A rigorous method to calculate the rising speed of gas kick

Abstract

The rising speed of gas kick is an important parameter in well control operation. The position of the gas kick dictates the pressure at the casing shoe, which is usually the weakest point in the openhole section, and the wellhead pressure, which is one of the key factors affecting the blowout preventer and choke folder. In this research, we derived a rigorous model to estimate the rising speed of gas kick. Starting from the force analysis and mass conservation, we developed equations to calculate the forces exerting on the gas kick. With the mass of the gas kick, the rising speed of the gas kick is calculated. The effect of wellbore temperature profile on the rising of the gas kick is taken into account in the derivation. Before the development of this model, the estimation of gas kick position is commonly based on experience. In many cases, the experience alone is not good enough for well control. The proposed model provides a new approach with solid theoretical base to characterize the rising of gas kick in the hole. It makes the procedure of the well control simple and makes drilling engineers feel more comfortable to control the well. The new model can be combined with engineers experience to predict the downhole situation, shut-in casing pressure, and mud rate as a functions of position of gas kick. Any deviation from the forecast indicates accidents or downhole problems. Therefore, the proposed model is a valuable tool to diagnose the problems in well control.