Study on the performance of downhole axial cyclone with spiral fins for drainage and sand removal

Abstract

When dewatering and resurrecting natural gas-flooded wells, sand-out problems can pose a serious hazard to downhole tools. At present, the downhole cyclone has more research on the separation of large particles of 60–70 µm, which is a serious hazard, but there is little research on the separation of fine particles of 10 µm. To improve the separation efficiency of downhole fine sand particles, this paper designs a new type of axial cyclone, in which a spiral fin is installed at the axis of the cyclone to improve the strength of the cyclone inner cyclone flow through the spiral fin so that the fine particles involved in the inner cyclone flow are thrown back into the outer cyclone flow area. This paper combines theoretical analysis, experimental study, and numerical simulation to compare and analyze the fluid transport law and internal flow field characteristics in the new cyclone and the basic cyclone, and the results show that the separation efficiency of the new cyclone for 10 µm fine particles is significantly improved and the pressure drop is slightly increased. In this paper, we also optimized the structural parameters such as envelope diameter, pitch, and length of the spiral fins. The separation performance is optimal when the envelope diameter is 10 mm, pitch is 40 mm and length is 240 mm, and the separation efficiency of 10 µm fine particles can reach 65.1%, which is a year-on-year increase of 99.1% compared with the basic separator, and the pressure drop is 0.231 MPa, which is a year-on-year increase of 31.2%.