An Evaluation of the Applicability of the Steady-State Productivity Approach for Horizontal Wells in Low-Permeability Heterogeneous Gas Reservoirs

The heterogeneity and complexity of low-permeability oil and gas reservoirs pose significant technical challenges for their efficient development, including reservoir plugging, high flow resistance, and optimal well type design issues. These challenges result in high development costs and extended production cycles due to insufficient productivity of oil and gas wells. Therefore, accurately assessing the applicability of horizontal wells and their design parameters in the development of low-permeability reservoirs through oil and gas well productivity prediction has become a pressing key issue that needs to be addressed. In this study, based on the principle of well type optimization in the development of low-permeability oil and gas reservoirs, the adaptability of horizontal wells is evaluated using steady-state productivity methods, and their stimulation effects are predicted and analyzed. A systematic comparison of the steady-state productivity of horizontal wells and vertical wells is conducted, productivity predictions for different types of gas reservoirs are conducted, the design parameters of horizontal wells (highly deviated wells) are optimized, and a well type adaptability evaluation system suitable for different reservoir characteristics is formed. The research findings indicate that vertical wells are preferable for gas wells when the steady-state productivity ratio (HRV) is less than 1. However, when the HRV is greater than or equal to 1, the benefits of horizontal and highly deviated wells become notably superior to those of vertical wells. Taking into account the output value, cost, and net income of the gas well, the optimal outcome is achieved with a horizontal section length of 800 m. Ultra-low-permeability thick reservoirs are best suited to vertical wells, low-permeability thick reservoirs to highly deviated wells, and low-permeability thin reservoirs to horizontal wells. The assessment of steady-state productivity offers a theoretical foundation for optimizing development plans in low-permeability oil and gas reservoirs.