Device for anchoring an oil well tubing string within an oil well casing

An anchoring device for anchoring an oil well tubing string within an oil well casing, the device comprising:

• (i) an anchor mandrel having attached thereto anchoring means for selectively engaging and disengaging the interior surface of an oil well casing;
• (ii) a drive mandrel, said drive mandrel having an upper end releasably securable to an oil well tubing string and a lower end releasably securable to said anchor mandrel;
• (iii) torque carrying means operatively connected between said anchor mandrel and said drive mandrel to assist in the transference of rotational movement and torque between said drive mandrel and said anchor mandrel;
• and,
• (iv) a shear member having an upper end, a lower end and a shear zone of reduced tensile strength located between said upper and said lower ends, said shear member assisting in releasably securing said drive mandrel to said anchor mandrel such that when said drive mandrel is secured to said anchor mandrel tensile load applied between said drive mandrel and said anchor mandrel in excess of the yielding strength of said shear zone causes breakage of said shear member along said shear zone and separation of said drive mandrel from said anchor mandrel.

A drive and shear mechanism for releasably connecting downhole tools to an oil well tubing string in an oil well, the drive and shear mechanism comprising:

• (i) a drive mandrel, said drive mandrel having an upper end releasably securable to an oil well tubing string and a lower end operatively connectable to a downhole tool;
• (ii) torque carrying means to assist in the transference of rotational movement and torque between said drive mandrel and the downhole tool;
• and,
• (iii) a shear member having an upper end, a lower end, and a shear zone of reduced tensile strength located between said upper and said lower ends, said shear member releasably securing said drive mandrel to a downhole tool such that when said drive mandrel is secured to a downhole tool a tensile load applied between said drive mandrel and the downhole tool in excess of the yielding strength of said shear zone of reduced tensile strength causes breakage of said shear member along said shear zone of reduced tensile strength and separation of said drive mandrel and the oil well tubing string from the downhole tool such that said drive mandrel and the oil well tubing string may be extracted from the oil well while the downhole tool and said lower end of said shear member remain within the well.