氢通量技术在缓蚀剂效果评价中的应用

为了有效检测塔里木油田缓蚀剂在管道中的应用效果,更好地指导现场缓蚀剂的筛选及加注,对目前应用的监测技术进行分析,指出现有监测方法存在的问题,引进具有无损、实时、全周相等优势的氢通量监测技术。现场试用结果表明,氢通量技术能够快速、准确、稳定地测出现场管线腐蚀数据,与挂片数据、缓蚀剂残余浓度数据具有一定的相关性,满足管道中缓蚀剂效果的检测,可以有效地用于含硫区块缓蚀剂效果跟踪评价。     

高含硫集气管线腐蚀监控技术研究

针对高含硫集气管线输送特点,采用无损氢通量监测技术,研究了缓蚀剂涂覆预膜技术在高含硫集气管线上的应用效果。结果表明,缓蚀剂涂覆预膜技术能明显控制高含硫集气管线腐蚀,涂覆后缓蚀剂在管线各个方向分布均匀,涂覆预膜有效保护周期约为58天。     

高含硫气田腐蚀特征及腐蚀控制技术

我国高含硫气藏H₂S、CO₂含量高,还伴随有大量的气田水,开发过程中腐蚀问题非常突出。为此,分析了高含硫气田的腐蚀特征,展示了该类气田开发在材料选择与评价、缓蚀剂防腐技术、腐蚀监测与检测技术等方面的进展：①提出了镍基合金评价方法、双金属复合管及其焊缝抗环境应力开裂试验方法和耐蚀性能评价程序、缓蚀剂筛选评价程序;②研发的专利缓蚀剂CT2- 4水溶性环空保护液体系能实现对套管内壁和油管外壁的有效保护,CT2-19缓蚀剂、地面管线清管器预膜技术和缓蚀剂连续加注技术较好地控制了湿气密闭输送系统内的腐蚀;③FSM、氢探针技术、电化学噪声技术等腐蚀监测新技术在研究点蚀、缝隙腐蚀和氢致开裂等方面具有独特的优势。最后提出在高含硫气田开发设计时,就应全面引入腐蚀控制设计和腐蚀监测体系,从腐蚀控制技术的集成与优化入手,形成高含硫气田整体防腐方案,建立数字化腐蚀数据管理系统和数据库,全面跟踪评价缓蚀剂效果,从而实现腐蚀控制的整体设计和完整性管理。     

应用显色萃取法测定塔里木油田采出液中残余缓蚀剂的浓度

油气开采及输送过程中常伴有CO_2、H_2S等气体的腐蚀,为保证油气田安全运营,通过投加缓蚀剂来减缓腐蚀速率。随着时间的增加,投加的缓蚀剂有效质量浓度无法确定,为了建立合理的集输管线缓蚀剂加药制度,需要对采出液中缓蚀剂的残余浓度进行测定。利用显色萃取法测定塔里木油田采出液中的缓蚀剂残余浓度,可以消除采出液中大量干扰离子的影响,且缓蚀剂质量浓度与吸光度成正比,线性关系较好,因此使用显色萃取法对塔里木油田采出液中的缓蚀剂残余浓度进行日常检测准确、简单、可行。     

深热含硫气井防腐蚀有效措施

美国南阿拉巴马州大Escambia河湾（BEC）气田含硫气井的生产环境，由280F、21％的H2S、40％的CO2和在采出水中浓度高达190000ppm的氯化物构成。严重腐蚀的状况迫切要求实现一项缓蚀计划，使这些井安全经济地进行生产。本文描述了井下和集气系统腐蚀防止与监测计划的基本情况、技术研究发展及其成果。该计划内容包括：在腐蚀最严重的井中自环形空间注入水溶性缓蚀剂，以此实现井下的持续性防腐；对其余的井以油溶性缓蚀剂分批处理置换硝化油管；在集气管线中为扩大分批处理，以及在选出的严重腐蚀的井中连续注入一种水溶性缓蚀剂；监测缓蚀剂残余产物并绘制趋势曲线图，以保证井下处理的有效性和优化注入率；以及出口管线内径规和水压试验以监测集气管线的防腐计划。本文还介绍了用于设计、计算和更新连续井下注入系统和硝化分批处理的计算机处理方法。由达到的油管寿命、缓蚀剂残余物的现场数据以及出口管线和井下的内径规，验证了该腐蚀防止与监测计划是成功的。文中提供的数据资料，有助于对严重腐蚀的生产环境的防腐蚀计划进行成功的设计与实施。     

普光气田集输系统腐蚀监测技术与应用

针对普光高含硫气田地面湿气集输系统工艺特点,对集输管道腐蚀环境进行机理分析,明确了管道面临的腐蚀形势。为提高集输系统腐蚀监测的准确性、有效性,根据不同集输环节、腐蚀类型、诱发时间,结合监测设备对腐蚀的响应速率,优选腐蚀监测方法、监测设备,优化各种腐蚀监测技术的工作制度、监测装置的分布及数量,建立完善的湿气集输系统腐蚀监测网络,形成以挂片与探针有机结合的在线集成腐蚀监测技术。结合现场工况,监测数据分析结果表明,监测体系完善,监测数据及时准确,为防腐措施实施,缓蚀剂配方、加注量及批处理频率等参数优化调整提供了数据支撑,有效防止了腐蚀加剧,普光气田集输管道主体平均腐蚀速率控制在小于0.076 mm/a,保证了管道安全平稳运行。     

S-Y气田集输工艺装置腐蚀与位移控制措施

S-Y高含硫气田地面管线腐蚀以内部坑蚀、点蚀为主,积液管线内部腐蚀严重;地面管线高温运行,形成热应力集中,导致地面阀门抬高、汇管发生位移。为有效控制高含硫天然气对地面管线、设备腐蚀以及地面管线高温运行发生位移,在对其腐蚀机理和地面工艺防腐的适应性分析,以及对高温运行发生位移应力计算分析基础上,通过优化调整缓蚀剂加注制度,更换关键部位管线材质;对管线应力泄放适应性技术整改。现场运行情况来看,地面管线腐蚀得到了有效控制,地面管线受热膨胀产生的应力得到了有效释放,控制在了规定范围内。     

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中国石油西南油气田分公司川中油气矿磨溪气田位于四川省遂宁市以南25km处，是一整装含硫气田。该气田从上世纪九十年代初投入开采以来，井下的油套管以及地面的集输气管线，阀门，分离器，排污管线都遇到了大量的腐蚀问题，是我国腐蚀最严重，腐蚀因素最复杂的含硫气田之一。通过大量的的技术攻关和现场实践，运用以下技术和措施；对井下油管采用了玻璃钢油管，集输气管线加注高效缓蚀剂，节硫阀采用陶瓷油嘴节流降压技术，分离器结构进行了改进，排泄管线采用了钢骨架复合筛管，逐步形成了一整套适合该气田实际的综合防腐配套工艺技术，从整体上提高了该气田的开采效益。     

元坝高含硫站场排污管线腐蚀风险及技术对策

元坝气田天然气中高含硫化氢、中含二氧化碳,且气井普遍产出凝析水和地层水,溶解了硫化氢气体的气田水进入天然气集输系统站场内的排污管道,导致抗硫碳钢排污管内腐蚀环境恶劣,存在较大的腐蚀风险。通过室内实验和现场试验评价分析,认为抗硫碳钢A333须有缓蚀剂配合使用才能满足含硫湿酸气环境下的腐蚀控制需求;在没有缓蚀剂保护的内腐蚀环境下,抗硫碳钢A333以局部腐蚀为主,腐蚀呈现点蚀扩大和坑蚀现象,平均腐蚀速率达到1 mm/a以上。针对现场排污管线腐蚀风险,制定了元坝气田站场排污管线腐蚀控制技术对策和研究方向,为同类含硫气田站场排污管线材质优选和腐蚀控制方案确定提供了借鉴和参考。     

酸性气田缓蚀剂现场效果评价技术及应用

目的利用气田水分析、现场腐蚀监测/检测等方法形成酸性气田缓蚀剂现场效果评价技术。 方法在实验室考查了缓蚀剂残余质量浓度分析、超声波测厚、电化学探针等方法的有效性。 结果缓蚀剂残余质量浓度标准曲线拟合值相关系数在99.9%以上、超声波测试结果相对误差最高在0.67%、电化学探针作为评价缓蚀剂的效果手段具有相当的灵敏性。 结论利用形成的酸性气田缓蚀剂现场效果评价技术,在龙王庙某原料气管线开展应用,结果表明可以有效评价缓蚀剂现场应用效果,评价结果与现场腐蚀检测结果相吻合。      

低渗透油藏水驱转空气泡沫驱提高采收率物理模拟实验

为进一步提高镇泾油田低渗透油藏原油采收率,利用室内驱油物理模拟技术,开展了水驱转空气泡沫驱提高采收率实验研究,探讨了空气泡沫驱对低渗透油藏水驱开发效果的影响。实验结果表明,在模拟地层条件下,初始水驱阶段的平均采收率为29.06%,水驱转空气泡沫驱后,采收率得到明显提高,增量均在10%以上;再次水驱后,最终采收率平均可达到45.42%。随着空气泡沫注入速度的增加,采收率呈上升趋势,但增幅逐渐减小。注入速度越大,气体突破时间越早,不过实验过程中并未发生明显的因气窜而导致采收率降低的现象;在相同条件下,空气泡沫注入总量为1倍孔隙体积时的采收率比0.6倍孔隙体积时的高5%。研究认为,通过交替注入起泡剂溶液与空气实现空气泡沫驱对于注水开发的低渗透油藏进一步提高原油采收率是可行的。     

Effect of stress sensitivity on displacement efficiency in CO2 flooding for fractured low permeability reservoirs

Carbon dioxide flooding is an effective means of enhanced oil recovery for low permeability reservoirs. If fractures are present in the reservoir, CO2 may flow along the fractures, resulting in low gas displacement efficiency. Reservoir pore pressure will fluctuate to some extent during a CO2 flood, causing a change in effective confining pressure. The result is rock deformation and a reduction in permeability with the reduction in fracture permeability, causing increased flow resistance in the fracture space. Simultaneously, gas cross flowing along the fractures is partially restrained. In this work, the effect of stress changes on permeability was studied through a series of flow experiments. The change in the flowrate distribution in a matrix block and contained fracture with an increase in effective pressure were analyzed. The results lead to an implicit comparison which shows that permeability of fractured core decreases sharply with an increase in effective confining pressure. The fracture flowrate ratio declines and the matrix flowrate ratio increases. Fracture flow will partially divert to the matrix block with the increase in effective confining pressure, improving gas displacement efficiency.     

Black Oil and Compositional Reservoir Simulation for Increasing the Recovery Performance of an Iranian Fractured Carbonate Reservoir

Abstract

Naturally fractured reservoirs contain a significant amount of world oil reserves. Accurate and efficient reservoir simulation of naturally fractured reservoirs is one of the most important, challenging, and computationally intensive problems in reservoir engineering. Black oil and compositional reservoir simulators have been used to determine the reservoir management and production strategies to increase the oil recovery from a low-porosity, low-permeability fractured carbonate reservoir, with an average matrix permeability of 0.8 md, average fracture permeability of 500 md, and an average matrix porosity of 10%. This reservoir is a candidate for an enhanced oil recovery (EOR) process, because the reservoir production rate has been declined due to increasing the water cut as a result of rising the water oil contact. The injection techniques that have been considered in this study for black oil model include (a) gas injection, (b) water injection, and (c) simultaneous water alternating gas injection and for the compositional model include (a) dry gas injection, (b) CO₂ injection, and (c) N₂ injection. Simulation results show that CO₂ injection has the maximum oil recovery between the EOR scenarios.     

裂缝性致密油藏超临界CO2泡沫驱规律实验研究

超临界CO2泡沫可以有效降低CO2流度,提高封堵强度,抑制CO2在裂缝性致密油藏岩心中的窜流。在接近油藏条件下对8种起泡剂进行评价,优选出稳定性最好的起泡剂;研究不同气液比、裂缝开度及注入方式下超临界CO2泡沫的岩心渗流特征,分析水驱和气驱后超临界CO2泡沫驱油规律。结果表明:质量分数为0.5%时,起泡剂HY-2稳定性最好;气液比为1.0时对裂缝性致密岩心封堵效果最好,对裂缝开度在39.80~82.67μm时有较好的适应性,气液同时注入更有利于提高超临界CO2泡沫封堵效果,在水驱或气驱基础上,超临界CO2泡沫驱可使采收率提高20%以上。因此,一定条件下的超临界CO2泡沫驱对裂缝性致密油藏提高采收率有显著效果。     

Profile improvement during CO2 flooding in ultra-low permeability reservoirs

Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.     

低渗透稀油油藏水驱后氮气泡沫驱适应性

吐哈油田低渗透稀油油藏注水开发进入高含水期后,水淹程度高,水驱调整措施效果较差,亟需寻找后续提高采收率方法。针对低渗透油藏注入能力差、不适合注聚合物等高黏度流体的特点,利用水驱、氮气泡沫驱和水驱后氮气泡沫驱开展室内实验研究,探讨驱油效率及其影响因素。结果表明,水驱驱油效率随渗透率的增加而升高,与渗透率呈较好的对数关系;氮气泡沫驱驱油效率为67.66%,较水驱驱油效率提高10.62%;氮气泡沫驱可在水驱的基础上提高驱油效率约9.63%。实验用泡沫的残余阻力系数大于1,表明氮气泡沫驱通过堵水调剖,提高了水驱后油藏的采收率,从机理和实验提高驱油效率程度判断,氮气泡沫驱适用于吐哈油田低渗透稀油油藏。     

An Experimental Investigation of Foam for Gas Mobility Control in a Low-Temperature Fractured Carbonate Reservoir

Abstract

This work concerns the experimental investigation of surfactant alternating CO₂ injection in carbonate rocks. The core samples provided from a low-temperature fractured light oil reservoir, located in southwest Iran. The experiments were designed to observe the effect of CO₂–foam injection on gas mobility and oil recovery at different surfactant concentrations. The core samples were initially saturated with synthetic/field brine, 5,000 ppm, and then flooded with live oil to reach connate water saturation at reservoir condition, 115°F and 1,700 psia. The commercial surfactant used was sodium lauryl sulfate as an anionic surfactant. The results of this work, along with field-scale simulation and/or economic considerations, could be helpful in making reliable decisions about optimum condition of foam-assisted water-alternating-gas (FAWAG) processes.

Core flooding results demonstrated that macroscopic sweep efficiency increased due to foam generation inside the core. In addition, it led to an increase of between 5 and 12% in the recovery factor in comparison to a water-alternating-gas (WAG) process. Furthermore, the value of the critical micellar concentration for the surfactant–oil system was about 2,000 ppm.

After primary and secondary recovery processes, there is a large amount of trapped oil in the reservoir. Extensive research has been directed toward enhancing the recovery of this oil, but limited success has been achieved. FAWAG injection appears to have more applicability to recover the trapped resources. However, little attention has been paid to experimental investigation of FAWAG processes in low-temperature oil reservoirs.     

Gas Injection Into Fractured Reservoirs Above Bubble Point Pressure

Abstract

Among all enhanced oil recovery (EOR) scenarios, gas injection seems to be promising for implementation in naturally fractured reservoirs. The use of CO₂ has received considerable interest as a method of EOR but a major drawback is its availability and increasing cost. Therefore, an alternative gas like CH₄ or N₂ must be considered to meet the economic considerations. To investigate the efficiency of oil recovery by CO₂, N₂, and CH₄ injection in fractured carbonate rock, a series of experiments was designed. Both miscible and immiscible schemes for gas injection were carried out on a low-permeable outcrop carbonate rock that was surrounded by fracture, established with a novel experimental method. The experiments aimed to investigate the potential of oil recovery by secondary and tertiary gas injection under high-temperature conditions. The matrix block was saturated using a recombined mixture of Iranian live oil, and by pumping water into the annular space, the space between rubber sleeve and outer jacket, high overburden pressure was exerted to obtain the desired homogeneous saturation. Using a back-pressure regulator, the pressure was kept above the bubble point pressure. The inlet was attached to a constant pressure pump injecting gas or water above the bubble point pressure, and the overburden pressure was removed gradually and the inlet fluid inflated the rubber sleeve. The amount of produced water from the annular space was recorded to estimate the distance between the rubber sleeve and sand face. This distance creates the fracture surrounding the core. Gas was injected into the fracture at pressures above the bubble point of the oil. Oil recovery as a function of time was monitored during the experiments. Results from both secondary and tertiary gas injection experiments indicate that CO₂ injection at elevated pressure and temperature is more efficient than N₂ and CH₄ injection.     

特低渗砂岩油藏CO2-低界面张力黏弹流体协同驱油机理研究

目的特低渗油藏储层物性差、层间非均质性强,造成CO₂驱易发生气窜,提高采收率效果欠佳,其中,CO₂水气交替驱作为结合CO₂驱和水驱优势的方法,具有较高的适用性。为进一步改善CO₂-水交替驱的开发效果,开展了CO₂-低界面张力黏弹流体协同驱油研究。 方法通过界面张力和润湿性能测试评价低界面张力黏弹流体基本性能,并利用微观可视化驱油实验及岩心驱油实验等,探究了不同驱替方式的驱油效果和CO₂-低界面张力黏弹流体协同驱油过程中二者之间的“协同作用”机理。 结果低界面张力黏弹流体具备良好的界面活性和改变岩石表面润湿性能力,水驱后开展CO₂驱、低界面张力黏弹流体驱、CO₂-低界面张力黏弹流体交替协同驱,采收率可在水驱基础上分别提高0.91%、10.66%、16.25%,其提高采收率机理包括降低界面张力、改善流度比、改变岩石表面润湿性及乳化作用的协同效应等。 结论CO₂-低界面张力黏弹流体协同驱既可有效增强非均质特低渗砂岩油藏注CO₂过程中气体流动性控制,又能够降低CO₂萃取轻烃导致重质组分沉积的影响,具有协同增效作用。      

裂缝储层空气泡沫驱注入参数优化实验

为提高裂缝性油藏空气泡沫驱的采收率,以王窑中西部地区长₆段储层为研究对象,开展前期水驱、空气泡沫驱、后续水驱实验,优化气液体积比、泡沫段塞体积、注入压力、注入速率和注入时机等参数。结果表明:泡沫注入岩心后,含水率迅速降低,采出程度迅速提高,裂缝岩心相对基质岩心封堵更快,但封堵效果较差;注入空气泡沫时间越早,最终采收率越高;最优气液体积比、泡沫段塞体积、注入压力、注入速率与岩心渗透率呈负相关,但因裂缝渗透率较大,渗透率变化对最佳注入参数的敏感性较弱。该研究结果可为低渗透油藏裂缝性储层空气泡沫驱精细化注入提供重要的理论依据。