Study on Lifting Efficiency of Cuttings in Return Line of Riserless Mud Recovery System

The exploration and development of offshore oil could cause a certain degree of damage to the marine ecological environment. To develop an offshore oil exploration and development technology that can protect the marine environment has always been focus of oil companies. The riserless mud recovery (RMR) system uses subsea pump to lift the drilling cuttings generated in the process of drilling operation to the drilling platform along the return line, so as to achieve zero discharge of drilling cuttings in the marine environment, which is an advanced drilling technology conducive to marine environmental protection. The lifting efficiency of cuttings in the return line will directly affect the efficiency of drilling operations, thus affecting the cycle and cost of drilling engineering. Based on the above problems, this paper establishes the mathematical model of the force and movement of the drilling cuttings in the return line by combining the working characteristics of the RMR system, and analyzes the influence of the change of the inner diameter of the return line, the density of the cuttings, the diameter of the cuttings, the flow behavior index and the consistency index of the drilling fluid on the lifting efficiency of the cuttings in the return line, providing theoretical basis for the optimization and improvement of the RMR system.