Michael Kaminski Team Leader Endor Upstream Technology
Directorate David Pelly Technology Team Leader Upstream Technology
Group
Slide 5
Detects the presence or absence of hydrocarbon concentration in
subsurface traps. Depth of hydrocarbon field. Size and form of
hydrocarbon field. Oil Gas Coal CBM Water Geothermal water
Radioactive materials Minerals Conventional geophysical methods can
only obtain information about the rock matrix, subsurface
structures and layers that could bear groundwater, but the presence
of water, gas, and oil is only determined once drilling
commences.
Slide 6
Achieve superior exploration success from a focused,
technology-driven balanced exploration program. Seismic acquisition
and processing, reservoir imaging, reservoir properties from
seismic; basin analysis; seals and structure; seismic
interpretation; and visualization. Primary application is in
Exploration but also includes application for delineation,
exploitation, major capital projects and reservoir management.
Slide 7
Improve risk and uncertainty quantification and cycle time
reduction through increased investments to address gaps and rebuild
organizational capacity in seismic acquisition and processing,
seismic analysis; volume interpretation; integrated basin analysis;
controlled source acoustical resonance; (CSAR) and development of
standard workflows. Endor's commitment to the development of oil,
gas, and mineral exploration technologies is reflected in the
successful targets developed.
Slide 8
(so is Poindexter!) How do you do it?
Slide 9
Slide 10
The electroseismic technique is based on the generation of
electromagnetic fields in soils and rocks by seismic waves. The
method measures the hydraulic conductivity which is related to
permeability and therefore water, gas and oil flow can be
extrapolated.
Slide 11
Based on the phenomenon of electrokinetic signals that are
generated through the relative movement of fluids and gases against
the sub- surface rock matrix. This movement of the fluids and gases
is established through a seismic wave artificially generated at the
surface. By proper processing and interpretation of the
electrokinetic signal measured at the earth surface, the presence
of fluids and gases, the estimated depth and a probable geometry
can be determined. What sets this technology apart from
conventional geophysical methods is the fact that the presence of
presence of fluids and gases is responsible for the generation of
electro-seismic signals.
Slide 12
The interest of the technique is therefore to measure the
electrokinetic effects which are initiated by sound waves passing
through a porous rock inducing relative motion of the rock matrix
and fluid. When the ionic fluid moves through the rock sample, the
cations are attracted to the walls and the applied pressure and
resulting fluid movement relative to the rock matrix produces an
electric dipole.
Slide 13
In the technique of the electroseismics, the electric dipole
produced gives a signal. The rise time of the electrical signal is
inversely proportional to the rock permeability. The frequency of
the signal is determined by the frequency of the pressure pulse and
by the permeability of the aquifer. The fluids and gases can move
easier and faster in a more permeable rock and generates a higher
frequency response than from less permeable rocks. The conductivity
of the fluid and gases also determines the amplitude of the signal.
Conductive (blackish or saline) water tends to short circuit the
signal generating process and reduces the amplitude of signals.
Fresh water produces signals that can be several mill volts in
amplitude.
Slide 14
A normal seismic source creates a sharp seismic pulse. This
travels through the ground at the velocity of sound. When it enters
the matrix containing fluids and gases the fluid, which is less
compressible, is forced to move as the rock matrix, more
compressible is deformed. Fluid carries ionic charge with it away
from the ions of the opposite charge, which are stuck to the pore
surfaces. The charge separation distributes the electromagnetic
field and the disturbance propagates to the surface at the speed of
light.
Slide 15
The signals are strongly dependent on at least three main
physical properties; porosity of the rock, permeability and fluid
chemistry. In theory there is no seismic electric response in
partially or unsaturated media so the geological medium must be
saturated by an electrolyte. The permeability has a strong
influence on streaming potential when the fluid is resistive and
hence affects the electro kinetic response as these effects are
related and it is why we can detect oil.
Slide 16
Furthermore electro kinetic signals are divided into two types.
The first type of signal is a nonradiating field, which occurs in
homogeneous media and is contained within and travels with the
seismic P-waves. The second type of signal is raised when the
P-waves passes through a boundary with contrast in elastic and /or
electrokinetics (fluid-chemistry) properties. The electric signals
diffuse rapidly to the sensors with an apparent velocity that is
much faster than any seismic wave. Thus the signal will arrive
nearly simultaneously across the probe sensor. The second type is
the signals that can be used to determine hydrogeological
properties.
Slide 17
When a seismic wave encounters an boundry layer interface, it
creates a charge separation at the interface forming an electric
dipole which can be detected by an probe on the ground
surface.
Slide 18
Slide 19
Electrokinetic potentials arise because of fluid flow through
porous media in response to a pressure difference where =
dielectric constant of water (80 0 ), = Zeta potential of mineral
surface (~-60 mV), = fluid viscosity, and = fluid
conductivity.
Slide 20
The ES Fresnel zones may be defined analogously to the seismic
Fresnel zones in Figure above a monochromatic seismic source ( S)
is located above a horizontal interface between media of different
electrokinetic properties. The spherically spreading seismic wave
intersects the interface and causes fluid flow across the
interface. Due to the streaming current imbalance at the interface,
electric dipole sources oscillating in phase with the seismic wave
are created on the interface. EM waves are radiated from the dipole
sources and are recorded at the observation point ( M).
Slide 21
Where ks = 2 / s is the propagation constant of the seismic
wave with a wavelength s = vs /f, where vs is the speed of
propagation of the seismic wave and f is the source frequency.
Similarly kem = 2 / em is the propagation constant of the EM wave
with a wavelength em = vem /f, where vem is the speed of
propagation of the EM wave. Since the speed of propagation of
seismic and EM waves in earth material differ by 2 to 3 orders of
magnitude, we have kem