Analysis of pressure response at an observation well against pressure build-up by early stage of CO_(2)geological storage project

To ensure a safe and stable CO_(2)storage,pressure responses at an observation well are expected to be an important and useful field monitoring item to estimate the CO_(2)storage behaviors and the aquifer parameters during and after injecting CO_(2),because it can detect whether the injected CO_(2)leaks to the ground surface or the bottom of the sea.In this study,pressure responses were simulated to present design factors such as well location and pressure transmitter of the observation well.Numerical simulations on the pressure response and the time-delay from pressure build-up after CO_(2)injection were conducted by considering aquifer parameters and distance from the CO_(2)injection well to an observation well.The measurement resolution of a pressure transmitter installed in the observation well was presented based on numerical simulation results of the pressure response against pressure build-up at the injection well and CO_(2)plume front propagations.Furthermore,the pressure response at an observation well was estimated by comparing the numerical simulation results with the curve of CO_(2)saturation and relative permeability.It was also suggested that the analytical solution can be used for the analysis of the pressure response tendency using pressure build-up and dimensionless parameters of hydraulic diffusivity.Thus,a criterion was established for selecting a pressure transducer installed at an observation well to monitor the pressure responses with sufficient accuracy and resolution,considering the distance from the injection well and the pressure build-up at the injection well,for future carbon capture and storage(CCS)projects.

Enhanced gas production and CO_(2) storage in hydrate-bearing sediments via pre-depressurization and rapid CO_(2) injection

Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades.Exploring an efficient CO_(2) storage method can significantly reduce CO_(2) emissions in the short term.In this study,we attempted to construct sediment samples with different residual CH_(4) hydrate amounts and reservoir conditions,and then investigate the potentials of both CO_(2) storage and enhanced CH_(4) recovery in depleted gas hydrate deposits in the permafrost and ocean zones,respectively.The results demonstrate that CO_(2) hydrate formation rate can be significantly improved due to the presence of residual hydrate seeds;However,excessive residual hydrates in turn lead to the decrease in CO_(2) storage efficiency.Affected by the T-P conditions of the reservoir,the storage amount of liquid CO_(2) can reach 8 times that of gaseous CO_(2),and CO_(2) stored in hydrate form reaches 2-4 times.Additionally,we noticed two other advantages of this method.One is that CO_(2) injection can enhance CH_(4) recovery rate and increases CH_(4) recovery by 10%-20%.The second is that hydrate saturation in the reservoir can be restored to 20%-40%,which means that the solid volume of the reservoir avoids serious shrinkage.Obviously,this is crucial for protecting the goaf stability.In summary,this approach is greatly promising for high-efficient CO_(2) storage and safe exploitation of gas hydrate.

A hybrid physics-informed data-driven neural network for CO_(2) storage in depleted shale reservoirs

To reduce CO_(2) emissions in response to global climate change,shale reservoirs could be ideal candidates for long-term carbon geo-sequestration involving multi-scale transport processes.However,most current CO_(2) sequestration models do not adequately consider multiple transport mechanisms.Moreover,the evaluation of CO_(2) storage processes usually involves laborious and time-consuming numerical simulations unsuitable for practical prediction and decision-making.In this paper,an integrated model involving gas diffusion,adsorption,dissolution,slip flow,and Darcy flow is proposed to accurately characterize CO_(2) storage in depleted shale reservoirs,supporting the establishment of a training database.On this basis,a hybrid physics-informed data-driven neural network(HPDNN)is developed as a deep learning surrogate for prediction and inversion.By incorporating multiple sources of scientific knowledge,the HPDNN can be configured with limited simulation resources,significantly accelerating the forward and inversion processes.Furthermore,the HPDNN can more intelligently predict injection performance,precisely perform reservoir parameter inversion,and reasonably evaluate the CO_(2) storage capacity under complicated scenarios.The validation and test results demonstrate that the HPDNN can ensure high accuracy and strong robustness across an extensive applicability range when dealing with field data with multiple noise sources.This study has tremendous potential to replace traditional modeling tools for predicting and making decisions about CO_(2) storage projects in depleted shale reservoirs.

Investigation of gravity influence on EOR and CO_(2) geological storage based on pore-scale simulation

Gravity assistance is a critical factor influencing CO_(2)-Oil mixing and miscible flow during EOR and CO_(2)geological storage.Based on the Navier-Stokes equation,component mass conservation equation,and fluid property-composition relationship,a mathematical model for pore-scale CO_(2) injection in oilsaturated porous media was developed in this study.The model can reflect the effects of gravity assistance,component diffusion,fluid density variation,and velocity change on EOR and CO_(2) storage.For nonhomogeneous porous media,the gravity influence and large density difference help to minimize the velocity difference between the main flow path and the surrounding area,thus improving the oil recovery and CO_(2) storage.Large CO_(2) injection angles and oil-CO_(2) density differences can increase the oil recovery by 22.6% and 4.2%,respectively,and increase CO_(2) storage by 37.9% and 4.7%,respectively.Component diffusion facilitates the transportation of the oil components from the low-velocity region to the main flow path,thereby reducing the oil/CO_(2) concentration difference within the porous media.Component diffusion can increase oil recovery and CO_(2) storage by 5.7% and 6.9%,respectively.In addition,combined with the component diffusion,a low CO_(2) injection rate creates a more uniform spatial distribution of the oil/CO_(2) component,resulting in increases of 9.5% oil recovery and 15.7% CO_(2) storage,respectively.This study provides theoretical support for improving the geological CO_(2) storage and EOR processes.

CO_(2)-EOR过程中油藏储层构造封存能力的模拟

为应对日益严峻的能源危机和温室效应,CO_(2)提高采收率技术脱颖而出,因此CO_(2)提高采收率后的地质封存安全性和相应的封存能力评估引起了广泛关注。借助数值模拟方法,基于吉林油田某区块油藏的实际储层条件,构建了注入CO_(2)含量为10%~90%的9个模型,分别探究了含水饱和度为30%,50%和90%以及储层压力为10 MPa,20 MPa和30 MPa时油藏各相组分的分布规律;基于前人对封存CO_(2)安全储存状态划分的研究,最终明确了CO_(2)的安全封存量。结果表明:1)当含水饱和度(30%)和压力(10 MPa)一定时,增加CO_(2)含量(10%~90%)可大幅提高CO_(2)的有效封存体积分数(26%~93%);2)压力的提升(10~30 MPa)促进了CO_(2)在油相中的溶解,从而略微降低了储层的封存能力(18%~7%);3)含水饱和度对储层封存CO_(2)的能力的影响微乎其微。该研究旨在阐明不同条件下CO_(2)的构造埋存量,为相关研究提供借鉴。

Research on the feasibility of storage and estimation model of storage capacity of CO_(2)in fissures of coal mine old goaf

The concept of the carbon cycle in the old goaf of a coal mine based on CO_(2)utilization and storage was put forward adhering to the principle of low-carbon development,utilization of space resources in old goafs,and associated gas resources development.Firstly,the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test,the sealing performance of the caprocks after stabilization was analyzed,and the fissures were counted and classi-fied.Then,the process of gaseous CO_(2)injection in the connected fissure was simulated by Ansys Fluent software,and the migration law and distribution characteristics of CO_(2)under the condition of gaseous CO_(2)injection were analyzed.Finally,the estimation models of free CO_(2)storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO_(2)injection.The CO_(2)storage capacity in the old goaf of the case coal mine was estimated.The results showed that a caprock group of“hard-thickness low-permeability hard-thickness”was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically.The connected fissure,occlude cracks,and micro-fractures in the goaf accounted for 85.5%,8.5%,and 6%of the total fissures,respectively.Gaseous CO_(2)first migrated to the bottom of the connected fissure after CO_(2)was injected into the goaf,then spread horizontally along the bottom of the connected fissure after reaching the bottom,and finally spread longitudinally after filling the bottom of the entire connected fissure.The theoretical and effective storage capacities of free CO_(2)at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t,respectively.The effective storage capacity of free CO_(2)at normal temperature and pressure in the old goaf after all minefield mined was 193404 t.The research can provide some reference for the coal mining industry to help the goal of“carbon peaking and carbon neutrality”.

An Integrated Framework for Geothermal Energy Storage with CO_(2)Sequestration and Utilization

Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage due to its superior thermal properties.Moreover,the use of CO_(2)plumes for geothermal energy storage mitigates the greenhouse effect by storing CO_(2)in geological bodies.In this work,an integrated framework is proposed for synergistic geothermal energy storage and CO_(2)sequestration and utilization.Within this framework,CO_(2)is first injected into geothermal layers for energy accumulation.The resultant high-energy CO_(2)is then introduced into a target oil reservoir for CO_(2)utilization and geothermal energy storage.As a result,CO_(2)is sequestrated in the geological oil reservoir body.The results show that,as high-energy CO_(2)is injected,the average temperature of the whole target reservoir is greatly increased.With the assistance of geothermal energy,the geological utilization efficiency of CO_(2)is higher,resulting in a 10.1%increase in oil displacement efficiency.According to a storage-potential assessment of the simulated CO_(2)site,110 years after the CO_(2)injection,the utilization efficiency of the geological body will be as high as 91.2%,and the final injection quantity of the CO_(2)in the site will be as high as 9.529×10^(8)t.After 1000 years sequestration,the supercritical phase dominates in CO_(2)sequestration,followed by the liquid phase and then the mineralized phase.In addition,CO_(2)sequestration accounting for dissolution trapping increases significantly due to the presence of residual oil.More importantly,CO_(2)exhibits excellent performance in storing geothermal energy on a large scale;for example,the total energy stored in the studied geological body can provide the yearly energy supply for over 3.5×10^(7) normal households.Application of this integrated approach holds great significance for large-scale geothermal energy storage and the achievement of carbon neutrality.

A CO_(2) storage potential evaluation method for saline aquifers in a petroliferous basin

According to the requirements for large-scale project implementation, a four-scale and three-level CO_(2)storage potential evaluation method is proposed for saline aquifers in a petroliferous basin in China, considering geological,engineering and economic factors. The four scales include basin scale, depression scale, play scale and trap scale, and the three levels include theoretical storage capacity, engineering storage capacity, and economic storage capacity. The theoretical storage capacity can be divided into four trapping mechanisms, i.e. structural & stratigraphic trapping, residual trapping, solubility trapping and mineral trapping, depending upon the geological parameters, reservoir conditions and fluid properties in the basin. The engineering storage capacity is affected by the injectivity, storage security pressure, well number, and injection time.The economic storage capacity mainly considers the carbon pricing yield, drilling investment, and operation cost, based on the break-even principle. Application of the method for saline aquifer in the Gaoyou sag of the Subei Basin reveals that the structural & stratigraphic trapping occupies the largest proportion of the theoretical storage capacity, followed by the solubility trapping and the residual trapping, and the mineral trapping takes the lowest proportion. The engineering storage capacity and the economic storage capacity are significantly lower than the theoretical storage capacity when considering the constrains of injectivity, security and economy, respectively accounting for 21.0% and 17.6% of the latter.

Key Problems and Countermeasures in CO_(2)Flooding and Storage

Based on literature research in combination with the practice of CO_(2)flooding and storage in Jilin Oilfield,this study assesses the key problems in CO_(2)flooding and storage,proposing the corresponding countermeasures from five aspects of CO_(2)gas source condition,namely geological condition evaluation,scheme design incoordination with other production methods,economic and effectiveness evaluation,together with dynamic monitoring and safety evaluation.The results show that CO_(2)flooding is the most economic and effective CO_(2)storage method.In eastern China,inorganic origin CO_(2)gas reservoirs are widely developed and are especially the most enriched in the Paleozoic carbonate rock strata and the Cenozoic Paleogene–Neogene system,which provide a rich resource base for CO_(2)flooding and storage.In the future,CO_(2)generated in the industrial field will become the main gas source of CO_(2)flooding and storage.The evaluation of geological conditions of oil and gas reservoirs is the basis for the potential evaluation,planning scheme design and implementation of CO_(2)flooding and storage.CO_(2)storage should be below the depth of 800 m,the CO_(2)flooding and storage effects in lowpermeability oil reservoirs being the best.CO_(2)geological storage mechanisms primarily consist of tectonic geological storage,bound gas storage,dissolution storage,mineralization storage,hydrodynamic storage and coalbed adsorption storage.The practice of CO_(2)flooding and storage in Jilin Oilfield demonstratesthat the oil increment by CO_(2)flooding is at least 24%higher than by conventional water flooding.The most critical factor determining the success or failure of CO_(2)flooding and storage is economic effectiveness,which needs to be explored from two aspects:the method and technology innovation along with the carbon peaking and carbon neutrality policy support.After CO_(2)is injected into the reservoir,it will react with the reservoir and fluid,the problem of CO_(2)recovery or overflow will occur,so the dynamic monitoring and safety evaluation of CO_(2)flooding and storage are very important.This study is of great significance to the expansion of the application scope of CO_(2)flooding and storage and future scientific planning and deployment.

Effects of Co_(2)O_(3)Addition on Microstructure and Properties of SiC Composite Ceramics for Solar Absorber and Storage

SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.

Effects of CH_(4)/CO_(2) multi-component gas on components and properties of tight oil during CO_(2) utilization and storage: Physical experiment and composition numerical simulation

An essential technology of carbon capture, utilization and storage-enhanced oil recovery (CCUS-EOR) for tight oil reservoirs is CO_(2) huff-puff followed by associated produced gas reinjection. In this paper, the effects of multi-component gas on the properties and components of tight oil are studied. First, the core displacement experiments using the CH_(4)/CO_(2) multi-component gas are conducted to determine the oil displacement efficiency under different CO_(2) and CH_(4) ratios. Then, a viscometer and a liquid density balance are used to investigate the change characteristics of oil viscosity and density after multi-component gas displacement with different CO_(2) and CH_(4) ratios. In addition, a laboratory scale numerical model is established to validate the experimental results. Finally, a composition model of multi-stage fractured horizontal well in tight oil reservoir considering nano-confinement effects is established to investigate the effects of multi-component gas on the components of produced dead oil and formation crude oil. The experimental results show that the oil displacement efficiency of multi-component gas displacement is greater than that of single-component gas displacement. The CH_(4) decreases the viscosity and density of light oil, while CO_(2) decreases the viscosity but increases the density. And the numerical simulation results show that CO_(2) extracts more heavy components from the liquid phase into the vapor phase, while CH_(4) extracts more light components from the liquid phase into the vapor phase during cyclic gas injection. The multi-component gas can extract both the light components and the heavy components from oil, and the balanced production of each component can be achieved by using multi-component gas huff-puff.

三河尖关闭煤矿煤层CO_(2)封存潜力研究

关闭煤矿煤层CO_(2)地质封存是CO_(2)封存的重要方式之一,也是短期内实现碳减排指标的有效手段之一。以江苏省徐州市三河尖关闭煤矿为例,分析了已采7号煤和9号煤的煤岩煤质特征,统计了剩余煤炭资源储量,运用模糊综合评价法,选取了稳定系数、上覆岩层性质、地质构造复杂程度、地下水指标、封存煤层压温比、封存煤层深厚比、封存煤层渗透率、采空塌陷程度和其他因素等9个主要影响因素指标对7号煤和9号煤封存CO_(2)稳定性进行评价,建立关闭煤矿煤层CO_(2)封存评价方法并评估CO_(2)封存潜力。结果表明,三河尖关闭煤矿7号煤和9号煤剩余储量较大,CO_(2)封存稳定性综合评价结果分别为86.209和87.698,评价等级均为较稳定,封存潜力较高。根据建立的关闭煤矿煤层CO_(2)封存评价方法,计算获得三河尖关闭煤矿7号和9号煤层CO_(2)理论封存量分别为207.6 Mt和80.9 Mt,并据此划分封存有利区为有利区、较有利区和不利区3个等级。研究可为关闭煤矿煤层CO_(2)封存研究提供基础依据。

海洋CO_(2)地质封存研究进展与发展趋势

CO_(2)捕集、利用和封存是中国实现“双碳”目标的核心技术,也是全球研究的热点。CO_(2)地质封存是其中的关键环节,特别是海洋CO_(2)地质封存是今后的重点发展方向。以国内外海洋CO_(2)地质封存的发展历程为基础,结合典型CO_(2)海洋封存示范项目案例,系统梳理了国内外海洋CO_(2)地质封存理论研究进展,分析了CO_(2)在井筒流动、相变与传热、CO_(2)流体运移与储层物性参数展布规律、海洋地质封存机制及封存潜力、地质封存盖层完整性及安全性评估等方面的研究现状。认识到中国目前对海底地质结构中CO_(2)注入过程的多相态转化、溶解、捕获传质特征及动力学特性认识尚浅,对海洋封存机制及不同封存机制之间的相互作用机理尚不明确,未来应开展海洋CO_(2)动态地质封存空间重构机制研究,解决地质封存相态转化及流体动态迁移机理等关键科学问题,揭示海洋CO_(2)地质封存机制的相互作用机理,形成适用于中国海洋地质封存CO_(2)高效注入和增效封存方法。

纳米SiO_(2)强化CO_(2)地质封存页岩盖层封堵能力机制试验

页岩为CO_(2)盐水层地质封存常见盖层岩石类型,强化盖层封堵能力有利于提高CO_(2)地质埋存量和安全性。为探究随CO_(2)混注纳米SiO_(2)(SNPs)强化盖层封堵能力的有效性和可行性,对CO_(2)地质封存页岩盖层样品开展原地条件下的超临界CO_(2)酸蚀反应试验,基础组为页岩样品-地层水、对照组为页岩样品-地层水+超临界CO_(2)、优化组为页岩样品-地层水+SNPs+超临界CO_(2),并采用核磁共振测试、场发射扫描电镜可视化观测、X射线衍射测试和岩石力学试验,探究CO_(2)酸蚀反应前后的页岩孔隙结构、表面形貌、矿物成分及力学性质特征。结果表明:优化组的大孔孔隙分量及孔隙度和渗透率增大幅度低于对照组;与对照组相比,优化组黏土矿物与碳酸盐岩矿物相对含量损失少,表明随CO_(2)混注SNPs可使岩样内部酸蚀作用减弱;SNPs在岩石端面吸附聚集或进入岩心孔喉,可使优化组页岩样品力学性能损伤程度降低;随CO_(2)混注SNPs有利于强化CO_(2)盐水层地质封存盖层封堵能力。

CO_(2)−荷载耦合作用下煤体细观统计损伤本构模型及验证

CO_(2)吸附会对煤体产生损伤劣化作用进而降低其稳定性,对CO_(2)封存的长期安全性提出挑战,明确CO_(2)劣化作用并建立本构模型至关重要。采用损伤力学理论和统计理论推导出能够综合反映CO_(2)吸附和荷载耦合作用下煤体总损伤变量的计算公式,并重点考虑了压密段的影响,分段建立了CO_(2)作用下煤体的细观统计损伤本构方程,明确了模型各参数的确定方法。最后通过CT扫描实验系统、MTS 816实验系统确定了本构模型参数,并采用自主研制的气−固耦合实验系统对不同CO_(2)压力下煤体进行了单轴压缩实验,验证了模型的合理性。研究结果表明:①基于CT扫描获取的裂隙率和运用Weibull分布理论分别定义了吸附和受载作用下的损伤变量,结合损伤理论进一步得到二者耦合作用下的总损伤变量,并建立了细观统计损伤本构模型;②基于CT扫描技术的裂隙三维重构真实反映了CO_(2)作用前后裂隙扩展特征,CO_(2)压力越高,裂隙扩展越充分,煤样三维裂隙参数和损伤变量越大,所形成的空间裂隙网络越复杂;③CO_(2)对煤体力学性质劣化作用显著,煤体的抗压强度与弹性模量随CO_(2)压力增加分别降低了49.78%和22.63%,CO_(2)对煤体的溶胀效应、塑化效应和气楔效应的综合作用导致了力学参数的降低;④建立的CO_(2)作用下煤体细观统计损伤模型理论曲线与单轴实验曲线具有较高的吻合度,说明损伤本构模型能够较好地反映出CO_(2)对煤体力学特性的损伤劣化作用,体现了损伤本构模型及模型参数确定方法的合理性与适用性。

超临界CO_(2)作用下无烟煤孔隙结构演化时间效应规律

CO_(2)地质封存技术是实现减排和废弃矿井资源再利用的有效技术之一,但煤层孔隙结构在CO_(2)注入后的变化具有时间效应,其演化规律将直接影响CO_(2)地质封存潜力。为了探索作用时间增加后煤层孔隙结构变化的真实情况,提高CO_(2)地质封存量计算精度,通过对重庆市南桐矿区无烟煤进行超临界CO_(2)吸附实验、低温氮气吸附实验、X射线衍射测试、核磁共振测试、扫描电镜测试等实验,研究了不同超临界CO_(2)作用时间对该区域内煤样孔隙结构的演化规律。研究结果表明:①超临界CO_(2)作用后煤样孔隙度的变化主要发生在7 d内,处理7 d后煤样孔隙度增加了3.20%,7~14 d内煤样孔隙度仅增加了0.05%;②随作用时间增加,煤样孔隙的比表面积增加但变化量逐渐减小,7 d内日均增长19.74%~24.50%,7~14 d内日均增长2.37%~4.60%,其变化规律近似呈对数函数关系;③超临界CO_(2)与煤产生的化学反应引起矿物质的溶解,增大了煤体的表面粗糙度,表征煤样粗糙度的分形维数随着作用时间的增加持续增大;④超临界CO_(2)作用后能有效改变煤样的孔隙度及表面形貌,为CO_(2)吸附提供了更多吸附点位,超临界CO_(2)对孔隙结构的改造效果在7 d内比较明显。结论认为,超临界CO_(2)作用下无烟煤孔隙结构的变化随作用时间增加最终会趋于稳定,研究结果可为无烟煤储层CO_(2)地质封存潜力评价提供理论指导。

衰竭底水气藏注CO_(2)提高天然气采收率与碳封存机理

气藏注CO_(2)提高天然气采收率并实现碳封存有望成为大幅度提高天然气产量与碳减排协同的潜在关键技术。为了给底水气藏注CO_(2)高效开发提供指导,针对地层水盐度对CO_(2)-CH_(4)-H_(2)O-NaCl体系相平衡影响、气藏注气过程中压力变化对CO_(2)-CH_(4)-H_(2)O-NaCl体系相平衡影响、注采方案对注CO_(2)提高气藏采收率影响、盐度对注CO_(2)提产及封存影响等目前认识不清的问题开展了CO_(2)-CH_(4)-H_(2)O-NaCl体系相平衡规律及注CO_(2)提采与封存数值模拟研究。研究结果表明:①随着盐度增加,CO_(2)和CH_(4)在盐水中的溶解度降低,液相的密度和黏度增加,盐度对气相性质几乎没有影响;②随着压力增加,CO_(2)和CH_(4)在液相中的溶解度均增加,气相、液相密度和黏度均增加,液相偏差因子随压力增加而增加,气相偏差因子先减小后增加;③同注同采方案CH_(4)产量更稳定且产出的CO_(2)少,而先注后采方案则会加速CO_(2)与CH_(4)的混合,CO_(2)封存量低,前者更适合注CO_(2)提采及封存;④在不考虑盐析效应的前提下,盐度对CH_(4)采收率和CO_(2)封存量的影响几乎可以忽略不计,不同盐度的衰竭底水气藏中CH_(4)采收率均超过80%、CO_(2)封存率均超过99%,短期注CO_(2)过程中,CO_(2)主要以气态或超临界态的形式被封存,少部分CO_(2)溶解在液相中,100年后CO_(2)在液相中的溶解质量分数约为5%。结论认为,衰竭底水气藏注CO_(2)能增压补能、驱替置换残余天然气,提高采收率并实现碳封存。

利用化学助剂强化CO_(2)埋存实验设计

结合储层CO_(2)埋存技术,自主搭建了地层温度压力条件下CO_(2)埋存实验装置,开展了多介质辅助CO_(2)埋存实验研究。研究结果表明,乙醇-KOH体系能够有效进行CO_(2)矿化埋存,其中96%乙醇+3 g KOH 500 mL溶液捕集CO_(2)能力最强,是最佳的CO_(2)矿化埋存溶液配比。经CO_(2)矿化埋存后,低渗透岩心孔隙度平均降低7.07%,孔隙度变化率与孔隙度呈正相关关系,渗透率平均降低16.01%。因此,96%乙醇+3 g KOH能够加速CO_(2)在储层中的CO_(2)沉淀过程,缩短CO_(2)在储层中的矿化埋存时间。该研究可重复性、准确性和可扩展性较强,能够激发学生自主设计实验的积极性及创新意识,培养学生的独立思考能力,有利于学生将理论知识与实际工程问题相结合,实现科研能力与创新能力的相互促进。

“双碳”愿景下CO_(2)驱强化采油封存技术工程选址指标评价

在国家能源安全和“双碳”战略愿景下,CO_(2)驱强化采油封存技术(CO_(2)-EOR)因能助力油气行业转型发展,成为“低碳化”乃至“负碳化”的首选技术和最现实的选择。无论是实验、数值模拟还是现场实践,目前国内外学者对CO_(2)-EOR研究侧重于CO_(2)作为高效的驱油“催化剂”本身及油藏CO_(2)-EOR适应性认识,对于工程选址评价缺乏统一标准和系统研究。在充分调研国内外文献的基础上,结合中国CO_(2)-EOR应用进展和工程实践,明确了CO_(2)-EOR工程选址可行性评价所需的通用依据,指出了CO_(2)-EOR工程选址遵循“CO_(2)封存与驱油双统一”、安全性、经济性的专属性原则,并从CO_(2)-EOR工程选址的地质、工程、安全、经济4个要素开展了较详尽系统的研究,定性-定量构建了“4+8+27”CO_(2)-EOR工程选址三级指标评价体系(GESE),以期为油藏开展CO_(2)-EOR工程选址提供借鉴,助力中国碳减排技术的应用与发展。

一种基于“四区”的低渗透油藏CO_(2)埋存量计算方法及应用

CO_(2)驱油和埋存能有效减少温室气体排放量达到碳中和目标,已有的CO_(2)埋存量计算方法主要针对CO_(2)的静态埋存量进行粗略计算,未考虑实际生产过程中CO_(2)埋存量的变化。针对上述问题,运用CO_(2)溶解、CO_(2)波及体积和驱油机理,将CO_(2)驱油与埋存过程分为气相区、两相或近混相区、扩散区和油相区,并基于“四区法”计算CO_(2)埋存量,得到了不同烃类的注入孔隙体积倍数、注入压力、注气速度下的CO_(2)动态埋存量的变化规律。将研究成果应用于W油田低渗储层,结果表明:注入烃类孔隙体积倍数、压力、注气速度与总埋存量呈正相关性,当压力由12 MPa升至30 MPa,CO_(2)埋存总量增加15.53×10^(4)t;当注气速度由5 t/d增加至30 t/d,峰值CO_(2)埋存总量由3.51×10^(4)t提高至12.62×10^(4)t。研究成果可为同类油藏开展CO_(2)驱油与埋存项目提供新的思路。