Optimization Design and Field Application of Anti-Ballast Stabilizer in Extra-Deep Well

The ultra-large borehole drilling fluid has low return rate, weak rock carrying capacity, and serious repeated crushing. The conventional stabilizer is easy to block the returning cuttings and cause them to sink, resulting in poor cuttings flowback and high potential sticking risk. In order to solve these problems, by optimizing the shape and size of the diversion surface of the conventional stabilizer, adjusting the torsion angle of the spiral edge, changing the radius of the spiral flow channel and other improvement measures, an improved stabilizer suitable for the mud bag of ultra-deep wells was formed. Based on the discrete phase model ( DPM ), the fluid-solid coupling simulation and indoor scaling test were carried out to study the influence of the inlet and outlet diversion surface of the stabilizer, the torsion angle of the spiral edge and the radius of the spiral flow channel on the rock carrying capacity. The research results show that for the ϕ444.5 mm borehole, when the optimal torsion angle of the stabilizer spiral edge is 90°, the high-efficiency diversion effect can be achieved while ensuring the wall shear stress of the spiral edge is small, and the residual concentration of cuttings can be reduced. When the radius of the optimal spiral flow channel of the stabilizer spiral edge is 230 mm, the drilling fluid can increase the speed of the outlet section and reduce the residual concentration of cuttings while ensuring the high speed of the drilling fluid in the stabilizer acceleration section. Compared with the conventional stabilizer, the cuttings reflectivity of the improved stabilizer is reduced by 55.7%, and the cuttings carrying capacity is increased by 15.15%. In the drilling of SDCK−1 well in Wanmike exploration well in Sichuan Basin, the improved stabilizer ( spiral edge torsion angle 90° ) was applied, which effectively reduced the phenomenon of mud bag. The research results can provide reference for the design of drilling stabilizer in ultra-deep wells, which is helpful to improve drilling efficiency and reduce the risk of sticking.