Influence of composition of Poly(meth)acrylate thickeners on the pour point of hydraulic oils

The influence of the characteristics (molecular weight, alkyl group composition, ratio of acrylate to methacrylate units) and dosage of poly(alkyl (meth)acrylate) thickening agents on the pour point of various base oils used for manufacturing hydraulic fluids has been studied. It has been shown that the effect of pour point elevation with the increasing additive concentration can be leveled by extending the range of alkyl groups and introducing methyl methacrylate units into the polymers.     

Generation of adamantanes and diamantanes by thermal cracking of polar components of crude oils of different genotypes

The thermal cracking of polar petroleum compounds—resins and asphaltenes—isolated from crude oils of different genotypes was carried out, with C₁₀-C₁₃ adamantanes and C₁₄-C₁₆ diamantanes being produced as a result. It was assumed that resins and asphaltenes contain the adamantane and diamantane moieties in their molecular structure. An explicit relation between the distribution of C₁₀–C₁₃ adamantanes in crude oils, thermal cracking products of high-molecular-mass (bp >350°C) saturated fractions, and the products of thermal cracking of resins and asphaltenes was revealed. The distributions of C₁₄–C₁₆ diamantanes in the cracking products of resins and asphaltenes are close to one another and correlate well with their distribution in the products of thermal cracking of high-molecular-mass (>350°C) saturated fractions, but differ from the distribution in oils. The products of thermal cracking of resins and asphaltenes almost completely lack cyclic hydrocarbons and contain only a small amount of remaining n-alkanes and isoprenanes.     

Generation of adamantanes and diamantanes by thermal cracking of high-molecular-mass saturated fractions of crude oils of different genotypes

The thermal cracking of high-molecular-mass paraffin-cycloparaffin fractions (bp above 350°C) of oils of different genotypes was carried out. Although the >350°C fraction contains neither adamantanes C₁₀-C₁₄ nor diamantanes C₁₄-C₁₆, which boil in the range 190–286°C, they are generated again during the thermal cracking of high-molecular-mass paraffin-cycloparaffin fractions. Thus, it was first shown that hydrocarbons with the adamantane and diamantane moieties are present in the >350°C fraction. The distribution of C₁₀-C₁₃ adamantanes in crude oils correlates well with that in the products of the thermal cracking of high-molecular-mass (>350°C) saturated fractions, thus indicating a relation between the high-molecular-mass hydrocarbon portion containing the adamantane moiety and C₁₀-C₁₃ adamantanes in the oils. There is no such correlation for the distribution of diamantane hydrocarbons of the C₁₄-C₁₆ series.     

Whole-oil relationship and origin of oil derived from heterogeneous reservoir systems in an offshore field,SE, Niger Delta

Whole-oil (C3–C39) gas chromatograms were obtained for 46 oil samples collected from a reservoirs pool in an oilfield located offshore SE Niger Delta, to investigate the origins and the relationships of the oils, in spite of the discontinuity of the reservoirs from which the oils were produced. All the oils contained hydrocarbons in the range C₃–C₃₉ with prominent pristane and phytane. The plot of pristine: nC17 versus phytane: nC18 shows oils of terrestrial origin that is deposited in an oxidizing environment. However, some of the oils show depletion of n-paraffin in the C₅–C₁₁ range and have abundant n-paraffin in the C₁₂–C₃₅ range suggesting biodegraded oils. The isoprenoid peaks, however, are more prominent than adjacent n-paraffin in some of the other oils. A star plot of the ratios derived from napthenic, aromatic, isoprenoid, and normal alkane compounds of the samples, in addition to the above-mentioned variations, allowed the grouping of the oils into three families. The results infer that the oils from the south eastern Niger delta may be related in some way (in terms of source input) but may have undergone slightly different histories due to reservoir discontinuity.     

GEOCHEMISTRY AND ORIGIN OF UPPER CRETACEOUS OILS FROM THE TERMIT BASIN,NIGER

Crude oil samples (n = 16) from Upper Cretaceous reservoir rocks together with cuttings samples of Upper Cretaceous and Paleogene mudstone source rocks (n = 12) from wells in the Termit Basin were characterized by a variety of biomarker parameters using GC and GC‐MS techniques. Organic geochemical analyses of source rock samples from the Upper Cretaceous Yogou Formation demonstrate poor to excellent hydrocarbon generation potential; the samples are characterized by Type II kerogen grading to mixed Types II–III and III kerogen. The oil samples have pristane/phytane (Pr/Ph) ratios ranging from 0.73 to 1.27, low C₂₂/C₂₁ and high C₂₄/C₂₃ tricyclic terpane ratios, and values of the gammacerane index (gammacerane/C₃₀hopane) of 0.29–0.49, suggesting derivation from carbonate‐poor source rocks deposited under suboxic to anoxic and moderate to high salinity conditions. Relatively high C₂₉ sterane concentrations with C₂₉/C₂₇ sterane ratios ranging from 2.18–3.93 and low values of the regular steranes/17α(H)‐hopanes ratio suggest that the oils were mainly derived from kerogen dominated by terrigenous higher plant material. Both aromatic maturity parameters (MPI‐1, MPI‐2 and R_c) and C₂₉ sterane parameters (20S/(20S+20R) and ββ/ (αα + ββ)) suggest that the oils are early‐mature to mature. Oil‐to‐oil correlations suggest that the Upper Cretaceous oils belongs to the same genetic family. Parameters including the Pr/Ph ratio, gammacerane index and C₂₆/C₂₅ tricyclic terpanes, and similar positions on a sterane ternary plot, suggest that the Upper Cretaceous oils originated from Upper Cretaceous source rocks rather than from Paleogene source rocks. The Yogou Formation can therefore be considered as an effective source rock.     

Investigation of the properties of novel nitrogen-containing poly(meth)acrylate oil thickening agents

A comparative study of the properties of poly(decyl methacrylate) and decyl methacrylate copolymers with N-tert-nonylacrylamide as viscosity index improver-dispersant additives for petroleum oils has been performed. Tests in the I-20A oil have shown that the introduction of substituted acrylamide units improves the thickening and dispersing properties of the poly(meth)acrylate additives, but it reduces their resistance to mechanical degradation.     

Dependence of efficiency of polyalkyl acrylate-based pour point depressants on composition of crude oil

Thirteen polyalkyl acrylate-based depressor additives with C16-C26 alkyl groups containing 0–30 mol% of various polar groups (amide, amine, ammonium, N-vinylpyrrolidone, oligo(ethylene glycol)) have been synthesized and tested in 18 crude oil samples of significantly different compositions. It has been shown that the dependences of the depressor effect on the additive concentration pass through maxima. An approach that predicts the degree of decrease in pour point of oil in the presence of polyalkyl acrylate additives depending on the content of paraffin and resin-asphaltene components was proposed for the first time. A polyalkyl acrylate with C16-20 alkyl groups proved to be the most versatile additive. However, polymers with different lengths of alkyl groups or containing polar groups are more effective for some oils.     

Application of Light Hydrocarbon (C7+) and Biomarker Analyses in Characterizing Oil from Wells in the North and North Central Sinai,Egypt

Abstract

Seven representative oil show samples from wells in the north and north central Sinai have been characterized by means of a variety of organic geochemical techniques (C₇ hydrocarbon and biomarker analyses), to illustrate origin, differences, and similarity among oils. These oils were obtained from Cretaceous and Jurassic reservoirs. The C₇ oil correlation star diagram (OCSD) suggests closely related oils, derived mainly from similar source rocks, while the C₇ oil transformation star diagram (OTSD) and C₇ light hydrocarbon analyses indicate a minor degree of transformation of some oils, as Misri-1, Halal-1, and Nakhl-1 oils were subjected to evaporative fractionation. Moreover, the studied oils show no sign of water washing and biodegradation. Molecular characteristics suggest pre-Tertiary shales and carbonate source rocks, deposited under a saline oxic environment, rich in terrigeneous organic sources with significant bacterial and algal input. Since the studied oils are of mixed marine and terrestrial origin, C₇ signature of these oils is not representative of their origin and should be supported by other geochemical evidence (e.g., biomarkers) to predict their origin.     

Petroleum naphthenomono-and naphthenobiarenes

The hydrocarbon-group composition and distribution of naphthenoaromatic hydrocarbons of West Siberian oils were studied by the technique of mass spectrometry. Naphthenoaromatic hydrocarbons of the general formula C_nH_2n?z , where z is 8, 10, 12, 14, 16, or 18, containing from one to six saturated cycles are present in oils in significant concentrations. Naphthenomonoarenes with one saturated cycle dominate in all oils. An increase in the amount of compounds containing 3–6 saturated cycles in their molecule with the occurrence depth was noted. Naphthenobiarenes of the general formula C_nH_2n?z , where z is 14, 16, 18, 20, 22, or 24 containing from one to six saturated cycles are present in oils in concentrations from 20.0 to 54.0 wt % of the biaromatic fraction. Most oils are characterized by the prevalence of structures with one and two saturated cycles in their molecule. The dependence of the number of cycles in naphthenobiarenes on the nature of original organic matter (OM) was not traced. The lack of correlation between the number of cycles and the OM type is presumably due to the fact that, for the most part, fused polycyclic naphthenobiarenes reflect the degree of catagenetic alteration of organic matter.     

Light hydrocarbon geochemistry of crude oils from Eastern Niger Delta

Abstract

Geochemical evaluation of oil samples from the eastern part of the Niger Delta divided into western, eastern, and central sections of the study area was carried out for the characterization of their light hydrocarbons content in order to correlate oils from different parts. The hydrocarbons in the oil samples were determined using gas chromatographic (GC) technique. The results obtained showed that CPI, Pr/Ph, Pr/nC₁₇, and Ph/nC₁₈ ratios ranged from 0.99–1.55, 2.19–4.79, 0.92–2.35, and 0.27–0.47, respectively. The Pr/nC₁₇ versus Ph/nC₁₈ plot showed that the oils were derived from terrestrial organic materials that were deposited under oxic to suboxic conditions. They are moderately matured with minimal effect of biodegradation on most of the oil samples although two of the oils showed relatively higher degradation. Both bivariate and multivariate plots of the light hydrocarbon ratios differentiated the western and central oils from the eastern oils. The classification of the oils into families was not based on origin but rather on post generative alterations that include reservoir conditions and possibly migration effects. The light hydrocarbon parameters identified can be used in the correlation tools.     

Synthesis of 2-alkyl(aryl)thietanes

Thietane and its 2-substituted derivatives were synthesized. A general preparation procedure for the synthesis of thietanes bearing alkyl and aryl substituents in the α-position was developed. Using this procedure, 2-substituted thietanes can be obtained from cheap and easily accessible raw materials in three steps. 2-R-Thietanes (where R = H, CH₃, C₄H₉, C₅H₁₁, C₆H₁₃, C₆H₅) and the corresponding sulfoxides and sulfones were synthesized and examined. Intermediate and by-products of the synthesis were studied.     

Synthesis of 3-alkyl(aryl)thietanes

A preparative procedure for the synthesis of thietanes bearing alkyl substituents in the β-position was developed. Using this procedure, 3-substituted thietanes can be obtained in four steps with an ultimate yield of > 50%. 3-R-thietanes (where R = CH₃, C₄H₉, C₅H₁₁, C₆H₁₃, C₆H₅) and the corresponding sulfoxides and sulfones were synthesized and examined. The feasibility of preparation of gem-3,3-substituted thietanes was exemplified by the synthesis of 3,3-dihexylthietane.     

GEOCHEMISTRY OF SEEP AND PRODUCED OIL SAMPLES FROM SOUTHERN CAMEROON

Crude oil samples from surface seeps in the Douala Basin (southern Cameroon) and from producing fields in the nearby Rio del Rey and Kribi‐Campo sub‐basins were analysed for bulk and molecular geochemical parameters by inductively coupled plasma – mass spectrometry (ICP‐MS), gas chromatography – mass spectrometry (GC‐MS) and isotope ratio mass spectrometry (IRMS). The aims of the study were to assess the composition of the oils, to evaluate the relationship between the seep oils and the oils from producing fields, and to highlight the significance of the data for oil exploration in the region. Chromatograms of the saturate fractions of the oils exhibit biodegradation ranging from very light (PM1 on the scale of Peters and Moldowan, 1993) in oil from the offshore Lokele field in the Rio del Rey sub‐basin, to severe (PM 6+) for seep oils from the Douala Basin. A plot of Pr/n‐C₁₇ (1.3– 5.0) versus Ph/n‐C₁₈ (0.8–2.6) for the samples further supports mild biodegradation in some samples (Lokele, Kole, Ebome), and demonstrates that the oils from the Lokele and Kole fields (Rio Del Rey sub‐basin) and from Ebome field (Kribi‐Campo sub‐basin) originated from mixed organic matter with a dominant marine contribution. The Pr/Ph ratio (1.8–2.3) for the Lokele, Kole and Ebome oil samples, and the V/(V+Ni) ratios (< 0.5) for the seep oils (Douala Basin) and the oils from the Lokele, Kole and Ebome fields, indicate derivation from source rocks deposited in oxic – dysoxic environments. The CPI (1.0–1.1) demonstrates that the Lokele and Ebome oils originated from mature source rocks, with the ratios of C₃₁ 22S/(S+R) (0.57 to 0.63) and C₃₀‐βαH/C₃₀‐αβH (0.18–0.23) for the Lokele, Kole and Moudi samples indicating early oil window maturity. Both V/(V+Ni) ratios (0.06–0.22) and δ¹³C (‐26.96 to ‐24.89 ‰) were used for correlation of the oils, with the seep oils from the Douala Basin showing the closest relationship to the oil from the Lokele field. The presence of mature Type II / III source rocks in different basins in southern Cameroon suggests significant potential for oil exploration in the region.     

Biomarkers and isotopic characteristics of crude oils from a central Niger delta depobelt field,Nigeria

Twelve crude oils samples from a field in the central depobelt in the Niger delta, Nigeria were analyzed for their biomarkers and isotopic composition by Gas chromatography–Mass spectrometry and Isotope mass spectrometry. The percentage C_27, C₂₈ and C₂₉ steranes in the oils ranged from 35.80 to 39.9, 28.1 to 30.8 and 29.9 to 35.0, respectively. The distribution of molecular biomarkers and isotopic composition in the oils indicated that they were formed from source rocks of a mixed source (marine and terrestrial kerogen) but with greater input from marine organic matter. The Pr/Ph ratios of the oil samples ranged from 1.2 to 2.3 and this indicated organic matter deposited under suboxic conditions. The vitrinite reflectance (%VRc) values calculated from methylphenanthrene index-1 (MPI-1) parameter ranged from 0.89 to 1.07 indicating oils generated at the peak of oil window.     

OCCURRENCE AND DISTRIBUTION OF n-ALKANESAND n-FATTY ACIDS IN SAUDI ARABIAN CRUDE OILS

ABSTRACT

Ten crude oil samples, covering wide range of maturity (API gravity = 18·5–36·1), were assembled from Safaniya, Abqiq, Ain Dar, Wafra. Marjan and Zuluf oil fields in the area of Arabian Gulf. n-Alkanes of were separated from the petroleum distillate ((150°C–450°C) of the crude oils by urea adduction. n-Fatty acids were separated from the fraction of n-alkanes by treatment with aqueous solution of KOH. Distribution of n-alkanes and n-fatty acids has been investigated by means of gas chromatography. The studied crude oils showed symmetrical distribution curves of n-paraffins and fatty acids of low molecular weight were abundant as compared with n-paraffins. The n-paraffins distribution curve of Wafra/Iucene biodegraded immature crude oil showed three maxima at C₁₇, C₁₉, and C₃₁ whereas the maxima of n-fatty acids are located at C₁₄,C₂₂and C₂₄. The results were interpreted in terms of origin, maturation and depositional environments of the crude oils.     

Correlation of basic <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR-measurable structural group parameters of crude oils of the Volga–Urals oil and gas basin

Among 120 pairwise relations between 16 main ¹H and ¹³C NMR-measurable characteristics of the structural group composition of Volga–Urals crude oils, 10 most consistent relations (correlation coefficients |r_s| ≥ 0.9), 13 relations with |r_s| in the range of 0.8–0.9, and 33 pairs with loosely related or mutually independent members (|r_s| ≤ 0.3) have been revealed. Several relationships are parametric. The main parameter is C_ar. The overall picture of the relationships is complex; correlation coefficients with the absolute value above 0.7 are observed not only between the parameters characterizing the structure in the same group of entities (aromatic, n-alkyl): it has been found that C_ar correlates with the total content of n-alkyl structures (r_s =–0.76). Having definitely common features, oils from the Volga–Urals and Western Siberia oil and gas basins noticeably differ from one another. To explain the differences, it is necessary to launch an integrated study that is methodologically beyond the scope of contemporary petroleum geochemistry. The paper demonstrates the capabilities of correlation analysis for solving problems to which this method has not been yet applied in petroleum geochemistry: partial correlation coefficients as a means of identifying parametric relationships and Spearman correlation coefficients for nonnumeric values in determining differences in the composition between oils of different structures and from different territories or stratigraphic plays.     

Waxes in asphaltenes of crude oils and wax deposits

Composition and molecular mass distribution of n-alkanes in asphaltenes of crude oils of different ages and in wax deposits formed in the borehole equipment were studied. In asphaltenes, n-alkanes from C_(12) to C_(60) were detected. The high molecular weight paraffins in asphaltenes would form a crystalline phase with a melting point of 80–90 ℃. The peculiarities of the redistribution of high molecular paraffin hydrocarbons between oil and the corresponding wax deposit were detected. In the oils, the high molecular weight paraffinic hydrocarbons C_(50)–C_(60)were found, which were not practically detected in the corresponding wax deposits.     

New and less common sterane and terpane hydrocarbons in oils from the Nepa-Botuoba anteclise (Eastern Siberia)

A number of previously unknown or less common sterane and terpane hydrocarbons in crude oils of the Nepa-Botuoba anteclise (NBA) have been found by gas chromatography-mass spectrometry. The former include pregnane structures demethylated at C10 (principal fragment ion at m/z 203) and C₂₆-C₂₉ tricyclic secosteranes (m/z 219). By the m/z 123 mass chromatogram, a number of bicyclic sesquiterpanes with the drimane or tricyclic norisopimarane structure have been identified for the first time in NBA oils. The origin of these terpenoid hydrocarbons is usually associated with the involvement of higher plant debris in sedimentary source rocks. Their presence in Neoproterozoic oils suggests other precursors of these hydrocarbons. Like 10-desmethylpregnanes, 12- and 13-monomethylalkanes, which are unique biomarkers for Neoproterozoic oils of the Siberian platform, have been found in Vendian and Lower Cambrian oils of the Arabian platform and provide evidence for a close similarity between biotas that existed in these ancient basins.     

The formation of the composition of unrecovered oils in producing oil fields of Tatarstan

Analysis of the composition of unrecovered and produced oils of Tatarstan shows that the adsorption-chromatographic process upon oil motion in the reservoir during recovery is manifested in an increase in the density and viscosity of unrecovered oils. They do not contain light hydrocarbons of the IBP ?200°C fraction and have dramatically smaller concentrations of both the least polar lube oil hydrocarbons and alcohol-benzene-extractable resins exhibiting the highest polarity. According to GLC data, unrecovered and produced oils are classified with different subtypes of chemical type A1 of nonbiodegraded oils: produced oils are grouped with subtype 1 and unrecovered oils are attributed to subtype 2. The dynamics of the development of areas of produced oils with the use of a technique based on the activation of reservoir microflora showed that the process of the microbiological oxidation manifests itself in the preferential ability of reservoir microflora to digest C₁₂-C₃₄ n-alkane hydrocarbons as compared to cyclic hydrocarbons. Normal C₁₂-C₂₀ alkanes are consumed by bacteria before hydrocarbons with a greater number of carbon atoms C₂₀-C₃₄ of this series. An analysis of extracts from aqueous infusions of oils showed that the dissolution process leads to the transfer of 0.04–0.07 wt % hydrocarbons and heteroatomic components from oil to water.     

Organic geochemical characterization of crude oils based on alkanes and acyclic isoprenoids distribution

A variety of biomarker and non-biomarker parameters has been used to geochemical characterization of seven crude oils from the Gulf of Suez region of Egypt. The carbon number distribution and the identities of specific compounds were determined by GC and GC–MS analysis of the saturated fraction obtained by liquid chromatography. n-Alkanes ranging from C₁₀ to C₃₅ were the major constituent series, while acyclic isoprenoids from C₁₃ to C₂₀ except C₁₇, iso- and anteiso-alkanes and cyclic alkanes were the minor constituent series. The close range of bulk property values and biomarker distribution indicated that the investigated oils are belong to only one type. Correlation plots between biomarker and non-biomarker parameters revealed that the oil samples are typical of crude oils generated from marine sediments deposited in suboxic conditions.