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.     

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。     

Evaluation of the inhibitor selection on wax deposition for Malaysian crude oil

Wax precipitates from crude oil when a fluid is cooled down below its wax appearance temperature (WAT). This particularly happens during the transportation of crude oil in the pipeline system. In this study, chemical inhibitors were chosen to prevent and reduce wax formation using seven different types of inhibitors, which are poly (ethylene-co-vinyl acetate) (EVA), poly (maleic anhydride-alt-1-octadecene) (MA), diethanolamine (DEA), cocamide diethanolamine (C–DEA), toluene, acetone, and cyclohexane. The total waxes deposited from the cold finger test are subjected to the type of inhibitor, rotation speed of impeller, and inhibitor concentration. EVA is suggested as the most effective inhibitor based on the amount of wax deposit weight and the value of viscosity. Therefore, this result might be useful for further research work related to wax deposition in the area of crude oil production.     

降凝剂对南阳原油管壁蜡沉积特性的影响

以魏荆线管道所输送的南阳原油为研究对象,利用旋转式动态结蜡装置,考察了添加降凝剂对原油蜡沉积规律的影响。实验结果表明,添加降凝剂改变了蜡晶的生长历程,增大蜡晶体积并阻碍三维网状结构的形成,弱化了管壁沉积蜡晶的结构强度,减小了胶凝原油的屈服强度;在保持壁面温差、油品温度、旋转筒转速相同的情况下,在低流速区间,添加降凝剂会增大南阳原油的蜡沉积速率,在高流速区间则对管壁结蜡具有一定的抑制作用;降凝剂的添加使壁面剪切应力成为影响加剂南阳原油蜡沉积速率的主要因素。     

高凝原油管道输送蜡沉积规律实验研究

针对高凝原油在管道输送过程中管壁结蜡等问题，通过室内建立的小型管流结蜡环道实验装置，模拟输油管道运行中某一管段的蜡沉积情况，研究了含蜡原油的蜡沉积速度，考察了蜡的沉积规律受温度的影响。通过计算，确定了实验条件下的结蜡量，并利用差热扫描量热仪从微观角度分析测试了蜡沉积物的特性，进而探讨了结蜡机理和影响管壁结蜡的因素。     

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.     

Evaluations of the effect of selected wax inhibitive chemicals on wax deposition in crude oil flow in sub-sea pipe-lines

Comparative studies were made on the effect of different wax inhibitive chemicals on the wax deposition volume during crude oils flow in pipeline. Two crude oils from Ovhor and Jisike oil fields in the southern part of Nigeria were used in the study. The four identified chemicals: Alkyl sulphonates (wax dispersant), polyethylene (wax inhibitors/crystal modifier), acrylate ester copolymer (pour point depressant, PPD) and xylene (wax solvents) inhibit wax deposition to varying degree of between 14.6–44.9% for crude oil A, and between 21.6–41.4% for crude oil B when 1500 ppm of each chemical was mixed with the crude oil sample. The optimal wax inhibition formulation of polyethylene, xylene, acrylate ester polymer and alkyl sulphonate contains 40.4, 19.2, 27.6, 12.8% and 36.3, 21.5, 25.8, 16.4% for crude oil A and B respectively. Applications of the optimal formulated mixtures of the above chemicals inhibit wax deposition by 58.9% and 62.4% for crude oil A and B respectively.     

Determination of wax content in crude oil

Wax deposition is one of the chronic problems in the petroleum industry. The various crude oils present in the world contain wax contents of up to 32.5%. Paraffin waxes consist of straight chain saturated hydrocarbons with carbons atoms ranging from C18 to C36. Paraffin wax consists mostly with normal paraffin content (80–90%), while, the rest consists of branched paraffins (iso-paraffins) and cycloparaffins. The sources of higher molecular weight waxes in oils have not yet been proven and are under exploration. Waxes may precipitate as the temperature decreases and a solid phase may arise due to their low solubility. For instance, paraffinic waxes can precipitate out when temperature decreases during oil production, transportation through pipelines, and oil storage. The process of solvent dewaxing is used to remove wax from either distillate or residual feedstocks at any stage in the refining process. The solvents used, methyl-ethyl ketone and toluene, can then be separated from dewaxed oil filtrate stream by membrane process and recycled back to be used again in solvent dewaxing process.     

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.     

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。     

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。     

Effect of drag reducer and pour point depressant on the wax deposition of crude oil pipeline

In this paper, the data of wax precipitation before and after the addition of the additives showed that the addition of the drag reducing agent (DRA) and the pour point depressant (PPD) cannot change the wax appearance temperature (WAT) of crude oil. When the dosage of DRA is small, the DRA cannot increase, stop, or slow down the precipitation of wax crystals. The addition of PPDs has no influence on the amount of precipitated wax crystals. From the GPC analysis, the molecular weight of the wax deposit samples in Linpu pipeline is from 500 to 76,800, which indicates that there is no enrichment of DRA in wax deposit samples. The results of IR show that the C?O group was not detected in the wax deposit sample of the Wei Jing pipeline, which indicates that there is no enrichment of the PPDs in wax deposit samples. The results showed that the DRA and PPD have no obvious effect on crude oil pipeline wax deposition.     

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.     

Effect of surfactants and their blend with silica nanoparticles on wax deposition in a Malaysian crude oil

The present study investigated the wax deposition tendencies of a light Malaysian crude oil(42.4° API), and the wax inhibiting potential of some surfactants and their blends with nanoparticles. With the knowledge that the majority of the wax inhibition research revolved around polymeric wax inhibitors, which cause environmental issues, we highlighted the potential of surfactants and their blend with SiO_2 nanoparticles as wax deposition inhibitors. Different surfactants including oil-based, silane-based, Gemini and bio-surfactants were considered as primary surfactants. The primary surfactants and their respective blends at a concentration of 400 ppm were screened as wax inhibitor candidates using cold finger apparatus. The screening results showed a significant influence on the paraffin inhibition efficiency on wax deposition by using 400 ppm of silane-based surfactant, which decreased the wax deposition up to 53.9% as compared to that of the untreated crude oil. The inhibition efficiency among the silane-based surfactant(highest) and bio-surfactant(lowest)revealed an appreciable difference up to 36.5%. Furthermore, the wax from the treated sample was found to deposit in a thin gel-like form, which adhered inadequately to the surface of the cold finger. A further investigation by blending the 400 ppm silane-based surfactant with a 400 ppm SiO_2 nanoparticle suspension in a load ratio of 3:1 found that the wax inhibition decreased up to 81% as compared to the scenario when they were not added. However, we have shown that the synergy between the silane-based surfactant and the nanoparticles is influenced by the concentration and load ratio of surfactant and nanoparticles, residence time, differential temperature and rotation rate.     

Study of asphaltene deposition from Tahe crude oil

Borehole blockage caused by asphaltene deposition is a problem in crude oil production in the Tahe Oilfield, Xinjiang, China. This study has investigated the influences of crude oil compositions, temperature and pressure on asphaltene deposition. The asphaltene deposition trend of crude oil was studied by saturates, aromatics, resins and asphaltenes (SARA) method, and the turbidity method was applied for the first time to determine the onset of asphaltene flocculation. The results showed that the asphaltene deposition trend of crude oil by the turbidity method was in accordance with that by the SARA method. The asphaltene solubility in crude oil decreased with decreasing temperature and the amount of asphaltene deposits of T739 crude oil (from well T739, Tahe Oilfield) had a maximum value at 60 o C. From the PVT results, the bubble point pressure of TH10403CX crude oil (from well TH10403CX, Tahe Oilfield) at different temperatures can be obtained and the depth at which the maximum asphaltene flocculation would occur in boreholes can be calculated. The crude oil PVT results showed that at 50 , 90 and 130 o C, the bubble point pressure of TH10403CX crude oil was 25.2, 26.4 and 27.0 MPa, respectively. The depth of injecting asphaltene deposition inhibitors for TH10403CX was determined to be 2,700 m.     

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.     

Prediction of wax content in crude oil and petroleum fraction by proton NMR

In this study, we develop a simple method for estimation of wax content in crude oil and their fractions. The traditional way of wax estimation follows low-temperature chemical extraction based gravimetric methods; those are tedious, time-consuming, need a lot of chemicals and solvents and may produce an erroneous result if not done properly. This study proposes an alternative method i.e. ¹H NMR based correlation study to Englar Holde’s wax determination method. In this study, the NMR derived structural parameters of petroleum fractions are used to estimate the wax content of petroleum fractions. A Model equation is developed based on Fourier equation and validated with different Indian origin samples with a proper fitting and high predictability.     

预测原油中固溶物沉淀的热力学模型

原油中通常含有大量重组分，在一定的温度和压力下它们将以固体形式沉淀下来，引起堵塞管道及许多油藏开发问题，论文提供了一个预测液固相平衡的热力学模型。应用该模型可以进行闪蒸计算和边界计算，确定固体组分沉淀的临界温度和临界压力，从而在开发中有取相应措施，它对于指导油气田开发有重要的理论意义和实际意义。     

南阳含蜡原油混合输送的结蜡特性

以南阳油田含蜡原油(1#原油、2#原油及其混合原油)与沉积物为研究对象,采用族组成分析、流变性测量、显微观察和气相色谱分析的方法,探讨了含蜡原油混合输送的结蜡特性。实验结果表明,混合过程主要表现为物理变化;混合原油的反常点与1#原油一致,析蜡点显著升高;与混合原油相比,沉积物中的蜡含量显著升高,沥青质含量增大,胶质含量显著减小,反常点和黏度显著增大,黏度随温度变化更敏感;沉积物与1#原油的蜡晶颗粒大小相差不大;沉积物和1#原油均含有C_(37)~+组分而2#原油没有;混合原油和沉积物的物理性质与1#原油基本一致,表明1#原油对混合原油的基本性质和结蜡特性起到了主要作用。