Analysis of typical cases of corrosion failure of tubing in heavy oil fire-flooding production wells

Abstract

A corrosion failure of tubing often occurs during the production process of production wells in heavy oil fire-flooding blocks and thus affects service safety. In the study, the service information of tubings in fire-flooding blocks was analyzed and the physical and chemical properties of defunct tubings were determined. In addition, the causes for the failures of series tubings with wall thickness thinning and corrosion perforation were revealed by SEM, EDS, and XPS. The common corrosion types of tubings and the inducing factors of different failure forms were clarified and corresponding anti-corrosion suggestions were given. The material of defunct tubings was not the failure cause. When high-temperature gas channeling and unburned O₂ occurred, corrosion was intensified by a high content of Cl⁻, thus resulting in the corrosion failure of series tubings with serious wall thickness thinning. When a high content of Ca^2 + existed in formation water, a CaCO₃ scale layer was formed to adhere to the outer wall of the tubing and aggravate local corrosion under the action of a high content of Cl⁻. This above process was the cause for corrosion perforation. CO₂/H₂S corrosion generally occurred in the tubings of fire-flooding production wells. The inducing factors of tubing failures included high-temperature gas channeling, unburned O₂, a high content of Ca^2 +, and a high content of Cl⁻. It is recommended to use imidazoline corrosion inhibitor XCN-ZO2 and annular outer wall aluminum-based sacrificial anode anti-corrosion short sections for corrosion protection.