Отправлено: 21.06.18 14:48. Заголовок: A proposed solution to the determination of water saturation: using a modelled equation

A proposed solution to the determination of water saturation: using a modelled equation
Jethro Sam‑Marcus · Efeoghene Enaworu · Oluwatosin J. Rotimi · Ifeanyi Seteyeobot

Abstract
Reservoir characterization is an important phase in oil and gas field development, which takes place during the appraisal
phase of either a green field or a brown field upon which further development options are considered. Water saturation is
a very important parameter in the general description of the reservoir as well as equity determination and dynamic modelling.
Numerous equations have been developed which have been used to determine water saturation, but calculated water
saturation values have been inconsistent with the saturation values determined from core analysis. This is generally due to
their inability to account for the varying distribution of shale in the reservoir and the often incorrectness of their underlying
assumptions. The major aim of this research is to develop a model which can be used to determine water saturation values
using data from well logs; also, to compare the developed model with other existing models used in the oil and gas industry,
using data from core analysis and well logs as the input data; and then finally, to discuss the results of the comparison, using
the core-derived saturation values as the bench mark.

The model is based on a parallel resistivity model, which is based on
the assumption that the conductivity of the sandstone term and the shale term exist in parallel in the shaly-sand reservoir.
The shale term in the reservoir of the model is based on the assumption that the clay-bound electrons do not move in the
same conductivity path as the sandstone electrons.

The shale conductivity term is based on the bound water saturation and
the bound water resistivity. The modelled equation was compared in two scenarios using well log data and core data from
two different reservoirs, and the model showed consistency in predicting the average water saturation in both reservoirs.
The results of the comparison were positive for the modelled equation, as it gave coherent results in both comparison scenarios
and matched reasonably the average water saturation of the selected reservoirs. This developed model can serve as
an accurate means of determining water saturation in reservoirs, especially for reservoirs with similar characteristics as the
selected reservoirs in this research.