Patent ID: 9518447
Filing Date: 2016-12-13
CPC Classification: E21B

Claim Text:
1. A method for controlling a drilling or cutting operation performed by a wireline tool downhole, comprising the steps of: commencing a drilling or cutting operation in a downhole object, such as a casing or valve, detecting vibrations in a tool housing produced during the drilling or cutting operation in the downhole object using a vibration sensor being an accelerometer arranged on the tool housing, processing a vibration signal from the vibration sensor to produce a reference frequency spectrum comprising actual measurements taken during a first part of the drilling or cutting operation, processing a vibration signal from the vibration sensor to produce a real-time frequency spectrum comprising actual measurements taken during a second part of the drilling or cutting operation, comparing the real-time frequency spectrum to the reference frequency spectrum, calculating and detecting a completion or failure of the operation, such as a completion in which the casing has been cut into two casing sections or a failure in which the bit is stuck, based on the comparison of the real-time frequency spectrum and the reference frequency spectrum, and controlling the operation to terminate the operation when completion or failure of the operation has been detected, wherein the step of calculating and detecting a completion of the operation comprises a step of calculating a centre of gravity of oscillation of an area of peaks in the frequency spectrum, which area is above a certain value and comparing that centre of gravity with a centre of gravity of an area of peaks in the reference frequency spectrum, which area is above the same certain value to determine a discrepancy between the two centres of gravity, and wherein the step of controlling the operation is based on the centre of gravity comparison.