US 3416614 A
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Den 1968 R, J. sooowm ETAL 3,416,514
vHYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIVES 2 Sheets-Sheet 1 Filed Dec. 27, 1965 QJ. Q
INVENTORSI ROBERTJ. GOODW I ERNEST A. MORI, JOSEPH L. PE/(AREK, 1241/4 W SCI/.405 ROBERT'E. Z/NKHAM v1958 R. J. GOODWIN ETAL 3,416,614
HYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIVES 2 Sheets-Sheet 2 Filed Dec. 27, 1965 (53/13/W) in? do Hie/3C7 mvswroRs' ROBERT J. aaaoww, ERNEST .A. MORI,
JOSEPH L. PE/(APE'K, PAUL W 567/408 9 ROBERT 1 Z/IV/(IMM United States Patent HYDRAULIC JET DRILLING METHOD USING FERROUS ABRASIV ES Robert J. Goodwin, Oakmont, Ernest A. Mori, Hampton Township, Allegheny County, and Joseph L. Pekarek and Paul W. Schaub, Penn Hills Township, Allegheny County, Pa., and Robert E. Zinkham, Richmond, Va., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Dec. 27, 1965, Ser. No. 516,290 4 Claims. (Cl. 175--67) ABSTRACT OF THE DISCLOSURE A method of drilling hard rock formations in which particles of ferrous abrasives having a size in the range of 7 to 80 mesh are suspended in a drilling liquid. The drilling liquid is pumped down rotating drill pipe in a well and discharged at a velocity of at least 500 feet per second through tungsten carbide noZZles in a drill bit at the lower end of the drill pipe to cut the formation being drilled. The ferrous abrasives give increased drilling rates with reduced wear of the nozzles in the drill bit.
This application is a continuation-in-part of copending application Ser. No. 311,088, entitled Method and Apparatus, fi'ed Sept. 24, 1963 by Robert J. Goodwin, Ernest A. Mori, Joseph L. Pekarek, Paul W. Schaub and Robert E. Zinkham, now abandoned.
This invention relates to the drilling of wells, and more particularly to an improved drilling process in which a stream of drilling liquid containing suspended ferrous abrasive is discharged at extremely high velocities against the bottom of a borehole to drill through hard formations.
Improvements in conventional rotary drilling processes have greatly increased rates of drilling in soft formations and formations of medium hardness. To a large extent, the improvements have resulted from more powerful equipment which allows the application of greater bit weights to cone or drag-type bits. One type of bit that is used widely to drill soft formations is referred to as the jet bit. It differs from the usual bit principally in directing the drilling mud against the bottom of the hole to clean the bottom of the hole rather than over the surface of the cutters to keep the cutters clean. The purpose of jet bits is to improve the removal of cuttings broken from the formation by the mechanical cutting elements of bits rather than to cut grooves in the formation being drilled; however, some penetration of soft formations by the stream of drilling mud may be responsible for some of the increase in drilling rate. Quick removal of the cuttings from the bottom of the hole reduces shielding of the bottom of the ho e from the bit by the cuttings and reduces regrindin-g of cuttings. The conventional jet bits have been ineffective in increasing substantially the rate of drilling in hard formations.
Recently, a novel hydraulic jet drilling process which is effective in increasing the rate of drilling of hard formations has been developed. In the hydraulic jet drilling process, an abrasive-laden liquid is discharged at extremey high velocities against the bottom of the hole to cut the formation being drilled and remove cuttings from the hole. Substantially all of the penetration of the rock being drilled in the hydraulic jet drilling process is accomplished by the abrasive-laden stream, and mechanical removal of rock from the bottom of the hole by engagement with a bit is restricted to removal of ridges which may extend upward between grooves cut by the high-velocity stream. In the hydraulic jet drilling process, the weight applied to the nozzle head, referred to for convenience as the bit, is approximately one-fourth, or less, of the weight applied in comparable conventional drilling methods. Hydrau ic jet drilling in hard formations is substantially faster than drilling with conventional rock bits but is still relatively slow compared to drilling in soft formations, and further increases in hydraulic jet drilling rates are desirable.
The high velocity at which the abrasive-laden stream passes through nozzles in the bit causes rapid erosion of the nozzle with a resultant increase in the diameter of the orifice in the nozzle. Because the rate of drilling is highly dependent upon the velocity at which the abrasive-laden stream strikes the bottom of the borehole, the reduced velocity resulting from enlargement of the nozzle orifice reduces the drilling rate and makes it necessary to replace the bit. In deep wells, a substantial part of the rig time can be used in making the round trips necessary to replace the bit. For this reason, it is important to reduce the rate of erosion of the nozzles.
When the high-velocity stream of abrasive-laden liquid strikes the formation being drilled, the abrasive, aswell as the formation, is subjected to severe stresses. When sand is used as the abrasive in the drilling, approximately one-half of the sand is broken up in a single pass through the bit into fine particles unsuited for further use. The large amounts of abrasive consumed cause the abrasive to be an important part of the cost of the hydraulic jet drilling process. It is desirable to use an abrasive that breaks up only to a negligible extent on striking the bottom of the borehole and, hence, can "be reused to reduce the abrasive requirements.
This invention resides in a hydraulic jet drilling method for the drilling of boreholes in hard formations in which a ferrous abrasive is suspended in a liquid to form a drilling liquid that is discharged through nozzles spaced at different distances from the center of rotation of a drill bit to cut a plurality of concentric grooves over the major portion of the bottom of the borehole. The drilling liquid is discharged from the nozzles at a distance of inch to 1% inches above the highest portion of the bottom of the borehole and at a velocity of at least 500 feet per second. The liquid in which the ferrous abrasive is suspended to form the drilling liquid has an apparent viscosity on the Fann viscometer of at least 50 centipoises at 600 rpm. and a minimum zero gel strength, also measured on the Fann machine, of 50 pounds per square feet both before and after passing through the nozzles.
FIGURE 1 of the drawings is a diagrammatic flow sheet of this invention showing a system for handling the drilling liquid used in the drilling process of this invention with the lower portion of the borehole enlarged.
FIGURE 2 is a chart comparing the rate of penetration of a hard rock by a drilling liquid containing a ferrous abrasive with the rate of penetration by a drilling liquid containing sand in hydraulic jet drilling processes.
FIGURE 3 is an enlarged diagrammatic view of the drill bit shown in FIGURE 1.
In the hydraulic jet drilling process of this invention, particles of ferrous abrasive are suspended in a liquid to form a drilling liquid which is pumped down drill pipe having a drill bit mounted on its lower end. The drill bit has a plurality of nozzles opening through its lower end for discharging the drilling liquid at a high velocity against the bottom of the borehole to penetrate the bottom of the borehole. The nozzles are positioned at different distances from the center of rotation to cut a plurality of concentric grooves in the bottom of the borehole as the bit is rotated. The nozzles may be positioned to cut overlapping grooves, but it is preferred that the nozzles be positioned to cut a central hole in the bottom of the borehole and a plurality of concentric grooves spaced from one another to leave intervening ridges which can easily be mechanically broken.
The drilling liquid is pumped down the drill pipe at a rate and pressure to cause a pressure drop through the orifices of at least about 4,000 p.s.i. to impart a velocity of at least 500 feet per second, and preferably more than 600 feet per second, to the drilling liquid discharged from the nozzles. Stand-off bars on the bottom of the drill bit body extend downwardly below the nozzle outlets and maintain the desired spacing of inch to 1 /4 inches from the nozzle outlets to the ridges on the bottom of the borehole.
After the discharge from the nozzles, the drilling liquid and entrained cuttings circulate upwardly through the borehole around the drill pipe and are discharged at the surface for treatment to remove cuttings and put the drilling liquid in condition for recirculating in the drilling system.
The ferrous abrasive used in the hydraulic jet drilling process of this invention may be either cast iron particles or steel particles readily available as commercial products used in the cleaning and treating of metal surfaces. Ferrous abrasives can be manufactured by blowing a highvelocity stream of air or steam against molten cast iron or steel to separate globules of the metal. The globules are blown into water where they are chilled. The solidified particles are heat treated and graded by size. Grit is prepared by crushing shot and then heat treating the granular particles and grading them according to size. Either angular granular particles, referred to as grit, or rounded particles, referred to as shot can be used, but the shot are preferred because of faster cutting rates obtained with them.
The ferrous particles used in this invention have a size larger than 80 mesh in the US. Sieve series. The drilling rate is faster with the particles of larger size, and it is desirable to use the largest particles that will pass through the nozzles in the drill bit without plugging the nozzles and that can be handled by the high-pressure pumps. In nozzles having an orifice Ms inch in diameter, ferrous abrasive particles in the range of 7 to 80 mesh can be used. A preferred range of abrasive particle sizes is 16 to 50 mesh. Larger particles can be used with larger orifices, but it is not possible to handle particles much larger than 7 mesh with the pumps presently available. An arrangement that has been used successfully with inch nozzles is to screen all cuttings and abrasive particles larger than mesh before delivering them to the high-pressure pumps. Ferrous abrasive particles in the 50-80 mesh range cause drilling rates approximately equal to sand particles in the preferred range of particle sizes for sand and are retained in the drilling liquid to reduce the amount of abrasives required.
The ferrous abrasive particles are suspended in a drilling liquid in a concentration of /2 to 6 percent, preferably 1 to 4 percent by volume. Higher concentrations increase the amount of abrasive in the system and the total break-up of the abrasive without a corresponding increase in drilling rate. Lower concentrations of abrasive markedly reduce the drilling rate.
Drilling liquids suitable for use in hydraulic jet drilling processes using sand as an abrasive are not suitable for use in this invention. The drilling liquids used to suspend the ferrous abrasive must have a relatively high gel strength and viscosity to remove the abrasive from the hole during the drilling operation and to prevent settling of the abrasive in the borehole when it is necessary to stop the circulation of the drilling liquid. The drilling liquid should have a minimum viscosity of at least 50 centipoises as determined on the Fann viscometer at 600 rpm. and an initial or zero time gel strength of at least 50 pounds per 100 square feet. The drilling liquid should have a pH of at least 8.5 and preferably in the range of 8.5-10. Viscosities and gel-strengths above the minimum specified are necessary to prevent excessive settling of the ferrous abrasive from the drilling liquid on those occasions when circulation of the drilling liquid in the hole is interrupted. We have found that many of the compositions ordinarily employed to increase the viscosity of liquids suffer a serious reduction in viscosity upon passing at high velocities through nozzles such as those in the drill bit. It is not only essential that the drilling liquid have the minimum specified viscosity in gel strength as it is pumped down the drill pipe, but it is also essential that the viscosity and gel strength of the drilling liquid be above the minimums specified after passing through the nozzles at a rate resulting in a pressure drop through the nozzles of at least 4,000 p.s.i.
A suitable drilling liquid is an invert emulsion of water and diesel oil containing 30 to 60 percent oil, with the oil in the continuous phase. A preferred drilling liquid is an invert emulsion containing 40 to 50 percent diesel oil. The emulsion can be stabilized by, for example, a sulfurized potassium soap of tall oil containing 5 percent sulfur. Other emulsifiers, such as polyhydric alcohol fatty acid esters, sulfated sperm oil soaps, and polyvalent metal soaps of rosin acids can be used. The pH of the drilling liquid is adjusted to the range of 9 to 10 by the addition of alkaline material such as caustic soda. Another suitable drilling liquid is an aqueous dispersion of bentonite containing 2 percent bentonite and l .to 2 percent Flosal, a fibrous asbestos material. The Flosal drilling mud should have a pH of 8.5 to 9.5 to reduce corrosion of the drilling equipment and abrasive. Hydraulic jet drilling with a ferrous-abrasive-laden drilling liquid is not limited to the use of any particular drilling liquid as long as the drilling liquid has adequate gel strength and viscosity to give satisfactory suspension of the abrasive particles.
For purposes of illustration, a hydraulic jet drilling process will be described in which 20 to 40 mesh particles of lndogrit, a cast iron granular material, manufactured by Industeel Company of Pittsburgh, Pa., is suspended in a concentration, by volume, of 2 percent in an invert emulsion drilling liquid containing 50 percent dieseloil. The drilling liquid is delivered by high-pressure pumps 10 through a line 12 into the drill string 14 of a drilling rig 16 suitably equipped to rotate the drill string in the borehole. The drilling liquid is pumped at a high rate downwardly through the drill pipe 14 and discharged against the bottom 18 of the borehole 20 through nozzles /s inch in diameter in a bit 22 at the lower end of the-drill pipe. Drill pipe 14 is rotated at a rate of at least 5 rpm. during the drilling.
The drilling liquid and entrained cuttings pass upwardly through the borehole and are discharged therefrom through line 24 and delivered to a shale shaker 26 in which oversize cuttings larger than 10 mesh are removed from the drilling liquid. Ferrous-grit-laden drilling liquid is delivered through line 28 to a bank of cyclone separators 30 in which abrasive particles are separated from the liquid and delivered as an underflow through line 32. Overflow from separators 30 is delivered through line 34 to a second bank 36 of separators in which further clean-up of ferrous-grit particles from the drilling liquid is accomplished, and the ferrous-grit particles separated in separators 36 are discharged as underfiow through line 38.
Overflow from separators 36, which contains less than 0.2 percent particles larger than 200 mesh, is delivered into a storage tank 40. Ferrous-grit-free drilling liquid is withdrawn from tank 40 through line 42 and passed through another bank of cyclone separators 44 for removal of fine solid particles of 200 mesh size and smaller to reduce the concentration of larger than 200 mesh particles to a trace and control the density of the drilling liquid. Clean drilling liquid from the separators 44 is delivered through line 46 to the high-pressure pumps 10. Abrasive from lines 32 and 38 is mixed with the clean drilling liquid for recirculation in the well. Because of the low rate of break-u p of ferrous abrasives, removal of fines from all of the liquid circulated in the borehole is not required and drilling liquid may be delivered from the shale shaker directly to pumps 10 through a suitably valved bypass line 48. Heat exchangers 47 and 49 are provided for control of the tance of A inch to 1% inches above the ridges in the bottom of the borehole. Stand-off bars 62 are also subjected to severe abrasion and are constructed of a hard material such as tungsten carbide. By cutting a central hole and a temperature of the drilling liquid- A e p r ture f 4 5 plurality of closely spaced concentric grooves, the inter- 170 F. is preferred when using the invert emulsion drillvening ridges are thin and unsupported which allow them ing mud. Tests on nozzles in the drilling bit have indicated t b readily b k f o th b tt f th h l by th that drilling liquid temperatures above 140 F. increase t d- 1f b nozzle life- Valves at e provided as required to allow The ferrous grit particles are effective in increasing the livery of liquid from tank 40 directly or indirectly through drilling rate over that which is obtained with other abrasepafatofs t0 P p 10, Or to circulate the drilling sive particles such as sand. A series of tests was made in q Ah Screen 51 in line 12 eIhOVeS large Solid which the abrasive-laden drilling liquid was discharged Particles which might P hOZZleS in the drill Make'up from a single nozzle onto a block of hard black granite abrasive is added to the system at shale shaker 26 from rotated in a horizontal plane about an i 11 inches Storage pp 15 from the bit axis at a rate of about 30 r.p.m. The outlet of For effective drilling by the hydraulic l drilling the nozzle was maintained /2 inch from the original rock method, the drilling llquid must be discharged at a Veloe' surface during the tests. The tests were made at a nozzle lty of at least 500 feet P Second, and Preferably at least inlet pressure of 5,000 p.s.i. and a drilling liquid velocity 600 per second: from nozzles having an Outlet 1/2 of approximately 776 feet per second. Each test was conto 11/2 m f bottom the borehole- In tintued for a period of 20 seconds after which the depth of cal hydrauhc let drlnmg opfiranon the four Pumps 10 the out was measured to give an indication of the drilling supPly a total of about 21000 t 2,400 PQ i rate. Test runs were made on drilling liquids containing deliver 450 to 600 gallons per mlnute of the drilllng l quid difierent Concentrations of 20 40 mesh cast iron and at a pressure of 5,000 p.s.1. to the drill pipe 14 for delivery with Sand of the same Size The results are Presented in a drill bit having Pluriility typical S FIGURE 2. The data presented in FIGURE 2 ShOW that 1 g. sutch an Operatlon W111 have 10 to 20 nozzles Inch ferrous abrasives cause much higher drilling rates than sand in hydraulic drilling operations.
Refemng FIGURE blt 22 1S Shqwn havlpg During the cutting test described above, the drilling liq- Outer nozzles 52 54 posltloned and slanting to uid samples were caught, diluted, screened, dried, weighed, charge? stream agamst the .bottom of the borehole and sieved, and reweighed. These data were then reduced to locimon to cut a hole having d enough gauge to an average percentage of particles larger than 40 mesh gf f i i a g zggsg ggi fi fi g' gz sggg broken to smaller than 40 mesh. The results of the partoward the center of rotation of the drill bit to cut a central tlcle breakup determmauons are presented m Table hole in the bottom of the borehole. Intermediate nozzles TA I 58 are provided between the inner nozzle 56 and the outer Matarial and mesh rangfi. Percent breakup nozzles to cut grooves in the bottom of the borehole be- 20 40 mesh Sand 50 60 tween those out by the inner nozzle and the outer nozzle. 204) mesh Steel i fig The number of intermediate nozzles 58 and their location 20 40 mesh ferrous grit 14 will depend upon the size of the borehole being cut. A sufiicient number of nozzles at different radial distances Because Of the eXtfeIhelY g VelOCltleS 0f the dfllhhg from the center of rotation of the drill bit should be proliq p g through the nozzles, erosion f the nozzles vided to cause penetration of the formation being drilled is n important factor in determining the feasibility of to be accomplished by the high velocity abra iv t am dra=ulic jet drilling. A series of tests was run in which 20 and to cause the major portion of the rock removal to be to 40 mesh sand particles were pumped through a nozzle the result of cutting by the abrasive stream. The nozzles having a inch diameter inlet tapering down to a /8 inch may be positioned so that there is some overlapping of the diameter orifice over a distance of 2 /2 inches and a paths traveled by the drilling liquid discharged from the straight section A; inch long and A5 inch in diameter exnozzles. It is preferred, however, that the nozzles be tending from the orifice to the nozzle outlet. In the test, spaced to cut grooves in the bottom of the borehole sepa- 5O suspensions of 20 to 40 mesh cast iron and of 20 to 40 rated by thin, easily broken ridges that are exposed on mesh sand were caused to flow through the nozzle at rates their inner and outer faces whereby they can be easily giving a pressure drop across the nozzle of 5,000 p.s.i. or broken by bit weights not exceeding about 700 pounds more. The nozzles were constructed of two types of tungper inch diameter. sten carbide. The results of the tests are presented in The nozzles in the bottom of the bit for the discharge Table II.
TABLE II.NOZZLE WEAR TESTS [Test duration, 6 hours] Pressure Increase in Nozzle designation Abrasive Cone. per- (p.s.i.) nozzle cent by Vol. across diameter nozzle (inch) Tungsten carbide I Cast iron 1. 5 7, 000 0.0018
D Sand (20-40)- 6 5, 000 0. 004-0. 005 Tungsten Carbide II Cast iron 1. 5 7, 000 0. 0036 Sand (20-40) 6 5, 000 0. 013
support the bit with the orifice outlet at the desired dis- The results presented in Table II show that nozzle wear is much lower when a ferrous abrasive is suspended in the drilling liquid than when the abrasive is sand in spite of the fact that the ferrous abrasive causes a much higher drilling rate. Because the drilling rate is a measure of the ability of the drilling liquid to out a hard surface, it is surprising that the nozzle erosion is less when iron grit is suspended in the drilling liquid than when sand is suspended in the drilling liquid.
Both cast iron and steel shot and grit are highly advantageous in hydraulic jet drilling operations in making possible high drilling rates through very hard rock formations. The high drilling rates can be obtained with a relatively low rate of erosion of the nozzles through which the drilling liquid is discharged against the bottom of the hole. Moreover, the low rate of breakup of the ferrous grit particles allows their repeated use, and thereby greatly reduces the cost of the abrasive required in hydraulic jet drilling.
1. A hydraulic jet drilling process for the drilling of boreholes in hard rock formations comprising suspending 7-80 mesh ferrous abrasive particles in a concentration of /2 to 6 percent by volume in a liquid to form a drilling liquid having a minimum viscosity of 50 centipoises at 600 rpm. on the Fann viscometer, a zero gel strength of at least 50 pounds per 100 square feet, and a pH of at least 8.5, pumping the drilling liquid down drill pipe in the borehole to a bit mounted on the lower end of the drill pipe, discharging the drilling liquid from downwardly opening nozzles in the bit at a velocity of at least 500 feet per second, rotating the bit whereby the streams of drilling liquid discharged from the nozzles cut a plurality of concentric grooves in the bottom of the borehole, said nozzles being spaced at different radial distances from the center of the bit whereby a central hole and a plurality of concentric grooves are cut in the bottom of the borehole with the outer groove having desired borehole diameter and the grooves are separated by intervening ridges having a maximum thickness of about /2 inch, supporting the drill bit on said intervening ridges with the outlet of the nozzles A1 inch to 1 1 inches above the ridges, and circulating cuttings upwardly around the drill pipe.
2. A process as set forth in claim 1 in which the pressure drop through the nozzles is at least 4,000 p.s.i.
3. A hydraulic jet drilling process as set forth in claim 1 in which the drilling liquid is an invert emulsion and is passed through heat exchangers before pumping down drill pipe in the borehole to maintain the drilling liquid in 8 the range of to F., and the internal surfaces of the nozzles are tungsten carbide.
4. A hydraulic jet drilling process for the drilling of boreholes in hard rock formations comprising suspending 7-80 mesh ferrous abrasive particles in a concentration of /2 to 6 percent by volume in a liquid to form a drilling liquid, delivering the drilling liquid down drill pipe in a well to a drll bit, rotating the drill bit about a vertical axis, discharging the drilling liquid at a velocity of at least 500 feet per second downwardly and outwardly from outwardly slanting first nozzles in the bit near the perimeter thereof to cut a borehole of the desired gauge, discharging drilling liquid downwardly and inwardly at a velocity of at least 500 feet per second from an inwardly slanting nozzle positioned near the center of the bit to cut a central hole, discharging drilling liquid downwardly at a velocity of at least 500 feet per second from intervening nozzles between the first nozzles and the inwardly slanting nozzle to cut grooves in the bottom of the borehole with intervening ridges having a maximum thickness of about /2 inch, supporting the bit on the bottom of the borehole with the nozzle outlets inch to 1% inches above the bottom of the borehole, circulating the drilling liquid and entrained cuttings upward through the borehole around the drill pipe, and discharging the drilling liquid and entrained cuttings from the well at the ground surface.
References Cited UNITED STATES PATENTS 878,208 2/1908 Kirschniok 67 2,315,496 4/1943 Boynton 166222 X 2,758,653 8/1956 Desbrow 166222 X 3,130,786 4/1964 Brown 166-223 X FOREIGN PATENTS 230,078 7/ 1925 Great Britain.
JAMES A. LEPPINK, Primary Examiner.