ALEXANDRU BABSKOW, VALERIU PLATON
PETROM, R.A., Institutul de Cercetari si Proiectari Tehnologice, Campina
"OPTIME" METHODS – NEW APPROACH OF WELL LOG PROCESSING AND INTERPRETATION
(Abstract)
The "optime" interpretation procedures, unlike the "deterministic" well
logging interpretation methods and procedures, use an explicit statistical
approach in well log analysis, by the minimization of the differences between
the logging tool observed (real) responses, and the theoretical computed responses – the
output unknown parameters, by applying the "inverse " response equations,
between the input known data and the output unknown estimated parameters.
The petrophysical – petrographic parameters affecting the logging tool
response may be divided into two groups: variable petrophysical parameters,
with a quite quick variation with the depth, and which are assumed to be unknown,
and constant petrophysical parameters, on the whole well profile, or on certain
depth intervals, and which are assumed to be known, each of them having assigned
a certain uncertainty. The "optime" procedure determines a set of
petrophysical parameters, by minimizing the difference between theoretical
and measured responses, each error being weighted with its associated uncertainty.
The weighted sum of the squared errors represents an objective function which
quantifies the minimizing process. In addition, the constraints are defined
by a certain function which limits the uncertainty range to the physically
possible values.
In addition to the best estimation of the unknown petrophysical parameters,
the "optime" interpretation procedure provides indications about
the estimate quality, by determining the confidence intervals, on the basis
of the weighted minimal squared method properties, and also the parameter estimation
quality indicators, for each processing level.
This paper is intended to provide some theoretical aspects of "optime" well
log processing and interpretation, along with applications on some real cases.
The paper also emphasizes the good quality of the interpretation using "optime" methods.
Key words: well logging "optime" methods.