Theoretical Study On Prevention And Control Of Barium Sulfate Scaling In Jiyuan Oilfield

The main way of oilfield development and production is water injection development.Water injection to the formation can supplement energy and is also an important means to improve oil recovery.It is the most common way of secondary oil recovery and development.Scaling problem?especially barium sulfate scaling?is one of the difficult problems in water injection development.During water injection,due to the change of formation temperature,pressure and other conditions or the incompatibility of SO₄^2-injected into the water and Ba²⁺in the formation water,barium sulfate scale will be generated,which will block the pores and throat,cause serious damage to the reservoir and affect the overall development benefit of the block.Water absorption index and oil recovery index are two important parameters in the process of oil field water drive development,which directly affect the change of oil recovery.Therefore,it is very important to establish a reasonable scale prediction model to simulate the changes of barium sulfate scale amount,water absorption index and oil production index in different water injection stages for the development of waterflood oilfield.Taking Jiyuan oilfield as an example,this paper analyzes the micro scaling mechanism of barium sulfate scale,the main factors affecting the scaling and the scaling position of barium sulfate scale in the formation.The scaling prediction model of barium sulfate in core and the scaling model of chemical reaction kinetics of barium sulfate in formation are studied.The influence of scaling of barium sulfate on water injection index and oil production index of oil production well is predicted.The specific results are as follows:?1?Through the study of the prediction model of barium sulfate scaling in core,the dimensionless diffusion coefficient and dimensionless reaction rate constant are obtained,the formation damage coefficient is solved,the influence of barium sulfate scaling on the core permeability damage rate and the influence of different scale inhibitors on the core permeability are explored.?2?The prediction model of barium sulfate scaling in core is extended to the formation,and the mass conservation equation of micro element in near well zone is studied.Based on the one-dimensional barium sulfate scaling prediction model in the near well zone of water injection well,the variation of scaling ion concentration,the amount of barium sulfate scaling and the amount of barium sulfate scaling in the near well zone of water injection well with different scale inhibitors are simulated.Based on the one-dimensional barium sulfate scaling prediction model,the Ba²⁺concentration change and the barium sulfate scaling amount change in the near well zone of the production well after a period of water injection are simulated.?3?Based on the one-dimensional barium sulfate scaling prediction model in the near well zone of water injection well,the water absorption index is introduced to predict the change of water injection well when injecting water with different pore volume multiples,the influencing factors of water absorption index under scaling conditions are analyzed,and the change of water absorption index of water injection well when adding scale inhibitors with different scale inhibition effects is simulated.?4?Based on the prediction model of barium sulfate scaling in the near well zone of oil production well,the production index is introduced,and the change of production index when injecting water with different pore volume multiple is predicted.The influencing factors of production index under the condition of scaling are analyzed,and the change of production index when adding scale inhibitor with different scale inhibition effect in the injected water is simulated.