Enhancing gravel packing efficiency in horizontal wells with nitrogen foam: A numerical simulation study for weakly sandstone reservoirs

Abstract

Gravel packing is a widely used sand control technique in oil and gas wells, especially in horizontal wells, where formation instability and well deviation create significant challenges. Conventional gravel packing with Newtonian fluids often faces issues such as premature sand bed plugging, excessive operational stress, and an increased risk of formation fracturing. To address these limitations, this study systematically examines the rheological behavior of nitrogen foam under varying temperature and pressure conditions, developing a viscosity prediction model based on experimental data. By integrating classical fluid mechanics with granular flow theory, a refined three-layer hydraulic flow model is introduced to simulate the nitrogen foam gravel packing process. Numerical simulations assess the impact of key parameters—including gravel size, foam quality, foaming agent concentration, pump flow rate, and sand concentration—on packing efficiency. Experimental results show that at an SDBS (Sodium dodecyl benzene sulfonate) concentration of 1.5 %, nitrogen foam achieves optimal foaming performance and strong sand-carrying capacity. Using a field oil well as a case study, simulations indicate that optimized parameters, including a pumping rate of 65 m³/h, gravel density of 1600 kg/m³, foam quality of 67 %, and a sand concentration of 7.5 %, significantly enhance packing efficiency. Field validation in Well P15 of the high-fluid-loss Gudong reservoir in the Shengli Oilfield confirms that these optimized conditions achieve a packing rate of approximately 97.53 %. This study provides a solid foundation for applying nitrogen foam in gravel packing for horizontal wells, offering valuable insights into its rheological behavior, transport mechanisms, and field applicability.