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.     

测量天然气在稠油中扩散系数的新方法

可靠的扩散系数测量方法对于稠油开发中气体注入方案设计、页岩气开发中流动机理研究和天然气成藏保存过程中气体运移方式的确定等都具有重要的意义。为此,提出了一种基于压力脉冲技术在稠油中测量扩散系数的新方法。首先通过压力脉冲实验来记录PVT容器空腔内的甲烷气体向稠油扩散过程中的压力变化,然后根据Fick第二定律和油气界面的动态边界条件建立数学模型,利用模型所得到的解析解对实验数据进行拟合得到相应的扩散系数。通过对数学模型的分析可以发现:在任一时刻空腔内还未流入油相中的气体物质的量与扩散达到平衡时流入油相中总的物质的量的比值,在时间较长时与无因次时间呈线性关系;与其他文献进行比较的结果表明,所建立方法的测量结果合理,并可推测出扩散系数随油相黏度的增加而逐渐减小;动态边界数学扩散模型符合实际气体扩散的物理过程,能准确地测量气体在稠油等有机质中扩散系数的大小。同时,所得到的新扩散系数测量方法还具有实验简便、操作简单、不用分析油相组分的优点。     

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 coefficients of natural gas in foamy oil systemsunder high pressures

The diffusion coefficient of natural gas in foamy oil is one of the key parameters to evaluate the feasibility of gas injection for enhanced oil recovery in foamy oil reservoirs.In this paper,a PVT cell was used to measure diffusion coefficients of natural gas in Venezuela foamy oil at high pressures,and a new method for determining the diffusion coefficient in the foamy oil was developed on the basis of experimental data.The effects of pressure and the types of the liquid phase on the diffusion coefficient of the natural gas were discussed.The results indicate that the diffusion coefficients of natural gas in foamy oil,saturated oil,and dead oil increase linearly with increasing pressure.The diffusion coefficient of natural gas in the foamy oil at 20 MPa was 2.93 times larger than that at 8.65 MPa.The diffusion coefficient of the natural gas in dead oil was 3.02 and 4.02 times than that of the natural gas in saturated oil and foamy oil when the pressure was20 MPa.However,the gas content of foamy oil was 16.9times higher than that of dead oil when the dissolution time and pressure were 20 MPa and 35.22 h,respectively.     

催化降粘剂作用下河南稠油族组成变化研究

通过棒色谱、气相色谱、红外光谱等分析方法,对反应前后河南稠油族组成及其结构进行了测试,研究了水热催化裂解降粘剂作用下稠油的性能变化,实验表明稠油在水热裂解催化降粘剂作用下重质组分发生加氢裂解反应,胶质、沥青质减少,饱和烃、芳烃等轻质组分增加明显,稠油物性明显改善,为稠油催化降粘开采提供了依据。     

胜利油田注空气提高采收率数模研究

根据胜利油田轻质油样的室内氧化实验,通过拟合动态氧化实验产出的O2与CO2含量,建立其低温氧化(LTO)动力学模型,并结合组分模型、PVT模型及相渗模型,研究低渗透油藏注空气低温氧化工艺的数值模拟方法;以胜利渤南油田罗36块为例,初步评价了油藏参数、开发参数及工艺参数等因素对注空气驱油效果的影响,同时分析了注空气提高采收率机理,并对比注空气与氮气工艺的驱油效果及经济可行性,对注空气开发矿场试验具有一定指导作用。结果表明,实验模拟与实际气体含量拟合较好,从而确定动力学参数;油藏初始温度、初始含油饱和度等是影响注空气效果的重要参数,而油藏倾角、网格大小、射孔位置等对采收率也有影响;注空气相对于氮气而言成本低,驱油效果好。     

Field scale applicability and efficiency analysis of Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR) method for heavy oil recovery

Heavy oil recovery from fractured carbonates is a real challenge, yet no proven technology exists as an efficient solution. Reservoir heating is generally inevitable and steam injection is the only effective way to heat heavy-matrix oil in such reservoirs using the steam distributed through fracture network. We propose a new method minimizing heat needed for efficient heavy oil recovery from oil-wet fractured rocks by adding solvent component. Efficiency is a critical issue in this process due to potentially high cost of the process.A new technique we proposed previously called Steam-Over-Solvent in Fractured Reservoirs (SOS-FR) consists of a cyclic injection of steam and solvent in the following manner: Phase-1: Steam injection to heat up the matrix and recover oil mainly by thermal expansion, Phase-2: Solvent injection to produce matrix oil through diffusion–imbibition-drainage processes, and Phase-3: Steam injection to retrieve the injected solvent and recover more heavy oil. Laboratory scale static and dynamic experiments had shown that, under very unfavorable conditions (oil-wet matrix, 4000cp crude), oil recovery at the end of Phase-3 was around 85–90% OOIP with 80–85% solvent retrieval (Al-Bahlani and Babadagli, 2008, 2009a).In this paper, the experimental results obtained earlier were matched to a single matrix/single fracture numerical model and parameters needed for field scale simulation (matrix-fracture thermal diffusion, solvent diffusion and dispersion coefficients) were obtained (Al-Bahlani and Babadagli, 2009b). Using the data obtained through matching, field scale simulations were performed for efficiency analysis and to identify the optimal injection schemes (soaking time for cyclic and injection rate for continuous injection) and durations, and surface steam quality. Specific conclusions as to how to apply this technique efficiently in the field considering the cost of the process were reported.     

An accurate model to predict viscosity of heavy oils

The viscosity of heavy oils is a crucial factor in estimating oil recovery. Viscosity plays a vital character in reservoir simulations as well as in estimating the easiness of fluid flow, estimating oil recovery, and choosing a production model. The authors present a new intelligent model, a GA-LSSVM, used for predicting the viscosity of heavy oils. The experimental data employed in this work are the product of searching in many heavy oils data gathered from the literature. Development of robust predictive models to predict the viscosity of heavy oils is of immense help in many process engineering applications. The outcomes revealed that GA-LSSVM is able to capture the complicated and nonlinear relation between the input and output variables. GA-LSSVM model resulted in R² and mean absolute error values of 0.9999 and 0.9924, respectively.     

重质原油采油工艺的设想——原油改质热注采

以改质含蜡原油获得轻质油源的技术为基础，结合对目前重质油开采工艺的分析，提出了原油改持热注采重质油的新工艺。与原油相比，分子筛改质原油粘度、凝点大大减小，油温一般在３００－４００℃，将其直接注入重质支，依靠注入介质的稀释作用和热力作用进行开采。依据对采油机理和目前采油工艺的分析，其优点是：采油效果好，注入介质需要分离，改善了产品品质并给后续的油生产带来利益，因此应用前景良好。     

泡沫油油藏冷采后期注气吞吐开采实验

以脱气原油与活油为参照,利用非常规PVT实验方法开展了泡沫油溶气特性实验,揭示了泡沫油溶气特性,明确了天然气在泡沫油中的溶解能力以及地层压力对其溶解的影响规律,并通过岩心驱替实验研究了天然气吞吐提高采收率的可行性以及注气时机、注气轮次对泡沫油天然气吞吐开发效果的影响。泡沫油溶气特性实验表明,天然气溶解过程分为快速溶解、波动下降和稳定3个阶段。注气前期天然气溶解速度较大,累积溶气量增加迅速;天然气溶解能力随深度的增加逐渐减小,垂向上可形成一定的混相区域;增大地层压力有利于增加天然气溶解速度和累积溶气量;各压力下泡沫油溶气能力小于活油及脱气原油,但同一深度处其含气量最多,黏度最小。泡沫油天然气吞吐实验表明,天然气吞吐比冷采开发提高采收率7.8%,注气时机应在泡点压力与拟泡点压力之间,且焖井时间不宜过长,并应最大限度地提高地层压力。     

二连盆地重质稠油藏成因及地化特征

二连盆地重质稠油藏的形成和分布受断陷结构、构造发育史、地层水系统、生油岩成熟度及油气运移史等多种因素控制.研究发现,二连盆地存在两种成因稠油:原生稠油和次生生物降解稠油;它们的形成机理和地质地化特征不同.原油的地化分析表明,蒙古林稠油藏为原生重质稠油藏;而吉尔嘎朗图凹陷西南斜坡区重质稠油藏是轻度-中度降解的低熟重质稠油藏,其产层物性与含油饱和度分析发现,它们是“先成藏后稠化”形成的.     

稠油油藏热采动态监测技术

稠油热采动态监测技术能提供热采过程中的各种动态参数，监测注汽质量，以确定下一步工艺措施或进行热采方案调整。该技术是利用各种专用解释软件，将井下仪器所测得的原始资料进行转换，直观地显示温度、压力、流量、干度、热损失、吸汽量等参数，定性、定量地了解各油层的吸气状况，判断注汽效果。辽河油田热采动态监测已形成配套技术，在稠油生产中发挥了重要作用，现已在现场应用600多井次，均取得了合格资料，效果良好。     

Heavy oil component characterization with multidimensional unilateral NMR

Heavy oil is a complicated mixture and a potential resource and has attracted much attention since the end of last century. It is important to characterize the composition of heavy oil to enhance its recovery efficiency. A designed unilateral Nuclear Magnetic Resonance (NMR) sensor with a Larmor frequency of 20 MHz and a well-defined constant gradient of 23.25 T/m was employed to acquire three-dimensional (3D) data for three heavy oil samples. The highly-constant gradient is advantageous for diffusion coefficient measurement of heavy oil. A fast data-implementation procedure including specially designed 3D pulse sequence and Inversion Laplace Transform (ILT) algorithm was adopted to process the data and extract 3D T1-D-T2 probability function. It indicates that NMR relaxometry and diffusometry are useful to characterize the components of heavy oil samples. NMR results were compared with independent measurements of fractionation and gas chromatography analysis.     

The Effects of Initial Gas Content of the Oil on Recovery by Natural Gas Flood

Effects of initial gas content in oil (IGC) on oil properties and interactions between oil and natural gas were firstly studied by measurements of oil viscosity, interfacial tension (IFT) between oil and gas, and continual dissolution capacity (CDC) of natural gas in oil, which were the main factors affecting oil recovery. Secondly, core flood tests using the oils with different IGC were conducted, so that effects of IGC on oil recovery could be known. Finally, reasons why IGC could influence oil recovery were mechanistically analyzed according to the breakthrough data of natural gas. The results show that, with increased IGC, oil viscosity decreased linearly and IFT was also reduced, but the CDC of natural gas in oil was weakened. Oil recovery of natural gas flood decreased obviously with increased IGC, which is mainly due to the getting-earlier breakthrough of natural gas resulting from the reduced CDC of natural gas in oil and the consequently weakened capacity of oil to dissolve the fingering gas. So for the light oils that are similar to the experimental samples, the lower the IGC was, the higher the oil recovery of natural gas flood was.     

Gas Chromatographic Analysis of Crude Oils with Thermal Extraction Sampling

A novel experimental technique has been developed for the gas chromatographic (GC) analysis of crude oils. The injection of the samples is carried out using a thermal extraction device, directly connected to the GC. Crude oil samples are initially adsorbed on a suitable material and subsequently their light components are thermally extracted and driven into the GC by the carrier gas flow, while the heavy end remains adsorbed on the sample probe. Factors affecting the depth of the analysis, such as the kind of adsorbent material, temperature, and duration of sampling, were studied. The main advantage of the proposed technique is that no preliminary separation of the crude oil sample into a light and heavy fraction is needed prior to the GC analysis. In addition, the contamination of the chromatographic system by the heavy crude oil components is avoided.     

多孔介质高温高压多组分气体-原油分子扩散系数研究

目前气体-原油分子扩散系数的研究对象多为单组分气体-原油体系,而且多在低温或者低压下在 PVT 筒中进行实验,与实际的注气过程相差较大。在这种情况下,研究了多孔介质中高温高压下多组分气 体-原油的扩散系数,测试了全直径岩心中多组分气体-凝析油、多组分气体-重质原油在60 ℃,20 MPa 条 件下的扩散系数。研究结果表明：原油组分对扩散有一定影响,但对于最终扩散程度影响不大;气体在凝析 油中的扩散系数高于其在重质原油中的扩散系数;扩散系数以幂函数形式逐渐增加,最终逐渐趋于平缓。     

天然气扩散系数的实验研究

在分析天然气扩散系数测定原理的基础上,作者自行组装了可控温型天然气扩散系数测定仪,可以测定高温、高压条件下岩石的天然气扩散系数,并能较好地模拟地层条件.利用该仪器分别测定了天然气通过13块人造石英粉砂岩干岩样和饱和水岩样的天然气扩散系数,并应用费克定律的积分式及气体范德华方程确定了对实测天然气扩散系数进行饱和介质条件转换的转换系数为6.06.利用斯托克斯·爱因斯坦方程对实测天然气扩散系数进行了温度校正.校正后地层条件下的天然气扩散系数均小于实测天然气扩散系数,且随着埋深增加,二者之间的差值逐渐减小.这是因为随着埋深增加、地温升高天然气分子运动速度加快的缘故,表明这一校正结果是符合地层条件的.      

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.     

多组分气-气扩散系数的计算

凝析气藏在注气的过程中会出现注入气、注入气与凝析气的混合带和凝析气３个明显不同的段塞,在混合带中注入气会与凝析气发生分子扩散。目前,众多学者已经进行了很多注入气与原油的扩散实验,也计算了相关的多组分物系扩散系数,但计算过程非常复杂,求得扩散系数的时间也较长。为此,通过研究多组分分子扩散系数,分析Maxwell-Stefan扩散系数和Fick扩散系数之间的相互关系,计算了凝析气藏注气混相带中气-气扩散系数。计算结果表明：与二元物系扩散系数相比,多组分分子扩散系数的计算更加的复杂,Maxwell-Stefan扩散系数与Fick扩散系数计算的结果近似相等;Fick扩散系数受分子间相互作用力和热力学非理想性两种因素的影响,其计算与研究较不方便,通常可以用Maxwell-Stefan扩散系数进行近似代替。上述研究成果对凝析气藏的注气开发具有指导意义。