HYDRAULIC DEFLECTOR FOR DIRECTIONAL DRILLING OF GEOLOGICAL EXPLORATION WELLS

V. M. MATROSOV

(Presented by the scientific seminar of the departments of exploration engineering, safety engineering, and mining production technology)

The drilling of geological exploration wells along a strictly prescribed trajectory is one of the most important problems of drilling; the further growth of the qualitative and quantitative indicators of drilling operations depends to a large extent on its successful solution. The technical means and methods of directional drilling presently available make it possible, in a number of cases, to solve more or less successfully the problem of sinking wells in a prescribed direction. At the same time, they are not free of certain shortcomings, as a result of which the range of their application is limited by a whole series of conditions. Thus, for example, some of the known designs require that the drilling process be stopped (various types of wedges, the SVS2-B design of Yu. L. Boyarko, the MGRI device of A. G. Kalinin’s design, etc.); others deflect the well only in the zenith plane (hinged deflectors). The designs of assemblies for spatial curvature of wells are often complex in arrangement (INB-ShM, the FTL VKGU design), require special anchoring devices (SNB-3) or complicated orientation, and are unreliable in operation.

The hydraulic deflector arrangement developed by the author is free of the indicated shortcomings and can be used for directional drilling of geological exploration wells along a prescribed trajectory. In this case, the given deflector makes it possible to change the direction of the well both in the zenith and in the azimuthal planes without stopping the drilling process.

In Fig. 1 the hydraulic deflector is shown in section. It is installed between adapter 2 to core barrel 1 and hinged adapter 11, connected with the drill-pipe string. The deflector itself consists of the following main parts: perforated branch pipe 7, distributing adapter 6, unbalance body 5, consisting of two parts—upper and lower—and cover 10. The lower part of the unbalance body rests on the shoulder of the perforated branch pipe through radial-thrust ball bearing 4. The upper part of the body rotates on radial ball bearing 9. The bearings are protected by gland seals 3. The upper and lower parts of the unbalance body are connected by means of a thread with the distributing adapter. Inside the body, eccentrics 8 (eccentrically arranged weights) are fastened by means of screws. The distributing adapter has two transverse holes, in which pistons 14 are placed. The pistons are connected through rods 17 with rocker arm 18, which has stop 19 at its end. The pist—

…they are held in the extreme position by springs 15, which bear against the compression nuts 16. The adapter-distributor has two inlet openings 12 and two outlet openings 13.

The operating principle of the hydraulic deflector is as follows.

After the drilling assembly together with the deflector has been lowered to the bottom of the inclined borehole, the body of the debalance, freely rotating

Fig. 1. Hydraulic deflector: 1 — drill pipe; 2 — adapter; 3 — packing seal; 4 — radial-thrust ball bearing; 5 — debalance body; 6 — adapter-distributor; 7 — perforated branch pipe; 8 — eccentric; 9 — radial ball bearing; 10 — cover; 11 — ball adapter; 12 — inlet opening; 13 — outlet opening; 14 — piston; 15 — spring; 16 — compression nut; 17 — rod; 18 — rocker arm; 19 — stop

in the bearings, will assume such a stable position that the eccentric load is located in the extreme lower position (on the low side …)

wall of the borehole). A pump is switched on at the surface, and the drilling fluid, after passing through the drill pipes, enters the debalancing body from the upper openings of the perforated sub. Then, entering the inlet openings of the adapter-distributor, the drilling fluid transmits pressure to the pistons, which, compressing the springs, extend the rocker arm with the thrust pad. After the pistons open the outlet openings, the drilling fluid from the lower part of the debalancing body enters the perforated sub and proceeds through the core barrel to the bottom of the borehole. The thrust pad of the rocker arm, pushing the upper part of the core-barrel assembly away from the borehole wall, thereby creates a skewing of the latter relative to the borehole axis.

If the eccentrics are positioned relative to the rocker arm as shown in Fig. 1, the hydraulic deflector will “straighten” the borehole, i.e., reduce its zenith angle. In the case when it is necessary to “lay out” the borehole (increase the zenith angle), the eccentrics must be displaced by 180° relative to the rocker arm. When the eccentrics are displaced by 90° clockwise or counterclockwise, the borehole being drilled will be deflected respectively to the right or to the left in azimuth. An intermediate displacement of the eccentrics will cause a simultaneous change in both the zenith and azimuth angles of the borehole.

The hydraulic deflector can be used directly in the process of drilling a borehole if its zenith angle is not less than 5°. It is most expedient to use it when drilling with hard-alloy bits and diamonds, both by the core method and with a full-face bottom, in rocks of drillability categories V–XII. This deflector is less effective when drilling by the shot method, since in that case it is necessary to regulate precisely the supply of drilling fluid to the bottom of the borehole.

The force with which the upper end of the core-barrel assembly is pushed away by the rocker arm will depend on the piston area and on the pressure drop in the adapter-distributor. For example, with a piston diameter of 2 cm and a pressure drop of 20 atm, this force will be 125 kg.

The weight of the eccentrics must be greater the smaller the zenith angle of the borehole. At the same time, the moment of the eccentrics must in all cases exceed the moment of resistance in the bearings and seals. The core-barrel assembly should be of small length (1.0–1.5 m) in order to create a sufficient skew angle in the borehole. However, so as not to reduce the technical rate of drilling, its length must not limit the run footage.