Survey Design
Exploration Reconnaissance
Large tracts of lands can be evaluated quickly and inexpensively using near
surface geochemical exploration, especially soil iodine or the CASE tool. In many
areas samples taken along roads can provide sufficient data to determine on which
parts of the larger area you might want to concentrate . All of this can be done, in
many cases, prior to lease investments.
surface geochemical exploration, especially soil iodine or the CASE tool. In many
areas samples taken along roads can provide sufficient data to determine on which
parts of the larger area you might want to concentrate . All of this can be done, in
many cases, prior to lease investments.
Using a detailed map (i.e. USGS 7.5 quad) of your area of interest mark
collection points on all the available roads. Base the sample spacing on the
anticipated size of the prospect typical for your area. As an example, if your
looking for something a number of miles across in it's smallest dimension, samples
taken every half mile could be used. If your trying to find a small reef or a channel
you might want to take samples every 1/10 (500 ft.) or 1/20 (250 ft.) of a mile.
Use numbered bags and list the bag number on the map as you collect each
sample. Try to collect samples, if possible, between 40 to 50 feet off the road.
collection points on all the available roads. Base the sample spacing on the
anticipated size of the prospect typical for your area. As an example, if your
looking for something a number of miles across in it's smallest dimension, samples
taken every half mile could be used. If your trying to find a small reef or a channel
you might want to take samples every 1/10 (500 ft.) or 1/20 (250 ft.) of a mile.
Use numbered bags and list the bag number on the map as you collect each
sample. Try to collect samples, if possible, between 40 to 50 feet off the road.
Exploration Detail
Many times the exploration reconnaissance survey will yield one or more areas
of interest. At this point you might want to add a detailed geochemical survey to
these prospects. Detailed surveys will most often require collecting samples "off
road." Although collection of off road samples can be done using a vehicle
odometer and a compass, the best way is to use a GPS. The relatively small
investment in a GPS with a computer interface (~$200) is more than made up
on the certainty of sample location and the simplification of the whole process.
of interest. At this point you might want to add a detailed geochemical survey to
these prospects. Detailed surveys will most often require collecting samples "off
road." Although collection of off road samples can be done using a vehicle
odometer and a compass, the best way is to use a GPS. The relatively small
investment in a GPS with a computer interface (~$200) is more than made up
on the certainty of sample location and the simplification of the whole process.
Many times the simplest method of collecting "off road" samples is to walk. A
man in reasonably good condition should be able to walk eight to ten miles per day
collecting 100 or more samples. Of course this option becomes less practical as
sample density expands but a dirt bike or an ATV can make almost any survey
simple even fun.
man in reasonably good condition should be able to walk eight to ten miles per day
collecting 100 or more samples. Of course this option becomes less practical as
sample density expands but a dirt bike or an ATV can make almost any survey
simple even fun.
As mentioned above the sample density of the detailed survey will be determined
by the size of the expected prospect. A good rule of thumb is to use a sample
density sufficient to place 3 to 4 samples across the smallest dimension of the
prospect. If you are walking, organizing the walks to minimize distance and the
number of samples you are carrying is important.
by the size of the expected prospect. A good rule of thumb is to use a sample
density sufficient to place 3 to 4 samples across the smallest dimension of the
prospect. If you are walking, organizing the walks to minimize distance and the
number of samples you are carrying is important.
Prospect Evaluation
Geochemistry can be used to "check" prospects. Depending on the size, as few as
four high density lines using 40 to 60 samples can confidently evaluate a prospect.
Failure to find a geochemical signature does not mean the prospect will not be
successful it just means the odds have gotten very long. If on the other hand the
limited evaluation shows promise the survey can be expanded to help guide drill
site selection and future development.
four high density lines using 40 to 60 samples can confidently evaluate a prospect.
Failure to find a geochemical signature does not mean the prospect will not be
successful it just means the odds have gotten very long. If on the other hand the
limited evaluation shows promise the survey can be expanded to help guide drill
site selection and future development.
Prospect Detail
Detailed geochemical surveys of prospects generated by other means can be
very useful. Often the integration of the geochemical data will improve the
interpretation of the data used to generate the prospect. An ultra high density
geochemical survey is often warranted based on the relatively minor additional
costs verses the enhanced data. See the above "Exploration Detail" section for
more information.
very useful. Often the integration of the geochemical data will improve the
interpretation of the data used to generate the prospect. An ultra high density
geochemical survey is often warranted based on the relatively minor additional
costs verses the enhanced data. See the above "Exploration Detail" section for
more information.
Development Evaluations
Development evaluations begin with high density "baseline" surveys. Additional
surveys over time can be preformed to find bypassed compartments and track
the depletion of the deposit. If secondary and tertiary recovery programs are
implemented continuing surveys can determine the efficiency of the recovery
program.
surveys over time can be preformed to find bypassed compartments and track
the depletion of the deposit. If secondary and tertiary recovery programs are
implemented continuing surveys can determine the efficiency of the recovery
program.
Geochemical surveys over existing fields, both old and new, have been used
primarily as case studies. Little consideration has been given to using
geochemistry for development but this application may prove to be
geochemistry's best. Geochemical surveys can detect untapped compartments,
avoid edge wells and dry holes and track hydrocarbon movements related to
tertiary recovery injections. Al Gallagher and I participated in a research
project with the Colorado School of Mines over the Vacuum Field in New
Mexico in 1998. We conducted multiple surveys that seemed to indicate that
surface geochemical data was tracking the movement of hydrocarbons between
the CO2 injectors and the collectors. Unfortunately the project was cut short
before this intriguing initial result could be firmly established. Dr. Ron Klusman
has recently published (AAPG Bulletin, v. 87, no. 9, Sept. 2003) a study of the
CO2 injection project at Rangely Field that also finds hydrocarbons and CO2 at
the surface related to the injections 6500 ft. below.
primarily as case studies. Little consideration has been given to using
geochemistry for development but this application may prove to be
geochemistry's best. Geochemical surveys can detect untapped compartments,
avoid edge wells and dry holes and track hydrocarbon movements related to
tertiary recovery injections. Al Gallagher and I participated in a research
project with the Colorado School of Mines over the Vacuum Field in New
Mexico in 1998. We conducted multiple surveys that seemed to indicate that
surface geochemical data was tracking the movement of hydrocarbons between
the CO2 injectors and the collectors. Unfortunately the project was cut short
before this intriguing initial result could be firmly established. Dr. Ron Klusman
has recently published (AAPG Bulletin, v. 87, no. 9, Sept. 2003) a study of the
CO2 injection project at Rangely Field that also finds hydrocarbons and CO2 at
the surface related to the injections 6500 ft. below.
As an example, a standard
square mile section using a
1/10 mile grid would have 81
off road samples. I have
designed three walks each
starting from a different point
on the surrounding roads. The
longest walk is 3.7 miles
collecting 36 samples. As
always the assignment of a
number to a point should be at
the time of collection, taking
that number from the pre
numbered bag. This entire
survey, including the 40
samples along the roads (not
marked), and 8 1/2 miles of
walking can be collected by
one man in one day.
square mile section using a
1/10 mile grid would have 81
off road samples. I have
designed three walks each
starting from a different point
on the surrounding roads. The
longest walk is 3.7 miles
collecting 36 samples. As
always the assignment of a
number to a point should be at
the time of collection, taking
that number from the pre
numbered bag. This entire
survey, including the 40
samples along the roads (not
marked), and 8 1/2 miles of
walking can be collected by
one man in one day.
GrayStone Exploration Labs, Inc.
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