Establishment and application of paraffin removal cycle prediction chart in offshore highly waxy oil fields

Some highly waxy oil wells in Bohai Sea were facing serious well paraffin deposition after putting into operation. Field workers used to determine paraffin removal cycles based on production experience, which led to low accuracy and limited success rate of paraffin removal operation. According to the characteristics of offshore oil well production strings and based on Ramey temperature field calculation mathematical model and wax deposition profile calculated by well wax deposition rate model, a prediction method for wax removal cycle of ESP wells is deduced and established, and a prediction chart for wax removal cycle and wax removal depth of block A in an oilfield is further drawn. The results show that the wax removal cycle decreases in power function form with the decrease of liquid yield and increases in exponential function form with the increase of water content. According to the prediction chart of wax removal cycle, the predicted wax removal cycles of three wells are 11 d, 15 d and 46 d respectively, and the actual wax removal cycles are 8 d, 12 d and 39 d respectively. The predicted results are basically consistent with the actual ones. This method can also be used to quickly and accurately determine the period and depth of paraffin removal in gushers in land oilfields. It has important guiding significance for timely formulation of paraffin removal and prevention measures in highly wax ESP wells and gushers.