Transient Pressure Fluctuation Effect During Gas Drilling in Horizontal Well

Combining gas drilling technology with horizontal well drilling leads to improvement in production in oil and gas reservoirs. However, wellbore gas encountering high-pressure formation gas could bring substantial risks in gas drilling process. A theoretical model for pressure wave speed and attenuation coefficient in gaseous phase flow is established and analytically solved by classic fluid-mechanics model and small perturbation theory. The simulation results suggest that the main factors affecting the pressure wave are angular frequency, pipe diameter, and original pressure. In addition, a pressure wave test device is designed to validate the model, and the experimental results fit well with the simulation results. The work presented in this paper can provide a theoretical basis for horizontal section gas drilling and can also detect gas influx to ensure safety and prevent accidents.