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Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs:Effect of molecular weight of the cross-linking agent

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Petroleum Science 2022年第6期19卷 3182-3193页

作者： Hong-Jun Zhang Dao-Yi Zhu Yong-Long Gong Jun-Hui Qin Xiao-Ning Liu Yuan-Hang Pi Qi Zhao Run-Tian Luo Wan-Sheng Wang Ke-Ke Zhi Zong-Jie Mu China University of Petroleum-Beijing at Karamay KaramayXinjiang834000China

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of part

关键词： Temporary plugging agent Preformed particle gel Degradable cross-linking agent molecular weight Low-temperature reservoir

molecular weight and Aggregation of Erwinia Gum in Aqueous Solutions

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Chemical Research in Chinese Universities 2000年第2期16卷 156-162页

作者： ZHANG Lina XU Xiaojuan ZHU RongPing Iijima Hideki 武汉大学湖北武汉 430 0 72 国家标准物质研究中心国家标准物质研究中心北京 1 0 0 0 1 Asahi Chemical Industry Co. 日本 Miyazaki 882 -8847

Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weightaverage molecular weights M w, numberaverage molecular weights M n and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.

关键词： Erwinia gum Light scattering SEC Membrane osmometry Viscometry molecular weight Aggregation

Relating Cd2+binding by humic acids to molecular weight:A modeling and spectroscopic study

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Journal of Environmental Sciences 2018年第8期30卷 154-165页

作者： Hongcheng Bai Zhenmao Jiang Minjin He Biying Ye Shiqiang Wei College of Resources and Environment Department of Environment Science and EngineeringSouthwest UniversityChongqing 400715China Chongqing Key Laboratory of Agricultural Resources and Environment Chongqing 400715China China Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment Ministry of EducationChongqing 400715China

molecular weight（Mw） is a fundamental property of humic acids（HAs）, which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid（HA） extracted from Jinyun Mountain, Chongqing was ultra-filtered into four fractions according to the molecular weight, and their properties were characterized.Complexation of cadmium was investigated by titration experiments. For the first time,Langmuir and non-ideal competitive adsorption-Donna（NICA-Donnan） models combined with fluorescence excitation-emission matrix（EEM） quenching were employed to elucidate the binding characteristics of individual Mw fractions of HA. The results showed that the concentration of acidic functional groups decreased with increasing Mw, especially the phenolic groups. The humification degree and aliphaticity increased with increasing Mw as indicated by elemental composition analysis and FT-IR spectra. The binding capacity of Cd2＋ to Mw fractions of HA followed the order UF1（〈 5 kDa）〉 UF2（5–10 kDa）〉 UF4（〉 30 kDa）〉 UF3（10–30 kDa）. Moreover, the distribution of cadmium speciation indicated that the phenolic groups were responsible for the variations in binding of Cd2＋ among different Mw fractions. The results of fluorescence quenching illustrated that the binding capacity of Cd2＋ to Mw fractions was controlled by the content of functional groups, while the binding affinity was largely influenced by structural factors. The results provide a better understanding of the roles that different HA Mw fractions play in heavy metal binding,which has important implications in the control of heavy metal migration and bio-toxicity.

关键词： Humic acid molecular weight NICA-Donnan Fluorescence excitation-emission matrix quenching Cadmium

Characterization of dissolved organic matter as N-nitrosamine precursors based on hydrophobicity, molecular weight and fluorescence

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Journal of Environmental Sciences 2013年第1期25卷 85-95页

作者： Chengkun Wang Xiaojian Zhang Jun Wang Chao Chen School of Environment Tsinghua University

It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter （DOM） from two source waters was fractionated with XAD resins and ultra- filtration membranes. The N-nitrosamine formation potential （FP）（ng of N-nitrosamines formed per mg of dissolved organic carbon （DOC）） from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix （EEM）, molecular weight （MW） and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products （SMPs） and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA254 values.

关键词： N-nitrosamine hydrophobicity molecular weight fluorescence excitation-emission matrix soluble microbial products

EFFECT OF molecular weight OF PEO ON THE STRUCTURE AND PROPERTIES OF PDMAEMA/PEO HYDROGELS

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Chinese Journal of Polymer Science 2006年第1期24卷 35-40页

作者： Zhu-gen Liu Min Yi Mao-lin Zhai and Hong-fei Ha Department of Applied Chemistry and The Key Laboratory of Polymer Chemistry and Physics of Ministry of Education,College of Chemistry & molecular Engineering,Peking University,Beijing 100871,China Department of Applied Chemistry and The Key Laboratory of Polymer Chemistry and Physics of Ministry of Education College of Chemistry & Molecular Engineering Peking University Beijing 100871 China

A new kind of binary hydrogels composed of poly（dimethylaminoethylmethacrylate）（PDMAEMA） and poly（ethylene oxide）（PEO） with varying weight average molecular weights （M^-w = 5 × 10^4, 1 × 10^5 and 2.5 × 10^6） were prepared by У-irradiation technology. The properties of PDMAEMA/PEO hydrogels obtained were evaluated in terms of gel fraction, gel strength, thermal characterization and swelling behavior. The gel strength and swelling degree of the hydrogels could be improved obviously after adding PEO into the PDMAEMA system, while the degree of improvement decreased with increasing M^-w of PEO. The temperature sensitivity of PDMAEMA/PEO was retained only in the sample with PEO of M^-w = 5 × 10^4, and the pH sensitivity was retained in samples with PEO of M^-w = 5 × 10^4 and 1 × 10^5. When DMAEMA/PEO mixtures containing PEO of M^-w = 5 × 10^4 were irradiated, the main reaction could be the cross-linking of DMAEMA, and the linear PEO molecular chains could penetrate into the cross-linked network of PDMAEMA. With increasing M^-w of PEO, some side reactions were induced, such as grafting of DMAEMA onto PEO molecules, the scission or cross-linking of PEO.

关键词： Poly（dimethylaminoethylmethacrylate） Poly（ethylene oxide） molecular weight Binary hydrogels Irradiation.

The Effect of Trifluoroacetic Acid on molecular weight Determination of Polyesters:An in Situ NMR Investigation

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Chinese Journal of Polymer Science 2021年第12期39卷 1590-1596页

作者： Yan-Yan Tu Xue-Ting Wan Jie Huan Xiang Zhu Xiao-Hong Li Ying-Feng Tu State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials College of ChemistryChemical Engineering and Materials ScienceSoochow UniversitySuzhou 215123China

Due to the poor solubility of aromatic polyesters in comm on orga nic solve nts,trifluoroacetic acid is usually used as a co-solve nt to increase their solubility for characterizations.However,only few studies have reported the side reactions induced by it.We present here the application of in situ 1H-NMR techniques to explore its effect on the hydroxyl end-groups,which are usually used for the molecular weight determination of polyesters by end-group estimation method.Using bis(2-hydroxyethyl)terephthalate(BHET)as model compound,quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent(1:10,V:V).This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid,revealed by the H-^(13)C gradient-enhanced heteronuclear multiple bond correlation(gHMBC)spectrum.The mixtures of dimethyl terephthalate and BHET with different molar ratios were used to represent poly(ethylene terephthalate)(PET)with different degrees of polymerization,and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied.Our results show that if a relative error of 5%is allowed,the NMR measurements must be finished within 1.3 h of solution preparation at 25℃ in the mixture solve nt.The results were confirmed in PET sample,while in poly(ethyle ne adipate),the obtained esterifaction con stant is faster that those in aromatic system.The results can be applied to other polymer systems with alcohol functionalized groups,and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

关键词： Polyesters NMR spectroscopy Trifluoroacetic acid molecular weight

SYNTHESIS OF HIGH molecular weight POLYISOBUTYLENE VIA CATIONIC POLYMERIZATION AT ELEVATED TEMPERATURES

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Chinese Journal of Polymer Science 2013年第8期31卷 1139-1147页

作者： Qiang Huang Ping He Jue Wang 吴一弦 State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology

A novel simple but effective initiating system of H2O/AlCl3/veratrole （VE） has been developed to synthesize high molecular weight polyisobutylene （PIB） at elevated temperatures via cationic polymerization of isobutylene （IB） in solvent mixture of hexane/methylene dichloride （n-Hex/CH2Cl2 = 2/1, V/V）. VE played very important roles in decreasing cationicity of the growing chain ends, suppressing side reactions of chain transfer and termination during polymerization, leading to production of high molecular weight PIBs. PIBs with high yields, having very high weight-average molecular weight （Mw） of 1117000 and 370000 g/tool could be synthesized with H2O/AICl3/VE initiating system at VE concentration of 5.4 mmol/L at -80 and -60 ℃ respectively. molecular weight of PIB increased remarkably with increasing VE concentration. The reaction order with respect to VE concentration was determined to be -3.52 via FTIR spectroscopy in combination with a diamond tipped attenuated total reflectance （ATR） immersion probe. The negative reaction order of VE was consistent with its retarding effect on IB polymerization by interacting with the propagating species. molecular weight of PIB decreased with increasing polymerization temperature. The activation energy for polymerization degree （Eop） could be determined to be around -23 kJ/mol when VE concentration was 5.4 mmol/L or 6.4 mmol/L.

关键词： Isobutylene molecular weight Cationic polymerization Polyisobutylene Kinetics.

A NEW TYPE LOW SHEAR RATE VISCOMETER FOR HIGH molecular weight POLYMER

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Chinese Journal of Polymer Science 1996年第4期14卷 311-317页

作者：叶美玲韩冬施良和 Polymer Physics Laboratory Institute of Chemistry Academia Sinica Beijing 100080

In this paper, the effects of shear rate on the intrinsic viscosity measurement of partially Hydrolysed Polyacrylamide (HPAM) in salt solution were studied with homemade multibulb viscometer and low shear rate rheometer. The critical shear rate of HPAM in salt solution for high molecular weight HPAM was determined. A low shear rate capillary viscometer was designed in which the [eta] approached to value at zero shear rate can be obtained for HPAM -salt system. The effect of molecular weight on shear rate dependence of viscosity was also studied.

关键词： viscometer intrinsic viscosity molecular weight polyelectrolyte polyacrylamide capillary viscometer

LOW molecular weight O-CARBOXYMETHYLATED CHITOSANS DERIVED FROM IRRADIATED CHITOSAN AND THEIR ANTIBACTERIAL ACTIVITY

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Chinese Journal of Polymer Science 2004年第6期22卷 521-527页

作者：管云林 School of Materials Science and Engineering Tianjin University Tianjin 300072 China

Original chitosan with M-v of 2.7 x 10(5) was degraded by irradiation with gamma-rays and a series of low molecular weight O-carboxymethylated chitosans (O-CMCh) were prepared based on the irradiated chitosan. A kinetic model of the irradiation of chitosan was put forward. Results show that the irradiation degradation of chitosan obeys the rule of random degradation and the degree of deacetylation of irradiated chitosan is slightly raised. The antibacterial activity of O-CMCh is significantly influenced by its MW, and a suppositional antibacterial peak appears when M-v is equal to 2 x 10(5).

关键词： chitosan O-carboxymethylated chitosan irradiation degradation antibacterial activity molecular weight