Abstract
The paradigm shift towards horizontal well drilling with multiple fracture stages to exploit unconventional plays has unsurprisingly resulted in a rapid growth of questions regarding the interpretation of the associated well performance signatures on log-log diagnostic and specialized analysis plots. Log-log diagnostic plots perhaps best illustrate the sequence of flow-regimes which may result from this completion type. However, the long-term behavior one should expect to see on a square-root-time plot from the sequence is seldom presented in the literature, in spite of the ubiquitous use of linear flow specialized plots for unconventional well performance analysis. This paper addresses frequently asked questions regarding the meaning of the commonly observed negative y-intercepts on these plots. Using multi-frac horizontal well analytical models, synthetic production data sets were generated to evaluate various hydraulic-fracture geometries. The resulting data signatures are presented on a dimensionless specialized plot to reveal the behavior of the early linear, transitional and (late) compound linear flow regimes. This study illustrates that negative intercepts are typically created from the transitional period following the first linear flow and quantifies both the magnitude and sign of the resulting intercept produced from compound linear flow based on various hydraulic fracture length and spacing combinations. Using a field example, this work also demonstrates that false interpretations of compound linear flow may arise due to the misinterpretation of the prolonged transitional flow period between the first and second linear flow regimes.
