Views: 60 Author: Site Editor Publish Time: 2022-07-25 Origin: Site
Under the condition of the wheel trencher bit, the combined drive of the surface and downhole motors can significantly improve the ROP of the wheel trencher bit, but the life of the drill bit will also be significantly shorter. So what is the rock breaking mechanism of the wheel trencher bit? Let's take a look at it next.
Here is the content list:
l The cutting principle of "milling instead of drilling"
l The characteristics of tooth invasion and the state of non-parallel scraping
l Unbalanced contact state of the wheel trencher bit
In the conventional drilling process, the process of the wheel trencher bit cutting the bottom hole rock is the same as the drilling principle of the twist drill bit in machining, and all the cutting teeth (except the backup teeth) are involved in the rotary cutting at the same time. However, in the wheel trencher bit, some teeth on the drill bit periodically participate in intermittent cutting (even if the cutting of the teeth is not interrupted, at least its cutting state will change periodically), and the cutting thickness is variable. This is no longer "drilling", but rather a characteristic of the "milling" process. The drilling process of the drill bit can be regarded as completed by the method of "milling instead of drilling". The rotation of the wheel trencher bit driven by the bending motor is the main motion of "milling", and the revolution of the drill pipe becomes the feeding motion.
In this special "milling instead of drilling" method, the working state of the drill cutting teeth shows a certain degree of alternation, rather than continuous scraping under ideal drilling conditions; the cutting motion trajectory is also determined by the ideal drilling method. The concentric circle track below becomes a spiral motion track. Observing and analyzing the interaction process of the drill bit and the bottom hole rock from the perspective of "milling" will help us to understand the complex motion and cutting mechanical characteristics of the Chain trencher bit and its cutting teeth in-depth and in detail.
From the observation of the bottom hole morphology of the wheel trencher bit, it is known that there are two main characteristics of the wheel trencher bit cutting rock: the interaction between the cutting teeth and the rock is a cutting process of non-parallel scraping; Rough "scratch marks" form on the bottom of the well, allowing the cutters to naturally penetrate the rock.
Due to the existence of the flexible angle θt of the curved screw, the center of the drill bit deviates from the center of the wellbore, and one side of the drill bit has a large penetration depth, while the other side has a small penetration depth. At the same time, the PDC cutters are not all involved in scraping and cutting rock. Therefore, the drill bit will form uneven and intersecting "scratch marks" at the bottom of the hole, which will help reduce the confining pressure compaction effect in the micro-convex area of the bottom-hole rock and reduce the local crushing strength of the rock. At the same time, the natural bulge of the rock is conducive to improving the ability of the cutting teeth to eat into the rock, and it is easier to cause the large-grained cuttings to peel off from the bottom of the well in the rock bulge, thereby improving the rock-breaking efficiency of the Chain trencher bit.
Due to the existence of the screw angle, some of the cutting teeth on the Chain trencher bit (the cutting teeth that rotate to the high end) are out of contact with the rock for a short period. In this way, the average number of effective teeth that the wheel trencher bit participates in cutting will be Less than the total number of teeth in the drill.
The above is the relevant content about the rock breaking mechanism of wheel trencher bit, if you are interested in Auger bits, Chain trencher bit, cup cutter teeth for vemeer, you can contact us, our website is www.cuttingpicks.com.
