The Vacuum oil field was discovered in Lea County, New Mexico in 1929 on the northwest shelf of the
Permian basin. Vacuum cumulative production, primarily from the Permian age Grayberg and San Andres
dolomites, totals more than 600 MMBO and 800 BCF gas from 2400 wells at 4200 to 4800 feet.
Enhanced Recovery Project
A research project organized through the Colorado school of Mines, using multiple 3-D seismic surveys
and multiple geochemical surveys, evaluated both tools for tracking hydrocarbon movements in an
enhanced recovery project on the Vacuum oil field. Results of the seismic portion of the project are
available
here. The orange box shows the one square mile area studied for this project. The structure,
below, is the map generated from the multiple 3D seismic surveys. The six CO2 injectors are shown
along with two established faults and two probable faults. This same structural map is overlaid on the
"net
 change" geochemical survey maps below.
Stucture contour map based on the top of the San Andres. Interval, 100 feet. Roy Milks (1957) and the Roswell Geologic Society.
The first net change map shows a pronounced sweeping of hydrocarbon away from the injectors and
down
 the structure both to the north and south. The hydrocarbons are also moving away from the
injectors to the east and west but they are moving towards the highs.
Survey 1 Baseline 3/98
Survey 2 10/98
Survey 3 10/99
Net Change Iodine, Survey 1 to Survey 2
Net Change Iodine, Survey 1 to Survey 3
Lea County, New Mexico
Vacuum Oil Field
Survey 1 Baseline 3/98
Iodine Survey Results
The first survey, below (3/98), was before any CO2 injections and represents a baseline to evaluate the
next two surveys. The baseline iodine data indicated substantial anomalies (remaining hydrocarbons)
associated with this elderly Field. If we use the baseline survey as a measure of subsurface hydrocarbons
at each sample location then other than analytical error the differences between the baseline and
subsequent surveys should be the net change in underlying hydrocarbons. If a reading goes lower the
hydrocarbons have moved away, if values increase hydrocarbons have moved to that location. The "net

change maps" should represent the subsurface hydrocarbon movements responding to the CO2 injections.
The net change map for the baseline to the third survey is very similar to the first net change map. The
swept areas to the north have remained much the same, to the south there are few increases south of the
fault The areas around the injectors is largely swept with the exception of the southwest injector with a
very high value on a possible fault. Most of the increases in  hydrocarbons are now on or very close to
the structural highs.
These surveys have established real time relationship between soil iodine and subsurface hydrocarbons.
Geochemical surveys should be a useful tool to monitor hydrocarbon movements associated with CO2
enhanced recovery projects.  
GrayStone Exploration Labs, Inc
GrayStone Exploration Labs, Inc