Study On The Synthesis,Performance And Mechanism Of Heavy Oil Viscosity Reduction And Seepage Flow Improver

The key problem in heavy oil recovery is high viscosity and difficult seepage caused by the macromolecular in asphaltene and resins.In this thesis,viscosity mechanism and improved method in reservoir seepage are discussed based on the composition and structure information of resins and asphaltene in heavy oil.Seepage flow improver based on main monomer of oleic acid ester is synthesized and characterized.The efficiency of pour point depression,viscosity reduction,interfacial activity,catalytic aquathermolysis property are evaluated.Preliminary field test in Jianghan oil field and laboratory core displacement experiment of Liaohe heavy oil are conducted to investigate the enhanced efficiency and mechanism in seepage improvement.The specific research content and achievements are as follows:Based on modern analysis methods,the composition,structural information and viscosity cause on super heavy oil in the Xin5 well of Liaohe and extra heavy oil of Tahe are understood.The analysis of UV,IR,¹H NMR,GC-MS and XRD show the typical structure of resins and asphaltene in the two typical heavy oils,which contain polar hydrogen bonding groups such as carbonyl,hydroxyl,amino,sulfydryl,ester,ether etc and long chain alkyl,aromatic,super molecular aggregates.The main reason for the high viscosity of heavy oil is the entanglement and interpenetration of long-chain alkyl,?bond interaction between aromatic lamellae,strong intermolecular force,hydrogen bonding effect and difficult thermal motion of macromolecular associations.Taking oleic acid octadecanol ester and styrene as main monomerds,allyl sulfonic acid,2-acrylamid-2-methylpropanesulfonic acid with excellent metal ion chelation,strong hydrogen bonding and interfacial activity as comonomer,seepage flow improver oleic acid octadecanol ester-styrene-maleic anhydride-allyl sulfonic acid?MOSS?and oleic acid octadecanol ester-styrene-maleic anhydride-2-acrylamide-2-methyl propane sulfonic acid?MOSA?were prepared by orthogonal experiment.Based on which,MOSSNa,MOSANa with the function of improving the interface activity are prepared,furthermore,aquathermolysis catalysts MOSSCu?MOSACu are synthetized by chelating a small amount of Cu²⁺.Systematic characterizations are taken for the above prepared compounds.The content of C,H,O,N,S elements is consistent with the composition of monomers,and the content of Cu in MOSSCu and MOSACu is 19.51mg/g and 19.08 mg/g respectively.FT-IR and ¹H NMR results confirm the existence of phenyl,long chain alkyl,ester,carboxyl,sulfonic acid,amino in the polymer,which is in accordance with the design of the polymer.The XRD spectra shows that the characteristic peaks of the two synthesized polymers are similar to that of asphaltenes in heavy oil,which provided a structural basis for the eutectic with heavy oil.The pour point depression and viscosity reduction effect of the synthesized oil-soluble seepage flow improver?MOSS,MOSA,MOSSCu,MOSACu?were investigated by National Standard.With addition of 1.0 mg/g,the wax prevention of 65^#high melting point wax is 27.4%,32.3%,26.4%,31.5%.MOSS and MOSA can make the condensation point of heavy oil in Xin 5 well of Liaohe decrease by 10.5 and 12.4 respectively,which of Tahe heavy oil are 21.4 and 23.6.The effect of MOSSCu and MOSACu is slightly lower compare with the above ones.In the viscosity reduction test,the viscosity reduction is 91.6%,91.9%and 90.5%,91.1%for the heavy oil in Xin 5 well of Liaohe,respectively for MOSS,MOSA,MOSSCu and MOSACu with addition of 1500 mg/L at30°C.Under the same conditions,upon ultrasonic intensification for 45 minutes,1000mg/L of the MOSS,MOSA,MOSSCu and MOSACu can achieve the comparable effect in condensation point decline and viscosity reduction of 2000 mg/L without ultrasound,which suggests the synergistic effect of ultrasonic wave is obvious.The synthesized polymer with the abundant long-chain alkyl and aryl have good oil solubility,which can promote seeping into the resin and asphaltene.The ester,carboxyl,sulfonic acid,amino groups could result in the structural lattice distortion of wax crystal and aromatic lamella in the asphaltene aggregation,leading to decline of condensation and wax crystallization.Simultaneously,the plentiful ester anhydride groups can serve as hydrogen bond receptors and collapse the hydrogen bonds in the asphaltene aggregates,cause the disintegration of the asphaltene,lower viscosity and enhance the flowability of heavy oil.The catalytic aquathermolysis performance of MOSSCu and MOSACu is investigated.Orthogonal experiment to Tahe heavy oil shows that at the optimized condition?563.15K,0.15%catalyst addition,100:10 of oil to water ratio,toluene as hydrogen donor?,the viscosity reduction of MOSSCu and MOSACu is 90.8%,92.3%respectively.Analysis of the composition and structure of aquathermolysis products showed that resin,asphaltene and refractory wax content were decreased by 1.4%and1.84%in MOSSCu and MOSACu.The asphaltene was decreased from 30.28%to 19.26%under the existence of MOSSCu and from 30.28%to 19.04%for MOSACu,which suggested that the asphaltene which effect the heavy oil viscosity seriously was transformed into resins and refractory wax.Meanwhile,the content of O,N,S heteroatoms in resins and asphaltene was decreased to a certain extent after aquathermolysis,which indicated that part of O,N and S containing molecules have been broken down to small molecules flowing into the light components.GC-MS information of refractory wax shows that bond cracking and conversion have taken place,and the signal of C₂₃-C₂₉ species is descended after reaction and many isomer peaks disappeared,which is consistent with the obvious decline of long-chain alkyl and ester peak of resin and asphaltene in the infrared analysis.The signal at?=2.35 in ¹H NMR spectrum of resins was intensified,which was weakened for asphaltene,implying the cracking of ester groups.Based on Brown-Ladner analysis of fused aromatic rings,aromaticity of resins and asphaltene was increased and the fused aromaticity was decreased,while aromaticity and viscous aromas of the asphaltene have always been higher than that of the resin.It can be concluded that broken of long-chain alkyl and ester bring small fragments of asphaltene and macromolecule resin into light components such as refractory wax and resins,which confirmed the fact that asphaltene is converted into resin and refractory wax.This result is closely related to the inductomeric effect and electrostatic effect of Cu²⁺to the resins and asphaltene,as well as acceptance and attraction to electrons in O,N,S heteroatoms of the empty orbital in Cu²⁺,which can weaken C-S,C-N bonds,promoting the dissociation under high temperature and pressure provided by vapor.Seepage flow improver can improve the break resins and asphaltene macromolecules into smaller ones under high temperature with steam flooding or steam huff and puff,which can achieve a reliable viscosity reduction and seepage features improvement.The improvement of interfacial activity on MOSSNa and MOSANa was investigated.The surface tension of heavy oil was reduced with increasing addition of MOSSNa and MOSANa,while the oil-water interfacial tension was increased slightly.For the heavy oil-SAS active water system,the interfacial tension reduced obviously with addition of MOSSNa and MOSANa.In preliminary field test,the MOSANa/SAS was applied to the heavy oil well in the intermittent mining Jianghan Xikou heavy oil well to detect the flow and permeability characteristics,viscosity of the wellbore or nearby the well as well as its adaptability.The optimized mass ratio of MOSANa to SAS is 0.508:0.492,which could achieve a viscosity reduction of 92.0%and dehydration rate of 31.6%in 30 min with moderate stability,0.5 m³ oil can be increased in each round.The seepage flow improver was amphiphilic,which could enhance the dispersion and emulsification of resins,asphaltene,wax crystal and reduce the oil-water interfacial tension.Finally,the heavy oil in Xin 5 well of Liaohe was selected as research object to detect the displacement efficiency of MOSS,MOSA under hot water flooding by unconsolidated sand model test,furthermore,the percolation law and mechanism of seepage improvement were discussed under simulated reservoir condition.The experimental results show that premixed seepage flow improver has better displacement effect than slug injection with lower displacement starting pressure,displacement pressure and seepage resistance.Premixing 1000mg/L of MOSS,MOSA at 60 could increase recovery by 19.70%and 20.59%,which was slightly inferior than that of 500mg/g MOSS,MOSA at 70 or slug injection condition.In displacement experiments,because of the high viscosity,much refractory wax,choking action of aggregated asphaltene particles,clogging block effect of adsorption layer on the surface of the rock,the starting pressure and seepage resistance are rather obvious.The appearance of MOSS/MOSA could break the hydrogen bonds,weaken the intermolecular Van der Waals force and the adsorption reaction between heavy oil and rock mineral.During the displacement process,heavy crude components are separated by different degrees of chromatographic separation,the reason of which is the weakened adsorption between heavy oil molecules and rock mineral,partial asphaltene and resins molecular adsorbed solidly were detached by hot water,leading to a enhanced heavy oil recovery.Upon a deep and systematic study,the series of MOSS,MOSA polymer have the ability of wax resistance,condensation point decline,viscosity reduction,catalytic aquathermolysis activity and improving the interfacial activity,which can enhance oil recovery by improving the fluidity and seepage characteristics of heavy oil,furthermore,the preliminary efficiency of practical application in oil field is good.The concept of seepage flow improver is put forward in this study.The seepage flow improver was prepared considering the composition and structure of heavy oil,aiming at developing a multi-effect,efficient and adaptable seepage flow improver.In addition,the selection of oleic acid as monomer,the optimization of hydrogen bond acceptor,the separation of refractory wax,the analysis of condensation point and viscosity reduction mutation as well as appearance of starting pressure are innovative.