Theoretical study on liquid drainage technology with nitrogen by coiled tubing

Bottom hole liquid loading is the primary factor leading to the reduction of single well production rate and reservoir pollution. So how to drain the bottomhole liquid rapidly and effectively is the key to ensure the normal development and production of oil and gas field. By analyzing two methods of liquid drainage technology widely adopted in the field, we put forward the optimization design process of liquid drainage with nitrogen by coiled tubing in this paper. In addition, according to the intermittent flow operation, we developed a maximum liquid drainage index model. Optimal design of maximum average produced fluid volume, minimum nitrogen injection rate and optimum time interval of liquid loading and their application were described also. In this technology coiled tubing is adopted instead of common operation string to drain the fluid with nitrogen. The technology has important populized values for the liquid drainage of deep and complex oil-gas wells due to these characteristics including convenience, no limitation of well pattern, flexible gas injection point and gas injection rate and short operation cycle.