| In the process of production and transportation of crude oil,the problem of wax formation in reservoir,wellbore and oil pipeline has been puzzling the oil industry,especially the problem of wellbore wax formation,which has a serious impact on the normal production of oil fields.Longdong area is the oil enrichment area of Ordos basin,the crude oil in this area belongs to the paraffin-based crude oil,the oil well generally has the more serious waxing phenomenon,while the LN block waxing situation is the most special,the waxing phenomenon appears in the deep part of the wellbore,and the waxing of the tail pipe and pump mouth is especially serious,which affects the normal production of the oil well.The commonly used oil-soluble wax remover usually has low density and cannot stay deep in the wellbore for a long time.Therefore,this paper aims at the problem of waxing deep in the wellbore of the LN block of Longdong Oilfield,comprehensively analyzes the cause of waxing,and carries out the study of wax cleaning and control system.Based on the LN block in Longdong area,the present situation of paraffin precipitation was analyzed.According to the actual operation data in the field,the paraffin precipitation prediction model is established by BP neural network,and the model is optimized by genetic algorithm to improve the accuracy of paraffin precipitation prediction under the interaction of different influencing factors,so as to provide reliable basis for the daily operation of oil wells.In this paper,the wax sample and crude oil in the LN block are taken as the research object,and analyze the causes of serious wax deposit in this block through the determination of component,structure,carbon number distribution,dissolved wax point of the wax sample,viscosity-temperature curve and carbon number distribution of crude oil,etc.The results show that there are three main reasons for the serious wax formation in wellbore in the research block:first,the high carbon fraction in crude oil is large,more than half,so it is easy to appear the phenomenon of wax formation;second,the molecular structure of wax sample is mainly straight chain alkane,and the carbon chain is longer,which leads to the phenomenon of wax formation in the high temperature of downhole;third,the high mechanical impurity content in wax sample,which provides the attachment point for the precipitation of wax molecule,and exacerbates the phenomenon of wax formation.Based on the analysis of the causes of paraffin precipitation in the depth of wellbore,the research on paraffin remover and inhibitor was carried out.Firstly,the paraffin removal components with high speed of paraffin dissolution and high density were obtained by agentia screening and formula optimization.On this basis,the mutual solvent and anti wax components were added.Finally,paraffin remover and inhibitor HX-3 was obtained.Its speed of paraffin dissolution was 0.049 g·min-1 and anti-wax rate was 45.3%.Through the indoor dynamic simulation experiment,the application effect of paraffin remover and inhibitor is verified,and the result shows that that its performance is good.At the same time,combined with the actual characteristics of oil well production,the field test was carried out to develop a reasonable dosing system to form a long-term paraffin control technology,and two wells were tested in the oil production field.The experimental results show that the effect of paraffin removal and control is stable,which provides necessary guidance for solving the production dilemma of serious paraffin deposition in the wellbore of oil wells in the block. |
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