SNUPAR-a nuclear parameter code for nuclear geophysics applications

A computer code, SNUPAR, has been developed to calculate nuclear measurement parameters for mixtures of elements found in nuclear geophysics applications. Parameters calculated are the neutron slowing-down length, the thermal neutron diffusion length, the thermal neutron capture cross-section, the formation density, the electron density index, the volumetric photoelectric absorption coefficient, and the effective atomic number. The code has been extensively benchmarked with published laboratory measurements and with results from the Monte Carlo Neutron Photon code. Special algorithms have been developed to handle variations in salinity of formation water. The first application has been the successful development of a modified migration-length model to describe the thermal neutron response to Schlumberger´s compensated neutron log. Some examples of applications of the SNUPAR code for determining reservoir gas saturation, carbon-dioxide saturation in an enhanced oil recovery project, and the effects of mineral mixtures on neutron log response are presented