US 2746721 A
Description (OCR text may contain errors)
APPARATUS FOR DRILLING Thomas V; Moore, Manhasset, N. Y., assignor to Esso Research and Engineering Company, a corporation of Delaware I Application October 1, 1951, Serial No. 249,113
1 Claim. (Cl. 255-24) The present invention relates to an apparatus for drilling well bore holes. In accordance with the present invention an increased drilling speed is obtained with the aid of jets in which a valve is positioned at the bottom of the drill pipe which opens when a predetermined high pressure is imposed upon it. The valve remains open until the pressure falls to a predetermined value. By operating in this manner the energy intermittently stored in the drill pipe is effectively released in a pulsing mud jet of very high reaction.
In the exploration for oil the art of drilling well bore holes into subterranean areas of the earth has been widely investigated and extensively developed. The techniques employed are many and a wide variety of drilling bits and associated apparatus have also been developed. One conventional procedure is to attach a suitable bit on the end of a pipe string and to rotate the bit by the rotation of the pipe string.
Thus, at the present time, the majority of drilling operations are conducted by employing rotary drilling equipment. In conventional rotary drilling, a hollow jointed steel shaft called the drill stem is rotated from the surface of the earth. This shaft, extending downwardly into the earth to any desired depth, rotates a drill bit. For a number of purposes, a weighted fluid called drilling mud is circulated in one direction through the drill stem and in the opposite direction through the annulus between the drill stern and the bore hole.
In drilling operations of this character, it is also known to employ relatively high velocity jets. The jetting action is secured by imposing a pressure on the drilling fluid within the drill stern by means of surface equipment. This fluid is jetted through suitable fluid jet passageways in the bit in order to aid the drilling operation. This type of jet drilling technique is particularly suitable for securing satisfactory drilling rates when piercing ditficult rock formations. However, in the conventional jet drilling operation of the character disclosed, the efliciency of the system depends upon the reaction of the jets of mud flowing through the water courses. The reaction of the jets is limited due to frictional loss of energy such as the friction of the mud flowing through the long string of drill pipe to the bit. This frictional loss consumes a large part of the energy of the mud stream which otherwise could be used in the jetting action. In accordance with the present invention, a valve is utilized which is disposed at the lower end or bottom of the drill pipe. This valve will open when a predetermined pressure is reached within the drill pipe at which time it will open and will remain open until the pressure has dropped to a predetermined point, thus producing an effective pulsing motion of the jets.
The present invention may be readily understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing, a drill stem 1 is shown disposed in well bore hole 2, which extends from the surface through subterranean formations 'ice 2 3. Attached to the lower end of drill stem 1 is a fishtail bit 4 containing fluid passageways 6. In normal operation, a drilling fluid is pumped down within the drill stem.
This fluid flows through ports 6 either in the bit itself or through other ports into the annular .area between the bore hole Wall and the outer surface ofvthe drill stemQ In accordance with the present invention, this fluid passes through fluid passageway 6 and is jetted at a high velocity in order to increase the drilling rate. In accordance with the present invention, a suitable piston valve 9 which seats at .the topof conduit 15 or its equivalent is disposed in thelower end of the drill stem. The valve assembly is positioned'within the drill stem by a suitable structural means 12 containing ports 14 so as to permit the passage of downflowing fluid. This valve remains closed until a predetermined high pressure is imposed upon it. The valve opens and remains open until the pressure falls to a predetermined value. Thus, there is secured an intermittent, high velocity pulse jet action through the jets 6 which is secured by utilizing the stored energy of the mud stream within the drill stem.
Any suitable type of valve may be employed, as for example a pintle type valve. The valve preferably operates against the action of a spring means 16. Thus, for example, as the pressure builds up on the fluid head within the drill stem, pressure is exerted against the face of the valve as illustrated by arrows 7. This pressure is exerted against the downward thrust of a spring means 8 positioned in cylinder 10. As the pressure reaches a predetermined high value, the face of the valve 9 moves off valve seat 11 at which time the area of the valve face exposed to the thrust of the mud increases abruptly due to the design of the valve, thus, materially and rapidly increasing the total force on the face of the valve. The effect of this is to have the valve in effect snap open rapidly. The entire valve mechanism 9 comprising a piston element, moves upwardly in cylinder element 10 against the force of spring element 8.
As the mud pressure is released after a certain quantity of fluid is jetted through ports 6, the valve starts to close and then snaps back rapidly for the reasons given heretofore. The entire valve assembly is rigidly positioned in the bottom of drill stem 1 by suitable brace elements 12, which brace elements permit the mud fluid to flow freely past the same. In order to permit satisfactory operation of the valve mechanism and to equalize the effect of the fluid head of mud in the area between the drill stem and the bore hole with that of the fluid head of the mud within the drill stem, a port element 13 is provided which communicates between the area in the cylinder and the area between the drill stem and the bore hole wall. Thus, the thrust of the fluid head within the drill stem exerted on the face of valve 9 is equalized by the thrust of the fluid mud head between the drill stem and the bore hole wall exerted through port 13 and on the base of valve 9 in the cylinder. It is also within the concept of the present invention to provide a mechanical or pneumatic surge tank to store hydraulic energy of the mud in the lower part of the drill pipe.
The present invention is broadly concerned With apparatus for providing a pulsing, jetting action of the fluid from the drill bit. This is provided by the operation of a mechanical valve which remains closed until a predetermined relatively high pressure is reached. At this point the valve, due to its design, snaps open thus releasing the stored energy of the mud through the jets, thus providing a jet action. At a predetermined point, the valve snaps closed and the cycle is repeated. The number of cycles per minute may vary appreciably depending upon the particular structure being drilled as well as upon other related factors, such as the rotational speed of drilling. A satisfactory drilling rate is from about 80 to 150, preferably, from about 120 to 140 revolutions per minute. Under these conditions, it is desirable to jet the fluid from about 1 to 10, preferably from about 2 to 5 times per revolution.
By operating in accordance with the present invention, a pump of relatively small horse power may be employed to store hydraulic energy in the drill pipe for a period of time and then cause the energy so stored, to be released in mud jet of very high reaction, which would appreciably increase the speed of drilling.
What is claimed is:
In an apparatus for drilling bore holes into subterranean surfaces an improved drill bit assembly which comprises a drill bit attached to the lower end of a pipe string, ports in said bit communicating by means of a common conduit to within said pipe string, a valve assembly positioned above said bit and concentrically disposed within said pipe string comprising a piston element which seats on a seat formed at the juncture of said conduit and a surface of the bit, and a cylinder element in which said piston element slides, said cylindrical element being rigidly positioned with respect to said pipe string by suitable brace elements, a vent communicating from within said cylindrical element above said piston to without said pipe string, a spring means positioned within said cylindrical element so as to exert a downward thrust on the piston element so as to seat the piston element in said seat, thereby controlling the flow of fluid through said conduit, said piston element being characterized by being upwardly flared and extending above said seat, whereby a predetermined lateral force exerted by the fluid head within said pipe string will exert an upward thrust component on said piston valve element which will exceed the downward thrust exerted by said spring means, whereby said piston element will move upwardly and allow free communication through said common conduit.
References Cited in the file of this patent UNITED STATES PATENTS 842,049 Wolski Jan. 22, 1907 1,853,379 Rotinotf Apr. 12, 1932 2,045,368 Reed June 23, 1936 2,422,031 Merten June 10, 1947 2,507,585 Bassinger May 16, 1950