Patent ID: 8875785

Claim:
A method of correcting a downhole speed of a tool string moving in a wellbore, said method comprising: (a) inserting a tool string into a proximal upper end of the wellbore, said tool string comprising: a cable head connected at a first end to a cable; a casing collar locator; an accelerometer; at least one downhole tool selected from the group consisting of a logging tool and a perforating tool; (b) spooling out cable at the surface allowing the tool string to move into the wellbore; (c) obtaining data with an accelerometer and providing said data to a processor that calculates the downhole speed of the tool string based on the data from the accelerometer; (d) moving the tool string past at least two casing collars and sending data to the processor including the depth of each of the collars and time that the casing collar locator passes each of the casing collars; (e) calculating by the processor an average tool speed over the interval between collars; and (f) comparing the downhole speed of the tool string as calculated by the processor using the data from the accelerometer to the average tool speed calculated by the processor based on the time and casing collars.