A model of calculating the circulating pressure loss in coiled tubing ultra-short radius radial drilling

By analyzing the relationship between measured values of pressure loss in a high-pressure hose and calculated values of metal tubing pressure loss formula under the same condition, a calculation formula of pressure loss in a high-pressure hose is revised on the basis of the existing formula, and a model of calculating the circulating pressure loss in coiled tubing ultra-short radius radial drilling is established by theoretical derivation. The effects of tubing diameter, tubing length, pump delivery and fluid dynamic viscosity on each part of pressure loss in circulation system are studied by the pressure loss calculating model. The pressure loss in coiled and straight parts of 0.025 4 m (1 in) coiled tubing is about 8-10 times bigger than the pressure loss of 0.038 1 m (1.5 in) coiled tubing, and the pressure loss in high-pressure hose accounts for a large proportion in circulation system, about 86% in this study; and with drag reducer added in clear water, the pressure loss is about half of clear water pressure loss under the same condition.