Hydrocarbon Inclusions Research Articles

Hydrogen-Bonding 3D Networks by Polyhedral Organosilanols: Selective Inclusion of Hydrocarbons in Open Frameworks

Tetrahedral organosilanols E[C6H4Si(i-Pr)2OH]4 (E = C, 2a; E = Si, 2b) as well as octahedral organosilanols Si8O12(CH═CHC6H4SiR2OH)8 (R = i-Pr, 5a; R = Ph, 5b) have been derived from tetraphenylmethane and -silane (1a,b) and octavinyloctasilsesquioxane (3) designed for self-assembly of 3D hydrogen-bonding networks possessing large porosity. X-ray analyses following crystallization of 2a,b from THF/benzene and either hexane or heptane revealed adamantane-type networks with hydrogen bonds between the silanols of four separate molecules and selective inclusion of hexane or heptane, respectively. Upon changing the mixed solvent to THF/benzene/cyclohexane, X-ray analysis of 2a showed an inclusion compound of composition 2a·1.5benzene. TOPOS analyses of 2a·1.5benzene demonstrated a non-adamantane-type framework with sra network topology. Crystallization of 5a,b from acetone/benzene followed by X-ray analyses confirmed the production of the inclusion compounds 5a·18benzene and 5b·23benzene. The open frameworks o...

Organic geochemical and fluid inclusion evidence for filling stages of natural gas and bitumen in volcanic reservoir of Changling faulted depression, southeastern Songliao basin

Recently, volcanic gas reservoirs in Yaoyingtai (腰英台) and Daerhan (达尔罕) tectonic belts in Changling (长岭) faulted depression of southeastern Songliao (松辽) basin have been discovered. Based on the compositions and isotopic values, the natural gas is characterized by high content of methane, low content of C2 +, and C1/C1–5 beyond 0.95. Also, the natural gas contains nonhydrocarbons including carbon dioxide with the content from 20% to 40% and minor amount of N2. Combined with the isotopic values, the natural gas is generated by humic kerogen and coal-derived type, but in Daerhan, the natural gas is probably mixed by oil type gas. From the measurement of lithology and fluid inclusions in volcanic rocks, the bitumen, liquid hydrocarbon, and gas hydrocarbon inclusions are present. Through the analysis of the single gas inclusion in volcanic reservoir, the content of carbon dioxide is low, so the carbon dioxide and hydrocarbon gas of the reservoirs are not accumulated at the same time. In addition, minor amount of bitumen in the reservoirs is formed by thermal evolution of the crude oils sourced from the Yingcheng (842557CE) Formation mudstones through the characterizations of the biomarkers. The distribution of homogenization temperatures presents two peaks, one with the liquid hydrocarbon filling stage, and the other with gas filling stage. However, in Daerhan tectonic belt, the second peak is gas and carbon dioxide mixed filling period probably. Combined with the homogenization temperatures of salt water inclusions, the oil and gas filling period is from Qingshankou (青山口) Formation to Nenjiang (嫩江) Formation in the research area. During the charging period, minor amount of inorganic carbon dioxide filled into the trap, but plenty of inorganic carbon dioxide from the end of Sifangtai (四方台) to Eogene periods was related with the structural movement.

Fluid inclusion evidence for a coupling response between hydrocarbon charging and structural movements in Yitong Basin, Northeast China

For this study 145 fluid inclusion samples from 19 wells have been analysed to unravel the relationship between the complex charging history and tectonic evolution of the Yitong Basin, Northeast China. Fluid inclusion petrography, microthermometry, transmitted light microscopy and micro fluorescence observation methods were employed to systematically obtain information on fluorescent colors of hydrocarbon inclusions, homogenization temperatures of oil inclusions and their coeval aqueous inclusions. The results indicate three events of oil charging and one gas charging event for the Paleogene reservoirs. The oil charging events have been reconstructed at 38.1–27 Ma, 19.5–10 Ma and 1–0 Ma, while the gas charging event most likely occurred at 1–0 Ma. When combining the known information on hydrocarbon charging history and structural evolution, two intermittent periods of hydrocarbon migration and accumulation are likely to have occurred at 27–19.6 Ma and 10–2 Ma, coupling to two structural events. It is suggested that these events caused the termination of hydrocarbon supply or destruction of the previously accumulated hydrocarbons.

Fluid flow reconstruction in karstified Panormide platform limestones (north-central Sicily): Implications for hydrocarbon prospectivity in the Sicilian fold and thrust belt

Diagenetic analysis based on field and petrographic observations, isotope and microthermometric data was used to reconstruct the fluid flow history of the Cretaceous shallow water limestones from the Panormide platform exposed in north-central Sicily. Analysis focused on diagenetic products in cavities and dissolution enlarged fractures of the karstified limestones that occur just below a regional unconformity. The fluid flow history could be broken down into five stages that were linked to the kinematic and burial history of the region. (1) Petrography (zoned cathodoluminescence and speleothem textures) and stable isotopes (6.5 < δ 18O V-PDB < −3.5‰ and 0 < δ 13C V-PDB < −14‰) indicate that the earliest calcite phase was associated with karstification during emergence of the platform. Limestone dissolution at this stage is important with regard to possible reservoir creation in the Panormide palaeogeographic domain. (2) Fine-grained micrite sedimentation, dated as latest Cretaceous by nannopalaeontology and its 87Sr/ 86Sr isotope ratio (0.7078), marks replacement by marine fluids during subsequent submergence of the karstified platform. (3) The following calcite cement was still precipitated by marine-derived fluids (−7.0 < δ 18O V-PDB < −5.0‰ and −3.0 < δ 13C V-PDB < 0.5‰/ T m = −2 to −5 °C), but at increasingly higher temperatures ( T h = 60–120 °C). This has been interpreted as precipitation during Oligocene foredeep burial. (4) Hot ( T h = 130–180 °C), low saline ( T m < −2.5 °C) fluids with increasingly higher calculated δ 18O SMOW signatures (+6 to +14‰) subsequently invaded the karst system. These fluids most likely migrated during fold and thrust belt development. The low salinity and relatively high δ 18O SMOW signatures of the fluids are interpreted to be the result of clay dewatering reactions. The presence of bitumen and associated fluorite with hydrocarbon inclusions at this stage in the paragenesis constrains the timing of oil migration in the region. (5) Finally, high saline fluids with elevated 87Sr/ 86Sr (0.7095–0.7105) signatures invaded the karst system. This last fluid flow event was possibly coeval with localized dolomitization and calcite cementation along high-angle faults of Pliocene age, as suggested by identical radiogenic signatures of these diagenetic products.

Widespread bedding-parallel veins of fibrous calcite (’beef') in a mature source rock (Vaca Muerta Fm, Neuquén Basin, Argentina): evidence for overpressure and horizontal compression

Abstract: In the Neuquén Basin of Argentina, ’beef' (bedding-parallel veins of fibrous calcite) is widespread within Late Jurassic black mudstones. A typical vein consists of two grey inner zones and two white outer zones. The inner zones contain inclusions of wall rock and hydrocarbons. Calcite fibres are perpendicular to the margins. In the outer zones, the angle between fibre and margin varies from about 45° at the vein tips to 90° in the centre. Imprints of fossils are offset, proving that the fibres have grown antitaxially. We infer that the veins opened in two phases. During Phase 1, the opening was vertical, against gravity. During Phase 2, the veins resisted tectonic shortening, so that shear stresses acted at the margins. The senses of shear account for the fibre angles. At outcrop, igneous intrusive rocks have cut and metamorphosed the veins. From burial curves, maturity calculations, growth strata, and ages of igneous intrusions, we estimate that the inner zones of the beef formed in the oil window, during the Aptian to Albian, and that the outer zones formed in the gas window, during the Cenomanian to Campanian. We infer that the beef is evidence for fluid overpressure during hydrocarbon generation.

Primary hydrocarbon inclusions in garnet of diamondiferous eclogite from the Udachanaya kimberlite pipe, Yakutia

Primary hydrocarbon inclusions in garnet of diamondiferous eclogite from the Udachanaya kimberlite pipe, Yakutia

Biodegradation of synthetic detergents in wastewater

A total of 76 wastewater samples were randomly collected from pharmaceutical, textile, and detergentmanufacturing industries as well as the Agbara Sewage Treatment Plant (STP). Thirty-eight samples each in 2-L plastic containers were collected for morning and evening effluent used for this study. Composite samples were later developed and the physico-chemical properties of these samples determined. The physico-chemical properties of the composite wastewater influenced the selected microbial population adapted to utilization of detergent components. The optimum temperature range of the composite wastewater was 33.9 – 34.3oC while the mean optimum pH ranged from 6.9 – 8.8 for the laboratory simulated biodegradation of test detergents. Although, the fungal consortium was eliminated as the medium approached the alkaline pH, this is as a result of the metabolites produced. The macroelements, the BOD and the hydrocarbon concentration of the composite effluent were above the EU and FEPA limits for discharged effluent. The composite effluent was thereafter spiked with test detergents (Elephant, Omo, Klin, Ariel Persil, Teepol, and SDS) at 0.01% (w/v) and its progressive degradation monitored for 30 days. The microbial detergent-degraders population changed between Day 0 and 15, thereafter it stabilized. The heterotrophic bacterial count from the seventy-six randomly collected effluent samples was 42.9 x 106 cfu/ml, while the mean bacterial detergent-degrader population was 20.94 x 106 cfu/ml. The mean fungal population from the randomly collected effluent sample was 4.5 x 106 cfu/ml. The bacterial detergent-degraders characterized and identified include Pseudomonas aeruginosa, Escherichia coli, Enterococcus majodoratus, Klebsiella liquefasciens, Enterobacter liquefasciens, Klebsiella aerogenes, Enterobacter agglomerans, Staphylococcus albus, Proteus sp., Klebsiella oxytoca and Brevibacterium sp., while the fungal detergent-degrader included; Myceliophthora thermophila, Geomyces sp., Alternaria alternata, Fusarium sp., Aspergillus flavus and Asperigillus oryzae. The primary biodegradability of synthetic detergent was confirmed by the Methylene Blue–Active Substance (MBAS) method. Gas chromatography (GC) provided the convincing evidence of synthetic detergent mineralization within the 30 day period in a sewage treatment plant. The detection of unusual peaks in the GC profiles provided the scientific evidence of inclusion of certain hydrocarbons in detergent formulation outside that of industry specifications. The unusual peaks are attributable to inclusion of certain chemical optical brighteners (C17–C24). Linear alkyl benzene sulphonates (LAS) which is the principal synthetic detergent component are thus biodegradable and its use in detergent formulation is environment - friendly.

Petroleum and aqueous inclusions from deeply buried reservoirs: Experimental simulations and consequences for overpressure estimates

Synthetic hydrocarbon and aqueous inclusions have been created in the laboratory batch reactors in order to mimic inclusion formation or re-equilibration in deeply buried reservoirs. Inclusions were synthesized in quartz and calcite using pure water and Mexican dead oil, or n-tetradecane (C 14H 30), at a temperature and pressure of 150 °C and 1 kbar. One-phase hydrocarbon inclusions are frequently observed at standard laboratory conditions leading to homogenization temperatures between 0 and 60 °C. UV epifluorescence of Mexican oil inclusions is not uniform; blue and green-yellow colored inclusions coexist; however, no clear evidence of variations in fluid chemistry were observed. Homogenization temperatures were recorded and the maxima of T h plotted on histograms are in good agreement with expected T h in a range of 6 °C. Broad histograms were reconstructed showing non-symmetrical T h distributions over a 20 °C temperature range centered on the expected T h. This histogram broadening is due to the fragility of the fluid inclusions that were created by re-filling of pre-existing microcavities. Such T h histograms are similar to T h histograms recorded on natural samples from deeply buried carbonate reservoirs. T h values lower than those expected were measured for hydrocarbon inclusions in quartz and calcite, and for aqueous inclusions in calcite. However, the results confirm the ability of fluid inclusions containing two immiscible fluids to lead to PT reconstructions, even in overpressured environments.

Simulation of the fluorescence evolution of “live” oils from kerogens in a diamond anvil cell: Application to inclusion oils in terms of maturity and source

The evolution of fluorescence has been measured for “live” oils generated from 14 oil-prone kerogens or coals from varying depositional environments during closed system pyrolysis in a diamond anvil cell at three heating rates (3, 8, and 25 °C/min), and temperatures up to 600 °C. The measured fluorescence intensities of the samples, employing using violet excitation at 405 nm, increases significantly during maturation intervals within the oil window, while the fluorescence spectra of oils generated from all studied kerogens exhibit progressive blue-shift of peak wavelengths ( λ max) and red/green quotients ( I 650/ I 500) upon increasing maturity. The observed trend is consistent with a maturity dependence of the spectral shift, which is widely recognized in natural hydrocarbon inclusions and crude oils using ultraviolet (UV) excitation (365 nm). The data presented herein suggest that the λ max of spectra for inclusion oils shift in similar direction despite differences in composition or source kerogen. This implies that the reverse or anomalous trends reported for inclusion oils in nature may be attributed to other processes, which significantly alters the fluorescence properties of oils subsequent to their generation. Oils with the similar color ( λ max or I 650/ I 500) can be derived from diverse kerogens with maturities that vary by ±0.3% Ro, suggesting that the fluorescent colors of crude and inclusion oils are both maturity- and source-dependent, and therefore cannot be used as universal maturity indicators. In addition, the blue-shifts observed for cumulative oils generated from all kerogens approaches similar minima λ max values around the green-yellow wavelength (564 nm) and at I 650/ I 500 values around 0.6, at maturities close to the middle or late stage of oil generation. This suggests that most late-stage cumulative oils will exhibit similar colors. Oils generated during late-stage maturity intervals, however, can exhibit colors with shorter wavelengths.

Raman characteristics of hydrocarbon and hydrocarbon inclusions

The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm−1 to 2970 cm−1); (2) branch methyl has the particular peak of 748 cm−1±; (3) six cyclic has the particular peak of 804 cm−1±; (4) phenyl has two particular peaks of 988 cm−1± and 3058 cm−1± and the 988 cm−1± peak is stronger than the 3058 cm−1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm−1±, 1635 cm−1± and 2996 cm−1±, with the 1635 cm−1± peak being the strongest, showing that the number of carbon in hydrocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclusions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydrocarbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram. And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion, saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

Partition of compounds from gas to water and from gas to physiological saline at 310 K: Linear free energy relationships

Data have been assembled on gas to water partition coefficients for 374 compounds at 310 K. It is shown that an Abraham solvation equation with five descriptors can be used to correlate 350 such values, as log K W(310), with R 2 = 0.994 and S.D. = 0.154 log units. Division into a training set and a test set shows that there is no bias in predictions and that predictive capability of the equation is 0.16 log units. Use of indicator variables allows the inclusion of polyaromatic hydrocarbons and polychlorobiphenyls, and for a total data set of 374 compounds R 2 = 0.993 and S.D. = 0.163 log units. For partition from the gas phase into physiological saline (0.9% sodium chloride) at 310 K, a similar equation with five descriptors correlates values for 257 compounds with R 2 = 0.989 and S.D. = 0.180 log units. For 135 overlapping compounds for which both log K W(310) and log K W(saline) are known, the average error is only 0.032 log unit, suggesting that the two data sets can be combined. For the total of 631 data points, an equation with five descriptors plus indicator variables for polyaromatic hydrocarbons and polychlorobiphenyls has R 2 = 0.992 and S.D. = 0.177 log units.

Volatiles in a peralkaline system: Abiogenic hydrocarbons and F–Cl–Br systematics in the naujaite of the Ilímaussaq intrusion, South Greenland

Agpaitic rocks comprise most of the exposed part of the 1.16 Ga old, 8 × 17 km large and about 1700 m thick Ilímaussaq intrusion in South Greenland. Within these, more than 600 m thick sequence of sodalite-rich “naujaites” (mainly sodalite + arfvedsonite + alkali feldspar + nepheline + eudialyte + aenigmatite) are interpreted as a sodalite flotation cumulate. Sodalites show two to three different zones in cathodoluminescence (CL) and at least two zones in thin sections. The CL zones can be related to chemical differences detectable by electron microprobe, whereas relations with optical zonations are less obvious. Compositional trends in sodalite reflect trends in the evolution of volatile contents in the melt. The sodalite at Ilímaussaq is almost free of Ca and closely corresponds to the pure Na–Cl sodalite endmember with about 7 wt.% of Cl; S contents reach up to 0.9 wt.%. Cl/Br ratios range from 500 to 1700. Raman spectroscopy shows that S is present as [SO 4] 2− in sodalite, although sphalerite (ZnS) is a stable phase in naujaites. Peralkalinity and fO 2 conditions allow S 2− and [SO 4] 2− to be present contemporaneously. The whole naujaite sequence is divided into two parts, an upper part with low, homogeneous S contents and Cl/Br ratios in the sodalite cores, and a lower part with strongly variable and higher S contents and with Cl/Br ratios, which are decreasing downwards. The details of the S content and the Cl/Br ratio evolution show that sodalite strongly influences the halogen contents of the melt by scavenging Cl and Br. The naujaites were formed from a highly reduced, halogen-rich magma in equilibrium with magmatic methane at about 800 °C, which, upon ascent, cooling and fractionation, exsolved an aqueous fluid phase. Both fluids were trapped in separate inclusions indicating their immiscibility. Micrometer-sized aegirine crystals and primary hydrocarbon-bearing inclusions are abundant in the crystal cores. The inclusions were trapped at pressures up to 4 kbar, although the emplacement pressure of the intrusion is about 1 kbar. This indicates growth of the sodalite during melt ascent and a very effective mechanism of trace element scavenging during sodalite growth. Sodalite rims are devoid of aegirine or primary hydrocarbon inclusions and probably reflect the emplacement stage.

Origin of coarse-crystalline calcite cement in Early Ordovician carbonate rocks, Ordos basin, northern China: Insights from oxygen and carbon isotopes and fluid inclusion microthermometry

The calcite cement in the Lower Ordovician Majiagou Formation in the Ordos basin in northern China can be subdivided into three groups based on preliminary results of oxygen and carbon isotopes and fluid inclusion microthermometry. Group 1 has low oxygen isotopes (− 14‰ to − 18‰), low T h values (92–103 °C), and low salinities (1.7–4.9 wt.% NaCl equivalent) and is interpreted to have precipitated during early burial from porewater influenced by meteoric water. Group 2 has much higher oxygen isotope values (− 5‰ to − 8‰), which, coupled with the higher T h values (136–151 °C), suggest that the calcite was precipitated from fluids that were significantly enriched in 18O, possibly resulting from fluid–rock reaction during burial. Group 3 occurring along fractures is characterized by high salinities (21–28 wt.% NaCl equivalent) and is interpreted to have been precipitated from locally preserved residual evaporitic brines. The occurrence of primary hydrocarbon inclusions and its low carbon isotopes (− 11‰ to − 15‰) suggest that precipitation of group 3 calcite took place in the presence of hydrocarbons.

Application Of Organic Geochemistry To Detect Signatures Of Organic Matter In The Haughton Impact Structure

Organic geochemistry applied to samples of bedrock and surface sediment from the Haughton impact structure detects a range of signatures representing the impact event and the transfer of organic matter from the crater bedrock to its erosion products. The bedrock dolomite contains hydrocarbon-bearing fluid inclusions which were incorporated before the impact event. Comparison of biomarker data from the hydrocarbons in samples inside and outside of the crater show the thermal signature of an impact. The occurrence of hydrocarbon inclusions in hydrothermal mineral samples shows that organic matter was mobilized and migrated in the immediate aftermath of the impact. The hydrocarbon signature was then transferred from bedrock to the crater-fill lacustrine deposits and present-day sediments in the crater, including wind-blown detritus in snow/ice. Separate signatures are detected from modern microbial life in crater rock and sediment samples. Signatures in Haughton crater samples are readily detectable because they include hydrocarbons generated by the burial of organic matter. This type of organic matter is not expected in crater samples on other planets, but the Haughton data show that, using very high resolution detection of organic compounds, any signature of primitive life in the crater rocks could be transferred to surface detritus and so extend the sampling medium.

Hydrothermal dolomitization in the Lower Ordovician Romaine Formation of the Anticosti Basin: significance for hydrocarbon exploration

This study deals with the diagenetic evolution of dolostones of the Romaine Formation, from cores and outcrops on Anticosti and Mingan islands, and reports evidence for hydrocarbon migration in secondary porosity generated by high temperature / hydrothermal alteration. Four types of calcite (grouped into early (C1) and late (C2) assemblages) and six types of dolomite (grouped into 3 different (D1, D2 and D3) assemblages) are distinguished. According to fluid-inclusion and stable C-O isotope data, the early calcite group, which consists of sedimentary micrite, replacement microspar and early pore-filling calcite records near surface diagenetic environments. Early and pervasive replacement dolomites (RD1 and RD2 in the first dolomite (D1) assemblage) were formed during early burial, and are not related to porosity generation. Later replacement dolomites (RD3 and RD4 in the second dolomite (D2) assemblage) and pore-filling dolomite cements (PD1 and PD2 in the third dolomite (D3) assemblage) as well as minor sphalerite were formed from warm, saline fluids, which were likely hydrothermal in origin. Vuggy porosity was produced through brecciation and fracturing, and through some dissolution of the D1 dolomite assemblage by these hydrothermal fluids. Intercrystalline porosity was also created during formation of the D2 dolomite assemblage. The vugs were partly occluded by late-stage pore filling dolomite and calcite cements, pyrite and barite. Bitumen droplets in vugs together with hydrocarbon inclusions recorded in C2 calcite and in contemporaneous barite indicate a hydrocarbon migration event after the porositygenerating processes. The brecciation / leaching of a precursor dolomite host is uncommon in hydrothermal dolomite hydrocarbon fields, but is recognized in the adjacent coeval pool in Newfoundland. This type of alteration in the Ordovician carbonates with the presence of a rich hydrocarbon source rock and favourable maturation are key elements for the on-going exploration efforts in this basin.

Ore metal redistribution by hydrocarbon–brine and hydrocarbon–halide melt phases, North Range footwall of the Sudbury Igneous Complex, Ontario, Canada

We report methane-dominant hydrocarbon (fluid) inclusions (CH4±C2H6–C2H2, C3H8) coexisting with primary brine inclusions and secondary halide melt (solid NaCl) inclusions in Au–Pt-rich quartz-sulfide-epidote alteration veins associated with the footwall-style Cu–PGE (platinum-group element)–Au deposits at the Fraser Mine (North Range of the Sudbury Igneous Complex). Evidence for coentrapment of immiscible hydrocarbon–brine, and hydrocarbon–halide melt mixtures is demonstrated. A primary CH4–brine assemblage was trapped during quartz growth at relatively low T (min. T trapping∼145–315°C) and P (max. P trapping∼500 bar), prior to the crystallization of sulfide minerals in the veins. Secondary inclusions contain solid halite and a mixture of CH4, C2H6–C2H2 and C3H8 and were trapped at a minimum T of ∼710°C. The halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate (by replacement) early alteration quartz hosting the primary, lower T brine–CH4 assemblage. Laser ablation ICP-MS analyses show that the brine, hydrocarbon and halide melt inclusions contain significant concentrations of Cu (0.1–1 wt% range), Au, Bi, Ag and Pt (all 0.1–10 ppm range). Cu:Pt and Cu:Au ratios in the inclusions are significantly (up to 4 log units) lower than in the host alteration veins and adjacent massive sulfide ore veins, suggesting either (1) early Cu loss from the volatiles by chalcopyrite precipitation or (2) enhanced Au and Pt solubilities relative to Cu at the temperatures of entrapment. Concentration ratios between coexisting brine and CH4 inclusions $$[C^{{\rm elem}}_{{\rm brine}}/C^{{\rm elem}}_{{\rm CH_{4}}}]$$ are lower for Cu, Au, Bi and Ag than for other elements (Na, Ca, Fe, Mn, Zn, Pb) indicating that during interaction with the brine, the hydrocarbon phase was enriched in ore metals. The high concentrations of ore metals in hydrocarbon, brine and halide melt phases confirm that both aqueous and non-aqueous volatiles were carriers of precious metals in the Sudbury environment over a wide range of temperatures. Volatile evolution and magmatic sulfide differentiation were clearly part of a single, continuous process in the Sudbury footwall. The exsolution of H2O-poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of PGE and Au in the footwall ore systems. The study reports the first measurements of precious metal concentrations in fluid inclusions from a magmatic Ni–Cu–PGE environment (the Sudbury district).

Effects of thermal cracking of hydrocarbons on the homogenization temperature of fluid inclusions from the Niigata oil and gas fields, Japan

The changes of the homogenization temperature (Th), when hydrocarbons in inclusions were cracked thermally, were experimentally evaluated. In the experiments, the hydrocarbon-inclusions in quartz were heated in an autoclave, and the Th between before and after heating were compared. In the experiments, the Th decreased after heating. The amount of decrease became greater as the heating temperature or the duration time or both increased. The experiments also revealed that the samples with higher Th showed a greater decrease after heating. Because the experiments have been performed in a closed system, mass transfer between inclusions and the enclosing medium was impossible. No volumetric changes in the hydrocarbon inclusions were observed after heating. Therefore, the temperature depression after heating should be caused by the pyrolysis of the hydrocarbons in the inclusions. In the Shin-Kumoide SK-1D well of the Niigata oil and gas field in Japan, the Th of hydrocarbon inclusions decreases from 73 to 30 °C between 4040 and 4810 m in depth successively. This temperature range is lower than the present formation temperature by from 60 to 140 °C, and shows a trend opposite to the normal geothermal gradient. Therefore, it should reflect the degree of the thermal cracking after trapping rather than the trapping temperature.

Deformation Band Control on Hydrocarbon Migration

ABSTRACT The hydrocarbon potential of sandstone reservoirs may be significantly affected by postdepositional compartmentation by grain-scale deformation mechanisms such as pressure solution, dislocation creep, microfracturing, and small-scale faulting. Deformation bands, sub 1-mm-thick elongate layers characterized by intense localized brittle fracturing, are important small-scale structural features controlling fluid flow in reservoir sands. They can act as fluid pathways or as barriers to fluid flow, depending on the timing relationship between hydrocarbon charge and deformation. Characterization of deformation-band scale, distribution, and timing of deformation relative to hydrocarbon charge is therefore critical in a full assessment of reservoir history. Integrated CL and UV studies of fluid inclusions from the Jeanne d'Arc Basin, Newfoundland, demonstrate that hydrocarbon charge predated deformation-band formation because oil-trapping quartz overgrowths are clearly cut by deformation bands. In contrast, porous, bitumen-rich sandstones from the Upper Old Red Sandstone of Caithness, NE Scotland, contain hydrocarbon inclusions trapped in quartz overgrowths that formed after deformation. Detailed petrographic work and CL imaging of these Old Red Sandstone samples demonstrates that hydrocarbons are absent in cemented deformation bands and occur only in undeformed sandstone pores and late quartz overgrowths. Post-deformation hydrocarbon migration pathways were thus constrained by effectively sealed deformation bands. In a third example, from the Jurassic of Skye, there is evidence for hydrocarbons in early (pre-band) cements, entrainment of hydrocarbons during band development, and a later pore-filling oil charge, indicating a complex relationship between the migration history and the bands.

Structural Studies and Computer Simulation of the Inclusion of Aromatic Hydrocarbons in a Zinc 2,6-Naphthalene Dicarboxylate Framework Compound

We have examined the structural response of a zinc 2,6-naphthalene dicarboxylate framework solid, isostructural with MOF-105, to the inclusion during crystallization of dimethylformamide, benzene, toluene, and p-xylene. These compounds, which are made up of a stacked arrangement of four-connected layers, crystallize in the space group P21/c with [Zn2(ndc)2(DMF)2]·1.6DMF (1), a = 8.075(1) Å, b = 16.891(2) Å, c = 12.673(2) Å, β = 92.90(1)°, [Zn2(ndc)2(DMF)2]·C6H6 (2) a = 8.340(2) Å, b = 15.660(4) Å, c = 13.008(4) Å, β = 91.340(5)°, [Zn2(ndc)2(DMF)2]·C7H8 (3), a = 8.183(2) Å, b = 16.245(3) Å, c = 12.920(3) Å, β = 91.976(4)°, and [Zn2(ndc)2(DMF)2]·C8H10 (4), a = 7.973(2) Å, b = 16.946(3) Å, c = 12.922(3) Å, β = 92.798(4)°. The structure is found to include p-xylene with high selectivity from mixtures of xylene isomers. In the presence of only o- or m-xylene as an additive, the structure does not crystallize. The mobility of fully deuterated benzene and toluene within compounds 2 and 3 over the temperature ranges 123−294 and 173−294 K, respectively, has been measured by 2H NMR using the quadrupole echo technique. Benzene is found to execute rapid hopping around its C6 axis over the entire temperature range studied with an activation energy of 6(1) kJ mol-1. The only motion of the toluene is rapid rotation of the −CD3 group. Computational modeling of the structures successfully reproduces the crystal structures and the changes in unit cell parameters and indicates that the binding energies of m-xylene within the structure are less favorable than those for p-xylene, predominantly as a result of the distortion of the framework required to accommodate the m-xylene. These lower binding energies explain the high selectivity for the uptake of p-xylene during crystallization.

Microspectrofluorimetric and microthermometric evidence for variability in hydrocarbon fluid inclusions in quartz overgrowths: implications for inclusion trapping in the Alwyn North field, North Sea

Hydrocarbon inclusions trapped in quartz cement from Alwyn North field sandstones of well 3/9a-6 (North Sea) have been analyzed using microthermometric and microspectrofluorimetric methods. They are two-phased, with consistent gas–oil ratios, and mainly occur along the detrital grain–overgrowth boundary. Their homogenization temperatures vary from 60 to 129 °C with a great variability within a single fluid inclusion assemblage (up to 40 °C). The fluorescence colour of the hydrocarbon inclusions has been characterized using a microspectrofluorimeter which allows the analysis of very small inclusions (>1.7 μm) with good reproducibility. Hydrocarbon inclusions display large variations in their fluorescence colour, converted in chromaticity coordinates, even within a single fluid inclusion assemblage. Moreover, they are concentrically distributed within the detrital grain–overgrowth interface. According to the relationship between API gravity and fluorescence colour, established with reference to crude oils from Alwyn North field, this observation is interpreted as representing compositional variations. Such compositional variability in a single fluid inclusion assemblage could result from either the progressive entrapment of oils in which API gravity evolves through time, and/or the fractionation of hydrocarbons at the time of trapping.