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USGS2009

Field tests prove microscale NRU to upgrade low-btu gas

The Kansas Geological Survey (University of Kansas) and the American Energies Corp., Wichita, have conducted field tests of a scalable, microscale, N 2 -rejection unit (NRU) to demonstrate its effectiveness to upgrade low-pressure ((<100 psig) and low-volume (=100 Mcfd) low-btu gas to pipeline quality. The tests aim to develop inexpensive NRU technology, which is designed for low- volume, low-pressure gas wells, to significantly increase the contribution of marginal low-btu gas to the gas supply of the US. The NRU uses two towers and uses three stages, namely, adsorption under pressure, venting to 2 psig, and desorption under vacuum. The modular design allows additional sets of towers to be added or removed to handle increases or decreases in feed volumes. The field tests also reveal that a strong compressor, which is capable of evacuating the tower (volume) as quickly as possible, should be employed to reduce process cycle time and increase plant throughput.

Oil & Gas Journal↗

USGS1987

Possible Late Middle Ordovician organic carbon isotope excursion: Evidence from Ordovician oils and hydrocarbon source rocks, mid-continent and east-central United States

Oils generated by Middle Ordovician rocks are found throughout the Mid-Continent and east-central regions of the United States. Gas chromatographic characteristics of these oils include a relatively high abundance of n-alkanes with carbon numbers less than 20, a strong predominance of odd-numbered n-alkanes between C 10 and C 20 , and relatively small amounts of branched and cyclic alkanes. Saturated and aromatic hydrocarbon fractions of 43 Ordovician oils from the Anadarko, Ardmore, Forest City, Illinois, Michigan, Salina-Sedgwick, and Williston basins and the Iowa shelf demonstrate a wide range in carbon isotope composition (^dgr 13 C sat = -24.9 ^pmil to -33.9 ^pmil, (^dgr 13 C arom = -24.3 ^pmil to -33.7 ^pmil). Saturated and aromatic hydrocarbons extracted from late Middle Ordovician shales (17 core samples) show ranges in ^dgr 13 C similar to that of the oils. The wide ranges in ^dgr 13 C for oils and rock extracts reflect a major, positive excursion(s) (6-9 per ^pmil) in organic matter ^dgr 13 C in late Middle Ordovician rocks. This excursion has at least a regional significance in that it can be documented in sections 480 mi (770 km) apart in south-central Kansas and eastern Iowa. The distance may be as much as 930 mi (1,500 km) if the carbon isotope variations observed in Michigan basin Ordovician oils and in organic matter from late Middle Ordovician rocks in southwestern Ontario are related to the same carbon isotope excursion. Organic-matter ^dgr 13 C in core samples from south-central Kansas and eastern Iowa is not directly related to variations in quantity or quality of organic matter, or maceral compositi n. The positive excursion in organic matter ^dgr 13 C is a possible result of increased organic matter productivity and/or preservation. The parallel shifts in organic and carbonate ^dgr 13 C in core samples from 1 E. M. Greene well, Washington County, Iowa, imply changes in the isotope composition of the ocean-atmosphere carbon reservoir. Differences in the magnitude of the carbon isotope shifts between organic matter (8.8 ^pmil) and carbonate (4.2 ^pmil) in this core suggest a decrease, either locally or regionally, in available dissolved CO 2 , possibly a result of high organic-matter productivity and/or limited circulation in the late Middle Ordovician seas.

American Association of Petroleum Geologists Bulle↗