| Popis: |
With the development of Fire Flooding test, serious corrosion occurred in N80-steel based tubing and casing string and caused severe damages. Wellbore integrity is getting worse, which gives rise to the abandonment of a well section or the whole well. This problem has seriously hampered the fire flooding development. In this research, the component analysis is first applied to the injection and production gas samples of fire flooding well groups, to determine the reaction mechanism and the main corrosion factors of wellbore tubing and casing string. Then, corrosion dynamic simulation experiments are carried out by the first domestic self-developed experimental device of fire flooding corrosion simulation. Corrosion rate of various string pipes under fire flooding conditions with different gas component is simulated and measured quantitatively by using the traditional weight loss method and inductance probe method, aiming to determine the dynamic corrosion degree during the process of fire flooding, and meanwhile the evaluation on the new developed chemical corrosion inhibitor is implemented. For new wells, the anticorrosive materials for casing and tubing is selected according to test results, and the optimal design of completion casing is carried out, to ensure the injection and production wellbore integrity and anticorrosive performance in the development process. For corrosion wells, chemical corrosion inhibitor was developed, and the dynamic simulation and evaluation of corrosion resistance was carried out by means of the fire flooding simulated corrosion model experiment device. The experimental results show that the corrosion rate of N80 steel can be reduced to 0.0687mm/a when the concentration of corrosion inhibitor is 500ppm. This corrosion rate can meet the need of field development. Field tests show that the above measures can effectively prevent or delay the casing and tubing corrosion damage, and extend the service life of fire flooding wells. The fire flooding wellbore corrosion dynamic simulation experimental device has completely changed the current situation of qualitative corrosion evaluation on casing and tubing in the field and realized quantitative evaluation on corrosion damage of tubing and casing. The results of quantitative evaluation provide the basis for optimal design, anticorrosive performance and integrity of wellbore. |
