Shale Devonian

FIGURE 15.7 Secondary changes in the total group composition of soluble organic matter as a result of simulated water washing extracts of the Miocene lignite and shale (both of the Bechatow open cast mine, Poland), the Upper Devonian shale (the Holy Cross Mountains, Poland), and the Upper Carboniferous bituminous coal (the Upper Silesia Coal Basin, Poland). 

In general these substances are widely distributed in the acid distillates but appear to increase in number at two stratigraphic levels (1) in the middle Silurian McKenzie Limestone and (2) in the middle Devonian shales. Furthermore, possible two- and three-ring aromatic or heteroaromatic structures show similar increases. There is also a rough correlation with the Kjeldahl nitrogen content of the samples (Table VI). 

C17 Isoprenoid 2,6,10-Trimethyltetradecane from a Devonian Shale The Role of Squalene as a Possible Precursor, Tetrahedron (1967) 23, 2609-2619. 

These include (1) tight sandstones, (2) Devonian shales. (3t geopiessured zones, (4) deep basins, (5) gas associated with coal seams, and (6) gas in the form of methane hydrates. 

Devonian Shales. The large eastern Devonian gas shales resource base underlies approximately 174,000 square miles (453,000 km2) of the eastern U.S. Estimates of recoverable gas range from 2 to 15% of the gas m place. Natural gas has been produced from these shales for decades. Well production rates are relatively low, but after the first few years of production it does not usually decline rapidly with time. A major constraint to present-day exploitation has been the extraordinary inability to predict with confidence the gas production rates that may be obtained in wells drilled outside the traditional production areas. Presently, the GRI is studying the systematics of historically successful fields, including the Appalachian, Illinois, and Michigan Basins. 

Fig. 20a and b. a) Radiolarian test enclosed in pyrite from the Devonian shale of Meggen (FRG). Silica of the testis replaced by sphalerite (ZnS) b) Marcasite containing budding structures interpreted as pseudomorphs after Pyrodictium. From sulfide formation of the East Pacific rise (Tufar et al., 1984) 92>... 

Degasification of coal, gas from Devonian shale, gas from tight formations, gas from geopressured zones, gas from biomass and gas from in-situ coal gasification, etc. 

A Comparison Between the Properties of Devonian Shale and Green River Oil Shale via Thermal Analysis... 

These oil shales represent two trillion barrels of oil in Colorado, Utah, and Wyoming, and an additional one trillion barrels of oil of Devonian shale formation in the eastern United States. Eastern Devonian shale is quite different from western Green River shale. The noticeable differences are in geological age, kerogen structure, oil content, pyrite, and other mineral compositions. In the past, little effort has been focused on Devonian shales. However, the increasing role of eastern shales has now... 

Figure 1. TGA and DTG thermal analyses for (A) Green River shale kerogen and (B) Devonian shale kerogen (No. 43)...

Table II. Activation Energy for Thermal Decomposition of Raw Shale and Kerogen Concentrate from Green River Oil Shale and Devonian Shale °...

Figure 2. DSC thermal analysis for (A) Green River oil shale and (B) Devonian shale (No. 43). (Both raw shale and kerogen concentrate.) (--) Raw shale, (----) kerogen concentrate, (— —) baseline.

The thermal properties of Devonian shale are quite different from those of Green River oil shale. The associated pyrite in kerogen concentrate may contribute greatly to the effect on thermal degradation of Devonian gas-bearing shale. For the first time DSC was applied to determining thermal properties of Devonian shale as well as Green River oil shale. 

Figure 3. DSC thermal analysis of pyrite in (A) pyrite mineral (Rico, Colorado), (B) Devonian shale kerogen, and (C) pyrite-reduced kerogen of...

The Devonian shale sample generally had a darker appearance with fewer and less distinct bands than the Green River shale sample, and the organic matter appeared to be more evenly distributed over the 2.5-cm sample. Several areas of this sample were examined using the slow rastering microprobe techniques to determine the elemental distribution in this material. The observations made in two of the areas are presented below. 

Figure 3. SEM and C, Fe, Ca, Mg, Si, Al, K, Na, and Ti x-ray intensity distributions in dark band of Devonian shale...

This study has shown that the sample of Devonian shale is composed primarily of silicates with much lower amounts of carbonate minerals. Here, as with the Green River shale sample, the silicate minerals were associated primarily with the organic-rich areas of the shale, and when present, the carbonate minerals were found mainly in the organic-poor areas. The siliceous minerals of this Devonian shale sample were found to be quartz, illite, and muscovite, with trace amounts of kaolinite. Calcite, dolomite, Fe-rich dolomite or magnesite, and siderite were observed in the carbonate regions of the Devonian shale. However, the... 

Figure 4. SEM and Fe, S, Ti, and C x-ray intensity distributions in dark area of Devonian shale. Large Ti particle at upper right contains C small Ti particle near center contains O.

Devonian shale had regions with much higher concentrations of siderite than were found in the Green River shale sample. As in the Green River shale, the FeS2 particles were less than 50ju.m in diameter and in most instances were observed only in the organic-rich areas of the samples. 

---