METHOD AND APPARATUS FOR PROVIDING REPEATABLE WIRELINE DEPTH MEASUREMENTS

摘要

METHOD AND APPARATUS FOR PROVIDING REPEATABLE WIRELINE DEPTH MEASUREMENTS A well-logging depth measurement system is described. In one form independent signals are produced, each presumably corresponding to the same surface movement of a wireline used to lower a borehole tool if produced under ideal wireline measurement conditions. The system utilizes the signals to provide an accurate d repeatable signal under varying wireline measurement conditions and is particularly suitable for driving a recorder for depth recording and merging measurements from borehole tools lowered in the borehole on the wireline on different runs. In another form of the invention, the independent signals are utilized to detect slippage between the wireline and a tangential wheel used to provide one of the signals. In still another form of the invention, slidably mounted measurement wheels are described which insure tangential engagement of opposite sides of the wireline with equal pressure. Low-load signal generators each responsive to the rotation of the opposing wheels provide independent signals, each ideally corresponding to the movement of the wireline engaged between them. Magnetic marks written on the wireline at selected intervals and related to a known referenced tension are sensed and provide yet another independent signal corresponding to the wireline movement. Automatic processing of these signals provides alarms and corrections for slippage, variations in measurement tension, and cable stretch. This processing assures repeatable depths