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.
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.
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.
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.
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.
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.
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.
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.
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. Check out the
project I participated in with the Colorado School of Mines over the Vacuum Field in New Mexico in 1998.
I conducted multiple surveys that seemed to indicate that surface geochemical data was tracking the
movement of hydrocarbons between the CO2 injectors and the collectors. Also, 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.
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. Check out the
project I participated in with the Colorado School of Mines over the Vacuum Field in New Mexico in 1998.
I conducted multiple surveys that seemed to indicate that surface geochemical data was tracking the
movement of hydrocarbons between the CO2 injectors and the collectors. Also, 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.
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.
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