The roller cone bit breaks rock by crushing and shearing. The cone is rolling at the bottom of the well, so the requirement for the torque is small, which can greatly reduce the mechanical load.
When the drill bit is working, the roller cone not only rotates around the axis of the drill string but also rotates around its own axis.
According to the number of roller cones, roller cone bits can be divided into single roller cones, double roller cones, three roller cones, four roller cones and multiple roller cones. According to the method of breaking rock, it can be divided into full-scale drilling cone bit and coring cone bit. According to the nature of the work, it can be divided into forward pilot hole drilling positive circulation roller cone bit, a pilot hole drilling reverse circulation roller cone bit, center continuous sampling cone roller bit, positive circulation reaming roller cone bit, and reverse circulation reaming roller cone bit. According to the teeth and structure of roller cones, it can be divided into steel teeth and embedded roller cone bits. When using it, it is necessary to choose the adaptation range of its tooth shape according to the local conditions.
The roller cone bit is used for drilling and has a wide range of applications, and it can be applied from soft formations to hard bedrock formations.
In contracted water well drilling projects, the adoption of roller cone drilling accounts for more than 80%, especially in the deepwater wells and the geothermal well construction. A small number of traditional fishtail drill holes, three-blade drill bit reaming, and hard alloy steel core drilling, which is not only laborious but also lavish, causing great waste to the construction and increasing the burden. Now, there is no choice but to seek for the innovation and upgrade of the roller cone drilling.
Safety accidents occur frequently in coal production. CBM wells are generally drilled with roller cone bits in the first opening, and pneumatically by DTH hammers in the second opening. Due to the large diameter of the gas discharge well and there are certain requirements about the verticality of the hole. Therefore, the three roller bits are generally used to drill the front pilot holes, and then the roller cone drills are expanded to form the well.
In the construction of trenchless crossing project, in addition to using winged carbide back-expanding drill bits in loose formations, some bedrock formations also need to use roller cone welding back-expanding drill bits to complete the task. It mainly uses roller cone reamer and PDC reamer.
In the construction of building and bridge foundation engineering, rock-socket piles with large diameter and high bearing capacity are often required. The previous method is to use cemented carbide and steel grain drilling, but now, the traditional drilling process has been replaced by the roller cone drilling process, which is of simple operation and strong adaptability. It can realize non-circulation drilling, mud forward circulation drilling, reverse circulation drilling and bottom expansion pile drilling. The main tool is a barrel drill. If it are co-used with a replaceable tooth palm piece, the rock will be broken evenly, with high efficiency, low cost, and the quality of the drilled hole will be better.