Pressure Buildup Test Results From Horizontal Wells in the Pearsall Field of the Austin Chalk

Abstract

ABSTRACT This paper presents the results and representative data sets of pressure transient tests on horizontal wells in the Pearsall Field of the Austin Chalk. The data trends indicated possible early time radial flow, largely obscured by wellbore storage, followed by a strongly developed linear flow period. On tests of adequate length this is followed by a multiple porosity transition and a return to linear flow. The data was interpreted in terms of a pseudosteady state dual porosity flow model for the Austin Chalk. The fracture system permeability was estimated to be in the range of 0.5 to 10 md, the dual porosity storativity ratio was found to be between 0.1 and 0.01, while the interporosity flow coefficient had values near IE-07. The net thickness drained by the wells was determined to be between 100 and 400 ft, depending on the well tested. The abnormally large observed wellbore storage coefficients correlate with well productivity and are considered to be indicators of the fracture intensity.