The following papers were either published in scientific journals or presented orally at national society meetings by Gulf Research scientists and Exploration Technologies, Inc. scientists under the direction of Dr.'s V.T. Jones and T.J. Weismann. They represent the state-of-the-art in surface geochemical exploration and provide the core information for this "Overview of Geochemical Exploration Technology."
1979 AAPG Meeting
Houston, TX April, 1979
"Predictions of Oil or Gas Potential by Near-Surface Geochemistry," by V.T. Jones.
"Role of Biogenic Light Hydrocarbon Generation in Near-Surface Prospecting," by G.G. Janezic.
"Dissolved Hydrocarbons in the Coastal Waters of North America," by R.J. Mousseau and J.C. Williams.
1980 Tenth World Petroleum Congress
1980 Bucharest, Romania
"Developments in Geochemistry and Their Contributions to Hydrocarbon Exploration" by T.J. Weismann.
181st ACS National Meeting
March 29-April 3, 1981
1981 AAPG Meeting
September, 1981 Santa Fe, NM
183rd ACS National Meeting
Las Vegas, Nevada March 28-April 2, 1982
"Chemistry and Dynamics of Sedimentary Basin Waters," by G.A. Cooke.
"Natural Rock Fractures and the Migration of Fluids in the Natural Environment," by R.A. Hodgson.
"Satellite and Aircraft Spectral Detection of Fluid Migration Effects," by M.D. Matthews.
57th Annual Fall Meeting of the Society of Petroleum
Engineers of AIME
New Orleans, LA September 26-29, 1982
186th ACS National Meeting
Washington, D.C. August 28-September 2, 1983
"Computer Based Gas Chromatograph Control and Data Reduction System," by J.D. Melvin and D. Masdea.
"Carbon Monoxide: A Prospective Indicator," by W.C. Sidle.
187th ACG National Meeting
St. Louis, Missouri April 8-13, 1984
"Hydrocarbon contamination in the Near-Surface Soil," by Robert J. Pirkle and R.J. Drozd.
"Mercury as a Pathfinder for Deep-Seated Ore Bodies," by V.T. Jones and J.B. Maciolek.
International Symposium on Remote Sensing of Environment
Third Thematic Conference "Remote Sensing for Exploration Geology"
Colorado Springs, Colorado April 16-19, 1984
American Chemical Society
Miami Beach, Florida April 30-May 1, 1985
Proceedings of the International Symposium On Remote
Sensing of Environment Fourth Thematic Conference
April 1-4, 1985 pp. 381-389
AAPG Bulletin, Vol. 70, No. 7, July, 1986
Second Workshop on Remote Sensing/Lineament Applications
Morgantown Energy Technology Center, April 23 and 24, 1986
Fifth Thematic Conference on Remote Sensing for Exploration Geology, Reno, Nevada, October, 1986
"Remote Sensing and Surface Geochemical Study of Railroad Valley, Nye County, Nevada-Detailed Grid Study", S.G. Burtell and V.T. Jones.
19th Annual Offshore Technology Conference
Houston, Texas, April 27-30, 1987
"A Geochemical Method for Finding Leaks in Submarine Pipelines", R.G. Aldridge and V.T. Jones.
Exploration for Precious Metals Symposium
Reno, Nevada, April, 1987
"Mobile Mercury Applications in the Search for Gold," J.B. Maciolek and V.T. Jones
Sixth Thematic Conference on Remote Sensing for Exploration
Geology
Houston,Texas May 16-19, 1988
"The use of Surface Geochemical Prospecting Techniques to Identify Sedimentary Gas Seepage Through Volcanic and Thrusted Formations" S.G. Burtell and V.T. Jones.
PREDICTIONS OF OIL OR GAS POTENTIAL BY NEAR-SURFACE GEOCHEMISTRY
Victor T. Jones
A near-surface hydrocarbon soil-gas technique developed by Gulf Research
& Development Co. has been shown to be capable of predicting whether
oil or gas is more likely to be discovered in the prospect area. These
predictions are made by using the percent compositions and ratios of methane
to ethane and propane. Typical average values are:
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Intermediate values are expected for many hydrocarbon accumulations.
Extensive studies compiled and reported in the literature have clearly shown that reservoired hydrocarbons contain varying amounts of methane and heavier homologs. Frequency histograms of the sum or ratio of methane homologs illustrate that gas from gas deposits is quite distinguishable from that of oil deposits.
Gases from gas-condensate or combined oil and gas provinces plot intermediate between those of gas or oil only provinces as expected.
Light hydrocarbon ratios have been used successfully to predict the petroleum potential of a formation by monitoring C1-C5 hydrocarbons from a steam-still reflux gas sampling system during routine mud-logging operations (Pixler, 1973). Individual ratios of the C2-C5 light hydrocarbons with respect to methane have been demonstrated to provide discrete distributions which reflect the true natural variations of formation hydrocarbons between oil and gas deposits. Analyses of these same ratios for soil-gas hydrocarbons yield nearly the same limits for delineation of oil and gas potential. This correspondence with the actual formation gases shows that the upward migration of reservoired light hydrocarbons into near-surface soils represents a viable mechanism, allowing near-surface geochemical exploration techniques to be utilized for prospect evaluation.
Normalized histograms of composition data have been constructed which better represent the actual near-surface hydrocarbon populations. Correlations with known producing areas are presented in the Sacramento and San Joaquin Basins in California and from the Pineview and Ryckman Creek Fields in the Utah-Wyoming Overthrust Belt.
DEVELOPMENTS IN GEOCHEMISTRY AND
THEIR CONTRIBUTIONS TO HYDROCARBON EXPLORATION
T.J. Weismann, Gulf Research & Development Co.,
PO Drawer 2038, Pittsburgh, PA 15230, USA
Abstract. This paper considers the exploration significance of developments in organic and other areas of geochemistry. The utility of geochemical criteria in early reconnaissance and developmental stages of exploration of sedimentary basins for crude oils and natural gases is discussed and illustrated with case histories. References to surface (land) and marine hydrocarbon survey technology, source bed determination, hydrocarbon maturation and migration phenomena, post-migration alteration and transformation, correlation processes and nonconventional hydrocarbon sources are made. Advances in spectroscopic techniques such as high resolution GC-mass spectrometry, nuclear and electron spin resonance, infrared and UV-fluorescence and their relevance in correlation of hydrocarbons with stratigraphic units and reservoirs are discussed. Results of an updated literature review on the theories of oil and gas formation will be presented. The role of stable isotopes of carbon, nitrogen, and sulphur in elucidating problems in evolution migration and alteration of petroleum is treated. Hydrocarbon gases, N, S, O organic compounds, and other elements as proximity indicators of petroleum reservoirs will be evaluated.
ROLE OF BIOGENIC LIGHT HYDROCARBON
GENERATION IN NEAR-SURFACE PROSPECTING.
Gary G. Janezic.
Possible biogenic occurrences of C1-C4 light hydrocarbon gases have caused
concern in the interpretation of near-surface geochemical prospecting
data in both land and marine environments. It has long been known that
methane is produced in copious quantities by microbial activity in anaerobic
water flooded soils and marine muds, but the possible production of C2-C4
hydrocarbons has been less well defined and has not been proven conclusively
to occur.Recent studies conducted at Gulf Research & Development Co.
have investigated the anaerobic microbial evolution of C1-C4 hydrocarbons
upon decomposition of various organic substrates. Only methane was observed
in copious quantities with minor amounts of ethylene co-produced. Ethane,
propane, or the butanes were not evolved.
A methane: ethane ratio >500 appears sufficient to delineate anaerobic
biogenic gas production from migrated petroleum hydrocarbons since such
ratios rarely occur in abiogenic natural gas deposits. Because surface
geochemical compositional parameters reflect those of known production,
diagenetic gases do not appear to be a major interference in this type
of petroleum prospecting.
DISSOLVED HYDROCARBONS IN THE COASTAL
WATERS OF NORTH AMERICA
Richard J. Mousseau and John C. Williams
Dissolved methane and propane concentrations measured aboard Gulf's
exploration vessels, the R/V HOLLIS HEDBERG and the M/V GULFREX, on the
continental margins of North America are discussed. Propane concentrations
of less than 0.5 nanoliters/liter were observed in a majority of the samples
in many of the areas studied. This is in agreement with open ocean concentrations
reported by Swinnerton and Lamontagne.
However, in a highly petroliferous area like the Louisiana offshore, higher
propane concentrations occur more frequently with 1/3 of the samples exceeding
2 nanoliters/liter. In the Louisiana offshore, 3/4 of the samples contained
over 250 nanoliters/liter of methane, whereas the reported open ocean
concentrations show a majority of the samples contained less than 50 nanoliters/liter.
Generally, on the continental shelf, a local contribution is indicated
more frequently for methane than for propane.
The seawater hydrocarbon concentrations are compared to the United States
Geologic Survey estimates of undiscovered oil and gas resources in each
of the offshore geologic provinces where data was collected.
ISOTOPE GEOCHEMISTRY OF SHALLOW
GROUNDWATER AS AN INDICATION OF ACTIVE GAS MIGRATION.
R.J. Drozd, J. Krushin, H.W. Rauch, D.A. Jeffrey.
Carbonate cements with unusual carbon and oxygen isotopic compositions have been reported over hydrocarbon reservoirs. It has been suggested that the identification of such areas may have exploration utility. The unusual isotopic ratios are thought to be due to rapid migration of hydrocarbons from a reservoir and their possible oxidation. Isotopically distinct cements imply the prior existence of carbon dissolved in the groundwater. The identification of such cements indicates that hydrocarbon migration once occurred, but not that it is actively occurring. The detection of isotopically unusual carbon species in groundwater suggests ongoing hydrocarbon migration. This study involves the investigation of carbon and oxygen isotopes of dissolved carbon species, light hydrocarbon gas concentrations, and inorganic chemistry of shallow groundwater in areas of West Virginia and Kentucky.
OIL-GAS CORRELATIONS BY FLUORESCENCE
SPECTROPHOTOMETRY
G.G. Janezic, M. Rodgers, R.C. Burruss, and D.A. Jeffrey.
Gulf Research & Development Company, P.O. Drawer 2038, Pittsburgh,
PA 15230
Synchronous fluorimetry of the aromatic fraction of crude oils provides an additional correlation technique which can be applied with other chemical fingerprinting analyses for a genetic classification of oils within a sedimentary basin. It is estimated that greater than 90% of oil fluorescence is attributed to aromatic constituents with minor contributions from resin and asphaltene fractions. Fluorescence wavelengths and intensities are a direct function of the number of fused aromatic rings. Oils of high API gravity exhibit maximum fluorescence intensities at lower wavelengths due to an enrichment in 1- and 2-ring aromatic components. Although significant oil migration in a sedimentary basin may alter the proportion of aromatic constituents present in an oil, genetically related oils of slightly differing API gravities exhibit similar relative fluorescence intensities due to similar proportions of aromatic ring components. Oil correlations based upon fluorogram fingerprinting have generally agreed well with more detailed chemical fingerprinting of biodegraded and nondegraded oils.
PYROLYSIS AS A GEOCHEMICAL SCREENING
TECHNIQUE IN OIL EXPLORATION
J.M. Patterson, W.F. Kardosh, and D.A. Jeffrey.
Gulf Science & Technology Company, P.O. Drawer 2038, Pittsburgh, Pennsylvania
15230
The IFP-FINA "Rock-Eval" pyrolysis instrument has been utilized
for source rock correlation studies on several recent wells. The method
has been shown useful as a rapid means to determine petroleum generating
potential and degree of maturation of the source rock. The isolated soluble
hydrocarbon fractions have been analyzed also by the Rock-Eval technique
to determine the extent of overlap of the S1 (250-350ºC) and S2 (350-550ºC)
peaks. Our studies indicate an excellent correlation of the S1 peak and
saturated hydrocarbons while aromatic HC's tail into the S2 peak.
Resins and asphaltenes are pyrolyzed as predominantly S2 peak with the
skewing toward the S1 peak. Kerogen gives a rather symmetric S2 peak.
The Rock-Eval pyrolysis method is effective as a screening technique but
should be used with confirming geochemical methods.
CORRELATION OF WELL GAS ANALYSIS WITH
HYDROCARBON SEEP DATA
J.C. Williams, R.J. Mousseau and T.J. Weismann.
Gulf Research & Development Company, P.O. Drawer 2038, Pittsburgh,
PA 15230
Chemical Instrumentation installed on modern petroleum exploration vessels
like Gulf Oil's R/V HOLLIS HEDBERG allows the explorationist to search
for seeps in the marine environment.
A comparison of methane and propane concentrations in the coastal waters
of the United States to the uncontaminated open ocean concentrations indicates
methane is added to sea water on the continental margins much more frequently
than is propane. The mean methane and propane concentration in the OCS
provinces appear correlated to exploration results in these regions.
Recent advances in this technique emphasize the examination of the ratios
among the concentration of the gaseous hydrocarbons to predict whether
an anomaly is more likely to reflect seepage from an oil, a condensate
or a gas source. Cross plots of the best predictive composition ratios
show the same patterns for both gases measured at the wellhead or in the
sea water hydrocarbon anomalies. Guidelines for successful application
of this technique are presented.
HELIUM AND HYDROGEN SOIL GAS ANOMALIES
ASSOCIATED WITH DEEP OR ACTIVE FAULTS
V.T. Jones and R.J. Pirkle.
Gulf Research and Development Co., P.O. Drawer 2038, Pittsburgh, PA 15230
GS&T has been conducting helium and hydrogen geochemical surveys since 1974 which strongly support the association of both these elements with tectonic activity. Examples will be given over the San Andreas Fault in California, the Duchesne Fault Zone in the Uinta basin, and a thrust fault near glacier National Park in Montana. The largest helium anomaly observed was 1243 ppm near Glacier National Park while a maximum value of 350 ppm was observed over the San Andreas Fault and 372 ppm over the Duchesne Fault Zone. Hydrogen values are typically between twenty to several hundred ppm. Hydrogen anomalies are also associated with petroleum deposits. Measurement of these gases can be useful in interpretation of geochemical data.
USE OF COMPOSITIONAL INDICATORS IN PREDICTION
OF PETROLEUM PRODUCTION POTENTIAL
R.J. Drozd, G.J. Pazdersky, V.T. Jones & T.J. Weismann.
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA.
15230
In soil gas geochemistry percent methane and ratios of methane to ethane and propane have been successfully used to predict production potential. Because these parameters are methane dependent, analyses are subject to an inherent bias which could lead to misinterpretation particularly where methane is derived from a bioqenic source. Since ethane is second in abundance to methane and is not subject to abundant biogenic generation, ratios using ethane should be more reliable. Ethane to propane and ethane to normal butane ratios provide alternate means to distinguish between oil, condensate and gas phases, and can confirm validity of methane dependent indicators. Application of these ratios is demonstrated with data from several soil gas studies and results are compared for land and marine data. Data sets predictive of oil condensate and gas in marine and soil gas analyses show similar compositional characteristics as would be expected if there were no fractionation in the seep process.
A THERMAL ANOMALY DETECTED BY SHALLOW
MEASUREMENT ACROSS THE SAN SEBASTIAN OIL AND GAS FIELD, EASTERN TIERRA
DEL FUEGO
Gary W. Zielinski, Peter M. Bruchhausen
Low thermal diffusivity of peat and soils overlying portions of the oil, and gas province of the eastern Magellan Basin has resulted in a small number of unusually shallow (<2m deep) relative heat flow determinations. The values are in agreement with the single published heat flow value for Tierra del Fuego of 2.3 HFU and with deep bottom-hole temperature measurements located in coincidence with the shallow determinations. They are furthermore consistent with local surface air temperature measurements obtained for a period of one year prior to the field work. Compared with that for similar tectonic provinces (post precambrian, non-orogenic) the heat flow in eastern Tierra del Fuego appears to be about 0.5 HFU greater than might be expected. Maturation level estimates based on burial history of sediments in the area suggest considerable lateral migration (~100 km) of hydrocarbons from deeper in the Magellan Basin. A model is explored whereby the same mechanism for transport of the hydrocarbons, namely, deep ground water movement can also explain the heat flow results. The dramatic 10 HFU decrease in relative surface heat flow observed across the southwestern edge of the San Sebastian oil and gas field is of similar magnitude as other thermal anomalies reported to be in close association with hydrocarbon accumulations.
CHEMISTRY AND DYNAMICS OF SEDIMENTARY
BASIN WATERS
G.A. Cooke
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA
15230
Fluids migrate in sedimentary basins in response to forces such as compaction,
mineral dewatering, and gravity recharge. The water generally moves radially
outward from the center of the basin if sediments are currently being
deposited or inward from the basin edge if uplift and erosion have exposed
aquifers to recharging waters.
Maps of current pressure distribution can be used to determine the potential
for fluid migration in a given direction. However, the amount of fluid
motion cannot be determined with pressure data alone. The magnitude and
direction of the driving forces vary with time and the uneven distribution
of permeable and impermeable sediments also affect migration rates.
The relative magnitude of fluid migration can be assessed by examining
the chemistry of the sediment waters. The subsurface water chemistry is
the result of a number of factors. These are primarily the initial water
chemistry, aqueous-solid interactions, membrane filtration, mineral dewatering,
and the mixing of waters from differing sources. Examining the source
and history of the dissolved species provides direct evidence of the magnitude
and direction of subsurface fluid migration.
THE DETERMINATION OF MIGRATION
PATHWAYS USING CRUDE OIL AND EXTRACT CORRELATIONS.
W.F. Kardosh, D.A. Jeffrey
Gulf Research & Development Co., Houston Technical Services Center,
P.O. Box 36506, Houston, TX 77036 and G.G. Janezic, Gulf Research &
Development Co., P.O., Drawer 2038, Pittsburgh, PA 15230
Geochemical correlation between an extract from a source rock and reservoired
petroleum can be an extremely useful tool in determining migration pathways
in a basin. Such correlations depend upon the recognition of compositional
similarities between extracts remaining in the source rock and generated
products which have migrated from the source rock.
Since crude oils and extracts are complex mixtures consisting of many
components, no simple method for complete chemical characterization exists.
Early attempts at crude oil correlations depended on bulk physical and
chemical properties such as density, sulfur, nitrogen, pour points, etc.
With the development of more sophisticated analytical instrumentation,
crude oil correlations have evolved into using specific compounds or compound
distributions to permit differentiation between individual source beds
and oils.
NATURAL ROCK FRACTURES AND THE MIGRATION
OF FLUIDS IN THE NATURAL ENVIRONMENT
R.A. Hodgson.
Gulf Research & Development Co., P.O. Drawer, 2038, Pittsburgh, PA
15230
Systematic and Non-systematic rock fractures comprise effective avenues for both vertical and lateral migration of fluids under a variety of stress and geometric conditions. The systematic fracture network reflects elements of the regional tectonic framework and understanding the genetic aspects of this geometric association can provide clues to the mechanism and timing of fluid migration in the natural geologic environment.
SATELLITE AND AIRCRAFT SPECTRAL
DETECTION OF FLUID MIGRATION EFFECTS.
M.D. Matthews. Gulf Research & Development Co., P.O. Drawer 2038,
Pittsburgh, PA 15230
Through the Geosat-NASA test case program, the usefulness of remote sensing data for petroleum/mineral exploration is being evaluated. The potential usefulness of this data as an aid to understanding, detecting, and mapping surface evidence of present and paleo fluid migration occurrences will be summarized. The ability to detect secondary mineral alteration haloes related to hydrothermal mineral emplacement by 1.6 and 2.2 um data will be demonstrated. This ability will be contrasted with similar attempts to understand fluid migration resulting in or related to uranium and/or petroleum accumulations. Emphasis will be placed on imaging systems but visible-near IR spectrometry data from laboratory and field devices as well as airborne line profiling information will be presented.
LIGHT HYDROCARBON, HYDROGEN, AND HELIUM
ANOMALIES IN THE EASTERN SNAKE RIVER, IDAHO
W.C. Sidle, V.T. Jones
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA
15230
Analyses of 546 water wells by gas chromatography from the Eastern Snake
River Plain (ESRP) were conducted during the post recharge season in 1979.
Both light hydrocarbon and non hydrocarbon dissolved gas anomalies were
discovered after repeated surveys.
Accompanying reconnaissance geologic and geophysical studies reveal a
close correlation between Pliocene rhyolite caldera complexes and the
hydrogen and carbon dioxide anomalies.
Helium point-sourced anomalies are centered near an ovoid 400 magnetic
high. Masking the Pliocene volcanic structures are extensional volcanic
terranes that may be affecting the migration of these gases thought to
be linked to residual magnetic processes.
Light hydrocarbon gas anomalies appear to be more spotty and have mixed
source populations. Generally they group away from the caldera complexes.
One prominent anomaly may be the result of hydrodynamic fluids migrating
from Paleozoic marine sediments at depth. Migration of source gases are
complicated by the volcano tectonic terrane overprinted on Paleozoic marine
allochtonous sheets along the margins of the ESRP. Rectilinear arrays
of Recent rifting are thought to reflect these older structural trends
in the marine sediments where potential hydrocarbon reservoirs may be
present.
GAS MONITORING AT ARROWHEAD HOT
SPRINGS NEAR THE SAN ANDREAS FAULT, SAN BERNARDINO COUNTY, CALIFORNIA
V.T. Jones, S.G. Burtell
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA
15230
Geochemical data was collected on a semicontinuous basis from a concreted hot spring at Arrowhead springs from 12/8/81 to 12/1/82. The spring, which is located on a splay of the San Andreas fault releases significant quantities of free gas which has been analyzed for seven light hydrocarbons (methane, ethane, propane, iso-butane, normal butane, ethylene and propylene), helium, hydrogen and carbon dioxide. Although sample collection intervals were variable over this time period, systematic magnitude and compositional changes were recorded for the measured gases. Hydrocarbon magnitudes nearly doubles by July 1982 and remained fairly stable until sample collection termination on 12/1/82. This type of change may indicate a precursory signal related to potential earthquake activity on the locked southern section of the San Andreas fault. Additional geologic and geochemical studies are underway to further our understanding of the relationships between geochemical signatures and local geology.
COMPUTER BASED GAS CHROMATOGRAPH CONTROL
AND DATA REDUCTION
J.D. Melvin, D. Masdea
A computer based gas chromatograph control system has been developed for field use in soil gas monitoring. The system controls Gulf built Hydrogen-Helium and hydrocarbon chromatographs through a light pipe interface with a bubble memory based microcomputer. All computer hardware is housed in a single video terminal. Electrical isolation and a minimal number of moving parts help to insure reliable operation in the field. The system includes interactive software for gas chromatograph scan acquisition, calibration, and peak analysis. Also provided are programmable control of chromatograph operation and graphical data display, interactive graphics which allow examination of scan data with more than two orders of magnitude magnification, storage of scans on cartridge tape, and scan reanalysis including addition and averaging of multiple scans. Complete printed graphical reports are generated. Work is in progress to allow modem transmission of data over voice telephone lines from the field to a central laboratory. The system can be expanded to control multiple chromatographs and carry out complex analysis.
CARBON MONOXIDE: A PROSPECTIVE GEOTHERMAL
INDICATOR
William C. Sidle
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA
15230
Regional soil gas investigations along the central part of the Utah Hingeline have measured anomalous seeps of carbon monoxide. These carbon monoxide microseeps averaging 210 ppm coincide with groundwater discharge areas along an arcuate geothermal zone. Typically, the interbasin groundwater flow is enhanced by cross cutting fracture zones, permitting artesian flow to be maintained. Relative high heat flow and active groundwater discharge combine to concentrate carbon monoxide levels in the overlying soils. Carbon monoxide anomalous sites appear to be associated with local "hot spots" and focus attention on prospective high permeability zones at depth.
SURFACE MONITORING OF RETORT GASES FROM
AN UNDERGROUND COAL GASIFICATION REACTOR: TIME DYNAMICS.
V.T. Jones
Gulf Research & Development Co., P.O. Drawer 2038, Pittsburgh, PA
15230
A near-surface soil-gas geochemical survey was conducted in conjunction with the Phase II underground coal gasification experiment at the North Knobs GR&DC-DOE UCG facility. Soil gases were measured in 122 eighteen ft deep permanent sites over an extended time period from July 1981 to July 1982. Baseline values were established one month before the 600 ft deep retort was pressured and fired. Monitoring of leakage gases continued daily throughout the three months during the burn and for one month after in order to follow the relaxation of surface leakage. A final monitoring was conducted six months after in July 1982. The final report contains 57 contour maps which illustrate the surface leakage patterns over four times windows for the following retort components: methane, ethane, propane, iso butane, normal butane, ethylene, propylene, and hydrogen.
SHALLOW-WATER CHEMISTRY ABOVE OIL AND
GAS FIELDS OF TIERRA DEL FUEGO
G.W. Zielinski, G.A. Cooke, Gulf Research & Development Co., P.O.
Drawer 2038, Pittsburgh, Pa 15230; and P. Bruchhausen, Lamont-Doherty
Geological Observatory, Palisades, NY 10964
Soil samples from depths less than 2 m were obtained as part of a thermal study of the oil and gas fields of Argentine Tierra del Fuego. Pore waters extracted from the samples were then analyzed for K, Mg, Ca, Na, Cl, SO4, NO3, and PO4. Results in the vicinity of the San Sebastian, La Sara, and San Luis Fields exhibit relatively high concentrations (up to several hundred ppm) of the cations and C1; however, with considerable variability. Crude sampling procedure of necessity may have affected the latter result. Regional samples along a 50 km line trending southwest from the San Luis Field, however, show a significant drop in concentration outside the hydrocarbon province. These observations could be the result of 1) discharge within the hydrocarbon province of waters from deeper in the Magellan Basin (this was one conclusion of the thermal study), 2) contamination of surface soils due to hydrocarbon production in the province or 3) an affect of increasing distance from the seacoast. Based on the geochemistry alone, it is difficult to reach an unequivocal conclusion.
A GEOCHEMICAL MODEL FOR THE DETECTION OF HYDROCARBON
LEAKAGE BY REMOTE SENSING
Martin D. Matthews
The detection of visible hydrocarbon leakage at the surface has been
one of the most successful exploration techniques ever utilized. Although
most areas with macroseepage have been explored by the drill, there exist
many areas with microseepage that have potential production. Remote sensing
data has been shown to offer the potential to delineate some of these
microseepage areas under the right conditions.
Examination of surface and subsurface data suggests that the passage of
hydrocarbons through rocks alters their geochemical equilibrium sufficiently
to change the inorganic composition of the rock. Given the appropriate
conditions, these changes may persist to the surface or be exposed by
subsequent erosion where they could be imaged by remote sensing data.
The observed and theoretical interactions of hydrocarbon leakage and surface
materials will be reviewed and integrated into a migration model. The
consequences of this model to detection of areas of hydrocarbon leakage
by spectral remote sensing techniques will be considered.
GEOBOTANICAL REMOTE SENSING - A CASE
STUDY OF PLANT/SOIL INTERACTION IN RESPONSE TO METHANE MICROSEEPAGE
B.N. Rock, Geobotany and Renewable Resources, Jet Propulsion Laboratory,
Pasadena, Ca 91109
During the summer of 1983, Gulf Research and Development conducted an extensive soil gas analysis at the NASA/Geosat Test Case Site at Lost River, WV. Results from this analysis have identified an order of magnitude methane and ethane soil gas anomaly precisely coincident with previously identified geobotanical anomalies at the site (anomalies noted on remote sensing images). A detailed discussion of root zone interactions with specific edaphic factors generated by methane microseepaqe will be presented. This discussion will provide a theoretical basis for interpretation of remotely sensed data sets acquired from heavily vegetated areas subjected to qeochemically-induced stress associated with hydrocarbon microseepage.
RECENT ADVANCES IN MULTISPECTRAL REMOTE
SENSING: APPLICATIONS TO GEOLOGY AND OIL AND GAS EXPLORATION.
H.R. Lang, Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA 91109
In the last year, multispectral remote sensing systems have become operational which provide significant new information for geological research and oil and gas exploration. These include both satellite (Landsat-4 Thematic Mapper, TM) and aircraft (Airborne Imaging Spectrometer, AIS, and Thermal Infrared Multispectral Scanner, TIMS) systems. In many cases these new data enable geologists to remotely identify and map the minerology of surface materials based on principles of visible short wavelength infrared (TM and AIS) and midinfrared (TIMS) spectroscopy. This talk will summarize these developments and provide examples of application of these new multispectral data to geologic mapping and oil and gas exploration in typical sedimentary basin environments.
THE SPECTRAL RESPONSE OF MINERALS
IN THE VISIBLE-NEAR INFRARED (400-2500 nm) REGION
William F. Buckingham
Gulf Research & Development Co., P.O. Box 37048, Houston, TX 77236
Electronic and vibrational transitions occurring in the visible near infrared (400-250 nm) spectral region produce unique reflectance spectral signatures for many rock forming constituents. Electronic transitions, including charge transfer and crystal field effects, have been utilized to identify transition metals, the crystal sites they occupy, and their oxidation state. This has been extended to the detection of rare earth elements in phosphate minerals. Vibrational absorptions which occur in the near infrared are due to combinations and overtones produced in hydroxyl and carbonate bearing minerals. The detection and identification of vibrational signatures has shown many clay minerals to have unique sets of spectral features. Several problems were encountered during attempts to interpret these data quantitatively. However, it was found that the concentration of alunite and kaolinite in synthetic samples could be determined to within 5 percent.
MERCURY AS A PATHFINDER FOR DEEP-SEATED ORE BODIES
V.T. Jones, Woodward Clyde Oceaneering, P.O. Box 430389, Houston, TX 77243,
J.B. Maciolek, Gulf Research & Development Co., P.O. Box 37048, Houston,
Tx 77236
Efficient and inexpensive methods for measuring free and occluded mercury in near surface soils have been developed. Occluded mercury gives excellent results as a pathfinder over gold and silver deposits, and appears to offer greater contrast between background and anomaly thresholds as compared to free or total mercury. The techniques developed are based on the precollection of mercury and utilize the property of gold to amalgamate mercury at relatively low temperatures. Adsorption of occluded mercury by gold takes place on the inside of gilded quartz vials at a fixed temperature in the range of 130ºC to 220ºC. Adsorption of mercury vapor from soil gas is achieved by flowing a predetermined aliquot of soil gas through a collector containing gold coated, purified quartz sand. Field tests determined the best time and temperature of amalgamation, the optimal depth of sampling, the reproducibility of the method and the effect of climatic variations on soil gas mercury content. Occluded mercury anomalies have been demonstrated to correlate reasonably well with free soil gas mercury, however, they are more repeatable and reproducible, and are not affected by climatic variations.
REMOTE SENSING AND SURFACE HYDROCARBON
LEAKAGE
M.D. Matthews, V.T. Jones, D.M. Richers
The geosat oil and gas test site program stimulated interest in the potential
interaction between surface hydrocarbon concentration and interpretation
of remote sensing data. The test case results suggested that lineaments
correspond to avenues of preferential hydrocarbon seepage and that this
seepage effects vegetation health and populations at Patrick Draw field
in Wyoming and potentially at Lost River field, West Virginia. These two
areas were selected for extensive surface hydrocarbon surveys in order
to test these hypotheses.
The Patrick Draw study shows that a zone of stressed vegetation, visible
on thematic mapper data, definitely coincides with an area of marked leakage
of hydrocarbons and that the composition of these gases would predict
an intermediate or oil and gas reservoir such as exists in the area. The
study further indicates that the leakage is in large part controlled by
the presence of fractures/faults recognized as lineaments on the remote
sensing images.
The Lost River study specifically investigated the inferred but unproven
existence of hydrocarbon leakage causing anomalous populations of maple
trees in a climax oak forest. The existence of these stands of maples
was first recognized by study of thematic mapper simulator data. The soil
gas hydrocarbon concentrations are above average in several of the maple
anomalies over the field. This supports the inference that the maples
are present because they are more tolerant of soil conditions where hydrocarbon
seepage is active. The crest of the field has low soil gas magnitudes
but high values occur to the updip eastern edge of the field along a fault/fracture
that was detected in the remote sensing data.
The conclusion that preferential pathways of hydrocarbon leakage can be recognized in spectral and textural analysis of remote sensing data will be supported by other studies and integrated into a suggested exploration/hydrocarbon migration model.
COMPARISON OF COMMONLY APPLIED SOIL-GAS TECHNIQUES
USED IN EVALUATING HYDROCARBON POTENTIAL
D.M. Richers, Gulf Research & Development Co., P.O. Box 37048, Houston,
TX 77236
A variety of commonly applied surface soil-gas techniques used in evaluating
an area's hydrocarbon potential are compared. These techniques include
a thermal-mechanical disaggregation technique, a commercial acid-extraction
technique (Horvitz), a shallow probe (4 ft.) free soil-gas technique,
and a deep (12 ft.) packer free soil-gas technique. Data collected from
a variety of areas with known or implied potential have been studied.
Results show that at least one to several of the methods applied correctly
identify the potential (i.e., oil, mixed oil-gas/condensate, or dry gas
prone) of the areas.
Recommendations that more than one method be applied in Frontier Areas
are presented.
ANALYTICAL METHODS AND PITFALLS
IN FLUORESCENCE ANALYSIS OF GEOCHEMICAL SAMPLES.
T. Whelan, C.S. Milan and F.C. Kuo, Woodward Clyde Oceaneering, 7330 Westview
Dr., Houston, TX 77055
Fluorescence spectroscopic analysis of geochemical samples has been used
with increasing frequency to provide information on the composition and
quantity of aromatic hydrocarbons in oils, source rocks and recent sediments.
In this paper we present analytical methods for optimizing fluorescence
measurements on recent sediments. Wet and dry extraction techniques are
compared with each other for quantitative and qualitative analysis. Specific
pitfalls are also discussed which can be traced to contamination and nonlinear
quenching effects.
Biogenic production and degradation of the aromatic fraction of petroleum
in sediments of South Louisiana is presented. A set of criteria is given
which will aid in the measurement and interpretation of fluorescence data.
SECOND DERIVATIVE ABSORPTION SPECTROSCOPIC
DETERMINATION OF BENZENE AND TOLUENE AT THE WELLSITE
Robert J. Pirkle, Gulf Research & Development Co. P.O. Box 37048,
Houston, TX 77236, Robert N. Hager, Hager Laboratories, Inc., P.O. Box
39228, Denver, CO, 80239, Victor T. Jones, Woodward Clyde Oceaneering,
P.O. Box 430389, Houston, TX
A Lear Siegler SM-400 derivative spectrometer was used to identify and quantify benzene and toluene in drilling returns in a well in the western United States. Excellent correlations were noted between these gases and all macro oil shows encountered, improving the geochemical recognition of potential oil producing zones. The largest benzene and toluene magnitude anomalies are coincident with the well's only current producing zone. Subsequent to these measurements, a new spectrometer was designed and built which is capable of simultaneous determination of benzene and toluene in wellsite applications.
THE INFLUENCE OF SOIL/SEDIMENT
pH OR MINERALOGY ON THE ADSORBED HYDROCARBON TECHNIQUE FOR GEOCHEMICAL
EXPLORATION FOR PETROLEUM
Van Price, Aiken, S.C., Ann Heatherington, Dept. of Geology, Washington
Univ., St. Louis, MO
The principal method practiced to release adsorbed or chemisorbed hydrocarbons
from soil or sediment samples involves acidification in the presence of
copper sulphate. Experience in a number of surveys indicates that the
method yields excellent results in some areas and equivocal results in
others. In our study, measurements of the incremental release of C1-C4
hydrocarbons with decreasing pH indicated a release threshold at about
4.5. Samples from three areas were titrated with acid and the evolved
gases and pH were monitored. Copper sulphate increased the amount of gas
released but did not alter the pH dependence.
The significance of these results lies in the possible inference that
natural pH's less than neutral may inhibit the sorption processes upon
which desorption prospecting relies. The converse may also be true...
positive results from particularly fecund samples may require cautious
interpretation. In either case knowledge of sample pH may lend insight
to data interpretation.
TYRONE-MT. UNION CROSS-STRIKE LINEAMENT
OF PENNSYLVANIA: A MAJOR PALEOZOIC BASEMENT FRACTURE AND UPLIFT BOUNDARY
Michael R. Rodgers and Thomas H. Anderson
The Tyrone-Mt. Union lineament of central Pennsylvania is one of many
lineaments recognized in the Appalachian Valley and ridge province. This
feature has been projected into the Plateau province where it defines
a cross-stride structural discontinuity. Geomorphic evidence of the lineament
is recorded in Mississippian and older rocks. Near-surface hydrocarbon
measurements, reservoir gas analysis, fracture measurements, borehole
surveys, and very low-frequency electromagnetic data indicate that these
lineaments are zones of increased fracture permeability with enhanced
hydrocarbon and fluid migration. In one gas field, wells drilled along
the lineament had significant gas shows in organic-rich Devonian shales.
Several Devonian through early Pennsylvanian formations are characterized
by facies and thickness variations across this lineament. These data consistently
suggest that the lineament marks the southern boundary of an uplift in
north-central Pennsylvania. This uplift boundary is recognized in northwestern
Pennsylvania in surface and subsurface data. Farther southeast, where
Allegheny deformation was stronger, this subtle boundary is obscured.
Analysis of subsurface data suggests that this uplift has affected fold
terminations and structural elevations in the vicinity of the lineament.
The structural and stratigraphic anomalies recognized in this study overlie
a crustal-block boundary. These trends may be explained by differential
subsidence of these crustal blocks.
HYDROCARBON CONTAMINATION IN THE
NEAR-SURFACE SOIL
Robert J. Pirkle and Richard J. Drozd
Near-surface hydrocarbons, C1-C4, have been measured around a leaking
production well, around a leaking storage cavern, over known crude oil
and diesel oil spills, and over a leaking pipeline. Aerial and depth profiles
of hydrocarbon magnitudes together with hydrocarbon composition in hydrocarbon
contamination in the near-surface.
Hydrocarbon magnitudes increase with depth around a leaking production
well whereas in areas of known crude oil spillage, magnitudes decreased
sharply with depth. The greatest evidence of well leakage was found in
close proximity to the casing in both the production and storage well
examples. Crude oil spills were characterized by C3 and C4 greater than
C2 or C1, due to loss of light ends during production. No light hydrocarbons
were associated with the diesel oil spill. Pipeline leaks are found to
agree well with composition of their products, but may extend to depths
well below that of the pipeline.
Characterization of these phenomena aid in the elimination of contamination
data from normal near-surface geochemical exploration survey data.
A GEOCHEMICAL RECONNAISSANCE OF
CRETACEOUS INLIERS IN NORTH-CENTRAL OREGON
William C. Sidle and David M. Richers
Cretaceous inliers in north-central Oregon represent isolated exposures
of potential source rocks in the region.
Interpreted neritic to upper bathyal mudstones of the Hudspeth Formation
represent late deposition within the Mesozoic forearc terrane. Accretionary
terranes that are represented by the Blue Mountain province are in part
inundated by voluminous Tertiary volcanic sequences, most notably the
Columbia River Group.
Both pyrolysis and solvent extraction source rock data from the Hudspeth
Formation present in local Cretaceous inliers support a mature, oil-prone,
mixed marine source rock environment. A trend reflected in this data indicates
that the western part of the study area is more mature. If these same
strata and conditions prevail beneath the volcanic cover, then the potential
for the presence of paraffinic oil accumulations exist.
Near-surface soil gas investigations have shown the occurrence of light
hydrocarbon microseep gases which cluster in the vicinity of the Mitchell
inlier. The soil-gas signal received in the near-surface, far removed
from the inliers, is identical to the soil gas signature measured on the
Cretaceous sediments. It is suggested that the application of reconnaissance
surface geochemical methods may offer additional insight in defining potentially
favorable source rocks peripheral to the Columbia river Plateau as well
as projecting their presence into the interior of the Plateau.
CARBON MONOXIDE AS A GEOTHERMAL INDICATOR
AT MEADOW-HATTON KGRA, WEST CENTRAL UTAH
W.C. Sidle
Carbon Monoxide (CO) was measured in soils over a Known Geothermal Resource Area (KGRA), located in west-central Utah. Attendant sampling of carbon dioxide (CO2) soil-gas was undertaken to compare with the spatial distribution of carbon monoxide anomalies. Anomalous CO data ranging up to 940 ppm are singularly grouped south of Devils Kitchen fault or rift in the vicinity of the KGRA. In contrast, the CO2 anomaly ranges up to 2.3 percent and is broader, forming a band extending northeastward in Pavant Valley. An active shallow groundwater regime apparently influences the upward migration of these gases into the soil horizon, resulting in sharply defined anomalies. It is suggested that CO is highlighting a local geothermal system with greater resolution than CO2 and should be more widely employed in geothermal investigations.
REMOTE SENSING AND SURFACE GEOCHEMICAL
STUDY OF RAILROAD VALLEY, NYE COUNTY, NEVADA
V.T. Jones and S.G. Burtell, Exploration Technologies, Inc.
R.A. Hodgson, Geological Consulting Services, 403 Liberty St., Jamestown,
PA 16134, USA
Tom Whelan and Charlie Milan, Woodward Clyde Oceaneering, 7330 Westview,
Houston, TX 77055, USA
Takeshi Ando, Kinya Okada, and Takashi Agatsuma, Japex Geoscience Institute,
Inc., Akasaka Twin Tower, 2-17-22, Akasaka, Minato-Ku, Tokyo 107, Japan
Osamu Takano, Earth Resources Satellite Data Analysis Center (ERS-DAC),
No. 39 Mon Bldg., 4-5 Azabudai, 2 Chome, Minato-Ku, Tokyo 106, Japan
A remote sensing and soil gas geochemical survey has been completed in
Railroad Valley, Nevada fot Japex Geoscience Institute, Inc., Tokyo Japan.
The initial survey was designed around an existing structural model published
by Foster and Dolly (1979). This study provides a test of this model with
remote sensing and geochemical information. Combined interpretation, using
SAR, TM and TM enhanced images has suggested a series of major fracture
lines which define regional fault and fracture systems. Many fracture
lines cross the valley graben and may reflect structural subdivisions
within the qraben blocks, some of these confirm structural divisions identified
by Foster and Dolly.
There appears to be a reasonable correlation between the mapped fracture
systems, the geochemical anomalies, and the existing oil fields, although
any one set of data alone does not delineate the fields. A comparison
of the geochemical data with the oil fields and remote sensing interpretations
shows good correlations with the presently identified fields. Light hydrocarbon
magnitude and compositional anomalies appear to reflect preferential migration
along certain fracture systems on the flanks of the valley updip from
the oil reservoirs. Although direct soil gas anomalies do not occur over
the reservoirs, valley boundary faults adjacent to the reservoirs do exhibit
a significant flux of hydrocarbons updip from all the presently known
accumulations.
SOIL MERCURY TRAVERSES ACROSS THE SAN ANDREAS FAULT IN SOUTHERN CALIFORNIA
Stephen G. Burtell, Exploration Technologies, Inc., 3911 Fondren, Houston,
TX
The adsorbed mercury content of surface soils has been measured along
10 traverses across the San Andreas Fault from the San Gorgonio Mountains
to Chalome in Southern California. The results of these analyses indicate
that anomalous mercury values are associated with the strike of the fault
in some areas which are not affected by seasonal sediment influx.
Samples collected from Pearlblossom to Juniper Hills do map a well-defined
anomaly which can be correlated with the fault and may indicate an area
of active gas migration from depth. Similar although less well defined
anomalies have also been identified in the San Bernadino Mountains and
near Chalome. A number of the traverses showed negative results which
could be due to recent sediment influxes or the absence of active mercury
localization and migration in these areas.
If anomalous soil mercury can be shown to correspond with active deep
fault gas migration, this inexpensive technique could be used as a guide
to the placement of future gas monitoring sites for earthquake prediction
studies.
CORRELATION OF SPATIAL AND COMPOSITIONAL
DISCRIMINATORS OF NORTH AMERICAN HYDROCARBON BASINS
M.D. Bray, Dept. of Mathematical Sciences, Rice University,
P.O. Box 1892, Houston, TX 77251 and V.T. Jones, Exploration Technologies
Inc.
The focus of this paper is to compare some of the published techniques used in compositional classifications to the method initiated by the current authors. The authors have previously presented findings that suggest a spatial and compositional correlation of hydrocarbon reservoirs in various basins. Clustering of the data based on chemical analyses, generally correlate with a similar set of spatial clusterings of proven producing wells. In order to define a more consistent set of boundary conditions for compositional classifications, mathematical means (i.e., frequency plots), based on compositional data will be investigated; published well data of various North American basins will be studied.
COMPOSITIONAL CORRELATIONS BETWEEN SUBSURFACE
WELLS AND MARINE GEOCHEMICAL DATA
V.T. Jones, Exploration Technologies, Inc., Houston, TX 77084. M. Bray
Previous publications (Jones & Drozd, AAPG Bull. 1983) and ACS presentations (Williams et al, 1981 and Pardensky, Drozd, and Jones 1981) have proposed the use of several methane through butane light hydrocarbon ratios and cross-plot schemes for identification of surface and marine hydrocarbon seeps. The marine crossplots presented by Williams et al were based on Gulf of Mexico well analysis data published by Rice et al in a USGS open file report. Further tests of this crossplot model are provided by additional plots of published U.S. Bureau of Mines gas analysis data. Examination of onshore Sacramento and San Joaquin Basin Wells proves the validity of the concept and suggests that considerable information concerning source rocks and potential migration pathways are contained within such plots, in addition to their value for predicting the types of hydrocarbon reservoirs associated with near-surface seepage anomalies.
THE 1983 LANDSAT SOIL-GAS GEOCHEMICAL
SURVEY OF PATRICK DRAW AREA, SWEETWATER COUNTY, WYOMING
D. M. Richers, V.T. Jones, M.D. Matthews, J. Maciolek, R.J. Pirkle, and
W.C. Sidle
The Geosat test site at Patrick Draw, Wyoming, was resampled during the
summer field season of 1983, to conduct a more detailed soil-gas survey
on and around the area's producing fields. The results of this study agree
with the 1980 Geosat assessment that the faults and fractures visible
as linear features on satellite and aircraft imagery provide paths for
active microseepage of hydrocarbons from depth to the near surface. This
association is particularly true near the earlier described "blighted
sage zone", where extensive resampling reveals a much wider area
of anomalously high free soil-gas values and fluorescence than was previously
reported.
Discriminant analysis suggests that the geochemical seepage signature
found over the fields differs statistically from that present for adjacent
areas of no known production. This observation was found to be true for
all three soil-gas techniques used in this study.
Anomaly patterns appear to be related to the type of soil-gas sample studied.
Data obtained from shallow free soil-gas samples reveal that direct anomalies,
controlled by faults and fractures, formed over production, whereas data
obtained from samples treated by acid-extraction or thermal/mechanical
disaggregation techniques exhibit magnitude lows over the producing areas.
Such patterns indicate halo features around the composite producing areas.
At present, this conflicting behavior cannot be explained.
GEOCHEMICAL APPLICATIONS AND REMOTE
SENSING ANALYSIS APPLIED TO FRONTIER AREAS
V.T. Jones, S.G. Burtell, R.A. Hodgson
Remote sensing and surface geochemical prospecting are excellent tools
for providing the initial evaluation of any frontier basin. Examples will
be shown that demonstrate the natural utility of surface geochemistry
to distinguish between potentially productive and non-productive basins
and as a method of predicting oil versus gas potential of productive reservoirs.
Remote sensing techniques greatly increase the cost effectiveness of geochemical
prospecting by highlighting areas most likely to have enhanced fracture
permeability to aid regional geochemical survey design. The proper application
of these two tools applied in concert provides a very cost-effective method
for a preliminary evaluation of the hydrocarbon potential of any frontier
basin.
Remote sensing techniques reveal linear, curvilinear, and tonal anomalies,
which when correlated with major geological features, provide useful exploration
information. However, it is important to note, that all basins have a
complex mixture of these remote sensing anomalies. For example, lineament
types: those that are traces of faults, and others that result from propagation
of basement fractures, such as domes and anticlines. Therefore, during
periods of uplift and erosion all the basement sets of lineaments can
become active simultaneously with respect to fluid and gas transmission.
In many cases mapped lineaments are a distracting element in interpreting
the geochemistry because of their general lack of systematic relationships
to petroleum reservoirs.
Applications covered in this paper will attempt to demonstrate the usefulness
of remote sensing and surface geochemical relationships in both productive
and non-productive basins. The importance of a subtle regional lineament
will be demonstrated in Railroad Valley, Nevada, along with the need for
detail studies using aerial photography and close-spaced geochemical sampling
(1000' centers). These detailed data are needed for proper exploration
evaluation to confirm and supplement regional results before any attempt
is made to generate drillable prospects.
A NEW METHOD FOR HELIUM ANALYSIS IN OFFSHORE SEDIMENTS
R. Hatton, L. Franklin, C. Milan, T. Whelan, Woodward-Clyde Oceaneering,
7330 Westview, Houston, TX 77055
Helium analysis in soil gas has been used as a complimentary geochemical technique for geothermal, uranium and hydrocarbon exploration for over 10 years. In this paper we report an analytical method which can be used at sea in near-surface marine sediments for sensitive and reproducible analysis of helium. This technique utilizes a helium leak detector (mass spectrometer) with the same inlet configuration described by the USGS. Samples of marine sediment are sealed in metal cans using specially prepared brine and an air headspace, heated at 60º for 16 hours and then shaken on a high speed mixer to partition helium out of the pore fluids and sediment matrix into the headspace. Subsamples are injected into the helium analyzer and compared to helium concentration in air. Values for helium in marine sediments range from 0 to 2 ppm. This indicates that some sediments contain less than sea water helium concentrations. Equilibration experiment onboard ship demonstrate that helium concentrations reach equilibrium after 16 hours. Helium determined prior to this period show erratic and low concentrations. After the equilibration period results are reproducible to within 5% with + sensitivities of 0.03 ppm relative to air. This method of helium + analysis has been used effectively to analyze over 5000 samples offshore. The results provide reproducible and meaningful information which compliments organic geochemical data and provide inorganic confirmation for the migration of thermally derived hydrocarbons in the surface ocean sediments.
DETECTION OF HYDROCARBON MICROSEEPS AND RELATED GEOBOTANICAL ANOMALIES
USING MULTI-DATE IMAGE SUBTRACTION, RAILROAD VALLEY, NEVADA
Dar A. Roberts, Remote Sensing Laboratory, Stanford University, Dept.
of Applied Earth Science, Stanford, CA and Robert D. Green, Molycorp Inc.,
Englewood, Colorado
Railroad Valley, Nye County, Nevada is a N.N.W. trending closed basin
70 miles long and 20 miles wide which shows substantial hydrocarbon microseepage.
The distribution of the dominant vegetation types is influenced by the
microseepage. A technique utilizing subtraction of two dates of registered,
atmospherically corrected imagery was developed to test the utility of
remote sensing as a means of locating vegetation growing on the microseeps
through phenological differences on and off the microseeps.
Plants are indirectly affected by the hydrocarbon microseepage. Hydrocarbons
are broken down by bacteria creating an acidic, reducing environment concentrating
heavy metals. This environment in turn controls to a limited extent, which
plants can grow over the microseeps and the vigor of these plants. The
results demonstrate that a multitemporal approach could be very useful
for mapping phenological anomalies associated with microseepaqe.
THE ROLE OF NATURAL FRACTURE SYSTEMS IN NEAR SURFACE GEOCHEMICAL PROSPECTING
Robert A. Hodgson, Geological Consulting Services, P.O. Box 531, Jamestown,
PA 16134
Experience shows that natural fracture systems can serve as avenues for
preferential transmission of diagnostic hydrocarbon and other gases from
depth into the near surface where they can be effectively sampled.
Knowledge of the nature of these fracture systems and their geometric
and genetic relations to hydrocarbon and other mineral environments of
accumulation can aid in planning and carrying out more effective and diagnostic
near surface geochemical surveys.
In this study the inherent pattern of fracture systems and the geometric
and structural hierarchies within fracture systems are outlined. An illustration
of the application of the results of mapping fracture systems to enhance
the interpretation of a near surface hydrocarbon survey is drawn from
a recent study in Railroad Valley, Nevada, USA.
REMOTE SENSING AND SURFACE GEOCHEMICAL
STUDY OF RAILROAD VALLEY, NYE COUNTY, NEVADA
V.T. Jones, and S.G. Burtell, Exploration Technologies Inc.
A remote sensing and soil gas geochemical survey has been completed in
railroad valley, Nevada for Japex Geoscience Institute, Inc., Tokyo, Japan.
The initial survey was designed around an existing structural model published
by Foster and Dolly (1979). This study provides a test of their model
via remote sensing and geochemical information. Combined information from
SARI TM and TM-enhanced images has suqgested a series of major fracture
lines which define regional fault and fracture systems.
A reasonable correlation exists between the mapped fracture systems and
geochemical anomalies and the existing oil fields, although any one data
set alone does not delineate the fields. Comparing the geochemical data
from the oil fields to the remote sensing interpretations yields a good
correlation with the presently identified fields. Light hydrocarbon magnitude
and compositional anomalies appear to reflect preferential migration along
certain fracture systems on the flanks of the valley updip from the oil
reservoirs.
SIGNIFICANCE OF RADON/HYDROCARBON SEEPS IN PETROLEUM EXPLORATION
Darioush T. Ghahreinani, TerraTech International, Inc., P.O. Box 22288,
Cleveland, Ohio 44122
Radon prospecting for hydrocarbon deposits provides an additional correlation
method which can be used with other geochemical surveys in order to support
the genetic association between soil gas hydrocarbon fingerprints at the
surface and bed rock sources at depth.
Results of an 800 site survey in northeastern Ohio indicated that sites
with anomalous radon activities in the soil-gas revealed higher values
for hydrocarbons and associated gases supporting the hypothesis of gas
leaking from depth. Gas components considered to be particularly significant
in this regard are the light hydrocarbons (C1-C4), H2, H2S, CO2, and He,
because the presence of high CH4 may be partly as a result of microbial
or chemical reactions in the soil or subsurface bed rock. This rapid radon
and hydrocarbon soil-gas detection technique is a unique and inexpensive
method of surface geochemical prospecting in basins with shallow black
shale deposits.
NEW CRITERIA FOR DISTINGUISHING ACTIVE MICROSEEPS FROM BACKGROUND
C.B. Glezen, Gulf Oil Co., P.O. Box 37048, Houston, TX 77236
A statistical comparison of soil-gas samples over production with samples
off production in eight geochemical surveys found as a general rule that:
1) large magnitude samples were twice as common over production, 2) large
alkane/alkene ratio samples were twice as common over production, and
3) large magnitude samples with large alkane/alkene ratios were six times
more common over production. A comparison of samples over fracture zones
with samples off fracture zones found even greater correlation.
Large alkane/alkene ratio samples had larger (oilier) C3/C1ratios over
gas-producing regions and smaller (gassier) C3/C1 ratios over gas-producing
regions than small alkane/alkene ratio samples. Thus the twin criteria
of magnitudes and alkane/alkene ratios can distinguish active microseeps
from background with two to three times more confidence than magnitudes
alone.
GEOCHEMICAL PROSPECTING OVER THE ROSE HILL OIL FIELD LEE COUNTY, VIRGINIA,
USING A SHALLOW PROBE TECHNIQUE
Robert J. Pirkle, Gulf Research & Development Co., P.O. Box 37048,
Houston, TX 77236; R.V. Brodine and Edgar S. Driver, Microseeps, Inc.,
P.O. Box 727, Indianapolis, PA 15051
Soil gases were recovered using a shallow probe technique over the Rose
Hill oil field in Lee County, Va. The gases were analyzed for light hydrocarbons,
C1-C4, plus hydrogen and helium using a custom built chromatograph.
Geochemical anomalies are interpreted in the context of 5 surface fracture
distributions and are found to correspond with regions of optimal production
from fractured reservoirs.
THE RATIONALE FOR SURFACE HEAT FLOW AS A SUPPLEMENT TO GEOCHEMICAL PROSPECTING
G.W. Zielinski, Department of Applied Science, Brookhaven National Laboratory,
Upton, NY 11973,
P.M. Bruchhausen, Omegalink International Limited, P.O. Box 66, Palisades,
NY 10964
A global correlation between known hydrocarbon production and high heat
flow can be explained by convective heat transport.
Recent theories on hydrocarbon migration and accumulation, in some aspects
analogous to hydrothermal mineralization processes, may also prove central
to the correlation. The ability of near surface measurements of relative
heat flow to detect heat transport by vertical fluid migration (with rates
as low as centimeters per year) can be shown theoretically and in the
field. Hence, for both operational and interoperational reasons, integrated
heat flow and geochemical data collection appears sensible and advantageous.
A GEOCHEMICAL METHOD FOR FINDING LEAKS
IN SUBMARINE PIPELINES
R.G. Aldridge and V.T. Jones.
A direct method of detecting leaks in submarine pipelines using established geochemical technology is discussed, including the theoretical basis and available equipment. An operational plan for location and pinpointing of a leak is outlined. This technology offers a superior solution for environmental monitoring for potential leakage, and a systematic means of locating the leaks that actually occur before any significant environmental damage is done.
SUBSURFACE DETECTION OF RETORT GASES
FROM AN UNDERGROUND COAL GASIFICATION REACTOR IN STEEPLY DIPPING BEDS
NEAR RAWLINS, WYOMING
V.T. Jones and H.W. Thune
A near surface soil gas geochemical survey was executed in conjunction
with the Phase II experiment at the North Knobs, Wyoming, GR&DC-DOE-UCG
facility from July 22, 1981, through December 12, 1981.
The soil gas detection method offers a unique new technique for locating
potential gas leakage areas before any significant migration avenues can
develop. This approach has the advantage over atmospheric measurements
because the soil gases are not greatly affected by winds and other varying
meteorological conditions; therefore a much lower level anomaly may be
resolved.
One hundred and twenty-two, 18 foot deep permanent sites, based upon the
local geology, were located and installed over the areas of both the previous
Phase I and the current Phase II retorts. All sites were routinely monitored
for methane, ethane, propane, iso-butane, n-butane, ethylene, propylene,
helium, hydrogen, carbon dioxide and carbon monoxide. Selected sites were
periodically monitored for carbon disulphide, carbon sulphide, hydrogen
sulphide and sulphur dioxide.
The survey demonstrates that residual gases from the Phase I burn are
still present in the near surface and product gases generated during the
Phase II burn were clearly evident. Maps are presented showing the areal
distribution of these products during: (1) the pre-burn, pre-pressure
period; (2) the air-pressured interval during system checkout; (3) the
ignition and early burn period; and (4) the late-burn and early post-burn
interval. These maps and the tabulated data indicate a recognizable surface
response occurred 3-6 days after changes in the burn retort pressures.
Product gases migrated into the near surface, both vertically and laterally,
along well developed cross-joints and near-strike joint sets within the
sandstones stratigraphically above the coal seam being burned. Additional
leakage is probably associated with poor cementing of the casing in some
of the deep boreholes. Casing leakage explains most of those anomalies
located in the rock sequence stratigraphically below the coal. While throughout
the survey, abnormally high values were found in the near surface at many
geochemical sites, ambient air samples routinely taken near those sites
consistently had mow values. It is concluded that a properly designed
and operated UCG facility would not experience any adverse product gas
leakage and would pose no hazard problems from either a safety or environmental
point of view.