Optimal angle design and techno-economic evaluation methods of deep-sea pipelines within gas and oil transportation

• Assessment of the risk of hydrate blockage in inclined pipelines. • Analysis of energy loss in inclined pipelines. • Calculation of laying costs for different inclination laying schemes. • An integrated approach to the evaluation of submarine pipeline laying schemes. As global energy demand climbs, the scope and depth of exploitation of submarine oil and gas resources continue to expand. The conditions for constructing deep-sea oil and gas pipelines have become increasingly complex. During long-distance transportation, the undulating terrain of the seabed increases both the technical challenges of pipeline installation and the associated safety and economic concerns. This paper systematically analyzes the risk of pipeline transportation at various inclination angles while comparing energy loss and laying costs. The analysis results indicate that the pipeline has the highest risk of blockage, energy loss, and laying cost at 3°, the lowest risk of blockage and energy loss at 12°, and the lowest laying cost at 15° Compared to the 3° pipeline, the 12° pipeline reduces energy loss by 63.1 %, and the 15° pipeline reduces laying costs by 79.8 %. Based on experimental results, this study integrates hydrate blockage risk, energy loss, and cost estimation to propose a comprehensive analytical model for evaluating inclined laying schemes of subsea oil and gas transportation pipelines. The findings can guide offshore engineering teams in selecting pipeline inclinations that reduce operational risks and optimize costs under varying seabed conditions.