Prediction of Diffusion Coefficients for Binary Gas System

A new formula has been developed to estimate diffusion coefficients for a binary system for some gases dependent on temperature, pressure, molecular weight, and a Pitzer acentric factor in a different range of temperatures. In this work, an introduction of the available observed data develops a new correlation for the effect of these parameters on the prediction of diffusion coefficients.     

天然气扩散系数的系统研究

在介绍天然气扩散系数测试方法的基础上,指出了目前天然气扩散系数测试中存在的问题,建立了实测天然气扩散系数的地层条件的校正方法。根据天然气扩散系数的影响因素分析,建立了古天然气扩散系数的恢复方法,并将天然气扩散系数的研究方法应用于松辽盆地徐家围子断陷深层泥岩扩散系数的研究中,其结果符合研究区实际地质条件,证实了该方法的实用性。     

The Determination of Effective Diffusivity Coefficients in a Solvent Gas Heavy Oil System for Methane

Abstract

In this investigation, an accurate high pressure and temperature diffusion setup was applied to measure the diffusion coefficients of methane in Iranian heavy oils in presence and absence of porous media by using the pressure-decay method. The solvent diffusivity in heavy oil was determined by both graphical and numerical methods. In addition, the effects of the porous medium and the temperature on the molecular diffusion coefficient of the solvent gas in the liquid phase were discussed and finally, using experimental data, a functionality dependence of molecular diffusivity on temperature and porous medium characteristics was proposed.     

Diffusion Coefficient of a Binary Liquid System

A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error.     

Diffusion Coefficient of a Binary Liquid System

Abstract

A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error.     

Liquid-phase Mutual Diffusion Coefficients for Heavy Oil + Light Hydrocarbon Mixtures

Liquid-phase mutual diffusion coefficients are a key parameter in reservoir simulation models related to both primary production and envisioned secondary recovery processes for heavy oil and bitumen. The measurement of liquid-phase mutual diffusion coefficients in bitumen and heavy oil + light hydrocarbon or gas mixtures present numerous experimental and data analysis challenges due to the viscosity and opacity of the mixtures, the variability of density, viscosity and mutual diffusion coefficient with composition, and the multi-phase nature of these mixtures. Data analysis challenges are particularly acute. For example, recently reported mutual diffusion coefficient values for liquid mixtures of bitumen + carbon dioxide vary over three orders of magnitude when different analysis methods are applied to the same experimental data. In this contribution, we illustrate the importance of measuring composition profiles within liquids as a function of time, as a basis for mutual diffusion coefficient computation, and for allowing explicitly for the variation of diffusion coefficient and liquid density with composition in the analysis of composition profile data. Such inclusions eliminate apparent temporal variations of mutual diffusion coefficients and yield values consistent with relevant theories and exogenous data sets. Liquid-phase mutual diffusion coefficients computed for the mixtures Athabasca Bitumen + pentane and Cold Lake Bitumen + heptane exemplify the experimental and data analysis approaches.     

Liquid-phase Mutual Diffusion Coefficients for Heavy Oil + Light Hydrocarbon Mixtures

Abstract:

Liquid-phase mutual diffusion coefficients are a key parameter in reservoir simulation models related to both primary production and envisioned secondary recovery processes for heavy oil and bitumen. The measurement of liquid-phase mutual diffusion coefficients in bitumen and heavy oil + light hydrocarbon or gas mixtures present numerous experimental and data analysis challenges due to the viscosity and opacity of the mixtures, the variability of density, viscosity and mutual diffusion coefficient with composition, and the multi-phase nature of these mixtures. Data analysis challenges are particularly acute. For example, recently reported mutual diffusion coefficient values for liquid mixtures of bitumen + carbon dioxide vary over three orders of magnitude when different analysis methods are applied to the same experimental data. In this contribution, we illustrate the importance of measuring composition profiles within liquids as a function of time, as a basis for mutual diffusion coefficient computation, and for allowing explicitly for the variation of diffusion coefficient and liquid density with composition in the analysis of composition profile data. Such inclusions eliminate apparent temporal variations of mutual diffusion coefficients and yield values consistent with relevant theories and exogenous data sets. Liquid-phase mutual diffusion coefficients computed for the mixtures Athabasca Bitumen + pentane and Cold Lake Bitumen + heptane exemplify the experimental and data analysis approaches.     

海上平台冷放空可燃气体扩散的数值模拟研究

为研究烃类物质大气排放所引起的潜在危险,针对某海上平台建立模型,并应用FLUENT软件对平台冷放空泄放气体扩散过程进行了数值模拟研究。研究了可燃气体扩散的基本规律,分析了不同风向、风速、泄放量、冷放空管径、以及泄放口朝向对可燃气体扩散的影响,并将数值模拟结果与规范中的推荐值作了比较,并依据计算结果对冷放空管的设计提出了建议。     

二氧化碳在原油中的分子扩散系数和溶解度研究

为了满足CO2驱油施工设计和油藏模拟的需要,建立了一套完整的测量气体溶解度和扩散系数的实验装置.导出了包含这两个参数的气体压力～时间线性关系式.采用压力降落法在50℃、70℃、105℃温度和静态条件下,测定CO2-吉林红岗原油体系的压力随时间的变化,对所得曲线进行线性拟合,求得了实验条件下CO2在吉林红岗原油中的溶解度和扩散系数.讨论了平衡压力,压力、温度对溶解度和扩散系数的影响,得到了每一实验温度下溶解度～平衡压力、扩散系数～平衡压力线性拟合关系式.在105℃温度下,静态条件下的扩散系数值在10-7m2/s数量级,而动态条件下(转速600r/min)则增至10-6m2/s.     

岩石中烃类气体扩散系数测定技术细节浅析

烃类气体的扩散系数是衡量气体扩散能力的重要物理量,是盖层评价的基本参数之一。国内实验室测定扩散系数一般采用间接方法,即实验测定一定时间内通过样品的扩散量或浓度,再由这些实测值求得扩散系数。但不同的操作流程和实验方法会造成结果的差异。对比实验表明,扩散系数测定误差主要出现在取气时间、取气方式、取值个数和取气位置这四个方面。掌握这些技术细节,有助于提高实验数据的准确性,对盖层封闭能力评价及天然气资源量的估算具有重要意义。     

电化学渗透技术对304不锈钢中氢扩散的研究

运用电化学渗透技术研究了不同充氢电流密度下304不锈钢的氢扩散现象。结果表明,随着阴极充氢电流密度的增大,阳极饱和电流密度增大,进入试样内的氢含量也愈大,而氢的表观扩散系数略有减小。其原因是表面氢含量增加,氢原子之间存在交互作用,从而阻碍了氢的扩散。通过测定充氢-放氢渗氢曲线,得到了该试样的不可逆陷阱密度。     

松辽盆地北部深层天然气的阶梯式扩散机制

松辽盆地徐家围子断陷深层存在多套气源岩,这些地层既可以作为天然气的储层,又对下伏地层的天然气具有一定的封盖能力。针对研究区的地质特点,建立了天然气的阶梯式扩散模型,其基本原理是,每一气源岩层向上扩散损失的天然气,可以直接作为一种天然气的来源提供给上覆地层。把阶梯式扩散模型加入盆地模拟系统中,可以动态地恢复天然气扩散的历史过程。天然气扩散量计算结果表明,在阶梯式扩散模型中,地层中天然气的扩散量与盖层的厚度基本无关,然而扩散速度却直接受盖层孔隙水中的气态烃含量影响,即气源岩作盖层时,对下伏气藏中的天然气向上扩散具有明显的抑制作用。     

极限扩散电流技术测定管内强化传质系数

采用极限扩散电流技术(LDCT)测定管内液体传质系数(k),通过使用静态混合器、筛板和不锈钢θ环填料与筛板耦合体等强化元件,考察了不同强化手段对管内k的影响,研究了气液多相体系的传质过程。实验结果表明,LDCT能较好地测定单相和多相体系的k。在液体流量为1.00m3/h的条件下,空直管中的k为2.38×10-2m/s;使用筛板、静态混合器和填料与筛板耦合体时,k分别为3.64×10-2,3.96×10-2,5.90×10-2m/s。由实验测定的k结合传递类比定律可得到液体传热系数。     

氢在加氢反应器筒体钢中的扩散规律

采用电化学渗氢的方法研究了加氢反应器简体钢2.25Cr1Mo中氢的扩散规律。试样的厚度低于3.5mm时随着厚度的增加,扩散系数D值增大;当厚度大于3.5mm后,D值稳定不变。实验测得温度与扩散系数的关系,可用于高温高压下运行的加氢反应器壁氢渗透测量中原子氢浓度分布的计算。     

CO_2在原油中的扩散及引起的沥青质沉积

CO2在原油中扩散和溶解,使得原油体积膨胀和黏度降低的同时,原油组分也发生变化,可能引起沥青质等重有机质沉积,伤害储层,因此需全面评价CO2在原油中的扩散和影响因素以及可能引起的沥青质沉积程度。用压力降落法测定了压力和沥青质含量对CO2在原油中的扩散系数和溶解度的影响。结果表明,随着压力增加,CO2在原油中的扩散系数成线性增加,溶解度先增加后降低。随原油沥青质含量的增加,CO2扩散系数降低,溶解度增加。CO2扩散后的原油沥青质含量大幅降低,最高降幅达94.6%,表明CO2在扩散过程中引起了沥青质的沉积。     

枯草芽孢杆菌的扩散系数

细菌的扩散作用与细菌在位繁殖及微生物驱油数学模型直接相关。针对微生物驱油过程,应用改进的毛细管法,结合细菌群体的通量模型,实验测定了在微生物驱油方面有应用潜力的菌株—枯草芽孢杆菌BacillussubtilisHSO121的扩散系数。该方法是将一根含有缓冲介质的毛细管插入菌悬液腔内,经过一定时间测定扩散进毛细管的细菌个数,进而求出细菌的扩散系数Db。在实验条件下测得枯草芽孢杆菌HSO121在35℃下的扩散系数为1.2×10-6cm2/s,而文献报道的多种细菌的扩散系数值在3.2×10-7~8.3×10-6cm2/s范围。对比细菌扩散与化学物质扩散的异同,发现非能动菌的扩散类似惰性粒子的布朗扩散,而能动菌的扩散主要基于其随机运动能力,布朗运动的影响可以忽略。图1表1参20。     

Prediction of time required for onset of convection in a porous medium saturated with oil and a layer of gas underlying the oil

The onset of convection for a viscous oil confined in a cylindrical porous medium and contacted with a gas to diffuse into it from below is investigated experimentally and theoretically. Two experiments are carried out, both at a specific reservoir temperature and pressure, starting with the medium saturated with the oil and bringing the gas into contact with it from the base. In the first experiment, the setup is arranged horizontally in order to determine the diffusion coefficient of gas in the absence of convection. In the second experiment, the setup is vertical to investigate the onset of convection. The pressure is maintained constant during both experiments and the volume of gas dissolving in oil is measured vs. time. The dissolved gas data obtained from the vertical experiment show a sharp slope change at the onset of convection. The observed onset time is in excellent agreement with the value obtained by means of an instability theory developed in this study.     

喷雾反应器中表面活性剂对制备天然气水合物的影响

天然气水合物作为一种高效、安全的天然气储存和运输的方式,其实用性很大程度上取决于水合物的含气率和气体水合物的生成速率。从理论上分析了在喷雾反应器中表面活性剂的作用机理:表面活性剂的主要作用在于它降低了参与水合物反应的水的表面张力和改变了水合物形态,提高了气体在水中扩散率和传质率,从而加速水合物的生成。实验证明,表面活性剂在降低水溶液表面张力的同时促进了天然气水合物的生成并提高了水合物的储气率。     

Analytical Modeling of Gas Diffusivity Into Oil Through a Film of Water

Abstract

The authors aimed to determine diffusion coefficient of gas in oil when there is a water-blocking film between them. Dealing with this purpose, a new technique based on analytical modeling was developed to measure the diffusivity and solubility of gas into oil and water. The system that was described is solved analytically and numerically. The result of analytical solution is presented as different type curves, which are very simple to use. To generate data, a numerical scheme was employed. The determination of gas diffusivity and solubility emerged from matching concentration data with the type curves.