It is critical to maintain stability of hydrate bearing sediments for safe and successful drilling. Changes of pressure and temperature distributions can trigger formation instability due to hydrate dissociation. In order to prevent such problems, it is necessary to model the behavior of hydrate bearing sediments. In this study, a real-time model of drilling through hydrate bearing sediments has been developed. The developed model can predict distributions of in-situ temperature, pressure, hydrate saturation, and gas saturation while drilling. Several simulations are conducted in the environment of gas hydrate formation in Ulleung Basin, the East Sea of Korea under various drilling and formation conditions. Guidelines for the safe drilling ranges can be provided by analyzing the simulation results.