A New Forecasting Model of a Wellbore Wax Deposition Profile in a Offshore Well

To alleviate the negative effects of wellbore wax deposition in offshore oil and gas production,research on wax deposition in offshore oilfields were carried out and a new forecasting model for wellbore wax deposition profile was established.The new model was developed on the basis of the existing four wax deposition mechanisms with comprehensive consideration to molecule diffusion,shear dispersion,shear erosion and wax layer aging.By using field data,performances of the new model were compared with waxing patterns in the four existing models.Calculation accuracy of wellhead temperatures (WHT) and bottom-hole pressures (BHP) of the new model was verified by using the production data from offshore wells with wax deposition in the Bohai Oilfield.Test results showed that the new model has higher accuracy with a relative calculation error of 1.32% for WHT and 0.30% for BHP,respectively.Sensitivities of influencing factors such as producing time,flow rates,water cut and production GORs were analyzed in the new model,and it indicated that wax deposition thicknesses may increase with the extension of producing time and they are highly sensitive to flow rates and water cut,whereas impacts of productions GOR are relatively low.Research results showed that the new model can accurately forecast the deposition of wax in offshore ESP wells and may provide valuable guidance for wax control and removal.