Geology topics

R.C. Burruss

Publications and source records attributed to R.C. Burruss.

21 records · Page 2Linked to original sources

USGS1990

Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy

Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

Chemical Geology↗

USGS1990

Hydrocarbon-water interactions during brine migration: Evidence from hydrocarbon inclusions in calcite cements from Danish North Sea oil fields

Crude oils in primary and secondary fluid inclusions in calcite from fractures in seven offshore oil fields associated with diapiric salt structures in the Danish sector of the North Sea were analyzed by capillary column gas chromatography and compared with crude oils produced from the same reservoirs. Oils from fluid inclusions in all fields show evidence of biodegradation (decreased n - C 17 /pristane and n - C 18 /phytane ratios and loss of n-C 7 , 2-methyl hexane, and 3-methyl hexane relative to methyl cyclohexane) and water washing (absence of benzene and depletion of toluene). Some oils in inclusions are extremely enriched in C 6 and C 7 cyclic alkanes suggesting that these samples contain hydrocarbons exsolved from ascending, hotter formation waters. Compared to inclusion oils the produced oils are less biodegraded, but are water washed, indicating that both types of oil interacted with large volumes of formation water. The carbon isotopic composition of the calcite host of the fluid inclusions in the Dagmar and Skjold fields is as light as −16.5%. PDB and the sulfur isotopic composition of pyrite in and adjacent to the calcite veins in the Skjold field is as light as −39.6%. CDT, indicating that biodegradation of the oils was a source of some of the carbon in the calcite and sulfate reduction was the source of sulfur for the pyrite. The evidence for microbial degradation of petroleum is consistent with present-day reservoir temperatures (65°–96°C) but is not consistent with previous estimates of the temperatures of calcite vein filling (95°–130°C) which are much higher than the temperatures of known occurrences of biodegraded oil.

Geochimica et Cosmochimica Acta↗

USGS1989

Geochemistry of oils and hydrocarbon source rocks, greater Anadarko Basin: evidence for multiple sources of oils and long-distance oil migration

Organic geochemical analyses of 104 crude oils and 190 core samples of dark-colored shales from the greater Anadarko basin show three major oil types which generally correlate with reservoir age and source-rock age. Analyses include C 3 -C 30 whole-oil gas chromatography, C 10+ saturated-hydrocarbon-fraction gas chromatography, and carbon stable isotopes (ppt relative to PDB) of saturated (sat) and aromatic (arom) hydrocarbon fractions. Three samples from Middle Ordovician Simpson Group reservoirs are "typical" Ordovician oils (type 1), having strong odd-carbon predominance in the C 13 to C 19 n-alkanes, containing little or no acyclic isoprenoids, an δ 13 C values of -33.9 ppt (sat) and -33.7 ppt (arom). Oils from Silurian to Devonian and Mississippian reservoirs (type 2) show little or no odd-carbon predominance in the n-alkanes, a regular decrease in abundance of n-alkanes with increasing carbon number, pristane/phytane ratios (pr/ph) of 1.1 to 1.5, and δ 13 C values of -30.6 ppt (sat) and -30.1 ppt (arom). Oils in Pennsylvanian reservoirs (type 3) have the greatest amounts of C 15+ hydrocarbons, are isotopically heavy (-27.5 ppt [sat] and -26.4 ppt [arom]), have methyl-cyclohexane as the most abundant hydrocarbon, and have pr/ph values from 2.0 to 0.9. Oils from the Kansas shelf area of the Anadarko basin are similar to the Anadarko oil types except that they have only traces of toluene and no detectable benzene. The relative abundance of toluene in the C 7 hydrocarbons systematically decreases with distance from the depocenter of the basin. The aromatic compounds are removed by water-washing, and hence could have been lost by contact with progressively greater amounts of formation water during long-distance migration. The lack of thermally mature source rocks in southern and central Kansas supports this hypothesis.

Oklahoma↗