Titanium alloys have now become the first choice of tubing material used in the harsh oil- and gas-exploitation environment, while the interaction of force and medium is a serious threat to the safety and reliability of titanium alloy in service. In this paper, different stresses were applied to TC4 titanium alloy by four-point bending stress fixture, and the corrosion behavior of TC4 titanium alloy was studied by high-temperature and high-pressure simulation experiments and electrochemical techniques, and the microscopic morphologies and chemical composition of the surface film layer on the specimen were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), to reveal the corrosion-resistance mechanism of TC4 titanium alloy under different stress-loading conditions. The results showed that the pits appeared on the specimens loaded with elastic stress, but the degree of pitting corrosion was still lighter, and the surface film layer showed n-type semiconductor properties with cation selective permeability. While the pits on the specimens loaded with plastic stress were deeper and wider in size, and the semiconductor type of the surface film layer changed to p-type, it was easier for anions such as Cl⁻ and CO₃²⁻ to adsorb on, destroy, and pass through the protective film and then to contact with the matrix, resulting in a decrease in corrosion resistance of TC4 titanium alloy.

The System #2 flow loop used in this study is a 4−inch−diameter, high−temperature, high−pressure system. In situ corrosion and electrochemical measurements were performed using a homemade flat corrosion specimen and a three−electrode probe. The experiment results show that temperature has an accelerated influence on the corrosion of antibacterial alloy steel. With the increase of temperature and the presence of O₂ in the environment, a loose and porous corrosion product film was formed on the surface of the resistant steel, which made it easier for the corrosion medium to enter the corrosion product film from the pore, thus accelerating the corrosion.

In oil and gas field development, the highly mineralized formation water environment often leads to casing corrosion, significantly reducing its collapse strength and service life. To investigate the corrosion characteristics and mechanical degradation of casings in formation water, this study combines high-temperature high-pressure (HTHP) corrosion experiments with finite element analysis to examine the influence of corrosion pit geometry and volume loss on casing collapse strength. Based on experimental data and simulation results, the safe service life of casing under various conditions is also predicted. The results show that greater material loss due to corrosion leads to lower collapse strength. Under the same volume loss, cylindrical pits cause the most severe reduction in collapse strength, while semi-ellipsoidal pits result in the least degradation. Elevated temperature and pressure significantly accelerate corrosion and further reduce mechanical performance. Under service conditions of 20 MPa–80 °C, 11 MPa–50 °C, and 2 MPa–20 °C, the predicted safe service life of the casing is 4.84, 7.57, and 11.61 years, respectively. The approach proposed in this study provides a reference for the evaluation of collapse resistance and service life prediction of casings exposed to formation water environments.

Single well output is poor in several Yanchang oilfield development blocks, water content is high, and hydrogen sulfide is present at the same time. The tank corrosion in the on-site multiphase time-sharing flow sewage system was severe. The coupon method was used to test the corrosion rate and the scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) methods were used to study the corrosion morphology of the coupon and analyze the composition of the corrosion products in order to effectively inhibit corrosion in the storage tank and analyze the physical and chemical properties of the sewage. The corrosion rates of the upper, middle, and lower sections of the incoming water tank increased and subsequently decreased, whereas the corrosion rates of the upper, middle, and lower parts of the filtered water tank decreased. Local corrosion, pitting corrosion, and pit corrosion were observed in the storage tank, with the corrosion products mostly being Fe₂O₃, FeS, and FeS₂. It was determined that the primary corrosion causes in the top section of the carbon steel storage tank were dissolved oxygen and Cl⁻, sulfur (H₂S) and SRB, and SRB in the bottom part. The combination of bacterial, hydrogen sulfide, and oxygen corrosion created the corrosion process.