Improved convolution analysis of late wellbore storage buildup data of gaswells

Conventional pressure buildup tests of gas wells with wellbore storage have long been recognized as providing somewhat inaccurate estimates of the res ervoir parameters. Also, the application of these tests to low permeability reservoirs is time consuming and impractical in some field practice. Moreo ver, these tests do not offer a straight forward method to determine of the rate-dependent skin factor of high-flow-rate wells. This paper presents an extension of the convolution methods to analyze late wellbore storage buildup data of high-flow-rate gas wells. In addition of possessing all the advantages of the convolution techniques, the proposed e xtension offers a simple method that permits a direct estimation of the for mation permeability, the mechanical and the rate-dependent skin factors, an d the extrapolated reservoir pressure from three different analysis plots. Two simulated cases and one field example are presented to demonstrate the effectiveness of the proposed technique in analyzing: high-flow-rate wells producing from low-permeability reservoirs.