.E. 1978. Vertical Flow Correlation--Gas Wells. In User Manual forAPI 14B Subsurface Controlled Safety Valve Sizing Computer Program, secondedition, Appendix B. Washington, DC: API.
Hinze, J.O. 1949. Criticalspeeds and sizes of liquid globules. Applied Scientific Research 1 (4): 273-288. doi:10.1007/BF02120335.
Hinze, J.O. 1955. Fundamentals of the hydrodynamicmechanism of splitting in dispersion processes. AICHE Journal 1 (3): 289-295. doi:10.1002/aic.690010303.
Katz, D.L. 1959. Handbook of Natural Gas Engineering, 127-129. NewYork: McGraw-Hill Higher Education.
McInerney, J., Lea, J., and Cox, J.C. 2004. Uncertainty in Gas Well CriticalVelocity Predictions. Paper presented at the 51st Southwest Petroleum ShortCourse, Lubbock, Texas, USA, 21-22 April.
Oudeman, P. 2007. On the FlowPerformance of Velocity Strings To Unload Wet Gas Wells. Paper SPE 104605presented at the SPE Middle East Oil and Gas Show, Bahrain, 11-14 March. doi:10.2118/104605-MS.
Perry, R.H., Green, D.W., and Maloney, J.O. 1997. Perry's ChemicalEngineers' Handbook, seventh edition, Chap. 6. New York: McGraw-Hill.
Rowe, A.M. Jr. and Chou, J.C.S. 1970. Pressure-volume-temperature-concentrationrelation of aqueous NaCl solutions. J. Chem. Eng. Data 15(1): 61-66. doi:10.1021/je60044a016.
Rowlan, O.L., McCoy, J.N., and Podio, A.L. 2006. Acoustic Liquid-Level Determinationof Liquid Loading in Gas Wells. Paper SPE 100663 presented at the SPEWestern Regional/AAPG Pacific Section/GSA Cordilleran Section Joint Meeting,Anchorage, 8-10 May. doi: 10.2118/100663-MS.
SMU Geothermal Lab. 2005. US Regional Heat Flow Database and Maps: ThermalGradient, http://smu.edu/geothermal/heatflow/heatflow.htm.
Standing, M.B. 1981. Volumetric and Phase Behavior of Oil Field HydrocarbonSystems. Richardson, Texas: Society of Petroleum Engineers of AIME.
Sutton, R.P. 2006. Oil System Correlations. In Petroleum EngineeringHandbook, Vol. 1--General Engineering, ed. J.R. Fanchi, 257-331.Richardson, Texas: Society of Petroleum Engineers.
Sutton, R.P. 2007. FundamentalPVT Calculations for Associated and Gas/Condensate Natural-Gas Systems.SPE Res Eval & Eng 10 (3): 270-284. SPE-97099-PA. doi:10.2118/97099-PA.
Sutton, R.P. 2009. An ImprovedModel for Water-Hydrocarbon Surface Tension at Reservoir Conditions. PaperSPE 124968 presented at the SPE Annual Technical Conference and Exhibition, NewOrleans, 4-7 October. doi: 10.2118/124968-MS.
Sutton, R.P., Cox, S.A., Williams, E.G. Jr., Stoltz, R.P., and Gilbert, J.V.2003. Gas Well Performance atSubcritical Rates. Paper SPE 80887 presented at the SPE Production andOperations Symposium, Oklahoma City, Oklahoma, USA, 23-25 March. doi:10.2118/80887-MS.
Turner, R.G. 1967. An Analysis of the Continuous Removal of Liquids From GasWells. MS thesis, University of Houston, Houston, Texas (August 1967).
Turner, R.G., Hubbard, M.G., and Dukler, A.E. 1969. Analysis and Prediction of MinimumFlowrate for the Continuous Removal of Liquids from Gas Wells. J. PetTech 21 (11): 1475-1482; Trans., AIME, 246.SPE-2198-PA. doi: 10.2118/2198-PA.
Veeken, K., Bakker, E., and Verbeek, P. 2003. Evaluating LiquidLoading--Field Data and Remedial Measures. Presented at the 2003 Gas WellDeliquification Workshop, Denver, 3-4 March.
Whitson, C. and Brulé, M. 2000. Phase Behavior. Monograph Series,SPE, Richardson, Texas 20.
Wichert, E. and Aziz, K. 1972. Calculate Z's for Sour Gases. HydrogenProcessing (May): 119-122.