Geological Conditions Favourable for High-Wax Oil Enrichment in Damintun Depression,Bohai Bay Basin

ABSTRACT： The Damintun （大民屯） depression, a small （about 800km^2 in area） subunit in the Bohai （渤海） Bay basin, hosts nearly 2×10^8 t of high-wax oils with wax contents up to 60%. The high-wax oils have high consolidation temperatures and viscosities. The high-wax oils were generated from the fourth member of the Shahejie Formation （Es4）, which is also important source rocks for oils in other subunits of the Bohai Bay basin. Yet high-wax oils have not been found in significant volumes elsewhere in the Bohai Bay basin. Geological conditions favourable for high-wax oil enrichment were studied. This study shows that the unusual concentrations of high-wax oils in the depression seem to result from at least three different factors： （1） the presence of organic-matter rich source rocks which were prone to generate wax-rich hydrocarbons; （2） the formation of early overpressures which increased the expul- sion efficiency of waxy hydrocarbons; and （3） reductions in subsidence rate and basal heat flows, which minimized the thermal cracking of high molecular-weight （waxy） hydrocarbons, and therefore prevented the high-wax oils from being transformed into less waxy equivalents.

Lacustrine biomass: An significant precursor of high wax oil

Although a variety of precursors have been proposed for the formation of high molecular weight hydro-carbons (HMWHCs) in crude oil, their precise origin re-mains elusive. Quantitative studies of macrocrystalline wax and microcrystalline wax content of source rock extracts from the Damintun depression, Liaohe Basin, a typical high wax producing area, coupled with microscopical maceral composition studies and pyrolysis-GC analysis indicate that oil shale enriched in lacustrine biomass makes a primary contribution to wax in oil. The main precursors of high wax oil are lacustrine alginites and their amorphous matrix, which are highly aliphatic in nature and have high genera-tive potential for HMWHCs. Wax generation efficiency could be affected by organic material abundance and matur-ity. The high abundance and low maturity of organic mate-rial are favorite for the formation of high quantity of wax, which declines with decreasing organic abundance and in-creasing thermal maturity. This suggests that wax is derived from organic-rich lacustrine biomass at early stages of maturation (RO = 0.4%—0.7%). Although the contribution of high plant cuticular wax and sporopollen cannot be ruled out, lacustrine biomass is more important in the formation of high wax oil.

Crude oil wax:A review on formation,experimentation,prediction,and remediation techniques

Wax deposition during crude oil production,transportation,and processing has been a headache since the early days of oil utilization.It may lead to low mobility ratios,blockage of production tubing/pipelines as well as fouling of surface and processing facilities,among others.These snags cause massive financial constraints increasing projects’turnover.Decades of meticulous research have been dedicated to this problem that is worth a review.Thus,this paper reviews the mechanisms,experimentation,thermodynamic and kinetic modeling,prediction,and remediation techniques of wax deposition.An overall assessment suggests that available models are more accurate for single than multi-phase flows while the kind of remediation and deployment depend on the environment and severity level.In severe cases,both chemical and mechanical are synergistically deployed.Moreover,future prospective research areas that require attention are proposed.Generally,this review could be a valuable tool for novice researchers as well as a foundation for further research on this topic.

Prediction Model Based on the Grey Theory for Tackling Wax Deposition in Oil Pipelines

Problems involving wax deposition threaten seriously crude pipelines both economically and operationally. Wax deposition in oil pipelines is a complicated problem having a number of uncertainties and indeterminations. The Grey System Theory is a suitable theory for coping with systems in which some information is clear and some is not, so it is an adequate model for studying the process of wax deposition. In order to predict accurately wax deposition along a pipeline, the Grey Model was applied to fit the data of wax deposition rate and the thickness of the deposited wax layer on the pipe-wall, and to give accurate forecast on wax deposition in oil pipelines. The results showed that the average residential error of the Grey Prediction Model is smaller than 2%. They further showed that this model exhibited high prediction accuracy. Our investigation proved that the Grey Model is a viable means for forecasting wax deposition. These findings offer valuable references for the oil industry and for firms dealing with wax cleaning in oil pipelines.

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 C12 to C60 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 C50–C60were found, which were not practically detected in the corresponding wax deposits.

The extraction and preliminary characterization of paint oil and paint wax

研究漆籽油和漆蜡提取的最佳工艺,进行单因素实验,对不同品种漆油进了红外分析。结果表明：漆蜡的最佳工艺条件是：石油醚（30℃～60℃）作为提取剂,提取温度为50℃,固液比为1∶20,提取时间12h,漆籽皮的目数是大于100目;漆油的最佳工艺条件是：石油醚（30℃～60℃）作为提取剂,提取温度为50℃,固液比为1∶30,提取时间3h,漆籽皮的目数是大于100目。通过萃取所得的漆油在红外图谱上出峰位置基本一致,表明其化学成分基本相同。

Prediction of wax precipitation region in wellbore during deep water oil well testing

During deep water oil well testing, the low temperature environment is easy to cause wax precipitation, which affects the normal operation of the test and increases operating costs and risks. Therefore, a numerical method for predicting the wax precipitation region in oil strings was proposed based on the temperature and pressure fields of deep water test string and the wax precipitation calculation model. And the factors affecting the wax precipitation region were analyzed. The results show that: the wax precipitation region decreases with the increase of production rate, and increases with the decrease of geothermal gradient, increase of water depth and drop of water-cut of produced fluid, and increases slightly with the increase of formation pressure. Due to the effect of temperature and pressure fields, wax precipitation region is large in test strings at the beginning of well production. Wax precipitation region gradually increases with the increase of shut-in time. These conclusions can guide wax prevention during the testing of deep water oil well, to ensure the success of the test.

食用蜡基稻米油油凝胶的制备及其性能特性研究

以稻米油为油相,蜂蜡、米糠蜡、巴西棕榈蜡和小烛树蜡作为凝胶剂制备油凝胶,并对其持油率、硬度、流变特性和微观结构进行表征。结果表明:蜂蜡、米糠蜡、巴西棕榈蜡的临界添加量为4%(以凝胶剂和稻米油的总质量为基准,下同),小烛树蜡则为2%,其中蜂蜡的持油效果最佳;随着凝胶剂添加量的增加,油凝胶硬度和黏附性总体上增强。流变学分析显示,所有油凝胶呈现剪切变稀的假塑性行为,弹性模量(G′)大于黏性模量(G″),表明以弹性形变为主。微观结构揭示,不同蜡凝胶剂在6%添加量下形成的油凝胶中存在α、β'和β型晶体。红外光谱分析证实了凝胶剂与稻米油间的非共价相互作用。差示扫描量热分析表明,巴西棕榈蜡油凝胶具有最高的熔化峰值温度。

基于原位微观图像的含蜡原油析蜡胶凝过程

原油的流变性是石油开采、输运过程关注的基础物性,含蜡原油具有复杂的低温流变特性,而蜡的析出是决定原油低温胶凝和复杂流变性的内因。采用可以记录蜡晶微观结构实时演变过程的原位显微观测技术,以大庆原油为考察对象研究了含蜡原油降温析蜡胶凝过程蜡晶微观形貌变化。结果表明:大庆原油在实验温度34~60℃范围内降温过程中,蜡晶数量和面积先缓慢增加后以近似指数形式增加,平均长径比由波动逐渐趋于稳定,分形维数由降温初始阶段波动式增加过渡到后续的线性增加。在降温的开始阶段,降温速率(0.25、0.50、1.00、1.50、2.00℃/min)和加热温度(50、55、57、60、65℃)对蜡晶析出生长过程影响不明显;随着降温的持续,降温速率的减小或加热温度的升高,蜡晶数量和蜡晶面积均大幅增大。蜡晶微观参数在65℃发生突变,这与宏观流变实验的改性加热温度相吻合。含蜡原油降温析蜡胶凝过程的蜡晶生长规律为含蜡原油复杂宏观流变性深入研究及改性输送技术提供理论基础。

木蜡油用透明氧化铁黄色浆制备与应用研究

探讨了分散载体、分散剂对透明氧化铁黄色浆粒径、透明度、存储稳定性、相容性的影响,研究了透明氧化铁黄色浆在木蜡油中的应用性能。结果表明,亚麻油为分散载体,用量为颜料用量的20.0%;D柠檬烯为分散介质;嵌段共聚物TB-3为分散剂,用量为颜料用量的45.0%,60 Hz下研磨60 min,制备颜料含量为30.0%的透明氧化铁黄色浆粒径分布窄、透明度高、存储稳定性好、相容性优异。在木蜡油中添加5.0%透明氧化铁黄色浆时,木蜡油耐老化性能得到明显提升,失光、变色由3级提升至2级,粉化、剥落由1级提升至0级。

Hydrocarbon-Degrading Bacteria and Paraffin from Polluted Seashores 9 Years after the Nakhodka Oil Spill in the Sea of Japan

Pollution of petroleum hydrocarbons, in particular oil spills, has attracted much attention in the past and recent decades. Oil spills influence natural microbial community, and physical and chemical properties of the affected sites. The biodegradation of hydrocarbons by microorganisms is one of the primary ways by which oil spill is eliminated from contaminated sites. One such spill was that of the Russian tanker the Nakhodka that spilled heavy oil into the Sea of Japan on January 2, 1997. The impact of the Nakhodka oil spill resulted in a viscous sticky fluid fouling the shores and affected natural ecosystems. This paper describes the weathering of hydrocarbon-degrading bacteria （genus Pseudomonas） and crystallized organic compounds from the Nakhodka oil spill-polluted seashores after nine years. The Nakhodka oil has hardened and formed crust of crystalline paraffin wax as shown by XRD analysis （0.422, 0.377, and 0.250 nm d-spacing） in association with graphite and calcite after 9 years of bioremediation. Anaerobic reverse side of the oil crust contained numerous coccus typed bacteria associated with halite. The finding of hydrocarbon-degrading bacteria and paraffin wax in the oil crust may have a significant effect on the weathering processes of the Nakhodka oil spill during the 9- year bioremediation.

Physical properties of wax deposits on the walls of crude pipelines

Wax deposits on the wall of a crude oil pipeline are a solid wax network of fine crystals, filled with oil, resin, asphaltene and other impurities. In this paper, a series of experiments on wax deposition in a laboratory flow loop were performed under different conditions （flow rate, temperature differential between crude oil and pipeline wall, and dissolved wax concentration gradient）, and the wax deposits were analyzed, so quantitative relationships among wax content, wax appearance temperature （WAT）, shear stress, and radial concentration gradient of dissolved wax at the solid/liquid interface were obtained. Finally, a model was established to predict WAT and the wax content of the deposit.

Development of a SGJ-1 of Water-Based Anti-Wax Agent

The phenomenon of petroleum wax deposition is very common during oil well production. When the wax molecule condenses on the surface of the pipeline, it will hinder the exploitation of crude oil, reduce the recovery rate of crude oil, and may lead to the blockage of the pipeline when it is serious, so that the oil recovery work will stop. This phenomenon can be obviously changed by using wax cleaning agent. However, the low ignition point and toxicity of oil-based wax remover are not conducive to oil recovery. Therefore, a new water-based paraffin remover SGJ-1 was developed in this paper. The best formula is: wax dispersant 15%, wetting reversion agent 1%, sodium silicate 1%, alcohol cosolvent 8% and 75% water. Condensation point, wax dissolution rate and anti-wax performance of SGJ-1 water-based dewaxing and anti-waxing agent were tested by self-assembly testing device. The experimental results show that the condensation point of SGJ-1 is -34°C, the viscosity reduction effect is good under 35°C, and the wax dissolution rate is 0.0512 g/min, The highest wax prevention rate can reach 89.58% and the wax removal and wax prevention ability is excellent. Compared with other paraffin removers, SGJ-1 can also reduce the viscosity of crude oil, so it has a good development prospect.

Relationship between waxy crude viscosities and wax crystal microstructure

It is important and profound to quantitatively study the relation between rheology and microstructure for development of the microstructural mechanism of crude oil rheology and even for the waxy crude oil pipelining.However,due to the high complexity and irregularity of wax crystal morphology,quantitative characterization is hard to achieve.This has hampered further study on the rheology-microstructure relationship.A new approach combined the fractal geometry and the stereology theory is presented for quantifying the intricate wax crystal morphology and structure.Based on the characterization,the effects of microstructures and oil composition on the waxy crude viscosities are analyzed quantitatively.It further validates the previous qualitative research and enriches understanding into the microstructural mechanism of waxy crude oil rheology.

沥青质对蜡油加氢处理装置运行影响分析

某公司3.2 Mt/a蜡油加氢处理装置催化剂失活速率高达2.16℃/月。经分析发现,原料沥青质含量大幅上涨是导致该装置催化剂快速失活的主要原因。根据沥青质分子模型和催化剂失活原理,对比分析了原料中沥青质质量分数分别在200、500、2800μg/g工况以及氢分压分别在9.0、11.0 MPa下的催化剂失活速率,提出了延长装置运转周期的措施。根据催化剂失活原理,提出对氢分压在中压范围(小于10.5 MPa)的蜡油加氢处理装置,原料沥青质质量分数控制在小于500μg/g,装置运转周期可达到4 a。原料沥青质质量分数降低到300μg/g以下且匹配合适的催化剂级配方案,可达到催化剂表面积炭稳态平衡,实现装置超长周期运行。

扶余油田外围区块生物胶降黏压裂技术试验

扶余油田外围区块原油密度大、黏度高、凝固点高、含蜡量高,采用常规胍胶携砂压裂技术无法有效开采,压裂投产后初期产量较低,达不到效益产能,外围区块基本处于未开发动用状态。为此,研发了生物胶降黏剂体系与压裂工程技术相配套的降黏压裂技术,并进行了实验评价。评价结果显示,该生物胶具有降凝、降黏、防蜡、乳化、驱油等性能,可显著提高原油流动性。现场试验分为生物胶降黏加砂压裂和生物胶降黏不加砂压裂两种技术方式,共在扶余外围及稠油区块累计实施45口井。前置液胍胶造主裂缝+支撑剂+生物胶降黏剂+支撑剂+后置液降黏剂的技术方法应用在新投产的外围及稠油区块,对比老区内部,在储层物性变差的条件下,投产后产油量超设计产能1.6倍,是老区内部的1.4倍。生物胶降黏不加砂压裂技术主要应用在老井二次压裂或多轮次压裂稠油区块或黏度上升井层,同等条件下对比,黏度由压裂前的70mPa·s下降到25mPa·s,增产量是同区块常规压裂的1.3倍。

金龙2井区含蜡原油结蜡微观机理及预测模型

采用分子动力学方法研究了含蜡原油结蜡的微观机理,通过实例优选了结蜡预测模型,根据含水率对结蜡量的影响对预测模型进行修正,并提出考虑原有结蜡厚度对后续结蜡影响的计算流程。实验结果表明,初始蜡分子先在原油中分散,后在非晶细胞盒子中聚集形成蜡晶,随着温度升高径向分布函数峰值降低,蜡分子分布从紧密聚集向分散转变;修正后的结蜡预测模型计算误差仅为4%,随着含水率的增高结蜡厚度减小,随生产时间的延长结蜡厚度增加缓慢。修正后的结蜡预测模型能准确预测金龙2井区清蜡周期,可为现场清防蜡工艺提供理论指导。

PHT-01/PHC-05组合催化剂在加氢裂化装置的工业应用

在中国石油辽阳石化公司110万t/a加氢裂化装置中,以俄罗斯原油的二次油(减压蜡油和催化柴油的混合油,二者质量比10∶1)为原料,采用中国石油自主开发的PHT-01加氢精制催化剂、PHC-05加氢裂化催化剂及PHT系列加氢保护剂,为最大限度生产重石脑油进行了工业应用,考察了催化剂应用情况、产品性质及其分布。结果表明:催化剂运行中,可同时进行湿法硫化与钝化操作,精制反应器、裂化反应器的平均反应温度分别为367,363℃,比设计值分别低5,15℃,温升比设计值分别低3,4℃;目标产品重石脑油的含硫(氮)量均小于0.5μg/g、溴指数0.755 mg/g、芳潜质量分数47.3%、初馏点73℃、收率51.56%,精制油含氮量为7~9μg/g,主要产品收率为94.04%,满足下游重整装置进料要求。

B301试验区油井结蜡主控因素及对策

B301试验区位于H盆地,该试验区目前油井结蜡现象严重,防蜡效果较差,防蜡措施有效期较短,无法满足油井防蜡的需要,亟需找到影响油井结蜡的主控因素。针对上述问题,通过室内实验对产出液中的蜡质、胶质、沥青质和机械杂质含量进行测定。利用Olga数值模拟软件对温度、压力、流速进行模拟。研究表明:蜡质、沥青质、机械杂质含量以及温度、流速为影响B301试验区油井井筒结蜡的主控因素,影响程度强弱依次为蜡质、温度、沥青质、机械杂质、流速。研究成果可为B301试验区进一步高效开发提供理论与技术基础,为高含蜡油藏防蜡方法提供参考。

JH油田含蜡原油析蜡温度测试与分析

采用显微镜观察法、黏温曲线法、DSC法分别测试了JH油田六个不同区块的原油析蜡温度。在DSC法中,测定了降温速率5、10℃/min下的析蜡点。在黏温曲线法中,测定了剪切速率10、20、50、100 s^(-1)下的析蜡点。在显微镜观察法中,测定了降温速率0.5、5℃/min下的析蜡点。实验结果表明,不同方法测量的析蜡点有所差异,一方面与不同测试方法的原理有关,另一方面与仪器的分辨率、操作者的经验有关。若原油中的活性物质和大分子不溶物影响较大时,也会表现不同。