CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

ABSTRACT

Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are concerned. Residual oil left in the limestone pack on the other hand shows an increase in the low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) activation energies as determined from TGA combustion experiments on the samples taken from the pack after steam injection experiments.     

GAS EVOLUTION AND CHANGE OF OIL COMPOSITION DURING STEAM FLOODING OF OIL RESERVOIRS

The injection of steam into oil reservoirs is a technique commonly used for improving the production of heavy crude oils. Very often, a change in the composition of the oil and gas produced may be observed during steam flooding. In general, corrosive gases, such as H₂S and CO₂, are produced in increased quantities.
In laboratory experiments on sulphur-bearing reservoir minerals and crude oils the origin of the change in oil and gas composition was investigated. Temperatures up to 370°C were applied to study temperature- and rate-dependent phenomena. By means of X-ray fluorescence, gas chromatography and chemical precipitation methods, the change in the sulphur material balance was studied.
It was shown that gas evolution depends strongly on the temperature of the steam injected. Furthermore, it was possible to prove that the gases evolved during steam flooding (such as CO₂, H₂S etc.) originate from the decomposition of crude oil components. Besides these investigations, a drastic viscosity increase of the residual crude oil was observed after steam injection was applied.
It is concluded that the production of H₂S and CO₂ may be controlled by temperature adjustment of the steam being injected.     

Calorimetric study approach for crude oil combustion in the presence of clay as catalyst

In this research, the effect of heating rate and different clay concentrations on light and heavy crude oils in limestone matrix was investigated by differential scanning calorimeter (DSC). In DSC experiments, two main distinct reaction regions were identified in all of the crude oil + limestone matrix + catalyst, known as low- and high-temperature oxidation respectively. It was observed that addition of clay to porous matrix significantly affected the thermal characteristics and kinetics of different origin crude oils. The Borchardt and Daniels and ASTM kinetic methods were used to determine the kinetic parameters of the samples. It was observed that activation energies generated for the high-temperature oxidation region for crude oil and crude oil + clay mixtures were in the range of 148–370 kJmol^?1 for the Borchardt and Daniels method and 51–253 kJmol^?1 for ASTM methods.     

AN EXPERIMENTAL APPROACH OF ELEMENTAL SULFUR DEPOSITION IN CARBONATE OIL RESERVOIRS

The existence of sulfur compounds in crude oils creates many problems of sulfur deposition in the vicinity of the wellbore hole, in well completion and/or production equipment, and in producing reservoir rocks. The major objectives of this experimental study are to investigate the influences of oil flow rate, initial sulfur concentration of crude oil, and reservoir rock permeability on elemental sulfur plugging in carbonate oil reservoirs. To achieve these objectives, actual crude oils were de-asphaltened to eliminate the effect of asphaltene deposition. Ten dynamic flow experiments were conducted using two actual crude oils of 0.78 and 1.67% sulfur concentrations. Viscosity of crude oils of different sulfur concentrations was measured under different conditions of temperature. The crude oils were flooded through actual carbonate cores of different permeability in the range of 2.34-28.16 millidarcy and under different flow rates of 0.5, 1.0, 1.5, and 2.0 cc/min. In-situ sulfur deposited was measured using Scanning Electron Microscopy (SEM) to provide the amount of sulfur deposited along the core samples. The results indicated that crude oil of higher sulfur concentration has higher viscosity than that of one of lower concentration. The deposition of elemental sulfur does not take place at the low rate of 0.50 cc/min, starts at 1.0 cc/min and increases as the flow rate increases up to 1.50 and 2.00 cc/min, respectively. In addition, the higher sulfur concentration of the crude oil increases the deposition of sulfur in carbonate oil reservoirs. The results also showed that permeability of carbonate reservoir rocks has a severe effect on sulfur deposition since carbonate rocks of higher permeability do not experience the problem of elemental sulfur deposition while the problem is more severe for lower permeability rocks. In addition, the depositional rate is accelerated rapidly as the rock permeability decreases. The obtained results of this study have important interest in identification of the most important factors affecting the elemental sulfur precipitation in heterogeneous carbonate oil reservoirs and robust implications in the development of reservoir simulation models.     

水力喷射泵用于稠油热采的几个问题

用水力喷射泵开采含砂稠油，由于泵结构简单、且无运动件，解决了泵的砂卡问题。在设计喷射泵时，考虑了两个问题：一是原油粘度随油层温度的下降而增加，泵效又随原油粘度的增加而降低，为此对注蒸汽后油层温度的变化作了定性分析后，给出了可供拟合油层温度随时间变化关系曲线的温度－时间关系式。二是为方便注蒸汽，设计了一种特殊结构的底阀，可不起出底阀直接由抽转注。     

电气绝缘油热膨胀系数的研究

在实验室采用ASTM D1903方法对油源不同、牌号不同的绝缘油进行热膨胀系数的研究,结果表明：大多数矿物绝缘油的热膨胀系数在0.000 72～0.000 80之间,且随着温度升高,呈略增大趋势;对于同一油源且黏度相差较大的绝缘油,黏度高的油样热膨胀系数小,黏度低的油样热膨胀系数大;对于同一黏度级别的绝缘油,环烷基油热膨胀系数最小,中间基油次之,石蜡基油热膨胀系数最大;对于基属相同的绝缘油,随芳烃含量增大,热膨胀系数减小。     

Effect of oil-solubility catalysts on the low-temperature oxidation of heavy crude oil

Due to low oil recovery factor in heavy oil reservoir, air injection with catalyst becomes a competitive technology to effectively reduce viscosity of crude oil as a result of the low cost and small environment pollution. This paper determined the feasibility of air injection with catalyst in a heavy oil reservoir through static and dynamic experiments. The results indicated that under the effect of catalyst, oxidation between heavy oil and air could significantly reduce the viscosity of crude oil. The optimal catalyst contained 0.7?wt. % oil-solubility organic acid copper and 0.5?wt. % sodium hydroxide. With the oxidation time increasing, viscosity of crude oil decreased and oil recovery factor increased. With temperature increasing, viscosity of crude oil decreased sharply and oil recovery factor increased. The oil recovery factor of air huff-n-puff process was 30.2%. Air injection with catalyst in the reservoir is a promising technology.     

多孔介质中原油蒸汽蒸馏实验研究

方法　利用注蒸汽蒸馏模拟装置研究了原油在多孔介质中的蒸汽蒸馏率。目的　研究原油在多孔介质中的蒸馏机理及其主要影响因素。结果　原油在多孔介质中的蒸汽蒸馏率与原始油量 (含油饱和度 )、注汽速度等无关 ;饱和条件下 ,提高蒸汽温度 ,原油的蒸馏率提高的有限 ;过热蒸汽能大幅度提高原油的蒸馏率 ,对于重质原油该现象尤为显著。结论　原油的蒸汽蒸馏率主要取决于原油自身的性质 ,与多孔介质、原始油量 (含油饱和度 )及注汽速度等无关 ;而温度和压力是影响原油蒸汽蒸馏率的关键因素。     

溶剂辅助SAGD开采油砂快速启动技术

双水平井SAGD技术是油砂开采的主要方式。针对SAGD预热启动时间长的问题,采用蒸汽循环前注入溶剂方式,缩短预热时间,提高蒸汽利用效率。对溶剂与原油混合后降黏效率进行了测试;采用一维填砂模型,开展溶剂注入性能研究;采用三维物理模型,开展不同预热启动方式实验研究,分析SAGD不同启动方式的温度场、压力场随时间的变化规律。并以加拿大油砂为目标进行了SAGD启动方式及工艺参数优化。结果表明,溶剂可以大幅度降低原油黏度,前置注入溶剂可提高蒸汽注入能力,蒸汽-溶剂复合循环启动时间沿程平均降低幅度达15%,蒸汽注入量可减少21.4%。通过油藏数值模拟方法对比得出,加入溶剂井间达到80 ℃需要90 d,时间减少50%。因此,采用蒸汽-溶剂复合循环启动技术,可以有效提高加拿大油砂开采启动效率,并大幅度降低成本。     

A study of the catalytic steam cracking of heavy crude oil in the presence of a dispersed molybdenum-containing catalyst

The features of the steam cracking of heavy crude oil in the presence of a dispersed molybdenumcontaining catalyst are studied. The effect of water, the catalyst, and process conditions on the composition and properties of the products of the thermal conversion of heavy crude oil is determined in experiments on thermal cracking, steam cracking, catalytic cracking in the absence of water, and hydrocracking. A complex analysis of the resulting products is conducted; the catalyst-containing solid residue (coke) has been studied by XRD and HRTEM. The effect of the process temperature (425 and 450°C) and time on the yields and properties of the resulting products is studied. The efficiencies of hydrocracking and steam cracking for the production of upgraded low-viscosity semisynthetic oil are compared; the fundamental changes that occur in the catalyst during the studied processes are discussed. Some assumptions about the principle of the catalytic action of the molybdenum-containing catalyst in the steam cracking process are made.     

地下水热催化裂化降粘开采稠油新技术研究

针对辽河油田的3种稠油,筛选陋一种合适的水热裂解催化剂（过渡金属盐）,确定了水热裂解的最佳条件,在0．2％该催化剂顾在下,3种稠油样在240℃经水热裂解反应24h后,50℃粘度分别下降89．9％－77．7％,饱和烃和芳香烃含量大幅上升,胶质,沥青质含量下降,烃碳数分布移向低碳数方向,产生大量气体和少量固体,在辽河油田曙光采油3口蒸汽吞吐井进行的地下稠油催化剂水热裂解降粘开采现场试验获得成功,采出的稠油粘度大同度降低。     

原油及源内残余沥青裂解成气差异及地质意义

为了研究不同类型原油和源内残余沥青在高演化阶段的甲烷产率,明确天然气成因类型,系统整理了不同类型原油及源岩的金管模拟实验结果,统计了甲烷产率随模拟温度的变化,发现原油性质对生气过程和生气量都有明显控制,重质油起始生气温度低于轻质油和正常油,在原油裂解成气初期,甲烷产率变化为重质油>正常原油>轻质油,重质油对天然气成藏贡献较大;在原油大量裂解过程中,轻质油的甲烷产率很快超过正常原油和重质油,最终成为天然气成藏的主力。重质油产气早是因为其富含非烃和沥青质,裂解活化能低,产气率低与H/C值（原子比）低有关,轻质油产气晚是因为其富含饱和烃,裂解活化能高,产气率高与H/C值（原子比）高有关。轻质油开始裂解对应成熟度约为Easy% R_O=1.5%。干酪根及源内分散沥青生气与原油裂解受相同的因素控制,H/C值高低控制了不同类型干酪根的生气量,在各成熟阶段上甲烷产率始终是Ⅰ>Ⅱ>Ⅲ型有机质。源内分散沥青在化学组成上接近重质油,但比重质油更容易裂解,除活化能低外,还受到黏土矿物催化的影响,其起始裂解成熟度大体为Easy% R_O=1.0%。这种差异对热演化程度极高的四川盆地天然气成因类型确定和潜力评价有非常重要的地质意义。     

The influence factors analysis of the light crude oil oxidation reaction process

During the high pressure air injection process, there are different types of oxidation reactions, which do not exist, and the predominant reaction type of is dependent on the specific conditions. In this study the influences of formation temperature, pressure, and oxidation time on light crude oxidation have been studied via oxidation experiments. And it is shown that the reaction types could be effectively improved by the temperature increment, which decreases the oil viscosity. As well, the pressure and oxidation time have obvious effects that were mainly present in oxygen addition reactions and the viscosity increase.     

浅谈我国裂解制乙烯的原料

基于我国原油中轻质馏分油少的特点，我国乙烯生产必须使用多种原料。从组分的碳氢结构及大量裂解中试数据出发研究我国研究不同的轻质馏分油，中质馏分油和重质馏分油的裂解和结焦性能。这些研究表明，不管何种馏分在生产乙烯过程中碳氢结构组成是非常重要的。因此通过加氢必质来改善劣质原料的碳氢结构是必需的。     

春风油田排601块水平井蒸汽驱井网类型优化物理模拟实验

蒸汽驱是稠油油藏水平井蒸汽吞吐进入开发后期主要的接替技术，而水平井的井网形式影响着蒸汽驱的开发效果。以春风油田排601块浅薄层稠油油藏为研究对象，依据相似准则，建立了高温高压三维比例物理模型，并开展了排状井网、五点井网、反九点井网条件下蒸汽驱物理模拟实验。研究结果表明:蒸汽驱过程中温度场的发育主要受注入井与生产井间的驱替压差的控制，注入蒸汽主要流向流动阻力小的区域（临近井、高渗条带、高温低黏油带）；蒸汽突破初期，依然有大量的原油从模型产出；实验结束后，蒸汽未波及区域存在大量剩余油。在排601块油藏条件下，排状井网、五点井网和反九点井网蒸汽驱的最终采收率分别为45.10%、41.90%和38.30%；排状井网、五点井网和反九点井网最大累积油汽比分别为0.69、0.63和0.53，综合对比排状井网效果最优。蒸汽驱过程的主要作用机理和现象包括:高温降黏作用、高温体积膨胀、高温蒸汽蒸馏和原油裂解作用、高波及效率和蒸汽超覆。研究结果可以有效支撑春风油田排601块水平井蒸汽驱设计。     

Molecular composition of in-situ combustion and steam assisted gravity drainage crude oils

This study investigated the property and composition of crude oils from in-situ combustion (ISC) and steam assisted gravity drainage (SAGD). We made comparison of the elemental composition and molecular weight distribution of the two crude oils. It was overserved that ISC crude oil has significant higher oxygen content. The ultra-high resolution mass spectrometry was applied to investigate the molecular composition of acidic compounds in two crude oils. The acidic compounds in ISC crude oil have higher carbon numbers than that of SAGD crude oils.     

In situ catalytic upgrading of heavy crude oil through low-temperature oxidation

The low-temperature catalytic oxidation of heavy crude oil (Xinjiang Oilfield, China) was studied using three types of catalysts including oil-soluble, watersoluble, and dispersed catalysts. According to primary screening, oil-soluble catalysts, copper naphthenate and manganese naphthenate, are more attractive, and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil. The heavy oil compositions and molecular structures were characterized by column chromatography, elemental analysis, and Fourier transform infrared spectrometry before and after reaction. An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity– temperature characteristics. Results show that the two oil-soluble catalysts can crack part of heavy components into light components, decrease the heteroatom content, and achieve the transition of reaction mode from oxygen addition to bond scission. The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil (oil viscosity and contents of heavy fractions). It is found that the temperature, oil composition, and internal molecular structures are the main factors affecting its flow ability. Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.     

改善中等粘度指数基础油质量的几种方法

针对中间基原油的特点,从油品的结构和组成论述了润滑油的粘度指数、氧化安定性与组成的关系以及采用调合、脱氮、缓和加氢处理工艺来改善中等粘度指数基础油质量的几种方法。其中润滑油缓和加氢处理工艺既能适当提高油品的粘度指数,又能改善其氧化安定性。