Wellbore depth instrument

A method for determining well depth measurements along a wellbore comprising:

• (A) mounting a wellbore depth instrument onto a tool-string designed for downhole operations, wherein the wellbore depth instrument comprises:
• an upper and lower tool mount body, each comprising a laterally extending cylindrical bore that allows the upper and lower tool bodies to mount onto a tool-string;
• a pair of side rails, each comprising an upper portion, a lower portion, and a center portion, wherein the upper portion of each of the pair of side rails is coupled to the upper tool mount body on opposing sides, wherein the lower portion of each of the pair of side rails is coupled to the lower tool mount body on opposing sides, wherein the center portion provides separation between the upper and lower tool mount bodies, and wherein the coupling of the pair of side rails to the upper and lower bodies form a combined upper/lower tool mount body;
• a pair of wheel suspension assemblies coupled to the combined upper/lower tool mount body on opposing sides, each comprising:
• a wheel assembly comprising a traction wheel and an electronics package;
• an upper and lower biasing element;
• and
• an upper and lower Scott Russel linkage, wherein the upper Scott Russel linkage couples the wheel assembly to the upper tool mount body and the upper biasing element, and wherein the lower Scott Russel linkage couples the wheel assembly to the lower tool mount body and the lower biasing element, and
• wherein the upper and lower biasing elements of the pair of wheel suspension assemblies bias the upper and lower Scott Russel linkages of the pair of wheel suspension assemblies in an axially inward direction, thereby biasing the traction wheels of the pair of wheel suspension assemblies in a downward direction perpendicular to the axial inward direction, wherein the biasing of the traction wheels allows the tractions wheels to remain in contact with a wall of the wellbore through upward and downward movement during a downhole operations run;
• (B) running the tool-string up or down the wellbore, thereby causing rotation of the traction wheels;
• (C) allowing the electronics packages to record in memory rotations of their respective traction wheels and frequencies of the rotations;
• and
• (D) determining well depth measurements along the wellbore via the recorded rotations of the traction wheels and frequencies of the rotations.