The effect of minor to moderate biodegradation on C5 to C9 hydrocarbons in crude oils

A suite of 18 oils from the Barrow Island oilfield, Australia, and a non-biodegraded reference oil have been analysed compositionally in order to detail the effect of minor to moderate biodegradation on C₅ to C₉ hydrocarbons. Carbon isotopic data for individual low molecular weight hydrocarbons were also obtained for six of the oils. The Barrow Island oils came from different production wells, reservoir horizons, and compartments, but have a common source (the Upper Jurassic Dingo Claystone Formation), with some organo-facies differences. Hydrocarbon ratios based on hopanes, steranes, alkylnaphthalenes and alkylphenanthrenes indicate thermal maturities of about 0.8% R_c for most of the oils. The co-occurrence in all the oils of relatively high amounts of 25-norhopanes with C₅ to C₉ hydrocarbons, aromatic hydrocarbons and cyclic alkanes implies that the oils are the result of multiple charging, with a heavily biodegraded charge being overprinted by fresher and more pristine oil. The later oil charge was itself variably biodegraded, leading to significant compositional variations across the oilfield, which help delineate compartmentalisation. Biodegradation resulted in strong depletion of n-alkanes (>95%) from most of the oils. Benzene and toluene were partially or completely removed from the Barrow Island oils by water washing. However, hydrocarbons with lower water solubility were either not affected by water washing, or water washing had only a minor effect. There are three main controls on the susceptibility to biodegradation of cyclic, branched and aromatic low molecular weight hydrocarbons: carbon skeleton, degree of alkylation, and position of alkylation. Firstly, ring preference ratios at C₆ and C₇ show that isoalkanes are retained preferentially relative to alkylcyclohexanes, and to some extent alkylcyclopentanes. Dimethylpentanes are substantially more resistant to biodegradation than most dimethylcyclopentanes, but methylhexanes are depleted faster than methylpentanes and dimethylcyclopentanes. For C₈ and C₉ hydrocarbons, alkylcyclohexanes are more resistant to biodegradation than linear alkanes. Secondly, there is a trend of lower susceptibility to biodegradation with greater alkyl substitution for isoalkanes, alkylcyclohexanes, alkylcyclopentanes and alkylbenzenes. Thirdly, the position of alkylation has a strong control, with adjacent methyl groups reducing the susceptibility of an isomer to biodegradation. 1,2,3-Trimethylbenzene is the most resistant of the C₃ alkylbenzene isomers during moderate biodegradation. 2-Methylalkanes are the most susceptible branched alkanes to biodegradation, 3-methylalkanes are the most resistant and 4-methylalkanes have intermediate resistance. Therefore, terminal methyl groups are more prone to bacterial attack compared to mid-chain isomers, and C₃ carbon chains are more readily utilised than C₂ carbon chains. 1,1-Dimethylcyclopentane and 1,1-dimethylcyclohexane are the most resistant of the alkylcyclohexanes and alkylcyclopentanes to biodegradation. The straight-chained and branched C₅–C₉ alkanes are isotopically light (depleted in ¹³C) relative to cycloalkanes and aromatic hydrocarbons. The effects of biodegradation consistently lead to enrichment in ¹³C for each remaining hydrocarbon, due to preferential removal of ¹²C. Differences in the rates of biodegradation of low molecular weight hydrocarbons shown by compositional data are also reflected in the level of enrichment in ¹³C. The carbon isotopic effects of biodegradation show a decreasing level of isotopic enrichments in ¹³C with increasing molecular weight. This suggests that the kinetic isotope effect associated with biodegradation is site-specific and often related to a terminal carbon, where its impact on the isotopic composition becomes progressively ‘diluted’ with increasing carbon number.     

Identification of C24 and C25 lanostanes in Tertiary sulfur rich crude oils from the Jinxian Sag, Bohai Bay Basin, Northern China

Unusual short chain lanostanes (C₂₄ and C₂₅) and C₃₀ lanostane were identified in sulfur rich crude oils from the Jinxian Sag, Bohai Bay Basin, northern China. Besides the regular steranes (C_27-30), a series of 4-methyl steranes (C₂₂₋₂₃, C₂₇₋₃₀), 4,4-dimethyl steranes (C₂₂₋₂₄, C₂₈₋₃₀), short chain steranes (C₂₃₋₂₆), abundant pregnanes (C₂₁₋₂₂) and androstanes (C₁₉₋₂₀), together with sulfur containing steroids (20-thienylpregnanes and thienylandrostanes) were detected in the aliphatic and branched-cyclic hydrocarbon fraction of these crude oils. A literature survey of some long chain sterane analogues (e.g., A-nor-steranes, norcholestanes, C₃₀ steranes, lanostanes) and pregnanes seems to point to a sponge and/or dinoflagellate source. 4-Methyl, 4,4-dimethyl steroids and lanosterols (4,4,14-trimethyl steroids as the basic skeleton of lanostanes) can be derived from methanotrophic bacteria. Thus, a biological origin from a prokaryotic methylotroph can be used to explain the common source of abundant short chain steranes (C_23-26), 4-methyl (C_22-23) and 4,4-dimethyl steranes (C_22-24), as well as lanostanes (C_24-25 and C₃₀ analogues) in our oil samples. Generally, the steroids appear to have been extensively sulfurized with sulfur substitution at the C-22 position in the side chain during the early stage of diagenesis, which was readily subject to attack by bacterial degradation (enzymatic cleavage) and/or abiotic oxidation. As a consequence, short chain sterane analogues (e.g., abundant pregnanes and androstanes in this study) and short chain lanostanes (C₂₄−C₂₅) might later be released through cleavage of weak C-S bonds at the C-22 carbon in the sulfurized steroids and lanostane sulfides. Finally, the formation of the short chain C₂₄−C₂₅ lanostanes and distinctive occurrence of short chain steranes in this study can be well explained by microbial biodegradation of sulfurized lanostanoids and steroids in the reservoir.     

Primary cracking of kerogens. Experimenting and modelling C1, C2–C5, C6–C15 and C15+ classes of hydrocarbons formed

Mathematical models of hydrocarbon formation can be used to simulate the natural evolution of different types of organic matter and to make an overall calculation of the amounts of oil and/or gas produced during this evolution. However, such models do not provide any information on the composition of the hydrocarbons formed or on how they evolve during catagenesis.From the kinetic standpoint, the composition of the hydrocarbons formed can be considered to result from the effect of “primary cracking” reactions having a direct effect on kerogen during its evolution as well as from the effect of “secondary cracking” acting on the hydrocarbons formed.This report gives experimental results concerning the “primary cracking” of Types II and III kerogens and their modelling. For this, the hydrocarbons produced have been grouped into four classes (C₁, C₂–C₅, C₆–C₁₅ and C₁₅₊). Experimental data corresponding to these different classes were obtained by the pyrolysis of kerogens with temperature programming of 4°C/min with continuous analysis, during heating, of the amount of hydrocarbons corresponding to each of these classes.The kinetic parameters of the model were optimized on the basis of the results obtained. This model represents the first step in the creation of a more sophisticated mathematical model to be capable of simulating the formation of different hydrocarbon classes during the thermal history of sediments. The second step being the adjustment of the kinetic parameters of “secondary cracking”.     

Optimization of headspace single-drop microextraction technique for extraction of light hydrocarbons (C6-C12) and its potential applications

In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography-flame ionization detection (GC-FID) was tested to determine C₆-C₁₂ light hydrocarbons (LHs) in petroleum and aqueous samples. Several significant experimental parameters, such as drop solvent type, drop volume, sample solution ionic strength, agitation speed and extraction time were optimized. Under optimum extraction conditions, specifically, a 1.5 μl microdrop of n-hexadecane, 30 min extraction of a 5 ml aqueous sample placed in a 10 ml vial, and stirring at 1000 rpm at room temperature, the reproducibility and accuracy of this method were found to be satisfactory. Two examples using this method indicated that HS-SDME is a simple, efficient and promising technique for the determination of volatile C₆-C₁₂ LHs in complex matrices.     

Generation and migration of light hydrocarbons (C2C7) in sedimentary basins

Sixty-five samples from selected source bed-type shale sequences from three exploration wells were analysed for yield and detailed composition of light hydrocarbons(C₂C₇) by a new hydrogen stripping/capillary gas chromatographic technique. In spite of low maturation levels (0.35–0.55% vitrinite reflectance), significant generation of ethane and propane was recognized in a Jurassic source bed sequence bearing hydrogen-poor kerogens. Light hydrocarbon generation in another and mature Jurassic source rock sequence is controlled by kerogen quality. Associated with a change from hydrogen-poor to hydrogen-rich kerogens, yields of total and most individual hydrocarbons exhibit orders-of-magnitude increases. At the same time, iso/n-alkane ratios for butanes, pentanes and heptanes decrease significantly. A study of an interbedded marine/nonmarine coal-bearing sequence of Upper Carboniferous age from the Ruhr area, West Germany, revealed that a marine shale unit in comparison to the adjacent coal seam is more prolific in generating n-alkanes of increasing molecular size.A case history for migration of light hydrocarbons by means of diffusion through shales is presented. In two shallow core holes in Campanian/Maastrichtian shales in West Greenland, upward diffusion of ethane to pentane range hydrocarbons is an active process within the near-surface 3 m interval. Diffusive losses within this interval amount to 99.8% for propane, 85.6% for n-butane and 38.9% for n-pentane.     

Reconstructing the response of C3 and C4 plants to decadal-scale climate change during the late Pleistocene in southern Illinois using isotopic analyses of calcified rootlets

The δ¹³C and δ¹⁸O values of well-preserved carbonate rhizoliths (CRs) provide detailed insights into changes in the abundance of C₃ and C₄ plants in response to approximately decadal-scale changes in growing-season climate. We performed stable isotope analyses on 35-40 CRs sampled at 1-cm intervals from an 18-cm-thick paleosol formed in southern Illinois during Wisconsin interstadial 2. Minimum δ¹³C values show little variation with depth, whereas maximum values vary dramatically, and average values show noticeable variability; maximum δ¹⁸O values vary less than the minimum δ¹⁸O values. These findings indicate that a diverse and stable C₃ flora with a limited number of C₄ grass species prevailed during this interval, and suggest that the maximum growing-season temperatures were relatively stable, but minimum growing-season temperatures varied considerably. Two general patterns characterize the relationships between the δ¹³C and δ¹⁸O values obtained from the 1-cm samples. In some cases, low δ¹³C values correspond to low δ¹⁸O values and high δ¹³C values correspond to high δ¹⁸O values, suggesting that cooler growing-season temperatures favored C₃ and warmer growing-season temperatures favored C₄ plants. In other cases, low δ¹³C values correspond to high δ¹⁸O values, likely suggesting that wetter growing-season conditions were favorable to C₃ plants. The high density of well-preserved CRs in this paleosol provides a unique opportunity to study detailed ecological responses to high-resolution variability in growing-season climate.     

Carbon-isotopic analysis of individual pollen grains from C3 and C4 grasses using a spooling-wire microcombustion interface

Pollen grains from grasses using the C₃ and C₄ photosynthetic pathways have distinct ranges of δ¹³C values that may be used to estimate their relative abundance in paleorecords. We evaluated a spooling-wire microcombustion device interfaced with an isotope-ratio mass spectrometer (SWiM-IRMS) for δ¹³C analysis of individual grass-pollen grains. Pollen from four C₃ and four C₄ grass species was isolated through micromanipulation and analyzed as single grains suspended in water. A carbon yield greater than the 2σ range of the carbon content of blanks containing only water was used to distinguish samples containing pollen (“pollen present”) from those not containing pollen. This criterion resulted in the exclusion of ∼45% of the 946 samples applied to the wire. The average δ¹³C values (±1σ) of the remaining samples were −26.9‰ (±6.3‰) and −11.5‰ (±9.6‰) for C₃ grasses and C₄ grasses, respectively, after blank-correcting the δ¹³C data. These results suggest that the SWiM-IRMS system can be used to distinguish C₃ from C₄ grass pollen. The high variability in measured δ¹³C values is likely caused by a combination of factors. These include natural isotopic variability among individual pollen grains; the relatively poor precision that can be obtained when determining δ¹³C values of such small samples; and the uncertainty in the magnitude, isotopic composition, and stability of the analytical blank. Nonetheless, high percentages of individual pollen grains were correctly classified as being of either C₃ or C₄ origin. On average, 90% (range = 78-100%) of pollen grains from C₃ grasses had δ¹³C values more negative than the cutoff threshold of −19.2‰; while 84% (range = 77-90%) of pollen grains from C₄ grasses had δ¹³C values more positive than −19.2‰. Compared with analysis using an elemental analyzer interfaced with an IRMS (EA-IRMS), the number of pollen grains required for δ¹³C-based evaluation of C₃/C₄ grass composition is many times lower with the SWiM-IRMS. Additionally, δ¹³C data from the SWiM-IRMS does not need to be incorporated into a mixing model to derive estimates of the abundance of C₃ and C₄ grass pollen. Carbon-isotopic analysis of individual grass-pollen grains using the SWiM-IRMS system may help improve our understanding of the evolutionary and ecological significance of grass taxa in the paleorecord.     

Thermal evolution of n- and iso-alkanes in oils. Part 1: Pyrolysis model for a mixture of 78 alkanes (C1-C32) including 13,206 free radical reactions

A mechanistic model consisting of 13,206 lumped free radical reactions has been developed to describe the thermal evolution of a mixture of 78 alkanes: all n-alkanes from C₁ to C₃₂ and 46 branched alkane model compounds from C₄ to C₃₂. The mixture was meant to represent the major part of the saturated fraction of petroleum. The rate constants used are available from the literature. The lumping together procedure is described and the model validated on the basis of several experimental results from the literature and relating to pure alkanes. The model is also compared to the saturated fraction obtained from pyrolysis of Elgin oil at 372 °C for up to 1000 h. The cracking global activation energy of n-C₁₅ as well as iso-C₁₅ is close to 69 kcal/mol in the range 200-350 °C. The implications of the model for geological reservoirs will be discussed in a following paper.     

Application of light hydrocarbons (C4–C13) to oil/source rock correlations:: a study of the light hydrocarbon compositions of source rocks and test fluids from offshore Mid-Norway

Relatively little work has been published on the correlation between the light hydrocarbon distributions in reservoir fluids and their proposed source rocks [Philippi, G. T. (1981)]. The aim of our work was to study this relationship in detail for samples from Mid-Norway. The main source rocks offshore Mid-Norway are the marine shales of the Late Jurassic Spekk Formation and the coals and paralic shales of the Early Jurassic Åre Formation. Reliable light hydrocarbon (C₄–C₁₃) data for source rock samples were acquired by thermal extraction-GC of the source rocks. Of these, notably the hydrocarbons in the C₆–C₈ range (routinely measured in test fluids) were used to discriminate between the Spekk and Åre Formation samples. A total of twenty-six samples from the Spekk Formation and twenty-four samples from the Åre Formation at different maturity levels and facies were analyzed. In general, the two source rock types differ in their light hydrocarbon composition by the presence of relatively more aromatics and cyclohexanes in the Åre samples, while the Spekk samples are richer in cyclopentanes and acyclic hydrocarbons. We show that source rock facies is a more important indicator of light hydrocarbon composition than maturity variation. Differences in the chemical composition, which can be used to discriminate between the two source rocks, were supported by differences in the carbon isotope composition of individual components of the same fraction, as determined by GHM-IR-MS analysis of eleven samples. Further, the light hydrocarbon compositions of reservoir fluids (oils and condensates) were compared with those for the source rock(s). Sixty-six gas chromatograms of oils and condensates, representing most of the known petroleum accumulations in Mid-Norway, were collected. Of these, five oil samples were selected for detailed isotopic analysis of individual components (GC-IR-MS). When using a classification scheme based on data from sediment samples, data for the light hydrocarbon fraction of oils and condensates indicate that the Spekk Formation is the dominant source for most of the fields from Mid-Norway, with a significant contribution from the Åre Formation being detected principally in one field. Differences in the chemical composition of the C₆–C₈ fractions were supported by differences in the carbon isotope composition of individual components, which also discriminate between the oils. Although the classification diagrams used in this study are based on source rock data from Mid-Norway, the method can be applied to other areas, providing that the diagrams are calibrated with source rock data from the area of interest.     

Volatile C1C7 organic compounds in an anoxic sediment core from the Pettaquamscutt River (Rhode Island,U.S.A.)

Surface sediments from an anoxic marine environment, the Upper Basin of the Pettaquamscutt River, Rhode Island, were analyzed for volatile organic compounds in the C₁C₇ range. The compounds identified included methane, ethane, alkenes (C₂C₅), carbon disulfide, cyclopentane, 3-methylpentane, methylfuran, aldehydes and ketones. Ethane, methylfuran, and most of the aldehydes and ketones showed maxima at the sediment water interface. Methane levels were very high-10–100 times greater than observed in most other surface sediments examined in this laboratory.     

C24–C27 Degraded triterpanes in Nigerian petroleum: novel molecular markers of source/input or organic maturation?

The analyses, by gas chromatography and gas chromatography/mass spectrometry, of the triterpane concentrate of crude oils sampled from various oil fields of the Tertiary Niger delta have revealed the ubiquitous presence of a series of C₂₄–C₂₇ tetracyclic alkanes likely to be novel degraded triterpanes. The presence in the crude oils of a C₂₅ tricyclic alkane, apparently structurally related to the tetracyclanes, seemed consistent with the hypothesis of sequential cleavages of the terminal rings of precursor pentacyclic triterpenoid derivatives with increasing thermal transformation of the respective petroleums.The degraded triterpanes might be useful for assessing the stages of thermal evolution of petroleum in the reservoir. A possible application, to oil exploration, of the expected variations in the concentration of the polycyclanes in crude oils with different thermal histories would be in distinguishing primary (immature) oils from mature but biodegraded oils.     

Correlation of crude oils and oil components from reservoirs and source rocks using carbon isotopic compositions of individual n-alkanes in the Tazhong and Tabei Uplift of the Tarim Basin,China

Carbon isotopic compositions were determined by GC–IRMS for individual n-alkanes in crude oils and the free, adsorbed and inclusion oils recovered by sequential extraction from reservoir rocks in the Tazhong Uplift and Tahe oilfield in the Tabei Uplift of Tarim Basin as well as extracts of the Cambrian–Ordovician source rocks in the basin. The variations of the δ¹³C values of individual n-alkanes among the 15 oils from the Tazhong Uplift and among the 15 oils from the Triassic and Carboniferous sandstone reservoirs and the 21 oils from the Ordovician carbonate reservoirs in the Tahe oilfield demonstrate that these marine oils are derived from two end member source rocks. The major proportion of these marine oils is derived from the type A source rocks with low δ¹³C values while a minor proportion is derived from the type B source rocks with high δ¹³C values. Type A source rocks are within either the Cambrian–Lower Ordovician or the Middle–Upper Ordovician strata (not drilled so far) while type B source rocks are within the Cambrian–Lower Ordovician strata, as found in boreholes TD2 and Fang 1. In addition, the three oils from the Cretaceous sandstone reservoirs in the Tahe oilfield with exceptionally high Pr/Ph ratio and δ¹³C values of individual n-alkanes are derived, or mainly derived, from the Triassic–Jurassic terrigenous source rocks located in Quka Depression.The difference of the δ¹³C values of individual n-alkanes among the free, adsorbed and inclusion oils in the reservoir rocks and corresponding crude oils reflects source variation during the reservoir filling process. In general, the initial oil charge is derived from the type B source rocks with high δ¹³C values while the later oil charge is derived from the type A source rocks with low δ¹³C values.The δ¹³C values of individual n-alkanes do not simply correlate with the biomarker parameters for the marine oils in the Tazhong Uplift and Tahe oilfield, suggesting that molecular parameters alone are not adequate for reliable oil-source correlation for high maturity oils with complex mixing.     

Polymerization of silicate and aluminate tetrahedra in glasses,melts, and aqueous solutions—I. Electronic structure of H6Si2O7, H6AlSiO71−, and H6Al2O72−

As part of a study of the effect of geologically common network modifiers on polymerization in silicate melts, glasses, and silica-rich aqueous solutions, we have studied the energies, electronic structures, and inferred chemical properties of ^IVT-O-^IVT linkages in the tetrahedral dimers H₆,Si₂O₇, H₆AlSiO₇^1?, and H₆Al₂O₇^2? using semi-empirical molecular orbital theory (CNDO/2). Our results indicate that the electron donating character of the bridging oxygen, O(br), linking two tetrahedra increases with increasing T-O(br) bond length but decreases with decreasing T-O(br)-T angles and increasing O-T-O(br) angles. This increase or decrease of the donor character of O(br) coincides with an increase or decrease of the affinity of O(br) for hard acceptors. The calculated electronic structure for the H₆Si₂O₇ molecule is compared with the observed X-ray emission, absorption, and photoelectron spectra of quartz and vitreous silica; the reasonable match between calculated and observed oxygen Kα emission spectra of vitreous silica supports our assertion that non-bonded O(br) electron density energetically at the top of the valence band controls the chemical reactivity of ^IVT-O-^IVT linkages in polymerized tetrahedral environments.     

The impact of thermal maturity level on the composition of crude oils,assessed using ultra-high resolution mass spectrometry

We have examined, using a 12 Tesla FTICR-MS instrument, the impact of varying thermal maturity level on a suite of 9 related crude oils charged from source rocks covering most of the liquid petroleum generating portion of the oil window (0.68–1.11% vitrinite reflectance equivalent (%Re)). The sample suite was analyzed as whole oils under three different conditions, electrospray ionization (ESI) in positive and negative ion mode to analyze basic and acidic components, respectively, and atmospheric pressure photoionization (APPI) in positive ion mode, for sulfur and hydrocarbon species.Increasing oil maturity level had a strong influence on the composition of all compound classes in the oils with several major observations evident:The relative apparent abundances of all heteroatom containing compound classes detected in this study, using all ionization modes, decrease systematically with increasing oil maturation levels. Both aromatic hydrocarbons, detectable in APPI mode, and NSO compound classes (detectable in both ESI and APPI modes), as broad classes, are becoming more aromatic (shift to a greater predominance of higher DBE group members) and dealkylated (decreasing average molecular mass of individual compound groups), with increasing maturation level in the oil suite. Several putative oil maturity level dependent, molecular ratios were identified in the study. Of particular note, the relative abundance ratios of heteroatom compound classes tentatively identified as alkylated carbazoles, quinolines and benzothiophenes, compared to their benzannulated homologues are very sensitive to maturation level. Several groups of compounds show interesting and specific carbon number distributions, suggesting there may be hints of specific molecular markers in the FTICR-MS data. One observation of note is the strong increase in the relative abundance of protonated hydrocarbon components with DBE 5. We speculate this might reflect the presence of previously unreported higher molecular weight diamondoid (diamantane) species in oils with up to 40 carbon atoms or more, at advanced maturity levels. Such species may prove very valuable as molecular markers in highly mature fluids, such as those currently being produced from some shale reservoirs. Covariation of quantitative GC–MS data for alkylated hetero aromatic sulfur and nitrogen compounds in this oil suite, together with the corresponding FTICR-MS data from compounds believed to be, based on accurate mass, alkylated sulfur and alkylated nitrogen compounds, suggests that FTICR-MS already has some very rudimentary quantitation capabilities.     

Identification and occurrence of novel C36–C54 3,4-dialkylthiophenes with an unusual carbon skeleton in immature sediments

A series of novel long-chain 3,4-dialkylthiophenes (C₃₆–C₅₄) was identified in a number of sediments ranging from Pleistocene to Cretaceous. The identifications were based on mass spectral characterisation, desulphurisation and mass spectral data of synthesised model compounds. These organic sulphur compounds are probably formed by sulphur incorporation into mid-chain dimethylalkadienes with two methylenic double bonds. These putative precursor lipids are unprecedented and may be considered rather unusual. The distribution of 3,4-dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment, indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment.     

Free energy of formation for green rust sodium sulphate (NaFe6Fe3(OH)18(SO4)2(s))

In a recent study, sulphate-bearing green rust (GR_SO4) was shown to incorporate Na⁺ in its structure (NaFe^II₆Fe^III₃(OH)₁₈(SO₄)_2(s); GR_Na,SO4). The compound was synthesised by aerial oxidation of Fe(OH)_2(s) in the presence of NaOH. This paper reports on its free energy of formation .Freshly synthesised GR_Na,SO4 was titrated with 0.5 M H₂SO₄ in an inert atmosphere at 25 °C, producing dissolved Fe²⁺ and magnetite or goethite. Solution concentrations, PHREEQC and the MINTEQ database were used to calculate reaction constants for the reactions:

     

鄂尔多斯盆地华池-庆阳地区延长组长62-63沉积微相研究

为了更精准地研究鄂尔多斯盆地西南部华庆地区上三叠统延长组长6₂-6₃油层组储层特征,运用岩心照片、测井数据、粒度分析、录井数据等资料,对延长组长6₂-6₃油层组的岩性、碎屑颗粒、构造、测井响应、生物标志以及接触关系进行了分析研究。分析了长6油层组沉积微相特征,识别出该沉积时期半深湖-深湖亚相和三角洲前缘亚相两类沉积亚相,半深湖泥、浊积岩、砂质碎屑流砂体、水下分流河道、分流间湾和席状砂6类沉积微相,并分析华庆地区延长组长6₂-6₃期沉积相发育演化过程。沉积微相精细化描述揭示了华庆地区延长组6段油层组沉积环境,为精细化勘探开发提供地质依据。