Earth surface hydrocarbon gas cloud detection by use of landsat data

A method of locating potential oil and gas reservoirs in the earth utilizing a satellite equipped to receive reflected solar energy from the earth at at least one selected frequency band, transmitting signals indicative of the received reflected energy to the earth, recording the received signals in a manner to provide a map of the earth's surface, filtering the received signals to provide signals representative of bands characterized by hydrocarbon gas absorption of the solar energy, and displaying the filtered signals, the area of hydrocarbon absorption being indicated by low intensity levels. The satellite system can be equipped with a coherent infrared irradiation system which scans the area of obsrvation, utilizing a selected infrared wave length beam to augment normal solar radiation at those wave lengths most effective for detecting the hydrocarbon gas cloud which appears above an oil or gas reservoir.

SUMMARY OF THE INVENTION 
The disclosure covers the use of infrared electromagnetic radiation to 
energize hydrocarbon gas molecules at their fundamental vibrational 
frequencies which causes the molecules to enter an excited vibrational 
state. This excited state is maintained momentarily, but sufficiently long 
to encounter other molecules such as oxygen or nitrogen, to which it 
transfers a discrete amount of its energy. Since the excited hydrocarbon 
gas molecule loses part of its energy when it drops back to the ground 
state, which occurs in a very short period of time, it re-radiates 
electromagnetic energy at a slightly longer wave length than the 
energizing infrared beam, resulting in a net loss of energy (absorption). 
It is the absorbed energy which is detected by a suitable detector and 
converted to an electrical signal or signals for visual display, or 
pictorial representation. 
Since the sun radiates at all frequencies and the atmosphere of the earth 
is transparent to the various fundamental frequencies which excite the 
hydrocarbon gas molecules, it is possible to detect the existence of 
hydrocarbon gas molecules which are excited by solar energy at the 
excitation wave length by the system disclosed in U.S. Pat. No. 4,490,613 
by this absorption phenomena. The pictorial representation or visual 
representation of the hydrocarbon gas anomaly is generated by electrical 
signals derived from the method which includes computer enhancement of the 
signal received so as to increase that portion of the signal represented 
by the selected "windows". Since solar energy can augment the pictorial or 
visual representation disclosed in U.S. Pat. No. 4,490,613, it follows 
that satellite or Landsat data can be analyzed in such a way as to 
visually or pictorially concentrate on those wave lengths represented by 
the five "windows" described in U.S. Pat. No. 4,490,613. This 
concentration or enhancement of specific portions of the broad band wave 
lengths detected by the satellite systems, i.e., the multispectral scanner 
system of the thematic mapper system is accomplished by a computer system 
which can screen the base satellite data in multiples or submultiples of 
the specific hydrocarbon gas molecules fundamental vibrational frequencies 
as described in lines 12 through 68 of column 6 and lines 1 through 19 of 
column 7 of the above patent. 
By computer enhancement of the data as described above, it is possible to 
pictorially or visually represent those areas on the earth which exhibit 
hydrocarbon gas microseeps, for oil and gas exploration purposes. 
To further improve the ability of the satellite system to gather data 
useful for soil and gas exploration purposes, a system is designed to 
direct a beam of coherent radiation from the satellite to the earth such 
that the path scanned by the satellite is at the same time irradiated by a 
selected wave length of infrared radiation as described by U.S. Pat. No. 
4,490,613 to increase and augment the absorption of molecular vibrational 
energy by the hydrocarbon gas molecules to increase visability of 
hydrocarbon gas microseeps for oil and gas exploration purposes. 
The technique developed also has the unique capability to reveal subsurface 
micro-drainage patterns related to original deposition of the oil or gas 
and, therefore, would be useful for well siting and petroleum production 
purposes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring first to FIG. 1 the earth is indicated by the numeral 10 and 
receives solar energy 12. A significant portion of this solar energy is 
reflected from the earth as reflected solar energy number 14. A small 
portion of the energy emanating from the earth is thermal energy 16. 
Reflected energy is received by a satellite 18 which preferably travels in 
an evolving circular or elliptical pattern in which the earth slowly moves 
relative to the pattern whereby the satellite 18 periodically appears 
directly overhead of all portions of the earth. The satellite 18 may be 
typically the presently employed Landsat thematic mapper satellite which 
receives signals in various bands. The satellite preferably has the 
capability to direct a coherent beam 19 of infrared electromagnetic energy 
at a selected wave length which scans the same earth area viewed by the 
satellite. The reflected signals are recorded in the satellite and are 
periodically retransmitted as signals 20 to an earth receiving station 22 
where thereafter the signals are thoroughly processed, including the use 
of computer enhancement. The processed signals are typically stored 
separately in several different bands thereby providing a plurality of 
bands representing each geographical area of the earth. These signals are 
filtered and processed and can then be transformed by video into black and 
white images 24 or into color images 26. The signals are typically stored 
on a plurality of magnetic tapes. 
As shown in FIG. 2, the magnetic tapes are stored in a tape bank 30 thereby 
providing tapes for mapped geographical areas in separately available band 
widths. 
By the process of this invention, and as will be described in more detail 
subsequently, when a particular geographical area is to be investigated 
for indications of potential deposits of oil and gas hydrocarbons, 
selected tapes 28A, 28B and 28C are taken from the magnetic tape bank 30. 
Tapes are individually processed in a computer processing unit 32 as 
controlled by central process unit control console 34. From the computer 
processing unit 32 signals are conveyed to video monitors and printers 
indicated by a false color monitor 36, an isometric profile monitor 38, a 
color printer 40 and a standard brightness/darkness scope 41. The monitors 
36 and 38 in printer 40 are emblematic of different types of monitors and 
printers which may be employed. The color printer 40 functions to make a 
record on paper of that scene displayed on one of the monitors for 
permanent record purposes. The scope 41 serves as a standard 
brightness/darkness reference which is used to adjust the monitor for 
quantification of data, and to insure consistency. 
The Landsat thematic mapper provides data in seven different wave length 
bands, i.e., band 1 from 0.45 to 0.52 micrometers, band 2 from 0.52 to 
0.60 micrometers, band 3 from 0.63 to 0.69 micrometers, band 4 from 0.76 
to 0.90 micrometers, band 5 from 1.55 to 1.75 micrometers, band 7 from 
2.08 to 2.35 micrometers and band 6 from 10.3 to 12.5 micrometers. The 
above bands extend from visual to thermal emission and are utilized for 
various science activities, i.e., world wide crop estimates, blight 
detection, polution detection, geological studies, detection of mineral 
deposits, oil and gas reservoirs, etc. Previously, satellite data has been 
utilized to derive oil potential of an area from implied subsurface 
structural determinations and tonal anomalies. 
Earth structural features are derived from satellite data indicating 
evidence of faulting, folding, fractures, lineaments, uplifts, basins and 
drainage patterns all of which contribute to detection of areas favorable 
for oil and gas accumulation and trapping. Tonal anomalies are interpreted 
to be surface mineral, soil and vegetation modifications caused by 
microgas seeps over a period of time and are detectable from the satellite 
data. Tonal anomalies can be a fossilized remnant of those mineral 
modifications. 
All of the above satellite features provide clues as to where oil and gas 
might be found, but does not provide direct evidence as to whether oil 
and/or gas may be trapped in commercial quantities. The following 
describes a procedure which can be utilized to provide direct satellite 
data evidence that oil and/or gas has been trapped, and, in addition, the 
data can be quantized for comparison with known oil and gas deposits. 
The technique depends on the well known and documented vertical migration 
of hydrocarbon gases from deep seated oil and gas reservoirs to the 
surface of the earth where venting occurs. The hydrocarbon gas microseep 
detection survey which samples and measures those hydrocarbon gases found 
at three foot depth has been very successful at locating and pinpointing 
oil and gas reservoirs. This system is covered by U.S. Pat. No. 4,310,057 
and confirms the hydrocarbon gas vertical migration theory. 
U.S. Pat. No. 4,490,613, previously referenced, describes a method for 
directly detecting the hydrocarbon gas cloud adjacent to the earth above 
oil and gas reservoirs by means of irradiation of potential areas with 
selected coherent wave lengths of infrared radiation which energizes the 
hydrocarbon gas molecules at their fundamental frequencies into a higher 
energy state whereupon the molecules drop back to an energy ground state 
and at the same time release electromagnetic energy at a slightly longer 
wave length than the energizing wave length thereby permitting detection 
of the re-radiated energy by proper use of filters and electronic imaging 
devices. 
The above patent also covers five specific "windows" A, B, C, D, and E, 
which are narrow regions in the electromagnetic spectrum where the 
fundamental frequencies of the hydrocarbon gas molecules of interest group 
together, which permits amplification of detection at the window wave 
length, whether detection is by means of re-radiation or absorption 
phenomena. Detection of the hydrocarbon gas cloud can be accomplished 
utilizing any one of the five windows cited by means of the techniques 
herein described. 
The windows also permit detection of various groups of hydrocarbon gas 
molecules together. For example, window A includes methane, ethane, 
propane and butane in fairly equal amounts, whereas window B is largely 
ethane and propane, window C is largely propane and windows D and E 
entirely propane. By viewing the earth at the various window frequencies, 
a judgment can be made as to whether the area is trending toward oil or 
gas. 
All of the above frequency data is derived from the National Bureau of 
Standards Publication NSRDS-NBS-39 "Tables of Molecular Vibrational 
Frequencies", Consolidated Volume I. This same document is incorporated 
herein by reference as a part of this disclosure. 
In order to utilize satellite data to detect the hydrocarbon gas cloud at 
the surface of the earth certain conversions must be made: Hydrocarbon 
gases, as all materials do, have fundamental vibrational frequencies or 
wave lengths characteristic of each type molecule. These fundamental 
frequencies have been converted to the equivalent wave length for ease of 
mathematical manipulation. The five windows above describe where the 
fundamental frequencies group together and provide the best opportunity 
for detecting the hydrocarbon gas cloud at the surface of the earth. 
The Landsat thematic mapper views the earth largely by reflected solar 
radiation along with some thermal radiation in the longer wavelengths. To 
detect the hydrocarbon gas cloud at the surface by means of the satellite 
data, the molecular vibrational fundamental frequencies have been 
mathematically converted from vibration to wave length. It was determined 
that initially windows A and B central wave lengths would be the target 
for mathematical conversion. Conversion is necessary since the earth is 
viewed by the satellite in band 7 at 2.08 to 2.35 micrometer wave lengths 
and band 6 at 10.3 to 12.5 micrometer wave lengths. Conversion can be 
accomplished by use of certain specific ratios, percentages or factors. 
Use of percentages is hereby described. To view the earth at the window A 
central wave length it was mathematically determined that 41.2% of band 6 
would be combined with 58.8% of band 7 to provide a composite wave length 
of about 3.39 micrometers which is about the center of window A. 
Absorption of incident solar radiation was expected at the above wave 
lengths by the hydrocarbon gas cloud when and if present at the earth 
surface. 
To view the earth at window B central wave length, portion of band 6 and a 
portion of band 7 are similarly combined to provide a combined frequency 
of 4.61 micrometer wave length, which is the central wave length for 
window B. The method of devising the proportions needed from each band to 
achieve an effective wave length signal will be described subsequently. It 
is emphasized that conversion can also be accomplished by the ratio method 
or factor method. 
Satellite data at a composite wave length of 3.39 micrometers and 4.61 
micrometers (windows A and B) was used to study an oil producing of Cook 
County, Tex. When viewed on both the color monitor and isometric monitor, 
definite radiation absorption at the windows selected (both windows A and 
B) indicates the presence of hydrocarbon gas clouds in the areas where oil 
and gas production is known to exist. Absorption was displayed on the 
color monitor as a dark area, which outlined the known oil pools for the 
area observed. This effect had never been previously observed by the 
normal way of viewing the satellite data. The isometric monitor confirmed 
the absorption of incident solar radiation by display of a depressed (low 
energy) area exactly conforming to the dark area on the color monitor. 
Field tests confirmed the presence of hydrocarbon gases. 
In addition to the above absorption areas a new effect referred to as 
microdrainage patterns was vividly displayed at certain color intensity 
adjustments. This microdrainage effect has never been previously observed 
by satellite data analysis. The potential use for the microdrainage 
pattern is employment as an aid for well site selection, since the 
patterns were definitely subsurface and not related to any surface 
feature. The patterns are believed to be indicative of oil/gas deposition 
patterns. 
In addition to identification of the areas of occurrence of hydrocarbon gas 
clouds, quantification of the hydrocarbon gas could can be practiced 
similar to the procedure outlined in U.S. Pat. No. 4,490,613 but modified 
to include the satellite data hydrocarbon gas cloud detection procedure. 
For this purpose a standard brightness or darkness patch is used to 
provide the capability to adjust the monitor brightness to a repeatable 
standard value both for repeatability and comparison of undrilled areas to 
known oil/gas production. The standard brightness/darkness patch can be 
incorporated into the color monitor or can be established as a separate 
fixed brightness scope. 
A quantification procedure begins with the display of the area to be 
quantified on the color monitor which is adjusted to the standard 
brightness of the patch or scope. This scene is then stored in a computer 
memory bank. The scene is a display of window A made up of 41.2% of band 6 
and 58.8% of band 7. The composite signal for window A is then removed 
from the monitor. This may be done by removing the instruction to view 
58.8% of band 7 from the composite leaving only the 41.2% of band 6 
displayed, to drop out the hydrocarbon gas cloud display. This scene is 
then recorded in a memory bank. 
The above procedure is then reversed by again displaying the composite 
window A scene. This time the instruction to view 41.2% of band 6 is 
removed leaving 58.8% of band 7 on the monitor. The hydrocarbon gas cloud 
drops out of the displayed scene. This scene is then recorded in the 
memory bank. 
The window A composite with hydrocarbon gas cloud is again displayed and 
adjusted to the standard brightness value. A TOPO map or oil map of the 
area of interest is positioned on the screen such that the TOPO map or oil 
map exactly matches up with the satellite data scene. The stored memory 
data for 41.2% of band 6 is subtracted from the composite scene. Then the 
stored memory data for 58.8% of band 7 is subtracted from the composite 
scene. These steps will leave the dark hydrocarbon gas cloud imposed on 
the TOPO map at the proper location. A print of the gas cloud data scene 
is then made for record purposes. 
A step neutral density filter (black to white) is then utilized to contour 
areas of the hydrocarbon gas cloud of like density. The contour lines are 
numbered in accordance with numbers established for each step of the 
neutral density filter. This procedure can be accomplished manually or by 
means of an X-Y plotter. This exercise is first accomplished for known oil 
or gas production within the area of interest to provide a reference. The 
undrilled hydrocarbon gas anomaly is then contoured. 
An alternate way to quantify the hydrocarbon gas cloud is to assign a false 
color to each degree of absorption utilizing a step neutral density filter 
as a guide for assignment of colors on the color monitor. Red can be used 
to denote the darkest shade (greatest absorption), orange (next lighter 
degree of absorption), yellow (third lightest degree of absorption), green 
(fourth lightest degree of absorption), and blue (fifth lightest degree of 
absorption). Actual hydrocarbon gas concentration values can be assigned 
by hydrocarbon gas sampling field tests for the area of interest. 
To obtain direct comparison with known oil/gas producing areas in the same 
region the same procedure is followed to calibrate and render a judgment 
or to high grade undrilled areas. 
The entire above, on shore, hydrocarbon gas detection procedure derived 
from satellite data can also be applied to lake, sea or ocean areas. The 
hydrocarbon gas emissions are known to occur off shore as well as on 
shore. Some adjustments are required for ocean depth, current direction 
and velocity which data is available from Bathymetric maps. Some 
adjustments for wave length band percentages or factors are normally 
necessary because of differences in land vs water temperature/absorption 
values. Wind is also a factor for oceanic areas, however, these necessary 
adjustments can be quantified for specific oceanic environments. For this 
disclosure the factor method will be used. The current method used for 
detecting hydrocarbon gas microseeps offshore is now described. 
Hydrocarbon gas microseeps occur off-shore as well as on-shore and can be 
detected by the system and methods of this invention. The present practice 
uses a water intake device towed behind a boat at a set depth and water 
samples are pumped aboard at a set rate. The hydrocarbon gas is extracted 
from the water sample and measured for species and concentration in the 
same way samples are measured onshore. The boat is equipped with precision 
navigation equipment to record the position of the water intake device at 
all times. Certain corrections are made for current direction and velocity 
and water depth. Gas chromatograph equipment is a part of the on board 
laboratory for gas concentration measurement purposes. This technique is 
currently used for off-shore hydrocarbon gas surveys and is very 
effective, but is slow and expensive. A far more efficient and cost 
effective method is to apply the principles as above described for 
on-shore satellite hydrocarbon gas cloud detection to off-shore surveys. 
This can be done utilizing the same techniques described in paragraphs 
above or by means of a slight modification of those techniques. The 
following is a description of the use of band 2 (green reflectance band) 
of TM data together with bands 6 and 7 for off-shore hydrocarbon gas cloud 
detection and mapping. Three bands of tape were selected from the Landsat 
data bank covering the area of interest. The procedure requires one 
visible band which can be band 2 or 3 or even a combination of bands 2 and 
3 ratioed to provide maximum topographic visibility in combination with 
band 7 which contain data from 2.08 micrometers to 2.35 micrometers plus 
band 6 which contains data from 10.3 micrometers to 12.5 micrometers. Band 
2 is the green reflectance band from 0.52 micrometers to 0.60 micrometers 
and band 3 is the red reflectance band from 0.63 micrometers to 0.69 
micrometers. Band 2 in combination with bands 6 and 7 will be used in this 
example, for the reason that the green band penetrates water to a greater 
degree than other bands and for that reason is more useful for offshore 
mapping of hydrocarbon gas anomalies. The first operation is to direct the 
computer to store in the disc pack memory the complete raw data from the 
magnetic tapes of bands 2, 6, and 7. The magnetic tapes were derived from 
the master tapes which recorded data direct from Landsat or Seasat. The 
data is actually a magnetic intensity reading ranging as an example from 0 
to 150 depending upon the intensity of the original signal from each 
individual sensor (Pixel) generated at the time the satellite was viewing 
the earth. 
A histogram for each pixel is created which provides an intensity value 
from 0 to 150 maximum range for the raw data. To improve resolution this 
range is increased to 0 to 256 on a log ratio basis electronically by 
computer. At this point in time the histogram is examined for quality and 
necessary adjustments are made, including adjustments to compensate for 
degradation of raw data quality due to factors such as sun angle, cloud 
cover, snow cover, moisture, conditions of vegetation, weather, etc. 
After quality adjustments have been made, a level of grey is assigned to 
each intensity level from 0 to 256 on a basis which matches the intensity 
level. A remap routine is then initiated which requires skewing of pixel 
geometry to obtain a flat picture of the earth. This operation sharpens 
and squares the edges of each individual pixel. 
At this point bands 6 and 7 are factored in such a way as to shift the 
center of satellite data band to the center of the window selected for 
detecting the hydrocarbon gas microseepage. This discourse utilizes window 
A centered at 3.39 micrometers. Since band 2 is centered at 0.65 
micrometers a multiplication factor of 6.054 is used to obtain 3.39 
micrometers which is the center of Window A. Since band 7 is centered at 
2.215 micrometers, a multiplication factor of 1.53 is used to obtain 3.39 
micrometers. Since band 6 centers at 11.4 micrometers, a multiplication 
factor of 0.297 is used to obtain 3.39 micrometers which is the center of 
window A. Other techniques such as use of percentages for each band or 
ratioing the bands can also be used as previously described. 
Band 2 (green band) is now programmed to be viewed on the RGB (color) 
monitor. This visible band displays various topographic features such as 
creeks, ponds, roads islands, etc. At this point band 2 is taken through 
an electronic color generator which is equivalent to a color wheel. 
Starting at a "0" value for grey at any selected point on the color wheel 
colors are assigned corresponding to the various values of grey from 0 to 
256 in a progressive manner. Color hue and contrast intensity can also be 
assigned at this time. 
At this point a false color image can be viewed on the screen. The next 
step is to rotate and fit the image or oil map to assure that the tape 
image matches the known mapped area. To do this, an X-Y system is used. 
The total picture consists of 512 lines of 512 pixels to each line, 
therefore the pixel number and line number can locate any point on the 
entire picture. To match the map with the tape image the operator selects 
a known point on the map and determines the line pixel number which is 
digitized and transferred to the screen and becomes a control point. About 
fifty control points are selected for each scene. The operator sets the 
cursor to each control point and records the line/pixel number. These are 
recorded in the memory and provide the basis for maintaining position. The 
computer warps the image so that the control points match the image. The 
operator then runs the scene through a statistical test and compares for 
correlation. Corrections, if needed, can be made at this time. 
After completing the map-matching operation the band 2, 6 and 7 data 
mathmatically converted to view the window selected is retrieved from the 
disc-packs, and projected onto the screen into the matched position. From 
this point on data can then be analyzed. With this graphics package, 
lineaments and anomalies can be traced and recorded in a memory separate 
from the Landsat theme. Adjustments to enhance the hydrocarbon gas 
microseep cloud for visibility are then made. The cloud normally appears 
as a dark patch due to energy absorption; however, adjustments can be made 
to cause the cloud to be bright or in color. Also, to test which band 
multiplication factors or ratios are best, the intensity value for ratios 
or factors on a scale of 0 to 100 can be scanned for band 2, band 6, and 
band 7 to visually determine which ratio or factor in practice actually 
proves most effective for display of the hydrocarbon gas cloud. The same 
procedure can be used to view any window from any band combination, to 
achieve the specific exploration objective. 
When the best and most effective RGB monitor display of the hydrocarbon gas 
cloud is achieved, the same scene is viewed on the isometric green screen 
monitor. The hydrocarbon gas cloud shows up as a low area on the isometric 
monitor indicating low energy, therefore, absorption has occurred. This 
low area corresponds to the dark area on the RGB monitor and serves to 
confirm the presence of electromagnetic wave absorption by hydrocarbon 
gases. 
It is known that the best petroleum producing areas generally exhibit high 
emissions of hydrocarbon gases, therefore, the capability to quantize the 
hydrocarbon gas cloud as previously described is a very useful exploration 
tool. An alternate quantization method is now described. 
To quantize an anomaly, a known oil or gas producing field in the area of 
interest is selected. A scale for the hydrocarbon gas cloud is then 
established. Any scale can be used, however, it is convenient to use 100 
as the quantity for the highest absorption exhibited by the known 
production with 0 established for no absorption. The gradient scale 
selected can be 5 or 10 depending upon conditions for the particular area. 
For example, 10 can be used as a scale to indicate the absorption 
exhibited by the reference pool. Thus, 110 would indicate 10% above the 
maximum absorption exhibited by the reference pool. In this manner the 
undrilled anomalies can be quantitatively compared with each other and 
with the reference pool. The standard brightness/darkness patch or monitor 
plus the neutral density filter are used for establishing the exact number 
to be used for controlling the gradient selected. 
The capability of transfering the quantized hydrocarbon gas cloud anomaly 
directed to an uncluttered topographic map is an excellent tool for making 
management decisions such as acquisition of acreage, release of acreage, 
drilling program planning and many others. In order to transfer the 
quantized hydrocarbon gas cloud anomaly, all background data contained in 
the Landsat tape is subtracted from the system described above, leaving 
only the quantized hydrocarbon gas cloud which is then rotated onto a 
previously prepared map of the area. Control points are checked for 
alignment, adjustments are made and then the combined scene, map plus 
quantized hydrocarbon gas cloud, is transferred to a photograph by the 
normal photographic transfer process utilized to obtain a photo copy of 
the scene depicted by the RGB monitor. 
An unexpected advantage of the system of this invention is that of being 
able to locate microdrainage areas in the earth. In order to be able to 
discern micro weathering and drainage patterns utilized, the same 
harmonies can be used as with detection of surface hydrocarbon gases. With 
the adjustment of the hue on the RGB monitor so that the low value 
readings appear a dark brown to a dark golden brown it is possible to 
identify very small and subtle drainage anomalies which are not detectable 
with normal false-color imagry. The intensity of the image should be 
brought up to a high to medium contrast for this purpose. 
The potential significance in this discovery lies in the fields of soil 
conservation, agronomy, and geologic exploration. Many buried geologic 
structures have extremely subtle surface drainage and weathering patterns 
associated with them. Thus, this discovery may be useful in siting oil and 
gas exploratory wells and in mineral exploration. It may also be used to 
explain subtle soil variation within a limited area. 
While the invention has been described with a certain degree of 
particularity it is manifest that many changes may be made in the details 
of construction and the arrangement of components without departing from 
the spirit and scope of this disclosure. It is understood that the 
invention is not limited to the embodiments set forth herein for purposes 
of exemplification, but is to be limited only by the scope of the attached 
claim or claims, including the full range of equivalency to which each 
element thereof is entitled.