江苏油田CO2混相驱现场试验研究

对江苏油田富14断块进行的可行性研究结果表明,复杂小断块油藏可以进行经济有效的CO₂混相驱。江苏油田富14断块在保持最低混相压力的状态下,于1998年末开始进行了CO₂—水交替(WAG)的注入试验。进行了6周期的注入试验后,水气比由0.86:1升至2:1。油井见到了明显的增油降水效果,水驱后油层中形成了新的含油富集带。试验区采油速度由0.5%升至1.2%,综合含水率由93.5%降至63.4%。到目前为止,CO₂波及区采收率已提高4%,CO₂利用率为1240m³/t(油)。试验仍在继续进行。富14断块CO₂混相驱的成功为提高复杂小断块油藏采收率和丰富国内三次采油技术提供了重要的依据。     

复杂断块油田CO2驱油动态监测技术应用与分析

CO₂驱油是3次采油提高采收率的一项重要手段,其驱油前后油藏动态监测评价工作十分重要,目前国内外尚未形成一套成熟的CO₂驱油动态监测评价技术系列。苏北盆地溱潼凹陷CS油田Et组油藏开展了CO₂混相驱先导试验工作,通过运用井间示踪、试井、吸水吸气剖面、产液剖面、剩余油饱和度及油气水性质等动态监测技术及相应监测技术的组合,满足了复杂断块低渗透油藏开展CO₂混相驱试验方案的编制、试验参数的优化调整及效果评价的需求。      

低渗小断块小砂体二氧化碳吞吐影响因素研究

低渗小断块油藏资源丰富，然而低渗透油藏由于孔吼细小、渗透率低，常规注水开发不是行之有效的方法。注CO₂可以大幅提高原油采收率，兼顾碳减排与提高采收率，是低渗透小断块改善开发效果的有效方式。胜利油田小断块、小砂体井网不完善，注CO₂驱油难以实施，CO₂吞吐技术通过注入-焖井-生产的方式开发，是一种井网不完善的小断块开发的有效方法。矿场实施CO₂吞吐影响因素较多，需要进一步开展研究。本文通过数值模拟，研究了不同油藏条件下CO₂吞吐效果，为矿场实施CO₂吞吐提供指导     

苏北盆地草舍油田CO_2混相驱替试验与效果分析

苏北盆地草舍油田泰州组油藏为复杂小断块油藏,水驱采收率仅32%。该文通过将CO2混相驱油室内试验和数值模拟结果与矿场试验相结合,进行了开采效果的理论和实际分析与对比。室内试验和数值模拟结果研究表明,采用CO2混相驱可以使该油藏采收率达到47%,比水驱油的方式提高15%。2005年7月至2009年12月,草舍油田泰州组油藏已累计注入CO2气5 842×104m3,增产原油3×104t,提高采收率2%,取得了显著的增产效果。因此,CO2混相驱油是有效的三次采油方法,对复杂断块油藏开展三次采油具有重要借鉴价值。     

CO2注入方式对芳48油藏开发效果的影响

大庆油田芳48断块为特低渗透油藏,对该油藏进行了水驱、CO₂驱、CO₂吞吐、CO₂转水驱、水驱转CO₂驱等开采方式室内物理模拟研究。实验结果表明,该区块水驱见水早、含水率上升快、注水能力低。在上述5种气驱方式中,CO₂吞吐后气驱的累积采收率最高,然后依次为水驱转CO₂驱、气驱、CO₂驱转水驱,CO₂吞吐的累积采收率最低。从累积气油比来看,CO₂吞吐累积气油比最高,其次为CO₂驱,而水驱转气驱、气驱转水驱、吞吐转气驱的累积气油比较低。从气体注入能力来看,气驱的注入能力最高,而水驱转气驱、气驱转水驱的注入能力比较低。考虑开采效果和气体注入能力,芳48特低渗透油藏开采应优先选择CO₂吞吐后气驱,其次为水驱转CO₂驱。     

CO2混相驱注气速率对重力超覆的影响规律

CO₂驱可以改善低渗透油藏的开发效果,并通过置换油气等方式实现CO₂地质埋存,但由于油气密度差的存在,会形成CO₂重力超覆而影响驱油效果。为明确油层厚度较大的低渗油藏中CO₂混相驱条件下注气速率对重力超覆程度的影响规律,分别采用室内物理模拟实验和数值模拟等方法进行研究,并通过建立的数值模型和超覆程度表征方法,系统评价注气速率的影响规律,从而对注入量等参数进行优化。结果表明,混相驱条件下仍存在一定程度的重力分异,且随注气速率的增加,重力超覆程度减弱,混相驱采收率提高,但相比非混相条件,超覆程度较低,通过注气速率优化减弱其影响的效果更为明显。针对给定模型的模拟计算结果表明,当注入量大于10 t/d后超覆程度影响减弱,因此,为保证厚油层CO₂混相驱油效果,在不发生气窜的前提下应适当采用较大的注气速率以减弱重力超覆的影响。研究结果对于CO₂驱油现场试验方案设计和注气参数优化具有一定的指导意义。     

彩9井区西山窑组特高含水油藏CO2混相驱先导试验

目前彩南油田彩9井区西山窑组已进入高含水低产低能阶段,开井率仅为23.0%,即将面临废弃停产。为了提高该井区特高含水油藏产能,降低含水率,利用类比法、油藏工程及数值模拟方法,对彩9井区西山窑组油藏开展CO₂混相驱可行性论证及油藏工程设计,并进行先导试验。结果表明:先导试验区应选择小井距反七点井网的C2576井组,注入层位选择剩余油富集的J₂x₁^2-2小层,合理注入量为0.3倍孔隙体积(地面CO₂注入量为10 500 t),注气速度为30～40 t/d,注采比为1.1~1.2。现场试验证实,该井组累计注入4 529.7 t CO₂后,累计增油达到1 269 t,CO₂换油率达到0.27 t/t,取得了较好的增产效果。该研究可为彩南油田CO₂混相驱扩大试验和全面调整开发提供技术支撑。     

稠油油藏注CO2提高采收率影响因素研究

与稀油注CO₂提高采收率机理不同,CO₂与稠油无法达到混相,因此影响其开发效果的主要因素差别很大,特别是在热化学复合采油过程中,注入的CO₂主要发挥隔热、降黏、增能的作用。为了进一步研究不同因素对稠油油藏注CO₂驱替效果的影响,在稠油样品物性分析的基础上,利用正交实验方法研究了原油黏度、温度、压力和渗透率对稠油油藏注CO₂提高采收率的影响。温度对采收率影响最大,其他因素由大到小依次为:渗透率、压力、油样类型。根据实验结论及认识,综合考虑地层温度、油藏渗透率等因素,在胜利油田开展了稠油油藏注CO₂吞吐提高采收率矿场试验。从矿场实际生产结果来看,油藏温度增加以及油藏渗透率提高,都有利于注CO₂吞吐开发,都能够有效提高油井产量。      

CO2驱开发后期防气窜综合治理方法研究

室内实验得到的 CO₂混相驱油效率往往可达 90% 以上,但现场却难以达到室内实验的驱油效果。 限制采收率提高的主要原因是 CO₂的黏性指进、重力超覆和油层的非均质性等因素对注入 CO₂波及效率 的影响。 针对注 CO₂驱开发后期油藏气窜现象逐渐加重、开发矛盾不断加剧等问题,从开发层系、注采结 构、注入方式以及注入剖面 4 个方面开展了改善 CO₂驱开发效果的研究,并提出了细分层系、高部位注气、 水气交替注入、聚合物调剖及 CO ₂+ 泡沫驱防气窜等技术对策。 现场实施结果显示,油藏整体气油比从 2733.1 m³/m³下降到 63.84 m³/m³,日产油从注气前的 30.72 t 上升到注气后的 81.68 t。 该项防气窜综合治 理技术及经验可为类似油藏注气驱开发方案设计和后期防气窜提供借鉴。     

水驱断块油藏CO-2气顶边水双向驱油封存机理及应用

复杂断块油藏水驱后会形成高部位剩余“阁楼油”及井间剩余油,为此建立了人工CO₂气顶与人工边水组合的双向驱技术,以实现该类油藏的剩余油动用及CO₂封存。首先,建立了模拟水驱“阁楼油”及双向驱过程的物理模型及方法,开展了CO₂驱及不同渗透率条件下双向驱对比实验,明确了双向驱提高采收率及碳封存潜力。然后,基于拟合数值模型,对CO₂和N₂双向驱开展了不同油藏及注入参数的数模研究,分别揭示了双向驱驱油及封存的主要机理,对比了2种气体双向驱的差异。结果表明：双向驱的焖井过程是气顶形成及“阁楼油”置换的必要过程;高含水油藏双向驱可提高采收率20%以上,相比气驱提高8百分点以上,而封存率相比气驱提高15百分点以上;双向驱主要驱油机理为控制油气界面运移,重力分异,气顶膨胀及抽提原油组分,而主要封存机理为控制油气界面运移,重力分异及增压促溶。经矿场试验取得良好效果,研究为水驱断块油藏有效提采提压提供技术手段及参考。     

二氧化碳—原油多相多组分渗流机理研究

二氧化碳与烃类体系的多相多组分渗流机理,对于深入理解实际油田注二氧化碳的驱替特征、提高采收率及地质埋存等都具有非常重要的意义。应用细管和多次接触实验以及包含相间传质的多相多组分CO₂驱油藏数值模拟模型,系统研究了CO₂—原油体系的相变规律以及多组分体系的变相态渗流特征。结果表明,,CO₂能够大量蒸发C₁₁以下的烃组分,甚至能够蒸发C₃₂等重烃组分;CO₂气驱过程是一个蒸发与凝析的混合过程, 混相带出现在气驱前缘附近;温度越高,CH₄和N₂含量越大,最小混相压力越大。     

Flow Properties of CO2/Crude Oil in Miscible Phase Flooding

Abstract

The high-temperature and high-pressure three-dimensional (3D) device is used to study miscible flooding of CO₂ and crude oil. The experiment model is a real sand plate. In oil reservoir condition, there is a large difference between production and injection volume. The complex flowing characteristics of CO₂ flooding in pore media are observed in recovery, water cut, and gas–oil ratio curves. By analyzing the water saturation contour plot measured by a saturation probe, CO₂ and oil can be miscible. The viscosity of miscible liquid and flowing pressure decreases. This is the important mechanism of enhanced oil recovery. When the viscosity of miscible liquid and flowing pressure decreases, miscible CO₂ and oil contacted with water can make a similar three phase. This is the important mechanism of enhanced oil recovery. Based on the conclusion, the main reason for the production and injection difference is that high-density CO₂ would flow into pore media in which water and oil cannot flow.     

Simulation Study of Different Modes of Miscible Carbon Dioxide Flooding

Carbon dioxide flooding has been applied worldwide as a successful enhanced oil recovery. Carbon dioxide flooding may be applied as a continuous injection or as water-alternating-gas (WAG) process. Optimization of the injection mode of carbon dioxide is important for economical field application. This paper focuses on using a fully compositional simulation model for “AEB-3C” sandstone oil reservoir of one of the Western Desert oil fields in Egypt to predict the impact of CO₂ miscible flooding on the reservoir oil recovery and net present value (NPV), to define the best mode of operation that is straight CO₂ injection or water alternating gas (WAG) processes and to show the difference between pure and impure CO₂. Moreover, several sensitivity runs were done on the oil price to show minimum profitable value of oil price when applying such a tertiary method in the subject field.The reservoir under study has been producing under a successful water flooding project since May-2010. The recovery factor by the end of water flooding project is predicted as 32%. CO₂ flooding processes have started by the end of water flooding. A significant increase in the oil recovery factor was noticed due to applying this method; it reached up to 57%. Comparisons between different modes of operations were shown which showed better results when applying WAG process than that with straight CO₂ injection. Moreover; sensitivities were done on the cycle periods in WAG processes and showed increase in the recovery factor with shortening the cycle periods. In addition to a comparison between pure and impure CO₂ which showed very close results.     

X油藏注气混相驱可行性实验研究

针对X底水油藏油井注水后综合含水上升过快的问题,利用HB70/300型高压物性分析仪开展了该区块原油相态特征实验、注气相态特征实验,并运用细管法开展了注CO₂最小混相压力实验。对比分析了CO₂和N₂两种性质气体注入前后原油的相态特征变化,确定了该区块原油注CO₂最小混相压力,为X油藏注气提高采收率可行性提出依据。实验结果表明,X油藏原始地层压力为46.01 MPa,原油饱和压力为11.06 MPa,注N₂后饱和压力上升迅速,在原始地层条件下难以实现混相,表现出典型的非混相特征;注CO₂后饱和压力上升较平缓,细管法测得的最小混相压力为28.03 MPa,说明利用CO₂可实现CO₂的混相驱替,而且最终的驱替效果比较理想。说明该油藏可开展注CO₂混相驱,为进一步的开发方案调整提供了依据和合理的建议。      

Effects of hydrocarbon solvents on simultaneous improvement in displacement and sweep efficiencies during CO2-enhanced oil recovery

The addition of hydrocarbon solvent such as liquefied petroleum gas (LPG) to the CO₂ stream leads to miscible conditions in reservoirs at lower pressures by reducing the minimum miscibility pressure (MMP). Under miscible conditions, improved displacement and vertical sweepout occur simultaneously. The influences of LPG concentration and composition on the displacement and sweep efficiencies during CO₂-LPG enhanced oil recovery (EOR) were investigated. Enhanced displacement efficiency was assessed through oil viscosity reduction and oil saturation change. Moreover, the miscible flooding induced by LPG addition, which resulted in increased solvent viscosity and a lower density difference between the injected fluid and reservoir oil, provided a smaller viscous gravity number, and improved the sweep efficiency, alleviating the impact of solvent gravity override. For CO₂-LPG EOR, oil recovery increased up to 52% as compared with that for CO₂ flooding. The amount of incremental oil recovery with 100% butane in the LPG was 16%, as compared with the 100% propane case. Mitigated gravity override enabled CO₂-LPG EOR to enhance sweep efficiency. Results indicated that the compositional modeling of the EOR process with the addition of LPG provided more accurate prediction on the performance of CO₂-LPG EOR.     

Evaluation of miscible and immiscible CO2 injection in one of the Iranian oil fields

Carbon dioxide (CO₂) flooding is one of the most important methods for enhanced oil recovery (EOR) because it not only increases oil recovery efficiency but also causes a reduction of greenhouse gas emissions. It is a very complex system, involving phase behavior that could increase the recovery of oil by means of swelling, evaporation and decreasing viscosity of the oil. In this study, a reservoir modeling approach was used to evaluate immiscible and miscible CO₂ flooding in a fractured oil field. To reduce simulation time, we grouped fluid components into 10 pseudo-components. The 3-parameter, Peng–Robinson Equation of State (EOS) was used to match PVT experimental data by using the PVTi software. A one-dimensional slim-tube model was defined using ECLIPSE 300 software to determine the minimum miscibility pressure (MMP) for injection of CO₂. We used FloGrid software for making a reservoir static model and the reservoir model was calibrated using manual and assisted history matching methods. Then various scenarios of natural depletion, immiscible and miscible CO₂ injection have been simulated by ECLIPSE 300 software and then the simulation results of scenarios have been compared. Investigation of simulation results shows that the oil recovery factor in miscible CO₂ injection scenario is more than other methods.     

低渗透油藏二氧化碳混相驱油机理数值模拟

二氧化碳混相驱是大幅提高油藏采收率的重要增产措施,但目前对二氧化碳驱油机理的研究多停留于室内实验阶段,对其混相驱油机理和影响因素缺乏全面系统的认识,因此,采用油藏数值模拟研究方法,以大情字油田黑59井区低渗透油藏为例,对二氧化碳混相驱油机理和影响因素进行了系统研究,对比了注水和注二氧化碳开发的效果。结果表明,注二氧化碳提高采收率的驱油机理是,二氧化碳溶于油相中增加了油藏流度,其与油相组分交换达混相,从而达到提高驱油效率的目的。注二氧化碳开发单井产油量可达注水开发的2倍以上,最终采收率提高14%以上,为研究区及同类低渗透油藏注二氧化碳混相驱开发提供了理论指导,为现场方案的实施提供了重要依据。在吉林大情字油田黑59井区实施混相驱方案后,初期平均单井产油量达10.2 t/d,是注水开发最高产油量的2.4倍,含水率下降了23.2%,与理论研究结果一致。     

A laboratory investigation of carbon dioxide-enhanced oil recovery by focusing on CO2-oil physical properties

Carbon dioxide (CO₂) miscible flooding has become an important method in enhanced oil recovery (EOR) for recovering residual oil. In addition it may help in protection of the environment as (CO₂) is widely viewed as an important agent in global warming. Knowledge of the interactions between (CO₂) and reservoir crude oil is very critical for any (CO₂)-enhanced oil recovery (EOR) projects. This paper shows the effect of (CO₂) miscible flooding application for Egyptian oil fields by swelling studies. The swelling test is a laboratory simulation of the process of injecting gradually different percentage of (CO₂) gas into a reservoir containing under-saturated oil. The gas (injection solvent) can dissolve, causing the reservoir fluid to swell. This paper presents a summary of a wide range of laboratory tests conducted on ten different crude oils varying from 26.4 to 40.5 API. These were used to invested the use of (CO₂) and its effect on parameters such as viscosity, density, gas solubility and swelling factor as a function of pressure at temperature from 620.3 to 706.0?°R.