Heavy oil reserves are often found at relatively shallow depths in
unconsolidated environments and are associated with significant drilling and
logging challenges, especially bad hole condition and hole stability. In these
heavy oil reservoirs, unknown or varying formation water salinity renders
standard resistivity saturation analysis unreliable, and needs to be calibrated
with Dean Stark core results, which are only available months after data
acquisition. Accurate understanding of reservoir properties like oil
saturation, viscosity, relative permeabilities and free water volume is
essential for the efficient and economic development of heavy oil fields.
In this paper, we present an innovative approach to heavy oil
characterization using novel multi-depth of investigation (nuclear) magnetic
resonance (MR), dielectric permittivity and sonic shear dispersion principles.
This paper demonstrates how the MR reliably estimated heavy oil viscosity and
also identified varying invasion profiles across the different hydrocarbon
bearing sands in the reservoir, reflecting subtle changes in reservoir quality.
The three independent radial measurements made by the MR tool allowed an
estimate of the heavy oil mobility, by measuring the extent to which mud
filtrate is able to move the reservoir fluids away from the wellbore.
We discuss how dielectric permittivity is used to provide formation
water salinity (in the absence of a water leg) in the reservoir and also
establish flushed zone resistivity in OBM. In addition, we demonstrate how this
method directly provides irreducible water saturation along with heavy oil
saturation without the need for resistivity data. Finally we review how sonic
shear dispersion and azimuthal data can reliably measure formation slowness in
challenging unconsolidated sands and identify fractures generated during a
leak-off test. We show how the horizontal stress estimation from advanced sonic
processing can be used to reproduce data normally acquired only by such
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