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Derivation of Stochastic Equations for Computational Uncertainties in PetroPhysical Properties Using a Simplified Algorithm
SOFOLABO, O ADEKUNLE & AMAEFULE JUDE, KEELAN DARE
Abstract
This paper presents a simple mathematical algorithm or procedure for computing the
uncertainties at the various percent of data input, using the stochastic approach of simulating the input variables to
compute the output variables. A simple algorithm was used to derive stochastic equations for some selected petrophysical
parameters using the relative standard deviations techniques (σ). These equations also known as reference
work equations were found to produce reasonably accepted magnitude of uncertainties in the different parameters
associated with cores. Equations were derived for the percent uncertainties in the values of the pore volume of the
core  V_{p}, the fluid saturation – S_{w}, S_{or}, the porosity of the core – Φ, formation factor  F, bulk density – ρ_{B}, the
derived porosity  Φ_{L} and the derived permeability – K_{BU}, Kro, Krw. The uncertainty equations can also be used to
define the maximum level of uncertainty that can be tolerated in any independent variable if the maximum
uncertainty to be tolerated in the dependent variable is known.
Keywords
Stochastic equations; petrophysical parameters; percent uncertainties; Mathematical algorithm; standard deviations; partial derivatives; degree of accuracy; empirical models.
