Overthrust

Figure 2-47. Overthrust structural trap (Painter Reservoir, Wyoming) [26].

Reflection suggests that some of the sulfur allocated to district I might be reapportioned to district III. However, the major increase is found in district IV. This is based on a projection of production from the Overthrust Belt. The evidence for this is currently very scanty. Proved reserves have been estimated at. 4.5 TCF with ultimate resources at 100 TCF but drilling costs are high (23) The H2S content appears to run from 10 percent to 18 percent (24, 25). One processing plant with a sulfur capacity of 1200 T/d is already planned (26) Eight such plants would fulfill the 1990 estimate. By 1990, however, development of western tight sands and imports of Alaskan and/or Canadian gas could reduce the competitive position of the Belt. 

On a qualitative basis, the estimates of recovered sulfur from refinery operations appear to be the most secure. Except for district IV, which depends heavily on the ultimate productivity of the Overthrust Belt, estimates of sulfur production from sour natural gas also seem reliable. The heavy crude oil sulfur output estimate is reasonably firm. Oil shale, tar sands, heavy oil and in situ coal combustion will produce little sulfur even under optimistic scenarios. The smelter acid projection is weak. Metal output may... 

After weighing these various factors, we have concluded that there will be a significant expansion in sour gas production and processing in the area over the coming decade, starting in 1983. Amoco and Chevron will likely be the first major developers of sour gas deposits in the Overthrust. Other companies will probably begin to participate significantly sometime in the middle 1980 s. 

Table III summarizes the supply outlook for the United States through the study period. We wish to re-emphasize that the major increase in nsour gas sulfur will occur primarily in the Overthrust region which, because of its long distance from major markets, could cause a substantial shift in regional trade patterns within the United States and Canada.

By relating the supply forecast that has been presented earlier in this paper with the projections of future demand, we can arrive at the trend in the supply/demand relationship over the forecast period. The U.S. has been a small net-importer of sulfur values during most of the past decade. In 1978, the U.S. had a net deficit position of about 400,000 tons. With a short-term upturn in phosphate demand, both domestic and international, we anticipate that the deficit position will widen over the next year or so. Even though U.S. exports will likely increase due to rising prices for sulfur in the export market, U.S. imports will also rise. But, with the advent of large amounts of sulfur starting to come from the Overthrust Belt by the mid-1980 s, we believe that the deficit position will reverse itself and place the U.S. in a net export position. In the latter part of the 1980 s, we anticipate this surplus to widen considerably. 

Well strata are involved in overthrusting which explains unusual depth figures values are in p.p.m., corrected for sulfur content. 

Figure 9. The increase of rank of coal in the immediate vicinity of the Sutan overthrust near Bochum (after M. TeichmuUer (25) ...

Pressure of the overburden does not cause chemical reactions which lead to a higher rank. Experiments have shown that static pressure even retards coalification processes. By contrast, pressure affects the physical properties, notably the porosity and moisture content in low rank coals. Further, the optical anisotropy of vitrinites (which is a tension anisotropy) is caused by pressure. Shearing movements have influenced the chemical coalification only occasionally and locally in the foredeeps that we have studied (for instance in the immediate vicinity of overthrusts). In such cases the tectonic movements probably were so quick that the friction heat and the shearing could operate. Shearing in no way can account for the gradual increase in coal rank with depth. 

The high coastal escarpments composed of Jurassic limestones recover complicated geological folds broken by tectonic faults and overthrusts. At the sites where intrusive rocks are developed, remarkable capes are formed. The largest of them are capes Ayu Dag, Medved Gora, Ai Todor, Nikita, Foros, Laspi, Sarych, and Aia. 

O Hara K. D. (1988) Fluid flow and volume loss during mylonitization an origin for phyllonite in an overthrust setting. Tectonopkysics 156, 21—34. 

Subduction-related magmatic arc (or simply, arc) Chains of volcanoes on the overthrust plate parallel to, and 100-200 km horizontally away from, the surface expression of a subduction zone, together with coeval, underlying plutonic rocks. 

Milliken K. L. (1998) Carbonate diagenesis in non-marine foreland sandstones at the western edge of the Alleghanian overthrust belt, southern Appalachians. In Carbonate Cementation in Sandstones Distribution Patterns and Geochemical Evolution (ed. S. Morad). International Association of Sedimentologists, Oxford, vol. 26, pp. 87-105. 

Deming, D., Nunn, J.A. and D.G. Evans, 1990. Thermal effects of compaction-driven groundwater flow from overthrust belts. Journal of Geophysical Research, Vol. 95, no. B5, pp. 6669-6683... 

Light hydrocarbons for petroleum and gas prospecting Overthrust Belt, Wyoming-Utah... 

Fig. 5-44. Composite cell map in which the Monte Carlo simulations have been applied to methane, ethane and propane anomalies in the Overthrust Belt, Wyoming-Utah, highlighting the regions where all three of these gases are above their respective medians.

---