Patent ID: 8919457
Filing Date: 2014-12-30
Classification: E21B

Abstract:
1. In a drill string to which a drill bit is attached for drilling a bore hole in an earthen formation, a method for determining the weight applied to said drill bit, comprising the steps of: sensing the relative displacement between a first component coupled to said drill bit and a second component in coaxial relationship with the first component, the first component configured to move axially in response to an axial motion of said drill bit, the first and second components containing a fluid there between, wherein the axial motion of said drill bit causes relative axial motion between said first and second components, so as to cause the relative displacement; generating a signal representative of said sensed relative displacement; causing a deflection of a spring, the spring operably connected to at least one of the first and second components, the spring configured to oppose said relative axial motion between said first and second components and generate a force in response to the deflection, the spring having a predetermined relationship between the deflection of said spring and the force generated by said spring when subject to the deflection; determining the value of the force based on said signal representative of said sensed relative displacement and said predetermined relationship of the spring; determining the value of the viscosity of the fluid; determining the weight on said drill bit based upon the value of the force and the viscosity of the fluid.