Accelerated oxidation during air flooding in a low temperature reservoir

To ensure the safety of application of air flooding in a low temperature reservoir, the accelerated oxidization of oxygen and the crude oil is studied at low temperature. The stabilized chlorine dioxide solution can be used as a type of catalyst, which can accelerate the reaction rate of oxygen and the crude oil to decrease the concentration of remaining oxygen when the gas reaches the production well. The experimental results of oxidization show that O₂ concentration is greatly reduced and CO₂ concentration is greatly increased on condition with catalyst. In addition, the amount of heavy components can be further reduced and the amount of light components can be further increased. These can ensure the safety of application of air flooding in low temperature reservoir. The experimental results of adaptability of the accelerated oxidation under different water saturation show air flooding can be better used in the low-temperature reservoir with low water saturation on condition with catalyst but cannot be used in the low-temperature reservoir with high water saturation. The experimental results can provide theoretical basis for the application of air flooding in a low-temperature reservoir.     

The effect of low-temperature oxidation in air-assisted steam flooding process for enhancing oil recovery

Air-assisted steam flooding is a new promoting technique for enhanced oil recovery compared to the other traditional thermal recovery methods. In this study, five experiments, including one steam flooding experiment, three combined steam–air flooding experiments, and one combined steam–N₂ flooding experiment were studied, under the conditions of 180 °C and back-pressure valve of 8 MPa, with sand-packed model. The volume fraction of mixed gas in these four combined steam–air (or N₂) flooding experiments were 80% steam+20% air, 60% steam+40% air, 40% steam+60% air, and 60% steam+40% N₂, respectively. The experimental results showed that air-assisted steam flooding could enhance the oil displacement efficiency when the volume fraction of air and steam was in a certain number, and the optimal condition is 60% steam+40% air. Furthermore, water cut curves and saturate, aromatic, resin, and asphaltene (SARA) analysis results also demonstrate that the low-temperature oxidation reaction in air-assisted steam flooding process advantageous to profile control of generating high viscosity “PLUG” to seal high-permeability channel in reservoir.     

轻质原油低温氧化催化技术

注空气采油技术由于气源和成本优势,具有广阔的发展潜力,但是安全问题一直是限制其应用的重要因素。为加快氧气消耗速率,降低生成烟道气中氧气的含量,提高注空气的安全性,进行了原油低温氧化催化技术研究。通过评价过渡金属元素对低温氧化反应的催化效果,筛选了催化剂及其用量;研究了温度、压力、含水率和岩石矿物等对催化性能的影响,并采用多管平行实验研究了不同反应阶段低温氧化反应的特征;在动力学参数计算和红外谱图分析的基础上研究了原油低温氧化催化反应的催化机理。实验结果表明:过渡金属元素Cu对原油低温氧化反应有很好的催化效果,优选的催化剂为CuCl₂,最佳用量为原油质量的0.88%,在油藏条件下可提高反应速率近2倍;温度和压力升高对低温氧化反应有促进作用,在所研究的温度、压力和反应阶段内,催化剂的低温氧化催化效果显著;催化剂对原油低温氧化反应的催化机理为配位催化,可显著降低反应的活化能,加快低温氧化反应速率,提高原油的耗氧能力。     

SZ36-1油田注聚井和聚驱受益油井堵塞物的组成及成因对比分析

随着注聚开发的进行,SZ36-1油田的部分受益油井中出现了含聚堵塞物,导致了产能下降。采用多种表征手段对比分析了注聚井和受益油井堵塞物的组成,发现在所采集到的样品中,受益油井堵塞物以无机垢为主,无机垢/有机垢质量比为4.0～5.5,远大于注聚井的0.25～0.75,受益油井和注聚井中无机垢分别主要为Fe_2O_3和CaCO_3,有机垢则均为部分水解聚丙烯酰胺。对比分析了注聚井和受益井中无机垢和有机垢的成因,重点分析了受益油井堵塞物的成因:在受益油井的近井地带,酸化作业后的残酸含有大量Fe~(3+),与聚合物驱替液相遇后,液体pH值上升,形成Fe(OH)_3沉淀,氧化后即形成Fe_2O_3无机垢;驱替液中降解后的聚合物在酸性条件下会选择性地与Fe~(3+)通过配位作用,形成水不溶的聚合物交联物,即形成有机垢。分析结果可为注聚井和注聚受益油井的针对性解堵以及预防注聚受益油井堵塞提供依据。     

低渗透油藏空气驱原油氧化机理实验

为深入探究低渗透油藏空气驱开发过程中原油的氧化特征及其影响因素,评价其驱油效果,以新疆油田低渗透油藏为研究对象,开展原油组分分析、原油氧化特征、空气驱及空气泡沫驱等实验,系统研究了不同条件下原油氧化特征及规律。实验结果表明:相同条件下,油砂比纯油样静态氧化反应速率大,反应充分,且反应速率与反应压力、温度、作用时间呈正相关;油藏温度下,原油经历氧化反应后轻重比减小,主峰碳增加;反应温度对空气驱原油动态氧化特征有较大影响,温度越高耗氧量越大,反应越充分;空气驱具有较好驱油效果,但易发生气窜;泡沫驱可有效封堵气窜通道,扩大空气波及体积,改善空气驱效果。研究成果对空气驱理论研究及应用具有借鉴意义。     

Effect of low-temperature oxidation of light oil on oil recovery during high pressure air injection

In this research, the low-temperature oxidation (LTO) behavior of light oil was evaluated via isothermal oxidation tube experiments. Also, the core model together with nuclear magnetic resonance (NMR) analyzer was implemented to explore the effect of LTO of light oil on oil recovery during high pressure air injection (HPAI). The results indicated that the polycondensation reaction of light components (C₅-C₆) and intermediate ones (C₇-C₁₇) for light oil was the preferred reaction path during LTO process. The oxygen addition was the primary oxidation reaction in LTO, but the LTO reaction presented a more favorable trend for the bond scission with the oxidation degree. Because of the gas flow steering resulting from property variation of light oil and heat release determined by LTO, the total oil recovery yielded by air flooding was 8.82% higher than nitrogen flooding.     

稠油油田空气辅助蒸汽驱现场试验

为考察稠油油田空气辅助蒸汽驱的开采效果,开展了稠油油田空气辅助蒸汽驱现场试验研究工作。在齐40块蒸汽驱试验区选择原油濒临枯竭的、油藏已经发生严重蒸汽窜流和超覆的、亟待改变开发方式的5个井组进行现场试验,结果表明:5个试验井组平均单井组日产油由14.8 t/d升至16.1 t/d,油汽比由0.14升至0.17;油层纵向动用程度明显提高,分析认为是注入的空气在纵向和平面上首先向蒸汽驱优势方向波及,与残余原油发生低温氧化反应使孔隙中沥青质沉积增加,降低油层渗透率,迫使蒸汽转向,扩大蒸汽波及范围。研究认为:空气辅助蒸汽驱宜采用连续式空气/蒸汽注入方式;汽气比接近1: 40可取得较高采收率;70 m井距注入的空气与地下原油发生低温氧化反应,油藏温度有所提高,产出氧气含量可降到安全范围内。现场试验取得成功,利用空气辅助蒸汽驱改善稠油油田蒸汽驱开发效果具有可行性。所选试验井组存在的问题在普通稠油蒸汽驱井组生产后期具有普遍性,因此本文试验方法和相关技术参数可为类似井组开展空气辅助蒸汽驱试验提供参考。     

The wettability with Ca2+ brine in a tight oil reservoir with zeta potential

Abstract

Based on Zetasizer Nano ZS instrumentation, the zeta potential with Ca²⁺ and tight oil reservoir were analyzed to study the abilities and microscopic mechanisms on reservoir characteristics of wettability. The results show that in the CaCl₂ solution, Ca²⁺ can reduce the surface hydrophilicity of tight sandstone, thus change the reservoir wetting characteristics. While increasing pH can improve reservoir wettability and facilitate tight oil development. Ca²⁺ can change the structural characteristics of tight reservoirs and crude oil. This provides a theoretical basis for our study of low salinity water flooding and recovery ratio.     

Changes in the properties of conventional crude oil before and after CO2 flooding

Abstract

In order to enhance oil recovery of a conventional oil reservoir by CO₂ flooding, the changes in the properties of the crude oil before and after CO₂ flooding are systematically investigated by on-site sampling and experimental testing. The results show that, after CO₂ flooding, the light hydrocarbons of the produced crude oil is increased and the heavy hydrocarbons of the produced crude oil is decreased due to the deposition of resins and asphaltenes in the pores of the formation. In addition, the produced fluid (a mixture of oil and water) has a high water separation rate, the oil- water interface has a high tension value, and the crude oil has a high acid value and a low viscosity. The conclusions can provide a certain guidance for high-efficiency development of a conventional oil reservoir by CO₂ flooding.     

Flow Properties of CO2/Crude Oil in Miscible Phase Flooding

Abstract

The high-temperature and high-pressure three-dimensional (3D) device is used to study miscible flooding of CO₂ and crude oil. The experiment model is a real sand plate. In oil reservoir condition, there is a large difference between production and injection volume. The complex flowing characteristics of CO₂ flooding in pore media are observed in recovery, water cut, and gas–oil ratio curves. By analyzing the water saturation contour plot measured by a saturation probe, CO₂ and oil can be miscible. The viscosity of miscible liquid and flowing pressure decreases. This is the important mechanism of enhanced oil recovery. When the viscosity of miscible liquid and flowing pressure decreases, miscible CO₂ and oil contacted with water can make a similar three phase. This is the important mechanism of enhanced oil recovery. Based on the conclusion, the main reason for the production and injection difference is that high-density CO₂ would flow into pore media in which water and oil cannot flow.     

Evaluation of Interfacial Tension Between Zahra Oil and ASP Solution

Alkaline-surfactant-polymer (ASP) flooding has been proved to be an effective enhanced oil recovery (EOR) method. Reduction of interfacial tension (IFT) between crude oil and ASP solution is the main mechanism in ASP flooding. Evaluating IFT between crude oil and ASP solution is a key parameter for ASP flooding in laboratory experiments or field projects. In order to obtain good result of ASP flooding in the reservoir in Zahra field, the influence of the concentration of Na₂CO₃ on IFT between Zahra crude oil and ASP solution with three different surfactants, BHJC, SS-231, and SS-233, was researched. IFT was measured with surface tension meter SVT20N, Dataphysics Co. Germany, at 72°C. For the view of IFT result anionic surfactant BHJC is more suitable for the Zahra oil field. This research is helpful for practical application of ASP flooding in Zahra oil field.     

Low-temperature isothermal oxidation of crude oil

In this work, the low-temperature oxidation (LTO) characteristics of different API gravity crude oils, involving one light, one medium, and one heavy, are studied comprehensively from the aspects of effluent gas, oxidized oil, and pressure drop. The results reveal that heavy oil exhibits faster LTO reaction rate and stronger O₂ consumption capability compared with lighter ones. There are a certain amount of carbonaceous deposits in oxidized oils and the carbonation progress of heavy oil is brought to a deeper degree. The pressure drop rule of oil samples is speculated to be the consequence of “skin effect” and crude oil with more heavy species shows higher oxidation activity, which contributes to an improved understanding about the LTO mechanism from the molecular perspective and needs further research.     

Calorimetric study approach for crude oil combustion in the presence of clay as catalyst

In this research, the effect of heating rate and different clay concentrations on light and heavy crude oils in limestone matrix was investigated by differential scanning calorimeter (DSC). In DSC experiments, two main distinct reaction regions were identified in all of the crude oil + limestone matrix + catalyst, known as low- and high-temperature oxidation respectively. It was observed that addition of clay to porous matrix significantly affected the thermal characteristics and kinetics of different origin crude oils. The Borchardt and Daniels and ASTM kinetic methods were used to determine the kinetic parameters of the samples. It was observed that activation energies generated for the high-temperature oxidation region for crude oil and crude oil + clay mixtures were in the range of 148–370 kJmol^?1 for the Borchardt and Daniels method and 51–253 kJmol^?1 for ASTM methods.     

CO2 miscible flooding in low permeability sandstone reservoirs and its influence on crude oil properties

Miscible CO₂ injection process has become widely used technique for the enhanced oil recovery in low permeability reservoirs. Core flooding experiments and field test of CO₂ miscible flooding in low permeability sandstone reservoirs and its influence on crude oil properties was studied. The results showed that CO₂ miscible flooding in low permeability sandstone reservoirs can enhance oil recovery both in laboratory study and field test. The permeability of sandstone reservoirs decreased during CO₂ miscible flooding due to the precipitation of asphaltene of crude oil. The precipitation of asphaltene lead to a reduction of asphaltene content and the apparent viscosity of crude oil. A further study on inhibitors and removers for asphaltene deposits from crude oil should be investigated to prevent and remove asphaltene deposits in low permeability sandstone reservoirs.     

Fe0/Graphene Nanocomposite as a Catalyst for the Viscosity Reduction of Heavy Crude Oil

Fe⁰/graphene nanocomposites were prepared via a thermal polymerization method and used as a catalyst to reduce the viscosity of heavy crude oil. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption-desorption isotherms and thermal analysis. Their performance on the aquathermolysis of heavy crude oil was assessed in an autoclave. Under the reaction conditions of 200°C and 24 h, the viscosity of the oil was remarkably reduced when the catalysts were added.     

THE STUDY OF PRODUCING HEAVY TRAFFIC ASPHALT BY USING THE HIGH VISCOUS CRUDE FROM NO.l SHUGUANG ZONE OF LIAOHE OIL FIELD

ABSTRACT

The characteristics of the high viscous crude from No. 1 Shuguang Zone of Liaohe Oil Field are similar to those of residue distillates of general crude such as high density(ρ ₂₀=0·9977 g.cm^-3),high viscidity υ ₁₀₀= 1223·9 mm².s-¹) and high carbon/hydrogen ratio. This oil contains less wax, but rich in resin and asphalt, which belongs to low sulfur naphthene-base crude oil and can be used as feedstock to produce high paving asphalt. But now it is used as fuel after emulsificating. In order to make full use of this oil and resolve the problem of paving asphalt demand-supply, various paving asphalts conforming to GB50092-96 standard were produced by blending vacuum residue of the high viscous crude from No.l Shuguang Zone of Liaohe Oil Field and waste oil which is rich in aromatics and poor in wax. The laboratory test results show that modified paving asphalts have good low-temperature properties and antiaging feature.     

火驱油藏岩矿与原油演化特征

温度是影响火驱储集层岩矿和流体性质变化的主要因素。为细分火驱各阶段变化特征,采用热重-差示扫描量热法,刻画了原油氧化过程,同时运用X射线衍射、背散射电子成像等技术,研究不同温度区间岩矿演化过程及其对储集层物性的影响。研究结果表明,火驱过程中存在原油氧化启动、高温燃烧门槛、岩矿热活化、岩矿深度变质等4个温度关键节点,将油岩演化过程分为地层预热、原油低温氧化、原油中温氧化和黏土分解、原油高温氧化和黏土烧结、非黏土矿物深度变质5个阶段。其中原油高温氧化和黏土烧结阶段为整个过程的激烈期,原油燃烧释放热量占总放热量的60%左右,黏土矿物发生烧结作用,使储集层孔隙结构和物性发生明显变化。     

降低启动压力的表面活性剂体系在朝阳沟油田的应用

针对朝阳沟低渗透油田注水过程中注水压力上升较快、欠注严重的问题,进行了朝阳沟油田降压增注表面活性剂体系的筛选工作,最终确定表面活性剂体系的配方为0.2%石油磺酸盐类表面活性剂T702-40^#+0.5%Na₂CO₃。实验结果表明,该表面活性剂体系与原油间平衡界面张力能够达到2×10^-2mN/m,耐温、抗盐性好,与朝阳沟油田注入水和地层水配伍性好,能够使岩石的润湿性发生反转,比水驱提高采收率5%左右。该表面活性剂体系驱替计算得出的可流动渗透率值约比水驱可流动渗透率值大15%,具有明显的降低启动压力的作用,并进行了表面活性剂体系降低启动压力的机理分析。朝阳沟油田朝82-152井区矿场试验结果表明,该表面活性剂体系能够降低启动压力,使油层吸水能力提高,使低渗透储层动用比例提高,7口油井累积增油1768t。     

The extraction effect of CO2 injection on the flow properties of crude oil

During CO₂ flooding, extraction of lighter hydrocarbons from crude oil makes the remaining oil hard to be recovered. In this work, we design a new experimental method to characterize the effect of CO₂ extraction on crude oil. The experimental results show that, the volume of extracted hydrocarbons increases as system pressure increases. The hydrocarbons with wider carbon number can be extracted from crude oil at high pressures. Moreover, the wax precipitation and viscosity of the remaining oil increase with increasing pressure. This study is expected to provide the basic understanding of the mechanisms of CO₂ flooding for enhanced oil recovery.     

Catalytic effect of in-situ preparation of copper oxide nanoparticles on the heavy oil low-temperature oxidation process in air injection recovery

In situ prepared hydrophobic CuO nanoparticles, about 84.3 nm in mean diameter, was synthesized and used to catalyze heavy oil low-temperature oxidation (LTO) reaction. Experimental results showed the average oxygen consumption rate with CuO nanoparticles addition increased by 1.4 times, and the residue oxygen content in tail gas in autoclave was decreased from 8.76% to 3.9% compared to the blank experiment (without CuO nanoparticles). In addition, the CuO nanoparticles could facilitate the cleavage reaction during LTO. This study can provide guidelines to improve effectively the safety of air flooding technology in the heavy oil.