Research On The Corrosion Rule Of Wellbore In Jingan Sulfide Oilfield And Its Countermeasures

During the exploitation of the Jingan Oilfield,the wellbore of the oil well is particularly corrosive.Leakage of liquid,perforation of the tubing,and disconnection of the sucker rod often occur.This poses a huge obstacle to the normal production and economic efficiency of the Jingan oil field.Therefore,it is necessary to analyze the wellbore corrosion mechanism in Jingan oilfield,study the law of wellbore corrosion,and formulate corresponding anticorrosion measures based on this.Firstly,analyze the wellbore corrosion environment in Jingan oilfield;select corrosion-resistant tubing and sucker rod materials through on-site corrosion monitoring;determine the main influencing factors of wellbore corrosion by grey relational analysis;and study the extent of impact on wellbore corrosion;The chemical method was used to evaluate corrosion inhibitors,weight-loss method was used to evaluate the corrosion inhibitors with better screening effect,and a sucker rod column combination method was designed to achieve tensile strength.Research indicates:(1)The output of Jing ' an Oilfield has a high moisture content,a weakly alkaline production fluid,a p H of 8.32 to 9.59,a salinity of 10143 mg/L-25949 mg/L,and a high sulfide content of 35 to 385 mg/L.The content of scale-forming cations Ca2+ and Mg2+ is small,and there is a tendency of hydrogen sulfide and chloride ions to corrode.(2)The corrosion rate of the tubing and sucker rods are all higher than 0.254 mm/a,and there is severe pitting behavior.The corrosion products are mainly Fe S.The tubing material J55 and the sucker rod material 4330 A have the best corrosion resistance and pitting resistance.(3)The major factors affecting wellbore corrosion are sulfide,Cl-,and p H.With the increase of sulfide and Cl-content,the average corrosion rate of J55 increased;p H decreased and corrosion progress increased.(4)Three kinds of sulfur-inhibiting corrosion inhibitors No.7,No.11 and TS-1719 were screened out from 21 inhibitors.And its performance in the oil loss,sulfur resistance,temperature performance evaluation and the best amount of the determination,No.7 and TS-1719 are better than the 11 th,and when the corrosion inhibitor dosage is 100mg/L The effect is best;at 50?and 80?,the corrosion inhibition rate of No.7 and TS-1719 can reach.more than 90%,and the corrosion inhibition rate of No.11 is between 40% and 70%.It is recommended to use No.7 in the field.And TS-1719 corrosion inhibitor.(5)The currently used sucker rod tensile strength Rm is less than the rated tensile strength of class D rod(965MPa),elongation A and reduction of area Z are less than 10% and50%,respectively;newly designed sucker rod combination method The tensile strength can meet the strength requirements after being checked;the total consumption cost of the 4330 A rod in 10 years is 258,000 yuan,which is the lowest among the four materials;the newly-designed pumping oil is aimed at the oil well with the most severe corrosion.Compared with the old combination method,the cost of the rod combination method was reduced by122,900 yuan/year.