Effect of Well Variables on the Performance of Chemical, Jet, and RCT Tubing Cutters

An analysis of 72 workover tubing cuts made was completed to determine the effect of well variables on the cutting performance of chemical, jet, and radial cutting torch (RCT) tubing cutters. Performance data indicated that cutting success was only 65, 50, and 77% for the chemical, jet, and RCT cutters, respectively. While it was found that some cutting failures could be attributed to specific causes, such as heavy paraffin in the well, improper detonation, low-pressure tool leaks, exceeding tool pressure limits, and improper tool gas ventilation, other failures did not have any apparent cause. Therefore, the data was analyzed against specific well variables to look for trends to determine other possible failure causes. The most significant results indicated that chemical cutter success in CaBr(2) completions fluids was significantly reduced. For comparison, cuts in bromide fluids accounted for 71% of the total number of failed cuts but only comprised 32% of the total attempted cuts. Based on this data, along with examining the chemical reaction between the acid in the chemical cutter, bromine trifluoride, and the other completion fluids, it is believed that the chemical cutter acid reacts more efficiently with bromide completion fluids, therefore, limiting the amount of acid available to sever the pipe. Additionally, it was concluded that placing the pipe in tension significantly increased cutting performance. No other significant correlations were found to other well variables.