Scientific Application
The Advanced Piston Corer Temperature (APCT) tool is an instrumented version of the coring shoe that is run on the Advanced Piston Corer (APC). It is deployed in soft sediments to obtain formation temperatures to determine the heat flow gradient and is essential in determining hydrocarbon maturity for pollution prevention purposes.
Tool Operation
The APCT is deployed on an APC inner core barrel and provides a precise in situ temperature measurement while adding only 10 min to each core barrel run. Typically, the tool is run starting at 30 m below seafloor (mbsf) and then run after every other core until four good readings are obtained. The shoe is hydraulically stroked 9.5 m into the sediment and remains stationary for ~10 min. The APC inner core barrel is then retrieved, the instrumented shoe is removed, and the data is downloaded into a computer.
Design Features
1) Temperature Measurement Without Wireline Trip
The APCT sensor, electronics, and memory are contained in an annular cavity inside the APC coring shoe.
Benefit: Temperature measurements can be obtained without a special wireline trip with a temperature tool.
2) Minimal Time Impact
The APCT tool is deployed on an APC inner core barrel and remains stationary for ~10 min in the sediment.
Benefit: The APCT provides a precise in situ temperature while adding only 10 min to each core barrel run.
3) Rapid Data Download
The instrumented shoe is removed as soon as the APC inner core barrel is retrieved, and the data are downloaded into a computer program for immediate processing.
Benefit: Hydrocarbon maturity evaluations can proceed during coring to avoid delays for data handling.
APCT Specifications
Motorola 68HC811 microprocessor
32K x 8 bit CMOS RAM data storage
Real-time clock
14-bit analog-to-digital converter
Platinum temperature sensor
±0.02șC accuracy
Typical Operating Range
-20șC to +100șC temperature measurement range
Limitations
Can only be used in soft sediments appropriate for piston coring
Can only be used in relatively stable sediments where danger of hole collapse is minimal
(May 2002)