CST Chronological Sample Taker | Schlumberger

CST

Chronological sample taker

Collect up to 90 sidewall core samples in one run

The CST chronological sample taker acquires sidewall cores using a series of core recovery bullets fired into the formation. Various bullet designs are available, corresponding to the degree of formation consolidation.

20,000-psi pressure rating
400- or 450-degF temperature rating for explosive charges
H₂S service
CST Chronological sample taker

Surface-controlled bullet firing

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 to release the gun from the core bullet, which prevents a stuck core resulting in a stuck CST sample taker.

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