The effects of temperature and acid number of crude oil on the wettability of acid volcanic reservoir rock from the Hailar Oilfield

Wettability of acid volcanic reservoir rock from the Hailar Oilfi eld,China,was studied with crude oils of different acid numbers generated from an original crude oil with an acid number of 3.05 mg KOH/g. The modif ied oils and their resultant acid numbers were:A(2.09 mg KOH/g) ,B(0.75 mg KOH/g) ,C(0.47 mg KOH/g) ,D(0.30 mg KOH/g) ,and E(0.18 mg KOH/g) . Contact angles and improved Amott water indexes were measured to study the effects of temperature and acid number on the wettability of the acid volcanic r...     

Emulsifying action of Pseudomonas aeruginosa L6-1 and its metabolite with crude oil for oil recovery enhancement

Pseudomonas aeruginosa L6-1 was isolated from formation brine of Xinjiang Oilfield, China. Strain L6-1 showed perfect emulsification activity to crude oil and transformed mixture of crude oil and water into emulsion when crude oil was used as sole carbon source; thus, this method is a promising approach for emulsification and mobilization of residual oil in oil reservoirs and enhancement of its recovery. Average diameters of emulsified crude oil were between 1 and 8 µm. Interfacial tension of crude oil and water was reduced to 0.8 mN m^?1. Strain L6-1 produced 2.2 g L^?1 of rhamnolipid biosurfactant. Core flooding tests were carried out to investigate application potential of strain L6-1 for microbial enhanced oil recovery (MEOR). Enhanced oil recovery efficiencies ranged from 9.23% to 12.58% in both core models, with and without oxygen injection. These results revealed that strain L6-1 is a candidate functional microorganism for MEOR application.     

Experimental investigation of oil recovery during water imbibition

Capillary imbibition and gravity are the main forces acting in fractured reservoirs. The cores used in the laboratory are usually short while experimental investigation of the gravity forces requires long samples. Therefore an experimental study has been carried out on a long core with the length of 116 cm surrounded with a simulated fracture. Kerosene and a synthetic oil with a density very close to brine have been chosen in order to distinguish the capillary and gravity effects during the water oil displacement. After doing many carefully conducted tests at different rates, it is clear that the process is significantly influenced by gravity. The second part of the study involved experiments on the long core surrounded with a simulated fracture where the flow processes are dominated by either co-current or counter-current imbibition. We changed the recovery mechanism from co-current to counter-current by changing the boundary conditions from an advancing fracture water level to an immersion-type mechanism. Our co-current and counter-current experiments on a tall block showed that counter-current imbibition has lower recovery than co-current imbibition. A wettability study was done after cutting the core into many pieces and aging the pieces in crude oil. Different wettability states were obtained by applying different aging times. The cores with different wettability index were subjected to immersion-type experiment. The results showed that more water wet conditions gave higher oil recovery.     

考虑渗吸和驱替的致密油藏体积改造实验及多尺度模拟

矿场试验表明,压裂后不立即放喷,依靠焖井过程的驱替和渗吸可置换小孔隙内的原油,提高原油采出程度。为探索该过程机理,进行了实验和模拟研究。首先,带压渗吸实验,模拟裂缝壁面在驱替压差和毛管力共同作用下的渗吸行为,无因次时间中加入驱替项（Δp）,对实验结果进行归一化处理;其次,建立基于CT 扫描的孔隙尺度模型,通过致密岩心采收率拟合, 获得驱替、渗吸的相渗和毛管压力;最后,在油藏尺度,分别赋予基质和裂缝不同的相渗和毛管压力,模拟矿场实际油水流动。结果表明:带压渗吸采收率明显高于自发渗吸采收率,提高幅度10%~15%;无因次时间中加入驱替项,可对实验结果进行较好的归一化;调整微观孔隙结构如孔道/ 喉道半径、孔喉比、配位数等参数可以实现渗吸采收率的拟合;油藏尺度对基质/ 裂缝以及渗吸/ 驱替的划分,可准确反映开采初期含水率变化。     

Using biosurfactant producing bacteria isolated from an Iranian oil field for application in microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is a useful technique to improve oil recovery from depleted oil reservoirs beyond primary and secondary recovery operations using bacteria and their metabolites. In the present study, the biosurfactant production potential of Bacillus licheniformis microorganisms that were isolated from oil samples of Zilaei reservoir in the southwest of Iran was explored under extreme conditions. Growth media with different temperatures of 40, 50, 60, and 70°C; salinities of 1, 3, 5, and 7 wt%; and yeast extract concentrations of 0.5, 1, 1.5, and 2 g/L were used to find the optimum growth conditions. The results demonstrated that bacteria grown in a mineral salt solution with temperature of 50°C, salinity of 1 wt% and yeast extract concentration of 1 g/L has the highest growth rate and therefore, these conditions are the optimum conditions for growing the introduced bacterium. This isolate was selected as the higher biosurfactant producer. The obtained biosurfactants by bacteria isolated in a medium with these conditions could reduce the interfacial tension of crude oil/water system from 36.8 to 0.93 mN/m and surface tension of water from 72 to 23.8 mN/m. The results of the core flooding tests showed that the tertiary oil recovery efficiency due to the injection of microorganisms was 13.7% of original oil in place and bacteria could reduce the oil viscosity by 41.242% at optimum conditions. Based on these results, the isolated microorganism is a promising candidate for the development of microbial oil recovery processes.     

The Removal of Naphthenic Acids from Beijiang Crude Oil With a Sodium Hydroxide Solution of Ethanol

Abstract

A new method is introduced in this article to separate naphthenic acids from Beijiang highly acidic crude oil with a sodium hydroxide solution of ethanol. The sodium hydroxide solution of ethanol was used as the acid removal reagent by mixing with the crude oil and then allowing the two phases to separate, with the naphthenic acids being extracted from the crude oil. Data indicated that the optimal content of sodium hydroxide in crude oil was 3,000 μg/g and the optimal extraction time was 5 min with the reagent/oil ratio being 0.4:1 (wt/wt). The suitable reaction temperature could be room temperature. The total acid number of the crude oil was lowered from 3.92 to 0.31 mg KOH/g and the acid removal could reach up to 92.1%.     

A thermotolerant surfactant-producing strain XT-1 applied for exogenous microbial enhanced oil recovery

A surfactant-producing strain XT-1 was isolated, identified and evaluated for exogenous microbial enhanced oil recovery (e-MEOR) in this study. The strain XT-1 was identified as bacillus subtilis through 16S-rDNA phylogenetic analysis, could grow and produce bio-surfactant at a wide temperature range from 20°C to 57°C with the highest surfactant yields of 830 mg/L. The bio-surfactant produced by the strain showed high degree of temperature-stability. Microbial core flooding experiment using three different types of crude oil at 35°C– 55°C indicated XT-1 can increase oil recovery of 6.88%?13.38%. These results demonstrate XT-1 have great potential for e-MEOR.     

Solutions of Lube Base Oil Not Meeting Acid Value Requirement

Two solutions of producing HVI400SN lube base oil meeting acid number requirement were determined. One solution was that optimum operation conditions were found by optimization solution of single-stage extraction experiment data (i.e., the solvent/oil ratio was 5, the top and bottom temperatures of extractor were 120°C and 80°C, respectively). Another solution was that at least four theoretical plates were required after transformation of the existing furfural extractor, and verification results of pilot test showed viscosity index of refined oil was 106 and acid number was 0.0174 mg (KOH)/g under current operation conditions of industrial extractor.     

超高酸原油中环烷酸类型及分布规律研究

通过对国内某原油进行实沸点切割和环烷酸分离,采用电位滴定仪、红外光谱仪及质谱仪等研究原油、馏分油中环烷酸分布及类型.研究结果表明:原油酸值为13.18 mg(KOH)/g,属于超高酸原油,其环烷酸主要集中为400～425℃,425～450℃和>450℃馏分,分别占原油总酸质量的4.68％,5.34％和54.44％;超高...     

Wild melon: a novel non-edible feedstock for bioenergy

In the present research work, a non-edible oil source Cucumis melo var. agrestis(wild melon) was systematically identified and studied for biodiesel production and its characterization. The extracted oil was 29.1% of total dry seed weight. The free fatty acid value of the oil was found to be 0.64%, and the single-step alkaline transesterification method was used for conversion of fatty acids into their respective methyl esters. The maximum conversion efficiency of fatty acids was obtained at 0.4 wt% Na OH(used as catalyst), 30%(methanol to oil, v/v) methanol amount, 60 ℃ reaction temperature,600-rpm agitation rate and 60-min reaction time. Under these optimal conditions, the conversion efficiency of fatty acid was 92%. However, in the case of KOH as catalyst, the highest conversion(85%) of fatty acids was obtained at 40%methanol to oil ratio, 1.28 wt% KOH, 60 ℃ reaction temperature, 600-rpm agitation rate and 45 min of reaction time.Qualitatively, biodiesel was characterized through Fourier transform infrared spectroscopy(FTIR) and gas chromatography and mass spectroscopy(GC–MS). FTIR results demonstrated a strong peak at 1742 cm~(-1), showing carbonyl groups(C=O)of methyl esters. However, GC–MS results showed the presence of twelve methyl esters comprised of lauric acid, myristic acid, palmitic acid, non-decanoic acid, hexadecanoic acid, octadecadienoic acid and octadecynoic acid. The fuel properties were found to fall within the range recommended by the international biodiesel standard, i.e., American Society of Testing Materials(ASTM): flash point of 91 ℃, density of 0.873 kg/L, viscosity of 5.35 c St, pour point of-13 ℃, cloud point of-10 ℃, total acid number of 0.242 mg KOH/g and sulfur content of 0.0043 wt%. The present work concluded the potential of wild melon seed oil as excellent non-edible source of bioenergy.     

Evaluation of interfacial tension between ASP solution and crude oil from B oil field

The interfacial tension (IFT) between alkali-surfactant-polymer (ASP) solution and crude oil is an important parameter for evaluating the feasibility of the ASP flooding for an oil field. The IFT between six series of ASP solution and crude oil from B oil field were measured at 65°C. Each series of ASP solution was composed of NaOH or Na₂CO₃, one of the three kinds of surfactants (S1, S2, and S3), and polymer FT60. The concentration of FT60 and surfactant were 1500 and 2000 mg/L, respectively. The research results show that the IFT between ASP solution and crude oil is ultra-low in the NaOH-FT60-S2 series and NaOH-FT60-S3 series and the best concentration of NaOH is 4000 mg/L and 8000 mg/L, respectively. NaOH-FT60-S2 series is more suitable for B oil field. The IFT between ASP solution and crude oil is ultra-low in the Na₂CO₃-FT60-S2 series and the best concentration of Na₂CO₃ is 4000 mg/L.     

渗吸置换提高原油采收率研究进展

渗吸置换作用已逐渐成为非常规油藏和低渗、特低渗裂缝性油藏提高原油采收率的一种重要方式,大量裂缝的存在及细小孔隙发育为渗吸作用的发生创造了有利条件。首先,基于毛细管压力与重力对渗吸的贡献程度,对渗吸模式进行分类;而后,主要聚焦于影响渗吸的各类因素,详细阐述如储层类型、孔渗物性、边界条件、流体(包括原油与渗吸液体)性质等因素对渗吸的影响规律及作用机制,总结了目前使用的研究渗吸的各种实验手段;最后,根据渗吸作用的研究进展,探讨在实验条件确定、黏土水化影响、界面张力优化和渗吸模式选择等方面所面临的问题,并对这些问题的研究前景进行展望。      

Studying Bacillus cereus's ability to biodegrade crude oil in hot areas

In this study, the biodegrading ability of three spices of Bacillus isolated from a soil, which was contaminated by crude oil, was studied. Isolated species are able to biodegrade crude oil carbohydrates by producing biosurfactants and lowering the rate of surface tension at different temperatures and pHs. The decrease of surface tension from 57 mN/m to 31 mN/m at 37°C and to 32.5 mN/m at 20°C by Bacillus cereus B1 in samples with 1% crude oil can be referred to as the results of this research.     

Wettability alteration and oil recovery by water imbibition at elevated temperatures

This investigation adopts a new perspective on wettability alteration as a function of temperature. Colloidal (i.e., DLVO) theory and calculations are used to interpret results from laboratory-scale displacements. Water imbibition tests were conducted with 9 reservoir cores from a diatomaceous reservoir. Permeability and porosity of cores varied from 0.2 to 0.7 md and 46% to 65%, respectively. The experiments included spontaneous counter-current water imbibition followed by forced co-current water imbibition to residual oil saturation. The fluids were 34° API crude oil and synthetic formation brine. All tests were isothermal and temperatures ranged from 45 to 230 °C at pressures sufficient to maintain liquid water. The experimental results show that an increase in temperature results in: (1) a substantial increase in imbibition rate and extent of oil recovery, (2) a slight reduction in residual oil saturation, and (3) a significant shift in the Amott wettability index from intermediate and weakly water wet to strongly water wet. DLVO calculations illustrate detachment of fines from pore surfaces at high temperature. Fines detachment is a mechanism for altering wettability. Release of fines coated with oil exposes clean water-wet pore surfaces. Further calculations indicate the water–oil contact angle decreases as temperature increases indicating a systematic increase in water wettability consistent with experimental measurements of the Amott index.     

Study of resin fraction of Nigerian crude oil using spectroscopic/spectrometric analytical techniques

Organics and trace metals of the resin fraction of Nigerian crude oil were analysed in order to characterise the fossil fuel. The crude oil samples were deasphaltened by n-pentane, while maltene fraction was fractionated into its components (saturates, aromatics and resin) using column chromatography. The organic compounds and elemental concentrations of the resin fraction were investigated using Fourier Transform Infrared Spectroscopy and Inductively Coupled Plasma Optical Emission Spectrometry respectively. The infrared spectra showed characteristic bands containing polar functional groups expected confirming that the resin was purely eluted. The elemental concentrations were found to be high compared to other fractions and was confirmed by their T-test values. Zinc had the highest mean concentration of 32.13 ± 35.66 mg/kg, while Mn had the least (1.14 ± 0.17 mg/kg). Results indicated that processing of the crude oil resin may cause catalyst poisoning/fouling, corrosion of equipment/pipelines. Therefore, adequate consideration of these trace metals must be taken before processing.     

致密岩心带压渗吸规律实验研究

致密油藏体积改造压后闷井过程中发生的渗吸置换,通常在压差(基质外部流体压力与孔隙压力之差)作用下进行,但渗吸置换物理模拟却通常在常压下进行(即自发渗吸),带压条件下的渗吸置换特征尚未提及.为研究压差作用下的渗吸置换(即带压渗吸)规律,首先,建立基于低场核磁共振测试技术的带压渗吸实验方法;其次,分析自发/带压渗吸的异同;...     

减二线馏分油微波辐射脱酸新方法的研究

以NaOH与去离子水为复合溶剂用微波辐射法对江苏减二线馏分油进行了脱酸精制研究。得到的最佳精制条件为 :V(复合溶剂 )∶V(油 ) =0 .2 2∶1、压力 0 .0 9MPa、恒压辐射时间 4min、微波功率 375W、静置时间 2 5min。馏分油的酸值 (KOH)由 0 .5 7mg/ g降至 0 .0 4 81mg/ g ,馏分油回收率为 99.3%。     

低渗透砂岩油藏渗吸采油影响因素研究

通过对低渗透砂岩应用静态渗吸实验方法,研究界面张力、渗透率、原油黏度、渗吸液矿化度对渗吸过程的影响规律,认识不同因素对渗吸采油效率的影响.结合渗吸机理,通过渗吸速度、渗吸采收率的比较,发现一定范围内,界面张力为10-1mN/m数量级、较高渗透率、较低原油黏度、较高渗吸液矿化度条件下,表现出较好的渗吸效果.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.