Tar Pit
Sulukta Oil Spring
Geochemisty and Seepage
Geochemical Model
Burning Seep
Seepage Model
Oil Drop Seep
Near surface geochemical exploration for hydrocarbons is a natural extension of the first
exploration method, seepage. The first oil well drilled by Colonel Drake in 1858 was
drilled on the banks of Oil creek and over the  next 60 years most oil was discovered
from seeps.
Along with macro-seepage detection, a number of
very successful oil finders claimed that they could
"smell" the oil they discovered.
Advancements in seismic data
collection and interpretation have
recognized the effects from
hydrocarbon gas in the subsurface.
"Acoustic signal attenuation" has been
used to describe these effects on the
seismic response.
These pictures have validated the
empirical model used by geochemical
scientists for seventy years. Not only
do hydrocarbons "leak" from the
subsurface to the surface they make
this journey in a near vertical path.
Placing your mouse over the picture
will draw vertical lines to demonstrate
that the columns of gas penetrate
both dipping and flat beds without
changing their vertical path. It is also
important to note that the column is
not expanding as it rises and shows
no discernible expansion from bottom
to top.
Massive seepage, like tar pits or oil springs represent a tiny fraction of hydrocarbon
accumulations, a slightly larger percentage have small but still visible seeps. However,
almost all accumulations have detectable amounts  of seepage when using modern
analytical chemistry.
Iodine Chemistry
Geochemistry - Theory and Techniques
Geochemisty and Seepage
Geochemistry was developed after
many of the large discoveries using
macro seepage were fading from
memory.  Surface geochemistry found
many indications of hydrocarbons
directly above petroleum
accumulations but had not much
more than the cartoon to the left to
explain the phenomena. The
enormous empirical data base of
these geochemical anomalies still met
with resistance and skepticism.
Recently sophisticated geophysical
surveys have confirmed the basic
hypothesis represented by the simple
cartoon. Mechanisms and
explanations of the gas plumes is still
debated but pictures are worth a
thousand words when it comes to the
"vertical migration of hydrocarbons."
Seismic, Gas Plumes
Once the vertical leakage of hydrocarbons has been established, what is the best way to
detect this leakage and use the data to find petroleum. Research has shown that the
leakage of hydrocarbons at the surface is inconsistent and the flux rates vary with
temperature and pressure. Flux rates are so variable that direct detection of hydrocarbons
has been difficult and often unsuccessful. Various types of time integrated collection
methods have been tried but none have proven reliable and all are difficult and expensive.
Natural integration of the leakage is a much better method and many elements and soil
properties respond to the addition of leaking hydrocarbons. For many of these elements or
properties the initial conditions and natural variations in concentrations are to great to
make the changes produced by hydrocarbons detectable. Picking the proper tool   is the
key to effective geochemical evaluations.
Geochemical Exploration Techniques
Iodine has a number of unique properties that make it an excellent choice for
geochemical exploration surveys.  As the cartoon above demonstrates soil iodine
originates from the atmosphere, eliminating varying initial conditions. Like all halogens,
iodine is a strong oxidizer and reacts readily with hydrocarbons. Volatile hydrocarbons
combine with iodine changing hydrocarbon gases into iodo hydrocarbon solids. These
compounds  can be used to track hydrocarbon seepage.
GrayStone Exploration Labs, Inc.
GrayStone Exploration Labs, Inc.