低渗透气藏型储气库储层物性参数的反演分析

低渗透气藏改建的地下储气库注气过程,渗透率和孔隙度随着地层压力变化显著。为更准确的模拟计算低渗透气藏地下储气库的注采过程,必须掌握储气库渗透率和孔隙度随地层压力的变化规律。首先基于地质统计学中的变差函数理论,以井点已知信息为条件,确定储层物性参数的初始分布。基于反问题理论,利用地层压力的测量值和计算值之差构造目标函数,将储层物性参数的反演识别问题转化为最优化问题。通过地层压力对孔隙度和渗透率变化率的求解,利用共轭梯度法实现了对储层物性参数的反演。通过案例证明了模型的正确性。以储气库中的某一区域为研究对象进行反演分析,结果表明：虽然渗透率和孔隙度在初始时在储层中的分布规律基本一致,但是在注气结束时各位置的渗透率和孔隙度变化率都不相同,二者之间的相关性不再一致。其中渗透率变化最大的位置出现在5#注采井附近,其值由1.66×10^-3μm²增加到2.81×10^-3μm²,增加了近70%。并利用最小二乘法拟合得到了渗透率和孔隙度与地层压力之间的函数关系式。本研究成果可以为低渗透气藏改建地下储气库的注采模拟提供...     

呼图壁低压水敏储层保护钻井液技术

枯竭气藏型地下储气库地层压力系数低,钻完井中储层保护难度大.针对呼图壁储气库水平井大压差钻完井中井筒工作液深度侵入储层造成严重储层损害的难题,通过储层岩石的矿物组分分析和膨胀性、润湿性、自吸钻井液滤液的渗透率损害率测定,分析了呼图壁储气库储层损害的主要方式,即强水敏地层的黏土水化膨胀和致密储层的液锁损害;提出了强化抑制...     

R油藏改建地下储气库单井注采能力分析

单井注采能力分析是改建地下储气库优化单井产能参数的一项重要研究内容.以R油藏建库为研究对象,采用节点分析方法,模拟计算管流动态.根据协调点、冲蚀临界流量、携液临界流量以及地层压力、地层破裂压力和地面压缩机额定功率的边界限制分别预测了不同油管尺寸的采气能力和注气能力.为合理选择完井油管尺寸和在注采过程中控制井口压力提供了参考.研究结果表明:R油藏改建库采用国际上目前普遍采用的184.2mm油管,其采气能力在185×104～390×104m3/d,注气能力在25×104～295×104m3/d.     

火山岩气藏开发现状综述

根据国内外火山岩气藏勘探开发的成功实例,分析总结了一般火山岩气藏的地质特征和开发特征,即火山岩气藏岩石类型繁多和岩性复杂、孔隙结构复杂、储集空间类型特殊多样、孔隙度小、渗透率低并且孔隙度和渗透率差异大、储层非均质性严重、含气面积和有效厚度变化大、气水分布复杂、双重介质储层.着重分析了升平气田火山岩储层的地质特征和该火山岩气藏开发特点.指出了产量稳定、地层压力下降小,气井产量大小与裂缝关系等火山岩气藏一般开采特征.提出了火山岩气藏增产措施和储层保护措施.     

油藏改建储气库注采速度敏感性实验研究

针对长岩芯试验研究注采速度敏感性中存在的可重复性差、围压与系统压力高、误差较大、注入速度与实际地层气水界面运动速度偏大等问题,提出了采用短岩芯进行物理实验的研究方案与技术思路,完成了注气速度敏感性实验和采气速度敏感性实验,取得了油藏改建成储气库时有关注气速度与库容能力、采气速度与水驱气效率的一般性认识.对我国的能源战略规划、西气东输工程等具有重大意义.     

苏里格气田苏59井区气水分布规律研究(1)

苏里格气田苏59井区气藏属于典型的低孔低渗致密砂岩气藏,气水分布规律及控制因素不明,主力产层出水严重,气水分布复杂.针对此现象,根据气田录井、钻井、测井、试气等资料,运用交汇图法识别工区气水层,讨论气水分布特征.研究认为,该区存在多个气水系统,未见统一的气水界面,单个气水系统内呈“上气下水”的分布状态.H8段储层物性优于S1段,砂体之间连通性较好,但产水量大.S1段靠近下伏烃源岩,受到烃源岩的高强度充注,表现出“气多水少”的特征;单砂体内气水明显分异,没有“上水下气”的倒置现象.气水分布受储层构造、圈闭类型、储层非均质性和物性等因素的控制.     

超临界CO_2增透煤热流固耦合模型与数值模拟

针对中国绝大多数高瓦斯煤层渗透性低以及低渗透煤层强化抽采瓦斯效果不理想的现状,结合超临界CO_2强扩散和溶解增透孔隙介质等独特优点,依据超临界CO_2作用后煤微观孔裂隙的演化特征,得到煤微观孔隙率和渗透率演化方程,根据孔隙率的变化确定损伤变量,考虑体积应力、温度、孔隙压力及超临界CO_2溶解增透作用的影响,建立超临界CO_2作用后煤的热流固耦合力学模型,利用ABAQUS软件提供的场变量子程序,结合PYTHON脚本和子程序二次开发功能,实现低渗透煤层注超临界CO_2增透规律数值模拟。结果显示:超临界CO_2注入后,注气孔周围煤体内体积应力、温度及孔隙压力变化明显,随着距注气孔距离的增加,影响程度逐渐减弱,并趋于稳定;经超临界CO_2作用后,注气孔周围煤体内不断萌生新的孔裂隙,并与原有的孔裂隙相互贯通,随注气时间的延长各级孔裂隙不断向煤体纵深演化发展,煤微观孔隙率较注气前提高了2个数量级;超临界CO_2的致裂增透作用引起煤体不同程度的损伤,距注气孔越近,损伤程度越大,损伤增加越快,注气时间越长,损伤增加的幅度越大;煤微观孔裂隙的有效发育为煤层气的扩散渗流提供了更多的运移通道,使煤体渗透系数较注气前提高了3个数量级。     

海上带油环高含CO_2凝析气藏的高效开发

A油田东三段Ⅰ油组是带油环凝析气藏,其凝析气顶高含CO2、高含凝析油,油环跨度小,油柱高度低,边底水能量弱,以Eclipse数值模拟技术对该油田进行合理开发方式优选、开发井型井位比选及提高采收率措施评价,形成一套此类凝析气藏高效开发的模式.结果表明:对于弱边水高含CO2、高含凝析油的凝析气藏,循环注气保持凝析气顶压力开发是最为合理的开发方式;对于小跨度、低油柱高度的油环,水平井平行气油界面且距气油界面油柱高度处是最为合理的开发井型和井位;对于"趾跟效应"和储层非均质性引起的水平井非均匀流动,ICD(Inflow Control Device)控气避水技术是最为有效的减缓气水突进的措施.     

陕45井区奥陶系马五1＋2气藏数值模拟研究

陕甘宁盆地陕45井区奥陶系马五1 2气藏属于低渗透、低丰度、统一压力系统下受岩性一地层圈闭控制的定容封闭弹性气驱干气藏,储层致密,裂缝发育差,为孔隙型储层.为改善开发效果,在历史拟合修正地质模型的基础上,根据气藏工程设计要求和目前生产状况,综合考虑井网、采气速度、增产措施等多种因素的不同组合,设计了6套模拟预测方案.进行对比并选出了最合理的开发方案.     

修正等时试井资料分析新方法在克拉美丽气田火山岩气藏中的应用

克拉美丽气田是新疆油田公司在准噶尔盆地腹部发现的首个1000亿方级的大型火山岩气田,前期测试及生产资料表明气藏储层物性平面变化大,渗透性差,常规的回压法产能试井耗时长,天然气消耗大,修正等时试井延续测试期间流压很难达到稳定,影响气藏产能分析与评价。本文采用修正等时试井资料处理新方法来分析解释低渗透火山岩气藏修正等时试井资料,实例分析表明该方法处理低渗透气藏产能测试资料的可靠性,为分析评价火山岩气藏产能大小提供了一种可靠的方法。     

Numerical Simulation and Analysis of Migration Law of Gas Mixture Using Carbon Dioxide as Cushion Gas in Underground Gas Storage Reservoir

One of the major technical challenges in using carbon dioxide（ CO2） as part of the cushion gas of the underground gas storage reservoir（ UGSR） is the mixture of CO2and natural gas. To decrease the mixing extent and manage the migration of the mixed zone,an understanding of the mechanism of CO2and natural gas mixing and the diffusion of the mixed gas in aquifer is necessary. In this paper,a numerical model based on the three dimensional gas-water two-phase flow theory and gas diffusion theory is developed to understand this mechanism. This model is validated by the actual operational data in Dazhangtuo UGSR in Tianjin City,China.Using the validated model,the mixed characteristic of CO2and natural gas and the migration mechanism of the mixed zone in an underground porous reservoir is further studied. Particularly,the impacts of the following factors on the migration mechanism are studied： the ratio of CO2injection,the reservoir porosity and the initial operating pressure. Based on the results,the optimal CO2injection ratio and an optimal control strategy to manage the migration of the mixed zone are obtained. These results provide technical guides for using CO2as cushion gas for UGSR in real projects.     

Performance analysis for underground gas storage reservoir in depleted gas field

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CO<Subscript>2</Subscript> permeability of fractured coal subject to confining pressures and elevated temperature: Experiments and modeling

The CO₂ permeability of fractured coal is of great significance to both coalbed gas extraction and CO₂ storage in coal seams, but the effects of high confining pressure, high injection pressure and elevated temperature on the CO₂ permeability of fractured coal with different fracture extents have not been investigated thoroughly. In this paper, the CO₂ permeability of fractured coals sampled from a Pingdingshan coal mine in China and artificially fractured to a certain extent is investigated through undrained triaxial tests. The CO₂ permeability is measured under the confining pressure with a range of 10–25 MPa, injection pressure with a range of 6–12 MPa and elevated temperature with a range of 25–70°C. A mechanistic model is then proposed to characterize the CO₂ permeability of the fractured coals. The effects of thermal expansion, temperature-induced reduction of adsorption capacity, and thermal micro-cracking on the CO₂ permeability are explored. The test results show that the CO₂ permeability of naturally fractured coal saliently increases with increasing injection pressure. The increase of confining pressure reduces the permeability of both naturally fractured coal and secondarily fractured coal. It is also observed that initial fracturing by external loads can enhance the permeability, but further fracturing reduces the permeability. The CO₂ permeability decreases with the elevation of temperature if the temperature is lower than 44°C, but the permeability increases with temperature once the temperature is beyond 44°C. The mechanistic model well describes these compaction mechanisms induced by confining pressure, injection pressure and the complex effects induced by elevated temperature.     

天然气地下储气库垫层气与工作气混合的模拟研究

天然气地下储气库的建筑是调节城市用气不均衡性、平抑供气峰波动的最合理有效的手段之一,在储气库进行注采动态运行时,避免注入气与垫层气发生混合是关键技术问题,本文通过分别建立三维两相渗流模型和三维气体扩散模型,采用跳跃式的求解方法,首先求出库内各点瞬态压力分布,再根据达西定律确定出速度分布,最后通过求解三维气体扩散数值模型,可动态的确定垫层气的需求量和注采天然气所需的最佳储气压力,残存气与储存天然气的混合而导致的回采气体浓度的变化,为保证储库满负荷的优化运行提供科学依据。     

二氧化碳管道运输系统优化模型及其应用

二氧化碳捕集利用与封存(CCUS)作为能够实现煤化工行业温室气体大规模减排的前沿技术,已成为当前研究热点.而管道运输是该技术得以实施的关键环节,高昂运输成本是影响该技术大规模推广的主要因素.因此,通过开发煤化工二氧化碳(CO_2)捕集压缩、管道运输系统优化模型,实现CO_2管道运输系统内关键环节的工艺和技术优化配置,降低捕集压缩、运输及注入整个系统的总成本.将模型初步应用于陕西延长榆林煤化工CCUS项目,结果表明:当封存区域CO_2封存需求量小,而且能够在封存现场提供方便的液化压缩设备时,榆林能化煤化工企业可以采用气相压缩输送方案,并结合封存地点液化加压注入;对于大规模CO_2封存及运输需求时,推荐超临界/密相CO_2输送,能够有效减少封存区再次加压环节的成本,从而使整个流程更为经济.     

Monitoring of CO2 geological storage based on the passive surface waves

Carbon dioxide (CO₂) capture and geological storage (CCS) is one of promising technologies for greenhouse gas effect mitigation. Many geotechnical challenges remain during carbon dioxide storage field practices, among which effectively detecting CO₂ from deep underground is one of engineering problems. This paper reviews monitoring techniques currently used during CO₂ injection and storage. A method developed based on measuring seismic microtremors is of main interest. This method was first successfully used to characterize a site in this paper. To explore its feasibility in CO₂ storage monitoring, numerical simulations were conducted to investigate detectable changes in elastic wave signatures due to injection and geological storage of CO₂. It is found that, although it is effective for shallow earth profile estimation, the surface wave velocity is not sensitive to the CO₂ layer physical parameter variations, especially for a thin CO₂ geological storage layer in a deep underground reservoir.     

基于数值模拟的CO2地质封存项目井筒泄漏风险定量化评价方法

为评估CO₂地质封存场地的CO₂沿井筒泄漏风险，介绍了自主研发的可对CO₂井筒泄漏风险进行定量化评价的数值模拟WellRisk软件，将软件应用于实际CO₂地质封存场地--神华鄂尔多斯CO₂咸水层封存示范工程，定量评估该场地CO₂沿注入井和监测井的泄漏量，并将软件模拟结果与美国能源部开发的NRAP–IAM–CS（The national risk assessment partnership–integrated assessment model–carbon storage）软件模拟结果进行对比，实现了CO₂沿井筒泄漏风险的定量化评价。定义了井筒泄漏系数，即井筒发生泄漏的有效截面积和井筒总截面积的比值，并将井筒泄漏系数作为量化表征井筒固井质量的重要参数。当泄漏系数取值为10^–6时，神华CO₂地质封存场地在1 000 a内的总泄漏量为720 tCO₂，占总注入量的0.24%，小于IPCC的风险阈值1%。因此，泄漏系数为10^–6或更低的井筒是低风险泄漏井，具有良好的固井质量，对应于NRAP–IAM–CS软件中井筒渗透率低于10^–12 m²的情况。泄漏系数为10^–5或更高的井筒是高风险泄漏井，具有较差的固井质量。WellRisk和NRAP–IAM–CS的计算结果均表明，当注入井和监测井的固井质量良好时，神华CO₂地质封存场地基本不存在CO₂泄漏风险。     

规整填料内乙醇胺吸收CO2的计算流体力学模拟

为模拟规整填料单元内乙醇胺吸收烟气二氧化碳的过程,利用计算流体力学(CFD),考虑包含化学反应气液质量传递过程,建立伴有二级化学反应的气液两相流动模型.通过改变吸收过程的操作条件,如气液入口流量比、CO_2入口质量分数、乙醇胺入口摩尔分数、压强等,分析吸收塔规整填料单元内碳捕捉过程的影响因素.CFD模拟结果表明:CO_2吸收率随乙醇胺浓度与压强的增大而升高;随烟气CO_2浓度与气液流量比的增大而下降;对各影响因素影响定量排序,乙醇胺浓度对吸收效率影响最突出,其次依次是CO_2入口浓度、气液入口流量比、压强.模拟与试验结果相吻合,得出了相应的最优参数.     

Preferential adsorption behaviour of CH4 and CO2 on high-rank coal from Qinshui Basin,China

In order to better understand the prevailing mechanism of CO₂ storage in coal and estimate CO₂ sequestration capacity of a coal seam and enhanced coalbed methane recovery (ECBM) with CO₂ injection into coal, we investigated the preferential adsorption of CH₄ and CO₂ on coals. Adsorption of pure CO₂, CH₄ and their binary mixtures on high-rank coals from Qinshui Basin in China were employed to study the preferential adsorption behaviour. Multiple regression equations were presented to predict CH₄ equilibrium concentration from equilibrium pressure and its initial-composition in feed gas. The results show that preferential adsorption of CO₂ on coals over the entire pressure range under competitive sorption conditions was observed, however, preferential adsorption of CH₄ over CO₂ on low-volatile bituminous coal from higher CH₄-compostion in source gas was found at up to 10 MPa pressure. Preferential adsorption of CO₂ increases with increase of CH₄ concentration in source gas, and decreases with increasing pressure. Although there was no systematic investigation of the effect of coal rank on preferential adsorption, there are obvious differences in preferential adsorption of gas between low-volatile bituminous coal and anthracite. The obtained preferential adsorption gives rise to the assumption that CO₂ sequestration in coal beds with subsequent CO₂-ECBM might be an option in Qinshui Basins, China.