Compounds In Crude Oil Research Articles

Surface and Interfacial Tension Behavior of Salt Water Containing Dissolved Amphiphilic Compounds of Crude Oil: The Role of Single-Salt Ionic Composition

A detailed investigation into the effect of dissolved amphiphilic compounds of crude oil in salt water on its surface tension/interfacial tension (ST/IFT) behavior has been conducted in this paper. To simulate water–oil contact during water injection into oil reservoirs, 16 single-salt aqueous solutions of NaCl, CaCl2, and Na2SO4 having ionic strengths of up to 2.0 M were mixed with a natural acidic–basic crude oil. The mixing was performed by a rocking mechanism in a visual pressure–volume–temperature cell at an elevated temperature. After the mixing process, two phases were completely separated from each other using a high-temperature centrifuge. Finally, in addition to pH measurements, the air–water ST and decane–water IFT of salt water were measured using the pendant-drop method. The results reveal that the dissolution of crude oil amphiphilic compounds, especially the acidic or basic compounds, in salt water can considerably decrease its ST/IFT. It seems that there is the same optimal ionic strength ...

Quantitative and Qualitative Analysis of Three Classes of Sulfur Compounds in Crude Oil.

Owing to the environmental hazards arising from sulfur-containing combustion products, strong legal regulations exist to reduce the sulfur content of transportation fuels down to a few ppm. With the ongoing depletion of low-sulfur crude oil reservoirs, increased technological efforts are needed for crude oil refining to meet these requirements. The desulfurization step is a critical part of the refining process but partly suffers from the recalcitrance of certain species to sulfur removal and the inability to quantitatively understand the behavior of individual compound classes during the process. We herein present a new and simple approach for the parallel quantification of three different classes of sulfur species present in crude oils by LC separation and on-line detection and quantification by ICP-MS/MS. This approach will help to estimate the amount of recalcitrant species and thus facilitate the optimization of desulfurization conditions during fuel production.

Size Distributions of Sulfur, Vanadium, and Nickel Compounds in Crude Oils, Residues, and Their Saturate, Aromatic, Resin, and Asphaltene Fractions Determined by Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry

The size distributions of sulfur (S), vanadium (V), and nickel (Ni) compounds in four crude oils, two residues, and their saturate, aromatic, resin, and asphaltene (SARA) fractions were determined using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show trimodal distributions of V, Ni, and S compounds in the crude oils and residues. V and Ni compounds are present in both resins and asphaltenes. Trimodal distributions are clearly apparent in the resins but not apparent in the asphaltenes. In the latter, the predominant compounds have a high molecular weight (HMW), even when the solution of asphaltenes is diluted by 40000-fold. In the resins, compounds with a medium molecular weight (MMW) were expected; however, HMW compounds were observed, indicating that nanoaggregates or large molecules exist in both the asphaltenes and resins. Low-molecular-weight (LMW) compounds are predominantly present in the resins and do not repr...

Interpreting Chemical Structures of Compounds in Crude Oil Based on the Tandem Mass Spectra of Standard Compounds Obtained at the Same Normalized Collision Energy

In this study, the tandem mass spectra of 25 standard compounds, obtained at a normalized collision energy of 50, were used to investigate the structures of crude oil. The product ion distributions of these standard compounds were dependent on the number and length of their alkyl side chains. Long alkyl side chains (CnH2n, n ≥ 5) were easily lost during molecular collision, leaving behind methyl groups on the aromatic cores. In contrast, compounds with short interlinking alkyl chains (CnH2n, n ≤ 1) were not significantly fragmented, and a decrease in the double bond equivalent (DBE) value was observed when compounds had saturated rings. Based on the derived observations, the possible structures of S1-class compounds with DBE values of 6, 7, 8, and 9 were suggested. It was also determined that, in the tandem mass spectra of crude oil fractions, (1) a series of peaks separated by CH2 groups were generated from isomers with different numbers of alky side chains, (2) the number of methyl groups left after mol...

Evolution of Acidic Compounds in Crude Oil during In Situ Combustion

In situ combustion (ISC) process has drawn more and more attention in the development of heavy oil reservoirs as a result of its high recovery efficiency. Although numerous studies have been reported that oil properties exhibit significant changes during the combustion process, the reaction mechanisms and evolution of oil components are still not well understood. In this work, the compounds of produced oils collected from a three-dimensional simulated production model (container) at different duration times after combustion being initiated and the original oil were characterized at the molecular level using gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both aromatic and acidic components were analyzed. The aromatic components showed relatively more stable characteristics than those of acidic components, and no obvious changes in aromatic compound distributions were observed by the positive ion atmospheric pressure photoionization (APPI) FT-ICR MS analysis. Small aliphatic acids were detected in the ISC oils, which were responsible for the high total acid numbers (TANs). The acidic Ox (x = 1–3) compounds, which have major contributions to the increase in TAN, were generated in greater abundances compared to that of the original crude oil. The carbon number distributions of the O1 and O2 classes in the produced oils significantly shifted to a lower carbon number region, with the dominant distribution from 15–40 at the initial state to 10–30 at the longest duration time. The double bond equivalent (DBE) values decreased during the combustion process. The generated acidic O1 components with DBE values less than 4 were also found in negative ion electrospray ionization (ESI) analysis, indicating the oxidation of hydrocarbons to alcohols.

Development of a chromatographic methodology for the separation and quantification of V, Ni and S compounds in petroleum products

The separation, quantification and identification of V, Ni and S and their compounds in crude oils or their refining fractions is a subject of great interest for the oil industry. Such elements and heterocompounds are harmful to industry catalysts and might be toxic to living organisms. This work presents a methodology based on the following two-step approach: (1) A chromatographic column separation is first performed on a silica gel column to produce six fractions from the initial crude oils or petroleum products, such as vacuum residues (VRs). This separation is achieved by varying the polarity of the elution solvent systems used. (2) The separated fractions are then studied using gel permeation chromatography (GPC) coupled to an inductively coupled plasma high-resolution mass spectrometry (ICP-HRMS).Additionally, the use of ultraviolet (UV)-visible spectroscopy allows for the identification of fractions containing porphyrinic-type compounds by detecting the Soret band at 405nm. The objective of this two-step approach is to deduce both the distribution and nature of Ni and V complexes within the sample. This method reduces the complexity of petroleum matrices and produces simpler fractions that can be used for further studies.

Genesis and distribution of hydrogen sulfide in deep heavy oil of the Halahatang area in the Tarim Basin, China

As the largest oil-and-gas-bearing basin in China, the Tarim Basin contains rich oil and gas resources buried deep underground. In recent years, large oil fields have been discovered in the Halahatang area of the northern Tarim Basin. The reservoir is buried 6000–7300 m underground. This reservoir is dominated by the Ordovician carbonate rocks, and the crude oil is mainly heavy oil. As a crude oil-associated gas, the natural gas generally contains hydrogen sulfide (H2S). The heavy oil in this region is the deepest buried heavy oil found in the world. H2S is also associated with the deepest buried natural gas. The burial, preservation and degree of biodegradation of a paleo-reservoir can be used to predict the distribution of H2S. According to research findings, there is a clear planar distribution pattern of H2S content: high in the east and north, and low in the west and south. We compared the physical properties of crude oil and the analysis of the composition of natural gas and isotopes, biomarker compounds of crude oil and groundwater. We find that the content of H2S in natural gas bears some relation to the physical properties and degree of biodegradation of crude oil. Crude oil density, sulfur content, colloid, and asphaltene have positive correlations with H2S content in natural gas. The formation of H2S is controlled by the degradation and densification of crude oil. Crude oil densification can lead to an increase of the sulfur content. The rise in the temperature of the reservoir resulting from the depth of burial causes the thermal decomposition of sulfur compounds to produce H2S. The generation of H2S by the thermal decomposition of sulfur compounds is confirmed by data on sulfur isotopes. The distribution of H2S can then be predicted based on the burial conditions of the paleo-reservoir and the degree of biodegradation. In the south Rewapu of the Halahatang area, the thick cap rock of the Ordovician oil reservoir was preserved well in the late Hercynian Period, without undergoing biodegradation. The oil is mainly normal oil and light oil. Sulfur content in the crude oil is quite low, making it impossible to generate a large amount of H2S in the later stages of deep burial.

Gas purge microsyringe extraction coupled to comprehensive two-dimensional gas chromatography for the characterization of petroleum migration

Several nitrogen-containing compounds play important roles as molecular indicators in petroleum migration but are usually absent or present at very low concentrations, especially when oils have been subjected to severe biodegradation or water washing. In this study, we use thiophenic compounds (such as dibenzothiophene and its alkylated homologs) as alternative oil migration indicators because they appear to exhibit strong absorption/adsorption interactions with solid organic/mineral phases due to their molecular structure, similar to organic nitrogen compounds. To improve the detection sensitivity of trace analytes, a gas purge microsyringe extraction (GP-MSE) device was developed and coupled to comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS) for the simultaneous analysis of biomarkers and trace nitrogen- and sulfur-containing compounds in crude oils. Twenty oil samples collected from the Hashan region of the Junggar Basin in China were classified as having different biodegradation levels and confirmed to be primarily sourced from the Fengcheng Formation with similar maturities and depositional environments. In addition to the commonly used oil migration parameters derived from the distribution of organic nitrogen compounds, several geochemical parameters based on the ratios of 4,6-/1,4-, 4,6-/3,6- and 4,6-/2,7-dimethyldibenzothiophenes (DMDBTs) were proposed to indicate the oil migration direction. The conclusions on oil migration obtained from organic nitrogen compounds and DMDBTs were in good agreement and further supported by other geological evidence. An oil migration model for the region was developed by combining the geochemical data with the geological information.

Variations of Acidic Compounds in Crude Oil during Simulated Aerobic Biodegradation: Monitored by Semiquantitative Negative-Ion ESI FT-ICR MS

Simulations of aerobic biodegradation have been widely employed to investigate the mechanisms of crude oil biodegradation in geological environments. In this study, a simulated biodegradation experiment was performed with crude oil under aerobic conditions, in which n-alkanes were nearly depleted, thus providing an opportunity to study the biodegradation mechanisms of n-alkanes in crude oils. The sequences of biodegraded oils with a slight to moderate degree of biodegradation were characterized by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography (GC). Semiquantitative results on the molecular compositions of heteroatom classes were obtained by coinjection of internal standards. The biodegradation mechanisms for n-alkanes and n-fatty acids, as well as some other heteroatomic compounds, are discussed. Evidence from FT-ICR MS and GC analyses of biodegraded oils indicates that n-alkanes can be progressively biodegraded to n-fatty ac...

Geochemical Characteristics and Origins of the Crude Oil of Triassic Yanchang Formation in Southwestern Yishan Slope, Ordos Basin.

Biomarker compounds that derived from early living organisms play an important role in oil and gas geochemistry and exploration since they can record the diagenetic evolution of the parent materials of crude oil and reflect the organic geochemical characteristics of crude oil and source rocks. To offer scientific basis for oil exploration and exploitation for study area, gas chromatography-mass spectrometry method is applied to study the biomarker compounds of crude oil in Southwestern Yishan Slope of Ordos Basin, through qualitatively and quantitatively analyzing separated materials. The crude oil of Yanchang Formation and the source rocks of Yan'an and Yanchang Formation were collected in order to systematically analyze the characteristics of the biomarker compounds in saturated hydrocarbon fractions and clarify the organic geochemical characteristics of crude oil. The distribution and composition of various types of hydrocarbon biomarker compounds in crude oil suggest that the parent materials of crude oil are composed of hydrobiont and terrigenous plants, and the crude oil is mature oil which is formed in the weak reducing fresh water environment. Oil source correlation results show that the crude oil of Yanchang Formation in Yishan Slope is sourced from the source rocks of Chang 7 subformation.

Volatile Organic Compounds in Crude Coconut and Petroleum Oils in Nigeria

Analysis of Volatile Organic Compounds (VOCs) in crude coconut and petroleum oils from Nigeria is reported. Using head-space gas chromatography with a flame ionization detector and mass spectrometer, 8 VOCs were found in crude coconut oil and 29 VOCs were identified in crude petroleum oil. Crude coconut oil contained two aromatic, two nitrogenated, and four oxygenated compounds. Alkane, alkene, alkyne, halogenated, and sulfur compounds were absent in crude coconut oil but not in crude petroleum oil. The same observation held true for naphthalene. Conversely, benzofuran was absent in crude petroleum oil but was present in crude coconut oil at a concentration of 1.38 part-per-billion (ppb). The most concentrated VOC in crude coconut oil was dodecanoic acid at 9.98 ppb and that of crude petroleum oil was toluene at 12.61 ppb. Total VOC concentrations in crude coconut and petroleum oils are 20.49 and 87.46 ppb, respectively. These results are helpful in characterizing the chemical signature of Nigerian crude coconut oil for potential forensics use or in biofuel research.

Extractive oxidative desulfurization of model oil/crude oil using KSF montmorillonite-supported 12-tungstophosphoric acid

12-Tungstophosphoric acid (PW) supported on KSF montmorillonite, PW/KSF, was used as catalyst for deep oxidative desulfurization (ODS) of mixed thiophenic compounds in model oil and crude oil under mild conditions using hydrogen peroxide (H2O2) as an oxidizing agent. A one-factor-at-a-time method was applied for optimizing the parameters such as temperature, reaction time, amount of catalyst, type of extractant and oxidant-to-sulfur compounds (S-compounds) molar ratio. The corresponding products can be easily removed from the model oil by using ethanol as the best extractant. The results showed high catalytic activity of PW/KSF in the oxidative removal of dibenzothiophene (DBT) and mixed thiophenic model oil under atmospheric pressure at 75 °C in a biphasic system. To investigate the oxidation and adsorption effects of crude oil composition on ODS, the effects of cyclohexene, 1,7-octadiene and o-xylene with different concentrations were studied.

Structural Assignments of Sulfur-Containing Compounds in Crude Oil Using Ion Mobility Spectrometry-Mass Spectrometry

Through proof-of-concept experiments, a preliminary structural characterization of isomeric and isobaric sulfur-containing compounds in petroleum is presented. Silver attachment to sulfur atom has been used for ionization enhancement of these compounds, which are less accessible by positive-ion electrospray ionization mass spectrometry (ESI-MS). Here, ion mobility spectrometry (IMS) is combined with the enhanced ionization approach and MS to characterize sulfur compounds in crude oil. The silver isotopes, being of nearly equal abundance and having a similar effect upon ion mobilities, provide a fingerprint for assignments of sulfur-containing ions in two-dimensional (2D) plots of mass-to-charge (m/z) vs drift time (tD). Fourier transform ion cyclotron resonance (FT-ICR) MS has been employed for the determination of molecular formulas for these ions. Collision-induced dissociation (CID) data are utilized to complement collision cross section (CCS) comparisons for candidate structures obtained from high mas...

Identification of genotoxic compounds in crude oil using fractionation according to distillation, polarity and Kow

We examined the degree of DNA damage caused by fractions of crude oil in accordance with the boiling points, polarity and log Kow. Relatively high DNA damage was observed in the aromatic fraction (290–330°C) and resin and polar fraction (350–400°C). The resin and polar fraction showed relatively high genotoxicity compared with the aliphatic and aromatic fraction at the 1–4 log Kow range. At the 6–7 log Kow range, the aromatic fraction showed relatively high DNA damage compared with the aliphatic and resin and polar fraction. In particular, every detailed fraction in accordance with the log Kow values (aliphatic and aromatic (310–320°C) and resins and polar fractions (370–380°C)) showed one or less than one DNA damage. However, the fractions before separation in accordance with log Kow values (aliphatic and aromatic (310–320°C) and resin and polar (370–380°C) fractions) showed high DNA damage. Thus, we confirm the synergistic action between the detailed compounds.

Effects of thermal maturation and thermochemical sulfate reduction on compound-specific sulfur isotopic compositions of organosulfur compounds in Phosphoria oils from the Bighorn Basin, USA

Compound-specific sulfur isotope analysis was applied to a suite of 18 crude oils generated from the Permian Phosphoria Formation in the Bighorn Basin, western USA. These oils were generated at various levels of thermal maturity and some experienced thermochemical sulfate reduction (TSR). This is the first study to examine the effects of thermal maturation on stable sulfur isotopic compositions of individual organosulfur compounds (OSCs) in crude oil. A general trend of 34S enrichment in all of the studied compounds with increasing thermal maturity was observed, with the δ34S values of alkyl-benzothiophenes (BTs) tending to be enriched in 34S relative to those of the alkyl-dibenzothiophenes (DBTs) in lower-maturity oils. As thermal maturity increases, δ34S values of both BTs and DBTs become progressively heavier, but the difference in the average δ34S value of the BTs and DBTs (Δ34S BT-DBT) decreases. Differences in the isotopic response to thermal stress exhibited by these two compound classes are considered to be the result of relative differences in their thermal stabilities. TSR-altered Bighorn Basin oils have OSCs that are generally enriched in 34S relative to non-TSR-altered oils, with the BTs being enriched in 34S relative to the DBTs, similar to the findings of previous studies. However, several oils that were previously interpreted to have been exposed to minor TSR have Δ34S BT-DBT values that do not support this interpretation. The δ34S values of the BTs and DBTs in some of these oils suggest that they did not experience TSR, but were derived from a more thermally mature source. The heaviest δ34S values observed in the OSCs are enriched in 34S by up to 10‰ relative to that of Permian anhydrite in the Bighorn Basin, suggesting that there may be an alternate or additional source of sulfate in some parts of the basin. These results indicate that the sulfur isotopic composition of OSCs in oil provides a sensitive indicator for the extent of TSR, which cannot be determined from other bulk geochemical parameters. Moreover, when combined with additional geochemical and geologic evidence, the sulfur isotopic composition of OSCs in oils can help to identify the source of sulfate for TSR alteration in petroleum reservoirs.

Molecular Transformation of Crude Oil in Confined Pyrolysis System and Its Impact on Migration and Maturity Geochemical Parameters

The compositions of crude oils can vary significantly during thermal maturation through cracking and aromatization. In this study, an immature high sulfur crude oil was pyrolyzed in a closed gold-tube system with heating rates of 20 °C/h and 2 °C/h, respectively, to simulate the thermal maturation process of crude oil. The molecular compositions of heteroatom-containing compounds in crude oil were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) while the impact of thermal maturation on migration and maturity geochemical parameters were investigated by gas chromatography–mass spectrometry (GC-MS). Based on the analysis of pyrolysis products, the compositional variations of heteroatom-containing aromatic compounds and the validity of the aromatic geochemical parameters during thermal maturation were investigated. When the equivalent vitrinite reflectance value (Easy %Ro) was greater than ca. 0.85, alkyl chain cracking was the major reaction and led to the producing of...

Visual investigation of the effects of clay minerals on enhancement of oil recovery by low salinity water flooding

Experimental study of Low-Salinity Water flooding (LSWF) in sandstone cores by core flooding indicated the presence of fine particles of clay minerals in the effluent. Also, migration of clay particles is considered as one of the major mechanisms for improving oil recovery by LSWF. In addition, it is believed that the presence of clay minerals is one of the necessary conditions for a positive impact of LSWF because clay/crude interaction plays an essential role in the initial wettability of porous media. However, a clear role of clay minerals in this process has not been identified. The aim of this study is to investigate oil recovery enhancement by fines migration at micromodel scale during LSWF. To this end, kaolinite and sodium bentonite were utilized as migratory and swelling clays in the glass micromodel to create clayey porous media. The results indicated that when the porous medium lacked clay minerals, LSWF did not enhance oil recovery. In the clay-coated porous medium that was free of connate water, the crude oil was adsorbed on the pore surfaces, and under this condition, LSWF caused the migration of clay particles with clinging oil droplets due to the electrical double layer force, which improved oil recovery and water wetness. If the porous medium contained clay minerals and connate water, the crude oil did not stick on the pore surfaces. Hence, in both seawater flooding and LSWF, film-flow was observed, which meant that migration of fines by LSWF did not contribute to the oil recovery enhancement. Our work showed that LSWF would be effective as the secondary recovery method if polar compounds of crude oil were adsorbed on the pore surfaces, which means that the initial wettability of porous media must be mixed-wet. LSWF in the clay-coated porous media with high cation-exchange-capacity clay in the primary mode increased the interstitial velocity in some pore paths due to pore-plugging by swelling of clay and finally led to sectional sweeping.

Analysis of crude oils using gas purge microsyringe extraction coupled to comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry

As a complex mixture, the analysis of individual compounds in crude oil is a great challenge. The traditional sample preparation method such as column chromatography is time-consuming, solvent-wasting, and very possible to cause the loss of light hydrocarbons. In addition, coelution of compounds with similar boiling points or polarities often occurs in one dimensional gas chromatography–mass spectrometry (1D GC–MS). To overcome these disadvantages, a homemade gas purge microsyringe extraction (GP-MSE) device was prepared and coupled to comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) for the analysis of crude oils from different regions. The extraction conditions of GP-MSE were optimized in detail. The whole process of GP-MSE extraction only takes 7min, only 20μL of organic solvent is needed, and almost complete extraction of analytes is achieved. Compared with the common used methods, light hydrocarbons in all the samples were well retained and more compounds were separated and identified, including diamondoid series, pyrrolic nitrogen compounds and other important biomarkers such as terpane and sterane series. Coelution of compounds in 1D GC–MS was eliminated in GC×GC-TOFMS. Based on the developed GP-MSE-GC×GC-TOFMS, the distribution of trace compounds in crude oils and effect of biodegradation were discussed in detail.

Complete genome sequence of a psychotrophic Pseudarthrobacter sulfonivorans strain Ar51 (CGMCC 4.7316), a novel crude oil and multi benzene compounds degradation strain

Pseudarthrobacter sulfonivorans strain Ar51, a psychotrophic bacterium isolated from the Tibet permafrost of China, can degrade crude oil and multi benzene compounds efficiently in low temperature. Here we report the complete genome sequence of this bacterium. The complete genome sequence of Pseudarthrobacter sulfonivorans strain Ar51, consisting of a cycle chromosome with a size of 5.04Mbp and a cycle plasmid with a size of 12.39kbp. The availability of this genome sequence allows us to investigate the genetic basis of crude oil degradation and adaptation to growth in a nutrient-poor permafrost environment.

Characterization of a crude oil weathering series by ultrahigh-resolution mass spectrometry using multiple ionization modes

Accidental crude oil releases, such as the Deepwater Horizon (DWH) accident, are always a potential threat to pristine marine ecosystems. Since the toxicity of crude oil heavily depends on its variable composition, the comprehensive characterization of crude oil compounds as a function of weathering is an important area of research. Traditional gas chromatography-based characterization presents significant limitations, and the use of ultrahigh-resolution mass spectrometric (UHRMS) techniques (that allow for the assignment of molecular formulae) has been shown to be better equipped to address the complex nature of crude oils. This study used an Orbitrap Q Exactive mass spectrometer operated at a resolving power of 140,000FWHM with both electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) sources, in order to characterize a crude oil weathering series of the Macondo oil released during the DWH incident (the source oil, two differently weathered surface slicks, and a beached residue). Preliminary gas chromatography mass spectrometry (GC–MS) and gas chromatography flame ionization detection (GC–FID) results suggested that the four oils comprised a true weathering series (including biodegradation and photodegradation in addition to other well-known processes such as dissolution and evaporation). UHRMS results showed a clear increase in oxygenated compounds with weathering, and further suggested a significant gain of acidic compounds, as well as the transformation of phenols to ketonic and quinonic compounds with weathering. A complementary study on a weathered oil sample amended with selected model compounds contributed additional insight into the functional group types that are accessible in each ionization technique.