Interpretation of pressure tests in hydraulically fractured wells in bi-zonal gas reservoirs

Due to the recent increase in the fracturing of low permeability formations, mathematical wellbore data interpretation has become important to generate mathematical models to study their pressure behavior and formulate interpretation methodologies for a more accurate characterization of tight hydrocarbon-bearing formations. This paper presents an analytical methodology of interpretation using the pseudopressure and pseudopressure derivative log-log plot for the characterization of hydraulically fractured (partially or fully penetrating) vertical wells completed in bi-zonal gas reservoirs. The methodology provided uses characteristic points and lines found on the pseudopressure and pseudopressure derivative plot so that new analytical expressions and correlations are developed to estimate half-fracture length, fracture penetration ratio, mobility and storativity ratios, radial permeability, size of the inner zone, well drainage area, vertical permeability and skin factor. The new expressions were successfully verified and tested with synthetic examples.