Print this pageBuilding and Testing Mineral Models for Mineral-Based Formation Evaluation
CARPENTER, ALDEN B.
Reliable estimates of several reservoir properties are potentially available
from
mineral-based formation evaluation. Effective mineral-based formation
evaluation requires an accurate "model" for each significant mineral within a
logged interval. A "model" consists of the average major and trace element
composition and relevant properties of a mineral for an interval of interest. A
particularly effective way to build a mineral model is from chemical analyses of
thin, foot-long core slabs cut from approximately 30 feet of continuous core.
Each foot-long sample is crushed, sampled with a splitter, and chemically
analyzed. The identities of the minerals in a few samples are determined by
x-ray diffraction and/or petrographic analysis. The average composition of each
mineral in the sample set and the mineralogical composition of each sample in
the set can be estimated by a non-linear least-squares analysis of the set of
chemical analyses. The trace element composition of each mineral in the sample
set can be determined by a linear least-squares analysis of relationships
between mineral abundances and bulk rock trace-element content for the sample
set. Relevant mineral properties are then estimated from the average major and
trace element content of each mineral. Estimates of mineralogy from
mineral-based formation evaluation should be checked against the mineralogy
determined for the core.