含蜡原油石蜡沉积模拟方法研究

对从苏丹Unity油田现场取得有代表性的原油样品进行了原油组分分析和析蜡点测试。并针对油田的生产状况,利用与美国德士古石油公司合作建立的自动化高压石蜡沉积循环管道模拟系统,采用冷却实验步骤测试了苏丹原油从高于原油析蜡点温度到较低环境温度范围内在现场流速、油温和环境温度下的石蜡沉积速率,定量研究了流速和油温对石蜡沉积速率的影响,并采用分子扩散和剪切效应的总效应来描述石蜡沉积机理。利用临界蜡张力作为模拟放大因子,采用半经验的石蜡沉积数学模型,预测了Unity油田21井的生产井筒在现场生产条件下的石蜡沉积情况,模拟了不同产量和不同时间的蜡沉积剖面。结果表明,该油井在目前高产条件下,未发生石蜡沉积问题;在低产时,须考虑清蜡和防蜡措施。     

热处理对添加防蜡剂长庆原油流动性及蜡沉积特性的影响研究

基于流变性测试和蜡沉积实验研究了热处理温度对添加EVA/PAMSQ复合防蜡剂的长庆原油的流动性和蜡沉积特性的影响。研究发现加剂原油依然具有热处理效果,50℃热处理条件下加剂原油的流动性改进效果较差,随着热处理温度升高至60、70和80℃,加剂原油的流动特性(如凝点、黏度、小振幅振荡剪切特性)显著改善。80℃热处理条件下,加剂原油的凝点已低于0℃,表明热处理与EVA/PAMSQ复合防蜡剂具有良好的协同效果。同时,随着热处理温度的升高,加剂原油的蜡沉积速率逐渐降低,但蜡沉积物的含蜡量逐渐升高,这可能不利于蜡沉积物的剥离。蜡沉积物呈现出非均质结构,表层蜡沉积物为凝油状,底层蜡沉积物具有比表层蜡沉积物更高的析蜡点和屈服强度。     

大庆原油蜡沉积规律研究

在理论分析及室内试验的基础上,系统研究了油温、流速、管壁处温度梯度等参数对大庆原油蜡沉积的影响.在原油与管壁温差相同时,不同温度段蜡沉积速率并不相同,存在蜡沉积高峰区.在壁温相同时,随油温升高,蜡沉积速率逐渐增加.在油温、壁温相同的条件下,随流速增加,蜡沉积速率下降.建立了大庆原油蜡沉积模型,并利用该模型预测了铁岭-秦皇岛输油管线不同季节、不同时间沿线蜡沉积分布.铁-秦线冬季存在蜡沉积高峰区;春、秋季出站时蜡沉积最严重,下一站进站时蜡沉积最轻;夏季蜡沉积速率更小,且沿线变化不大.     

热处理温度对长庆原油蜡沉积特性的影响

通过Couette蜡沉积装置及DSC热分析探究了热处理温度对长庆原油蜡沉积特性的影响,发现随着热处理温度的升高,长庆原油蜡沉积速率减缓,蜡沉积层老化速率加快;经50 ℃和60 ℃热处理的长庆原油,蜡沉积层出现了分层现象,其表层为流动性较强的凝油状蜡沉积层,底层为结构较为致密的类固态蜡沉积层;经70 ℃热处理的长庆原油,蜡沉积层极薄且致密,无分层现象,其表面无凝油状蜡沉积层。采用沥青质分散程度分析、DSC热分析及蜡晶形貌显微观察探究了其影响机理,发现随着热处理温度的升高,长庆原油沥青质分散程度增大,从而使其析蜡点降低,蜡晶团聚性增强,原油低温流动性得以改善,进而对其蜡沉积特性产生了显著影响。     

Prediction of Wax Deposition in an Insulation Crude Oil Pipeline

This study establishes an insulation crude oil pipeline wax deposition experimental device and describes the experimental method for insulation crude oil pipeline wax deposition. The experimental program is based on the operational plan of Tieling–Huludao insulation crude oil pipeline. The data are analyzed according to the effect of varying oil temperature, insulation thickness, and flow on wax deposition. Using SPSS software, a Daqing crude oil wax deposition rate model is derived from the linear regression. The use of the wax deposition rate model forecasts the wax deposition of the Tieling–Huludao insulation crude oil pipeline during different seasons.     

An experimental design approach for investigating and modeling wax deposition based on a new cylindrical Couette apparatus

The authors report an experimental study carried out through a newly developed Couette apparatus on evaluating the influence of important operating factors such as wall oil temperature, temperature difference (△T) and flow rate. It is found that wax crystal solubility coefficient, temperature gradient, and sheer stress at the wall play leading roles on the internal mechanism. CFD software is adopted for numerical calculation and the result agrees well with the distribution of the flow and temperature field in actual pipelines so that precise parameter values under related experimental conditions are obtained. An improved dynamic wax deposition model considering the enhance effect of resin and asphaltene as well as static deposition condition is established with an average error of 5.6%. Thus the feasibility of the method based on the new apparatus for further research is implied.     

延长油田高含水油井井筒结蜡速率预测模型优化

结蜡速率计算是预测油井结蜡的关键参数,目前针对油井井筒的结蜡速率预测模型相对较少,且大多以机理模型为主,计算参数众多,现场应用不便.延长油田油井含水率普遍较高,常用的普适性经验模型预测准确度低.因此,重新考虑含水率对结蜡速率的影响,开展了含水率对结蜡速率影响的室内研究,基于实验数据与简化后的经验公式,拟合了含水率分别为...     

海上油井井筒结蜡剖面预测新模型

为了缓解井筒结蜡给海上油田油气开采造成的消极影响,研究了海上结蜡油井的蜡质沉积规律,并建立了一种海上油井井筒结蜡剖面预测新模型。该模型基于对4种现有模型的机理分析,采用理论与试验相结合的方法,综合考虑了分子扩散、剪切弥散和蜡层的老化与剥蚀损失等结蜡机理。通过实例对新模型与4种现有模型的结蜡剖面预测结果进行了对比分析,并结合渤海油田海上结蜡油井的生产数据,检验了新模型对结蜡井筒流体温度和压力的计算精度,新模型计算井口温度的相对误差为1.32%,计算井下压力的相对误差为0.30%,计算精度良好;利用新模型分析了生产时间、产量、含水率和生产气油比等影响结蜡因素的敏感性,认为结蜡厚度随生产时间递增,受产量和含水率的影响较大,受生产气油比的影响相对较小。研究结果表明,新模型能够较为准确地预测海上结蜡电动潜油离心泵油井井筒的结蜡剖面,可以为海上电潜泵结蜡井的清蜡防蜡工艺优选与实施提供指导。      

Wax deposition during production of waxy crude oil and its remediation

In the current paper, fundamental aspects of wax deposition problems in pipeline are defined, and characterization of paraffin and their solubility tendencies have been discussed. Wax deposition depends on flow rate, the temperature differential between crude and pipe surface, the cooling rate, and surface properties. The physico-chemical characterization of crude oil is determined. The experiments were carried out in “Cold Finger Apparatus.” Best pour point depressant for the selected crude oil has been found out as Lubrizol-6682 among different chemicals available that reduces the pour point from 36° to 12°. The deposition of paraffin wax, its dispersion, and inhibition were studied with available chemicals and by the optimization of suitable additives for particular well. Kinetics of crude oil in terms of time and differential temperature has also been studied and effective dispersion times are observed for particular oil. It is found that dispersion is effective within 30–60 min of starting. Kinetic study of oil with respect to differential temperature is done in two ways either by varying ambient/surface temperature or pumping/reservoir temperature. The tendencies of wax deposition on different sample with neat and treated crude are observed and ideal differential temperature for particular oil to flow is determined.     

一种高效防蜡降凝剂的研制与应用

姬塬油田部分区块原油蜡质、胶质含量高,油井结蜡严重,现有防蜡技术在该区块应用效果不佳,针对上述问题利用蜡晶晶格扭曲机理和微乳液机理,将蜡晶改进剂以纳米颗粒的形式均匀分布在水中,制备出一种不易燃烧、防蜡降黏效果好、密度较大、冬季可方便使用的高效防蜡降凝剂.研究结果表明,在最佳的合成工艺条件下制备出的高效防蜡降凝剂,纳米粒...     

管输温度对EVA型防蜡剂防蜡效果的影响

采用Couette蜡沉积实验装置研究了聚乙烯醋酸乙烯酯(EVA)型防蜡剂对长庆原油蜡沉积特性的影响,分析了不同管输温度条件下EVA型防蜡剂的防蜡效果。研究发现,与空白原油相比,加剂原油的蜡沉积速率大幅降低,同时蜡沉积物的老化速率升高。无论是在恒定油壁温差还是在恒定壁温条件下,EVA型防蜡剂的防蜡效率均随油温的升高而不断降低,EVA对蜡沉积物老化速率的提升幅度均随油温的升高而不断增大。通过分析EVA型防蜡剂对长庆原油流动特性、低温胶凝结构特性及微观蜡晶形貌的影响,阐明了EVA型防蜡剂对长庆原油蜡沉积特性的影响机理,并从蜡沉积物初始凝油层抗剪切强度及蜡分子扩散速率2个角度揭示了管输温度对EVA型防蜡剂防蜡效果的影响。     

海上高含蜡油田井筒清蜡周期预测图版建立及应用

渤海部分高含蜡油井投产后面临比较严重的井筒结蜡问题,现场作业人员一般根据生产经验确定清蜡周期,导致准确度低、清蜡作业成功率有限。根据海上油井生产管柱特征,以Ramey温度场计算数学模型为基础,结合井筒结蜡速率模型计算得到了井筒结蜡剖面,推导建立了电潜泵井清蜡周期预测方法,并进一步绘制了某油田A区块清蜡周期和清蜡深度预测图版。结果表明,清蜡周期随产液量的下降呈幂函数形式变短,随含水率增加呈指数函数形式增加。根据清蜡周期预测图版,预测3口井的清蜡周期分别为11 d、15 d、46 d,实际清蜡周期分别为8 d、12 d、39 d,预测结果与实际基本吻合。该方法同样适用于陆地油田自喷井确定清蜡周期和清蜡深度,对高含蜡电潜泵井、自喷井及时制定清防蜡措施具有借鉴意义。     

基于原油及蜡样实验的油井井筒结蜡规律综合分析

高含蜡原油生产时,油井井筒结蜡的影响因素很多也很复杂,仅通过对油样结蜡实验分析或者井筒结蜡厚度的理论分析进行结蜡规律研究比较片面,现场井筒蜡样实验分析及不同气油比压力下结蜡规律实验是必要的补充。以安塞油田高平2井区长10油层原油及蜡样为研究对象,通过黏温曲线测定析蜡温度、原油全组分实验分析、蜡样全组分实验分析、不同气油比和压力条件下实验分析、不同产液量和含水率的理论计算分析等多种手段,全面综合地研究和认识其结蜡规律,为制定清防蜡措施提供了更详实的依据。     

Influencing factors governing paraffin wax deposition of heavy oil and research on wellbore paraffin remover

Abstract

Wax deposition is harmful to oil wells, especially for waxy heavy oils at low temperature. The influencing factors on wax deposition of heavy oil were studied and a kind of O/W emulsion type wellbore wax remover was investigated. The results showed that the wax deposition rate of Jinghe heavy oil increased with the increasing wax content and asphaltenes content but decreased with the increasing water content. The oil in water emulsion type paraffin remover was prepared and it showed both good wax dissolution and paraffin prevention ability and can save large quantities of solvent. The results of this study provides a possible way for waxy heavy oils to dissolve wax, to prevent wax deposition and reduce the viscosity of heavy oils by emulsification together, which is helpful to reduce the frequency of hot washing and enhance oil recovery for waxy heavy oils.     

Transportation technology with pour point depressant and wax deposition in a crude oil pipeline

The authors systematically studied transportation technology with pour point depressant and wax deposition in an industrial crude oil pipeline. Experiment results manifest that beneficiated oil acquires obvious modification effect and the reheating temperature of intermediate heat stations should be above 55°C to avoid effect deterioration. Heating schemes are made with lower heating temperature and wider output range. Moreover, an applicable wax deposition model is established to predict wax deposition distribution along the pipeline under various operating conditions. Wax deposition rate varies severely along the pipeline and it is necessary to consider its non-uniformity in production.     

Evaluation on the effects of wax inhibitor and optimization of operating parameters for wax deposition in Malaysian crude oil

The complex phenomenon of wax deposition subject to thermal gradient in crude oil is one of the biggest challenges in petroleum industry. In this comparative study, two inhibitors which were poly(ethylene-co-vinyl acetate) (EVA) and xylene were investigated in terms of rate of wax deposition in Malaysian crude oil using one-factor-at-a-time (OFAT) approach and cold finger methods. Stirring rate and cold finger temperature were optimized using response surface methodology (RSM) after being investigated using OFAT. It can be concluded that EVA had higher capability of reducing wax in two different conditions where the minimum point of wax reduction was found at 400 rpm with 63.5% paraffin inhibition efficiency (PIE) and 10°C with 64.7% of PIE. The amount of waxes collected for each parameter were 0.35 and 0.49 g, respectively. To minimize the wax deposit amount, RSM approach was applied using rotatable central composite design (CCD). The result shows that the amount of wax deposit decreased significantly with the increase of temperature and the stirring rate which were set at 400 rpm and 19°C, rescpectively. The amount of wax deposit was successfully reduced to the minimum value of 0.0095 g after the optimization.     

宁东油田清蜡、防蜡技术分析

在原油开采过程中,随着温度、压力的降低和气体的析出,溶解的石蜡便以结晶体析出、逐渐长大聚集最终沉积在管壁等固相表面上,即出现所谓的结蜡现象.结蜡会堵塞产油层,降低油井产量,同时也会增大油井负荷,造成生产事故.油井结蜡是影响油井高产、稳产的主要因素之一,清蜡和防蜡是高含蜡油井常规管理的重要内容.通过收集整理现场资料、分析原油性质和综合评价不同清防蜡技术的经济效果,确定宁东油田采用热力清蜡和化学防蜡技术较为合适.     

模拟延长油田CO_2驱油过程原油结蜡特性研究

通过对某CO2驱油区块的不同CO2分压条件下原油结蜡倾向和原油结蜡特性评价,计算出原油的结蜡速率、结蜡率及蜡含量,分析了原油的析蜡曲线特性。结果表明,CO2分压增大时原油的结蜡速率和结蜡率提高,蜡含量降低,蜡析出更明显;经CO2处理作用后原油析蜡点向低温方向移动,其蜡含量也相应地比未处理油样的蜡含量降低。     

Screening of factor influencing wax deposition using full factorial experimental design

The purpose of this work was to study the rate of wax deposition of Malaysian crude oil using full factorial design. Important parameters affecting wax deposition such as experimental duration, speed of rotation, cold finger temperature, and inhibitor concentration were investigated. The individual effects of variables and its interaction effects towards the dependent variables were studied. Wax deposit is the dependent variable. The results of the study showed that less wax deposit was obtained (0.75 g) with optimal conditions of initial poly(ethylene-co-vinyl acetate) concentration of 5000 ppm, 2 h duration without rotation speed, and 15°C cold finger temperature. These results demonstrate that cold finger temperature and experimental duration could be the main factors affecting wax deposit formation. The minimum amount of wax deposit obtained could reduce the chances of blocked pipelines; however, crude oil production increased. Nevertheless, Design Expert can be a valuable tool to quantify and detect the special relationships of two of more factors known as interactions regarding how they factors could affect a process, especially for screening purpose.     

普适性结蜡模型研究

根据原油在管道内流动特性及析蜡规律,提出了有效析蜡量的计算方法.利用F检验法筛选了原油结蜡的主要影响因素,包括原油黏度、管壁处剪切应力、温度梯度及管壁处蜡晶溶解度系数.利用9种原油室内环道结蜡实验数据,按照逐步线性回归的方法,得到了含蜡原油的普适性结蜡模型.该模型不需进行结蜡模拟实验,只需根据原油的黏度、析蜡特性及密度等物性参数就可预测原油的结蜡规律.在未进行室内结蜡模拟实验的情况下,利用普适性结蜡模型预测了中宁-银川输油管道不同工况下沿线结蜡分布,并和现场运行参数进行了对比,平均误差为6.32%,最大误差为20%,预测结果为现场清管作业提供了依据.