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.

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.

Oxidization characteristics and thermal miscible flooding of high pressure air injection in light oil reservoirs

Physical modeling,numerical simulation and field case analysis were carried out to find out the subsurface thermal oxidation state,thermal oxidation front characteristics and production dynamic characteristics of high pressure air injection thermal oxidation miscible flooding technology.The lighter the composition and the lower the viscosity of the crude oil,the lower the fuel consumption and the combustion temperature are.The thermal oxidation front of light oil and volatile oil can advance stably,and a medium-temperature thermal oxidation stable displacement state can be formed in the light oil reservoir under high pressure conditions.With strong thermal gasification and distillation,light oil and volatile oil are likely to form a single phase zone of gasification and distillation with thermal flue gas at the high-temperature and high-pressure heat front,finally,an air-injection thermal miscible front.In light oil reservoirs,the development process of high-pressure air-injection thermal miscible flooding can be divided into three stages:boosting pressure stage,low gas-oil ratio and high-efficiency stable production stage and high gas-oil ratio production stage.Approximately 70%of crude oil is produced during the boosting pressure stage and low gas-oil ratio high-efficiency and stable production stage.

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.

An online physical simulation method for enhanced oil recovery by air injection in shale oil

In order to understand the mechanism of air flooding shale oil, an online physical simulation method for enhanced shale oil recovery by air injection was established by integrating CT scanning and nuclear magnetic resonance(NMR). The development effect of shale oil by air flooding under different depletion pressures, the micro-production characteristics of pore throats with different sizes and the mechanism of shale oil recovery by air flooding were analyzed. The effects of air oxygen content, permeability, gas injection pressure, and fractures on the air flooding effect in shale and crude oil production in pores with different sizes were analyzed. The recovery of shale oil can be greatly improved by injecting air into the depleted shale reservoir, but the oil displacement efficiency and the production degree of different levels of pore throats vary with the injection timing. The higher the air oxygen content and the stronger the low-temperature oxidation, the higher the production degree of pores with different sizes and the higher the shale oil recovery. The higher the permeability and the better the pore throat connectivity, the stronger the fluid flow capacity and the higher the shale oil recovery. As the injection pressure increases, the lower limit of the production degree of pore throats decreases, but gas channeling may occur to cause a premature breakthrough;as a result, the recovery increases and then decreases. Fractures can effectively increase the contact area between gas and crude oil, and increase the air sweep coefficient and matrix oil drainage area by supplying oil to fractures through the matrix, which means that a proper fracturing before air injection can help to improve the oil displacement effect under a reasonable production pressure difference.

INFLUENCE OF SEA－AIR INTERACTION ON THEDISCHARGE OF FLOOD SEASON IN THEUPPER REACHES OF THE CHANGJIANG RIVER

ＩＮＦＬＵＥＮＣＥＯＦＳＥＡ－ＡＩＲＩＮＴＥＲＡＣＴＩＯＮＯＮＴＨＥＤＩＳＣＨＡＲＧＥＯＦＦＬＯＯＤＳＥＡＳＯＮＩＮＴＨＥＵＰＰＥＲＲＥＡＣＨＥＳＯＦＴＨＥＣＨＡＮＧＪＩＡＮＧＲＩＶＥＲＺｈａｎｇＸｉｎｐｉｎｇ（章新平）（ＬａｎｚｈｏｕＩｎｓｔｉｔｕ...

空气驱油可燃气体爆炸安全风险分析

目的目前,安全问题仍然是限制空气驱大规模应用的主要原因,为此进行了针对其爆炸极限计算方法的研究。方法通过对6种可燃气体的单组分计算方法、单组分文献值与2种多组分计算方法进行组合,得到了14种计算组合,将其与国内某油田3口井的爆炸实测值进行比较,以判断哪种组合适应性最好。结果含碳原子单组分燃气计算法与多组分燃气计算中查图-理·查特里修正法组合得到的计算结果整体误差相对较小,更符合爆炸极限实测值。结论可为C_(1)~C_(3)轻烃体积分数达90%以上的井流物的爆炸极限理论计算方法的选择提供参考。

微气泡驱与空气泡沫驱技术差异性及调整对策

微气泡驱与空气泡沫驱技术经过矿场试验,在低渗高含水率油藏具有较强的适应性,但对于两种气驱机理认识及技术政策调整思路方式上仍存在短板。本文通过深入研究两种气驱技术机理、驱替特征的差异性,结合现场动态调整效果,认为微气泡驱以物理发泡为主,驱替特征呈气液同驱,采取低气液比(1.0∶3.0)的技术政策,空气泡沫驱以化学发泡为主,驱替特征呈气驱为主液相为辅,采取高气液比(3.0∶1.0)的调整思路,并提出了气驱分注试验的调整对策,控水增油效果显著提升,提高采收率趋势良好。对同类油藏两种气驱技术调整界限具有一定的借鉴指导意义。

遥感技术在洪涝灾害防御中的前沿应用与面临挑战

及时全面掌握洪涝发生的关键信息是洪涝灾害防御的基础,将遥感技术与传统监测技术相结合,形成“天空地”一体化的立体监测体系,可以实现宏观观测与重点监测的互补与协同,有利于洪涝灾害的监测、预报和预警,显著提高洪涝灾害防御能力。遥感技术可应用于水体提取、水位测算、降水测量、流量估算、洪涝模拟、灾害损失估计等,但在监测数据可用性、监测方法有效性等方面还有很多问题需要解决。

基于水气两相流的海拔高程对某电站溢洪道泄洪雾化的影响分析

海拔高程增加所引起的气象条件的改变会对泄洪水舌的运动产生影响,进而影响泄洪雾化风场及雨场的时空分布。为此,基于水气两相流理论,考虑不同海拔高度的环境压强、温度、粘滞性及空气密度等参数的变化,采用数值模拟的方法研究了海拔高程对泄洪雾化的影响。结果表明,相同泄洪条件下,泄洪稳定后的压强值随海拔升高无明显增加趋势,然而海拔越高,水舌空中运动所受空气阻力越小,相同条件下落水点压强增幅越大;温度降低带来的水的粘滞性增加对水雾运动影响较小,海拔高程越高,雾化风速到达最大值的时间越早,所能达到的最大值也越大;泄洪稳定时近地表雾化降雨强度随海拔高程的增加而增大,与海拔高程呈近似线性关系,此外强降雨范围随海拔的升高而逐渐扩大。

空气热混相驱矿场试验中的工艺配套研究与实施

空气热混相驱是油田提高采收率的前沿技术之一,为进一步探索低渗透油藏提高采收率的工艺技术,结合A区块油藏特征,开展空气热混相驱工艺技术先导试验。本文主要针对空气热混相驱工艺现场试验所存在的技术难点,从注入井井筒、采出井井口、地面工艺流程、现场实施工艺、数字化监控等方面进行研究及配套,确保空气热混相驱工艺试验顺利实施,为后期空气热混相驱在低渗透油藏扩大试验提供技术支撑。

玉果油田果8区块减氧空气驱低温氧化对采收率的影响

注减氧空气是低渗透油藏有效的开发手段,减氧空气可在地层条件下与原油发生低温氧化反应,提高采收率。针对玉果油田果8区块目前减氧空气驱提高采收率机理认识不完善的问题,采用等温氧化实验和长岩心驱替实验探究原油氧化过程和生成物质对提高采收率的影响。等温氧化实验结果表明,稀油的低温氧化过程产生了沉积物质,随着温度升高,氧化程度明显提高,89℃时原油氧化生成重质组分沉积量为1.25×10^(-3)g/g,100℃时为3.43×10^(-3)g/g,120℃时为5.02×10^(-3)g/g。长岩心驱替实验结果表明,不同氧化温度下重质组分沉降对采收率存在影响,随着温度升高,气窜时机变晚,波及效果变好,最终采收率有所提高,温度为89℃、100℃和120℃时的最终采收率分别为52.77%、58.89%和65.23%。

驮英水库泄洪隧洞方案比选

驮英水库泄洪隧洞方案选用“龙抬头”连接型式(不共用进水口布置方案)与短斜坡连接型式(共用进水口布置方案)等两种方案。本文从结构安全、运行调度、工程施工、工程投资等方面进行比选,推荐短斜坡连接型式(共用进水口布置)方案为实施方案。

致密油藏化能自养微生物生长规律及其氧化活性研究

为了探明致密油藏化能自养微生物利用催化岩石耗氧功能辅助空气驱提高采收率的机理,针对注气开发致密油藏注氧安全问题,开展了对致密油藏化能自养氧化亚铁硫杆菌的富集筛选,并探究了氧化亚铁硫杆菌的生长规律以及其作用氧化矿物中亚铁、硫以及其生物活性等效能,结果表明:1)高生物量活性的氧化亚铁硫杆菌可生长代谢产生酸性环境(pH值小于2),从而加速了矿物中亚铁和硫的氧化还原;2)反应体系中亚铁氧化率达到91%,硫氧化率为57.8%;3)岩石矿物质亚铁和硫的氧化活性与微生物的生物活性成正相关关系;4)油藏化能自养微生物通过催化矿物中亚铁氧化耗氧,介导硫氧化还原产生SO_(4)^(2-),促使体系pH值下降,酸性环境利于矿物溶蚀分解,进而加速微生物催化岩石耗氧或矿化速率,达到耗氧增渗驱油目的。该研究成果,对化能自养微生物强化减氧空气复合驱技术现场应用提供指导意义。

“双碳”目标下绿色提高采收率技术路径与实践

“碳达峰、碳中和”目标下,油气生产行业在持续增产稳产、确保能源安全的前提下,需要加强负碳、零碳和低碳技术创新,促使产业转型升级。新技术、新工艺、新材料的研发赋予了绿色低碳提高原油采收率技术新的内涵。理论研究与矿场实践表明:CO_(2)驱油、CO_(2)压裂增产、空气(减氧空气或N_(2))驱油、生物质基驱油、微生物基驱油技术碳减排效应明显,为提高原油采收率领域碳中和提供了新路径。未来将继续优化绿色提高原油采收率技术路径,构建新一代绿色低碳提高采收率工程技术体系,开展全流程全生命周期碳减排潜力研究,探索绿色低碳提高采收率技术定量表征方法。

基于实验的水驱后空气泡沫驱替特征研究

当油田处于特高含水时期时,传统的采油技术无法继续保持高产、稳产,采油速率下降,成本上升。空气泡沫驱替将空气驱替采油技术和泡沫驱替采油技术有机结合在一起,可以很好地解决传统采油后期采收率下降等问题,具有良好的应用前景。利用填砂管装置研究不同渗透率下空气泡沫驱替的渗流场的变化情况。结果表明,渗透率越高,空气泡沫驱替的效果越好;在空气泡沫驱替过程中段塞堵塞会导致压力变化较大;数值模拟显示空气泡沫驱替具有启动、驱替、突破三个阶段,其中驱替阶段为提高采收率的关键阶段。研究结果可以为油田中后期特高含水时,转空气泡沫驱替提供参考。

延长低渗透油藏CO_(2)驱油参数优化数值模拟研究

CO_(2)驱油在特低渗油藏中具有较好的应用效果,是提高采收率的重要方法。以延长油田H区块为研究对象,分析目前注水开发存在的问题,根据动静态参数将井组分成2类,应用数值模拟方法,分别对2类井组CO_(2)驱油的开发方式、注气时机、注气速度、井底流压及气水交替周期进行了优化。结果表明,以气水比1∶1且气水交替的方式在油井含水40%~60%时注气效果最佳。第1类注气井组的最优注气速度为10~15 t/d,井底流压1 MPa,气水交替周期60天;第2类注气井组最优注气速度为5~10 t/d,井底流压2 MPa,气水交替周期30天。该研究结果对H区块低渗油藏现场注CO_(2)驱油设计具有重要的指导作用。

双高油藏“二三结合”提高采收率技术应用

特低渗油藏进入双高开发阶段后一次井网适应性变差,水驱油效率大幅下降,大量剩余油及残余油仍未驱替,围绕剩余油分布零散、死油区动用难问题,开展二次加密调整井网转换结合空气驱三次采油综合提高采收率技术现场试验,近五年现场实践表明,试验区开发效果显著提升,自然递减、含水率上升率呈负增长,阶段动态采收率提高3.6%,预测最终采收率提高8.5%以上。

页岩油注空气提高采收率在线物理模拟方法

为探索页岩油注空气驱油机理,建立了基于CT扫描和核磁共振技术的页岩油注空气提高采收率在线物理模拟方法,研究了不同衰竭压力下页岩油空气驱开发效果、不同大小孔喉微观动用特征和页岩油空气驱采油机制,分析了空气含氧量、渗透率、注入压力、裂缝对页岩注空气驱油效果和不同大小孔隙原油采出量的影响。研究表明,页岩储集层衰竭开采后注入空气可大幅提高页岩油采收率,但不同注入时机下驱油效率和不同级别孔喉动用程度存在一定差异。空气含氧量越高,低温氧化作用越强,不同大小孔隙动用程度越高,采收率越大。渗透率越高,孔喉连通性越好,流体流动能力越强,采收率越高。注入压力升高,孔喉动用下限减小,但易产生气窜现象导致突破提前,采收率先增大后减小。裂缝能加大气体与原油的接触面积,通过基质向裂缝供油提高空气波及系数和基质泄油面积,在合理生产压差下,注空气前进行适当的压裂改造有助于提高空气驱效果。