Scientific Application
The Advanced Piston Corer (APC) is crucial for high-resolution climate and paleoceanographic studies. The APC is a hydraulically actuated piston corer designed to recover relatively undisturbed continuous 9.5 m long oriented core samples from very soft to firm sediments that cannot be recovered well by rotary coring.
Tool Operations
The APC inner core barrel is run to bottom on the coring wireline. Pump pressure is then applied to the drill pipe, which severs the shear pins and strokes the inner core barrel 9.5 m into the sediment. The inner core barrel containing the core is then retrieved by wireline. A wireline packoff at the top of the drill string permits rotation of the drill string and continued circulation while the core is retrieved. After core retrieval, the bit and bottom-hole assembly (BHA) are again advanced 9.5 m, repeating the process.
Design Features
1) Compatibility
The APC inner core barrel is deployed in the same BHA as the Extended Core Barrel (XCB); therefore, both tools can be used interchangeably depending on formation lithification. The Motor Driven Core Barrel and Pressure Core Sampler are also compatible with the APC/XCB BHA.
Benefit: Tools are interchangeable and no time is spent for bit trips.
2) Wireline Deployment
The APC inner core barrel is deployed (and recovered) using the coring wireline to avoid premature release of the shear pins, which determine penetration force of the barrel into the sediment.
Benefit: Allows rapid recovery of core with minimal nonproductive time.
3) Core Orientation
The APC core can be oriented with respect to the Earth’s magnetic field by running a downhole orientation tool above the core barrel.
Benefit: Allows recovery of oriented core for paleomagnetic studies.
4) In Situ Temperature Measurement
Special APC shoes have a pocket in which a thermistor unit can be run to record the in situ formation temperature after taking a core (see APCT tool sheet).
Benefit: Provides in situ heat flow measurements for science and hydrocarbon safety.
APC Specifications
Maximum Piston Stroke (Core) Length
9.5 m (31.16 ft)
APC Shoe Inside Diameter (Core Outer Diameter)
6.2 cm (2.44 in)
Piston Force
23,000 to 28,000 lbf at 2300 to 2800 psi pump pressure
Typical Operating Range
Formation
Very soft to firm sediments
Depth Range
Seafloor to +300 m below seafloor (mbsf)
Recovery
~100% in soft sediments
Rate of Core Recovery
~38.0 to 9.5 m of core/hr (depends on depth/wireline time). Rate of penetration typically decreases with depth.
Quantity of Cores on Deck
1 to 4 cores/hr depending on water depth and formation cored.
Limitations
Does not penetrate or recover granular formations (such as sand) or hard ground. Core barrel may stick in firm sediments and require drill-over.
(May 2002)