An Experimental Study of Rheological Properties of Nigerian Waxy Crude Oil

Abstract

Nigerian crude oils are known for their good quality (low sulfur, high American Petroleum Institute gravity). However, similar to any other paraffinic-based crudes, most Nigerian crudes contain moderate to high contents of paraffinic waxes. These waxy crudes exhibit non-Newtonian flow behavior at temperatures below the cloud point because of wax crystallization. In order to accurately predict flowing and static temperature profiles, design waxy crude oil pipelines, evaluate flow interruption scenarios, and start up requirements in the handling of waxy crude oils, the effect of temperature and shear rate on the rheology of crude oils must be determined. This work presented some experimental results on the rheology of two waxy crude oils produced from different Nigerian oil fields. A Brookfield DV-III ultraprogrammable rheometer (Brookfield Engineering Laboratories, Middleboro, MA) was utilized. The temperature dependence of rheological properties and thixotropy of these crudes were investigated. The influence of some petroleum-based diluents to depress the wax appearance temperature (WAT), their effect on the thixotropic/yield pseudoplastic behavior of two Nigerian crudes were studied and it was observed that lower wax content crude has higher tendency to regain its cohesive lattice bonding (yield strength) when left undisturbed for some days at its gel point after agitation. The experimental results showed that the addition of petroleum-based diluents to the lower wax content crude oil leads to its lost some of its yield strength regaining capacity.     

COMPARISON OF KUWAITI CRUDE OILS,COMPOSITIONAL ANALYSIS USING GAS CHROMATOGRAPHY TECHNIQUES

Abstract

High resolution capillary gas chromatography studies, were performed to compare and group oils from three different Kuwaiti wells completed in the same structural sand. These groupings contributed to the identification of the nature, origin and maturity of the crudes under study. Analysing the fingerprint gas chromatograms of the three Kuwaiti crude oils, it was found that the crudes are from a carbonate rock source origin. The chromatographic fingerprints showed that two of these crudes are almost identical in composition and belong to the same reservoir, while the other crude is different in its composition reservoir source.     

Crude Oil Blending Effects on Asphaltene Stability in Refinery Fouling

Abstract

It has been known for some time that blending of incompatible crude oils may lead to asphaltene destabilization. The link between such asphaltene destabilization and their subsequent fouling of equipment in refinery operations was established in this study. Several refinery crude blends known to cause problems ranging from desalter upsets to fouling in pre-heat train were studied. Stability analysis of the crudes and their blends using a solvent titration method with a laser-based solids detection system showed that destabilization of the asphaltenes is caused, in the main, by blending of incompatible crudes. The stability data showed that the individual crudes had a high, medium, or low fouling potential. The blends of those that are incompatible however showed increased instability and may be the cause of the fouling problems encountered in the pre-heat train heat exchangers during their processing.     

Applications of Polycyclic Aromatic Hydrocarbons to Assess the Source and Thermal Maturity of the Crude Oils from the Lower Indus Basin,Pakistan

Abstract

A suite of six crude oils from Lower Indus Basin, Pakistan, were analyzed for geochemical characterization of source organic matter (OM) and thermal maturity. Distribution of polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, alkylphenanthrenes, alkyldibenzothiophenes, and aromatic biomarkers were reported from aromatic fractions of the crude oils. The aromatic hydrocarbons parameters revealed a higher thermal maturity of OM of source rock-generated Lower Indus Basin oils. Calculated vitrinite reflectance values from the methylphenanthrenes index 1 (MPI-1) and methyldibenzothiophene ratio (MDR) indicate that most of the oils reached a late oil generation window of thermal maturity. PAH distributions revealed the oils of two different origins are present in the Lower Indus Basin; two oil samples indicate aquatic source of OM and the aromatic biomarker distributions of retene, 1-MP, and 1,7-DMP indicate a significant contribution of land plant OM in the other four oils. This is the first study to report the distribution of aromatic hydrocarbons from Lower Indus Basin crude oils.     

RELATIONSHIP BETWEEN PETROLEUM COMPOSITION AND DEPOSITIONAL ENVIRONMENT OF PETROLEUM SOURCE ROCKS FROM THE GULF OF SUEZ AND THE WESTERN DESERT OF EGYPT

ABSTRACT

Crude oils from the Gulf of Suez and the North Western Desert of Egypt have been analyzed for geochemical biomarkers using GC and GC-MS techniques. The biomarker compositions of the crude oils have been used to differentiate crude oils of non-marine, normal marine and marine carbonate sources. The geochemical features of Zaafarana crude oil from the Gulf of Suez Basin indicate a marine carbonate depositional setting. One crude oil from Budran however, possesses geochemical characteristics consistent with an origin from source rock deposited in normal marine conditions. Bahar and Morgan show normal marine source rock deposition environment with terrigenous organic matter input. On the other hand, the crude oils from the North Western Desert have bulk and biomarker characteristics cosistent with non-marine depositional setting, with the exception of one oil sample which appears to have a mixed marine/terrestrial sources. The presence of oleanane in some of these oils suggests source rocks deposited in deltaic or near shore environment in Post Cretaceous Basin.     

南堡凹陷原油芳烃地球化学特征

通过对南堡凹陷原油GC-MS分析,研究了原油芳烃组成特征,探讨了原油成因。结果表明,南堡凹陷原油主要形成于弱氧化的淡水湖相沉积,为成熟原油。通过芳烃化合物组成及萘系列、联苯系列化合物内部相对丰度关系表明．沙河街组原油与东营组、馆陶组原油在源岩有机质输入方面有一定的差异,其中东营组和馆陶组原油有机质输入中高等植物有较大贡献,可能来源于南堡凹陷东三段或沙一段烃源岩,而沙河街组原油来源于沙三段烃源岩。     

Emerging Role of Biorefining of Heavier Crude Oils and Integration of Biorefining with Petroleum Refineries in the Future

Abstract

With the depletion of light and sweet crude oils, reliance and dependence on heavier crude oils will increase. However, refining of heavier crudes generates not only larger amounts of heavier products, but is also costly and involves problems of corrosion of equipment and poisoning of costly catalysts. Presence of asphaltenes, asphaltols, S-heterocyclics, N-heterocyclics, organometallics, and metal sulphides, in crude oils results in poisoning of costly catalysts used for FCC and hydrocracking. Thus, there is a need to remove sulfur, nitrogen, and toxic metals from heavier crude oils and also a necessity of degrading larger higher molecular weight-bearing complex molecules to lower molecular weight-bearing lighter crudes. Conventional physical and chemical refining techniques may not be easily applied to heavier crudes. Thus, there is a need to develop simpler biorefining techniques to not only biodegrade the heavier asphaltenes and asphaltols, but also to remove sulfur, nitrogen, and toxic metals from crude oils. This paper describes the studies of biorefining of crude oils, diesel, and gasoline, which includes studies on microbial degradation, biodesulfurization, biodenitrogenation, and biodemetallation of crude oil using not only mesophilic, but also thermophilic bacteria. The role of microbial isolation from geographically diverse sites, chemotaxis, and genetic engineering tools, such as gene conversion, gene duplication, transportation, and biovehicles (plasmids and transposons) and rearrangement of DNA fragments, is vital in these studies. There is a need to genetically develop a designer microbe which can help in biorefining of heavier crude oils efficiently and economically. Bioprocess engineering of heavier crudes may include pre-biorefining, during-biorefining, and post-biorefining techniques. In the future, an integration of biorefining with petroleum refining by rendering not only heavier crudes as lighter crudes through microbial degradation, but also through biodesulfurization, biodenitrogenation, and biodemetallation may be required.     

类异戊二烯烷烃非对映异构体的色谱—质谱分离及条件优化研究

运用GC-MS对准噶尔盆地煤样及孤岛稠油样中的饱和烃生物标志化合物进行分析,首次检测到了丰富的无环类异戊二烯烷烃类化合物:iC₁₈(2,6,10-三甲基十五烷)、Pr(2,6,10,14-四甲基十五烷)和Ph(2,6,10,14-四甲基十六烷)及其非对映异构体。并考察了色谱柱类型、长度、程序升温等对类异戊二烯烷烃非对映异构体分离效果的影响,同时确定了程序升温色谱分离类异戊二烯烷烃非对映异构体的最佳条件,对样品中的降姥鲛烷、姥鲛烷、植烷与其非对映异构体进行了分离,对姥鲛烷、植烷的分离度最高可分别达0.7及0.9。      

COMPARISON OF KUWAITI CRUDE OILS, COMPOSITIONAL ANALYSIS USING GAS CHROMATOGRAPHY TECHNIQUES

High resolution capillary gas chromatography studies, were performed to compare and group oils from three different Kuwaiti wells completed in the same structural sand. These groupings contributed to the identification of the nature, origin and maturity of the crudes under study. Analysing the fingerprint gas chromatograms of the three Kuwaiti crude oils, it was found that the crudes are from a carbonate rock source origin. The chromatographic fingerprints showed that two of these crudes are almost identical in composition and belong to the same reservoir, while the other crude is different in its composition reservoir source.     

Effects of Steam Soak on the Two Eocene Heavy Crude Oils from the Urdaneta District (Venezuela)

Abstract

Simulation studies of steam-alkaline injection were made using the only two Eocene viscous crude oils from the Urdaneta District (Venezuela). Reactors were stainless steel and work conditions were a temperature of 200°C, 20 days' reaction time, and an alkali concentration of 4000 ppm. The aim of this work was to evaluate chemistry changes in the saturates and aromatics of both crudes as a result of the crude-alkaline-solid phase interactions. There were significant variations in the biomarker distribution in the two crudes (higher for the Boscán crude), particularly in the mono- and triaromatic steranes, and benzotiophenes of the two crudes.     

Effect of Crude Oil Composition and Blending on Flowing Properties

Abstract

The effect of crude oil n-paraffin molecular weight distribution on wax crystallization risk was studied. Sixteen highly paraffinic crude oils from Eastern Venezuela were characterized, in terms of hydrocarbon family distribution, by High Temperature Simulate Distillation (HTSD), Gel Permeation Chromatography (GPC), and wax content. n-Paraffin chain length was correlated with crude oil cloud point and pour point. It was demonstrated that high molecular weight linear paraffins are responsible for crude oil wax precipitation. A quantitative correlation between molecular weight distribution and crude oil flowing properties was also obtained. It was found that the wider the molecular weight distribution, the lower is the wax crystallization risk. Blends of different paraffinic crude oils were prepared and their flowing properties were evaluated in comparison with the original crudes. Cloud points below the mean value were obtained. In some cases, a synergistic effect was observed (cloud points below the minimum of the two crude oils). Blends of some of these crudes with condensates afforded improvements on crude oil flow and a reduction of wax crystallization tendency (cloud point). This phenomenon can be attributed to a combination of two factors: I. increases in C24-n-paraffins, and II. a wider molecular weight distribution.     

The Importance of Asphaltene Content in Petroleum III—New Criteria for Prediction of Incompatibility in Crude Oil Blends

Abstract

Our previous results have shown that macroscopic properties of petroleum media may undergo abrupt changes caused by currently underinvestigated microscopic phase transitions in asphaltene nanocolloids. In particular, native crudes of diverse origin exhibit sharp viscosity and density peaking at phase boundaries, defined by specific asphaltene contents. We suggest that when these asphaltene contents are approached in blends of several crude oils, severe incompatibility may be observed; for example, massive appearance of solid sediments. New criteria for most incompatible and for most compatible blends are formulated in terms of grams per liter of asphaltene concentrations.     

东濮凹陷西斜坡地区原油成熟度

胡状集和庆祖集油田是东濮凹陷西斜坡地区的两个主要油田,原油主要分布在长垣断层与石家集断层之间二台阶构造带上,该区原油具有饱和烃含量低、含蜡量高、碳同位素较重的特征。利用GC-MS技术对原油分析结果显示,饱和烃馏分中Cg甾烷立体异构体比值、三降藿烷w(Ts)/w(Tm)比值普遍较低,这些参数值与我国不同盆地典型低熟原油分布范围十分相似。芳烃馏分中检出了反映低成熟阶段生物标志物一-烷基噻吩、四氢噻吩等含硫化合物及多羟基维生素E系列。综合分析认为,胡状集和庆祖集油田的原油为低成熟原油,而非成熟原油。     

典型海相油和典型煤成油轻烃组成特征及地球化学意义

通过对塔里木盆地塔中隆起典型海相原油和吐哈盆地典型煤成油的轻烃组分、Mango参数和成熟度等分析后发现:2类原油轻烃组分含量差异明显，塔中隆起海相油富含正庚烷,吐哈盆地煤成油则富含甲基环己烷;塔中隆起海相油Mango参数K₁值分布在0.97~1.19之间，与Mango所报道的结果相一致，而吐哈盆地煤成油的K₁值却异常高（1.35~1.66）；塔中隆起海相油成熟度参数庚烷值(32.3%~45.4%)和异庚烷值(1.9~3.7)高于煤成油，已处于高成熟阶段，塔中隆起典型海相油的形成温度要明显高于吐哈盆地煤成油。     

Crude Oil Blending Effects on Asphaltene Stability in Refinery Fouling

It has been known for some time that blending of incompatible crude oils may lead to asphaltene destabilization. The link between such asphaltene destabilization and their subsequent fouling of equipment in refinery operations was established in this study. Several refinery crude blends known to cause problems ranging from desalter upsets to fouling in pre-heat train were studied. Stability analysis of the crudes and their blends using a solvent titration method with a laser-based solids detection system showed that destabilization of the asphaltenes is caused, in the main, by blending of incompatible crudes. The stability data showed that the individual crudes had a high, medium, or low fouling potential. The blends of those that are incompatible however showed increased instability and may be the cause of the fouling problems encountered in the pre-heat train heat exchangers during their processing.     

金刚烷类化合物与库车坳陷克拉2构造凝析油的形成机理研究

借助于色谱和色谱—质谱分析技术,对库车坳陷克拉2构造和牙哈构造带原油中轻烃、链烷烃、多环芳烃、甾萜烷生物标志化合物和金刚烷类化合物进行了系统分析。结果表明：克拉2构造凝析油的轻烃和全烃组成中特别富含芳烃化合物,甾烷、萜烷中明显富含低分子量化合物如三环萜烷系列、孕甾烷和升孕甾烷,这一特征明显不同于牙哈构造带来源相似的原油和凝析油,显示其形成机理的特殊性。此外,克拉2构造凝析油和牙哈构造带原油中普遍存在烷基单金刚烷系列和烷基双金刚烷系列,但只有克拉2构造凝析油中检测出烷基三金刚烷系列。定量结果表明克拉2构造凝析油中金刚烷类化合物的浓度较牙哈构造带原油高约一个数量级,这些特征表明克拉2构造凝析油的成熟度明显高于牙哈构造带原油。依据甲基单金刚烷指数MAI和甲基双金刚烷指数MDI与镜质体反射率RO间的对应关系,发现克拉2构造凝析油对应的RO值约为1.9%,热裂解程度大于97%,属于典型的热裂解原油,这与富含芳烃的特征吻合;而牙哈构造带原油对应的RO值约为1.2%～1.4%,且不同构造单元原油的热裂解程度变化较大,介于20%～80%之间,这与后期高成熟油气侵入程度有关。     

一种新的原油轻烃分类法——塔里木盆地原油分类及其地化特征

根据Mango提出原油中轻烃成因的假说--稳态催化成因,按“母体”(甲基己烷类)占C7化合物的百分数与两类“子体”(二甲基戊烷类+3-乙基戊烷;1,1和1,3-二甲基环戊烷类)丰度比的关系图,将塔里木盆地不同地区、层位的141个原油分成A、B两大类和四亚类。为了验证分类的有效性和研究影响分类的因素,对各类原油中微量元素、饱和烃的C₁₄⁺色谱、生标组成及其分布规律进行了综合研究。鉴于各类原油具明显的地化特征区别,且在地区、层位上有一定的规律性,证实根据Mango假说提出的新的原油轻烃分类方法在塔里木盆地是有效的,在高熟的油气区更有应用前景。研究成果支持Mango的观点,即影响轻烃分类的主要因素可能是受沉积环境控制的催化剂组成,此外干酪根类型等也可能有一定的影响。     

Utilization of Trace Metals and Sulfur Contents in Correlating Crude Oils and Petroleum Heavy Ends

Abstract

The asphaltic components of four crude oils were analyzed for their V, Ni and Co contents. The metallic concentrations increased with increasing the molecular weight and the polarity of the fraction and the highest concentration is associated with asphaltene fraction. The V, Ni and Co might have been incorporated during the genesis of the parent crudes as the V/Ni, V/Co and Ni/Co markers are fairly uniform in the asphaltenes and unfractionated asphalts. In addition, the total V and Ni together with S were measured in twelve crude oils from different geographic locations and geologic ages. The Ni/S marker can be considered as characteristic marker for all the crudes studied. On the other hand, V/S marker is too precise in correlating with the geologic age of the oil and is decreasing by maturation.     

一种新的原油轻烃分类法——塔里木盆地原油分类及其地化特征

根据Mango提出原油中轻烃成因的假说--稳态催化成因,按“母体”(甲基己烷类)占C7化合物的百分数与两类“子体”(二甲基戊烷类+3-乙基戊烷;1,1和1,3-二甲基环戊烷类)丰度比的关系图,将塔里木盆地不同地区、层位的141个原油分成A、B两大类和四亚类。为了验证分类的有效性和研究影响分类的因素,对各类原油中微量元素、饱和烃的C₁₄⁺色谱、生标组成及其分布规律进行了综合研究。鉴于各类原油具明显的地化特征区别,且在地区、层位上有一定的规律性,证实根据Mango假说提出的新的原油轻烃分类方法在塔里木盆地是有效的,在高熟的油气区更有应用前景。研究成果支持Mango的观点,即影响轻烃分类的主要因素可能是受沉积环境控制的催化剂组成,此外干酪根类型等也可能有一定的影响。     

IN‐RESERVOIR FRACTIONATION AND THE ACCUMULATION OF OIL AND CONDENSATES IN THE SURMA BASIN,NE BANGLADESH

Petroleum in the Surma basin, NE Bangladesh (part of the Bengal Basin) ranges from waxy crude oils to condensates. The origin and source rocks of these hydrocarbons were investigated based on the distributions of saturated and aromatic hydrocarbons in 20 oil samples from seven oil and gas fields. The relative compositions of pristane, phytane and adjacent n‐alkanes suggest that the source rock was deposited in a non‐marine setting. The abundance and similar distribution of biphenyls, cadalene and bicadinanes in most of the crude oils and condensates indicates a significant supply of higher‐plant derived organic matter to the source rocks. Maturity levels of the crude oils and condensates from the Surma basin correspond to calculated vitrinite reflectance (R_c) values of 1.0–1.3%, indicating hydrocarbon expulsion from the source rock at a comparatively high maturity level. The R_c values of oils from the Titas field in the southern margin of the Surma basin are relatively low (0.8–1.0%). Some oils were severely biodegraded. The similar distribution of diamondoid hydrocarbons in both biodegraded and non‐biodegraded oils indicated similar types of source rocks and similar maturity levels to those of oils from the Surma basin. The Oligocene Jenam Shale and/or underlying non‐marine deposits located at greater depths may be potential source rocks. The diversity of the petroleum in the Surma basin was likely due to evaporative fractionation, resulting in residual waxy oils and lighter condensates which subsequently underwent tertiary migration and re‐accumulation. Evaporative fractionation due to modification of the reservoir structure occurred during and after the Pliocene, when large‐scale tectonic deformation occurred in and around the Bengal Basin.