Analysis Of Frictional Resistance Of Drilling And Grinding Bridge Plug And Calculation Of Hydraulic Parameter For Coiled Tubing

In recent years, with the increase in the transformation of conventional and unconventional reservoirs reservoir development needs, coiled tubing horizontal well fracturing technology has been developing rapidly. However, due to the small particle size of coiled tubing, low bending stiffness, light weight and other factors, there will be a lot of negative factors in underground operations, one is that the depth and pressure of the coiled tubing are limited, which is especially significantly lower than conventional tubing string s in the horizontal section; and the other is that the displacement and the pressure drop of the coiled tubing conveying medium are limited, which makes it difficult to carry out the operation with large displacement.For this purpose, this paper mainly studies into the running-in, drilling and grinding conditions of coiled tubing for integration process technology of perforating, fracturing and drilling plug for coiled tubing. The calculation formula of pipe flow and annular flow pressure drop under the structure and space shape of coiled tubing and downhole tools are considered. The calculation formula of the pressure drop between the tube and the annular space is analyzed, and the existing formulas are verified and modified by numerical simulation and field experimental data, the calculation formula of pipe flow and annular flow pressure drop under different structure and space form is obtained, which provides a more complete and reliable calculation formula for the calculation of pressure drop in the downhole operation of coiled tubing. Based on the mechanical model of coiled tubing, the mechanical model of drilling and grinding bridge is established, and the calculation formulas of frictional resistance, fluid frictional resistance, local mechanical resistance and force in the tube and annulus adjustable are considered. Based on the force model and calculation method of coiled tubing, the mechanical analysis software of coiled tubing is developed. By analyzing the influencing factors of the depth of the limit of the coiled tubing, the limit depth of the coiled tubing under typical operating conditions is obtained.Through the comparison of 3 groups of experimental data and theoretical formula calculation, the error of 29 sets of experimental data is less than 5%, which shows the correctness of the model and the software. By calculating the typical working conditions of the coiled tubing at different velocities, different discharge and different WOB, the maximum depth of the coiled tubing under different conditions can reach 5200 m, with the horizontal segment length being 3700 m, and the minimum is 1675 m, with the horizontal segment length being 175 m, which provides a theoretical basis and guidance for the field construction.