Well plugs and associated systems and methods

1. A well plug for use in a subterranean well, the well plug comprising:

a tubular mandrel;

a seal element positioned on the tubular mandrel; and

a setting rod releasably secured relative to the tubular mandrel by an annular shaped shear ring having longitudinally-extending straight parallel sides within which the shear ring is configured to shear, in which an uppermost surface of the shear ring abuts a lowermost surface of the setting rod in an assembled configuration of the well plug, and in which the setting rod is configured to apply a compressive force to the tubular mandrel during setting of the well plug, the setting rod being releasable for longitudinal displacement relative to the tubular mandrel in response to a predetermined shear force applied to the shear ring.

2. The well plug of claim 1 , in which the shear ring is positioned longitudinally between a first annular shoulder that displaces with the setting rod, and a second annular shoulder that displaces with the tubular mandrel.

3. The well plug of claim 2 , in which the first annular shoulder is formed on a fastener that secures the shear ring to the setting rod.

4. The well plug of claim 2 , in which the second annular shoulder is formed in the tubular mandrel.

5. The well plug of claim 1 , in which the seal element is positioned between first and second structures, the seal element being outwardly extendable in response to a decrease in a longitudinal distance between the first and second structures.

6. The well plug of claim 5 , in which the first structure displaces with the tubular mandrel.

7. The well plug of claim 1 , in which the predetermined shear force is transmitted from the setting rod to the tubular mandrel via the shear ring.

8. The well plug of claim 1 , in which the shear ring is received in a counterbore in a lowermost end of the tubular mandrel.

9. A method of setting a well plug in a subterranean well, the method comprising:

displacing a tubular mandrel with a setting rod relative to an outer housing of the well plug, in which a compressive force is applied to the tubular mandrel by the setting rod during the displacing;

outwardly extending a seal element of the well plug in response to the displacing; and

shearing a releasable attachment securing the setting rod relative to the tubular mandrel, the releasable attachment comprising an annular shaped shear ring having longitudinally-extending straight parallel sides within which the shear ring is configured to shear, in which an uppermost surface of the shear ring abuts a lowermost surface of the setting rod, and

in which the releasable attachment is positioned proximate a lowermost end of the tubular mandrel.

10. The method of claim 9 , in which the shearing comprises shearing the shear ring between annular shaped shoulders.

11. The method of claim 10 , in which the shearing further comprises releasing the setting rod for displacement relative to the tubular mandrel in response to a predetermined shear force being applied to the shear ring.

12. The method of claim 10 , in which one of the annular shoulders displaces with the setting rod, and another annular shoulder displaces with the tubular mandrel.

13. The method of claim 9 , in which the releasable attachment is received in a counterbore in the lowermost end of the tubular mandrel.