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ABSTRACT: Small-angle neutron scattering - a new technique to detect generated source rocks

Radlinski, Andrzej P. , Australian Geological Survey Organisation, Canberra City, ACT 2601, Australia

Despite all its sophistication, geochemistry cannot distinguish source rocks that have actually generated hydrocarbons from those that have the potential to do so. In this work we describe a new low cost technique which can detect invasion of pore rock space during primary hydrocarbon migration, thus enabling the identification of hydrocarbon generation zones in organic-rich rocks.

Small-angle neutron scattering is a routine nuclear-reactor-based technique which enables one to detect thermal neutrons scattered at the rock-pore interface. Experimental data are interpreted to provide specific information (e.g. the pore size distribution) about the geometry of the pore space in the range 1 nm to 0.01 mm which covers the entire pore size range for a typical shale. The process of primary migration affects the scattering contrast and may lead to pore deformation, both of which can be readily detected through changes in the scattering intensity pattern.

Case studies include ground-truthing of the technique using an artificially pyrolysed maturity series of source rocks, and natural maturity series of source rocks from petroleum provinces in Australia. The small-angle scattering results are compared with Rock-Eval pyrolysis, vitrinite reflectance and biomarker data. The value of this technique is to identify source rocks that have generated.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia