The analysis of production data in unconventional reservoirs to determine well/reservoir properties, completion effectiveness, and estimate future production has become popular in recent years. However, production analysis in unconventional reservoirs is a challenging task because of the non-uniqueness associated with estimating well/reservoir properties. Various analysis methodologies exist in the literature, but no single methodology is robust enough to characterize the production data and forecast production. Therefore, from a conceptual standpoint, we believe that production analysis in unconventional reservoirs should not be a "single-method based" application. Instead, multiple analysis techniques combined with diagnostic tools have to be utilized, and challenges associated with the analysis have to be recognized.
This work attempts to provide a review of the existing production analysis and diagnostic techniques as well as to identify the challenges associated with production analysis in unconventional reservoirs. We present an extensive evaluation of the diagnostic tools for assessing data viability, checking data correlation along with flow regime identification. Based on diagnostics and analysis results, we demonstrate the use of forward modeling (simulation) to predict future performance of single/multiple well(s) for various production/completion and field development scenarios. Field examples from a wide range of unconventional reservoirs are used to describe the application of the methodology.