Xinghua Zhang

In the process of acidizing operation, especially in ultra-high temperature wells, metal components such as wellbore tubing and surface equipment are severely corroded by acid fluids, leading to operational challenges in oilfield production. At present, the ad-dition of corrosion inhibitors is one of the most effective methods to mitigate metal corrosion. Pyridine residues, quinoline quaternary ammonium salts, aldehyde ketone amine condensates, acetylenic methyl ammonia and imidazoline corrosion inhibitors have been widely studied in the industry. Among them quaternary ammonium salts are widely used in oilfield production due to their excellent corrosion resistance, low toxicity and good water solubility. However, their limited heat resistance makes them unsuitable for ultra-deep exploration wells or scientific research wells. This study fo-cuses on N-heterocyclic quaternary ammonium salt-based corrosion inhibitors (alkyl quinolinium quaternary ammonium salts), which can withstand temperatures up to 200°C, meeting the requirements of ultra-high temperature wells.

Gravel sandstone reservoirs are characterized by low porosity, low permeability, and strong heterogeneity, presenting significant challenges for hydraulic fracturing. This study investigates the fracture propagation mechanisms in gravel sandstone formations using a combination of laboratory experiments, numerical simulations, and theoretical modeling. The findings reveal that gravel size, strength, and distribution significantly influence fracture morphology and propagation behavior. Under low stress differences, cracks tend to wind around gravel, while under high stress differences, cracks are more likely to penetrate gravel. Numerical simulations highlight the complex fracture network caused by high gravel content, leading to increased filtration loss, accelerated energy dissipation, and reduced fracture length. A quantitative model was developed to describe trans-gravel behavior, offering theoretical support for optimizing hydraulic fracturing designs in gravel sandstone reservoirs. This work provides valuable insights into the coupling mechanisms between gravel properties, stress conditions, and fracture propagation, contributing to more effective stimulation strategies for complex reservoirs.

The sand conglomerate has strong heterogeneity, great difference in rock mechanical properties, and serious filtration loss of fracturing fluid. In order to describe the effect of heterogeneous gravel distribution on the filtration loss of conglomerate reservoir, a dual media filtration model was established based on the equivalent flow principle, and the heterogeneous distribution relationship was characterized by Fuller gradation and solved by numerical method. The degree of non-uniformity, formation gravel characteristics and pressure process parameters were taken into account for simulation analysis and calculation. The results show that the average filtration rate of 60% gravel content is 54.2% lower than that of 20% gravel content. When the degree of non-uniformity is 6, the average filtration rate is 73% higher than that of uniformity. Injection rate and injection pressure have a great influence on the filtration loss of fracturing fluid. The research results can provide theoretical support for fracturing optimization design.

The electric heating process for lifting heavy oil has been widely applied. However, research on its temperature field laws mostly focuses on onshore heavy oil wells, while research offshore is limited. Therefore, based on the energy conservation equation and heat transfer theory, a transient one-dimensional wellbore temperature model coupled with the temperature and viscosity of heavy oil and considering the effect of time was developed. In order to verify the accuracy of the model, the results of the previous model were used for comparison with the present model, and the results showed that the model has good accuracy. The results show that a reasonable selection of the process parameters of electric heating can increase the production of heavy oil while saving development costs and improving the economic benefits of the oilfield. The conclusions and recommendations of this paper can provide a theoretical basis and guiding suggestions for the optimal design of process parameters for lifting heavy oil using an offshore electric heating process.