Correlation of Color Infrared Anomalies to the Thomsen and Avon Oil Fields, Coffey County, KS

ES771 Class Project, Emporia State University, Spring 2009

by: John Gillenwater, April 2009



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Project Introduction

Satellite and aerial images have been used for many years as a screening tool for oil and gas exploration. Historically, these images have been used for identifying anomalous surface features which could indicate structural traps for hydrocarbons. However, with the continuing improvements in both satellite imagery and aerial photography, other "indirect" indicators of possible oil and gas fields can also be identified. One indirect indicator is a vegetative anomaly caused by alterations in the surface soils caused by hydrocarbon microseepage.

The purpose of this project is to review two color infrared data sets from both 1981 and 2006 and their correlation to the Thomsen and Avon Pools in Coffey County, KS. The Thomsen and Avon pools were chosen because both fields are Ordovician structural traps though the Thomsen is approximately eight times larger in terms of reserves and productive acreage.

Color infrared images were chosen because anomalies were present in both the Thomsen and Avon areas. After reviewing various Landsat datasets and analyzing several composites and clusters with Idrisi Andres software, only the larger Thomsen Field showed anomalous charactaristics. Those calculated satellite images are shown also.

Additional sophisticated methods of manipulating satellite imagery to define various vegetative, soil, and rock alterations are well documented. However, those methods require the use of specific bands of hyperspectral data and were not attempted.

Yahoo Map of Area (notice Emporia State) (Left) and KGS Production Map of Coffey County Oil Fields (Right)

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Assumption of Hydrocarbon Microseepage

This image was taken from the website of Geomicrobial Technologies. The GMT website contains a more detailed explanation of the various effects of hydrocarbon microseepage.

The effects of hydrocarbon microseepage to surface rocks, soils, and vegetation are well documented (Schumacher 1996). Without going into great detail, the primary alterations we would likely see in these two fields in Coffey County would be soil alterations. These changes in the soil chemistry and composition could affect soil pH, Eh, and other charactaristics which could cause either stress or favor one type of landcover vegetation over another. It should also be noted that microseepage theoretically declines as the reservoir is depleted unless sufficient pressure is maintained on the reservoir with secondary reco methods such as waterflooding. Also, microseepage should in principle "shrink" as the oil field becomes smaller, especially in a structural setting where the remaining oil should flow updip.

However, these are oversimplified statements as many factors can affect the reco effiency. These factors include reservoir zone porosity and permeability, faulting and fractures (which can redirect the flow of the seepage), oil company practices, and distribution of existing wells.

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Overview of the Thomsen and Avon Fields

USGS Topo Map with outline of Thomsen Field

The Thomsen Field is a structural high with a profile similar to the topographic structure. The primary producing zone is the Ordovician age Simpson Sand which subcrops on the unconformity at the base of the Chattanooga Shale. Another sand in the Pennsylvanian section locally called the "Squirrel Sand" also produces in some areas of the field. There are excellent oil wells virtually on the shores of John Redmond Lake on the east side so the eastern boundary is not fully known.

Since the field disco in 1972, 1.8 million barrels of oil have been produced.

The terrain is gently rolling, low relief hills, almost entirely pasture except for the wooded areas along the lake shore and along the creeks.

USGS Topo Map with outline of Avon Field

The Avon Field is also a structural trap of Ordovician rocks, but the primary zone is the Viola Limestone which is eroded away from the producing areas of the Thomsen Field. Stratigraphically, the Viola interval normally lies on top of the Simpson. In the Avon Field, the Viola subcrops at the pre-Chattanooga unconformity.

Since the field was discovered in 1973, 232,000 barrels of oil have been produced.

The terrain of Avon oilfield is essentially flat, with a mix of pasture and cultivated fields. The trees are limited to areas along the creeks.

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Color Infrared and Satellite Images of the Thomsen and Avon Fields

Set 1: NHAP (May 1981) Color Infrared Imagery Analysis of Thomsen Field (Discovered 1972)

(Left to Right) (Provided by USGS)Images showing original NHAP May 1981 CIR along with the anomalies outlined and the Thomsen Oil Field outlined. The correlation is high between the CIR anomaly and the Thomsen Field. Unfortunately there were no CIR images available before 1981 which would help define whether oilfield development activity was possibly the cause of the anomaly.

Set 2: FSA (2006) Color Infrared Imagery Analysis of Thomsen Field (Discovered 1972)

(Left to Right) (Provided by KDASC)Images showing original FSA 2006 CIR along with the anomalies outlined and the Thomsen Oil Field outlined. The FSA images are much higher resolution and not as obvious as the earlier images. However, it appears the area of CIR anomaly has become smaller over time.

Set 3: NHAP (May 1981) Color Infrared Imagery Analysis of Avon Field (Discovered 1973)

(Left to Right) (Provided by USGS)Images showing original NHAP May 1981 CIR along with the CIR anomalies outlined and the Avon Oil Field outlined. Notice the difficulty in picking the anomalous areas when the land use type changes from pasture to cultivated fields. There does not appear to be a correlation between the two fields aside from the small "finger" of the CIR anomaly which overlaps the field boundary. It is worthy to note this "finger" is located over the highest well (probable apex) in the field.

Set 4: FSA (2006) Color Infrared Imagery Analysis of Avon Field (Discovered 1973)

(Left to Right) (Provided by KDASC)Images showing original FSA 2006 CIR along with the anomalies outlined and the Avon Oil Field outlined. There is some correlation on the on the east side but the the CIR anomaly extends to the east. The white area on the CIR image is what is locally referred to as "alkali spots" where salts are formed in and on top of the soil. These areas of high salt concentration inhibit growth of pasture grass and require treatment on cultivated lands. There are many causes of these "alkali" deposits including hydrocarbon microseepage.(Schumacher)

Set 5: Landsat NDVI and Cluster Analysis of Thomsen Field (There were no satellite anomalies found for the Avon Field)

(Left to Right)NDVI image, Cluster Map taken from multi-county image, Cluster Map for data within window area. As mentioned earlier, the Avon Pool did not show any noticeable features on any of the same images as shown above. This is either due to the small size of the field or the different cause of the CIR anomaly. The cluster over the Thomsen Field shows up on both a small dataset and a large multi county dataset though much smaller in pixels. (All images used data provided by the USGS and processed with Idrisi Andes software.)

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Conclusions

In reviewing the sets of images, there are noticeable correlations between the aerial and satellite images for both oil fields. The next logical step would be a more comprehensive ground study to discover the cause of the Thomsen CIR anomaly. Field visits along the publicly available county and lease roads showed consistent pasture. Soil salts such as those verified by field visits to the Avon Pool may also be present in the Thomsen area, but is more difficult to find (especially on private lands.) Soil surveys on both areas could also map the Ph and Eh values to see if additional anomalies also exists similar to the CIR image.

The Thomsen anomaly could also be caused by oilfield development such as graveled roads to individual wells on 10 acre spacing or oil field pollution. The cause could also be surface rock which affects both the growth and density of grasses and the reflectivity measured by a satellite. Since the land was private, I was not able to walk the area other than what was accessible by roads. There was a shallow creek on the south side of the Thomsen Field that was cut into thinly layered limestone so near surface rock is a distinct possibility.

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References

Schumacher, Dietmar,1996. Hydrocarbon-induced alteration of soils and sediments. In Hydrocarbon migration and its near-surface expression. American Assoc of Petroleum Geologists, Memoir 66, pp 71-89

Zhang, J, Meer, Van Der, and Yang, H, 2000. Aerospace Detection of Hydrocarbon-Induced Alteration. Chapter 7, Geochemical Remote Sensing of the Subsurface, pp 233-24571-89

Remote Sensing Tutorial Section 5: Finding Oil and Gas from Space http://www.fas.org/irp/imint/docs/rst/Sect5/Sect5_5.html

Geomicrobial Technologies, Ochelata, KS. About Microseepages

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