Optimization and analysis of gravel packing parameters in horizontal wells for natural gas hydrate production

Highlights: • Gravel packing parameters in horizontal wells for marine NGH production are studied. • Safe operational window becomes narrower with the decrease of hydrate saturation. • Lightweight gravels are effective to prolong the maximum packable horizontal length. • Multiple β-wave packing widens safe operational window and improves packing safety. Horizontal well is preferred for marine natural gas hydrate (NGH) production, while a robust completion method is required to control the associated sand production. In this paper, technical challenges, evaluation workflow, and deployment constraints of gravel packing in horizontal wells for marine NGH production are comprehensively analyzed. A virtual horizontal well located at the site SH2, northern South China Sea is involved to optimize packing operation parameters and analyze factors that affect the safety and effectiveness of packing operation. The results indicate that the extremely narrow safe operational window and high fluid-loss ratio are the main obstacles that affect packing effectiveness in marine NGH production horizontal wells. The safe operational window becomes narrower with the decrease of hydrate saturation within the reservoir; hence, the packing failure risk increases significantly. As for the virtual horizontal well located at the site SH2, the safe operational windows are 1.38–1.56 m³/min and 1.38–1.82 m³/min given the average hydrate saturation is 30% and 70%, respectively. However, the horizontal well is unpackable when hydrate saturation is less than 15%. Furthermore, the maximum packable lengths in horizontal wells for marine NGH production are found to be affected by hydrate saturation, fluid-loss ratio, gravel density, gavel concentration, and density/viscosity of sand-carrier. A joint application of lightweight gravel, low concentration slurry, viscosity reducer additives, and multiple β-wave packing technique could prolong the maximum packable length.