If precious metals are not your forte, then try the petroleum industry. Exploration for oil and gas has always depended on surface maps of rock types and structures that point directly to, or at least hint at, subsurface conditions favorable to accumulating oil and gas. Thus, looking at surfaces from satellites is a practical, cost-effective way to produce appropriate maps. But verifying the presence of hydrocarbons below surface requires two essential steps: 1) doing geophysical surveys; and 2) drilling into the subsurface to actually detect and extract oil or gas or both. This Tutorial website sponsored by the Society of Exploration Geophysicists is a simplified summary of the basics of hydrocarbon exploration.
Oil and gas result from the decay of organisms - mostly marine plants (especially microscopic algae and similar free-floating vegetation) and small animals such as fish - that are buried in muds that convert to shale. Heating through burial and pressure from the overlying later sediments help in the process. (Coal forms from decay of buried plants that occur mainly in swamps and lagoons which are eventually buried by younger sediments.). The decaying liquids and gases from petroleum source beds, dominantly shales after muds convert to hard rock, migrate from their sources to become trapped in a variety of structural or stratigraphic conditions shown in this illustration:
The anticlinal trap, among the most common, is nicely revealed in a real world setting in this old photograph:
The oil and gas must migrate from deeper source beds into suitable reservoir rocks. These are usually porous sandstones, but limestones with solution cavities and even fractured igneous or metamorphic rocks can contain openings into which the petroleum products accumulate. An essential condition: the reservoir rocks must be surrounded (at least above) by impermeable (refers to minimal ability to allow flow through any openings - pores or fractures) rock, most commonly shales. The oil and gas, generally confined under some pressure, will escape to the surface - either naturally when the trap is intersected by downward moving erosional surfaces or by being penetrated by a drill. If pressure is high the oil and/or gas moves of its own accord to the surface but if pressure is initially low or drops over time, pumping is required.
Exploration for new petroleum sources begins with a search for surface manifestations of suitable traps (but many times these are hidden by burial and other factors govern the decision to explore). Mapping of surface conditions begins with reconnaissance, and if that indicates the presence of hydrocarbons, then detailed mapping begins. Originally, both of these maps required field work. Often, the mapping job became easier by using aerial photos.
After the mapping, much of the more intensive exploration depends on geophysical methods (principally, seismic) that can give 3-D constructions of subsurface structural and stratigraphic traps for the hydrocarbons. Then, the potential traps are sampled by exploratory drilling and their properties measured.
Remote sensing from satellites or aircraft strives to find one or more indicators of surface anomalies. This diagram sets the framework for the approach used; this is the so-called microseepage model, which leads to specific geochemical anomalies:
The surface geochemical expression of petroleum seepage can take many forms: (1) anomalous hydrocarbon concentrations in sediment, soil, water, and even atmosphere (2) microbiological anomalies and the formation of "paraffin dirt" (3) anomalous non-hydrocarbon gases such as helium and radon (4) mineralogical changes such as the formation of calcite, pyrite, uranium, elemental sulfur, and certain magnetic iron oxides and sulfides (5) clay mineral alterations (6) radiation anomalies (7) geothermal and hydrologic anomalies (8) bleaching of redbeds (9) geobotanical anomalies (10) altered acoustical, electrical, and magnetic properties of soils and sediments.
Landsat, and other space imaging systems, serve as mega-photos that depict large areas, within which clues to subsurface conditions may be evident. In general, most of the obvious structures that have surface expression had been discovered and mapped (to varying extents) over much of the world. Some regions, however, were not adequately mapped even in the 1970s, so that the advent of higher-resolution space imagery proved a boon to energy companies seeking new sources of fossil fuels. Sometimes the imagery proved especially sensitive to subtle indications of interior structures. For instance, fractures around structures in known oil/gas fields may extend further, as seen in the coherent space images, than suspected from ground work. Also, drainage patterns at broader scales may reflect control by underlying rocks involved in suitable traps. And even vegetation distribution may disclose signs of structure. These and other indicators discernible in space imagery appealed to exploration geologists as another means to survey large areas.
The two most useful indicators discernible in airborne or spacecraft remote sensors data are fracture systems (mainly lineaments) which can control or affect the migration of gas and oil to the surface and geochemical alterations of surficial rocks by hydrocarbons which lead to compositional and color changes. This second effect is reviewed on a website that deals with hydrocarbon detection.
We will now illustrate these ideas by examining and evaluating one of the first case studies using Landsat-1 to demonstrate the feasibility of direct exploration from space. This pilot study, conducted jointly by the Eason Oil Corp. and the Earth Satellite Corp. of Rockville, MD, sheds considerable light on effective criteria for recognizing conditions that might relate to buried hydrocarbons. In addition, some of the pitfalls associated with the space approach were also discovered by carefully assessing the results reported by these investigators.
The strategy behind the study was to look at Landsat imagery of a region already established as a petroleum province, giving special attention to telltale surface indications of the presence of known underlying fields. The investigators used standard-processed and computer-enhanced versions. Rather than test capabilities in a region where there is obvious structural control and other clear-cut evidence, they selected producing areas where the surface does not give clear indication of subsurface conditions. If they could succeed in detecting hydrocarbons under such difficult circumstances, then Landsat would increase in stature as an oil/gas discriminator .
The Anadarko Basin of south-central Oklahoma fits this requirement well. Located in the eastern Great Plains, with most of the land used for farming and ranching, the Basin is one of the great producers of the mid-continent petroleum province, which also includes much of Texas, as well.
The Basin is a down-sag in the crust that has allowed up to 15,200 m (50,000 ft) of Paleozoic sedimentary rock to accumulate. Structurally, the Basin is an asymmetrical geosyncline (a regional-scale downfold), with the deepest part near the south edge. Oil and gas are present in porous rocks associated with structural (anticlines; fault blocks) and stratigraphic traps. Large gas fields occur mainly along the Basin's western half, whereas oil is more common in the eastern half. Wells as deep as 7,600 m (25,000 ft) have recovered both hydrocarbons, although most pay zones are between 2,750-5,250 m (9,000-15,000 ft).
Generally, surface expression of underlying oil or gas traps in the Basin is meager, because first, there are few structural indicators in the flat-lying sediments atop older folded units and second,there is overprinting of geologic features by vegetation and land use (grasslands; hilly sage-covered terrain; and wheat farmlands). The Eason Oil/Earthsat investigators decided to focus on two search elements: previously undiscovered fractures and subtle chemical alterations of surface rocks by escaping hydrocarbons.
Lineaments analysis was conducted by Eason Oil using Landsat image transparencies backlighted on a light table. The linear features they picked are shown by lightweight black lines on the map below. Superposed as brown and green-black heavier lines are faults that had previously been discovered and mapped. As a geographic reference, note the meander bends (curved segments) of the Canadian River, traced in blue. The majority of the Landsat-mapped linear features are inconspicuous in the imagery. Many of them are suspect, i.e., they could be non-geological or some type of lighting artifacts.
As first mentioned in Section 2, a group of four geologists, including this writer (NMS), at Goddard Space Flight Center, decided to check on the reproducibility of these map results, using the same April, 1973 Landsat MSS full scene (see below). Each person used the same transparencies (mostly winter images) as Eason Oil and worked independently of one another to minimize bias. When done, we registered the tracings to a base map, on which the Eason Oil lineaments were also plotted, as seen below. The comparison disclosed rather startling discrepancies in terms of variance between the two groups. We found only about 20% of the total linear features in common. Eason Oil chose approximately 35% of the questionable features, exclusively, while Goddard geologists chose the remaining 45%, which represented those "missed" by Eason Oil. We immediately suspected that this kind of result is partially due to considerable subjectivity in deciding whether a given linear feature a) really exists, b) is geological in nature, and c) means anything.
This suspicion was reinforced by comparing the linear features selected by the four Goddard geologists. Here are the results - a mishmash that requires the following interpretation:
Of the 785 linear features identified by all four combined, only 4 (0.5%) were noted by every operator. From the remainder, 3 operators mutually selected 37 (4.7%), two operators agreed on 140 (17.8%), and the rest, 604 (77%), each operator found exclusively. This type of result has been reported in similar studies, although the above scores were particularly discouraging. Each geologist had ample experience in photointerpretation and special skills in analyzing Landsat imagery. Their choices were justifiable but overall, our results were questionable.
5-10: In this experiment, and in the technique of picking linear features in space imagery, what do you think was really going on behind the end result of some many linears being found but not consistently by multiple interpreters? ANSWER
The bottom line here is that there often is a strong tendency towards overkill in choosing features that appear to be meaningful lineaments. So many are drawn that it would take a monumental field effort to check them out. If plotted as rose diagrams (see page 2-9), they may reveal valid trends for the orientations of regional fractures, because statistically lineaments of non-geological nature should be in the minority. (A study of obvious lineaments in the Adirondacks confirmed this result.) Of the 200+ prominent ones in the Anadarko Basin that were field-checked, geological fractures directly or indirectly controlled most of them, but about 20% related to human factors, such as fence lines, roads, etc. Thus, we conclude that we should combine lineaments analysis with other indicators of mineralization or hydrocarbons. This combining would encourage geologists to field-check particular sites to verify the lineament presence and nature and their possible correlation with these indicators.
The Eason Oil study sought to recognize such indicators. Their interpreters delineated certain geomorphic anomalies, such as circular patterns and unusual drainage. In the course of their image appraisals, they noticed unexpected tonal patterns that looked a bit like light-colored smudges on the images, such as evident in the April, 1973 full Landsat MSS scene that became the reference base for the study. These they called "hazy" features, as seen here:
We labeled three typical hazy patterns A, B, and C. The one at A, at a bend in the Canadian River, is especially prominent, and occurs over a known oil field.
A standard false color subscene (computer-enhanced) around A shows the hazy to have a bluish-white color similar to soils in barren fields. Note the road pattern and white blotches which are accesses to producing wellheads. The yellowish areas coincide with unaltered Permian (late Paleozoic) red beds.
When we process this April Multispectral Scanner image into three ratio bands that we then combine into a color image (4/5 = Blue; 5/6 = Green; 7/5 = Red), the hazy feature at A takes on a unique yellow-green, and the red beds become orangish.
The signature for the hazy area, seen in darker orange-brown, is conspicuously different from its surroundings. It is associated with a small oil field that was developed after the Oil and Gas Map of the U.S. was published (see below). An aerial photo shows the roads that cross the hazy patch (inside the large meander loop of the Canadian River):
One might argue that the activities from the drilling had somehow lightened the whole immediate area, accounting for the "hazy". But, this is unlikely, especially since other hazies usually do not have active oil fields associated with them. The lighter tone is more likely to be a condition within the soil.From the multiseasonal data sets, only those scenes imaged in late winter to early spring show hazies. At other times of the year, vegetation masks the phenomenon. To understand their explanation of the features, we look now at this photograph of two rock types:
The rock on the far left is a sample from the red beds (sandstones) of Permian age. Next to it is the same material that has been color bleached to yellow-brown by converting iron oxide cement into hydrated iron oxides (analogous to rust). The gray rock on the far right is a limestone (calcium carbonate). To its left is a gypsum rock (hydrated calcium sulphate). Both interior rocks appear to be altered equivalents of the primary exterior rocks. In the field, comparable altered rocks can occupy many square miles.
To account for these hazy features, the Eason Oil people postulated that chemical reactions affected the iron cement, bleaching it out, and/or transformed the carbonates into sulphates. This, they surmise, happens when sulphur-laden gases or fluids leaked out of petroleum traps and rose towards the surface, interacted with susceptible rocks, and brought about compositional changes. Microseeps along lineament would be particularly effective.
About the time of their conclusion, evidence for such changes was reported as the Doctoral thesis of Terrence Donovan (later of the U.S.G.S.), in which escaping hydrocarbons drastically altered rocks above the Cement Field, at the southeast edge of the Anadarko Basin. Dr. Donovan found a pronounced set of anomalous values of the ratio of C13 to C12 in samples collected over both producing zones in the field, shown as contoured areas below:
These values represent some of the highest departures from normal ratios known anywhere in the world. He attributed them to the effects of chemical action by carbon-rich fluids on the rocks which, as a consequence, appear bleached. The Cement Field does not show any evident hazy-type anomaly in the imagery Eason Oil used. But an image processed by EarthSat did show a whitening about where the Cement Field is located, seen as a lighter tone near the center of the image (this is a winter scene, and a trace of snow is found around a reservoir to the northwest, but appears absent in the vicinity of the Cement Field).
Accepting this alteration hypothesis, the Eason Oil group looked for at least partial coincidence between these hazies and the surface projections of subsurface oil or gas fields. Of the 57 anomalies they mapped in a control segment of the imagery, they claimed an association with 42 producing fields. Another six occurred above or near non-producing structures, and only 9 showed no coincidence. If this observation remained true, then detecting hazies, sometimes correlative with lineament concentrations, could promise a powerful new way to hunt for oil and gas using space imagery.
The present writer (NMS), being skeptical in habit, decided to challenge these findings. The begging question: To what extent do the hazy anomalies correspond to known oil and gas field distributions. Here is a part of the Oil and Gas Map of the U.S. published by the American Association of Petroleum Geologists (AAPG):
On this map, the Cement Field is shown in a unique color - a purplish-brown. Next, here is the Eason Oil Map of the hazies shown in purple-blue:
It's hard to check the degree of correspondence by shifting between the two maps. So, I traced the outlines of the Eason Oil hazy features (in a hachured pattern) on a transparency and then overlaid and registered it to the oil (greens) and gas (reds) AAPG map of Oklahoma. The resulting combination is shown here:
Visually, the coincidence between hazies and fields does not appear strong. This was supported by a spatial correlation analysis, which demonstrated there is no statistical significance to the pattern distribution, i.e., the coincidence is random rather than associative. In practical terms, there would be at least as much chance of striking oil by drilling into points selected by throwing darts at the map, as there would be in drilling into the centers of hazies. (That is not facetious: I did drop the overlay randomly several times onto the AAPG map - a few hazies always landed on a few oil fields.) Based on a quick field trip to the A hazy, the writer (NMS) believes hazy features are areas where wind has blown away much of the soil fines, leaving reflective quartz grains behind. Of course, if escaping hydrocarbons affect the soil, that may be degraded enough to foster the wind removal.
However, at one locality designated as a hazy feature, the writer did find convincing evidence of what appears to be distinct color difference attributable to hydrocarbon alteration of red beds. In a dirt road, the reddish-orange of unaltered Permian rocks gives way to a yellow-white color representing hydrocarbon "bleaching" as proposed by EarthSat/Eason Oil. Here is a photo taken at that point:
The Goddard geologists under my direction didn't perform these studies to discredit the Eason Oil study, which provided some valuable insights into the discerning power of space imagery for petroleum exploration and the potential shortcomings of the apparent results. We did them to independently evaluate this approach and to inject caution into any beliefs that this technique might become a panacea for finding petroleum.
5-11: Critique the Eason Oil study, devising if appropriate a defense of their approach. In general, what do you believe to be the most effective use of remote sensing in exploring for hydrocarbons. ANSWER
Our bottom line: "The Jury is still out" on making positive claims about oil and gas exploration if based solely on the Eason Oil/EarthSat report.
At the time of the Anadarko study, several other investigators claimed to have found similar evidence that appeared to indicate that leaking oil and gas reservoirs could indeed be altering surface rock and soil. One that seemed to confirm this was the Beaver Creek Oil Field in the Wind River Basin of Wyoming. Dr. Robert Vincent presented this evidence, an MSS Band 5 (red) to 4 (green) ratio image in which a prominent oval shaped anomaly (shown here in tan) coincided very closely with the outline of the field as determined by subsurface drilling:
The writer (NMS) visited this field while engaged in his Wyoming investigation work. The area consisted of Lower Tertiary sedimentary rocks that were strongly dissected into gullies. Many of these beds were reddish and could in themselves account for some of the anomaly. A rather quick search for obvious signs of alteration by escaping gases or fluids failed to find any convincing evidence. But the remarkable co-incidence of the 5/4 anomaly with the outline of the Beaver Creek field suggest that this may be a valid example of the concept of alteration by petroleum compounds.
Landsat results in geological applications excited many in the petroleum and mining industries. Various companies banded together as a consortium, starting in 1976, in what became known as The Geosat Committee. Their avowed aims were along three lines: 1) to share information and conduct studies using space imagery to search for petroleum and minerals (mainly metallic ores); 2) to "lobby" NASA and Congress for a continuation and expansion of the Earth-Observing Satellite program; and 3) to provide inputs in determining and improving sensors in future satellites. One of their principal study sites was the Patrick Draw oil field near the Beaver Creek field in Wyoming. (see summary online at this website: Patrick Draw oil field). Hydrocarbons appear to be leaking as gases at various points above the oil field. This map shows the results of a field study (ground cored typically to depths of 3-4 m) that retrieved samples analyzed for propane:
When the Patrick Draw field was overflown by an airborne UV sensor, this map of fluorescence anomalies was constructed; these results seem to confirm detectability of hydrocarbon-related gases at or above surfaces where leakage of the gases occurs:
Two discoveries stemming from the Geosat study of Patrick Draw are significant: 1) a map of lineaments shows microseeps at several intersections, and 2) there is a distinct geobotanical anomaly in and near Patrick Draw - sage plants are damaged, presumably by escaping hydrocarbons, and this is detectable in hyperspectral imagery. Unfortunately, key illustrations supporting this have not been made public.
Earth Satellite Corp. (now renamed MDA Federal, Inc), and another group, Earth Search Sciences, have continued to validate data obtained from sensors on satellites and aircraft as potentially decisive indicators of subsurface oil/gas fields. This next diagram summarizes recent thinking:
Airborne hyperspectral sensors that were flown over known hydrocarbon leaks (in some settings, called microseeps) have found that an absorption feature near 2.31 µm (one of several in the near IR) is very sensitive to the amount of a specific component of the hydrocarbons. A ratio of two reflectance values on either side of that absorption feature divided by the value of the decreased reflectance in the spectral curve at the feature's low point enhances the detectability of the hydrocarbon and quantifies its magnitude.
This next image display shows an actual field case conducted jointly by the HJW GeoSpatial, Inc, the Geosat Committee and Earth Search Sciences in which an oil seep that corresponds to a specific pixel (red) in the Probe-1 hyperspectral scanner image shows the 2.31 µm diagnostic anomaly (strong absorption bands at 1.4 and 2.0 µm are related to other materials):
Leaks of oil from fields below the ocean can serve both as an exploration indicator and as a source of environmental damage. Prospecting for oil beneath the open ocean requires some different techniques as well as use of some of the conventional land methods. Oil seeps and slicks can remain intact on the surface and may be detectable in Vis/NIR and radar imagery. The Earth Satellite Corporation has developed SEP - the Seep Enhancement Algorithm - to bring out an oil signature using radar imagery. Here are two examples:
Oil slicks can be both natural or due to manmade oil spills. This EarthSat image shows a slick off the coast from Kuwait as rendered in a natural color Landsat image.
Specialized remote sensing can monitor another aspect of petroleum withdrawal not necessarily expressed as leaks. In time, as the oil is removed from pores leaving a partially filled void, the rock units bearing the oil start to contract or crush inward into the voids as support diminishes. This is commonly expressed by all the overlying units pushing downward on the now compressed reservoir rocks, giving rise to progressive surface subsidence. This lowering of elevation can be monitored by radar interferometry (see page 11-10 This next illustration, made from ESA radar data, shows interferometry rings, which can be computed into elevations, at the Lost Hills oil field in the San Joaquin Valley of California. The field is subsiding now at a rate of about 3 cm (1.2 inch) per month, with a cumulative drop since 1989 of 3 meters (10 ft). Subsidence is greater at the two ends of this 1.5 x 6 km (~1 x 4 miles) elongate field.
At the time of this writing (February, 2007) the intensity of the economic and political aspects of the availability and costs of oil and gas as still the principal energy sources for such multiple uses as transportation, heating, and plastics is at a "dangerously" high level. Prices are rising everywhere because of OPEC decisions, rapidly growing markets (e.g., China), and threats of cutting production (Iran's nuclear program). Alternate sources of energy, including oil in non-conventional modes of recovery, are being pushed. Two huge potential suppliers are Canada (tar sands) and Venezuela (heavy oil; requires pumping in hot water to release the oil from its host rock). Estimates of available oil from these types of deposits in Alberta, Canada approach, or may exceed, two trillion barrels (Venezuelan heavy oil is at least one trillion barrels).
The Canadian oil sands were first discovered in the late 1700s. The sand units outcrop at the surface in the northeast part of the province of Alberta but have a wider distribution subsurface, as seen in this map:.
The Cretaceous sandstones that contain sticky, near-solid bitumens (up to 20%) filling interstitial pores have been called Athabasca Tar Sands or now more commonly Alberta Oil Sands. Here is a surface photo of an outcrop rich in the blackish tar that pervades the rock.
As seen by the Space Shuttle astronauts in 1989, the area along the Athabasca River where surface stripping of the oil sands is active, is shown in the middle. The town of Fort McMurray, which has since grown considerably in anticipation of greatly increased production, appears to its south:
The oil sands after surface removal are further broken up and then extracted from the rock pores by subjecting the material to hot water and other chemicals. A barrel of thick oil requires processing of about a ton of the oil sand. Here is a processing plant where this is accomplished:
For decades the cost of obtaining liquid products from the sands for further refining had been too high to turn a profit. But that has now rapidly changed as prices of oil and gasoline in the U.S. and worldwide climb in response to demand. This has convinced various companies to set up greatly expanded operations. If stripping becomes impractical, the cost of subsurface mining must be weighed against expected increases in price and demand. In time recovery is likely to include underground mining. One plan is to confine stripping recovery to the summer months and go underground when the snow cover impedes surface mining. The reserves in Alberta are huge - comparable to that known in the Arabian Peninsula. There may be enough tar sands in Alberta to place Canada in "the driver's seat" in the 21st Century; for North America alone there could be sufficient oil sand reserves to last a century. As of 2009, the U.S. gets 22% of its oil (about 1.5 million barrels a day) from these Canadian deposits; China is becoming another major customer.The Canadian government is carefully monitoring and controlling the expansion of the oil sand industry. Waste at the surface, as seen below, must in a reasonable time be reworked to form a smooth surface and then replanted with trees and grass. Here is where space imagery will play a leading role - determining that the reclamation requirements are being met.
Among other uses of remote sensing for applications related to oil and gas exploration and production include: 1) monitoring pipeline location and possible breaks (leaks), 2) monitoring environmental damage from drilling for oil/gas, 3) monitoring recovery of the natural terrain after a field is no longer producing, and 4) producing land use/land cover maps of a region where new or increased development is anticipated.
An example of item 2 is offered by this photo taken from the International Space Station. It shows the barren ground patches around individual drilling sites and developed wells in the West Texas Permian Basin - a major producer in the U.S.:
Astronaut photography is occasional and target-selective. Environmental effects in areas immediately around drilling sites need more frequent monitoring. This SPOT-5 image shows multiple sites near Carthage in west Texas. There appears to be almost no adverse impact on areas surrounding the white scars that result from land cover clearing at each site.
This EO-1 satellite image also has environmental significance. It shows the markings saturating the hills of southern California's Coast ranges at the Elk Hills oil field, which first started producing in 1912 and is still active. It has yielded more than 1.3 billion barrels of oil and some natural gas. For many years it was the kingpin of the Naval Petroleum Reserve before being sold to Occidental Petroleum Co. in 1997.
Regarding item 4 - land use mapping of a developed or developing natural energy-rich region - is done in compliance with regulations for managing all of the resources. The writer (NMS) participated in a singular example of this requirement, which engendered an outcome of some notoreity. Here is the story:
Landsat-1 started to send back images in late July of 1972. The writer (NMS) was then a co-investigator with Dr. Robert S. Houston and Dr. Ronald Marrs of the Geology Dept., University of Wyoming (Laramie) in the NASA-funded Wyoming Geology program. I received the first images of Wyoming in mid-August and left at once for the field there. I spent a week roaming the state to check out what I could relate between image features and ground truth. Upon return to Laramie, Drs. Houston and Marrs and myself drove to the state capital, Cheyenne, to meet with state officials about possible uses of Landsat imagery in environmental and land use projects. A big one was in the offing - 8 million dollars to prepare land use maps of the Powder River Basin. That basin is one of the richest energy sources in all the U.S. - huge (and thick) deposits of coal, active uranium mining, and some oil and gas productions. The maps were needed within 3 years.
The state officials decided to gamble and earmark $60000 for the University of Wyoming to "try" to produce some preliminary maps using Landsat. The project began in September. On January 13, 1973 the faculty and students who worked on Landsat imagery presented a large (30 inches by 16 inches) folio with a series of maps - all patiently colored by hand using student help - that addressed several themes. Most important was the land use map, a portion of which is reproduced here:
The State was so impressed, it accepted these folio maps as adequate in meeting its multi-million dollar objectives. No further work was done.
A copy of the folio was soon sent to me. I too was impressed. I brought this copy down to the Earth Observations program office at NASA Headquarter for the managers to see. Their reaction was almost boisterous. This is just what they were looking for when they went to the U.S. Congress in just a few weeks to an Appropriations Committee hearing. The NASA chief, Dr. Len Jaffe, just commandeered (syn., confiscated) the folio and told its story to the congresspersons. (Never got the folio back; students had to color another one for me.) But a small price to pay to get the overall program in high gear.
Suffice to close this page with the remark that since the launch of ERTS-1, the petroleum industry has found new oil and gas fields with the aid of space data and has developed criteria from the images that continue to prove worthwhile in planning and conducting exploration programs, which are leading to payoffs. Most of the successes have come by using space imagery (as has been done before with aerial photography) in the tried-and-true (conventional) way of using the pictures as base maps on which to analyze and plot structural patterns and trends, often supplemented by recognition of stratigraphic units. (Detection of surface alteration, while it happens sometimes, remains a rather rare event.
In sum, remote sensing aids in exploration for oil and gas by 1) providing overviews of the regional geologic setting in which oil and gas is being sought; 2) helping to define existing fold/fault structures; 3) demarcating linear features that are usually fractures along which hydrocarbons migrate; 4) detecting alteration of rocks by escaping hydrocarbons; 5) finding other signatures indicated by fluorescent anomalies in the UV and compositional anomalies in the IR; 6) noting oil directly as leaks, spills, and seepage in the oceans/lakes or on land; and 7) observing environmental damage associated with drilling, pumping, pipeline transfer, and refining of hydrocarbons.