There are cracks and karst caves development in carbonate formations. If we still follow the security pressure of drilling fluid density in accordance with the conventional formation fracture pressure, the leakage is susceptible to be formed. Based on the different mechanisms, the leakage pressure considering the burst leakage pressure and natural leakage pressure is proposed, and then we put forward the calculation model of the two type leakage pressures. According to the model predictions of Halahatang sag X1 well’s leakage pressure, we can ascertain that the model can meet the requirement of engineering.