A NEW METHOD FOR MINERAL QUANTIFICATION TO AID IN HYDROCARBON EXPLORATION AND EXPLOITATION

Quantitative information about the reservoir rock minerals is importan t for making technical and business decisions in hydrocarbon explorati on and exploitation. Minerals are usually quantified using mineral pro perties available from published data and rock properties measured in the laboratory used cored samples or in the field using geochemical we ll logs. Despite considerable efforts by many researchers, the rapid q uantification of minerals with error estimates remains a challenge. Th e most widely used method for rapid mineral quantification is the matr ix algebra method that uses the least-squares principle. Although fast and: easy to implement, the conventional matrix algebra method is; co mputationally unstable leading to unrealistic values (negative or grea ter than one) for mineral fractions. In this paper, we present a compu tationally stable method that retains the speed of the conventional ma trix algebra method while overcoming its limitation. The present metho d can be applied to both laboratory (core samples) and downhole (geoch emical well logs) analyses. It is effective in handling over-determine d, determined, and under-determined systems. It also handles both fixe d and variable mineral properties. Unlike the conventional matrix alge bra method, the present method supplements the rock and mineral proper ties with several constraining equations that incorporate prior inform ation about the mineral fractions. The prior information about the min eral fractions, and the measured rock properties are weighted by the r eciprocals of their respective error variances. Involving only matrix operations, the resulting equation to obtain mineral fractions is easy to implement and fast to compute. Programmed as an Excel macro or in Visual Basic, the method has been successfully implemented in our labo ratory since 1993 for quantifying minerals in core samples from divers e rock formations.