Application of Adaptive Processing Technique for the Inversion of Open Hole Logs Recorded in Oil Fields of Indian Basins
J. P. Narayan and Dr Lalaji Yadav*
Petrophysics Division, KDMIPE, ONGC, Deharadun-248195, INDIA
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6th International Conference & Exposition on Petroleum Geophysics “Kolkata 2006”
(505)
Introduction
During the Second World War, Norbert Weiner of
MIT, USA, one of the foremost mathematicians of the
century, was asked to develop a technique for extracting radar
signals from noise. The method of least square optimization
developed by him eventually proved to be useful in many
other applications in information processing. This approach
with different assumptions and limitations was also presented
by Geophysical Analysis Group (GAG–MIT), under the
leadership of E.A. Robinson, in sixties for enhancement of
offshore seismic reflection data which is considered as digital
revolution in seismic exploration. After a lapse of almost
three decades,
Mayer and Sibbit (1980), used the least square
optimization for formation evaluation (GLOBAL). This was
followed by Alberty and Hashmy, 1984 (ULTRA).
This paper deals with application of - Adaptive
Processing Technique for Comprehensive Well Log
Evaluation (APTWEL) developed in 1984-88. APTWEL
performs inversion of open hole logs by solving the
simultaneous system of logging tool response equations
through statistical approach by using weighted least square
minimization technique. It involves minimization of the
Application of Adaptive Processing Technique for the Inversion
of Open Hole Logs Recorded in Oil Fields of Indian Basins
J. P. Narayan and Dr Lalaji Yadav*
Petrophysics Division, KDMIPE, ONGC, Deharadun-248195, INDIA
Summary
Adaptive Processing Technique for comprehensive well log evaluation solves the simultaneous system of logging tool response
equations through statistical approach by using weighted least square minimization technique. It involves minimization of the incoherence
function i.e. summation of square of errors between the measured and constructed logs by incorporating the total uncertainties on tools,
parameters and response equations. It also simultaneously optimizes the unknowns and zones parameters in different way. It introduces the
statistical theory that least square estimates are the mean estimates and only mean values are optimized while selecting minerals parameters
for a particular zone. Process is adaptive in the sense that it uses the results of previous stage/level as the input to the next stage/level.
Adaptive Processing Technique has been successfully in use for comprehensive well log evaluation of all type of reservoirs of
Indian Basins. Siliciclastics complex reservoirs of Upper Assam, Krishna Godavary and Kavery Basins, Western on Shore and offshore,
fractured and non fractured carbonates reservoirs of Mumbai High have been processed with this package. Evolution of basic concept of
inversion of open hole logs through weighted least square technique and how basic conditions, which ensures the mathematical feasible
solutions for the log evaluation problem, are linked through parameter selection on cross plots are illustrated with actual field examples.
Selection of parameters on cross plots which ensures feasibility of the mathematical solutions and minimum value of incoherence /error
function are essential for the successful application of the package. The log analyst has to achieve the meaningful results by fine-tuning the
parameters within the uncertainties defined on the log measurements. An improper parameter selection can produce a meaningless paralogs,
which may not corroborate at all with the geological model/ reservoir characteristics of the field.
http://www.spgindia.org/conference/6thconf_kolkata06/22.pdf
Отправлено: 22.05.11 06:41. Заголовок: Inversion of Open Hole Logs Recorded in Oil Fields of Indian Basins
