Risk assessment and control technology for deep water and shallow gas drilling

Shallow gas is often encountered during the development of deep-water oil and gas fields. Shallow gas is an overpressure gas accumulated on the seabed. Due to the prediction difficulty and few control methods, the area where shallow gas exists is usually avoided by changing well positions. This restricts the site selection of drilling wellheads, and even fails to achieve the purpose of reservoir exploration. Based on ANSYS Fluent software, by using VOF model and k-ε turbulence model, a calculation model for transient multiphase fluid flow when shallow gas blowout was established, and the shallow gas blowout features under the conditions of different pressure coefficients, reservoir scales, and wellbore sizes were obtained. Based on the gas flow characteristics and the reservoir scale, a numerical model of shallow gas blowout was established, and a prevention and control method of adopting active blowout technology for shallow gas at medium and high-risk level was put forward. This research has theoretical guiding significance for actively responding to potential geological disasters caused by shallow gas.