Study On The Effect Of Elemental Sulfur In Sour Gas Field On The Anti-corrosion Effect Of Corrosion Inhibitors

As the exploitation process of sour gas well continues,sulfur deposition occurs with the abrupt change in temperature and pressure and absorbs at metal matrix,resulting in severe corrosion.Corrosion inhibitor,as an economic efficiency anticorrosion method,can be widely used in high sulfur-containing gas field.However,the performance of corrosion inhibitor film in the flow field is weaker than that in static environment.Corrosion inhibitor film can easily be exfoliated from the surface of metal and lose the corrosion inhibition due to the shear effect of flowing medium.Therefore,aiming at the sulfur deposition corrosion of high sour gas field,several researches have been conducted.Fluent software was used to establish simulation models of oil tube and high temperature and high pressure(HTHP)autoclave multiphase flow corrosion tester.The wall shear stress distributions of oil tube and specimen have been obtained under the multi-phase flow erosion effect.The results show that the wall shear stress of oil tube increases with the increasing of produced gas production,water production and sulfur solid mass production.In addition,the wall shear stress increases with rise in rotation rate.HTHP autoclave multiphase flow corrosion tester has been employed to study the corrosion of anti-sulfur carbon steel under different sulfur containing conditions and the corresponding corrosion prediction model has been established.Deep analysis technologies(SEM and EDS)were used to evaluate the corrosion inhibition effect and sulfur corrosion influencing factors.The results show that sulfur will absorb on the surface of steel and destroy the integrity of corrosion inhibitor film,resulting the localized risk.Sulfur corrosion rate of steel will be greatly affected by the addition of sulfur,corrosion period,wall shear stress and sulfur forms.Electrochemical workstation(model CS350)has been used to study electrochemical corrosion mechanism of SMC110 at normal temperature and atmospheric pressure.Besides,the effect of environmental factors on electrochemical corrosion of SMC110 were obtained.As the sulfur content and bond between sulfur and metal matrix increase,and the cathodic tafel slope,corrosion current density gradually increase,resulting in increasing cathode polarization effect.In addition,the addition of JS corrosion inhibitor makes the corrosion current density and corrosion potential increase,demonstrating that it has great protection effect of matrix due to its good cathodic reaction inhibiting effect.