Study On Corrosion Behavior Of Polymer Flooding Well In A Certain Area Of Xinjiang Oilfield

In recent years,as the global demand for oil and gas resources continues to rise,polymer flooding has become a popular new technology for enhanced oil recovery,with very good application prospects,but there are also many problems to be solved.The first problem facing the problem is the corrosion of the shaft of the wellbore.At present,for the corrosion problem of polymer flooding wells,the related research only focuses on the unilateral effects of the polymer itself or the corrosive environment,and the environmental cracking performance and weight loss corrosion performance of the wellbore material are not carried out.Overview.Based on the current situation of the production process in a certain area of Xinjiang Oilfield,the wellbore contains polyacrylamide polymer,the formation produces CO2 and H2S gas,and the anti-sulfur steel is not used.This paper aims to extract the oil casing and pumping oil from the wellbore in this area.The conventional performance of the rod,the resistance to environmental cracking and the weight loss and corrosion resistance of N80 oil casing steel are explored.The specific research work is as follows:(1)The conventional properties of two oil casing materials(N80 steel and P110 steel)and H-stage sucker rod materials were tested to obtain the corresponding chemical composition,metallographic and inclusion analysis,hardness and tensile properties,and impact properties.The results show that the chemical composition of N80 steel and P110 steel meets the requirements of API SPEC 5CT standard,the chemical composition of H-class sucker rod meets the requirements of GB/T 26075-2010;the microstructure of P110 is tempered sorbite,the grain size is Grade 10,N80 metallographic structure is pearlite and ferrite,grain size is 9 grade,H-bar metallographic structure is tempered sorbite and ferrite,grain size is 10;P110 steel and H-stage sucker rod have greater strength and hardness,and the toughness of the N80 is good.(2)The anti-H2S stress corrosion cracking performance test of P110 and N80 oil casing steel in NACE A solution and H-stage sucker rod in simulated solution was carried out.The causes and processes of P110 steel fracture and N80 stress corrosion damage were discussed.The relationship between rod stress corrosion cracking sensitivity and H2S and polymer.The results show that the P110 constant load specimens are all broken at 3d,and the N80 C-ring specimens pass through the 720h experimental period.Although there is no fracture,all the specimens have visible microscopic cracks on the force surface,and the crack direction is perpendicular to the stress.In the direction,the anti-H2S environment cracking performance of N80 steel is better than that of P110 steel;the high-strength H-stage sucker rod has certain H2S environmental fracture sensitivity,and its sensitivity increases with the introduction of H2S,and the presence of polymer,Reduce its H2S stress corrosion sensitivity.(3)Polyacrylamide concentration(300ppm?1200ppm),chloride ion concentration(5000ppm?20000ppm),hydrogen sulfide concentration(300ppm?1200ppm),wellbore temperature(20??80?)to the production well were studied by static high temperature autoclave The corrosion behavior of N80 oil casing steel was obtained,and the corrosion law of oil casing steel under different influencing factors was obtained.The results show that under liquid phase conditions,the corrosion rate of N80 oil casing steel decreases with the increase of polymer concentration,and increases with the increase of chloride ion concentration,hydrogen sulfide content and wellbore temperature.Temperature is the main influencing factor of corrosion.Under gas phase conditions,the corrosion rate of N80 oil casing steel increases with the increase of hydrogen sulfide concentration,and it increases first and then decreases with the increase of wellbore temperature.Both factors have significant effects on corrosion.The research results of this paper provide a reference for the evaluation of the corrosion risk and corrosion degree of the current polymer injection flooding wellbore in a certain area of Xinjiang Oilfield.It has important theoretical significance and practical application value for solving the corrosion problem in the process of polymer injection flooding.