The extra-heavy oil in the Tahe Oilfield of China has extremely high viscosity, as it is rich in the heavy components asphaltene and resin, creating significant difficulties in its exploitation and transportation. Therefore, it is important to effectively reduce the viscosity and improve the fluidity of this extra-heavy oil. The traditional viscosity reduction method suffers from a high blending ratio and a shortage of light crude oil resources for extra-heavy oil blending. In this study, coal tar and washing oil—widely available low-cost by-products of the coal chemical industry—are used for extra-heavy oil blending and viscosity reduction. Washing oil—containing light components distilled from coal tar—was highly effective in reducing the viscosity of extra-heavy oil. When the dilution ratio of washing oil is 0.25, the viscosity of extra-heavy oil is reduced to 1214 mPa·s, and the viscosity reduction rate is 99.8%, indicating that washing oil is an efficient viscosity-reducing agent in extra-heavy oil blending. GC-MS showed that the washing oil contained abundant aromatic hydrocarbons and aromatic heterocyclic rings. A multi-component viscosity reduction system using washing oil coupled with toluene, xylene, and surfactant achieved an even better viscosity reduction effect. In conclusion, we designed a low-cost, high-efficiency, multi-component, and multi-functional synergistic system for extra-heavy oil viscosity reduction in the Tahe Oilfield. In the proposed working mechanism, aromatic hydrocarbons and aromatic heterocyclic rings in washing oil can intercalate into the layered structure of dense asphaltene aggregates, thereby dispersing and dissociating them.

In-situ combustion technology (ISC) was a potential technology for efficient development of medium-low maturity shale oil reservoirs. Clarifying the exothermic behavior of organic carbon oxidation will be beneficial for better control of ISC processes. In this work, the organic carbon composition, type II kerogen and residual oil, were separated and extracted from the shale samples of typical medium-low maturity shale oil reservoirs in the Ordos Basin, China. The synchronous thermal analyzer and mass spectrometry (STA-MS), Fourier transform infrared spectroscopy (FTIR), and ROCK-EVAL VI were used to study the products, heat release, and functional group changes of type II kerogen, residual oil, and shale during the oxidation process. The results indicated that the oxidation heat release of shale mainly came from the oxidation reaction between its residual oil and type II kerogen, but the oxidation heat release range of shale was relatively lagging compared to the single residual oil or type II kerogen affected by rock debris. Secondly, under atmospheric pressure, the type II kerogen experiences obviously higher heat release than residual oil and heavy oil, indicating its superior potential of in-situ heat release. In addition, the major productions that CO, H2O, 2 O, SO2, 2 , and CO2 2 were quantitatively characterized, with CO2 2 having the highest production of 882.25 mg/g. Furthermore, combined with the molecular weight, an oxidation reaction equation of type II kerogen was constructed. Finally, the oxidation kinetics parameters of type II kerogen, residual oil, and shale were determined using Friedman and Ozawa-Flynn-Wall (OFW) models. It was found that the activation energy of shale was higher than II kerogen and residual in low temperature oxidation (LTO) and fuel deposition (FD) stages. This may be due to the joint reaction between kerogen and residual oil, thus exacerbating the challenge of shale in-situ ignition. However, due to the catalytic effect of rock debris, the activation energy of shale was lower than LTO in high temperature oxidation (HTO) stage, indicating that once fuel deposition was completed, organic carbon will undergo stable combustion. This study has theoretical guidance for the numerical simulation research of ISC development technology of maturity-low shale oil reservoirs.

In recent years, low-salinity waterflooding and nanofluid flooding have been regarded as the new technologies for enhanced oil recovery and research (EOR). Research on the mechanisms behind the improvement in the recovery rate has garnered significant attention. However, little attention has been given to the mechanism of low-salinity water within the high-salinity range and the synergistic mechanism between low-salinity water and nanoparticles. In the salinity range of 0-22,0,000 mg/L, the interfacial properties of different concentrations of Na+, Mg2+, Ca2+, and SO42- were investigated. The following conclusions were drawn: interfacial tension (IFT) gradually decreased at elevated temperatures, reaching a minimum value of 14.9 mN/m for 2000 mg/L low-salinity water at 60 degrees C. The contact angle decreased significantly at increased temperatures, reaching a minimum value of 64.8 degrees for the contact angle of 2000 mg/L low-salinity water at 60 degrees C, indicating water-wet wettability. Electrostatic repulsion was the highest for 5000 mg/L low-salinity water, with a zeta potential value of -12.56 mV. Furthermore, Na+ significantly affected IFT and zeta potential values at low concentrations, while Ca2+ exhibited a more significant effect on wettability at low concentrations. Additionally, when utilizing 2000 mg/L low-salinity water as the dispersion medium for ZrO2 nanoparticles, increasing the particle concentration negatively impacted the stability of the nanofluid. As the temperature increased, IFT decreased, reaching a minimum value of 14.27 mN/m at a concentration of 0.01 wt % at 60 degrees C. Similarly, as the temperature increased, the contact angle decreased, with nanofluids at a concentration of 0.014 wt %, exhibiting the lowest contact angle of 51 degrees at 60 degrees C, indicating increased water-wet wettability of the rock surface. This study offered a fundamental understanding of interfacial phenomena involving low-salinity water and nanoparticles, indicating their potential for EOR technology.

Polymer gels are widely used in the oil and gas industry, and high-molecular-weight polymer gels have significant effects on reservoir water plugging operations. Based on nontoxic polyvinyl alcohol (PVA), its stability in solvents containing formation saltwater (Tahe oilfield, NW China) was studied, and the composite gel solution was prepared using saltwater. The polymerization mechanism of PVA with phenolic resin (PF) and polyacrylamide (PAM) was analyzed, using hexamethylenetetramine (HMTA) instead of formaldehyde for cross-linking, and the rheological properties of the prepared gel were tested; the results showed excellent elastic properties. The application value of the gel was evaluated by gelation performance, thermal stability, and indoor simulated core displacement. The gelation time of the PVA/PAM/PF gel at 130 ? was 4 h; after aging at 130 ? for 40 days, the gel strength of the polymer gel remained at the G level, and no dehydration occurred. The simulated core plugging results showed that the breakthrough pressure was 11.79 MPa and the plugging rate was 99.83%. Compared with the PAM/PF gel, the PVA/PAM/PF gel has a higher breakthrough pressure, which is beneficial to reduce the permeability of the porous medium.

It is often highly difficult to predict the main flow path of reactive fluids in porous media with complexly distributed fractures and/or caves. Based on Darcy's law, this research defines the control domain of fractures/caves that represents the interference range of fractures/caves. This control domain can be used to identify the connectivity possibility between fractures/caves and predict the flow paths of reactive fluids at the optimal flow rate. Furthermore, after simplifying the geometry of fractures/caves, a threshold geometric aspect ratio of 20 is set to distinguish fractures and caves, concerning the flow mechanisms, by clarifying the ranges of control domains. Moreover, the control domain theory is combined with the two-scale continuum model for acidizing carbonate rocks to estimate the flow paths of acid in fractured-vuggy carbonate rocks at an optimal flow rate, thereby validating the accuracy of the reactive fluid main flow path estimation based on the control domain theory. The primary criterion to determine the reactive transport in porous media with complex fracture/cave distribution is the overlap degrees of control domains of adjacent isobaric bodies along their width and length directions, while the directions of isobaric bodies offer supplementary material. If the control domains of two isobaric bodies overlap with each other perpendicular to the flow direction, these isobaric bodies have higher odds of connected fluid flow.

为拓宽生物质材料在油水分离领域中的应用,以新疆廉价的大宗废弃葵花杆为原料、壳聚糖为复合材料、硬脂酸为疏水改性剂,通过简单的冷冻干燥-常温浸渍法合成了一种具有超疏水性的杆茎纤维/壳聚糖复合气凝胶.采用傅里叶变换红外光谱仪(FT-IR),扫描电子显微镜(SEM),接触角测量仪对气凝胶进行表征,并评价了其吸油性能和循环使用性能.研究结果表明:当葵花杆纤维与壳聚糖质量比为6:1,硬脂酸加量为1.64％,浸渍时间为2.5 h时,复合气凝胶静态水接触角最大,为150.9°.对煤油等不同油品的吸附容量为12.34～21.85 g/g,并且经10次循环使用后仍保持稳定的吸油性能和疏水性能.研究成果不仅为油水分离材料的制备提供了一种新的方法,而且也为新疆丰富的秸秆高值化利用拓宽了途径.

Hydrogels have been widely adopted for in-depth water control in mature oilfields, however, the poor mechanical properties limit their application. Herein, a conjoined-network induced hydrogel was prepared through the in-situ free radical copolymerization of acrylamide (AM), Acrylic acid (AA) and N,N0methylenebis(acrylamide) (MBA) in the presence of nano-cellulose (CNF/ACNF), and the coordination effect between aluminium ion and carboxyl. The results showed that a small amount of nano-cellulose (0.2 %) increased the compressive strength of the hydrogel by 7 times. The presence of nano-cellulose endowed the hydrogel with excellent thermal stability and high shearing elasticity, at the same time, could effectively reduced the swelling rate that hindered its disintegration in practical application. The evaluation of sand-pack plugging suggested that the double cross-linked nano-cellulose hydrogel presented a significant capacity for efficient water plugging, where the breakthrough pressure gradient was as high as 23.73 MPa, the plugging rate reached 99.9%, and the maximum residual resistance factor was 3902.06. This work provided a novel design of hydrogel with high compressive strength and satisfactory stability for water shutoff and conformance control in heterogeneous oil reservoirs.(c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

分子沉积膜驱油剂(MD膜驱剂)作为一种新兴纳米材料驱油体系,可有效提高驱油效率.本文选用三羟甲基氨基甲烷、环氧氯丙烷和三乙胺为原料,合成出分子沉积膜驱油用的单分子双季铵盐体系,测定了MD膜驱剂的黏度、阳离子度、表面张力及其接触角等,并通过动态驱油试验对驱油效果进行了评价.结果表明,合成的MD膜驱剂性能稳定,体系黏度均在1.11 mPa·s左右;当浓度为800 mg/L时阳离子度达到71.73％,此时在砂岩表面的吸附性能最好;MD膜驱剂可使润湿性发生转变,将亲油表面载玻片(98.70°)转变为弱亲油(85.31°),使水湿表面载玻片(58.1°)亲水性增强(45.58°).MD膜驱剂能驱替出水驱未能采出的原油,水驱转为分子沉积膜驱后,驱油效率由42.55％上升到48.29％,而直接进行分子沉积膜驱后,驱油效率高达54.81％,相较于水驱后分子膜接替驱油,直接进行分子膜驱油能够获得更高的采收率.

以MCM-41作为载体,通过后嫁接法将硅烷偶联剂3-氯丙基三甲氧基硅烷接枝在MCM-41分子筛上,制备出功能化的含氯介孔材料MCM-41-Cl作为一种新型的超疏水材料。利用FT-IR、马尔文激光粒度仪、SEM来确定其结构,利用接触角测量仪等实验对材料进行性能评价。结果表明,3-氯丙基三甲氧基硅烷成功接枝在MCM-41上,功能化的MCM-41-Cl与水的接触角为157.9°,是一种分子筛基超疏水材料;并且考察MCM-41-Cl对不同油品及有机溶剂达到吸油饱和时的吸油率,发现MCM-41-Cl对甲苯的吸油率高达290.98%,呈现出良好的超疏水吸油性能。

The pre-crosslinked gel particles has been perceived as an important alternative to improve oil recovery from fractured-vuggy carbonate reservoirs. However, it remains a great challenge for the applications in high temperature and high salinity reservoirs. In this context, we firstly developed novel preformed gel particles with controllable density (PGPCD) which can be used at high temperature (140 degrees C) and high salinity (250 g/L) fractured-vuggy carbonate reservoirs for in-depth profile control and displacement. Then, the swelling property, toughness, injectivity, EOR potential and EOR mechanisms of PGPCD were investigated. Experimental results show that PGPCD has favorable swelling ability, toughness, and controllable density due to the introduction of sodium montmorillonite and modified foamed acrylate rubber (ACM) powders. Moreover, PGPCD has favorable injectivity, and can mitigate water channeling in the form of "filling accumulation", "bifurcation accumulation", and "necked accumulation". After the treatment, PGPCD achieves incremental oil recovery in a range of 16%-26% of original oil in place. Taken together, our findings suggest the role of PGPCD in promoting the incremental oil recovery at high temperature and high salinity reservoirs, especially in fractured-vuggy carbonate bottom water reservoirs.

为有效利用棉浆黑液、减少环境污染,以碱法棉浆黑液、苯酚、甲醛和聚丙烯酰胺为原料,通过水热法制备了黑液-酚醛复合凝胶,通过红外光谱、热重分析和扫描电镜对凝胶结构进行了表征,研究了苯酚加量对凝胶的影响,评价了凝胶的耐盐性、耐酸碱腐蚀性和封堵效果.结果表明,黑液-酚醛复合凝胶网络致密紧凑,热分解温度为200℃.苯酚加量为2％～4％的凝胶的成胶时间为24～14 h,含水率为72％～75％,吸水倍数为3.60％～3.92％.该凝胶具有黏度低、易泵入的优点,且具有良好的耐盐、耐酸碱性能.凝胶的封堵效果良好,对人工模拟岩心的封堵率大于99％.利用棉短绒黑液制备油田堵剂,不仅可以改善黑液污染,还可降低稠油开采成本.

Polymer solution has extremely extensive applications in many natural and industrial processes, especially in oilfield development field, such as polymer flooding, fracturing and water shut-off. Thus, the study of flow behaviors of polymer in formation pores is significantly important. In this paper, the flow behaviors of the polymer droplets in the 3-D pore throat structure were systematically studied. Additionally, the influencing factors (polymer concentration, molecular weight and pore throat ratio, for instance) were investigated. As the increasing of polymer concentration and molecular weight, the polymer droplets were more difficult to break, which means the critical flow rate decreased and the average sizes of the first daughter droplets (FDD) were longer synchronously. Moreover, with the increase in pore throat ratio, the critical flow rate increased and the length of the FDD decreased. In addition, the prediction models of the length of the FDD with polymer concentration and pore throat ratio were established, respectively. The prediction model revealed that the length of the FDD satisfied an exponential relationship with the polymer concentration and a linear relationship with the pore throat ratio. Finally, the average size of droplets after macroscopic core flooding experiment was 8 μm and 17 μm when the polymer concentration was 0.01% and 0.1%, respectively. The results were consistent with the breakup behaviors of polymer droplets in the microscopic pore throat structure.

Environmental boron removal and salt lake brine boron enrichment are important separation processes, which are of great significance to animal and plant health, environmental safety, and effective use of resources. Polymers are often used for boron separation due to their low cost and high performance. In this study, Tris(hydroxymethyl) methyl aminomethane (TRIS) and glucose functionalized polymer (P(GMA-co-TRIM)) were synthesized by hydrothermal method, and the polymer structure were characterized by FTIR, SEM, Mapping, XRD, XPS, PZC and TG-DSC-DTG. P(GMA-co-TRIM)-TRIS and P(GMA-co-TRIM)-Glu were used as boron adsorbents and the performance test were carried out. When the pH = 8 of boron solution, the two adsorbents have the best adsorption performance, with the adsorption capacity of 16.25 and 18.09 mg/g, respectively. The effects of initial concentration and contact time on boron adsorption were studied. Langmuir adsorption isothermal model and pseudosecond-order model were more consistent with the adsorption data, and the adsorption process was chemical adsorption. The two adsorbents have strong resistance to ion interference and cycle life, and have potential application value in environmental boron removal and boron extraction from salt lake.

Adsorption plays an important role in seawater desalination, wastewater treatment, and, especially, boron removal from natural aqueous systems. In this paper, two sponge-like multifunctional polymers based on a cyclodextrin backbone were synthesized and used as adsorbents for the removal of boron, methylene blue (MB), methyl orange (MO), and phenol. The syntheses were carried out by esterification, atom transfer polymerization, and nucleophilic addition reaction. The polymers were characterized by 1H NMR spectroscopy, IR spectroscopy, XRD, XPS, and SEM. The performance of the two different adsorbents was investigated considering the effect of pH, initial concentration, and the anions and cations in an aqueous solution of borates. The experimental data were fitted with an adsorption isothermal model, adsorption kinetic model and other models. Both adsorbents exhibited high adsorption capacities (B: 31.05 mg/g and 20.45 mg/g, MB: 29.43 mg/g and 32.29 mg/g, MO: 47.36 mg/g and 49.23 mg/g, phenol: 5.04 mg/g and 4.35 mg/g, respectively) and a fast adsorption rate. The boron adsorption was found to be an exothermic process. The adsorbents show promising potential for the removal of boron and benzene-containing organic pollutants from aqueous solution.

棉籽底油为棉籽榨油时的副产物,废弃的棉籽底油会造成严重的环境污染和资源浪费,首次提出使用乳化的棉籽底油作为一种选择性堵剂.选用合适的复配乳化剂配制出了高含水的棉籽底油W/O乳状液并进行了性能评价.使用流变仪对乳状液的增黏区间进行了研究,结果表明,最大增黏区间可以达到80％;使用分油率研究了乳状液的稳定性,乳状液的稳定性随着含水量的增加而增强;对棉籽底油乳化体系进行耐温抗盐能力评价,棉籽底油乳状液可以耐110℃高温,抗2×104 mg/L的钙离子;利用流性指数研究了不同含水量乳状液的流变性,含水量越高,假塑性越弱;填砂管驱替实验表明棉籽底油乳状液对水和油的封堵率分别为98％和15％,具有良好的封堵性和油水选择性.

In recent years, studies conducted on foam stabilization have focused on nanoparticles by generating strong adsorption at the interface to stabilize the foam under harsh reservoir conditions. Meanwhile, the selection of a gas source is also of great importance for foam performance. In this study, a mixed system of surfactants was selected, and the foamability and foam stability of nitrogen and methane were evaluated according to the improved jet method. After adding modified SiO2 nanoparticles, the foam-related parameters were analyzed. The plugging abilities of the different foams were compared through core-flooding experiments, and the oil displacement effects of the different foams were compared through microfluidic experiments. The results show that the amphoteric surfactant betaine has an excellent synergistic effect on the anionic surfactant SDS. The methane foam produced using the jet method has a larger initial volume than the nitrogen foam, but its stability is poor. The half-life of the nitrogen foam is about two times that of the methane foam. After adding 1.0 wt % SiO2 nanoparticles to the surfactant solution, the viscosity and stability of the formed foam improve. However, the maximum viscosity of the surfactant nanoparticle foam (surfactant-NP foam) is 53 mPa·s higher than that of the surfactant foam. In the core-flooding experiment, the plugging performance of the methane foam was worse than that of the nitrogen foam, and in the microfluidic experiment, the oil displacement abilities of the methane foam and the nitrogen foam were similar. The plugging performance and the oil displacement effect of the foam are greatly improved by adding nanoparticles. The surfactant-NP foam flooding has a better oil displacement effect and can enhance the recovery factor by more than 30%. Under actual high-pressure reservoir conditions, although the stability of the methane foam is weaker than that of the nitrogen foam, some methane may be dissolved in the crude oil to decrease the viscosity after the foam collapses, which leads to the methane foam being the preferred method in oilfields.

在油田开发过程中,由于修井、采油及地层结构的影响,油水井经常出现管外窜通和钻井液漏失等问题,严重影响采油速率和油水井的使用寿命.本文以环氧树脂作为封窜剂主剂,考察活性稀释剂缩水甘油丁醚加量、固化剂TEA加量、硅烷偶联剂KH-560加量对环氧树脂胶塞堵剂固化时间、固化强度、封窜等性能的影响,并根据简化的环氧树脂固化动力学模型,模拟得到树脂胶塞封窜剂凝胶时间和温度的关系曲线.研究结果表明,环氧树脂胶塞封窜剂中稀释剂缩水甘油丁醚的最佳加量为15％(占环氧树脂用量),固化剂TEA加量为10％～20％时,在130℃下环氧树脂胶塞封窜剂的固化时间可控制在2～5 h,固化后抗压强度可达到20 MPa以上,封窜强度5.57 MPa,当KH-560加量为3％～4％时,树脂胶塞的封窜性能提升2倍左右,具有很好的封窜性能,完全能够满足套管封窜要求.通过模型模拟得到稀释剂加量15％、固化剂TEA加量15％的环氧树脂胶塞浆液的凝胶时间tgel与温度T关系为:tgel=1.234exp(13208/T+273),对现场施工具有指导意义.图9表3参18

During the development of low or ultra-low permeability oil resources, the alternative energy supply becomes a prominent issue. In recent years, carbon dots (CDs) have drawn much attention owing to their application potential in oil fields for reducing injection pressure and augmenting oil recovery. However, carbon dots characterized of small size, high surface energy are faced with several challenges, such as self-aggregation and settling. The preparation of stably dispersed carbon dots nanofluids is the key factor to guarantee its application performance in formation. In this work, we investigated the stability of hydrophilic carbon dots (HICDs) and hydrophobic carbon dots–Tween 80 (HOCDs) nanofluids. The influences of carbon dots concentration, sorts and concentration of salt ions as well as temperature on the stability of CDs were studied. The results showed that HICDs are more sensitive to sort and concentration of salt ions, while HOCDs are more sensitive to temperature. In addition, the core flooding experiments demonstrated that the pressure reduction rate of HICDs and HOCDs nanofluids can be as high as 17.88% and 26.14%, respectively. Hence, the HICDs and HOCDs nanofluids show a good application potential in the reduction of injection pressure during the development of low and ultra-low permeability oil resources.

In this work, a novel water plugging agent, hydrophobic modified silica particle (HMSP)-surfactant-stabilized cottonseed oil emulsion, for oil recovery enhancement was developed. The stability and rheology experimental results displayed that the synergistic interaction between the HMSP and surfactant was formed, which could remarkably improve the stability and increase the viscosity of the emulsion system. The microscopic visualization tests suggested that there was a bicontinuous structure in the HMSP-surfactant-stabilized emulsion. Moreover, the sand pack flooding tests showed that the sweep and displacement efficiency could be significantly enhanced after HMSP-surfactant-stabilized emulsion injected. The blocking rates of HMSP-surfactant-stabilized emulsion and individual surfactant-stabilized emulsion are 98.7% and 52.9%, respectively. The above results can be considered as a guidance in the design and studies of HMSP-stabilized emulsion for a selective plugging.

To define the channel flow control (CFC) mechanism of the equidensity particle agent, the effect of CFC treatment in fractured-vuggy carbonate reservoirs was systematically analyzed by visual simulation experiments and field tests. The typical visual experimental model of the fractured-vuggy reservoir was designed based on the fractured-vuggy reservoir outcrop characteristics. It overcomes the shortcomings of the conventional model, whose experimental results are greatly affected by subjective factors. The water breakthrough in the dominant flow channel caused substantial shielded remaining oil to be left in the reservoir, resulting in violent flooding of the oil well. The shielded remaining oil accounted for approximately 43.8% of reserves, which is the potential point of the CFC treatment. The CFC treatment can effectively enhance the shielded remaining oil recovery by 22.2% in laboratory experiments. Based on its own efficient suspension and migration ability, the equidensity particle agent can be transferred to the whole dominant flow channel in the fractured-vuggy carbonate reservoirs. By using the multistage distributed shrinkage joint at the outlet of each vuggy and inside of each fracture to control the flow capacity, the equidensity particle agent can equably control the dominant flow channel along the path to realize a wide range of water flooding in the fractured-vuggy carbonate reservoirs.