New Rate-Transient Analysis for Fractured Shale Gas Wells Using a Tri-linear Flow Model

Fractured shale gas wells often exhibit long-term linear flow. Previous studies have developed some linear flow models to analyse this behaviour. In this study, we developed a tri-linear flow model for simulating shale gas production. Our model does not assume that the length of secondary fractures is equal to the half-distance between adjacent hydraulic fractures, which is an improvement over previous tri-linear flow models. Based on the tri-linear flow model, we developed simplified equations for characterizing bilinear and linear flow regimes. Combining the tri-linear flow model and simplified equations, we developed a new rate-transient analysis (RTA) workflow to analyse shale gas production data. The new RTA workflow not only includes the identification of flow regimes and their analysis using a log-log plot of the reciprocal of production rate versus time, i.e., straight line analysis, but also history-matching. The results obtained from straight line analysis serve as additional constraints in history-matching. This helps to reduce the non-uniqueness issue of history-matching. The new RTA workflow was validated using two synthetic and five field examples.