Study On Treatment Method For Acidizing Returning Liquid Of Offshore Oilfield

Acidizing technology has become one of the commonly used measures to increase production in offshore oilfields because of its good yield-increasing effect and low construction cost.The acid injected into the near-well zone can effectively dissolve the holes,seams and holes that are in contact with it,and the pollution in the near-well zone can be relieved and the permeability can be improved.After acidizing of the oil well,it takes a period of returning to be put into normal production.However,due to the low pH value,high shale content and complex composition,the acid reflux liquid is often caused by the“electric field” of the electric dehydrator when entering the electric dehydrator,that is,the internal liquid conductivity of the electric dehydrator The large internal short circuit caused the electric water heater to trip and could not work normally.The common treatment method for onshore oil fields is to use a large settling tank to settle the return liquid and settle the oil,so that the impurities and water in the oil are naturally separated.However,because of the small space and short operating cycle of offshore oil fields,such treatment methods are difficult to achieve.The use of buffer tanks to transport the return liquid back to the land for processing will consume a lot of manpower and material resources,and the treatment cost is too high.Therefore,it is urgent to design an economical and practical acidizing return liquid treatment method for the characteristics of the offshore oil field.This paper takes the oil from the three oil wells of S oilfield as an example to study the return and discharge.The oil phase and the water phase were separately treated by using a hydrocyclone for preliminary separation.The basic parameters of the water phase and the oil phase were analyzed,and the reasons for the oil phase overcurrent were initially determined based on these parameters.Through indoor experiments,the effects of temperature,pH value,oil,water type and water content,emulsification and shale content on the electric dehydration effect of oil phase were analyzed.The experimental results show that temperature,pH value,oil,water type and water content are not the main reasons for the difficulty in electrical discharge of the return liquid.The main reason is the oil phase and water under the action of mud,iron hydroxide precipitation and other substances.Phase emulsification forms an extremely stable emulsion which is difficult to handle by conventional methods.For the reasons,the effective treatment methods designed in this paper are as follows:(1)Adding viscosity reducer to assist centrifugal separation,and screening two kinds of agents,the optimal concentration is200mg/L and 250mg/L respectively;(2)Adding mud removal The agent assisted the centrifugal separation,and the two agents were screened out.The optimal concentration was200mg/L and 300mg/L respectively.The upper layer of the oil phase after treatment was easy to separate,and it could be normally discharged after entering the electric dehydrator.A set of aqueous treatment schemes was designed: screen filtration-oil absorbing felt cloth-strong oxidizer iron removal-flocculation sedimentation.The oil phase,oil content,suspended matter content and other indicators of the water phase treated by this process can reach the re-injection standard of the oil field.