A Study On Salt Deposition Mechanism And Development Technology In High Salinity Oilfield

Aimming at the question that salinity of formation water is saturated or oversaturated in some high salinity oilfields; salt is separated out in the formation,wellbore and oil pipeline, which results in production drawdown, high flow resistance or well shutdown, even leads to well being abondaned during developing. Author studied salt deposition mechanism and development technology in high salinity oilfield in this thesis, illustrated with 438B oilfield.This thesis studied the feature of geology & hydrocarbon accumulation,reservior, exploratory & development status with Dynamic of Hydrocarbon Aaccumulation.The salinity of T1 and SI formation water is up to 290～380 g/L.The possible causes that the salinity of SI formation water is higher than that of T1 formation water was analyzed.The salt deposition in oilfield is a serious problem that affects development in whole development phase.With electron microscope scanning, simulating pressure profile of near wellbore formation ,nature gas saturating, satured formation water displacing rock core water in formation ,reserch of formation salt deposition mechnism reveal: Salt particles was found in formation core, which can pass through the formation throat.When the formation pressure is higher than saturation pressure,there is no salt diposition in the formation,but the salt will deposit in bottom hole since fluid velocity slow down; When the formation pressure is lower than saturation pressure, lots of salt begins to deposite.When the formation pressure drops to 10MPa (abandonment pressure), the maxmun radius of salt deposition is up to 4.7m.Quantitative experiment of salt deposition mechanism in wellbore and oil pipeline found: Main factors affecting salt deposition are tempature, pressure, different ions content, gas fluid ratio, water cut and velocity, which affect salt solution and lead to salt separation in wellbore and oil pipeline.Based on Field Chemistry theory, AST-1 salt inhibitor fit for 438B block was optimized with synthesized appraisal method; the most suitable concentration is 10000-20000mg/L, inhabiting salt rate is up to 95%.The supersonic wave and chemistry combined removing formation damage technique was developed, which synthesizes supersonic removing damage, scrub function of active water and controlling salt deposition founction of salt inhabitor.Salt deposition from formation to wellbore is controlled or removed with this technology.Based on Analytical Chemistry and Electrochemistry, ion selective electrode monitoring method was reformed.Compared with Mohr Method, This new method has the features of simple, high accuracy and low pollution.Considering high salinity in 438B block and different development phase,the Combined salt Controlling & Production Technique, consisting of Hollow Screw Pomp & Replenishing Water Technique, Gas Lift & Replenishing Water with Capillary Tube Technique and Nature Flowing & Rreplenishing Water with Capillary Tube Technique ,has been studied successfully in this thesis.The different match surface facilities have been designed according to different lifting technique.These techniques ensure oil production of high salinity oilfield in desert short of water and power.