Methodology and algorithm to correct the thermal neutron porosity for the effect of rare elements and rock minerals with high neutron absorption probability

Abstract The thermal neutron porosity is routinely acquired in almost every well. When combined with the density, gamma ray and resistivity logs, basic petrophysical parameters of a reservoir are evaluated. design tool simple, but its interpretation complex affected by formation constituents. most challenging situation occurs when contains elements high absorption probability neutrons. existence such changes transport results false increase measured porosity. problem reported many users throughout years. In 1993, higher due to an iron-rich mineral, Siderite, Nazzazat Baharia formations Egypt. Siderite all minerals have neutrons probability. Recently, 2018, Unayzah field Saudi Arabia also few parts per million gadolinium. Gadolinium rare element that has absorption. Currently, none existing commercial petrophysics software(s) modules correct for effects. This represents challenge petrophysicists properly calculate actual this paper, effects other on discussed, correction methodology developed tested. based integrating physics perform correction. details steps algorithm included, tested applied two fields.