Methods and apparatus to produce stick-slip motion of logging tool attached to a wireline drawn upward by a continuously rotating wireline drum

An apparatus for logging a cased well comprising:

• a logging truck having a wireline drum capable of continuous rotation;
• a wireline with one end wound on said wireline drum;
• a wireline with the other end attached to a logging tool disposed within the cased well;
• a logging tool suspended in the well that is capable of performing measurements of formation resistivity from within the cased well only while the tool is stationary within the well;
• said logging tool having electrode means which electrically engage the casing for measurements of formation resistivity when the tool is stationary within the well;
• said electrode means producing sticking friction within the cased well when said tool is at rest;
• said electrode means producing rolling friction within said cased well when the tool is moving;
• whereby when said tool is at rest, said electrode means produces sticking friction that exceeds the magnitude of the rolling friction produced by said electrode means;
• whereby eventually the continuously rotating wireline drum results in an upward force by the wireline at the surface on the logging tool that eventually exceeds the combined weight of the tool, the weight of the wireline in the well, and the sticking friction of the logging tool;
• whereby when said tool initially begins movement after being stationary, said electrode means producing moving friction during the initial movement of the tool that is less than the magnitude of the sticking friction produced by said electrode means when the tool is stationary;
• whereby said upward motion of the tool becomes eventually damped out due to hydraulic damping in the well and other energy dissipative mechanisms so that the tool eventually halts after moving vertically in the well;
• whereby when the wireline is would up on a continuously rotating wireline drum, the tool executes periodic stick-slip motion whereby the tool alternatively comes to rest within the well during "dwell times" and alternatively moves vertically upward during a "move times";
• whereby measurements of formation resistivity within the cased well at different vertical positions are obtained during each resulting dwell time so as to record resistivity of geological formations with a tool capable of measurements only when it is periodically stationary within the well which is drawn vertically with a continuously rotating wireline drum.