Fouling Mechanism And Experimental Research Of Glass Steel Pipe

Currently,most oilfields use water injection technology as the main approach to increase oil recovery ratio in China.With the continuous increase of water content and the degree of salinity of the formation water,the scale formation of ground gathering pipelines has become increasingly serious.In order to solve the scale formation,GFRP with excellent performance are widely used at home and abroad to replace traditional steel pipes.However,under the influence of complex environmental factors in the oilfield,GFRP still have the scale formation.At present,there is a lack of research and mechanism on the scale formation of GFRP at domestic and foreign.Therefore,this paper first investigated the literature and works related to research on the pipeline fouling formation at home and abroad,mastering the research methods for the pipeline fouling formation and clarifying the current deficiencies in their studies.Moreover,on this basis,a dynamic circulating fouling device was innovatively self-developed which can simulate a real flow environment.According to the actual working conditions of an oilfield in Xinjiang,the mechanism of fouling of GFRP pipeline was studied.The main research contents include:（1）The paper analyzed the quality of formation water and the composition of scale formation phases in this oilfield,obtaining preparation method of the simulation mineralization water.Based on the actual working conditions of GFRP pipeline,the cause of scaling in GFRP pipeline of the oilfield was analyzed through the existing domestic and foreign mechanisms of scale formation.The composition characteristics of GFRP were analyzed,laying the theoretical foundation for the further study.（2）A static experimental was conducted on scale formation of GFRP.The water erosion experiment of GFRP was firstly carried out which concluded that the effect of glass fiber hydrolysis and epoxy resin swelling have minimal impact on scale formation.Then the static method was used to simulate the scale formation of GFRP.It obtained influence rules of temperature,time,material roughness and surface free energy on scale formation of GFRP by comprehensively analyzing the macro and micro test results,explaining the reason for the prone to scaling in the first half of GFRP pipeline in the oilfield.Meanwhile,the amount of fouling between GFRP and 13Cr in the same working conditions was compared to analyze the effect of surface properties on it,which provided the scientific basis for the selection of gathering pipelines in the oilfield.（3）A dynamic circulating fouling simulation device was developed.Due to the operation parameters of the oilfield,a dynamic circulation fouling device was self-developed which have capable of simulating realistic tube flow environment.The device designed by similar principles,namely to ensure the similarity of geometry,movement and power between the model and the prototype.The core of the device consists of two test pipe sections and control-monitoring system.Through the control of fluid temperature and pressure,flow velocity,pipe material,and wall temperature difference,the oil-water pipe flow environment can be truly simulated.The experimental data can accurately and valuably describe the fouling phenomenon of the corresponding prototype.（4）A dynamic experimental was conducted on scale formation of GFRP.The second test pipe section of device was used to conduct the dynamic circulation experiment of GFRP pipe scale formation,obtaining the influence rules of temperature,time and actual circulation rate on scale formation.Furthermore,the gray correlation theory was adopted to analyze the relevance of the temperature and circulation rate on scale formation of GFRP.Finally,control measures were proposed to suppress scale formation on the spot.In addition,the effect of ion concentration of Fe²⁺ and Mg²⁺ on fouling formation was qualitative clarified.（5）This paper quantitatively analyzed the influence mechanism of Fe²⁺ and Mg²⁺concentration on scale formation.According to the results of dynamic experiment,CASTEP module of Materials Studio（MS）was utilized to establish the structure model of Ca_6-xMg_x（CO₃）₆ and Ca_6-xFe_x（CO₃）₆ based on the calcite crystal structure,calculating the elastic property parameters and obtain the influence degree of Fe²⁺ and Mg²⁺ ion concentration between the aragonite promotion and calcite intensification.On this regard,the selection method of scale inhibitors on the spot was proposed,thus achieving the effect of inhibiting scale formation by controlling the metal ion concentration.According to the above researches,this paper achieved the influence rules of factors such as temperature,circulation rate and metal ion concentration on scale formation of GFRP pipeline,determining the mechanism of scale formation of GFRP pipes and putting forward the measures for inhibiting scale formation in the oilfield,which provided help for strengthening the safety and stability in the operation of GFRP gathering pipelines and the production efficiency of the oilfield.