Experimental investigation on stable displacement mechanism and oil recovery enhancement of oxygen-reduced air assisted gravity drainage

The effects of gravity,capillary force,and viscous force on the migration characteristics of oil and gas interface in oxygen-reduced air-assisted gravity drainage(OAGD)were studied through a two-dimensional visualization model.The effects of bond number,capillary number and low-temperature oxidation on OAGD recovery were studied by long core displacement experiments.On this basis,the low-temperature oxidation number was introduced and its relationship with the OAGD recovery was established.The results show that the shape and changing law of oil and gas front are mainly influenced by gravity,capillary force and viscous force.When the bond number is constant(4.52×10-4),the shape of oil-gas front is controlled by capillary number.When the capillary number is less than 1.68×10-3,the oil and gas interface is stable.When the capillary number is greater than 2.69×10-2,the oil and gas interface shows viscous fingering.When the capillary number is between 1.68×10-3 and 2.69×10-2,the oil and gas interface becomes capillary fingering.The core flooding experiments results show that for OAGD stable flooding,before the gas breakthrough,higher recovery is obtained in higher gravity number and lower capillary number.In this stage,gravity is predominant in controlling OAGD recovery and the oil recovery could be improved by reducing injection velocity.After gas breakthrough,higher recovery was obtained in lower gravity and higher capillary numbers,which means that the viscous force had a significant influence on the recovery.Increasing gas injection velocity in this stage is an effective measure to improve oil recovery.The low-temperature oxidation number has a good correlation with the recovery and can be used to predict the OAGD recovery.

Research on the Corrosion of J55 Steel Due to Oxygen-Reducing Air Flooding in Low-Permeability Reservoirs

Oxygen-reducing air flooding is a low-permeability reservoir recovery technology with safety and low-cost advantages.However,in the process of air injection and drive,carbon in the air is oxidized through the crude oil reservoir to generate CO_(2),and this can cause serious corrosion in the recovery well.In this study,experiments on the corrosion of J55 tubular steel in a fluid environment with coexisting O_(2)and CO_(2)in an autoclave are presented.In particular,a weight loss method and a 3D morphometer were used to determine the average and the local corrosion rate.The corrosion surface morphology and composition were also measured by means of scanning electron microscopy(SEM)and an X-ray diffractometer(XRD).The corrosion pattern and morphological characteristics of J55 steel were analyzed in the O2/CO_(2)environment for different degrees of oxygen-reduction.As made evident by the experimental results,the corrosion products were mainly ferrous carbonate and iron oxide.In general,air injection increases the degree of oxygen reduction,from oxygen corrosion characteristics to CO_(2)corrosion-based characteristics.As a result,the corrosion product film becomes denser,and the corrosion rate is lower.

Predicting air pressure in drainage stack of high-rise building

It is necessary to understand the features of air pressure in a drainage stack of a high-rise building for properly designing and operating a drainage system. This paper presents a mathematical model for predicting the stack performance. A step function is used to describe the effect of the air entrainment caused by the water discharged from branch pipes. An additional source term is introduced to reflect the gas-liquid interphase interaction （GLII） and stack base effect. The drainage stack is divided into upper and base parts. The air pressure in the upper part is predicted by a total variation diminishing （TVD） scheme, while in the base part, it is predicted by a characteristic line method （CLM）. The predicted results are compared with the data measured in a real-scale high- rise test building. It is found that the additional source term in the present model is effective. It intensively influences the air pressure distribution in the stack. The air pressure is also sensitive to the velocity-adjusting parameter （VAP）, the branch pipe air entrainment, and the conditions on the stack bottom.

Low-temperature oxidation of light crude oil in oxygen-reduced air flooding

Light crude oil from the lower member of the Paleogene Xiaganchaigou Formation of Gaskule in Qinghai Oilfield was selected to carry out thermal kinetic analysis experiments and calculate the activation energy during the oil oxidation process.The oxidation process of crude oi l in porous medium was modeled by crude oil static oxidation experiment,and the component changes of crude oil before and after low-temperature oxidation were compared through Fourier transform ion cy-clotron resonance mass spectrometry and gas chromatography;the dynamic displacement experiment of oxygen-reduced air was combined with NMR technology to analyze the oil recovery degree of oxygen-reduced air flooding.The whole process of crude oil oxidation can be divided into four stages:light hydrocarbon volatilization,low-temperature oxidation,fuel deposition,and high temperature oxidation;the high temperature oxidation stage needs the highest activation energy,followed by the fuel deposition stage,and the low-temperature oxidation stage needs the lowest activation energy;the concentration of oxygen in the reaction is negatively correlated with the activation energy required for the reaction;the higher the oxygen concentration,the lower the average activation energy required for oxidation reaction is;the low-temperature oxidation reaction between crude oil and air generates a large amount of heat and CO,CO_(2) and CH4,forming flue gas drive in the reservoir,which has certain effects of mixing phases,reducing viscosity,lowering interfacial tension and promoting expansion of crude oil,and thus helps enhance the oil recovery rate.Under suitable reservoir temperature condition,the degree of recovery of oxygen-reduced air flooding is higher than that of nitrogen flooding for all scales of pore throat,and the air/oxygen-reduced air flooding de-velopment should be preferred.

Applicable scope of oxygen-reduced air flooding and the limit of oxygen content

The mechanisms of oxygen-reduced air flooding(ORAF)and the explosion limit and the corrosion control approaches were studied based on the pilots of oxygen-reduced air flooding(ORAF)in the Dagang,Changqing and Daqing oil fields in China.On the foundation of indoor investigations and pilots,the explosion limits,oxygen reduction limits and corrosion control approaches were clarified.When the temperature of reservoir is equal to and higher than 120℃,there is a violent reaction between oxygen and crude oil,that means the effect of low temperature oxidation would be fully taken use of to enhance oil recovery by air flooding directly;nitrogen dominated immiscible flooding with oxygen-reduced air should be applied in cases where reservoir temperature is below 120℃ with little oxygen consumption and little heat generated.The oxygen-reduced air flooding is suitable for 3 types of reservoirs:low permeability reservoir,water flooding development reservoir of high water-cut and high temperature and high salinity reservoir.In the process of development,in order to ensure safety,the oxygen reduction limits should be controlled fewer than 10%,while oxygen-reduced air can obviously reduce the corrosion rate of pipes;The surface pipelines and injection wells don’t need to consider about oxygen corrosion with no water,special materials and structure of pipe or corrosion inhibitor can be applied to the surface pipelines and injection wellbores with water.Air/oxygen-reduced air is a low-cost displacement medium and it could be applied in many special conditions of low permeability reservoir for energy supplement,huff and puff and displacement,that means oxygen-reduced air flooding has become the most potential strategic technology in 20 years.

Risk assessment of gas control and spontaneous combustion of coal under gas drainage of an upper tunnel

The adjustment of the gas drainage rate has an immediate impact on air leakage in gob,thus resulting in the change of self-heating of coal.While regulating the gas drainage parameters,the risk of spontaneous combustion of coal should be considered.The risk assessment of gas control and spontaneous combustion of coal under gas drainage in a tunnel was investigated at different gas drainage rates.The distributions of the air volume along the working face,the gas management effects and the width of the oxidation zone were subjected to risk analysis.As the simulation results showed,with increasing gas drainage rate,although the safety of gas dilution by ventilation was assured,the intensifying air leakage caused the oxidation zone to move into the deeper gob and led to an increase in the width of the oxidation zone.A risk assessment method was proposed to determine a suitable gas drainage rate for the upper tunnel.The correctness of the risk assessment and the validity of the numerical modelling were confirmed by the field measurements.

输水管线空气阀进排气孔径的合理选择

输水管线空气阀进排气孔径的选择,包括防水锤型空气阀低压进排气孔、缓冲板小排气孔和高压微量排气孔,不仅影响输水的安全性,而且严重影响工程投资。为了合理选择各种类型空气阀进排气孔径,本文首先提出了气体流量与流量系数、孔径、气压的函数关系,以及输水管液柱弥合水击压力与输水管直径、水击波速和空气阀流量改变量的函数关系;然后,建立了空气阀进排气孔径与输水管线充水和排水流速、负压控制要求及水击压力之间的函数关系,同时考虑了管材刚度和位置高程的影响。最后,分别以重力流输水管线和泵站加压输水管线为例,应用所得理论公式分别计算确定了复合式空气阀和防水锤型空气阀进排气孔孔径,结果表明按照本文公式确定的空气阀进排气孔径,不仅比按照常规经验确定的空气阀孔径小得多,而且可以有效削减输水管的液柱弥合水击压力。

数字胸腔引流系统在肺切除术中的应用价值

肺切除术后,胸腔引流管理是决定患者术后病程的关键,延迟拔管影响恢复速度和住院时间。传统胸腔闭式引流瓶已被广泛应用于相应患者,但存在一定局限性,尤其是肺切除术后存在肺漏气时,通常面临着长期不能拔除胸腔闭式引流管的风险。数字胸腔引流系统因其独特的优势可加快肺部漏气的愈合、减少胸腔引流量,进而缩短住院时间,其效果在多项研究中都得到了验证,本文就数字胸腔引流系统在肺切除术中的应用价值进行综述,并就其进一步有效应用进行讨论。

下向低浓钻孔“抽-注”排水排渣抽采一体化技术研究

为了防止永夏矿区陈四楼煤矿煤与瓦斯突出事故的发生,在采用水力排渣钻孔进行抽采瓦斯时,发现在钻孔内存在着大量的水和煤渣,堵塞了煤体内部的孔隙通道,对煤层瓦斯运移和钻孔孔壁的稳定性产生不利影响,从而严重影响了瓦斯抽采的效果。针对煤矿急需解决的俯孔排水排渣问题,提出采用压风吹孔技术,将孔内水和煤渣带出孔外,疏通钻孔堵塞通道。该技术在陈四楼煤矿井下现场应用效果良好,吹孔后钻孔平均在抽浓度由11.86%提升到了18.73%~56.38%,低浓钻孔提升效果明显;代替了以往水力排渣钻进技术,达到高效抽采瓦斯、保证煤矿安全生产的目的,对钻孔抽采瓦斯过程中能够及时排出水和煤渣有一定指导意义。在此基础上,形成的一套下向低浓钻孔“抽—注”排水排渣一体化技术及工艺,为下向低浓钻孔排水排渣工作提供参考借鉴。

气动降水技术在地基处理施工中的应用

在吕四港环抱式港池东港区基础设施工程(一期)Ⅰ标段基础处理施工中,特殊地基处理施工采用了气动降水施工技术,取消了传统管井降水法对潜水泵的使用,减少了施工现场安装配电箱和铺设电缆的工作,节省了潜水泵、配电箱及电缆等的工程造价和用电费用,减少了用电安全隐患,提高了大面积地基处理的降水施工效率。

橡胶坝积气和尾水故障分析及抽排系统设计

充水式橡胶坝在充水后坝袋内顶部常有积气无法彻底排除,塌坝泄洪时坝袋底部常有尾水无法彻底排除。为解决这两项常见故障,在分析故障产生的原因及可能引发的一系列后果的基础上,发明了橡胶坝积气和尾水抽排系统,提出了抽排管路、抽排动力装置和控制系统的概念设计原理和方法。通过典型应用实例验证了该系统能有效排除积气和尾水故障及其引发的一系列问题,保障橡胶坝工程能够以最大高度蓄水,以最大过水断面泄洪,为橡胶坝工程精细化设计及改进传统设计方案提供了创新思路。

张化厂固废堆场设计方案分析

氯化钡是一种重要的化工原料,其生产过程中产生了大量的钡渣,属于危险固体废物。对周边环境造成严重污染的同时,对于人体也会产生不同程度的损害。以张化厂固体堆场设计为例,依托该场地调研情况和地质情况,根据生态环境部发布的《危险废物填埋污染控制标准》(GB 18598—2019)中要求,制定了切实可行的固废堆场设计和实施方案,解决了场地有限、废渣占地面积大等问题,最大限度利用了现有场地,减少了工期。

空地一体技术在地下暗河探测中的应用研究

地下排水管涵是城市排水的主要渠道之一,掌握地下排水管涵信息对于城市防汛具有重要意义。受拆迁、道路改造施工等影响,地下排水管涵的部分井盖、井筒遭到掩盖、掩埋,使其成为难以探明的地下暗河。针对现场条件复杂的地下暗河,单一探测技术难以实现地下暗河的完整探测。因此,采用了测量型无人机、全地形机器人、三维激光扫描仪和GNSS-RTK协同作业的方案,形成了一种空地一体测绘技术,实现了测区地形、地下暗河的精确测绘,提高了城市疑难地下暗河的作业效率和数据质量。

关于附建式人防地下室给排水设计的探讨

人防地下室是城市建筑体系中不可或缺的一环,用于增强战争时期和应急情况下城市的自我保护能力。其功能形式多样,防护能力和效果也各不相同。本文将以附建式人防地下室给排水设计作为研究对象,通过引用相关规范条文和设计实例,深入研究人防地下室给排水设计的关键技术和实际应用。

地铁风水电安装质量控制——以南京轨道交通6号线为例

以地铁建设工程中的风水电工程为出发点,依托南京轨道交通6号线工程,深入研究了通风空调、给排水与消防和低压配电照明的施工方案及技术措施,同时对风水电设备安装问题,提出了针对性的质量控制措施。

川渝地区含硫深井气举技术研究及应用

深层碳酸盐岩气藏占四川盆地天然气资源的59%,已开发气藏普遍受水侵影响,气藏具有埋藏深、高温、高压、含硫、井筒条件复杂等特点,导致气举技术在该类气藏中应用时面临设计方法缺失,工具性能不足等系列问题。针对上述问题,通过优化设计方法、研制高压气举阀及排水采气工具等技术攻关,并进行实际应用,形成了高压深井气举、免修井排水采气等一系列含硫深井排水采气新技术。研究成果表明:(1)在常规气举设计基础上,引入地层吸液指数,建立基于地层—井筒耦合流动的高压深井气举设计方法,该方法增加顶阀下入深度,气举阀布阀支数减少60%,降低阀间干扰;(2)通过气举阀结构优化设计,研制了充氮压力35 MPa、抗外压90 MPa的高压耐蚀气举阀,可满足6 000 m井深范围内酸化—气举联作和井下长期工作的需求;(3)设计以单向注入通道为核心的气举封隔器构建单向工艺通道,以自验封和悬挂为核心的气举封隔器重建工艺通道,研发了预置式、隔离式、跨隔式排水采气工具,满足永久式封隔器在气井完井不同阶段开展排水的技术需求,实现免修井排水采气。在川渝地区含硫深井中现场应用300余井次,应用井深超6 000 m,最大排水量达650 m~3/d,有效地解决了川渝地区气田含硫、高压、深井排水采气问题。

挖金湾煤业瓦斯治理技术应用研究

针对挖金湾煤业井下通风风量紧张,瓦斯涌出量急剧提升的现象,采用分源动态预测的方法对挖金湾煤业井下瓦斯涌出量进行了预测分析,通过对瓦斯压力、含量以及通风阻力等指标的测定,了解井下瓦斯状况,找出工作面瓦斯主要来源,并对井下瓦斯涌出量进行预测分析。通过制定瓦斯抽放及井下通风技术方案,提升了瓦斯抽采时间与浓度,提高瓦斯抽采率为73%,保证工作面回风流瓦斯浓度在0.4%以下,回采面上隅角与高位孔处浓度保持在4%~12%,符合煤矿井下安全高效生产要求。

山区段天然气长输管道水压试验气阻问题探析

试压是长输管道建设过程中的重要施工工序。山区段因地势问题容易产生高落差,水压试验排水过程中容易出现气阻现象,使水压试验成为试压施工中的一大难题。结合山区段长输管道建设项目元坝-德阳输气管线工程,分析气阻产生的原因,并提出了相应的预防措施和产生气阻时的解决办法。这为山区大落差地段管道建设提供了参考。

区域排涝工程中的环境保护措施研究

随着城市化的快速发展,区域排涝工程成为解决城市内涝和改善水环境的重要手段,然而,这些工程在解决水患问题的同时,也可能对环境造成一定的影响。本文从水环境、生态环境、环境空气污染防治以及水土保持等多个方面,探讨如何在排涝工程中实施有效的环境保护措施。通过分析现有排涝工程的环境保护现状,提出一系列改进措施,旨在实现排涝效果与环境保护的双重目标。

浅谈地下人防工程通风给排水设计要点

随着我国经济的快速发展,人们对人民防空的认识在不断提高,地下人防工程建设的规模增长迅猛。地下人防工程的开发、利用和维护管理都离不开内部环境的保障,通风和给排水系统是工程内部环境保障的重要组成部分,由于地下人防工程通风和给排水的专业性,对从业人员提出了特殊要求,由于历史和涉密方面的限制,相关文献资料匮乏。本文介绍了地下人防工程通风和给排水设计的要点,旨在为地下人防工程通风给排水设计提供参考。