Multiphase Pressure Transient Analysis – Agbami Case Study

Abstract Production performance of well assets changes as oil and gas assets mature leading to increased breakthrough of associated fluids (gas and/or water). Classic single-phase Pressure Transient Analysis (PTA) becomes limited with multiphase flow due to the underlying principles governing single phase flow resulting in errorneous interpretation results. This paper presents the outcome of PTA interpetaion results for oil production wells that recently experienced water breakthrough to assess the value of performing post-breakthrough multiphase pressure transient analysis. Using field data, the results obtained from single-phase pressure transient analyses on buildups after breakthrough were inconsistent with results obtained prior to breakthrough. Multiphase pressure transient analyses were performed on the same post-breakthrough buildup data and the results were compared with the historical well and reservoir behaviors when the well was still in single phase and single-phase pressure transient was conducted. The results indicated excellent agreement in terms of well and reservoir properties between the buildups obtained during two-phase flow and those obtained during single phase flow when multiphase pressure transient analyses were performed on the buildups during two-phase flow. The study also compared two multiphase pressure transient analysis methodologies: Perrine (1956) and Kamal-Pan (2010). Using field data, the results obtained from these two methodologies were observed to be consistent. A key lesson learned during this study was the importance of the relative permeability data on the results of multiphase pressure transient analysis.