Use of Geostatistics in Planning Optimum Drilling
Program
Shankhar Ghose
Application of geostatistics in the natural resources industry is well
established. In a typical process of estimation, the statistically dependent
geological data are used to predict the characteristics of a deposit. The
estimator used is the best linear unbiased estimator (or BLUE), and a numerical
factor of confidence is also provided. The natural inhomogeneity and anisotropy
of a deposit are also quantified with preciseness.
Drilling
is the most reliable way of obtaining data for mining and related
industries. However, it is often difficult to decide what is the optimum number
of drill holes necessary for evaluation. In this paper, sequential measures of
percent variation at 95% confidence level of a geological variable have been
used to decipher economically optimum
drilling
density. A coal reserve model has
been used to illustrate the method and findings. Fictitious
drilling
data were
added (within the domain of population characteristics) in stages, to obtain a
point of stability, beyond which the gain was insignificant (diminishing
marginal benefit). The final relations are established by graphically projecting
and comparing two variables--cost and precision. By mapping the percent
variation at each s age, the localized areas of discrepancies can be identified.
These are the locations where additional
drilling
is needed. The system can be
controlled if performed at progressive stages and the preciseness toward
stability is monitored.
AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.