Analysis of bit balling and application of the balling-preventing drilling fluid in well Songke-2

In order to solve the problem of the high mud content and easy hydration and dispersion of the Cretaceous sedimentary strata in well Songke-2, the bit balling is prone to occur in the water-based drilling fluid environment, which affects the drill bit ROP and induces downhole adhesion stuck, the paper combined the core drilling technology of well Songke-2, systematically analyzed of the causes of bit balling generated by the drill bit in the mudstone and water-based drilling fluid environment, provided a basis for the design of the anti-balling of the drill bit and the formulation of the anti-ball in drilling fluid, and proposed a drilling fluid formulation with excellent anti-balling performance. The results show that the mudstone drilled in well Songke-2 had the characteristics of high shale content and easy hydration and viscosity, it is very easy to induce the bit balling caused by the adhesion of cuttings and the mechanical “inlaying” of cuttings. Mechanical adhesion of drill bit and drill structure size, bottom hole hydraulic condition, bit material and surface condition, drilling procedure parameters and drilling fluid performance indicators are closely related. Adjusting the performance of the drilling fluid is an effective way to solve the bit balling problem at the drilling site. According to the technical characteristics of the high-temperature and high-pressure sections in the fourth opening of the well Songke-2,after repeated matching, the drilling fluid composition with excellent high temperature resistance and anti-adhesion performance was obtained. The test results of high temperature inhibition, water loss wall-building and the lubricity show that this drilling fluid has strong inhibition at high temperature(230℃), little water loss and good lubricity, it can solve the bit balling problem of the well Songke-2, effectively avoid the instability of the ROP and the occurrence of sticking stuck, the field application effect is ideal.