Formation and Accumulation of Hydrocarbons in the Central Uplift,Dongying Depression

1. Introduction The Central Uplift discussed is located in the center of the Dongying Depression, Bohai Bay Basin, which is one of the most important petroliferous areas in China. It borders the Lijin Sag in the west and south, and is bounded by the Niuzhuang and Minfeng sags in the east and northeast respectively. There are multiple source rocks providing oils for the Uplift, with different types of hydrocarbon genesis due to the special geological background (Liu, et al., 2004). The Up…     

The effects of temperature and acid number of crude oil on the wettability of acid volcanic reservoir rock from the Hailar Oilfield

Wettability of acid volcanic reservoir rock from the Hailar Oilfi eld,China,was studied with crude oils of different acid numbers generated from an original crude oil with an acid number of 3.05 mg KOH/g. The modif ied oils and their resultant acid numbers were:A(2.09 mg KOH/g) ,B(0.75 mg KOH/g) ,C(0.47 mg KOH/g) ,D(0.30 mg KOH/g) ,and E(0.18 mg KOH/g) . Contact angles and improved Amott water indexes were measured to study the effects of temperature and acid number on the wettability of the acid volcanic r...     

Bulk geochemical characteristics and carbon isotope composition of oils from the Sayhut sub-basin in the Gulf of Aden with emphasis on organic matter input,age and maturity

The Sayhut sub-basin is undergoing hydrocarbon exploration province in the Gulf of Aden, South Yemen. In this study, geochemical analyses were performed on three oil samples from two exploration wells in the Sayhut sub-basin. The results were used to describe the source organic matter input, age and maturity and to correlate between crude oils from different pay zones.The high saturated hydrocarbon values of more than 70% indicate that the analysed oils are normal crude oils and not degraded oils. This is supported by a complete suite of their normal alkanes and acyclic isoprenoids. The hydrocarbon distributions of normal alkane and isoprenoid with bulk carbon isotope data also suggest that the analysed oils are grouped into two genetic families and were generated from marine-source rock. The family A presents by one oil sample representing Harshiyat reservoir rock and characterized by relatively high Ph/Ph ratio > 2 and δ¹³C values of their saturated and aromatic hydrocarbon fractions range from ?26.1‰ to ?24.8‰. This oil family was derived from mixed organic matter with high contribution of a terrigenous organic matter input. The family A was deposited under suboxic conditions during the Late Cretaceous age. The family B presents by two oil samples representing Ghaydah and Habshiyah reservoir rocks and characterized by relatively low Ph/Ph ratio < 2 and carbon isotope less than ?23 for their saturated and aromatic hydrocarbon fractions. These oils were generated from source rock containing high contributions of marine organic matter (e.g., algal and microbial) with minor amount of land plant source inputs that was deposited in more reducing conditions. The family B oils are consistent with those of the Paleogene Umm Er Radhuma source rock.The hydrocarbon distribution and oil composition data also indicate that the analysed oils were generated from mature source rocks with a peak oil-window maturity.     

塔里木盆地寒武系源岩地化特征及与典型海相原油对比

对27件塔里木盆地台盆区寒武系烃源岩样品进行地球化学分析及油源对比表明,寒武系烃源岩具有低姥植比、C₂₁三环萜烷/C₂₃三环萜烷比值大于1、升藿烷含量低甚至不含、伽马蜡烷含量高、C₂₈规则甾烷相对含量高、C₂₇三芳甾烷相对含量高、三芳甲藻甾烷含量高及同位素偏重等特征。寒武系烃源岩与典型寒武系、奥陶系原油油岩对比分析表明,寒武系烃源岩与T904和TD2等典型寒武系原油具有良好的亲缘性,而与台盆区大量发现的奥陶系油藏原油并无相关性,从而否定了寒武系烃源岩作为台盆区海相原油主力烃源岩的可能性。此外,塔西北地区柯坪隆起肖尔布拉克、东二沟及苏盖特布拉克等剖面烃源岩样品在生源构成上与台盆区其余寒武系烃源岩有一定差异,其母源有机质可能与奥陶系原油母源有机质具有部分相同的菌藻类构成。     

Distribution and geochemical significance of phenylphenanthrenes and their isomers in selected oils and rock extracts from the Tarim Basin,NW China

Twenty-two oil samples and eight source rock samples collected from the Tarim Basin,NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene(PhP),phenylanthracene(PhA),and binaphthyl(BiN) isomers and methylphenanthrene(MP) isomers in oils and rock extracts with different depositional environments.Phenylphenanthrenes are present in significant abundance in Mesozoic lacustrine mudstones and related oils.The relative concentrations of PhPs are quite low or below detection limit by routine gas chromatography-mass spectrometry(GC-MS) in Ordovician oils derived from marine carbonates.The ratio of 3-PhP/3-MP was used in this study to describe the relative abundance of phenylphenanthrenes to their alkylated counterparts-methylphenanthrenes.The Ordovician oils in the Tabei Uplifthave quite low 3-PhP/3-MP ratios(0.10),indicating their marine carbonate origin,associating with low Pr/Ph ratios(pristane/phytane),high ADBT/ADBF values(relative abundance of alkylated dibenzothiophenes to alkylated dibenzofurans),low C_(30) diahopane/C_(30)hopane ratios,and low Ts/(Ts+Tm)(18α-22,29,30-trisnorneohopane/(18α-22,29,30-trisnorneohopane+17α-22,29,30-trisnorhopane)) values.In contrast,the oils from Mesozoic and Paleogene sandstone reservoirs and related Mesozoic lacustrine mudstones have relatively higher 3-PhP/3-MP ratios(0.10),associating with high Pr/Pli,low ADBT/ADBF.high Ts/(Ts + Tm).and C_(30) diahopane/C_(30) hopane ratios.Therefore,the occuirence of significant amounts of phenylphenanthreiies in oils typically indicates that the organic matter of the source rocks was deposited in a suboxic environment with mudstone deposition.The phenylphenanthreiies may be effective molecular markers,indicating depositional environment and lithology of source rocks.     

BIOMARKER GEOCHEMISTRY OF PALEOGENE CRUDE OILS AND SOURCE ROCKS FROM THE RAOYANG SAG,BOHAI BAY BASIN,NE CHINA: AN OIL – SOURCE ROCK CORRELATION STUDY

This study presents a systematic geochemical analysis of Paleogene crude oils and source rocks from the Raoyang Sag in the Jizhong sub-basin of the Bohai Bay Basin (NE China). The geochemical characteristics of fifty-three oil samples from wells in four sub-sags were analysed using gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). Twenty core samples of mudstones from Members 1 and 3 of the Eocene-Oligocene Shahejie Formation were investigated for total organic carbon (TOC) content and by Rock-Eval pyrolysis and GC-MS to study their geochemistry and hydrocarbon generation potential. The oils were tentatively correlated to the source rocks. The results show that three groups of crude oils can be identified. Group I oils are characterized by high values of the gammacerane index and low values of the ratios of Pr/Ph, Ts/Tm, 20S/(20S+20R) C₂₉ steranes, ββ/(ββ+αα) C₂₉ steranes, C₂₇ diasteranes/ C₂₇ regular steranes and C₂₇/C₂₉ steranes. These oils have the lowest maturity and are interpreted to have originated from a source rock containing mixed organic matter deposited in an anoxic saline lacustrine environment. The biomarker parameter values of Group III oils are the opposite to those in Group I, and are interpreted to indicate a highly mature, terrigenous organic matter input into source rocks which were deposited in suboxic to anoxic freshwater lacustrine conditions. The parameter values of Group II oils are between those of the oils in Groups I and III, and are interpreted to indicate that the oils were generated from mixed organic matter in source rocks deposited in an anoxic brackish–saline or saline lacustrine environment. The results of the source rock analyses show that samples from Member 1 of the Shahejie Formation were deposited in an anoxic, brackish – saline or saline lacustrine environment with mixed organic matter input and are of low maturity. Source rocks in Member 3 of the Shahejie Formation were deposited in a suboxic to anoxic, brackish – saline or freshwater lacustrine environment with a terrigenous organic matter input and are of higher maturity. Correlation between rock samples and crude oils indicates that Group I oils were probably derived from Member 1 source rocks, while Group III oils were more likely generated by Member 3 source rocks. The Group II oils with transitional characteristics are likely to have a mixed source from both sets of source rocks.     

Oil-source correlation and the impact of oil-filling process on geochemical composition of the different states of oils in the Upper Triassic Chang 7 Formation,Ordos basin,China

Five crude oil samples from five wells and 33 oil-containing sandstone reservoir rock samples from six wells of Chang 7 sub-unit were systematically studied to determine hydrocarbons in these oil reservoirs whether are the mixtures of oil components derived from different source rocks or from the same source rock during oil filling process over geological times. Sequential extraction was applied to the oil-containing reservoir rocks to deserve the free and adsorbed oils. The distribution of alkanes, hopanes and steranes and the correlation diagram of Pr/n-C₁₇ versus Ph/n-C₁₈ show that these oil components and crude oils have similar parent materials. And on this basis we compared the thermal maturity of the crude oils, the free oils and adsorbed oils and found that the thermal maturity of these oils is different. The cross plot of C₂₉αα-20S/(20S+20R) versus C₂₉ββ/(αα+ ββ) and the correlation diagram of Pr/n-C₁₇ versus Ph/n-C₁₈ both show that the crude oils have highest thermal maturity, followed by the free oils and then the adsorbed oils. The ratios of ∑C₂₁^?/∑C₂₂⁺ for the crude oils and free oils are greater than the adsorbed oils, indicating the crude oils and free oils have suffered more thermal stress and extensive cracking than that of the adsorbed oils. These geochemical data reveal that hydrocarbons in these oil reservoirs and crude oils were derived from the same source rock with different thermal maturity over geological times.     

Geochemistry characteristics of high-mature source rock extracts and using various approaches to discriminate the indigenity

A total of 11 core samples of Cambrian source rocks and 2 Cambrian-sourced crude oils (TD2, T904) were analyzed. High content of total organic matters indicates a good to excellent source rocks. However, high maturity was indicated by high T_max values and very low content of HI index and S₁+S_2. The relative intact alkanes can be detected in most samples with no odd/even predominance. A series of relatively high abundance of terpanes and steranes can be detected on m/z 191 and m/z 217 chromatograms, respectively. Ratios of C₂₁/C₂₃ tricyclic terpanes are greater than 1.0. All samples of Yuli 1 and Tadong 2 show high abundance of C₂₆～C₂₈ triaromatic steroids and triaromatic dinosteroids, with ratios of (C₂₆+C₂₇) TAS/C₂₈TAS and TDSI greater than 1.0 and 0.62, respectively. Oil source rocks correlation between sampled rock extracts and typical Cambrian oils reveals that high-postmature Cambrian source rock extracts are well consistent with those two typical Cambrian oils that are usually used as end members oils represented by Cambrian-sourced oils. Three approaches were proposed to discriminate indigenity of high-postmature source rocks.     

渤海湾盆地济阳坳陷埕岛—桩西潜山油气特征与来源

潜山油气藏具有多种油气来源和充注成藏方式。为揭示渤海湾盆地济阳坳陷潜山油气藏的形成过程,以油气物性、地球化学特征为基础,分析了埕岛—桩西潜山带的油气来源及充注方式。结果表明：研究区原油来自低等生物为主的湖相烃源岩,天然气为腐泥型干酪根在热解生烃过程中产生的原油伴生气;受多源供烃的影响,油气物性和地球化学特征在不同层系之间无明显差异,但在不同构造带间差异显著。埕北11潜山原油中4?甲基甾烷不发育,是埕北凹陷沙三段烃源岩生成的油气沿埕北断层垂向注入而形成;埕北20潜山的原油成熟度相对较低、伽马蜡烷含量高低不等,为来自沙南凹陷沙一段和沙三段的混源油,通过不整合侧向充注而聚集;埕北30潜山和桩海潜山的原油成熟度高,是黄河口凹陷沙三段烃源岩生成的油气沿埕北30断层和供烃窗口充注而形成;桩西潜山的油气来自孤北洼陷沙三段,经桩南断层从供烃窗口充注进入潜山。     

库车坳陷陆相烃源岩及原油中的氧芴系列化合物

分析了塔里木盆地库车坳陷三叠系、侏罗系7个湖相泥岩和3个煤岩以及5个陆相原油样品中的萘、联苯、氧芴、芴、二笨并噻吩、菲、蒽、惹烯、和苯并蒽系列10种重要芳烃化合物.研究发现,氧芴系列化合物在煤岩样品中丰度高,在湖相泥岩样品中丰度低.据岩、油芳烃总离子流图中氧芴系列化合物,特别是氧芴之相对丰度对比研究结果判识,沙3井白垩系原油、羊塔克5井下第三系和白垩系原油以及却勒1井下第三系原油可能为库车坳陷下侏罗统阳霞组或中侏罗统克孜勒努尔组的煤成油,英买7井奥陶系原油和牙哈1井下第三系原油可能为库车坳陷三叠系、侏罗系湖相泥岩成油.该研究结果对进一步开展库车坳陷油源对比研究和油气勘探具有一定的意义.     

API gravities,vanadium, nickel,sulfur, and their relation to gross composition: Implications for the origin and maturation of crude oils in Western Desert,Egypt

In the present study, the geochemical analyses of API gravities, vanadium, nickel, sulfur, and bulk composition were performed on eight samples from productive wells in Gindi, South Deep Abu-gharadig, Abu-gharadig, Dahab-Merier, and Faghure basins locates in the North Western Desert. The results were used to describe the source organic matter input, depositional environment, assess the degree of thermal maturity, and to correlate between crude oils to determine the genetic relationship between hydrocarbon generation and their source rock for the studied oil samples. The results showed that a wide range of crude oil parameters exists in this data, indicating that a variety of oil types is represented. Crude oils range from unaltered to altered by vanadium, nickel, and sulfur concentrations, V/Ni and saturate fraction were used to classify the oils. Oils are classified into two groups. Group I contains oil samples from Gindi, South deep Abu-gharadig and Abu-gharadig, and Dahab-Merier that are generated from organic matter input deposited in marine environment under anoxic to suboxic conditions. Group II from Faghur basin possess high Pr/Ph ratios suggesting high contribution of terreginous organic matter deposited under relatively oxic conditions.     

海拉尔盆地乌尔逊—贝尔凹陷白垩系原油地球化学特征及油源对比

对海拉尔盆地乌尔逊凹陷和贝尔凹陷共21个原油和油砂样品进行GC、GC-MS和非烃含氮化合物测试分析,根据饱和烃、轻烃和甾萜类生物标志化合物的分析资料,全面剖析了海拉尔盆地乌尔逊-贝尔凹陷白垩系原油的地球化学特征,并通过油源对比确定了其主力烃源层。研究结果表明,海拉尔盆地贝尔凹陷和乌尔逊凹陷原油存在2种成因类型:第一类油饱和烃C17—C23具正构烷烃优势,呈单峰型分布,Pr/Ph>1(1~2.88),C27—C29甾烷呈"V"型分布,伽马蜡烷含量较低,表征淡水湖相沉积环境;第二类油具有饱和烃低碳正构烷烃优势,Pr/Ph<1,孕甾烷、C27重排甾烷含量较低,伽马蜡烷不发育,表征煤系地层原油。油源对比揭示,原油来自2套不同沉积环境的源岩,展示了海拉尔盆地良好的烃源条件。     

硅酸盐钻井液技术在牛斜114井中的应用

胜利油田牛庄洼陷东部主力含油层是沙三段,油藏类型为沉积岩油藏.该地区馆陶组以上地层成岩性差,易造浆;下部地层易坍塌,易漏;底部含有膏泥岩层,需注意防卡、防膏岩水侵.研究了硅酸盐钻井液配方和性能,并对其抑制性、抗固相污染及盐膏污染能力进行了评价.实验证明,硅酸盐钻井液具有良好的抑制泥页岩水化膨胀能力,并具有一定的抗盐膏抗固相污染能力.硅酸盐钻井液体系在牛斜114井进行了现场应用,密度达到了1.50 g/cm3,该钻井液在高pH值环境下能够防止地层的垮塌,起到了保护井壁的作用,悬浮携岩能力强,保护油气层效果好.     

渤海湾盆地惠民凹陷临南洼陷沙河街组原油地球化学特征及油源对比

惠民凹陷是渤海湾盆地济阳坳陷中的一个富油气单元。系统研究惠民凹陷临南洼陷20个原油样品和4个烃源岩样品地球化学特征,分析其成熟度、沉积环境和有机质来源,利用烃源岩和原油生物标志化合物参数建立油-岩关系,筛选有效参数运用交会图和聚类统计划分原油类型和进行油源对比。研究区原油已进入成熟阶段,生油母质的沉积环境为弱氧化-弱还原的湖沼相-淡水湖相,具有陆相湖盆混合型母质特征。总体上,研究区原油有较高的饱和烃含量和较低的胶质及沥青质含量,正构烷烃为"平台式"双峰形态分布,伽马蜡烷含量较低,4-甲基甾烷含量较高。研究区内不同地区原油的地球化学特征存在一定差别,可按地区分为南带和北带。相比南带的原油,北带原油样品中4-甲基甾烷/C29R、Ts/Tm比值较低,而C29降藿烷/C29降新藿烷、1,2,7-/1,2,6-三甲基萘、菲/∑甲基菲较高。研究区沙四段烃源岩有机质类型为Ⅲ型,有机质丰度较低;沙三段烃源岩有机质以Ⅱ型为主,有机质丰度较高,其中,沙三下亚段和中亚段是临南洼陷的主力烃源岩。通过系统对比研究区原油和烃源岩的地球化学特征,认为临南洼陷沙三、沙四段原油来自沙三下、中亚段烃源岩。     

BIOMARKER CHARACTERISTICS OF CRUDE OILS FROM THE MURZUQ BASIN,SW LIBYA

Twenty crude oil samples from the Murzuq Basin, SW Libya (A‐, R‐ and I‐Fields in Blocks NC115 and NC186) have been investigated by a variety of organic geochemical methods. Based on biomarker distributions (e.g. n‐alkanes, isoprenoids, terpanes and steranes), the source of the oils is interpreted to be composed of mixed marine/terrigenous organic matter. The values of the Pr/Ph ratio (1.36–2.1), C₃₀‐diahopane / C₂₉ Ts ratio and diasterane / sterane ratio, together with the low values of the C₂₉/ C₃₀‐hopane ratio and the cross‐plot of the dibenzothiophene/phenanthrene ratio (DBT/P) versus Pr/Ph ratio in most of oil samples, suggest that the oils were sourced from marine clay‐rich sediments deposited in mild anoxic depositional environments. Assessment of thermal maturity based on phenanthrenes, aromatic steroids (e.g. monoaromatic (MA) and triaromatic (TA) steroid hydrocarbons), together with terpanes, and diasterane/sterane ratios, indicates that crude oils from A‐Field are at high levels of thermal maturity, while oils from Rand I‐Fields are at intermediate levels of thermal maturity. Based on the distributions of n‐alkanes and the absence of 25‐norhopanes in all of the crude oils analysed, none of the oils appear to have been biodegraded. Correlation of the crude oils points to a single genetic family and this is supported by the stable carbon isotope values. The oils can be divided into two sub‐families based on the differences in maturities, as shown in a Pr/nC₁₇ versus Ph/nC₁₈ cross‐plot. Sub‐family‐A is represented by the highly mature oils from A‐Field. Sub‐family‐B comprises the less mature oils from R‐ and I‐Fields. The two sub‐families may represent different source kitchens of different thermal maturity or different migration pathways. In summary, the geochemical characteristics of oil samples from A‐, R‐, and I‐Fields suggest that all the crude oils were generated from similar source rocks. Depositional environment conditions and advanced thermal maturities of these oils are consistent with previously published geochemical interpretations of the Rhuddanian “hot shale” in the Tanezzuft Formation, which is thought to be the main source rock in the Murzuq Basin.     

Organic geochemistry investigations of crude oils from Bayoot oilfield in the Masila Basin,east Yemen and their implication for origin of organic matter and source-related type

Thirteen crude oil samples from fractured basement reservoir rocks in the Bayoot oilfield, Masila Basin were studied to describe oil characteristics and to provide information on the source of organic matter input and the genetic link between oils and their potential source rock in the basin. The bulk geochemical results of whole oil and gasoline hydrocarbons indicate that the Bayoot oils are normal crude oil, with high hydrocarbons of more than 60%. The hydrocarbons are dominated by normal, branched and cyclic alkanes a substantial of the light aromatic compounds, suggesting aliphatic oil-prone kerogen. The high abundant of normal, branched and cyclic alkanes also indicate that the Bayoot oils are not biodegradation oils.The biomarker distributions of isoprenoid, hopane, aromatic and sterane and their cross and triangular plots suggest that the Bayoot oils are grouped into one genetic family and were generated from marine clay-rich source rock that received mixed organic matter and deposited under suboxic conditions. The biomarker distributions of the Bayoot oils are consistent with those of the Late Jurassic Madbi source rock in the basin. Biomarker maturity and oil compositions data also indicate that the Bayoot oils were generated from mature source rock with peak oil-window maturity.     

鄂尔多斯盆地林镇地区原油地球化学特征

林镇地区是鄂尔多斯盆地中生界油气勘探新区,近几年在该地区发现了延长组上部和延安组下部的复合油藏。通过对鄂尔多斯盆地林镇地区原油样品和区域内烃源岩样品进行系统采集和GC-MS分析,研究了原油和烃源岩中生物标志化合物的组成和分布特征,探讨了延安组延6、延8、延9和延长组长3等油层组原油的成因;油源对比研究表明该地区延安组与延长组原油的地球化学特征均与上三叠统延长组长7烃源岩具有亲缘关系,说明原油主要来源于长7烃源岩。这些研究成果为林镇地区石油勘探开发提供了科学依据。     

黔北地区下寒武统页岩孔隙结构特征及其含气性能

通过对黔北地区下寒武统牛蹄塘组和杷榔组页岩岩心样品的有机碳含量、矿物组成、孔隙结构及甲烷等温吸附容量等分析,探讨了页岩孔隙结构的发育特征、影响因素以及有机质对页岩甲烷吸附容量的影响。研究表明,下寒武统页岩具有低孔低渗的特征,页岩比表面积介于5.64~28.29cm²/g之间,NLDFT微孔及中孔体积分别为0.02~0.54cm³/100g及0.53~3.38cm³/100g。孔隙度、BET比表面积以及微孔体积与TOC含量均呈正相关,显示了页岩有机质对孔隙的控制作用;而过高的TOC含量对页岩有机质孔隙可能有一定的抑制作用。此外,黏土矿物对孔隙也有一定贡献。下寒武统页岩吸附量为0.30~3.71cm³/g(12MPa),Langmuir最大吸附量介于0.41~4.22cm³/g之间,吸附量与有机碳含量之间大体呈正相关,但高有机碳含量的页岩样品由于具有低的微孔体积及比表面积而表现出相对低的甲烷吸附量。     

Recognition of the Source Rock Using Biomarkers From Eocene Reservoir Oils

The source rocks of 20 oils in Eocene reservoir from Lengdong oil field have been evaluated using geochemical biomarkers. Most of the oil samples have been undergone light to moderate biodegradation and four of these oil samples suffered heavy biodegradation. The oils were originated from low maturity source rocks within early to middle oil window according to the thermal-maturation-dependent biomarker ratios. Source-related biomarkers indicated that the oils originated from carbonate source rock possessed both high plants and algae organic matter input, while high plants' input was dominant in almost all the oils. The source rocks concerning the oils were deposited under anoxic to suboxic (low EH), salinity to hypersaline, and lacustrine environment with deep water.