Evaluation of Fracture Asymmetry of Finite-Conductivity Fractured Wells

Abstract

SummaryThis paper presents a graphical technique to evaluate asymmetry of hydraulically fractured wells. This technique is based on a new analytical solution for the pressure behavior of a finite-conductivity, asymmetrically fractured well during the pseudolinear flow period and the known bilinear flow solution. A semianalytical solution for transient flow toward finite-conductivity, asymmetrically fractured wells producing at constant rate is also presented. This solution was used with the analytical solution to analyze the pseudolinear flow pressure behavior.An expression relating dimensionless fracture conductivity, CfD, and asymmetry factor, a, with a parameter calculated from analysis of well-test data, βa, was developed by combining the pseudolinear and bilinear flow solutions; a graph of a vs. βa with CfD as a parameter is then constructed. The parameters βa and CfD are calculated as follows: βa=0.309 mbf2/(bLfmLf) and CfD=2.944 mLfm/mbf2, with mbf as the slope of the bilinear Δp-vs.-t¼ straight line, mLf and bLf as the slope and intercept of the pseudolinear Δp-vs.-t½ straight line, respectively, and m as the slope of the semilog Δp-vs.-log t straight line obtained during the pseudoradial flow period. Correlations developed apply indistinctly to oil and gas wells. Published field data were reanalyzed with the technique presented here and asymmetry was detected.