Abstract

The core recorder, a mechanical instrument for determining the exact depthat which core is recovered, drilled up or lost, is described. Examples ofcharts from the recorder are explained and interpreted. The uses of the corerecorder are discussed.

Introduction

In the experience of geologists and engineers during coring operations ondrilling wells, many will recall the times when a full core was not recoveredand particularly when the requirement was urgent that they know exactly whatpart of the core was lost. To make this determination, the core recorder wasdesigned. Its uses are many, and only the most obvious will be presented here.Although this discussion will be limited to drilling wells for petroleum, thecore recorder can be used in any type of coring operation.

The principle of the core recorder is the proportional reduction of themotion of core entering or dropping out of the core barrel to a stylus movingin such a manner as to record the reduced motion on a chart. The time elementis registered on the same chart by the revolution of a clock which turns thechart drum. Thus the exact amount of core entering or dropping out of the corebarrel is charted and the time of such entry or exit from the core barrel isprecisely correlated to the depth at which the core is recovered or lost. Lackof movement of the stylus which is revealed by the continued revolution of thechart drum indicates that no core is entering the barrel.

The principles are accomplished by an instrument placed inside of the corebarrel. A cylinder which contains the clock and mechanical apparatus has adiameter smaller than that of the core barrel. Near the top of the cylinder isan eighteen hour clock which turns the drum that contains the chart. Near thebottom of the instrument is a serrated wheel which by friction against theinside of the core barrel is turned as core enters or drops out of thebarrel.

T.P. 2542

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