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