Displacement characteristics of CO_(2)flooding in extra-high water-cut reservoirs

Carbon dioxide(CO_(2))flooding is a widely applied recovery method during the tertiary recovery of oil and gas.A high water saturation condition in reservoirs could induce a‘water shielding’phenomenon after the injection of CO_(2).This would prevent contact between the injected gas and the residual oil,restricting the development of the miscible zone.A micro-visual experiment of dead-end models,used to observe the effect of a film of water on the miscibility process,indicates that CO_(2)can penetrate the water film and come into contact with the residual oil,although the mixing is significantly delayed.However,the dissolution loss of CO_(2)at high water-cut conditions is not negligible.The oil-water partition coefficient,defined as the ratio of CO_(2)solubility in an oil-brine/two-phase system,keeps constant for specific reservoir conditions and changes little with an injection gas.The NMR device shows that when CO_(2)flooding follows water flooding,the residual oil decreasesdnot only in medium and large pores but also in small and micro pores.At levels of higher water saturation,CO_(2)displacement is characterized initially by a low oil production rate and high water-cut.After the CO_(2)breakthrough,the water-cut decreases sharply and the oil production rate increases gradually.The response time of CO_(2)flooding at high watercut reservoirs is typically delayed and prolonged.These results were confirmed in a pilot test for CO_(2)flooding at the P1-1 well group of the Pucheng Oilfield.Observations from this pilot study also suggest that a larger injection gas pore volume available for CO_(2)injection is required to offset the dissolution loss in high water saturation conditions.

Influences of water treatment agents on oil-water interfacial properties of oilfield produced water

The emulsion stability of oilfield produced water is related to the oil-water interfacial film strength and the zeta potential of the oil droplets. We investigated the effects of water treatment agents （corrosion inhibitor SL-2, scale inhibitor HEDP, germicide 1227, and flocculant polyaluminium chloride PAC） on the stability of oilfield produced water. The influence of these treatment agents on oil-water interfacial properties and the mechanism of these agents acting on the oilfield produced water were studied by measuring the interfacial shear viscosity, interfacial tension and zeta electric potential. The results indicated that the scale inhibitor HEDP could increase the oil-water interfacial film strength, and it could also increase the absolute value of the zeta potential of oil droplets. HEDP played an important role in the stability of the emulsion. Polyaluminum chloride （PAC） reduced the stability of the emulsion by considerably decreasing the absolute value of the zeta potential of oil droplets. Corrosion inhibitor SL-2 and germicide 1227 could decrease the oil-water interfacial tension, whereas they had little influence on oil-water interfacial shear viscosity and oil-water interfacial electricity properties.

Preparation and Field Application of a Novel Micro-emulsion as Heavy Oil Displacement Agent

A novel micro-emulsion was prepared by mixing an oil-soluble viscosity reducer,which was screened to aim at improving the heavy oil properties of Shengli oilfield with water-soluble surfactant and co-surfactant.The static viscosity reduction and oil washing performance of the micro-emulsion were investigated,and the field application of the microemulsion used as heavy oil displacement agent was also reported.Results showed that the micro-emulsion exhibited excellent viscosity reduction performance for the studied heavy oil samples.When heavy oil was mixed with 0.5%of the micro-emulsion,a stable oil-in-water heavy oil emulsion could be formed.After the content of the micro-emulsion was increased to 3.0%,the oil removing rate reached up to 80%.Field application of the micro-emulsion to the Pai-601-Ping-115 well and the Pai-601-Ping-123 well was shown to be effective by increasing the periodic oil production up to 203 tons.

Mechanism of expanding swept volume by nano-sized oil-displacement agent

The effect of expanding swept volume by iNanoW1.0 nanoparticles in ultra-low permeability core was studied by low-field nuclear magnetic resonance(LF-NMR)technology,and the mechanism of expanding swept volume was explained by oxygen spectrum nuclear magnetic resonance(17O-NMR)experiments and capillarity analysis.The results of the LF-NMR experiment show that the nano-sized oil-displacement agent iNanoW1.0 could increase the swept volume by 10%-20%on the basis of conventional water flooding,making water molecules get into the low permeable region with small pores that conventional water flooding could not reach.17O-NMR technique and capillary analysis proved that iNanoW1.0 nanoparticles could weaken the association of hydrogen bonds between water molecules,effectively change the structure of water molecular clusters,and thus increasing the swept volume in the low permeable region.The ability of weakening association of hydrogen bonds between water molecules of iNanoW1.0 nanoparticles increases with its mass fraction and tends to be stable after the mass fraction of 0.1%.

Numerical modelling of the dynamic process of oil displacement by water in sandstone reservoirs with random pore structures

The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected area.Magnetic data(n=84)measured,processed and interpreted as qualitative and quantitatively.The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies.The magnetic values ranged from-137 nT to 2345 nT with a mean of 465 nT.Reduction to equator shows significant shifting of causative bodies in the southern and northern directions.Analytical signal map shows exact boundary of granitic bodies.Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines.Sudden decrease of magnetic values from 2042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence.Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well.Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m,respectively.Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0,1,2,and 3 and found depth ranges from<10 m to>90 m.Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.

表面活性剂对水驱普通稠油油藏的乳化驱油机理

为了研究乳化降黏驱油剂对不同渗透率的水驱普通稠油油藏的驱油效率和孔隙尺度增效机理,选取了烷基酚聚氧乙烯醚(J1)、α-烯基磺酸盐类表面活性剂(J2)、十二烷基羟磺基甜菜碱(J3)、J3与烷基酚聚氧乙烯醚羧酸盐复配表面活性剂(J4)作为驱油剂,开展了4种驱油剂一维驱油和微观驱油模拟实验,明确了乳化降黏驱油剂在孔隙尺度的致效机理。结果表明,降低界面张力对提高驱油效率的作用大于提高乳化降黏率。在油藏条件下,乳化降黏驱油剂需要依靠乳化降黏和降低界面张力的协同增效作用,才能大幅提高驱油效率。乳化降黏驱油剂的乳化能力越强、油水界面张力越低,驱油效率增幅越大。当化学剂乳化降黏率达到95%时,油水界面张力从10^(-1)mN/m每降低1个数量级,化学剂在高渗透和低渗透岩心中的驱油效率依次提高约10.0%和7.8%。乳化降黏驱油剂注入初期通过降低界面张力,使得高渗透岩心和低渗透岩心中的驱替压力分别为水驱注入压力的1/2和1/3,从而提高注入能力。注入后期大块的原油被乳化形成大量不同尺寸的油滴,增强原油流动性,提高驱油效率。乳化形成的界面相对稳定的稠油油滴,能暂堵岩石的喉道和大块稠油与岩石颗粒形成的通道。油滴的暂堵叠加效应,使高渗透和低渗透岩心的驱替压差分别为水驱压差的5.2倍和32.3倍,大幅提高了注入压力,从而扩大平面波及面积。降黏驱油剂驱油实现了提高驱油效率的同时扩大波及范围。研究结果为水驱稠油开发用驱油剂的研发提供参考,为大幅提高水驱普通稠油采收率奠定基础。

纳米驱油剂相渗特征及对页岩油开发方式的影响

纳米技术在非常规油气开发中应用前景广泛,有望成为新一代颠覆性开发技术。相渗作为驱替和渗吸的重要渗流特征需要加以研究。对页岩油岩心开展纳米剂、表面活性剂等不同驱渗介质相渗等实验,并进行拟合分析,可以发现:1)纳米剂的油相相对渗透特征指数n值显著降低,有利于提高油水流度,降低注入压力;2)低浓度纳米剂水相端点相对渗透率高于地层水,反映低浓度纳米剂水溶液流动性更强;3)纳米驱油剂相渗的两相区较油水相渗增加8.8%,幅度小,需要改进开发方式以进一步提高驱油效率;4)纳米剂通过驱替与渗吸相结合可以将驱油效率从36.67%大幅度提高到74.67%;5)周期驱替还能进一步改善开发效果,驱油效率比连续驱替提高14.1%(注入体积倍数0.478 PV)。该研究成果对页岩油补能、稳产、提采的开发方式优选具有重要指导意义。

适用于哈拉哈塘高温高盐岩油藏表面活性剂的研制及应用

为了研制出适用于哈拉哈塘油藏条件的表面活性剂驱油剂,对该储层地层流体及岩石润湿性进行了测试,基于此,采用二甲胺、全氟丁酸、氯丙烯、丙烯酰胺、对苯乙烯磺酸钠等为主要原料,合成了一种耐高温高盐含氟两性离子型高分子表面活性剂(GPHQ-2),并对其表面活性、润湿性以及洗油效率等进行了室内评价。实验结果表明,150℃、25×10^(4)mg·L^(-1)矿化度老化后的GPHQ-2仍能有效降低油水界面张力,可使岩心表面实现润湿反转,洗油效率可达43.4%,远高于常规石油磺酸盐的洗油效率(5.6%);GPHQ-2具有很好的驱油效果,可在水驱阶段原油采收率基础上提高22.84%;现场应用结果表明,目标井采取注GPHQ-2表面活性剂吞吐驱油措施后,日产油量从4.9t提升到8.9t,增产效果明显,且持续有效。说明GPHQ-2表面活性剂满足哈拉哈塘油藏提高采收率需求,并可对该类油藏表面活性剂增产提供理论和实践指导。

纳米材料在油田开发领域的研究及应用

可利用石油资源逐渐减少、开采难度在增大。纳米材料具有卓越的粒子尺寸和性能,通过表面改性还可在同一纳米材料上集成多种驱油功能,其被认为是解决传统提高采收率(EOR)技术所面临众多问题的潜在方案。本文主要介绍了纳米材料的制备与改性、种类,综述其在油田开发各阶段的应用与研究进展,特别是EOR方面。结合油田开发需求与纳米技术的优势,指出了纳米颗粒在EOR过程中应用的挑战和未来研究的机遇。

低渗透致密储层用改性纳米驱油压裂液

低渗致密油藏作为未来我国非常规油气资源勘探开发的主要新领域,是接替常规油气资源、支撑油气革命的重要力量。纳米流体在低渗致密油藏中驱油效果较好,但纳米粒子作为助剂在水溶液中易堵塞地层微纳米孔喉,纳米粒子的团聚问题一直难以解决。通过水溶液引发自由基共聚法,以丙烯酰胺(AM)、2-丙烯酰胺-2-甲基丙磺酸(AMPS)和N-12-(2-丁烯酰氧基)正十二烷基-N,N,N-三甲基溴化铵(MEDDA)为底物单体,引入改性纳米SiO_(2)合成了一种改性纳米SiO_(2)/聚合物驱油压裂液。借助红外光谱仪、核磁共振氢谱仪和透射电镜等方法分析表征改性纳米SiO_(2)/聚合物驱油压裂液稠化剂;再将渗吸驱油实验和核磁共振技术相结合来研究改性纳米SiO_(2)/聚合物驱油压裂液的驱油效果。研究结果表明,聚合物体系中的改性纳米SiO_(2)最优加量为1.5%。通过对比不同改性纳米SiO_(2)加量的改性纳米SiO_(2)/聚合物驱油压裂液在饱和油岩心片表面的接触角,证明改性纳米SiO_(2)/聚合物驱油压裂液驱油效率的提升是通过改善岩石表面润湿性来实现的。相较于未添加改性纳米SiO_(2)的聚合物驱油压裂液体系,添加改性纳米SiO_(2)(1.5%)/聚合物驱油压裂液的自发渗吸效率接近40%,渗吸效率提升超过1倍。通过核磁共振成像结果也可明显看出:随着渗吸时间的延长,添加了改性纳米SiO_(2)的驱油压裂液中的岩心原油饱和度大幅降低,渗吸速度明显加快,渗吸效果显著。

低渗透致密油藏压裂驱油剂润湿性评价及效果

针对低渗透致密油藏压裂驱油剂的润湿性评价问题,分析现有接触角法的误差及不确定性,提出了评价压裂驱油剂润湿性的改进方法,采用润湿倾向指数,即驱油剂与蒸馏水在亲水/油表面的润湿接触角的比值来表征压裂驱油剂的润湿性改变方向和程度。结果表明,用接触角和接触角变化的最大值反映驱油剂对储层润湿性改变方向和能力都存在一定的不确定性。亲水表面的性质非常稳定,润湿接触角偏差较小,但亲油表面的润湿接触角偏差较大。蒸馏水与亲水/油表面润湿接触角的相对平均偏差分别为0.281%、8.929%。另外,部分驱油剂在亲水/油表面的接触角最大变化值差异不明显。用润湿倾向指数可较好地表征驱油剂的润湿性改变程度。润湿倾向指数不确定度远小于接触角不确定度。0.2%磺酸盐类驱油剂、聚氧乙烯醚类驱油剂、氟碳类驱油剂在亲水表面的接触角(润湿30 s)不确定度分别为1.24、3.11、0.64,而水润湿倾向指数不确定度分别为2.48×10^(-2)、6.33×10^(-2)、1.76×10^(-2)。通过Amott方法,测得7种压裂驱油剂作用下天然岩样的水湿指数。该水湿指数从大到小的排序与用接触角法测得的水润湿倾向指数从小到大的顺序一致。两种方法的测试结果进一步证实了使用润湿倾向指数的准确性和优越性。该方法有利于快捷地评价压裂驱油剂对储层润湿性的改变能力,优选低渗透致密油藏压裂驱油剂。

致密油藏高起泡强渗吸驱油剂的构建及性能研究

针对致密油藏经“水平井+体积压裂”技术改造开发后井间流体发生窜流及致密油采收率偏低的问题,研制了一种高起泡强渗吸纳米驱油剂。以自研双子表面活性剂BD-2、CHSB、LAB为纳米驱油剂的主剂,通过三元相图法得出纳米驱油剂的配方为:25%BD-2+10%LAB+4.5%CHSB+5%油溶性增效剂+15.5%小分子醇。对纳米驱油剂界面性能、润湿调节性能、渗吸性能、起泡性能、耐温抗盐性能、增容性能、静态洗油性能进行评价,同时研究了驱油剂对岩心中致密油动用情况。结果表明,在2000 mg/L下,纳米驱油剂YYC-2与玛湖原油的界面张力可达6.318×10^(-3)mN/m,可将接触角降低至20.36°,渗吸采出程度达到21.37%;在90℃、10×10^(4)mg/L NaCl和5×10^(3)mg/L CaCl_(2)矿化度下均能达到超低界面水平,最大增容粒径可达593.6 nm,静态洗油效率最大可达80%左右。高压压汞曲线与核磁共振曲线的转换系数C为791 nm/ms,能启动岩心最小孔隙直径为20.0304 nm。

一种适用于油基钻井液堵漏水泥浆体系研发

水泥浆堵漏是解决恶性漏失的有效措施之一,但是水泥浆在油基钻井液中难以凝结固化,致使其使用受限。从油基钻井液污染水泥浆机理出发,开发油水置换剂,并对胶凝体系和配套降失水剂和缓凝剂进行研选,开发油基钻井液堵漏水泥浆体系,并对水泥浆体系性能进行评价。研究表明:通过微乳液共聚法(即油相和水相同时引发聚合)制备了油水置换剂,在油井水泥中加入油水置换剂后,钻井液与水泥浆的相容性良好,水泥浆与油基钻井液体积比为50∶50的混浆体系在50℃条件下养护时间24 h,强度可达2 MPa左右,且油水置换剂具有很好的广谱性能,现场不同区域取的不同类型的油基钻井液,均发展强度;研选了配套降失水剂BXF-200LL和缓凝剂GH-9,开发出了适用于油基钻井液堵漏的水泥浆体系,油水置换剂对水泥浆稠化没有不良影响,且抗温达120℃。

高磷赤铁矿直接还原过程中不同添加剂脱磷的性能对比及分子动力学模拟研究

通过试验对比了高磷赤铁矿直接还原焙烧过程中不同添加剂CaCO_(3)、Na_(2)CO_(3)、CaF_(2)的脱磷性能,结果表明,Na_(2)CO_(3)的脱磷性能更好,CaCO_(3)次之。利用分子动力学模拟统计计算使用3种不同添加剂后体系在焙烧过程中的桥氧分布和氧原子均方位移,查明了高磷赤铁矿直接还原过程中CaCO_(3)、Na_(2)CO_(3)、CaF_(2)的脱磷机制,结果表明,添加剂脱磷的作用机制是提高体系中自由氧含量或提高体系中氧原子的均方位移,减少体系中Si、P共用氧原子,从而抑制磷灰石的还原;添加剂脱磷性能与体系中氧原子均方位移呈正相关的规律。

驱油剂对无碱三元复合驱采出液乳化稳定性影响

为探究无碱三元驱油剂对于采出液乳化稳定的机理,为采出液处理提供依据。对游离水中含油量、油水动态界面张力、液滴界面寿命与油滴粒径分布状态及粒径随驱油剂含量的变化进行了研究。加入低浓度表面活性剂(100 mg/L)时,动态界面张力、界面寿命、油滴粒径均显著降低,水中含油量显著增加,随着表面活性剂浓度增加,动态界面张力、界面寿命、粒径、含油量变化均不明显;随着NaCl浓度上升,动态界面张力与界面寿命变化不明显,油滴粒径变大,水中含油量增加;随着聚合物浓度增加,动态界面张力与界面寿命变化不明显,对于油滴粒径与含油量出现双重作用。这表明表面活性剂与NaCl有利于乳化稳定,但表面活性剂作用远大于NaCl;低浓度聚合物不利于乳化稳定,随着浓度增加,有利于乳化稳定。

深度调剖化学剂驱油机理及实验研究

基于分子设计及化学反应合成了化学驱油剂HPEN体系,分析了催化剂质量分数、反应温度、反应时间及投料比等因素对反应产率的敏感性。通过正交方案设计优选了HPEN的合成条件,岩心驱替实验评价了HPEN与磺酸盐复配体系的驱油特性,选取目标区块进行了现场应用实验。结果表明:HPEN适宜的合成条件为催化剂质量分数5%、反应温度100℃、反应时间6 h、脂肪醇聚氧乙烯醚与磺酸盐投料比1∶1.5。无机盐离子的存在会不同程度影响HPEN溶液体系的界面张力。1.0%的HPEN与磺酸盐按质量比3∶1复配时效果最佳,此时体系抗温能力为130℃,高矿化度溶液体系其界面张力仍处于10-2 mN·m^(-1)数量级范围。复配体系可显著提高现场原油采收率,实现老井日均产油4 t、日均产液16 m^(3)的效果。

适用于特稠油的耐高温高盐纳米二氧化硅降黏驱油剂

乳化降黏是稠油提高采收率的关键技术之一。普通降黏剂无法同时满足特稠油热采时的高温与高矿化度要求,导致降黏剂失活、降黏效果差、采收率低。以纳米硅溶胶、两亲型分散剂、修饰剂硅烷偶联剂、增效剂两亲型表面活性剂等为原料,制得纳米降黏驱油剂,表征了驱油剂的微观结构,评价了驱油剂对特稠油的降黏效果、耐温耐盐性能、吸附性能和驱油效果。结果表明,驱油剂配方组成为:50%SiO_(2)+40%分散剂+4.2%表面修饰剂+5.8%增效剂。驱油剂粒径约50 nm,粒径分布均匀,分散性良好。1%驱油剂未老化前,对特稠油的降黏率达84.99%,在矿化度为15 g/L、350℃下老化2 h后的降黏率为83.62%,降黏性能保持率为98.39%。驱油剂可使砂岩表面由疏水性转变为亲水性。在50℃、液固比为10∶1、平衡吸附时间为15 h的条件下,驱油剂在油砂表面的静态吸附量为1.377 mg/g砂;1%驱油剂在填砂管的动态吸附量为0.745 mg/g砂,在油藏中的吸附损失较低,符合化学驱对表面活性剂的吸附损失要求。在一维驱替实验中,驱油剂的驱油效率比普通蒸汽驱提高了26.7百分点,在350℃、老化2 h后的驱油性能保持率为97.0%。纳米降黏驱油剂具有良好的降黏效果、耐温耐盐性能、吸附性能和驱油效果,可降低驱油成本,有效提高特稠油的热采开发效果。

改性纳米二氧化硅耐温微球调驱剂的合成与性能评价

以丙烯酰胺(AM)、丙烯酸(AA)、2-丙烯酰胺-2-甲基丙磺酸(AMPS)为合成原料,以纳米二氧化硅为载体,γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(KH-570)为改性试剂,采用乳液聚合法制备了一种具有“核-壳”结构的改性纳米二氧化硅微球,并对其化学结构、溶胀倍率以及微观形貌进行了表征;同时,研究了在不同溶胀时间、温度以及矿化度条件下的膨胀性能;通过填砂管模型驱替实验,研究了改性微球在不同条件下的封堵能力、调剖能力。结果表明,改性微球的成球性好,平均粒径80 nm;50℃时,纯水中溶胀5~10 d后,微球颗粒的溶胀倍率可达2.9~3.9。同时,该微球具有较好的耐温、耐盐性能,在温度<90℃、矿化度<10000 mg/L时,能保持较好的溶胀性能。此外,用作调驱剂,微球的平均封堵率达85%以上;渗透率级差1∶5时,微球的剖面改善率为59.6%。

油田深度调剖化学剂驱油效率与机理

随着石油资源的日益紧张,提高油田开采效率成了石油行业面临的主要挑战。选用3种不同的化学剂(PAM、SDBS、PAA)并通过测定岩心渗透率和油水界面张力进行驱油效率实验。实验结果显示,PAA在提高岩石渗透率方面表现最为突出,从130.14 m D增加到212.43 m D,增幅为63.2%,而SDBS则在降低油水界面张力方面表现最佳,从38.92 m N·m^(-1)降至21.00 m N·m^(-1),降低了46.2%。此外,在中温(40℃)和中压(20 MPa)以及适中的注入流量(100 L·min^(-1))下,驱油效率达到最优。化学剂在改变岩石孔隙结构及降低油水界面张力方面的作用,共同促进了油水流动性的提升,从而显著增强了整体的驱油效果。研究结果对于指导实际油田作业中化学剂的选择和应用具有重要的参考价值,为油田开发提供了新的视角和方法。

温敏驱油剂的合成及性能评价

以丙烯酰胺、N,N-二甲基丙烯酰胺、十六烷基二甲基烯丙基氯化铵为合成单体,采用共聚后水解工艺,合成了温敏驱油剂。由红外光谱曲线可以看出,温敏驱油剂的聚合单体均接入纳米减阻剂的分子链。合成的聚合物具有优异的增黏、抗盐、抗剪切性能,且具有温度敏感特性,在一定范围内,随着温度的升高黏度不断增加。