US 2761651 A
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2 Sheets-Sheet 1 l 7 5 m ik M W., Sept. 4, 1956 1 w. LEDGERWOOD, .1R g APPARATUS FOR CYCLIC PELLET IMPACT DRILLING Filed March e, 1952 Sept. 4, 1956 l.. w. LEDGERwooD, 1R 2,761,651
APPARATUS FOR cYcLrc PELLET IMPACT DRILLING Filed March 6, 1952 2 Sheets-Sheet 2 United States Patent O APPARATUS FOR CYCLIC PELLET IMPACT DRILLING Leroy W. Ledgerwood, Jr., Tulsa, Okla., assigner to Esso Research and Engineering Company, a corporation of Delaware Application March 6, 1952, Serial No. 275,171
4 Claims. (Cl. 255-61) This invention concerns a novel technique of drilling bore holes in the earth. The invention embodies the basic principles of drilling employed in the so-called `pellet impact drilling method. Thus, a stream of high velocity directed pellets is employed to pulverize the earth so as to drill or cut a bore hole. In accordance with this invention, means and apparatus are disclosed for maintaining the drill ejecting the pellets at a desired spaced distance from the bottom of `the borehole. The invention employs the concept of using a cyclic drilling operation in accordance with which the drill is normally maintained at a spaced distance from the bottom of the bore hole. Periodically, however, the drill is lowered to the bottom and is then retracted a set distance from the bottom to permit periodically feeling for and readjusting the displacement of the drill from the bottom of thc bore hole.
The basic principles of pellet impact drilling are fundamentally simple. Means are simply required to provide a jet of high velocity fluid including provision for entraining and accelera-ting pellets in this jet of fluid. The basic principles of the technique of drilling by pellet impact are set forth in co-pending applications, Ser. No. 268,873 of Philip S. Williams, entitled Pellet Impact Drilling Method and Apparatus, and Ser. No. 268,882 of Leroy W. Ledgerwood, Jr., entitled Momentum Pellet Impact Drilling Apparatus, both applications iiled on January 29, 1952.
Basically the pellet impact technique for drilling bore holes in the earth involves the use of a stream of fluid pumped from the surface of the earth through a tubular member to a jet nozzle assembly adjacent the bottom of the bore hole. The jet nozzle assembly is adapted to direct a high velocity jet of uid against the formation being drilled and is provided with means for entraining in the jetted fluid a multitude of pellets which are accelerated to high velocity in the jet stream and thereby acquire considerable kinetic energy so that when the pellets impinge against the formation the resulting percussive and fracturing forces exert a drilling action. Preferably the pellets that are employed are smooth, non-abrasive and esentially sperical and are of substantial size, preferably in the size range of about l to about l in diameter. lt is preferred that hard, tough metallic alloys be employed as the pellet material.
It is generally desirable in obtaining a suitable ejection of pellets to employ a nozzle assembly utilizing a primary and secondary jet nozzle. The primary nozzle is employed to convert uid pumping pressure to velocity energy. Consequently, fluid pumped through the primary nozzle is subjected to a substantial pressure drop, of 100 pounds per square inch or more, to provide a constricted directed high velocity jet of fluid. A secondary nozzle is positioned immediately below and concentric with the primary nozzle. The secondary nozzle should have a substantially greater diameter than the primary nozzle to accommodate the total volume of uid from the primary nozzle in addition to the volume of pellets there entrained. This configuration and arrangement of nozzles, by its nature, creates an aspirating eifect which plays a part in the recirculation of the pellets.
By the nature of pellet impact drilling of the character described, it is necessary that the jet nozzle assembly used for ejecting the pellets be maintained above the bottom of the bore hole. It is generally undesirable to have any portion of lthe drill extending below the nozzle assembly as circulation of the pellets would cause rapid wear of this portion of the drill. Thus it is generally undesirable to employ mechanical standoff arrangements to position the jet nozzle assembly at the desired distance above the bottom of the bore hole. It is the principal object of this invention to provide a method and apparatus for spacing the drill from the bottom of the bore hole without necessitating constant contact of any portion of the drill with the bottom of the bore hole.
The method by which this is achieved depends upon periodically lowering the drill so as to contact the bottom of bore hole. By then retracting the drill a selected amount, normal drilling can be conducted at the optimum displacement of the drill from bottom. The cyclic operation of bringing the drill in contact with bottom need only infrequently be conducted so that a small portion of the drilling time is required for this positioning operation. Apparatus embodying this method may best be constructed so as to maintain the drill itself in sliding relation with the lower termination of the drill string.
This sleeve arrangement may be provided with accessory means to automatically and periodically cause the sleeve supported drill to contact bottom and to retract from the bottom so as to maintain the desired displacement of the drill.
A preferred embodiment of the invention is illustrated in the accompanying drawings in which:
Figure 1 illustrates in cross-sectional elevational detail the drill of this invention in drilling position;
Figure 2 is a cross-sectional view of Figure l along the line II-II;
Figure 3 is a cross-sectional view of the drill of Figure 1 along the line III-III of Figure 1;
Figure 4 is a cross-sectional view of the drill of Figure l along the line of IV-IV; and nally Figure 5 is an enlarged detail cross-sectional drawing of the trigger valve arrangement employed to cause automatic cycling operation of the drill assembly of Figure 1.
Referring to these drawings, it will be seen that the entire drill is supported by a tubular member which may constitute a drill string identified by numeral 1. The drill itself constitutes a primary nozzle 3 and a secondary nozzle 9 of the character hereinbefore identified. The primary nozzle 3 may be fixed to and constitute the lower termination of a sleeve element 2 which is maintained in sliding relation with the lower termination of the drill string 1. The secondary nozzle 9 is supported below and coaxial to the primary nozzle 3 by means of the support elements 25 which may be fixed to either the sleeve 2 or the primary nozzle 3.
A cylinder 17 is xed to the drill string 1 immediately above the uppermost position of sleeve 2. This cylinder extends downwardly along drill string 1 about sleeve element 2. The lower portion of the cylinder is maintained in fluid-tight sliding relation with sleeve member 2 by the provision of packing 26. A piston 4 is provided on the upper termination of sleeve 2 within the cylinder member 17. A fluid passage extends from the interior of the drill string 1 through the wall of the cylinder to the interior of the cylinder near the bottom thereof. This passage is identified by number 6, and preferably terminates in an orice opening 7. If desired, a number of such passages may be provided.
In addition to these elements, an elongated slot 13 is provided in the wall of the tubular support member 1 at the portion of the drill string over which sleeve 2 may slide. One or more ports 14 are cut through sleeve element 2 which are normally not in register with slot 13 and may normally be somewhat above the upper termination of slot 13. Finally, one or more ports 27 are cut through an upper portion of the cylinder 17.
From this brief identification of the principal elements of the drill illustrated, the operation of this apparatus may be understood. In the course of the description of the operation reference will be made to the remaining features of construction not heretofore described.
The drill is normally maintained in the condition and position illustrated in Figure l. Drilling fluid is pumped through the drill string 1 to be ejected from primary nozzle 3 and to pass downwardly through secondary nozzle 9. Pellets are entrained in the secondary nozzle and are accelerated and directed downwardly through the secondary nozzle so as to impinge against the bottom of the bore hole. These pellets rebounding from the bottom of the bore hole are carried outwardly and upwardly in the ow of drilling fluid in an annular channel between the bore hole and the external portion of secondary nozzle 9. Immediately above the secondary nozzle 9 an enlarged annular space is provided causing the fluid to have a substantially reduced vertical velocity. Consequently, immediately above the secondary nozzle 9 pellets may settle from uptlowing drilling fluid so as to drop downwardly into the interior of the secondary nozzle for recirculation as described. This recirculation of the pellets is facilitated by aspiration forces created by this nozzle arrangement. Drilling fluid will pass upwardly to the surface of the earth for recirculation through the interior of the drill string.
The propulsion of drilling uid through nozzle 3 and nozzle 9 will maintain a net downward force on these elements. This force, in addition to the weight of nozzle 9 and the slidable elements supporting it, will create a normal tendency for extension of the sleeve arrangement provided so as to normally urge the nozzle arrangement downwardly against the bottom of the bore hole. This downward force is counteracted and overcome by an upward force provided by the cylinder and piston arrangement employed.
Thus drilling lluid under the pumping pressure employed is at all times forced from the interior of the drill string through channel 6 and orifice 7 into the cylinder so as to act upwardly against piston 4. This upward force is proportioned by design considerations so as to normally overcome the downward forces on the nozzle arrangement so as to maintain sleeve 2 in the upward position illustrated. ln the practical construction of this apparatus, the area of piston 4 may be chosen so that when the pressure in the annular chamber 5 within the cylinder is at least about 1/2 the pressure in the drill string, sufficient upward force will be exerted by the piston arrangement to balance the net downward force on the nozzle assembly. As a result circulation of drilling uid through passage 6 to the interior of the cylinder will normally maintain sleeve 2 in its uppermost drilling position as shown.
To permit the desired cyclic operation causing lowering of the nozzle assembly to the bottom of the bore hole a trigger arrangement is employed. This trigger arrangement serves to rapidly and sharply reduce the pressure within the annular space 5 of the cylinder so as to permit piston 4, sleeve 2 and the associated elements to drop downwardly. For this purpose it is necessary to provide a pressure release mechanism in cylinder 5 which will operate to reduce the pressure therein at periodic intervals. One means by which this may be accomplished is illustrated in Figure l and is particularly shown in Figure 5. The method employed depends upon the gradual build-up of pressure within the annular space 5 permitted by the restricted orifice 7. Orifice 7 permits only a limited amount of uid to pass from the drill string into the cylinder, so that a time period of live minutes for example, may be required for the pressure to build up within the annular space 5 to the pressure of the fluid within the drill string. The pressure release mechanism is arranged to permit opening of a valve 8 when this pressure has built up to substantially the pressure within the drill string. The pressure release mechanism operates independently of the relative position of piston 4 within the cylinder 17.
The rapid release of pressure within the annular space 5 occurs through a valve opening 28 which may be cut in piston 4. This valve opening is normally closed by valve member 8 which sets on port 28. A valve stem 10 xed to the valve member 8 extends downwardly in conjunction with a detent arrangement adapted to normally hold valve 8 in closed position. As illustrated in Figure 5 the detent may constitute a recess cut into stem 10 which receives a ball 11 urged into detent position by spring 29. A second spring element 12 is maintained in compression above valve member 8 acting to apply a force to maintain valve member 8 in sealed position. This arrangement is constructed so that substantially greater upward force is required on valve 8 to unseat the ball detent 11, than to` compress spring 12. Thus, once fluid pressure builds up within chamber 5 to the pressure of uid in the drill string, suflicient force will be exerted on valve 8 to unseat the detent arrangement, and to permit opening of the valve. As spring 12 is relatively weak, the valve will stay open as long as Huid flows through the valve. This uid ow will continue until pressure within annular chamber 5 is equal to pressure in the annular space between the bore hole and the drill string; equalization occurring through port 27. When fluid flow stops, then spring 12 is able to force valve 8 back on its seat permitting re-engagement of the detent 11, and preventing the valve from opening again until a very high fluid pressure is reached below valve 8.
This arrangement therefore serves to provide the desired triggering of the sleeve arrangement. Normally, uid will pass through channel 6 and orifice 7 to apply pressure within annular chamber 5 so as to maintain the piston in the uppermost position. The piston will remain in the uppermost position during the time period required for fluid to leak through orice 7 to raise the pressure within annulus 5, to the pressure within the drill string. When this happens, valve 8 is triggered to cause rapid release of pressure and to permit the nozzle assembly to drop downwardly to contact the bottom of the bore hole. Preferably, particular provisions are made to secure the rapid retraction of the drill bit from thc lowermost position to the position illustrated in the drawing. This depends upon utilization of slot 13 and port 14 already identified. When the drill nozzle assembly has contacted the bottom of the borehole, contact with the bottom will prevent rotation of the nozzles and the sleeve element 2. Continued slow rotation of drill string 1 from the surface of the earth will therefore cause drill string 1 to rotate within sleeve 2. This rotation will bring port 14 of sleeve 2 in register with slot 13 of the drill string. When this happens a uid passage is opened from the interior of the drill string to the annular chamber 5 so as to cause a rapid increase of pressure within chamber 5 forcing piston 4 upwardly to lift the drill bit off the bottom. This upward movement will be rapid because of the large size ports employed. Upward movement of the bit will continue until pin 15 which is fixed in drill string 1 is engaged by the upward moving cam 16 which is rigidly xed to the upper surface of piston 4. Contact of the pin 15 with the cam 16 will force rotational movement of sleeve 2 with respect to the tubular support or drill string 1. This rotational movement will force slot 13 and port 14 out of register. The elements described are so arranged that this occurs when the lower termination of drill string 1 seats on shoulder 18 provided adjacent the primary nozzle 3. Thereafter the cyclic operation continues with the gradual build-up of pressure due to fluid passage through channel 6 and orifice 7.
It is apparent that the different operational steps conducted on a cyclic basis may be adjusted as desired by design of the elements employed. Thus it is practical to maintain the bit in a stationary position off bottom for about five-sixths of the total time cycle, while moving downwardly to contact bottom and to be retracted there from for the other one-sixth of the time. Division of time between these operations may be adjusted by choice of orifice and port sizes and their relative positions.
It is a particular feature of the apparatus illustrated that one or more ports 19 cut through sleeve 2 are positioned to provide hydraulic information as to the distance of the drill bit from the bottom of the bore hole. Thus, when sleeve 2 and the nozzle assembly is permitted to drop downwardly, port 19 may be at a position below the lower termination of drill string 1, if the drill bit was originally at an undesired distance above the bottom of the bore hole. If port 19 does drop beyond this point, there will be a release of pressure within the drill string by the passage of fluid through port 19 which will inform an operator at the surface of the earth that this limiting position has been reached. This provides a convenient indication that it is necessary to lower drill string 1 a short distance to maintain the desired positioning of the drill bit.
In using this apparatus it is generally preferred that the drill string be continuously lowered at a rate somewhat less than the normal drilling rate of the apparatus. Progression of the drilling at a rate faster than that at which the drill string is lowered will eventually result in the pressure drop referred to through port 19 when the drill is in the bottom contacting position. When this happens an operator will then lower the entire drill string a limited amount and will then resume the continuous lowering at the rate referred to. Alternatively, if desired, the drill string can be maintained stationary except when port 19 operates to permit release of pressure. When this occurs the drill string will simply be lowered an incremental amount and drilling continued until port 19 is again opened by the cyclic operation.
It should be observed that all elements of the apparatrs described operate on the basis of pressure differentials existing in the different portions of the apparatus and the bore hole. None of the elements described depends upon absolute pressures and consequently changes in static pressure within the bore hole, even though at great depth, will not affect the operation of the apparatus.
It is apparent that arrangements other than those disclosed may be employed to secure the cyclic drilling referred to.
What is claimed is:
1. A drilling apparatus comprising in combination a tubular support member and a sleeve member maintained in vertical telescopic sliding relationship, a nozzle element supported on the lower termination of said sleeve, a cylinder fixed to one of said members, a piston fixed to the other of said members and positioned within said cylinder, a uid passage extending from the inner bore of one of said members to within the portion of said cylinder that will exert a lifting force on said sleeve when fluid pressure is built up within said cylinder, and a pressure release mechanism operative to release pressure within said cylinder sharply when a predetermined pressure has been built up within said cylinder, whereby when fluid pressure exists within said tubular support and sleeve members, pressure will periodically build up within said cylinder and will periodically be released by said valve, thus imparting a vertical reciprocating motion to said sleeve, said pressure release mechanism comprising a valve member having a valve passage and a valve closure element, a first spring element urging said valve closure element to seal in said valve passage, a detent member acting to retain said valve closure member in sealed position, and a second spring element urging said detent member against the valve closure member.
2. A drilling apparatus comprising in combination a tubular member and a sleeve member maintained in vertical telescopic sliding relationship, a jet nozzle assembly supported by said sleeve below said tubular member, an annular cylinder fixed to one of said members and encircling the other member in fluid-tight sliding relationship, an annular piston fixed to the other of said members in fluid-tight sliding relationship with the inner wall of said annular cylinder, a uid passage extending from the inner bore of one of said members to within the portion of said cylinder that will exert a lifting force on said sleeve when fluid pressure is built up within said cylinder, and a pressure release mechanism operative to release fluid pressures within said cylinder rapidly when a predetermined pressure has been built up within. said cylinder, whereby when fluid pressure exists within said tubular support and sleeve members pressure will periodically build up within said cylinder and will periodically be released by said valve, thus imparting a vertical reciprocating motion to said sleeve, said pressure release mechanism comprising a valve member having a valve passage an-d a valve closure element, a first spring element urging said valve closure element t-o seal in said valve passage, a detent member acting to retain said valve closure member in sealed position, and a second spring element urging said detent member against the valve closure member.
3. The apparatus defined by claim l including a vertical slot in said support member and at least one perforation in said sleeve member adapted to register with said slot on relative rotation of said sleeve and support members.
4. The apparatus defined by claim 3 including a cooperat-ing cam element and cam follower fixed` to. said sleeve member and said support member urging rotation of said sleeve relative to said support member when said sleeve member is forced upwardly with respect to said support member.
References Cited in the file of this patent UNITED STATES PATENTS 1,502,851 Gale July 29, 1924 1,659,826 Malloy et al. Feb. 21, 1928 1,669,130 Jensen May 8, 1928 1,927,836 Kightlinger Sept. 26, 1933 2,233,260 Hawthorne Feb. 25, 1941 2,422,031 Merten June 10, 1947 2,448,459 Palm Aug. 31, 1948