Parametric analysis of the effect of operation parameters on asphaltene deposition: An experimental study

Changing pressure, temperature, and composition cause instability in crude oil and create a problematic issue which is called asphaltene deposition. Asphaltene deposition causes problems in wettability alteration and flow assurance in different parts of petroleum industry so asphaltene deposition becomes a challenging issue in petroleum engineering. Hence, it is necessary to predict asphaltene deposition and investigate parameters which effect on asphaltene deposition. In this contribution, because of similarity between pore throat of reservoir rock and capillary tube, to investigate parameters such as asphaltene content, precipitant ratio, flow rate, and temperature effect on asphaltene deposition, a capillary setup was constructed and a model was developed to relate pressure drop along capillary tube to permeability reduction.     

Investigation of the asphaltene deposition along the flow of the oil in tubing: Experimental study and a parametric analysis

In this work, a novel experimental setup was designed and utilized to carry out the n-alkane induced asphaltenes for understanding the kinetics of deposition and also effects of oil velocity, oil-precipitant volumetric dilution ratio, and temperature on the rate of asphaltene deposition. As the deposited layer of asphaltenes makes it difficult for the flow of oil along the tube, measurement of the pressure drop across the tube section of setup enabled the measurement of the amount and extent of deposition process at desired condition. The experimental results revealed that increasing the velocity of fluid across the pipe dominance the shear force on asphaltene deposit and cause remobilization of part of the deposit into the flowing fluid in contrary to oil-precipitant ratio, where deposition rate is enhanced with increasing DR ratio. The results of this work elucidate some less-addressed shadows of dynamics of flow blockage in pipelines and could create a better framework for conducting forthcoming experiments     

Flow Characteristics of Crude Oil with High Water Fraction during Non-heating Gathering and Transportation

In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil, the effect of temperature, water fraction, and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield. Four distinct flow patterns were identified by the photographic and local sampling techniques. Especially, three new flow patterns were found to occur below the pour point of crude oil, including EW/OW stratified flow with gel deposition, EW/OW intermittent flow with gel deposition, and water single-phase flow with gel deposition. Moreover, two characteristic temperatures, at which the change rate of pressure drop had changed obviously, were found during the change of pressure drop. The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil, while the pressure drop reached the peak at this temperature. An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate. The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.     

Study on the wax deposition of waxy crude in pipelines and its application

An experimental loop for the wax deposition study is established; a novel method to determine the thickness of the wax deposition in the experimental loop is developed, taking into account the impact of the instant temperature decreasing of the test section wall which leads to the increasing of the viscosity of the crude oil near the pipe wall and the distortion of the flow field in the pipe. The wax deposition characteristics of the QH crude are studied using the experimental loop. For the QH crude oil, there is a peak area of the wax deposition when it is 40 °C around. And very little deposition emerges when the temperature is not only higher than the wax appearance point but also lower than the temperature of solidification. It is also proved in the lab that the shearing dispersion of the wax crystal particles plays little role in the wax deposition when the shearing rate is high. The observation of the pipe which is cut in the field shows that the laying of the wax deposition in the pipe is very clear, and the wax deposition caused by the shearing dispersion exists clearly. From the angel of the shutdown temperature drop and safely restart for the hot oil pipeline, it is concluded that there is a permissible critical thickness of the sedimentary layer for the low flow rate pipelines.     

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.     

Wax Deposition in Flow Lines Under Dynamic Conditions

The wax deposition in the tubing, pipeline, and surface flow line is the major problem in the oil fields. It generates additional pressure drop and causes fauling and ultimately increases the operating cost during production, transportation, and handling of waxy crude oil. In this work, attempts were made to study the wax deposition in the flow lines due to Indian crude oil under dynamic condition. The experimental work was carried out for neat crude oil and pour point depressants treated crude oil at different ambient/surface temperature and pumping/reservoir temperature. It was observed that temperature has significant effect on the wax deposition of the crude oils. From these studies, ideal temperature of crude oil to pump in the pipeline or flow line was determined. The present investigations also furnishes that the selected pour point depressant in this work decreases the wax deposition significantly and may be used for controlling the wax deposition problems in case of Indian crude oil.     

高含水、高粘、高凝点原油低温管输粘壁现象研究

一些高含水原油在低于凝点输送时,水包油乳状液中的水滴会以凝胶的形式粘在管道内壁,称“粘壁现象”,原油输送过程中粘壁现象会造成管道局部或全部堵塞,造成能源浪费。通过室内环道实验,研究了高含水、高粘、高凝点原油在管道内低温输送时的粘壁规律。发现含水率、剪切率是影响原油粘壁速率和粘壁温度的主要因素,水包油乳状液的含水率越低、剪切率越小粘壁现象越严重。提出粘壁温度判别式,建立粘壁速率模型,据此建立高含水时压降计算软件。     

海底多相流混输管道压降计算主要影响因素分析

以我国海洋油气开发工程为例,以黑油物理模型为基础,利用PIPERFLO软件,分析了不同压降计算模型、起输温度、气体流量及总传热系数(K)对海底多相流混输管道压降计算的影响。用不同压降计算模型得到的混输管道的压降结果相差很大,在设计混输管道时,应根据实际情况选择合适的模型。设计高粘原油混输管道时,应根据油品物性将起输温度控制在适当的范围;设计低粘原油混输管道时,在满足管道终端温度要求条件下,应尽量降低起输温度。海底油气混输管道存在一个最小压降气液比,按此气液比确定高粘原油混输管道的气体输量,可降低管输原油粘度,从而减小管道压降。对海底多相流混输管道应进行一定的敏感性变量分析和结果预测,以保证管道具有一定的抗波动能力。     

水平井筒射孔完井变质量流动压降规律

影响水平井产能和向井入流剖面的因素很多,水平井筒沿程压降是其中一个重要因素。结合水平井筒生产实际,在大庆多相流试验环道基础上,设计了壁面注入系统和变质量流动试验段,针对射孔水平井筒变质量流动规律进行了单相和两相变质量流动试验研究。结果表明,单相水平井筒沿程压降随注入比变化,并且存在临界注入比,当注入比超过临界注入比时,压降随着注入比增加显著。进一步的数值模拟研究揭示了其中的原因:当超过临界注入比后,射孔孔眼下游出现流动分离,混合压降开始起作用,从而引起压降的显著增加。油水两相变质量流动除了受注入比影响外,还受到含水率变化的影响,在高流量条件下,40%含水率时压降最高,流型为分散流型;低流量下,压降随含水率变化不大,流型为分层流型。该研究结果对完井设计有一定指导意义。     

超深水平井尾管悬挂器下部环空压力预测及其应用

超深水平井多封隔器分段改造作业过程中,井筒温度下降造成尾管悬挂封隔器下部环空压力下降,易造成尾管悬挂封隔器、下部分段改造封隔器和油管柱失效。针对典型分段改造水平井井身结构,开展分段改造过程中尾管悬挂封隔器下部环空压力变化的影响因素和潜在后果分析,综合考虑油管柱鼓胀效应引起的环空体积变化、井筒压力温度变化引起的环空流体体积变化和井筒温度变化引起的油管柱体积变化对尾管悬挂封隔器下部环空压力的影响,建立了尾管悬挂封隔器下部环空压力变化预测模型。以塔里木油田一口超深水平井为例,开展了分段改造过程中尾管悬挂封隔器下部环空压力预测,并在此基础上开展了封隔器和改造管柱力学分析。分析结果表明:超深水平井分段改造过程中,由于井筒温度场急剧下降,尾管悬挂封隔器下部环空压力相对坐封工况将发生大幅下降,从而给改造管柱和封隔器带来非常大的失效风险,超深水平井分段改造管柱设计过程中必须充分考虑该因素。     

海底管道油气混输关键装备的实验研究

多相增压泵、混相计量仪和油气水分离器是实施海底管道长线混输中的关键设备。中国科学院力学研究所用于研究这些关键设备的模拟实验装置,包括了集重力、膨胀和离心原理于一体的高效油气水分离器和引射增压泵、叶轮增压泵等设备。首先采用控制气液两相压比和流量比的方法实现了水平、垂直管内各种流态的仿真模拟,并用狭缝光和快速摄影技术得到了清晰的流态照片,用硅阻差压式压力传感器测量了一定距离内管流压降和同一截面不同位置的压差分布;然后介绍对上述设备进行各种流态下分离器的分离效果以及引射增压、叶轮增压泵的性能、效率试验的方法和初步结果。     

Prediction the variation range of wax deposition with temperature of crude oil in a flow loop

Wax deposition under different temperature conditions was investigated in a flow loop, using a local crude oil with a wax content of 22.5%. The results revealed that the wax deposition increases with increasing coolant temperature. However, the amount of deposit increased initially with increasing oil temperature and then decreased. Based on these results, the corresponding temperature ranges were divided into three ranges: hot flow, sensitive precipitation of wax crystal, and cold flow. Based on diffusion mass, a method and steps for determining the temperature dependence of wax deposition were proposed.     

大庆原油管输结蜡规律与清管周期的确定

在确定不同流态区管壁处剪切应力、蜡晶溶解度系数、径向温度梯度及管道沿线温降分布的基础上,回归建立了适用于描述大庆油田某两联合站间输油管道蜡沉积的结蜡模型。根据差压法原理,建立了研究原油管输结蜡过程室内模拟试验装置,并覆盖该输油管道的典型工况条件开展了管输原油结蜡模拟试验。相对偏差分析表明,结蜡模型预测结果与试验值的适配性良好。进而在预测运行时间对该输油管道结蜡影响的基础上,结合结蜡层厚度对管道轴向温降及压降的作用,确定了年季节最高与最低土壤温度期的清管作业周期分别为4个月和3个月。     

Prediction of asphaltene deposition during turbulent flow using heat transfer approach

In this study, asphaltene deposition from crude oil has been studied experimentally using a test loop and prediction using theoretical study under turbulent flow (Reynolds numbers below 5000). The effects of many parameters such as oil velocity, surface temperature and concentration of flocculated asphaltene on the asphaltene deposition were investigated. The results showed that asphaltene deposition thickness increases with increasing both surface temperature and concentration of flocculated asphaltene and decreasing oil velocity. Thermal approach was used to describe the mechanisms involved in this process and the results of data fitting showed that there are good agreements between the results of the proposed model and the measured asphaltene deposition rates.     

Modeling aspects of oil–water core–annular flows

The annular flow pattern of two immiscible liquids having very different viscosities in a horizontal pipe—also known as ‘core–annular flow’—provides an attractive means for the pipeline transportation of heavy oils since the oil tends to occupy the center of the tube, surrounded by a thin annulus of a lubricant fluid (usually water). The correspondent pressure drop is comparable to the flow of water only in the same pipe at the total volumetric flow rate. Recently, successful experiments led by the author and his group indicated that the core flow technology might be even more attractive for heavy oil production in vertical wells, due to the symmetry of the flow and the favorable effect of buoyancy. In this paper, several aspects of core–annular flow modeling are analyzed and discussed in the light of experimental data. First, criteria for existence of stable core flow are proposed, which show the essential role played by interfacial tension. Phenomenological models, based on mass and momentum balances, are developed for volume fraction and pressure drop and compared with data for both horizontal and vertical oil water core flows. The very good agreement observed is encouraging.     

斜针翅管套管换热器壳程传热与压降的数值模拟

以水-柴油换热为对象,对直针翅管和斜针翅管套管换热器的壳程传热与压降性能进行了实验研究与数值模拟。采用Fluent软件模拟了柴油在直针翅管和斜针翅管套管换热器壳程层流流动时的流场、温度场以及传热与压降性能。结果表明,在相同流动条件下,直针翅管与光管套管换热器的总传热系数K的比值模拟值与实验值吻合较好。同时分析了斜针翅管纵向流流动特性,压降低于直针翅管换热器,强化传热为光管的1.5～2倍,并设计应用于炼油换热器中。     

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。     

泡沫在不同渗透率级差填砂管中的调驱特性研究

为了解决胜利油田稠油油藏开采时蒸汽波及效率低的问题,利用泡沫作为蒸汽流度调剖剂,在温度为90℃的条件下通过物理模拟实验测算了泡沫在不同渗透率级差的两并联岩心管中的阻力因子、高低渗管中产液速度变化特征及泡沫驱油时的采出程度与注入压差的变化特征。实验结果表明：起泡剂FCY产生的泡沫阻力因子随渗透率级差的增大而先增大后减小;泡沫能使高渗管的产液速度减小,而使低渗管的产液速度增大;并联岩心管饱和油后采用泡沫驱,注入0.85PV泡沫时,才能形成有效封堵,而且渗透率级差越大,最终注入压差越低;泡沫驱能同时提高高渗管和低渗管的原油采出程度,但随着渗透率级差的增大,高渗管采出程度略有增加,而低渗管采出程度略有降低。     

气井井筒条件下单液滴动力学特征及其携带临界气流速

准确认识气井井筒条件环状流场中单液滴的动力学特征和正确计算液滴携带临界气流速是气井连续携液机理研究的重要内容之一.为深入研究气井井筒高温高压条件下液滴的动力学特征,首先建立了气流场中单液滴动力学特征的数值模型及求解方法,采用流体体积函数法(VOF)模拟液滴表面结构,利用直接数值模拟方法(DNS)模拟液滴周围气流场,开发...     

流动型态对气液总压降的影响实验研究

针对深层稠油在井筒举升过程中形成多相混合流体造成原油举升困难的问题,采用高温高压井筒模拟装置,在高温高压实验数据基础上,依据前人模型,推导并修正得出油气水三相压降计算模型,实验数据与模型拟合度高达0.98以上,并得出不同气液比下的气相分布因数C_(og)值。实验结果表明,泡状流的C_(og)值最小,气相分散程度高,气液混合物分布均匀,对气液总压降的降低效果最为显著。因此,气液流态保持在泡状流区间,更有利于生产。流动型态对气液总压降的研究为稠油开采中举升压降的精确预测提供了新的思路。