Development of a Dual-Measured-Points Early Gas Kick Detection Method based on the pressure responses of two PWD tools

Early gas kick detection is an important measure to ensure well control safety. In this paper, firstly, a new two-phase flow model was developed to accurately describe the transient annular pressure responses at the PWD tool during the gas influx. Secondly, a Dual-Measured-Points Early Gas Kick Detection Method was proposed based on the consistency and discrepancy between the pressure responses of two PWD tools. The results of case research indicated that the annular pressure increased and changed periodically with time in the initial stage of gas kick and then declined approximately linearly after the gas-liquid interface reached the PWD tool. Additionally, the proposed gas kick detection method could significantly reduce the chances of the gas kick misdiagnosis and improve the reliability of the gas kick detection. Moreover, the gas kick confirmation time (GKCT) obtained by the proposed method was 2–7 min, and the corresponding gas kick confirmation volume (GKCV) was 0.3–0.5 m3. The GKCT diminished with the increase in the formation permeability and the bottomhole pressure difference and with the decrease in the borehole size and the well depth.