Development and Field Application of Controllable Reamer While Drilling

As unconventional oil and gas exploration and development in my country deepens, problems such as the narrow safety window of drilling fluid and necking of wellbore in salt-gypsum layers have put forward higher requirements for drilling and cementing operations. In response to the above problems, a controllable hole expander was designed based on the hydraulic control principle to expand the wellbore size, realize unconventional wellbore structure, inhibit wellbore necking, and improve cementing quality. In order to modularize the tool, its main parts are divided into a control mechanism and a transmission mechanism. The internal liquid flow field of the tool under different states was constructed with the help of numerical simulation software. The numerical simulation analyzed the pressure loss difference of the tool in the unactivated state, activated state and activated state when the inlet displacement was 32 L/s and the fluid density was 2.0 g/cm3. The feasibility was verified by indoor tests and field applications. The results show that the starting stress of the tool is 2 MPa, the starting displacement is 20 L/s, and the stress of the blade fully expanded is 4.5 MPa. After throwing one ball, the pin sheared at a pressure of 6 MPa. After the tool was deactivated by throwing two balls, it could be recovered normally despite the configuration of the spring blade with lower stiffness. The average wellbore diameter of the test well section was 268.18 mm, which was 36.58 mm larger than the average wellbore diameter before the expansion eye, with an expansion rate of 15.8%. The tool effectively alleviated the problems of electrical measurement resistance and hanging caused by formation necking, and provided product and technical support for solving the necking of salt-gypsum layers and unconventional casing operations.