Schlumberger

APS Accelerator Porosity Sonde

Accurate porosity and shale evaluation from epithermal and thermal neutron measurements using a pulsed neutron generator

The APS accelerator porosity sonde uses an electronic pulsed neutron generator (PNG) to deliver both epithermal and thermal neutron measurements. The relative insensitivity of the measurements to the borehole environment and formation characteristics, such as lithology and fluid salinity, provides accurate data for evaluating porosity, detecting gas zones, and correcting for borehole irregularity. Because clays and mixed carbonate lithologies have little effect on the hydrogen index measurement made by the APS sonde, true formation porosity is obtained and gas effects are more visible.

Measurements can be performed by the APS sonde in both open and cased holes.

Improved measurements and wellsite safety

The use of a PNG instead of a conventional radioactive chemcial source means that the APS sonde is ideal for wells with difficult conditions and a greater likelihood of sticking. Logistics are simplified and the concerns of deploying chemical sources are eliminated.

Shale evaluation with greater vertical resolution

The porosity measurement by the APS sonde has a much lower sensitivity to clay than conventional logging. The result is improved identification and evaluation of shales, shaly sands, and thin beds. The thermal neutron formation capture cross section (sigma) measurement significantly focuses the vertical resolution for shale evaluation, which is usually obtained from gamma ray measurements.

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