Study On Riserless Mud-lift Drilling System Design And Control Unit

Dual-gradient drilling technology can solve the problems associated with deepwaterdrilling in theory. Among all the implementation methods, only riserless drilling technologyobtains a wide range of commercial applications at abroad, and access to significant economicand environmental benefits. The paper supported by the project of “Research on SubseaMud-lift Drilling Technology (2008ZX0526-001-12)” sponsored by National Science andTechnology Major Special Project. Undertakes the research of riserless drilling technologydesign and control unit, which is meaningful to the system. The main work is summarized asfollows:1. Proposals for riserless drilling technology in different water depthBased on studying of related technology abroad, combined with500-1500m water depthdrilling environmental characteristics, put forward new proposals for riserless drillingtechnology in different water depth. It includes the overall program, major equipment, drillingprogram, technical characteristics and so on.2. Design of subsea mud-lift systemThe biggest difference between riserless drilling technology and conventional riserdrilling technology is whether owns subsea mud-lift system on not. The system is the keychallenges of the technology. The mud return pipeline Hydraulic parameters were got byHydraulics calculation. It’s a basis for design of power systems and signal communicationssolutions. Mechanical analysis was done to obtain structural parameters of mud returnpipeline and seabed anchor block.3. Well control of riserless drilling technologyDue to the special nature of riserless drilling technology, it exists the situation that drillpipe can’t be filled with drilling fluid. There is U-tube effect after the pump on deck stopped.We do wellbore hydraulics calculation to obtain the flow of drilling fluid and the wellpressure situation under different conditions. We also study the response program of U-tubeeffect and the shallow-job accident.4. The shallow riserless drilling technology test systemWe build a test platform to simulate shallow riserless drilling technology. It can getequipment performance parameters and simulate well control. The hardware part includesmain equipments, a circuit consisting of sensors and controllers, signal transmission system and so on. The software part includes data acquisition and storage, pump start and stop andthe liquid level control, normal drilling conditions control, well kick and leakage detectionprogram.