METHOD AND APPARATUS FOR PROVIDING REPEATABLE WIRELINE DEPTH MEASUREMENTS

摘要

Well logging depth measurement method and system are described for automatically driving a recorder under varying wireline measurement conditions. This system produces two depth signals. First depth signals correspond to magnetic marks placed at regular intervals on the wireline. Second depth signals correspond to incremental movements of the wireline as produced by mechanically coupled measuring devices. Such measuring devices are subject to slippage, variations in circumference, etc... There are no variations of this type for magnetic mark signals but the intervals between these signals are much larger than the mechanically produced incremental signals and are too far apart to be used to drive a recorder. According the incremental signals are counted for each interval determined by two magnetic mark signals and compared with the number expected for such intervals, a low count indicating slippage or the like. In one form of the invention, a low count is used to provide an appropriate alarm. In another form, an automatic correction for the slippage is provided, the resulting corrected signals being particularly suitable for driving a recorder.