Study On Crystal Structure And Morphology Of Calcium Carbonate In O/W Emulsion

As an important tertiary oil recovery technology,ASP flooding technology can significantly increase oil recovery,also has brought serious fouling problems to the injection and production system.Fouling occurred in the injection and mining equipment,especially in the oil well,resulting in a significant decline in oil production efficiency,because blockage of the oil layer and pumping the pump.And the fouling phenomenon is accompanied by the whole process of crude oil production,which has severely limited the promotion of ASP flooding technology.In view of the actual situation of oil production in Daqing O ilfield,from emulsion environment and the perspective of crystallization,to understand the formation mec hanism of calcium carbonate in essence.Therefore,this paper simulates the O/W emulsion environment to study the effects of HABS and HPAM on crystal structure and morphology of calcium carbonate first time.In order to to determine the influencing factors of crystal form and morphology of calcium carbonate,Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and scanning electron microscope(SEM)were used to determine the polymorphy and morphplogy of Calcium Carbonate.The results of the study are as follows.1.Kerosene emulsion system:Fixed HABS concentration 600 mg/L and HPAM concentration 200 mg/L,in 0%,15%,25% and 50% of the kerosene emulsion,With the increase of reaction time(10min-2h),the content of vaterite decreased from 78.5% to 54.3%;the proportion of kerosene increased,and the content of vaterite increased from 78.5% to 93.7%.In the 25% kerosene O/W emulsion,the HABS concentration was 200 mg/L-1000 mg/L,and the content of vaterite increased from 23.3% to 76.3%.When the concentration of HPAM was 100 mg/L-500 mg/L,a mixed phase of calcite and vaterite was formed,and the content of vaterite was increased from 32.5% to 78.3%.Under the above conditions(with the exception of kerosene volume increase),the unit cell parameters a and Ca-O bond length of vaterite increase.Simulated formation temperature of 45 °C,reaction time increased from 10 min to 2 h,the aragonite content decreased from 85.6% to 0,and the reaction temperature increased from 35 °C to 85 °C.The aragonite content increased from 0 to 93.5%.The increase in temperature(35-85°C)is conducive to ion diffusion to generate a stable aragonite phase at high temperature,but it is delayed due to the steric hindrance of the hydrophobic group and oil phase of HABS and the electrostatic interaction between-SO3-and Ca2+ in HABS.The growth rate of the aragonite crystal nucleus changed the equilibrium lattice position of the original crystal lattice of calcium carbonate,resulting in distortion of the microscopic crystal structure of the aragonite,and the formation of aragonite calcium carbonate with a reduced surface roughness particle size.2.Crude oil emulsion system:Simulation of formation temperature of 45 °C,in 5%,15%,and 25% of the O/W emulsion,As the concentration of HABS increased from 200 mg/L to 800 mg/L,the content of vaterite increased,and the calcite content decreased.The 25% crude oil O/W emulsion system reacted with HABS concentration of 600 mg/L for 1 h,and the content of vaterite was 100%.The concentration of HABS was 600 mg/L and HPAM concentration was 200 mg/L.The reaction was conducted for 2 h,and the stable vaterite phase calcium carbonate was found.SO32-in HABS forms a complex with Ca2+ HABS(SO32-)Ca.HPAM contains several coordination bonds in which COO-forms a complex with Ca2+ HPAM(COO-)Ca,and the presence of crude oil and additives.Increased space steric hindrance,the joint action of the three delayed the transformation of ball crater,stabilized ball gangue.At the same t ime,the unit cell parameters a and Ca-O bond length of vaterite increase.The research results in this paper provide a scientific basis for the formation of calcium carbonate scale in the ASP flooding system,and find a method for preventing scale formation during the ASP flooding system from the root to provide a theoretical solution,the guidance provides technical support for improving oilfield production efficiency.