Abstract

In order to improve working performance of the section mill in U-shaped wells of coalbed methane (CBM), a numerical simulation model of section mill with single knife was established to study working process and mechanism of the section mill. Then a section mill of DXQ-512" was tested in a field CBM well named SX-T-02 in Qinshui Basin of China to verify the simulation results. Besides, the working process of the section mill, as well as the chip topography and formation mechanism was analyzed in simulation and field tests. Also, the influence of different working parameters on working performance of the section mill was carried out and an evaluation chart to choose recommended working parameters was established. Analysis results indicate that the error between simulation and field test result is within 11.9%, which verifies the fine accuracy of the numerical simulation model. Both the chips in simulation and field tests are curled chips, and when the rotating speed grows, the chip becomes smooth and the radius of curvature increases considerably. The working performance of the section mill is comprehensively determined by the working parameters including rotation speed and weight on bit (WOB). When it is necessary to balance the relationship between working efficiency and safety, rotating speed of 80 r/min and WOB of 12 kN are recommended. These studies are significant for satisfying the higher requirements on the working performance of the section mill for the development of CBM U-shaped wells in the field.

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