A Study of Swirling Jet Drilling and Its Specific Energy for Hydrate-Bearing Sediments
Yiqun Zhang, Xiao Hu, Xiaoya Wu, Gensheng Li, Jingbin Li, Shoucheng Tian, Kaixiang Shen
Abstract
Summary Natural gas hydrate (NGH) is a form of clean energy. The marine NGH solid fluidization exploitation method and the integrated radial jet drilling and completion method are considered as two ways to improve gas production, and water jet is the key technology of the two mining methods. This paper first compared the flow field distribution of conical jet and swirling jet at different outlet velocities through numerical simulation. The volume change of conical jet and swirling jet erosion hydrate-bearing sediment (HBS) was analyzed when the jet outlet velocity and standoff distance were changed. Then, based on the experimental apparatus for NGH generation and jet erosion, we carried out the swirling jet erosion HBS experiments. The depth and diameter of the erosion pits were about 10% larger than the numerical simulation. Finally, we evaluated the jet erosion performance with specific energy calculations. The results show that the reaming ability of the swirling jet is 2.4 times than that of the conical jet at the jet velocity of 100 m/s and the standoff distance of 5 mm. When the jet velocity ranges from 30 to 100 m/s, the erosion efficiency of the swirling jet is higher than that of the conical jet. The critical standoff distance is calculated as 12.5 mm (12.5 times nozzle throat) in current study, larger than which the advantages of swirling jet erosion HBS become less obvious. The excellent performance of swirling jet erosion HBS under certain conditions is described by specific energy calculation. This study can help for better understanding the performance of water jet drilling and provides an idea for improving the production efficiency of NGH.