Conventional analysis for characterization of bi-radial (elliptical) flow in infinite-conductivity vertical fractured wells
Abstract
It is difficult to ignore a 0,36-slope line, bi-radial flow, which shows up in the pressure derivative plot of many well pressure tests conducted in hydraulically fractured vertical wells. Needless to say that interpretation of this flow regime as linear flow introduces errors in the estimation of the fracture parameters. Very few technical papers have dealt with the bi-radial or elliptical flow. Even though, none of the commercial well test interpretation packages name it, they can reproduce the typical pressure behavior in which elliptical flow is seen. For more than half a century, conventional techniques have been a very reputed and respected method for interpretation of well pressure tests. Therefore, it is necessary to add a new methodology to complement the conventional technique so that the bi-radial/elliptical flow can be characterized, and of course, its application leads to an appropriate evaluation and assessment of a fracture treatment. Therefore, this paper provides a new alternative which allows to obtain the slope of the cartesian plot of pressure vs. either t 0,36 (for drawdown) or ([ t p +?t ] /?t ) 0,36 (for buildup) from which the half-fracture length is readily estimated. The proposed technique was verified by the application of a field case and a simulated example.
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