Study On Scaling Technology Of Heater Used On Offshore Oilfield

In one FPSO, oil Tubing of steam heaters are suffering scale blocking problemsfrom the beginning of the production. For the past few years, steam heater scaling ismore and more serious; it brings tremendous potential risks for oil production.Pointing at this problem, this paper analyzed scales from heater, researched watercomponents at different points of production process, and studied the scaling tendencyof oilfield water. The article indicated that main types of scaling are CaSO4, SrSO4,Mg(OH)2and KCl.Through the steam heater water quality scale of theory and experiment research,the main impacting factors are, interface temperature, pressure, the velocity of thefluid, standing time. Interface temperature of heater is the most influencing factor onscaling speed and volume of scale. Calcium sulfate scaling in water is enhancingwhen the temperature of interface is increasing, pressure is reducing, flow velocity isdecreasing, retention time is lengthening. Small range of fluctuation of water-cut ofoil and concentration of scale ion has less impact on scaling of heater.According to the characters of heater scaling on this oil field, one chemicalinhibitor HTSI has be developed, it has better compatibility with oilfield producedwater, has little impact on water corrosion and good depressiveness in oil and water.In low water cut of oil and water system, calcium sulfate scale will be inhibited when150～200mg/L HTSI is added in the system. When the temperature of interface is at347℉, ratio of scaling inhabitation reaches more than97%; when the temperature ofexchanging medium is at374℉, ratio of scaling inhabitation can get73%.This paper also raised the suggestions of modifying the process to preventscaling, lower down the temperature of heat exchanging medium, speeding up the rateof fluid will slow down the blocking of scaling, or to choose more effective heater toshorten retention time which will beneficial for slowing down the scaling of heater.