Development of Coiled Tubing Jet Tools with Multi-Hole Nozzles and Cleaning Parameter Optimization

To solve the problem of poor cleaning effects caused by incorrect matching of coiled tubing (CT) sizes with nozzle jet parameters and pumper parameters, the influences of jet velocities, nozzle diameters, number of nozzles, movement velocities, and scale removers on tubing cleaning effects were studied through laboratory experiments by simulating the matching relationship among CTs, nozzle combinations, and hydraulic parameters of pumpers. Based on the analysis results, a new type of multi-hole jet cleaning tool was designed, and the parameters of which were optimized. The research shows that under the condition that the string is safe, and the space in the tubing is large, the CT with a large size can be selected to reduce the friction in the tubing and increase the flow return velocity. For the scale removing of ϕ73 mm tubing with the well depth of less than 3000 m, the optimal construction displacement can be obtained by selecting a ϕ50.8 mm CT,a pumper plunger diameter of 114.3 mm, a pump speed of 90 min⁻¹, and a power of 580 kW. For the scale removing of tubing in Qigequan Oilfield, clean water was mixed with hydrochloric acid of 5% and a scale remover of 1%, the jet scale removing tool was equipped with five ϕ3.5 mm nozzles. In that case, the construction displacement is 550–600 L/min, and the movement velocity is 5 m/min. The results shows a good scale removing effect. CT jet scale removing technology is safe, environmentally friendly, and pollution-free, it has a great prospect for broad application.