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Downhole Measurements

Drill String Tools

Pressure Core Sampler

The PCS is a free-fall deployable, hydraulically actuated, wireline-retrievable sampling device intended to return formation sediment and fluid samples at hydrostatic pressure. The system is fully compatible with standard APC, XCB and MDCB drilling and coring hardware, allowing pressurized samples to be collected at any time from the mud line down to the depth of indurated formations or hard rock. The PCS is of particular interest to scientists studying frozen hydrates, gases, or other pressure-sensitive materials which tend to degrade during conventional core retrieval and rig-floor handling. Unlike the WSTP, which draws fluid and gas into an evacuated chamber and can therefore alter the chemistry of the sample, the PCS is intended to trap ambient pressure at the time that the sample is collected; also unlike the WSTP, the PCS returns a solid sample.

The PCS comprises several components: a detachable sample chamber, a ball-valve subassembly that traps pressure in the chamber, an actuator assembly that catches the ball valve and pulls the core tube into the sample chamber, a latch assembly that directs torque to the PCS cutting shoe and serves other standard coring functions, an accumulator that maintains pressure in the sample chamber, and a manifold assembly that allows fluid and gas within the PCS to be monitored and accessed under pressure. The PCS can recover a 42-mm-diameter core sample, 0.86 m long, at pressures up to 68.9 MPa (10,000 psi). A detailed description of the PCS with tool drawings is available as ODP Technical Note 17 (Pettigrew, 1992). For tool specifications and schematics see Technical Note 31.

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