Experimental Study on Evolution Patterns and Influencing Factors of Blowout Plumes in Deepwater Open-Circuit Drilling

Deepwater oil and gas development is an important part of the oil and gas extraction field, among which open-circuit drilling technology (riserless drilling technology) is a widely used, safe and efficient deepwater shallow drilling technology. During this period, the problem of blowout caused by drilling shallow gas formations was particularly prominent. The shallow gas stored in the formation after a blowout will invade the wellbore and upwind under the drive of the pressure difference between the formation and the wellbore, and then spray into seawater to form a plume. In severe cases, it will migrate and spread to the vicinity of the platform, posing a serious threat to the safety of offshore drilling platform operations. Therefore, it is necessary to finely characterize the evolution patterns of the blowout plumes under different operating conditions. An experimental apparatus and method for the formation and evolution of plume after a deepwater open-circuit drilling blowout were designed based on similarity criteria, revealing the laws of plume formation and evolution after a blowout and clarifying the key influencing factors of plume movement after a blowout. The results indicate that after the fluid is ejected, it undergoes a process of turbulent jet entrainment bending convection diffusion, developing into a plume flow with a narrow bottom and a wide top. When the gas flow rate is 0.2 m/s, the offset angle range is 3.5–14.9° under weak cross flow conditions, and 9.4–20.8° under strong cross flow conditions; When the gas flow rate is 0.7 m/s, the offset angle range is 3.7–5.2° under weak cross flow conditions, and 4.3–14.5° under strong cross flow conditions. Overall, the initial offset angle of the plume is inversely proportional to the gas flow velocity and directly proportional to the nozzle diameter. The results of this study can lay the foundation for the study of the formation and evolution laws of blowout plumes.