Schlumberger

CST Chronological Sample Taker

Overview Library

Collect up to 90 sidewall core samples in one trip

The CST chronological sample taker can collect up to 90 core samples in one trip by using a series of core recovery bullets. This percussion-type gun is accurately depth positioned by using a spontaneous potential or gamma ray log. A surface-controlled, electrically ignited powder charge fires a hollow cylindrical bullet into the formation at each sample depth. Each bullet is attached by two retaining wires to the gun; these are used to retrieve the bullet and core. The wires have a breaking strength of approximately 1,800 lbf [8,000 N] to release the gun from the core bullet, which prevents a stuck core from resulting in a stuck CST tool.

Bullet designs and configurations for optimal recovery

The CST guns vary in the number of bullets per gun. Bullet designs are available for optimal core recovery in various ranges of formation consolidation. The recovered sidewall samples are usually large enough for conducting core analysis.

Different sizes and temperature ratings of CST guns are available to fit a wide variety of operating environments.

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Surface-Controlled Bullet Firing for Core Recovery

CST Chronological
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