The Pressure Core Sampler (PCS) is capable of retrieving core samples from the ocean floor while maintaining in situ pressures up to 689.7 bar (10,000 psi). The primary application of the PCS is to recover in situ hydrates. The PCS is free-fall deployable and wireline retrievable.
The PCS is free-fall deployed down the drill string for intermittent “spot” coring while using the Advanced Piston Corer/Extended Core Barrel (APC/XCB) bottom-hole assembly (BHA). The PCS inner core barrel is latched in to the XCB rotary window sub and is rotated with the drill string while weight is applied to the bit. After cutting the core, a ball is released by wireline action to divert flow to a piston that pulls the core tube into the pressured core barrel and closes the ball valve. The core is then retrieved by wireline.
The PCS is completely compatible with the existing BHA used for the APC and XCB coring systems.
Benefit: The PCS can be deployed during routine coring without a pipe trip.
2) Rotary Latch
The PCS latch dog locks into the APC/XCB latch window in the BHA, which transmits BHA rotation to the PCS. A combination of low weight on bit, slow rotation, and low pump rate is required to core.
Benefit: Fragile samples and sticky clays can be recovered with minimal hydraulic disturbance or contamination.
After the PCS core sample is cut, the actuator hydraulically pulls the inner core barrel and core sample through a ball valve into the sample chamber and closes the ball valve, thereby sealing the sample chamber at in situ pressure.
Benefit: The PCS core sample is trapped at near in situ pressure behind a ball valve that closes by rotation to maintain its seal at both positive and negative pressure differentials.
4) Detachable Sample Chamber
A removable pressure chamber maintains the core sample at near in situ pressure, provides for internal pressure monitoring, incorporates safety pressure release mechanisms, and offers two sampling ports for collecting gas and fluids.
Benefit: Permits the pressured core sample chamber to be moved to a lab for further examination.
Core Sample Diameter
1.70 in. (43.2 mm)
Core Sample Length
39 in. (0.99 m)
Sample Chamber Working Pressure
689.7 bar (10,000 psi) maximum
Sample Chamber Length Overall
67 in. (1.7 m)
Sample Chamber Outer Diameter
3¾ in. (95.25 mm)
Sample Port Thread
¼ in. 18 UNF – 2b
Typical Operating Range
From mudline to indurated formations
Up to ~6500 m combined water depth and formation penetration
Tool is limited to formations composed of soft sediments to firm clay
Sample chamber is short to accommodate lab handling
Core diameter is limited by ball valve size
No method of transferring pressurized cores to an autoclave
Small core diameter could impact scientific sampling
Wireline core recovery time per meter of core increases ≈ 10:1 compared to standard coring system because the core recovered is one-tenth the length of a standard core