Apparatus for remote adjustment of drill string centering to prevent damage to wellhead

摘要

A drill bit guide is mounted in a wellhead in place of a wear bushing. The bit guide is capable of guiding strings and tools through the wellhead without damage to the wellhead or string while drilling. In one version of the bit guide, a pair of linear actuators radially extend and retract separate halves of the bit guide to conform to the size of the object located between them. In another version of the bit guide, a set of interlocking arms and wear bars are articulated to form a circular opening having a variable inner diameter. A drill string may be lowered through a fully open bit guide or landed on top of a filly closed bit guide. The bit guide also can be moved to more closely receive the drill string passing through it to prevent damage to the drill string and the wellhead.