Edward ML. Tobing


Extended wellbore storage can be mistakenly interpreted as a reservoir response in gas well testing with surface shut in. This interpretation usually results in false value for permeability, skin and reservoir size and shape. This paper investigates changing wellbore storage in pressure transient testing with surface shut-in in gas well. This study was prompted by the observation, that in gas wells, many of the buildup tests obtained with surface shut-in exhibited complex reservoir model behavior with relatively low skin. The results presented in this paper are based on well test simulation and field data from North Sumatera. This work demonstrates the effect changing wellbore storage on the pressure derivative curve. Knowledge of the expected pressure derivative shape, and duration, will improve the design of buildup tests that will allow enough time for the actual reservoir response to be observed. This will result in a reliable reservoir model and correct estimation of permeability and skin factor.


Changing Wellbore Storage, Gas Well Testing

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Earlougher, R.C. Jr., Kersh, K.M., and Ramey, H.J. Jr. : “Wellbore Effects in Injection Well Testing, “ JPT (Nov. 1973) 1244.

Van Everdingen, A.F. and Hurst, W. : “Application of the Laplace Transformation to Flow Problems in Reservoir,” Trans., AIME (1949) 186, 305.

Hegeman, P.S., Hallford, D.L., and Joseph, J.A.: “Well-Test Analysis With Changing Wellbore Storage”, SPE Formation Evaluation (September 1993), page 201-207.

Fair, W.B. Jr.:”Pressure Buildup Analysis With Wellbore Phase Redistribution”, SPEJ(April 1981) 259;Trans.,AIME 271.

Hasan, A.R., and Kabir, C.S : “Modeling Changing Storage During a Shut-in Test,” SPE Annual Conference in Washington, DC, October 4-7, 1992. 47 CHANGING WELLBORE STORAGE IN GAS WELL LEMIGAS SCIENTIFIC CONTRIBUTIONS EDWARD ML. TOBING VOL. 31. NO. 2, AUGUST 2008 : 40 - 48

Yitang, Z, and Fuming, Z.: “Well Test Analysis in The Case of Changing Wellbore Storage,” SPE 22424.

Fair, W.B. Jr.: “Generalized of Wellbore Effects in Pressure Transient Analysis”, SPE 24715 presented at the 67th SPE Annual Conference in Washington, DC, October 4-7, 1992.

Lee, W.J.: “Presure-Transient Test Design in Tight Formation”, Journal of Petroleum Technology, October 1987, page 1185.

Agarwal, R.G., Al-Hussainy, R. and Ramey, H.J. Jr.: “An Investigation of Wellbore Storage and Skin Effect in Unsteady Liquid Flow: I. Analytical Treatment”, SPEJ (September 1970) 279- 90; Trans., AIME, 249. ˇ


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