Heavy oil and bitumen recovery by hot solvent injection

Thermal and miscible methods are commonly used for in situ recovery of heavy oil and bitumen. Both techniques have their own limitations and benefits. However, these methods can be combined by co-injecting solvent with steam or injecting solvent into a pre-heated reservoir. The current work was undertaken to study the performance of solvents at higher temperatures for heavy oil/bitumen recovery. Glass bead packs and Berea sandstone cores were used in the experiments to represent different types of pore structures, porosity and permeability. After saturating with heavy oil, the samples were exposed to the vapor of paraffinic solvents (propane and butane) at a temperature above the boiling point of the solvent, and a constant pressure of 1500 kPa. A mechanical convection oven was used to maintain constant temperature across the setup. The setup was designed in such a way that a reasonably long sample (up to 30 cm) can be tested to analyze the gravity effect. The oil recovered from each of these experiments was collected using a specifically designed collection system and analyzed for composition, viscosity and asphaltene content.The final amount of oil recovered in each case (recovery factor but not extraction rate) was also analyzed and the quantity and nature of asphaltene precipitated with each of the tested solvents under the prevailing temperature and pressure of the experiment was reported. Optimal conditions for each solvent type were identified for the highest ultimate recovery. It was observed that recovery decreased with increasing temperature and pressure of the system for both solvents, and that the best results were found when experimental temperature is only slightly higher than the saturation temperature of the solvent used. It was also noticed that butane diluted the oil more than propane which resulted in lower asphaltene content and viscosity of oil produced with butane as a solvent.     

超稠油注气次生泡沫油生成机理及渗流特征

为探索泡沫油在超稠油油藏中的形成机理、渗流特征及驱油效果，采用准噶尔盆地西北缘乌夏断裂带侏罗系齐古组原油及油藏参数，进行注气形成泡沫油介质筛选及原油泡点压力测定实验，并开展注气微观可视化和填砂管驱油实验，深入解析注气形成泡沫油过程中的渗流特征，评价了注气泡沫油驱油效果。研究结果表明：①准噶尔盆地西北缘乌夏断裂带侏罗系齐古组原油泡点压力为9.7 MPa，拟泡点压力随着注气量的增加而增加，随温度的上升而上升，50℃的拟泡点压力随着CO₂注入量的增加而增大，压力上升速度较缓，储层具有较好的注气特性。②研究区的泡沫油渗流可分为5个阶段：无气泡阶段、气泡析出阶段、气泡扩张阶段、气泡聚并阶段和气泡消亡阶段。③研究区蒸汽+CO₂方式驱油开采过程较纯蒸汽填砂管驱的采收率可提升13.3%，开采过程中随着压力的释放，气泡数目逐渐增多，产油量逐步缓慢上升；当压力降至泡点压力后，气泡数目趋于平稳，形成较稳定的泡沫油，产油量大幅提升，为主力产油期；当压力释放至拟泡点压力后，气泡数目迅速下降，泡沫油逐渐消亡，产油量缓慢下降。     

稠油环空掺稀气举技术——以吐哈油田吐玉克区块为例

为了提高稠油冷采开发水平,利用高18.25 m的垂直多相管流实验回路开展了稠油气举流动实验及压降模型优选。基于实验结果及井筒传热机理,建立了环空掺稀气举井筒压力-温度梯度耦合预测模型,并可通过耦合环空与油管内流动进行循环迭代求解。实验结果表明:注气有助于稠油与稀油更快更充分混合;压降模型优选表明,Ansari模型误差相对最小,为12.12% 。针对吐哈油田吐玉克区块稠油井筒举升困难的实际情况,提出了稠油环空掺稀+气举工艺思路,并开展了实例井掺稀气举设计,对注气量、掺稀量等进行了敏感性分析。实例设计结果表明,实例井仅靠气举无法生产,其 掺稀生产极限产量可达到16 m³/d,而掺稀+气举极限产量能达到52.5 m³/d;定产油量条件下,在特定范围内增加注气量能极大地减小掺稀量,且井底掺稀气举能极大地提升稠油井的产能。     

The mechanism of the oxidation of light oil

High pressure air injection (HPAI) has been proven as an enhanced oil recovery process in many fields. The reactions associated with crude oil and oxygen are the main difference between HPAI and other gas injection processes. In order to study the reaction schemes, different experiments, such as the combustion tube, kinetic cell, accelerating rate calorimeter, and thermogravimetry analysis, are conducted. In this paper, a reaction scheme is build that includes three classes of reactions: low-temperature oxidation, cracking, and combustion. We then use simulation models with the proposed reaction scheme included to history match the data from a combustion tube experiment and a kinetic cell experiment. It is demonstrated that the reaction scheme is valid. Based on this study, lumping the crude oil into four pseudocomponents brings a good matching result, and the kinetic parameters are obtained through matching the experimental results.     

Marangoni对流启动残余油微观机理

Marangoni对流可以有效地剥离油膜、乳化油滴的现象已经引起关注,研究Marangoni对流启动残余油的机理对提高石油采收率有着重大意义。在此背景下,选用了能产生Marangoni对流的季铵盐和OP7两种表面活性剂,设计了微观膜状残余油和喉道残余油启动实验,分别对比了强和弱Marangoni对流启动残余油的现象并分析了机理。结果表明:油膜在Marangoni对流引发的界面扰动作用下拉伸聚集成小油滴,同时界面扰动与浮力做功之和超过了油的黏附功,油膜收缩成油滴后从表面脱离。Marangoni对流产生的界面扰动在低界面张力条件下使喉道处的残余油自发乳化为粒径小于喉道尺寸的小油滴,使滞留油滴能够克服贾敏效应所产生的毛细管压差顺利通过喉道。Marangoni对流对启动残余油有着重要作用。     

Gas and oil production from waterflood residual oil: effects of wettability and oil spreading characteristics

In the depressurisation of reservoirs already produced to waterflooded residual oil, solution gas is released when the reservoir pressure drops to below the bubble point. This gas becomes mobilised when the critical gas saturation has been reached. Additionally, the oil itself can become mobile from its residual state and can also be produced under suitable physical conditions. The critical gas saturation, the rate of saturation change, and the gas saturation remaining at the end of the depressurisation process (unrecoverable gas) are important parameters in determining the overall economic performance when depressurising a reservoir.In this, and previous work, we are demonstrating that these quantities depend additionally upon other factors which affect the fluid distribution and the rate of gas generation, particularly the surface and interfacial properties. For instance, earlier visual experiments in glass micromodels suggested that wettability and oil spreading coefficient could substantially influence both the value of the critical gas saturation and the growth pattern for the developing gas bubbles, and thus the gas flow. In order to confirm these observations and to provide quantitative data, further experiments in large sintered packs, with different matrix wettability and with oils having different spreading coefficients (e.g. oil spreading onto a gas–water interface), have been carried out and are reported here. These new experiments show that the magnitude of the critical gas saturation for a water-wet system is about the same irrespective of whether the oil is spreading or non-spreading, but it is much higher than for the oil-wet case. In addition, oil is also produced but the rate of production is dependent upon the rock wettability and the oil characteristics. We find that in a water-wet medium, for spreading oils, the physical form of the oil becomes transformed from being immobile ganglia into mobile oil films, which can then be transported by the gas. For non-spreading oils, oil has to be pushed out by the gas as discontinuous ganglia so less is oil produced. In contrast, in an oil-wet system, the oil phase already exists as a continuous film on the surface of the solid so that the generation of gas effectively expands the oil phase, enabling the oil to be produced in larger quantities even at lower gas saturations.These new experiments give further evidence that rock wettability has an important influence on the performance of gas production from residual oil. Additionally, significant amounts of oil may be recovered after waterflooding from the residual condition, which could have a beneficial impact on the economics of the depressurisation.     

Determination of gas dispersion in vapor extraction of heavy oil and bitumen

In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier.     

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。     

油页岩原位注蒸汽开采油气中试与多模式原位热采技术的适用性分析

油页岩是中国储量巨大的重要战略资源,也是国际公认的重要非常规石油资源。对油页岩进行地下原位干馏是目前实现其大规模工业开发的唯一可行技术方案。太原理工大学于2010年获得油页岩原位注蒸汽开采油气技术（MTI）的发明专利授权。基于MTI技术原理,对大尺寸油页岩试件实施原位注蒸汽开采油气的中试实验,并对多模式油页岩原位干馏技术的适用性进行分析。研究结果表明：①在实施油页岩原位多井水力压裂连通过程中,最高注水压力仅为地应力的41%,裂缝起裂扩展压力低。②蒸汽对流传热方式具备很高的传热效率,有机质热解迅速,蒸汽携带油气快速从生产井产出。同时,通过选择开启或关闭井组钻孔阀门的方式,实时调整蒸汽的流量和流向,灵活控制油页岩目标加热热解区域,实现了蒸汽的科学调配。③在油页岩原位注蒸汽正常运行过程中,蒸汽的注入压力仅约为自重应力的1/4,蒸汽锅炉长期低负载运行。④油页岩原位热解引发的地面沉降量很小,对地质环境危害小。⑤注汽热解区采出的含油率高达95%以上,总体原油采收率达到67.3%,充分证明利用MTI技术原位注蒸汽热解油页岩可达到较高的原油采收率。⑥所得油页岩油中轻质油品的占比达到72.51%;H₂在热解气体中的比例占据绝对优势,体积含量高达68.87%。⑦注蒸汽热解区的顶、底板油页岩层热解不充分,裂隙发育不明显,成为良好的防渗隔热层。⑧MTI技术与其他油页岩原位热采技术相比,其在技术流程和经济性方面具有明显优势,具备广阔的商业开发应用前景。     

注气压力对气驱驱油效率影响的实验研究

通过多组细管实验,研究塔里木油田某区块原油在模拟地层温度108℃下注气压力对气驱驱油效率的影响,分析了不同注入压力下气驱驱油效率和气体突破的影响。实验结果证实：随着注气压力、注气体积增加,气驱驱油效率增加且增幅较大,表明提高注气压力可以显著提高驱油效率;且CO2与原油间最小混相压力为35．1MPa。注气压力越大,气体与原油混相程度越高,气驱越接近活塞式驱替,气体突破时间越长。     

气润湿反转提高采收率实验研究

注气开采是三次采油的一种重要开发方式,在气驱水的过程中,气润湿反转可以使毛细管压力由气驱阻力变为动力,从而提高气驱油效率.用N2和CO2做气驱水实验,研究气润湿反转对提高采收率的影响.实验所用岩心为长庆油田的低渗透率岩心,所用气润湿反转剂属阳离子型氟化物.对气润湿反转前后的岩心做气驱水实验,绘出气润湿反转前后水的采出程...     

委内瑞拉MPE-3区块超重油冷采过程中泡沫油开采机理

针对超重油沥青质含量高、原油重度高等特点,研究了水平井溶解气驱冷采的开采机理,包括冷采过程中泡沫油的形成机理、非常规PVT特性与驱替特征。实验结果表明,当油藏压力低于泡点压力时,原油中形成许多微小气泡,这些微小气泡能够长时间滞留在油相中,使得这种原油表现出与常规溶解气驱许多不同的特征;泡沫油的作用与油藏衰竭速度、油层压力下降水平及围压等因素有关。使用水平井冷采技术能够获得较高原油产量和采收率。     

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。     

苏北盆地高邮凹陷油气成藏特征研究

苏北盆地高邮凹陷近几年油气勘探的一系列重要发现，为重新认识凹陷的石油地质特征，总结油气分布特点和油气聚集规律，提供了较为丰富的信息。根据地层压力、泥岩孔隙度及地层水资料、油源对比和已发现的油藏原油物性（包括高压物性）的纵横向变化规律，总结出不同地质环境下的油气运移方式及油气聚集的规律。通过对该区压力封闭层的分布研究得知：压力封闭层对该区油气运移起明显的控制作用，不同的压力封闭模式控制不同的油气分布类型。该地区地层水的变化规律能有效地反映地层保存条件的差异，地面原油物性变化能很好地反映油气运移的方向，运移系数可以反映油气侧向、垂向运移的程度，定量地得出主要运移方式。     

Three-phase flow in water-wet porous media: gas/oil relative permeabilities for various spreading conditions

This paper addresses the impact of oil-on-water spreading energy (which governs the ability of the oil phase to spread on water in the presence of gas) on three-phase gas/oil relative permeabilities and residual oil saturation.Experimental tests, including simultaneous injections of oil and gas in porous media (steady state) as well as displacements of oil by gas (unsteady state) in the presence of connate water, were performed in two different rocks, Fontainebleau and Clashach sandstones.Gas and oil relative permeabilities were calculated directly from the steady-state data or evaluated by history matching of the experimental displacement production curves. The values obtained by the two methods often differ significantly; the relative permeabilities obtained by the steady-state method cannot represent a displacement.Oil recovery and relative permeabilities are higher for spreading than for non-spreading conditions for gas drainage displacements. Gas relative permeabilities at low oil saturations seem to be lower for non-spreading than for spreading conditions due to an important gas blocking effect caused by the oil/gas menisci. In this case, the measured relative permeabilities include a capillary effect.Oil relative permeabilities are compared to theoretical curves derived from an analytical model that takes into account, through the fractal dimension, the surface irregularities of a real porous medium; the model presented in this paper can be used to calculate the relative permeability of the intermediate phase (oil) during gas injection in a porous medium in the presence of water, for low oil saturations where film flow predominates; very good agreement is obtained for spreading conditions.Gas and oil relative permeabilities obtained by fitting the displacement curves for experiments performed with the reservoir rock and fluids under representative conditions may thus be used for prediction or modeling purposes on a reservoir scale.     

同一条断层垂向封闭的差异性分析

在断层静止后垂向封闭机理分析的基础上,对断层垂向封闭的主控因素进行了研究,认为断层面压力、断裂带中泥质含量和是否被SiO2和CaCO3沉淀胶结是影响断层垂向封闭性的主控因素。通过模拟实验和实例对断层垂向封闭的差异性进行了研究,表明由于封闭空间（剖面上和平面上）变化造成同一条断层垂向封闭性在空间（剖面和平面）上存在着差异性,由于封闭条件和机理演化造成同一条断层垂向封闭在时间上存在着差异性,由于封闭对象改变造成同一条断层垂向封闭能力存在着差异性,在相同条件下,同一条断层垂向封油能力强于垂向封气能力。     

油砂SAGD开发后期转火驱数值模拟

当蒸汽辅助重力泄油(SAGD)开发进入平台期末时,日产油量降低,汽油比急剧升高,在蒸汽腔发育的楔形区域存在大量剩余油,造成热量的损失,并降低了开发的经济性。文中提出了SAGD开发后期转火驱的接替方式,基于加拿大某油砂区块储层、流体特征建立数值模拟机理模型,将蒸汽腔波及至油层顶部边缘位置时作为转火驱的开发时机,利用在SAGD井两侧添加的垂直注气井排与原水平生产井分别作为火驱开发的注、采井,对转驱开发进行油藏数值模拟研究。结果表明:转驱开发分为4个阶段,即气驱次生水期、火驱见效期、火驱稳产期以及产量递减期;转驱采出程度达到20.9%,平均空气油比仅为788 m~3/m~3,最终采收率达到82.1%。该研究对于油砂高效开发具有积极的推动作用。     

Experimental and Modelling Investigations of Asphaltene Precipitation During Pressure Depletion and Gas Injection Operations

Asphaltene precipitation problems manifest themselves in different stages of oil reservoirs production. Experimental and modeling investigations are, therefore, employed as promising tools to assist in predictions of asphaltene precipitation problems and selection of proper production facilities. This study concerns experimental and modeling investigations of asphaltene precipitation during natural production and gas injection operations for a heavy Iranian crude oil at reservoir conditions. First, with design and performance of high pressure–high temperature experiments, asphaltene precipitation behavior is comprehensively investigated; the effects of pressure and temperature are fully studied during pressure depletion tests and the role of injection gas composition on precipitation is described in gas injection experiments. In the next stage, the obtained experimental results are fed into a commercial simulator to develop the asphaltene precipitation model. The results for the pressure depletion experiments indicate that the maximum amount of asphaltene precipitation takes place at fluid bubble point pressure. Increase in the temperature, as seen, causes to reduce the amount of precipitation for the entire range of pressures. For gas injection experiments, the onset of precipitation for CO₂, associated, and N₂ gases takes place at around 0.20, 0.28, and 0.50 gas to mixture mole ratios, respectively. Carbon dioxide shows the highest asphaltene precipitation values and nitrogen has the lowest amounts for the whole range of gas mole fractions. Finally, the results for modeling indicate successful asphaltene precipitation predictions for both pressure depletion and gas injection processes.     

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     

稠油溶解气驱泡沫油特征实验研究

压力衰竭速度是影响稠油溶解气驱泡沫油生产的一个关键因素。为定量描述压力衰竭速度对泡沫油现象的影响,实验选取了4组不同压力衰竭速度进行实验。研究不同压力衰竭速度下稠油衰竭开采中的采收率、产油量、生产气油比以及实验压力的变化。通过实验发现稠油溶解气驱过程中出现明显的泡沫油阶段,且压力衰竭速度越大,泡沫油拟泡点压力越小,泡沫油阶段越长。随着压力衰竭速度增加,采收率增加,生产气油比减小,油藏压力递减变慢。