Ratios Of Hydrocarbons Research Articles

Microbial Biodegradation of Paraffin Wax in Malaysian Crude Oil Mediated by Degradative Enzymes.

The deposition of paraffin wax in crude oil is a problem faced by the oil and gas industry during extraction, transportation, and refining of crude oil. Most of the commercialized chemical additives to prevent wax are expensive and toxic. As an environmentally friendly alternative, this study aims to find a novel thermophilic bacterial strain capable of degrading paraffin wax in crude oil to control wax deposition. To achieve this, the biodegradation of crude oil paraffin wax by 11 bacteria isolated from seawater and oil-contaminated soil samples was investigated at 70°C. The bacteria were identified as Geobacillus kaustophilus N3A7, NFA23, DFY1, Geobacillus jurassicus MK7, Geobacillus thermocatenulatus T7, Parageobacillus caldoxylosilyticus DFY3 and AZ72, Anoxybacillus geothermalis D9, Geobacillus stearothermophilus SA36, AD11, and AD24. The GCMS analysis showed that strains N3A7, MK7, DFY1, AD11, and AD24 achieved more than 70% biodegradation efficiency of crude oil in a short period (3 days). Notably, most of the strains could completely degrade C37–C40 and increase the ratio of C14–C18, especially during the initial 2 days incubation. In addition, the degradation of crude oil also resulted in changes in the pH of the medium. The degradation of crude oil is associated with the production of degradative enzymes such as alkane monooxygenase, alcohol dehydrogenase, lipase, and esterase. Among the 11 strains, the highest activities of alkane monooxygenase were recorded in strain AD24. A comparatively higher overall alcohol dehydrogenase, lipase, and esterase activities were observed in strains N3A7, MK7, DFY1, AD11, and AD24. Thus, there is a potential to use these strains in oil reservoirs, crude oil processing, and recovery to control wax deposition. Their ability to withstand high temperature and produce degradative enzymes for long-chain hydrocarbon degradation led to an increase in the short-chain hydrocarbon ratio, and subsequently, improving the quality of the oil.

Effect of hydrogen partial pressure on catalytic reforming process of naphtha

The semi catalyst regenerative commercial naphtha catalytic reforming of Kaduna Refinery, Nigeria is modelled and simulated with general process modelling systems (gPROMS) model builder 5.0.0 which is a computational tool in modelling process and complex chemical engineering processes. The thermodynamic and kinetics parameters used are obtained from the referenced literature. The model was validated with data from literature and was used to simulate the commercial data of KRPC. Simulation results obtained were good compared with the plant and literature data and these results were used in monitoring the plant performance and the temperature and concentration profiles of the parafins, naphthenes and aromatics as they change across the reactor bed heights. Hydrogen partial pressure effect on the product quality, aromatics and product yields were studied. It was found that an increase in hydrogen hydrocarbon ratio of 5.6 to 7.4, aromatics yield decrease from 58.5% to 55.5%, reformate yield increases from 52,805 kg/h to 53,234.5 kg/h, hydrogen yield increases from 10,955 kg/h to 14,515 kg/hr. The percentage weight of coke on the catalyst decreases with increase in hydrogen hydrocarbon ratio of 5.6 to 7.4 from 1.8%wt to 1.289%wt, 3.297%wt to 2.415%wt, 4.457%wt to 3.351%wt and 5.1850%wt to 3.983%wt for reactors 1, 2, 3 and 4 respectively.

Extraction of essential oil from methyl cinnamate basil (Ocimum canum Sims) with high yield in a short time using enzyme pretreatment.

This research was carried out to evaluate the effect of viscozyme pre-treatment followed by hydrodistillation (E-HD) on extraction yield, extraction time and quality of methyl cinnamate basil (O. canum) oil. The viscozyme, as a multienzyme acting on cell wall, was used at different concentrations (0.5% and 1%, v/w) for 30, 60 and 90min at 50 °C and pH 5 before hydrodistillation (HD). Oxygenated monoterpenes/monoterpene hydrocarbons ratio was used as a quality index for the obtained essential oil. Enzymatic pretreatment at 1% enzyme concentration for 90min followed by HD increased yield of essential oil by 44.5% with high quality index and decreased HD time from 180 to 30min. Thirty-nine volatile compounds, comprising > 99% of the essential oil were identified and quantified by Gas Chromatography Mass Spectrum (GC-MS). The major components of essential oil were (E)-methyl cinnamate, camphor, trans-β-caryophyllene and 1,8-cineole. Results confirm the effectiveness of the enzyme pretreatment, which enhance extraction of O. canum essential oil in a short time, with a high quality.

Diagnostic ratios of individual polycyclic aromatic hydrocarbons for their identifiaction in soils of power station

the article presents the study of the content of organic ecotoxicants – polycyclic aromatic hydrocarbons in the soils of the impact zone of the energy industry enterprise of Novocherkasskaya power plant (NPP) – the largest producer of electricity in southern Russia. The study showed a high level of total PAH content in the soils of the studied territory, compared to the background territories. The degree of contamination of soils in the zone of influence of the energy industry enterprises with Benzo(a)pyrene is classified as highly contaminated soils. The diagnostic relationships of individual PAHs showed a significant effect of the NchGRES on the soils of sites located along the line of the prevailing wind from NPP. For these sites, the pyrogen-coal origin of PAHs was established.

Solar methanol by hybridizing natural gas chemical looping reforming with solar heat

Liquid sunshine is a concept for converting solar energy into liquid fuel. Methanol is an attractive candidate as the liquid fuel due to the long-period experiences in large-industrial scale of methanol production. Solar driven chemical looping process is considered as a way to produce raw materials of methanol synthesis. To achieve the transformation from solar energy to the chemical energy of liquid fuel, an integrated system based on the solar-driven chemical looping process using methane for methanol production is proposed. During the chemical looping process, solar heat is absorbed by the reaction to convert methane into syngas with a reasonable hydrocarbon ratio. The syngas as raw materials would be sent into a two-tower tandem methanol synthesis sector. The obtained crude methanol would be rectified and stored as the product. A preliminary parameter analysis helps to get the optimal reaction conditions of the chemical looping process, as the reaction temperature of 600 °C, CH4-to-NiO ratio of 1.25 and H2O-to-CH4 ratio of 0.7. In addition, the system was simulated and the energy analysis and exergy analysis are examined. The results show that energy efficiency is about 62%, and exergy efficiency is about 65%. In addition, the stored chemical energy in methanol can be released by employing solar energy again. The solar heat at around 250 °C driven methanol cracking process can be further released and coupled with an internal combustion engine for power generation. The net solar to electricity efficiency is evaluated and reaches around 23%. In this study, by solar-driven natural gas chemical looping process coupled with methanol synthesis, we would expect to provide a new pathway for further development of liquid sunshine.

High pressure rheological studies of methane hydrate slurries formed from water-hexane, water-heptane, and water-decane multiphase systems

High pressure rheological properties of methane hydrate slurries entail the high-pressure rheometer that can deliver a suitable mixing to form in situ methane hydrate from the multiphase system. However, the hydrate formation was extremely challenging in conventional cup and bob geometry due to its plane surface. In this work, modified Couette geometry has been used in a high pressure rheometer to study in situ formation and dissociation of methane hydrate slurries formed from multiphase water-hexane (C6H14), water-heptane (C7H16) and water-decane (C10H22), with varying water-to-liquid hydrocarbon ratios (50:50, 30:70 v/v). Rheological properties such as viscosity, flow curve measurements, viscoelastic properties have been measured during hydrate formation and dissociation. Transient viscosity measurements are carried out at 10 MPa and 275.15 K at a shear rate of 1000 s−1. It was observed that the viscosity increases significantly during hydrate induction. Viscosity profile has shown bobbing behavior during the course of hydrate formation indicating in situ morphological changes (agglomeration and breakage of hydrate crystals) during hydrate formation. Flow curves indicate strong shear thinning behavior. Viscosity profile of methane hydrate slurries were also observed for each case during the hydrate dissociation using thermal stimulation. The peak in the viscosity has been identified near hydrate equilibrium condition during dissociation. Dynamic viscoelastic properties indicate solid behavior of methane hydrate slurries. The present study provides significant contribution on the rheology of methane hydrate slurries formed from multiphase systems in the context of flow assurance applications.

Formation of Organic Deposits in Model Petroleum Systems

The formation of organic deposits in model petroleum-containing systems of various compositions has been studied. Introduction of asphaltene–resin substances into a model paraffin system reduces the amount of precipitated wax deposit to 40 wt %; significantly changes the ratio of liquid and solid hydrocarbons in the n-alkane composition of the deposits, shifting the distribution maximum towards a lower molecular weight; and substantially reduces the mechanical strength. In the model paraffin system in the presence of resins and asphaltenes, which contain a greater amount of condensed aromatic structures and a smaller amount of paraffin structures, a precipitate is formed with an increased proportion of the liquid phase. The deposits are characterized by lower strength of the crystal lattice and, hence, a decreased value of ultimate shear stress.

Geochemical implications from direct Rock-Eval pyrolysis of petroleum

The maximum burial depth and thermal maturity of a hydrocarbon source rock controls the generation of petroleum, and data on rock maturity are necessary for an understanding of a petroleum system. Rock-Eval pyrolysis is an established method to assess the hydrocarbon generation potential, the type of organic matter (kerogen type), but also the thermal maturity of hydrocarbon source rocks. Data on the thermal maturity of source rocks and/or of the generated hydrocarbons are, however, often lacking either, because (i) the source rock itself is not available or (ii) today’s maturities cannot be directly linked to a generated petroleum, because petroleum generation and expulsion may have taken place at an earlier and less mature stage of the source rock. Indirect records of source rock maturities can be inferred from the physical properties of petroleum (e.g, API gravity), from biomarker abundances or from individual hydrocarbon ratios (including biomarkers). Using an adapted direct Rock-Eval pyrolysis approach for petroleum samples we present data from oils from the BGR petroleum archive. We distinguish between two hydrocarbon release-stages during Rock-Eval pyrolysis of which the first represents a vaporizable mid-molecular (S1oil) fraction (< 400 °C; n-C15 ->n-C40) and the second (S2oil) fraction (> 400 °C; >n-C40) most likely represents a residual higher-molecular weight petroleum fraction generating hydrocarbons by pyrolytic destruction. Using this program, we calculate an “Oil Composition Index” (OCI). Unless processes like biodegradation, evaporation or migration can affect OCI values, in a relatively well known petroleum system without major influences from these processes (the Gifhorn Trough in the Lower Saxony Basin [LSB] in Northern Germany), our data indicate that maturity of the source rock during expulsion is key for OCI. Application of Rock-Eval on a large set of oils from the entire LSB demonstrates that OCI values further hold information on the kerogen-type of the source rock (Wealden vs. Posidonia shales).

The effect of co-feeding ethene on Fischer-Tropsch synthesis to olefins over Co-based catalysts

Understanding the secondary reactions of olefins in Fischer Tropsch Synthesis (FTS) is crucial for enhancing olefin selectivity in Fischer Tropsch to Olefin (FTO) reaction. Equimolar ethene towards CO was used as a probe to be cofed into the syngas (H2: CO = 2) to study the effect on the product distribution over cobalt-based catalysts supported on γ-alumina, α-alumina and carbon nanotube (CNT), respectively. The experiments were performed at T = 210 °C; Ptot = 1.85 bar, PCO = 0.11 bar; PH2 = 0.22 bar; PC2H4 = 0 or 0.11 bar with Ar as the balance. On all three catalysts, ethene co-feeding at this concentration inhibited CO conversion and the products were mainly from ethene. The products showed similar Anderson-Schulz-Flory (ASF) distribution as typical for FTS products. Ethene co-feeding can both enhance the chain growth probability and significantly increase the O/P ratio of C3-C6 hydrocarbons. An isotopic switch from 12CO/H2 /Ar→13CO/H2/C2H4/Kr proved that ethene can hydrocrack to C1 intermediates and be incorporated into the growing chain. On the other hand, the hydrogenation activity can be significantly suppressed due to the H2 scavenging effect and possibly competitive adsorption with H2.

Critical Role of Confinement in the NMR Surface Relaxation and Diffusion of n-Heptane in a Polymer Matrix Revealed by MD Simulations.

The mechanism behind the NMR surface-relaxation times (T1S,2S) and the large T1S/T2S ratio of light hydrocarbons confined in the nanopores of kerogen remains poorly understood and consequently has engendered much debate. Toward bringing a molecular-scale resolution to this problem, we present molecular dynamics (MD) simulations of 1H NMR relaxation and diffusion of n-heptane in a polymer matrix. The high-viscosity polymer is a model for kerogen and bitumen that provides an organic "surface" for heptane. Diffusion of n-heptane shows a power-law dependence on the concentration of n-heptane (ϕC7) in the polymer matrix, consistent with Archie's model of tortuosity. We calculate the autocorrelation function G(t) for 1H-1H dipole-dipole interactions of n-heptane in the polymer matrix and use this to generate the NMR frequency (f0) dependence of T1S,2S as a function of ϕC7. We find that increasing molecular confinement increases the correlation time, which decreases the surface-relaxation times for n-heptane in the polymer matrix. For weak confinement (ϕC7 > 50 vol %), we find that T1S/T2S ≃ 1. Under strong confinement (ϕC7 ≲ 50 vol %), we find that T1S/T2S ≳ 4 increases with decreasing ϕC7 and that the dispersion relation T1S ∝ f0 is consistent with previously reported measurements of polydisperse polymers and bitumen. Such frequency dependence in bitumen has been previously attributed to paramagnetism; instead, our studies suggests that 1H-1H dipole-dipole interactions enhanced by organic nanopore confinement dominate the NMR response in saturated organic-rich shales.

Hydroconversion of Perhydrophenanthrene over Bifunctional Pt/H‐USY Zeolite Catalyst

AbstractIn petroleum refining, middle distillates are produced via hydroisomerization/hydrocracking processes using bifunctional catalysts often containing ultrastable Y (USY) zeolite. Petroleum fractions serving as feedstock for hydrocracking processes contain a majority of (poly)cyclic hydrocarbon molecules. Few studies on reaction mechanisms of hydrocracking of such polycyclic compounds are available. In this study the tricyclic phenanthrene molecule was used as model compound. Phenanthrene was hydrogenated on a Pt/alumina pre‐catalyst to perhydrophenanthrene, and subsequently hydrocracked over Pt/H‐USY zeolite. The feed consisted of 3 wt.% phenanthrene dissolved in n‐heptane. The reaction was performed at 280 °C and 60 bar, with a molar H2 to total hydrocarbon ratio of 7 mol/mol. The reaction products were analyzed using GCxGC‐FID/MS. This detailed analysis enabled identification of the reaction scheme involving skeletal isomerization, ring opening and fragmentation. New mechanistic insight is gained on relative reactivities of bridged and non‐bridged tricyclic naphthenes. Preferential hydrocracking routes were identified. The study provides insight in the products to be expected from polycyclic hydrocarbon isomerization and hydrocracking.

Comprehensive investigation of the effect of adding phosphorus and/or boron to NiMo/γ-Al2O3 catalyst in diesel fuel hydrotreating

In order to comprehensively investigate the effect of boron (B) and phosphorous (P) promoters on the catalytic performance of a hydrodesulfurization catalyst (NiMo/γ-Al2O3, separate or simultaneous addition of the two promoters and the method of their addition to the catalyst solution or support have been studied by physical, chemical and reactor evaluation of nine synthetic catalysts using a diesel fuel feed containing 11,500 ppm of sulfur and 250 ppm of nitrogen. For better evaluation of the synthetic catalysts, their surface area, morphology, crystalline structure, regeneration temperature and acidity have been studied by ICP, XRD, Raman, FTIR, TPR, BET, FESEM and TPD analyses. Reactor evaluations have been performed at a temperature of 340 °C, pressure of 65 bar, LHSV of 0.8 h−1 and hydrogen to hydrocarbon ratio of 250 and the amounts of sulfur and nitrogen resulting from each catalyst have been determined. The catalysts showed very different performances in the absence or presence of P and B promoters in the desulfurization and hydrodenitrogenation processes. The presence of P and B promoters seems to be necessary in the hydrodesulfurization process. However, the presence of P and B promoters in the HDN process depends on the type and method of the promoter addition.

Factors Controlling the Unusual Oil Composition Distribution in the Bangestan Reservoir, Dezful Embayment, SW Iran

Abstract —Petroleum geochemical characteristics are a major parameter of hydrocarbon field development. The present study is an attempt to decipher the unusual Bangestan (Cretaceous age) oil distribution throughout the Ahvaz oil field, SW Iran, based on the SARA test and GC–MS analysis of selected oil samples. The results indicated that all analyzed oils belong to the paraffinic group. Hydrocarbon indicators, such as tricyclic triterpane C22/C21 (high), C24/C23 and C26/C25 (low), and hopane C31R/C30 (high) ratios and C25/C26 ratio vs. C25/C26 tet ratio, show that these oils are sourced from carbonate–marl rocks. The high saturation/aromatic hydrocarbon ratio in these oil samples may be related to long migration or high maturity. The biomarker variation exhibits a marine environment for the source rocks deposition. The observed oil maturity trend is showing a good correlation with the prevailing geothermal gradient and possible basement faults and fractured system. The increasing oil maturity in the eastern part of the field may be related to a heat flow anomaly. It seems that the area around well C (the area of wells C, D, or E) can be considered a petrochemical separator of fluids for two sides of the field. Therefore, it can be concluded that the observed petrochemical pattern is a complicated response of several factors: the presence of a palaeohigh, basement-controlled faults, petroleum source rocks, fractured system, and geothermal gradient variation in this deep reservoir.

Source Rock Characterization of Silurian Tanezzuft and Devonian Awaynat Wanin Formations the Northern Edge of the Murzuq Basin, South West Libya

Drill cutting samples (n = 92) from the Devonian Awaynat Wanin Formation and Silurian Tanezzuft Formation, sampled from three wells F1, G1 and H1, locate in the northern edge of the Murzuq basin (approximately 700 kilometers south of Tripoli). The studied samples were analyzed in the objective of their organic geochemical assessment such as the type of organic matter, depositional conditions and thermal maturity level. A bulk geochemical parameters and precise biomarkers were estimated, using chromatography-mass spectrometry (GC-MS) to reveal a diversity of their geochemical characterizations. The rock formations are having varied organic matter contents, ranged from fair to excellent. The total organic carbon (TOC) reached about 9.1 wt%, ranging from 0.6 to 2.93 wt% (Awaynat Wanin), 0.5 to 2.54 wt% (Tanezzuft) and 0.52 to 9.1 wt% (Hot Shale). The cutting samples are ranged oil-prone organic matter (OM) of hydrogen index (HI) ranged between 98 –396 mg HC/g TOC, related kerogen types are type II and II/III, with oxygen index (OI): 6 - 190 with one sample have value of 366 mg CO2/g. Thermal maturity of these source rocks is different, ranging from immature to mature and oil window in the most of Tanezzuft Formation and Hot Shale samples, as reflected from the production index data (PI: 0.08 - 034). Tmax and vitrinite reflectance Ro% data (Tmax: 435 – 454 &amp; Ro%: 0.46 - 1.38) for the Awaynat Wanin. Biomarker ratios of specific hydrocarbons extracted from represented samples (n = 9), were moreover used to study thermal maturity level and depositional environments. Pristine/Phytane (Pr/Ph) ratios of 1.65 - 2.23 indicated anoxic to suboxic conditions of depositional marine shale and lacustrine source rock.

Geochemical Characterization of Two Niger Delta Crude Oils and Their Mixtures II: Correlation of Bulk Properties and Aliphatic Hydrocarbons

Correlations of bulk geochemical properties such as density, API gravity, saturates, aromatics, resins and asphaltenes (SARA) compositions, aliphatic hydrocarbons (from nC8 to nC38) and their diagnostic ratios (Pr/Ph, Pr/nC17 and Ph/nC18) were evaluated for two Niger Delta crude oils (samples A and F) and their mix at different proportions of 4:1, 3:2, 2:3 and 1: 4 (samples B, C, D and E respectively). Pearson correlation showed strong relationships (> 0.99) between sample pairs in their bulk geochemical properties and diagnostic ratios, but variable relationships (0.20 - 0.85) in the aliphatic hydrocarbons which increased with increase in the proportion of sample F. Assessment of aliphatic hydrocarbon compositions by hierarchical cluster analysis (HCA) showed two major groups of clearly differentiated clusters with negative similarity and their plots revealed the aliphatic hydrocarbon compositions increased/decreased from samples A to F and exhibited variable strength for correlation of the oil samples. Plots of ratios of the aliphatic hydrocarbons were used to depict the geochemical compositional variations of the oil samples. Coefficient of determination (R²) of the plots indicate the ratios C 14/C14 + C25, C15/C15 + C24 and C17/C17 + C23 fits well and could account for 99.4%, 99.3% and 99.2% of the geochemical compositional variations of the two Niger Delta crude oils and their proportional mix. The results suggest these aliphatic hydrocarbon ratios could be useful for estimating the composition of two Niger Delta crude oils in their mix.

Isotopic difference between hydrate-bound and sediment gases retrieved at Lake Baikal

The objective of our study is to clarify the formation process of natural gas hydrates in the sublacustrine sediments of Lake Baikal, and we are now compiling data on stable isotope ratios of hydrocarbons in hydrate-bound and sediment gases, which have been collected in the framework of collaboration between Russia, Belgium and Japan for 15 years. The results obtained in the VER19-03 cruise at the southern and central Baikal basins were summarized in this report. Comparison of stable isotope ratios of hydrate-bound and sediment gases at the same core and depth was performed. The methane carbon isotope ratio of the hydrate-bound gas was 1 to 2 smaller than the sediment gas. The methane hydrogen isotope ratio was similarly about 5 smaller. These results can be explained generally by the isotopic fractionation of methane. In contrast, some sediment cores from pockmarks in the center of the mud volcano showed small or reversed differences in methane carbon isotope ratios, as well as small differences in methane hydrogen isotope ratios, suggesting that dissociation of gas hydrate is occurring at that point.

Influence of Vehicular Emissions (NO, NO2, CO and NMHCs) on the Mixing Ratio of Atmospheric Ammonia (NH3) in Delhi, India.

Mixing ratios of atmospheric ammonia (NH3), nitric oxide (NO), carbon monoxide (CO), nonmethane hydrocarbons (NMHCs), and methane (CH4) were measured to investigate the vehicular emissions, which are a dominant source of atmospheric NH3 in urban sites of Delhi, India from January 2013 to December 2014. The annual average mixing ratios of NH3, NO, CO, NMHCs, and CH4 were 21.2 ± 2.1ppb, 21.2 ± 6.1ppb, 1.89 ± 0.18ppm, 0.67 ± 0.21ppm and 3.11 ± 0.53ppm, respectively. Considering NO as a tracer of vehicular plume, ambient NH3 was correlated with NO during peak traffic hour in the morning (7:00-10:00h) and evening (17:00-19:00h) and observed significant positive correlation between them. Result reveals that the mixing ratio of atmospheric NH3 significantly positive correlated with traffic related pollutants (NO, CO, and NHHCs) during all the seasons (winter, summer, and monsoon). During winter, the average mixing ratio of atmospheric NH3 was increased by 1.2-3.5ppb in the morning peak hour, whereas increased by 0.3-1.6ppb in the evening peak hour. Similarly, an increase in NH3 mixing ratio was observed during summer (morning: 1.2-2.7ppb and evening: 1.5-1.6ppb) and monsoon (morning: 0.4-3.6ppb and evening: 0.9-1.4ppb) seasons. The results emphasized that the traffic could be one of the dominant source of ambient NH3 at the urban site of Delhi, as illustrated by positive relationships of NH3 with traffic related co-pollutants (NO, COand NMHCs).

Petroleum hydrocarbons in semipermeable membrane devices deployed in the Northern Gulf of Mexico and Florida keys following the Deepwater Horizon incident.

The Deepwater Horizon (DWH) oil spill from April to July of 2010 contaminated Gulf of Mexico waters through release of an estimated 4.1 × 106 barrels of oil. Beginning in June of 2010, semipermeable membrane devices (SPMDs) were deployed near areas with sensitive marine habitats (Alabama Alps and Western Shelf) potentially exposed to that oil. Elevated TPAH50 concentrations, flux rates and similarity of histograms and diagnostic ratios for polycyclic aromatic hydrocarbons (PAH) from SPMDs to weathered floating oil collected during the DWH spill indicates the Alabama Alps habitats were affected. While not affected by oil from the DWH spill, the temporal pattern of PAH contamination of SPMDs deployed near the Western Shelf between July 2010 and March 2011 could indicate prevailing currents affected contaminant transport to the Western Shelf Area (East and West Flower Garden, Sonnier, and Stetson Banks) from non-DWH sources, including oil and gas exploration, shipping, and Mississippi River effluent.

Temperature-depth control of petroleum occurrence in the sedimentary section of the South Caspian basin

This study analyses the temperature and depth control of well productivity (oil and gas), density of hydrocarbons (HC) and gas/liquid HC ratio (GLR) of petroleum fields in the South Caspian Basin (SCB). The database includes more than 700 field data from 54 onshore and offshore fields, which were processed to provide graphical and statistical analysis using standard computer programs. It was established that the peak of initial production and proven oil reserves falls in the temperature range 50–70 °C. The oils of this interval are characterized by medium (about 890 kg/m3) and light (about 806 kg/m3) density. The maximum condensate and gas production are in the temperature range 100–120 oС, associated with the discovery and operation of large gas condensate fields in the deepwater part of the SCB. Liquid HC are represented in this temperature interval by “volatile” oils and condensates with an average density of 777–802 kg/m3. Low values of GLR are typical for temperatures below 70 °C, associated both with poor gas conservation conditions and relatively high volumes of oil production. The carbon isotope composition of methane indicates an exclusively catagenetic (thermal) origin at temperatures >50 °C and both catagenetic and mixed (microbiological-catagenetic) at temperatures <50 °C. Based on the results, a forecast is provided for the discovery of new commercial HC accumulations.

Simulation of thermochemical sulfate reduction of gaseous hydrocarbons in Wushenqi area, Ordos Basin, China

Prediction of the H2S distribution is critical to lower the risks during petroleum exploration and development in the exploration area. Natural gas of two wells produced from the Ordovician Majiagou Formation Ma5-6 section from Wushenqi area show great difference in H2S content. To investigate whether the different thermal maturity of the two wells contributes to the different H2S content, the thermal mature history and transformation ratio of gas hydrocarbons and sulfate into H2S and CO2 through TSR (thermochemical sulfate reduction) were simulated by using Petromod 2016. Simulation result shows that difference of thermal maturity of the two wells is about 0.6%. Propane and butane have all been consumed to generate H2S. The transformation ratio of ethane is higher for the well with higher thermal maturity. The high H2S content in the well with high thermal maturity and no H2S in the well with lower thermal maturity was not caused by the different thermal maturity. Some other geological factors should be considered.