The Advance Piston Corer Methane (APCM) tool continuously monitors temperature, pressure, and conductivity changes in the core liner during coring, wireline retrieval, and handling to quantify changes that occur in gas-rich cores. By comparing data plots from successive cores, stratigraphic variations and relative amounts of gas stored in sediments can be determined at individual sites and variations between sites can be assessed. Models indicate that the data also provide information on the presence of gas hydrate in the sediment that may disassociate before core retrieval.
Tool Operations
Temperature, pressure, and conductivity sensors are embedded within the piston head on the standard ODP Advanced Piston Corer (APC) (Fig. 1, Fig. 2). During the APC coring stroke, the piston head acts as a plunger to evacuate water from the inner core barrel, which allows the core to enter.
Design FeaturesWireline Deployment
The APCM is deployed at the beginning of APC coring and removed when coring is suspended. A 100-hr long-life battery allows continuous 1-Hz recording of data for the duration of the APC coring sequence.
Benefit: Allows scientists to calculate the amounts of gas stored in sediments.
APCM Specifications
General
Replaces APC piston and snubber in APC assembly
Three sensors: temperature, pressure, and conductivity
Temperature sensor accuracy: ±0.05ºC
Pressure transducer operating range: 0-10,000 psi; ±0.15% full scale
Conductivity sensor: 3-pin Bulkhead Connector (detects gas phase in headspace)
Sample rate: 1 Hz
Electronics
ODP/MBARI design
Motorola 68338 processor
DOS-like operating system
48 MB of flash memory
Two double-C, lithium/thionyl chloride batteries in series—lasts ~100 hr
Typical Operating Range
Very soft to firm sediments (any time the APC is deployed).
Limitations
The APCM can be used any time the APC is deployed.
(July 2004)