Development trends in the upgrading of modern large-scale oil drilling rigs

Thread Content

　　As oil exploration involves drilling in deeper seas and further underground, and with the development of new drilling techniques, there is a trend to use horizontal wells, directional wells, and ultra-deep wells to locate oil and gas. As a result, oil drilling rigs must go beyond traditional design patterns in order to meet the requirements of various drilling operations. Oil rig winches need to meet high power requirements. As the lifting load increases, it generally rises to 2,940–5,145 kW, with the lifting load approaching 10,000 kN. This places higher demands on the winches of oil drilling rigs. 1 Transmission of the winch: In the past, it was equipped with up to 3 GE752 type DC motors for driving; now, 4 high-torque GE752 type DC motors are to be installed. However, the sleeve roller chains of the transmission elements consist of up to 10 rows of chains; to transmit greater power, such multi-row chains are unable to handle it. As a result, gearboxes with high power and high precision have gradually come to be used in high-power winches. The use of a gear transmission box not only helps to reduce the size of the winch’s transmission mechanism, satisfying the layout requirements of the entire drilling rig, but it also facilitates the use of automatic drill feeding and energy-consuming braking, thereby advancing drilling technology toward mechatronics. 2 Electric motors: Originally, the most advanced drive system used was one that relied on direct current to power drills, and this was applied in both land-based and deep-sea drilling rigs. Due to the development of deep-sea oil and gas wells as well as medium and deep drilling for onshore oil and gas, these DC-driven drilling rigs have also gradually shown their shortcomings. Because the structure of DC motors cannot meet the requirement of producing no sparks. Especially in the drilling of high-pressure gas wells, this represents a fatal drawback for DC motors. With the development of variable-frequency technology, large offshore platforms and deep-well land drilling rigs now use AC variable-frequency motors; as a result, no sparks are generated, eliminating the risk of fires. Furthermore, permanent magnet motors have been introduced into the conventional design of AC variable-frequency motors; these motors have a power factor close to 1, are suitable for high-power, high-speed operation, and their size is 1/2 to 1/3 of that of conventional motors. They are particularly the preferred choice for users in top-drive drilling applications. 3 Auxiliary brakes: Not only have hydraulic brakes been phased out, but electromagnetic eddy-current brakes are also gradually disappearing from the market. The most modern types of brakes are water-cooled or pneumatic disc brakes, as well as auxiliary hydraulic disc brakes; these allow the drilling tools to be stopped in emergency situations. By eliminating the need for separate brake systems, the design becomes simpler, and the corresponding dimensions are reduced. 4 Changes in mud pumps: Firstly, to meet the requirements of horizontal wells and long-distance drilling, it is necessary for mud pumps to increase their pumping pressure and flow rate, as well as their power output. At present, the maximum power of a single mud pump is 1,617 kW, with a pressure exceeding 35 MPa. This is to meet the needs of deep-sea exploration and ultra-deep wells on land. Moreover, the number of pumps required per drilling rig has increased from 2 to 3, with the aim of ensuring that two pumps are always in operation, thereby preventing horizontal drilling tools from getting stuck at the bottom of the well. Additionally, from a structural perspective, mud pumps are required to have small external dimensions in order to meet the space constraints of offshore platforms.