Mechanical caliper system for a logging while drilling (LWD) borehole caliper

摘要

A logging while drilling (LWD) caliper includes a drill collar, at least one movable pad, a hinge coupler, a power transmitter and a power receiver. The hinge coupler couples the movable pad to the drill collar in such a way that the movable pad can move between an open position and a closed position. The power transmitter is coupled to the drill collar in such a way that the power transmitter receives power from the drill collar. The power receiver is coupled to the movable pad in such a way that the power receiver provides power to the movable pad. Also, the power transmitter is coupled to the drill collar and the power receiver is coupled to the movable pad is such a way that power is transmitted from the power transmitter to the power receiver.

主权项

1. A method comprising:
providing a first coil within a drill collar; providing a second coil in the moveable member; coupling the first and second coils with a coupling coefficient, k, wherein, k=M/√{square root over (L1L2)}≦0.9, M is a mutual inductance between the first and second coils, L1 is a first self-inductance of the first coil, and L2 is a second self-inductance of the second coil; and resonantly tuning the first coil at a first frequency, f1, with a first capacitance, C1, and the second coil at a second frequency, f2, with a second capacitance, C2, wherein f1 is approximately equal to f2,f1=12⁢π⁢L1⁢C1⁢⁢and⁢⁢f2=12⁢π⁢L2⁢C2; wherein the first and second coils have a figure of merit, U, whereinU=k⁢Q1⁢Q2≥3,Q1=2⁢π⁢⁢f1⁢L1R1,Q2=2⁢π⁢⁢f2⁢L2R2,  Q1 and Q2 comprise respective quality factors associated with the first and second coils, and R1 and R2 comprise respective resistances of the first and second coils.