US3016098A - Vibratory drilling - Google Patents

Description

Jan. 9, 1962 ECKEL T I 3,016,098

VIBRATORY DRILLING Filed March 11, 1958 2 Sheets-Sheet l JOHN E. ECKEL EVERETT H. LOQK INVENTORS BYw (27W ATTORNEY 1952 J. E. ECKEL ETAL 3,016,098

' VIBRATORY DRILLING Filed March 11, 1958 2 Sheets-Sheet 2 JOHN E. ECKEL EVERETT H. LOCK INVENTORS nv w. ATTORNEY United States Patent 3,016,098 VIBRATORY DRILLING John E. Eckel and Everett H. Lock, Tulsa, Okla., as-

signors, by mesne assignments, to Jersey Production Research Company Filed Mar. 11, 1958, Ser. No. 720,767

7 Claims. (Cl. 17556) The present invention is concerned with an improved apparatus for drilling well boreholes into the earths substrata. The invention more specifically relates to an improved apparatus for rotary drilling employing a vibratory vertical thrust. In accordance with the specific adaptation of the present invention, theenergy dissipation to the surrounding drilling liquid when employing a vibratory bit assembly, particularly a high-frequency bit assembly, is materially decreased by the utilization of a unique gaseous buffer zone.

In the exploration for oil, the art of drilling well boreholes 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 apparatu 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, rotate a drill bit. For a number of reasons, there are attached, to the lower end of the drill pipe, heavy sections of pipe termed drill collars. Also, for a number of purposes, a weighted liquid called drilling mud is circulated in one direction through the drill stem and in the opposite direction through the annulus between the drill stem and the borehole. In these drilling operations, it is known that rocks subjected to alternating stresses will fail rapidly in .fatigue. This effect is responsible to some extentfor the action of conventional rock bits, wherein toothed cutters rolling on the surface of the rock impart alternating stresses to the surface of the rock, resulting in chipping, fracturing, and crumbling of the 'rock being drilled. The conventional rock bit, however, depends to a very great extent for its cutting action upon compressive stress induced by extreme weight on the bit. This is secured by allowing the weight of'the drill string to partially rest on the bit. This process, while entirely satisfactory, has a number of inherent difficulties. may be in compression, resulting in buckling of the pipe which in instances causes the hole to deviate from the vertical. vFurthermore, the stressinduced due. to the buckling and unbuckling of the compressed pipe results'in corrosion fatigue. To reduce this difficultyjdrill collars, which are heavy lengths of pipe, are used. These are expensive and are subject to frequent failures. Another disadvantage is that the friction against the walls of the hole causes the drill pipe to wind up, with the resultvthat a substantial amount of bouncing of the bit occurs on the bottom ofthe hole. This aggravates the wearing of the cutter bearings in rock bits. Thus, this is not 'anfefiicient way to induce alternate stresses of the magnitude and For example, part of the drill pipe Thus, the principles of this invention may be appreciated by considering simple drilling tests. Thus, in shattering hard formations with a drill as, for example, of the nature of the star drill, it can be readily established that the most effective penetrating force is achieved by imparting a combination torsional and percussive action to the drill bit. The resultant motion at the actual drill teeth or other cutting surfaces is downwardly inclined and results in an inclined force which serves to hammer and shear the formation encountered by the drill. Depending upon the composition of the formation to be drilled, thelongitudinal and torisonal components of the drill movement should be varied for best results. Again, depending on the composition of the formation to be drilled, the phase relationship between the downward and rotary motion of the drill should be varied. In this connection, it is a principal object of this invention to provide a simple and effective drilling apparatus capable of varying the phase .and magnitude of the combined longitudinal and torsional vibrations that are applied to a drill bit. It is also an object of the invention to separately or jointly control the amplitudes of the vibrations.

In addition to the observation that a combination torsional and percussive action in a drill. bit provides the most effective penetrating force, it has also been observed that other factors have pronounced effects upon the effec tiveness and efficiency of a drilling apparatus or method. Furthermore, it has been found that these factors tend to differ markedly in their relative importance, depending upon the type of formation being drilled, the depth of the formation, etc.

Accordingly, it is one object of the present invention to provide a drilling apparatus which is superior to existing apparatus and methods in its ability to drill effectively and efliciently through a wide variety of earth formations. It is another object of the invention to provide a drilling apparatus which is much more readily adapted to chang ing drilling conditions than are conventional apparatus and methods. It is stillanother object of the invention to. greatly reduce the time and money that are presently required in drilling a borehole by greatly reducing the time required to ascertain and adjust to the best drilling conditions for various formations and structures that are penetrated by the borehole.

, Q While, as pointed out above, a vibratory bit such as de-' scribed in US. 2,554,005, issued May 22, 1951, Earth.

Boring Apparatus, A. G. Bodine, In, possesses many advantages, the enery dissipation to thesurrounding liquid In accordance with the present invention, this energy dissipation is materially decreased by utilizing a unique gaseous buffer zone positioned'in the bit assembly. A specific adaptation is to employ an annulus which is filled with an inert gas, such as air or nitrogen. A

particular apparatus is one that, when thepressure builds up in the drill pipe, a differential area valve opensthe pressure chamber to an orifice so as to very slowly bleed nitrogen or other inert gas into the pocket and maintain a gas buiier pocket while drilling. By this method, the pressure from the escaping gas also forces mud and shale accumulation from the pocket.

The apparatus of the present invention may be more fully understood by reference to the attached drawings illustrating embodiments of the same.

FIGURE 1 illustrates the gas pocket wherein the pocket is open to the surrounding liquid drilling fluid.

FIGURE 2 illustrates an adaptation of the present invention wherein the gas surge pocket is separated from the surrounding drilling liquid by means of a movable piston element.

Referring specifically to FIGURE 1, a drill bit assembly is shown disposed in the bottom of borehole l which extends to the earths surface. The drill bit assembly is attached to the lower end of drill collar 2. For the purposes of clarity and simplicity, the device imparting the vibratory motion to the drill bit assembly which is positioned generally at the upper end of the drill collar is not shown, since these means are well known in the art. The vibration-inducing apparatus may be hydro-driven or may be of the electrical type such as a magnetostnictive transducer or solenoid driven. Also for the purpose of simplicity, the mechanical filter or isolator positioned be tween the drill stem and the drill collar is not shown, since these devices are also well known in the art. In general, these filters or isolation devices prevent the vibratory motion from being imparted upwardly through the drill stem.

These filters may be of the air-pocket type or springactuated type.

As pointed out heretofore, the present invention is particularly concerned with a drilling apparatus wherein high firequencies are employedas, for example, frequencies in the range from about to 500 cycles per second. A particularly desirable frequency is about 300 cycles per second. In general, the amplitudes vary from about 0.0001 to 0.25 inch. A desirable amplitude is in the range of about 0.01 inch.

The drill bit assembly, as illustrated in FIGURE 1, which is attached to the lower end of drill collar 2 comprises an upper cylindrical butler element 3 which contains a hollow annulus 4 positioned between an inner wall 20 and an outer wall 6.

A satisfactory type bit 7 is attached tothe lower end of cylindrical butter element 3. This bit may be of any type employed in rotary drilling, such as a fish tail bit, a star bit, or the frusto-conioal roller-type bit.

Cylindrical element 3 containing a hollow annulus is characterized by having said annulus sealed into upper and lower separated spaces. The lower space of said annulus, comprising a surge chamber 8, communicates at its lower end to the annulus between the borehole Wall and wall 6 through ports 9.

In operation, the upper space or chamber of said annulus is filled at the surface with gas through filler valve 10 so as to secure a relatively high-pressure gas in the upper space of said annulus. A metering valve 11 is adjusted so as to permit a predetermined rate of flow through said valves when a bleeder valve 12 is opened as hereinafter described.

The assembly is lowered into the well borehole after the upper space of said annulus is filled to high pressure with inert gas. The mud pumps are then started, forcing mud, liquid, or other suitable drilling fluid downwardly within the pipe stringthrough mud channel 13 within said cylindrical element, through bit 7, and upwardly in the annulus between the pipe string and the borehole wall. This mud pressure will exert a thrust on bleeder valve 12. Thus, inert gasas, for example, nitrogen-will flow through metering valve 11, through bleeder valve 12, into the upper portion of surge chamber 8. 7

Thus, as the drill bit assembly vibrates as hereinbefore described, gas accumulated in surge chamber 8will compress and decompress to compensate volumetrically forliquid movement caused by the motion of the vibrating steel. The gas being compressible, little energy is consumed in the vibrating process. By operating in this manner, the major part of the energy otherwise lost in lifting a long column of drilling liquid (generally known as pumping the liquid) is eliminated or materially reduced.

Referring specifically to FIGURE 2, the apparatus is substantially similar to that described with respect to FIGURE 1. Similar parts of FIGURE 2 are numbered identically with the corresponding par-ts of FIGURE 1. FIGURE 2 shows a doughnut-shaped piston element 15 positioned above ports 9 which in eflect substantially seals ott the upper end of surge chamber 8 from contact with the drilling liquid. In operation, the piston moves upwardly and downwardly, thus acting as a cushion for the vibratory movements and thereby materially decreasing the energy which would otherwise be lost to the surrounding liquid. Piston 15 is provided with a check valve 16 which permits the gas to bleed from the surge chamber to the liquid when the pressure within the surge chamber exceeds a predetermined maximum.

As pointed out heretofore, the invention is concerned with an improved apparatus for drilling when utilizing vibratory drilling techniques. By the utilization of a gaseous surge chamber, appreciable amounts of energy are conserved which can greatly increase the effectiveness and rapidity of the drilling rate.

Having described the invention, it is claimed:

1. An improved vibratory bit assembly which comprises a bit attached to the lower end of an elongated cylindrical absorber, the upper end. of said absorber being attached to the lower end of a drill collar, said absorber being characterized by having an inner wall which forms a con tinuous and uninterrupted passageway from within said drill collar to within said bit, said absorber having an outer wall thereby forming an annular space between said inner and said outer walls, a partition Within said annular space to form a top annular chamber. and a bottom annular chamber separated one from the other, ports in the outer wall at the lower end of said bottom annular chamber thereby forming a passageway from within said bottom annular chamber to the exterior of said absorber such that the volume of said annular chamber is in substantially direct fluid communication with the exterior of the absorber, and valve means controlled by mud pressure for permitting continuous controlled flow of gas from said top annular chamber to the upper section of said bottom annular chamber.

2. Apparatus as defined by claim 1 including a doughnut-shaped movable piston in said lower annular chamber at a point above said ports.

3. An apparatus of the character described and of a character to be inserted between a drill bit and the lower end of drill string which comprises in combination: a body member of a character to be attached at its upper end to the lower end of said drillstring and attachable at its lower end to said bit, said body member having a pas sage therethrough establishing fluid communication between the interior of said drill string and the interior of said bit; a chamber in said body member and of a character to retain therein 'gas under high pressure; a surge chamber in said body member having a port in the lower portion thereof establishing substantially direct fluid communication between the substantially complete interior of said surge chamber. and theexterior of said body member; a passageway between said chamber and said surge charm ber; and valve control means in said passageway, said valve means being of a character'to openwhen the pressure within said passage reaches a predetermined value to engaging the walls of said chamber above said port.

' 5. In a'drilling system using a circulating drilling fluid 6 and wherein a vibratory vertical thrust is imparted to a 6. An apparatus as defined in claim 5 wherein said rotating bit rotated by a drill string, an apparatus for surge pocket contains an inert gas. minimizing energy dissipated to the drilling liquid which 7. An apparatus as defined in claim 6 wherein said comprises: means for establishing a gaseous surge pocket inert gas comprises nitrogen. at the lower end of the drill string; means for continuously 5 injecting gas into said surge pocket during the circulation References Cited in the file of this patent of drilling fluid; means for maintaining direct fluid communication between the gas in said surge pocket and drill- UNITED STATES PATENTS ing fluid in the space adjacent said bit whereby gas 210- 2,554,005 Bodine May 22, 1951 cumulated in the surge pocket compresses and deco-m- 10 2,815,928 Bodine Dec. 10, 1957 presses to compensate volumetrically for liquid movement 2,824,718 Currie Feb. 25, 1958 caused by the motion of vibrating vertical thrust.

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