The technical-economic indices of deep-well drilling in hard, strong, and very strong rocks are improved by the use of drill-rig shock absorbers (henceforth referred to simply as shock absorbers). These devices reduce the vibrations of the drill rig, which in turn reduces the incidence of fractures of the heavily loaded drill pipes and the threaded couplings, lengthens the time between repairs of the bottom-hole engines, and makes it possible to optimize the service conditions of the bits. The use of such shock absorbers has a particularly significant effect on the technical-economic indices of drilling. The most important characteristics of any shock absorber are its durability and performance inside the well and the efficiency of its use. The reliability and service life of a shock absorber with shell-type elastic elements are determined by the durability of the parts of its housing, since the reliability and service life of the elastic element and the other parts are considerably greater. This circumstance is related to the operating conditions of the shock absorber: �9 the geometric dimensions of well are limited, which makes it impossible to maintain the necessary gap between the shock-absorber housing and the wall of the well, assuming that the shock absorber itself is of the necessary strength; �9 poor cleaning of the bottom of wells leads to the accumulation of abrasive sludge in the bottom region and along the well: �9 the shaft of wells is curved, and constrictions and projections are formed; �9 wells contain metallic and hard-alloy fragments of the teeth of the bits, as well as entire teeth tom from the cutter during drilling. All this creates very difficult conditions for the operation of the housing parts of shock absorbers [1, 2]. Thus, special protection must be provided to ensure their reliability, durability, and efficiency during the drilling of wells. In shock absorber installed on the shafts of motors, it is best to combine the housing of the shock absorber with the housing of the radial-thrust bearing of the turbodrill, electric drill, or screw motor (or the so-called spindle). This prevents vibration of the housing and its parts in an abrasive medium [3]. During rotary drilling, it is impossible to keep the shock absorber from also rotating. In this case, it is necessary to resort to technological and design solutions to protect the parts of the shock-absorber housing. Figure la shows a shock absorber with straight ribs equipped with hard-alloy inserts (teeth) or a wear-resistant hard facing [4]. It can be seen that the ribs are secured to a thick-walled adapter and a bushing, and the ends of the ribs overlap the thrust ends of the conical threads. Those threads are the most vulnerable and most dangerous parts from the viewpoint of the strength of the shock absorber. If the strength of the housing is increased (with its wall being at least 17.5 mm thick), the ribs can be attached directly to the housing (see Fig. lb). The ribs of the shock absorber can be made in helical form [5]. This reduces the number of ribs located about the perimeter.
Read full abstract
Sep 30, 2017
V Biletskyi + 2
Open Access
