Production State Identification of Offshore High-Water-Rate Gas Wells Based on Dynamic Pressure Profile Calibration and Nodal Analysis

Offshore high-water-rate gas wells can often sustain stable production for a considerable period after liquid first appears at the wellhead. Unlike conventional onshore gas wells with relatively low liquid production, these wells can remain in stable production during the middle and late production stages even when the gas velocity in the wellbore has fallen far below the critical value predicted by conventional liquid-carrying criteria. Under such conditions, the wellbore flow pattern commonly shifts from annular mist flow to churn flow and slug flow, and liquid transport becomes governed by a dynamic balance jointly controlled by pressure differential and gas entrainment. As a result, conventional critical liquid-carrying theory alone is no longer sufficient for accurate production state identification. To address this issue, this study proposes a production state identification method for offshore high-water-rate gas wells based on dynamic pressure profile calibration and nodal analysis. In this method, the wellbore pressure profile serves as the key link between outflow capacity and production state evaluation. Measured data from flowing pressure tests are used to calibrate the pressure profile within the selected multiphase flow correlation by introducing two calibration coefficients, namely the liquid holdup calibration coefficient and the two-phase friction calibration coefficient. Gaussian process regression is then applied to model the temporal evolution of the calibration coefficients, generate their fitted trajectories, and predict their values at the next time step. By using the predicted calibration coefficients to recalibrate the pressure profile, dynamic calibration of the wellbore pressure profile is achieved. Field applications to four offshore high-water-rate gas wells show that the calibrated pressure profiles are in closer agreement with the measured pressure points. The accuracy of production-state identification is also significantly improved, and the gas production rates calculated from calibrated nodal analysis are closer to the values reported in daily production records than those obtained before calibration. These results demonstrate that the proposed method effectively improves both wellbore pressure profile prediction and production-state identification for offshore high-water-rate gas wells. The study provides a practical method for production state evaluation and production management of offshore high-water-rate gas wells during the middle and late stages of field development.