Mechanism and Characteristics of Horizontal-Wellbore Cleanout by Annular Helical Flow

Summary Horizontal-wellbore cleanout by rotating jets and annular helical flow has developed rapidly in past decades, in which the annular helical flow is one of the most significant factors to transport the solids in a horizontal wellbore. Because of its complexity and lack of research approaches, the mechanism and characteristics of annular helical flow by high-pressure jets were never revealed comprehensively. By the computational-fluid-dynamics (CFD) method, the flow field of annular helical flow (such as its generation, continuation, and attenuation) was first manifested. The axial velocity and tangential velocity vary regarding cleaning distance, flow rate, and nozzle assemblies. Furthermore, the dynamic simulation of sandbed sweeping by rotating jets and annular helical flow in a horizontal wellbore was accomplished, and the influences on sweeping efficiency were discussed. Finally, the recommended nozzle assembly and its flow-rate distribution in front jets, lateral jets, and rear jets were provided. This study is beneficial in designing the cleaning tool and in optimizing the hydraulic parameters and operation procedures.