2/19/2023 0 Comments Directional drilling technology![]() ![]() These methods typically require the drill string to turn (via kelly or top-drive), but have computerized active directional controls located at the bottom of the drill string above the drill bit. Reverse circulation is not compatible with some modern drilling approaches (e.g., downhole mud motors or hammer drilling) or would require specialized equipment.įor directional control, several different types of hybrid rotary steerable systems have recently emerged. Very large borehole diameters sometimes require reverse circulation to effectively remove cuttings, since mud flow velocities drop off as the annulus diameter increases (larger cuttings fall out of the mud when it slows down), while velocity in the drill pipe remains high. This approach often results in more depth-specific cuttings retrieval than direct circulation, where mud circulates up the borehole annulus. ![]() Pumping mud down the drill string (i.e., direct circulation) then turns the pump, which translates into torque applied directly at the drill bit.īoth top-drive and kelly-drive systems can be configured to utilize reverse circulation, which pumps the drilling mud up the drill pipe, rather than down the drill pipe. In these systems the drill pipe is not rotated a positive displacement motor is part of the bottom of the drill string above the drill bit. While this is mechanically more complex than using a stationary kelly system, more control is allowed to the drilling operator, including applying rotation while pulling up.ĭownhole mud motors are a modern alternative method for applying torque to the drill bit. The rotary motor assembly moves up and down the drill rig mast during drilling operations. These involve the rotary motor being directly connected to the drill pipe at its top. More recently, top-drive motors have been utilized to turn the drill string. Pipe is added to the bottom of the kelly section when advancing the hole. The entire length of drill pipe is torqued to turn the drill bit at the bottom of the hole. The kelly is a piece of nonround cross-section drill pipe that is turned using a motor connected to a similarly shaped bushing fixed to a rotating table at the drill rig floor. Historically, drill rigs applied the torque to the drill bit through the drill pipe by an uppermost “kelly” section. A recent overview of advances in drilling is Li et al. We broadly group relevant deep drilling methods by how drilling torque is applied to the drill bit, how directional control is maintained, and the type of drill bit. While deep borehole disposal is currently being investigated in vertical boreholes, the same directional-drilling technology can be used to maintain borehole straightness (i.e., dogleg-severity or maximum angular deviation across a specified distance) and verticality (i.e., borehole plumbness), even when the rock structure, fabric, or fractures would tend to cause the drill bit to deviate from vertical. The advances have been primarily associated with directional control, which is related to the boom in oil and gas drilling associated with horizontal wells. MacKinnon, in Geological Repository Systems for Safe Disposal of Spent Nuclear Fuels and Radioactive Waste (Second Edition), 2017 4.4 Drillingĭrilling technology has matured significantly since the Woodward–Clyde deep borehole design study in 1983. ![]()
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