USING FRACTALS TO DETERMINE A RESERVOIR’S
Speaker: Steve Cuddy
Steve Cuddy is a
Principal Petrophysicist with Baker Hughes and an Honorary Research Fellow at
Aberdeen University where he holds a PhD in petrophysics. He also holds a BSc in physics and a BSc in
astrophysics and philosophy. He has 40
years industry experience in formation evaluation and reservoir description. He has authored several SPE and SPWLA papers
and carried out more than 200 reservoir studies. He has been selected as a Distinguished Speaker
for the SPWLA for 2017/18 season.
The petrophysicist contributes to
maintaining and prolonging the lifetime of oil and gas fields by ensuring the
reservoir’s 3D geomodel is accurately initialised with properties that include
porosity, permeability, water saturations and net cut-off. This is very challenging as there is only
limited core and electrical log data available at the well locations.
The petrophysicist helps to determine
a field’s hydrocarbon in place by modelling the distribution of
fluids using a water saturation vs. height (Swh) function. A good Swh function ensures the three
independent sources of fluid distribution data are consistent. These being the formation pressure, core and
electrical log data. The Swh function
must be simple to apply, especially in reservoirs where it is difficult to map
permeability or where there appears to be multiple contacts. It must accurately upscale the log and core
derived water saturations to the reservoir model cell sizes.
Using capillary pressure theory and
the concept of fractals, a practical Swh function has been derived. Several case studies are presented showing
the match between this function and well data.
The function gives an accurate prediction of water saturations, even in
wells where a resistivity log was
not run due to well conditions.
Logs and core data from eleven
fields, with very different porosity and permeability characteristics,
depositional environments and geological age, are compared. This study demonstrates how this Swh function
is independent of permeability and litho-facies types. A method is presented to
identify swept and by-passed hydrocarbon and to normalise true vertical depths
The fractal function
defines the free water level, the hydrocarbon to water contact, net reservoir
and the irreducible water saturation. The
function provides a simple way to quality control electrical log and core data
and justifies using core plug sized samples to model water saturations on the
There are two identical sessions, please register for only ONE session which fits your schedule.
Morning - Tuesday, February 13th, 8am – 9am US Central Time;
Evening - Wednesday, February 14th 8pm – 9pm US Central Time.
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