高压注气条件下沥青质沉淀的实验研究

引　言注ＣＯ2 三次采油技术的实施容易引发原油中沥青质沉淀 ,并使岩芯渗透率降低、润湿性反转 ,甚至造成永久性油藏损害[1] .此外 ,还会导致设备的堵塞 ,使生产效率严重降低 .为了配合我国注ＣＯ2 三采技术的实施 ,本文首次测定了国产原油 (草桥原油 )注气过程中沥青质的沉淀量 .现有描述沥青质沉淀的理论模型都涉及沥青质物性数据 ,且待定参数多、预测性较差[2 ] .标度方程[3] 不涉及此物性数据 ,且待定参数少 ,预测性较高 ,但迄今仍限于常压正构烷烃 /原油体系 .因此 ,本文将其拓展应用至高压注气体系 ,并与本文及文献数据进行了比较 .1…     

注气过程中沥青质沉淀对孔隙型碳酸岩油藏储层伤害的实验研究

中东地区大部分油藏属于孔隙型碳酸岩油藏,开发初期采用衰竭开采,中后期二次采油基本采用注气方式。而无论是衰竭开采还是注气提高采收率,沥青在地层和井筒沉淀都是一个普遍现象。它是制约原油生产的一个重要因素,本次重点研究了实验模拟条件下注气过程中沥青沉淀对储层的伤害程度。这对于中后期注气开发过程中控制沥青沉淀,提高原油采收率有重要的意义。实验表明:沥青沉淀会对储层的孔隙度和渗透率造成伤害,不同的注入速度对储层的伤害程度不同,注入速度较高时,沥青沉淀对储层的伤害更严重;气驱后注入气体突破对储层的伤害进一步加剧。因此在对油藏特别是孔隙型低渗透碳酸岩油藏实施注气时,尽量延长气体突破的时间,同时针对沥青沉淀需采取一定的预防措施。     

影响煤焦油沥青质测定量的工艺参数

煤焦油通过溶剂分析可定量分离为三部分：甲苯不溶物、沥青质和油相。本文主要研究了煤焦油在此分离过程中芳烃溶剂类型、萃取方法、甲苯溶液浓缩量、烷烃溶剂类型和正庚烷溶剂与甲苯溶液浓缩量的添加比例对煤焦油沥青质沉淀量的影响。结果表明,甲苯溶液浓缩量、正庚烷与甲苯溶液浓缩量的添加比例对沥青质沉淀量的影响较大,萃取方法次之,将苯替换成甲苯影响最小。当选择甲苯溶解煤焦油,超声萃取3h,甲苯溶液浓缩量9mL,正庚烷与甲苯溶液浓缩液的添加比例为20∶1时,煤焦油沥青质的沉淀量为13.4%。本实验表明煤焦油的分离工艺会影响沥青质沉淀量,故在研究煤焦油沥青质性质和结构时需注明沥青质的沉淀分离条件。     

不同原油界面活性组分的分离及表征

用极性分离法将胜利油田孤东1#、孤东4#原油和大庆原油分离为饱和分、芳香分、胶质、沥青质组分(S、Ar、R、As)。孤东1#和孤东4#沥青质组分质量分数(14.43%、11.35%)明显高于大庆原油沥青质组分质量分数(0.09%),而饱和分组分质量分数(47.08%、46.54%)低于大庆原油饱和分质量分数(68.08%)。孤东1#和孤东4#原油的原油组分(S、Ar、R、As)氧的质量分数、酸值由大到小的排序为:沥青质>胶质Ⅰ>芳香分>饱和分。而大庆原油的原油组分酸值由大到小的排序为:胶质Ⅰ>沥青质>芳香分>饱和分;大庆原油的饱和分组分中氧质量分数较低,饱和分中氧质量分数在原油氧中所占比例最高(0.375%),饱和分中的氧化物对大庆原油的界面活性影响不可忽视。在3种原油所有原油组分中,孤东1#原油沥青质的酸值最大(16.45 mg KOH/g沥青质),说明孤东1#原油沥青质组分含有较多酸性基团,反应活性较强。色-质分析结果表明,孤东原油饱和分正构烷烃在C10-C37呈双正态分布,大庆原油饱和分正构烷烃主要分布在C10-C38,基本呈正态分布。     

BA原油沥青质性质及沉积抑制剂作用机理

原油开发中出现沥青质沉积问题，会导致油井及集输管线堵塞，从而影响原油正常生产和油田的高效开发。本文通过对BA原油中沥青质进行元素、XPS和FTIR分析，可知该沥青质表面官能团以碳氢化合物（C-C，C-H）为主，还含有硫酚和硫醇等脂肪类硫以及羧基等酸性官能团，可为沥青质沉积抑制剂的选择提供理论依据。抑制剂是通过破坏沥青质缔合体的相互作用来达到抑制聚沉的作用，利用激光粒度仪对原油加正庚烷（沉淀剂）后沥青质颗粒的粒度分布进行测定，结果表明：在油样中加入含有胺基碱性基团的抑制剂FAE183，能抑制沥青质的絮凝与沉淀，使沥青质颗粒的粒径显著减小。由抑制剂的作用机理分析可知，FAE183抑制剂与沥青质的主要作用机理为酸碱作用，并辅以氢键作用和偶极作用。     

F油田降压开采过程中沥青质沉淀规律

沥青沉降是影响原油生产的一个重要因素,针对其沉淀机理和规律进行分析研究对于控制沥青沉淀,提高原油采收率有重要的意义.研究了依靠自然能量开采的F油田原油的沥青沉淀析出规律和沥青沉淀量变化规律.沥青沉淀析出实验研究表明随着压力的降低,沥青沉淀现象的发生对应有一个临界压力(AOP).当压力低于AOP高于泡点压力时,沥青沉淀随压力降低而增加,当压力高于AOP时不会发生沥青沉淀;不同温度也会对沥青的沉淀造成影响,与储层相比井筒靠近井口附近发生沥青沉淀的概率更高;沥青的沉淀量实验研究表明,沉淀量随压力先降低后增加,在近似饱和压力处沉淀量最大.     

易沉积重油储层沥青质沉积特征及防治技术研究

M油田为碳酸盐岩储层,原油相对密度为0.9487,比重指数为17.65,属于重质原油.原油中沥青质质量分数为17.7％,高含量的沥青质在生产过程中易在井筒内沉积,导致井筒、电潜泵堵塞等问题,严重影响了该油田的正常生产.通过对原油特征、沥青质特征实验,得到了原油具体组成和胶体不稳定指数等原油特征,并得到了沥青质沉积物组成及具体结构特点、絮凝初始点、沉淀量等关键参数.在对原油和沥青质实验分析的基础之上,开展了沥青质沉积抑制剂、解除剂的筛选和优化实验,得到了适用于该油田的阳离子型沥青质沉积抑制剂和水基乳化低毒性沥青质解除剂体系.     

巴什托油田沥青质沉淀清除方法探讨——以BK7、BK9井为例

结合沥青质沉淀机理相关材料,对沥青质的物理化学沉积机理、沥青质堵塞储层孔喉的机理进行了总结,通过分析原油中沥青质发生絮凝的温度、压力、组分,找出该油田发生沥青质沉积的主要影响因素,从而搞清沥青质对储层渗透率的影响,总结历年巴什托油田解堵实验成果,为巴什托油田后期综合治理提供依据,对防止储层损害,确保稳产、高产具有重要意义。     

塔河油田托甫台区块油井沥青质堵塞综合研究

目前塔河油田托甫台区块油井沥青质堵塞问题渐显突出,解堵难度大,成本高,严重影响产量;通过对该区块油井TP17CX沥青质堵塞基本情况及堵塞物成份实验分析,结果表明该井堵塞物60%左右为胶质及沥青质;基于沥青质产生基本原因及前人研究成果,确立了一种对沥青质初始沉淀压力及温度预测的计算方法,并结合生产实践,得出TP17CX井的初始沉淀压力及温度分别为44MPa、125℃,为塔河油田沥青质沉淀预防和解堵提供依据,促进了该区油井高产、稳产高效开发。     

石油沥青质的化学结构研究进展

本文概述了石油沥青质的化学结构的理论研究成果,描述了原油胶体体系模型及化学结构模型。通过1H和13C核磁共振(NMR)的测定,计算沥青质的平均分子式和结构参数,并推测出分子模型。沥青质的基本结构单元均可以用稠环芳烃连接环烷烃和烷基侧链,并含杂原子的单元来表示。这有助于从分子水平认识沥青质,对于解决在原油开采与加工中吸附、沉淀等问题具有重要的理论意义。     

Asphaltene precipitation and deposition in oil reservoirs – Technical aspects,experimental and hybrid neural network predictive tools

Precipitation of asphaltene is considered as an undesired process during oil production via natural depletion and gas injection as it blocks the pore space and reduces the oil flow rate. In addition, it lessens the efficiency of the gas injection into oil reservoirs. This paper presents static and dynamic experiments conducted to investigate the effects of temperature, pressure, pressure drop, dilution ratio, and mixture compositions on asphaltene precipitation and deposition. Important technical aspects of asphaltene precipitation such as equation of state, analysis tools, and predictive methods are also discussed. Different methodologies to analyze asphaltene precipitation are reviewed, as well. Artificial neural networks (ANNs) joined with imperialist competitive algorithm (ICA) and particle swarm optimization (PSO) are employed to approximate asphaltene precipitation and deposition with and without CO₂ injection. The connectionist model is built based on experimental data covering wide ranges of process and thermodynamic conditions. A good match was obtained between the real data and the model predictions. Temperature and pressure drop have the highest influence on asphaltene deposition during dynamic tests. ICA-ANN attains more reliable outputs compared with PSO-ANN, the conventional ANN, and scaling models. In addition, high pressure microscopy (HPM) technique leads to more accurate results compared with quantitative methods when studying asphaltene precipitation.     

Aggregation thermodynamics for asphaltene precipitation

Asphaltene precipitation has been a major concern for petroleum industry due to its adverse effect on upstream production, midstream transportation, and downstream refining. As a complex phenomenon involving solubility, aggregation, and clustering, asphaltene precipitation has been extensively investigated and correlated with empirical models and equations. Based on the insight regarding hierarchical structure of asphaltenes recently elucidated by Mullins, we present a thermodynamic formulation for asphaltene aggregation, the onset of asphaltene precipitation. The thermodynamic formulation accounts for asphaltene aggregation driving force as a two‐step process: (1) molecular asphaltene forming imaginary “nanocrystals”, and (2) “nanocrystals” re‐dissolving as colloidal nanoaggregates. Applying UNIFAC with this thermodynamic formulation, we show semi‐quantitative predictions of asphaltene precipitation in 13 binary solvents with wide varieties of chemical structures and solvent combinations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1254–1264, 2016     

二氧化碳驱油藏沥青质沉淀量测量装置的实验研究

设计了一套二氧化碳驱油藏沥青质沉淀量测量装置,该装置采用全密闭流程,借助计算机实现控制并做数据采集,对产出的气体进行同步气相色谱分析。使用该装置对某油田的二氧化碳驱进行实验分析,最终得出了地层温度、驱替压力对二氧化碳驱沥青质沉淀的影响关系。     

A Novel Photometric Technique to Detect the Onset of Asphaltene Precipitation at Low Concentrations: The Effect of Maltenes and Water

A photometer was utilized to measure the intensity of scattered light in toluene / heptane / asphaltenes mixtures. On the scattering‐intensity versus heptane‐to‐toluene ratio functions, two linear regions can be observed. The intersection of these regions determines the heptane‐to‐toluene ratio at which the precipitation of asphaltenes starts. The onset of asphaltene precipitation was determined as a function of asphaltene concentration in the presence and in the absence of maltenes as well as water. The onset is dependent on the asphaltene concentration. The presence of water promoted while the presence of maltenes inhibited the precipitation of asphaltenes.     

Application of Chebyshev polynomials to predict phase behavior of fluids containing asphaltene and associating components using SAFT equation of state

In this work, a thermodynamic model based on statistical association fluid theory (SAFT) is developed to predict the phase behavior of mixtures containing asphaltene contents. The SAFT equation of state is a good candidate for closing that gap between statistical mechanic models and the classical models dominated by cubic equation of state. A robust, fast and accurate computational algorithm based on Chebyshev polynomial approximation is developed to calculate the density and hence fugacity using SAFT equation of state in order to perform phase equilibrium calculations. Application of Chebyshev polynomials to approximate pressure-density function leads to an interpolation error of degree 10⁻¹³. Application of the proposed algorithm to calculate density of binary systems composed of ethanol and toluene shows an average relative deviation of 0.143% in the temperature range 283.15-353.15 K and for pressures up to 45 MPa. The proposed model is developed to predict the precipitation behavior of petroleum fluids containing asphaltene. The effect of pressure, temperature and solvent concentration on the amount of asphaltene precipitation is investigated. A good agreement with an AAD of 2.593% is observed between experimental and predicted amount of asphaltene precipitate. The model is also tested to investigate the effect of temperature and solvent concentration on asphaltene onset pressures (upper and lower). Again, an excellent agreement is observed between experimental and predicted values of the asphaltene onset pressure at different temperatures and solvent concentrations with an average 0.705% relative error. The accuracy of the proposed model is compared with WinProp software using Peng-Robinson equation of state with average 53.132% and 8.657% relative errors for the amount of asphaltene precipitate and onset pressure, respectively.     

Modeling of asphaltene and water associations in petroleum reservoir fluids using cubic‐plus‐association EOS

Asphaltene is a group of complex compounds commonly present in petroleum reservoir fluids. It is conceivable that asphaltenes strongly interact with water through hydrogen bonding, affecting phase behavior of water/oil mixtures with/without forming an asphaltene‐rich phase. In this research, the cubic‐plus‐association equation of state (CPA EOS) is applied to multiphase behavior resulting from self‐ and cross‐associations of asphaltenes and water in petroleum fluids. This article also presents a new correlation for binary interaction parameters for water with n‐alkanes for the CPA EOS by using three‐phase data for water/n‐alkane binaries. A method is proposed to characterize mixtures of asphaltene‐containing oil with water using the CPA EOS. Results show that the CPA EOS can represent multiphase behavior for water/oil mixtures with up to four equilibrium phases: asphaltene‐rich, solvent‐rich, aqueous, and vapor phases. Case studies include bitumen/water mixtures, involving asphaltene‐water emulsion, water solution in bitumen, and their continuous transition with varying temperature. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3429–3442, 2018     

Inhibition effect of CO2 on asphaltene precipitation for an Iranian crude oil and comparison with N2 and CH4

The effects of N₂, CH₄ and CO₂ injection on asphaltene precipitation have been experimentally investigated using a reservoir oil fluid from south of Iran, making use of light transmission method. The results are compared and the effects of injected gases on reducing asphaltene colloidal stability in oil are found in the following order: CH₄> N₂>CO₂. It is observed that CO₂ can act like an inhibitor and can increase the solubility of asphaltene, decreasing the asphaltene precipitation onset. A thermodynamic discussion explains the effect of CO₂ on the solubility of asphaltene based on the solubility parameters of recombined oil and CO₂, calculated from Peng-Robinson equation of state along with an empirical correlation for volumetric properties of CO₂.