GB2410051A - Pressure pulsing apparatus at surface and method for drilling - Google Patents

Abstract

A method for underground drilling comprises generating high intensity pressure pulses at the surface and coupling the pressure pulses into drilling mud 21 being pumped into the drill string 27. The pressure pulses propagate down the drill string to do work at an underground location 34. The pressure pulses are preferably generated by periodically interrupting flow of the drilling mud in a conduit 22, thereby creating a water hammer effect. Intensity of the pulses can be intensified at the bit 30 using nozzles. The pulses can also be used to drive pistons (74, fig 12) to generate vibration. The pulses reduce the torque requirements of the drill.

Description

PRESSURE PULSING APPARATUS AT SURFACE

AND METHOD FOR DRILLING

Cross-reference to Related Applications

1] This application is related to and claims the benefit or the Filing dates of Canadian patent application No. 2,31,021 riled on 9 January, 20G1 and Canadian patent appl cation No. 2c354,994 Filed on 13 August 2001.

Field of the Invention

2] This invention relates to underground IS drilling. In particular, the invention relates to underground drilling methods which involve the creation of acoustic pulses in drilling fluid, the use of such pulses to operate downhole tools, and the use or such pulses to increase drilling rates.

The invention also relates to apparatus adapted to practice the methods of the invention.

Background

3] Deep wells such as oil and gas wells are typically dri led by rotary drilling methods. Some such methods are described in Walter, US patent No. 4, 97G, 577. Apparatus fc rotary dr fling typically comprises a suitably constructed derrick. A drill string having a drill bit at its lower end is gripped and turned by a kelly on a rotary table.

4] During the course of d_llling ooerations, drilling Fluid, often called drilling mud, is pumped downwardly through the hollow drill string.

The drilling fluid exits the drill str ng at he S drill bit and -lows upwardly along the well bore to -he surface. The drilling -luid carries away cuttings, such as rock chips.

5] The drill string is typically suspended from a block and hook arrangement on the derrick. The drill string, comprises a drill pipe, drill collars and may comprise drilling tools, such as reamers and shock tools, with the drill bit being located at the ex.teme bottom end.

6] Drilling a deep underground well is an extremely expensive operation. Great cost savings can be achieved i- the drilling process can be mad" more rapid. A large number of factors arrect the 2Q penetration rate than can be achieved in drilling a well.

7] Around the late 1940s, it was discovered Chat drilling efficiency could be improved by equipping the openings in drill bits, which allow escape of drilling fluid with nozzles. The nozzles provide high velocity jets of drilling fluid a. the drill bit. This innovation resulted in a dramatic increase in achievable drilling rates. Today, almost a l drill kits are equipped with high velocity nozzles to take advantage of this increased efficiency. It s worthwhile to no e that between to - 6% o' all hydrau'ic power ourcur from a mud pump is typically used to accelerate the drl_llng mud in the drl 1 bit nozzles.

8] The flow rate of drilling fluid affects pens ration rates. Rock drill bits drill by forming success ve small craters in a rock face as individual drill bit teeth contact the roe] face.

Once a drill bet tooth has formed a crater, roe} chips must be removed from the crater. The amount of drilling fluid necessary to effect proper chip removal depends upon the type of rock formation being drilled and the shape o' the crater produced by the drill bit teeth. Maintaining an appropriate flow of drilling fluid is important for maintaining a high penetration ate.

9] The weight on the drill bi also has a very significant effec- on drilling penetration races.

I.- adequate cleaning of rock chips from the roe}: fare is effected, doubling o_ the drill bit weight will roughly, double the drilling penetration rate (i.e. drlling/penetration rate is typically directly proportional to weight on the drill bit).

However, i- Inadequate cleaning takes place, further increases in the drill bit weight do not cause corresponding increases in penetration race because rock chips not cleared away are being reground, thus wasting energy. If this situation occurs, one solution is to increase pressure and -low o the do fling fluid in an attempt to effect better clearing of rock chips from the vicinity of the drill bit.

0] Fu_her information on rosary drilling and penetration rate may be round in standard texts on the subject, such as Preston L. Moore's Drilling Practices Manual, published by PennWell Publishing Company, (Tulsa, Oklahoma).

1] Downhole vibrating tools known as mud hammers have been developed in an effort to increase drilling penetration rates. A typical mud hammer comprises a striker hammer which is caused to repeatedly, appl:, sharp blows to an anvil. The sharp blows are transmitted, through She d 112 bit to the tee'_h of the drill bit. This has been found to increase drllllng penetration rates. Mud hammers are expensive to operate as drill hi' fire is significantly reduced by The use of a mud hamme_.

2] In another efo_t to increase dr'lling penetration rates of drill strings has yielded various downhole devices which exploit the water hammer effec_ to create pulsations in thee flow of drilling mud. Such devices Bend To enhance the hydraulic action of the drilling fluid. Their use has a poslive effect on rock chip removal and, consequently, drilling penetration rates. Another effect o these devices is to induce vibrations in the dri" s.-ing, more specifically in the frill bit itself. This too has a positive erect on dulling penetration rates. Examples or such devices can be round -a. US patent No. 4, 819, 75 (Walter,, US patent No. 4, 830, 122 (Walter), US patent No. a, 979, 577 (Walter), US patent No. 5,0Q9, 272 (Walter) and US patent No. 5, 190, 114 (uJalte'-).

3] While the devices described in these patents have proven To be effective at increasing drilling penetration rates they have a number or disadvantages which has prevented their widespread adoption. It is difficult to design such a tool which will operate reliably under the constantly changing properties OT drilling mud and the constantly increasing hydrostatic pressure at downhoe Locations. This problem is exacerbated be the small space within which downhole tools must _. In many drilling situp ions the downhole tools have an outside diameter o,' only 4 3/4 inches.

Space constraints impose onerous constraints on the design o_ such tools. Other problems with these devices include: Downhole conditions are harsh. Operating parts of these tools may not withstand downholP operating conditions To_ extended periods o time.

Operating parameters cannot be adjusted while drilling is ongoing. This makes it dif-icu' r To optimize the performance of these tools.

It is not possible to switch these tools on or ore while drilling. This makes i_ if-icul to ascertain the e r-ec--veness of the tools s ace There is a siari-ican vGri2 ion in drilling Penetation rates from wcll-'o-well even ir

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all driling parameters are kect constant.

During dl'lng, these tools are only accessible Nor repair when they are brought to the surface.

[00141 Despite the signi icant progress Chat has been made in underground drilling technology- over the past century, there remains a need for drilling methods and apparatus which provide increased drilling penetration rates. This need is Any significant increase Summav a- the Invention [00153 This invention provides methods for underground dri_llng which involve generating high intense by pressure pulses a' a_ near the surface and then allowing those pulses to propagate in drilling mud down a drill string. The pulses may cause Fluctuations in the flow of drilling mud exiting nozzles in a drill bit.

tO016J The nven_ion also provides apparatus for producing high intensiLv pulses. m' he apparatus includes a calve which can suddenly substani='lr block a conduit in which drilling mud is flowing, thereby creating a water hammer in the lowing drilling mud. In one embodiment of the invention G oa'-ial flow -rom the same mna pump that 's used -a pump drilling mu_ down a drill string is diverted into pulse generating - ireful.. The pulse geneat ng ircuit in_ludes a conduit hrough wrich drilling muc' can flow and a,-low interrupter valve downstream in the conduit. The apparatus may direct drilling bud exiling the flow interrupter valve may to a mud tank or may comprise a jet pump, or other apparatus in the main mud conduit which causes a reduced pressure a: a location in the main mud conduit where the diverted drilling mud s reintroduced into the main mud conduit. The apparatus includes G valve controller- which operates the flowir.terrupter valve on a periodic basis.

7] Another aspect of the invention provides 1) downhole tools that are operated by pressure pulses propagating down a G'-i] l string according to the nvenon.

8] Further aspects and advantages of the invention are described below and shown in. the accompanying drawings.

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Brief Des--otion of the Drawings [0019] In. drawings which illustrate various non limiting embodiments of the invention: Figure 1A is a schematic view of G typical classic rotary drilling method apparatus, with. a surface acoustic pulse generator (SPA generator) pursuant to one embodiment of The invention; Figure 13 is an enlarged schematic d-agram o the SAP generate= of Flqu,e lAi Figure 2A is a schematic view of a typic' classic rotary drilling apparatus, with an SAP generate' pursuant to an alternative embodiment o- the invention; Figure 2 an enlarged schematic diagram of the SAP generator or Figure 2; Figu'-e 3T, is C schematic view of G _yp-2__1 classic rota-; fir- ling method apparatus, with an SAP generator pursuant to G '-Us the_ alternative embodiment o the invention; Figure BE an enlarged schema_i diagram of the SAP generator of Figure 3; Figure 4 is a schematic view of a typical classic rotary drlll_ng method apparatus equipped with an SAP generator pursuan' to a _utine' alternative embodlmer,' of the invention.; Figure 5P is a schematic view o The SAP generator of Figure 4 and a schematic view of a preferred interrupter valve means pursuant to the invention; Figure 5B is an enlarged sonemaic diagram o_ ah_ preferred _nterruper van ve means of figure 5A; - 9 Figure 5C is a detailed schematic diagram or the preferred interrupted valve means of Figure 5A; FIG 6 is a schematic view o- drilling apparatus including an acoustic pulse generator and a multiple piston telescopic tool located in a drill string above a drill bit; FIG 7 is a longitudinal sectional view of the down hole telescopic tool of Figure 6 shown lo. its "closed" position; FIG 8 -s a longitudinal sectional view or the down hole telescopic tool or Figure 7 shown in its "open" position; FIG 9 is a cross sectional view through a splined par of the telescopic tool of Figure S; IS FIG 10 is G schematic view of a drilling apparatus including G surface acoustic pulse genera_o and a multiple Piston telescopic (MPmj tool in The drill string above one or a few drill collars; FIG 71 is a longituclrlal sectional -view o_ the MET tool in a First position wherein the weight or the portion or The drill string below the '_oo2 is supported by G set of springs; and, F'G 12 is a longitudinal sectional view a' the MAT tool of Figure 11 in a second position which occurs when G pressure pulse lifts the portion o the drill string below the MPT tool.

Detailed Description

0] As required, detailed embodiments of the present Invention. are disclosed herein. However, it is 2c be understood that the disclosed embodiments -1G are mere v e':emplary o' the inrention, which may be embodied in various forms. Therefore, specific SI'UC-U^G1 and functional details disclosed herein.

are nor to be dete'^mined as limiting, bu merely as a basis or the claims and a representative basis Boa teaching one skilled in the a'^t to variously employ the present Invention In vir_ua ly any approp'-'ate'y detailed structure.

10021] This invention provides methods fo^ generating acoustic pulses at the surface and conveying such pulses downhole to downhole tools and/or a a-ill bit. Tn p^ere^red embodiments o the invention, acoustic pulses are generated by interrupting the -low of drilling mud in a conduit and thereby caus ng water hammer in the conduit.

[OC22j rlqure 1A is a schema ic view c_ a vpic-2 rotary d^i'l_ng apparatus 10 which has beer mod Pied tv The add tick or a su^face acous-i pulse generator (SAP generators) 20 according o the invention Figure 1B is a de ailed schematic view of SAP generator 20. Rotary drilling apparatus 20 comprises G mud pump 45 which pumps drilling mud 21 from G mud tank 32 into a stand pipe 22. Pump 45 typically has a rlaclvelv- high capacity and supplies mud 21 under sign ficant pressure The pressure wl- hin stand pipe 22 night be, Boa example, 2,500 psi. Stand pipe 22 delivers mud to the drill string in an;, suitable way. - 11

3] In the illus.-ated embodimen_, stand pipe 22, is Fastened to derrick 23, located on a surface of an area to be dr lied. Flexible hose 43 (made for example o- reinforced rubber! carries the flow of drilling mud 21 from stand pipe 22 into a swivel 24, which is suspended from derrick 23 by a hook. From swivel 24, drilling mud 21 enters a drilling pipe 27 by passing through kelly cock 25 and then kelly 26. Drilling mud 21 is convevec to a drill bit 30 by way of a number of vertically successive drill collars 28, and a bit sub 29. The drilling fluid exits bit 30 through a number or openings. Drilling mud 21 then returns to the su face through the annular well bore 31 surrounding the drill string. At the surface the mud is collected and returned co mud tank 32. The mud may be treated Lo remove cuttings et_. aster i.

is cclleted.

4] Kelly 26 is ypicallv rotated by a rotary Cable 33. The rotation of Kelly 26 is imparted to drill pipe 27, successive dr-11 collars 28, bit sub 29 and drill bit 30. In some cases the drill sc_in may be rotated by a too drive (not shown). or. such 2: cases a kelly is not needed. As shown in Figure lA, SAP generator 20 is preferably installed between mud pump 45 and stand pipe 22.

5] As shown in detail in! Figure lB, some c pressurized drilling mud 21 is diverted at G junction 145 into a conduit 52 as indlca ed by arrow 5. Conduit so is pree^chly made Loom "!eGvy wall pipe. The amount of drl2lino mud diverted into conduit 52 can be adjusted by a flow control valve 48. In Referred embodiments a_ the invention the proportion o drilling mud which is diver_eo al junction 145 is significantly smaller than the proportion o drilling mud in the main flow which continues past junction 145 into stand pipe 22. In the illustrated embodiment, flow contra' valve 48 comprises a needle valve. The flow in conduit 52 can be adjusted by Burning valve stem 49 with knob 50. Valve stem 49 is in threaded engagement 51 with the housing of flow control valve 48. Therefore, rotation. of valve stem 49 causes valve stem 49 to move axially, thereby altering the degree to which valve stem 49 restricts the -low a- fluid into conduit 52. Suitable seals are provided to prevent -'ea;ag& o mud around -have stem 49.

[0026J A sus-an-ia2 portion or the Trilling mud diverted at junction 145 eventually Lows back into mud tan}: 32 (the two mud tanks 32 illustrated In each of Figures 1A and SIB may be different mud tangs but are preferably the same mud tank). SAP generator 20 includes a flow inte-ruc. ing valve 54 operated by a valve controller 55 which causes valve 54 to periodicals,, at leas substantially block the flow of drilling mud 21 out or conduit 52. currently preferred embodiment o' Interrupter valve controller 55 according to this invention is describer below with reference to lqu-es 5A through 5C.

[00271 \7alve controlle -5 mav comprisP any o a wide variety of valve Mongol means. By way of example only, possible valve control means include: electrically operated valve actuators driven by elec ricer or electronic controllers; hydraul-c or pneumatic control circuits; valve members in valve 54 actuated by '-lo-w of mud through Valve 54; and, mechanical valve operating mechanisms comprising cams, relprocarlug members, oscillating members, or the like which move a valve member in valve 54 to periodically interrupt the '-low of do fling mud through valve 54.

[00281 When VG1VP 54 is not blocking th" flow of drilling mud, the d__ll_ng mud flows through v_lve 54 and our of DGr 44. By rapidly blocking the lowing drilling mud in condul. 52, flow interrupting valve 54 generates water hammer pulses which propagate upstream in conduit 52.

9] A pulse transmission means, which is a conduit 56 in the illustrated embodiment, has one end connected to conduit 52 at a location upstream From ine_rupe- va ve 54. Another end o pulse t-ansmissicr conduit 56 jolts main conduit 57, which carries the main flow o drilling mud 2i o stand pipe 22. In preferred embodiments or the invention, a check valve 47 prevents drilling mu rom lowln bask thrOU5.! pulse t- ansmissior.

Fondue 56 into condo 52. Check valve 47 opens to a2 107 drliling mud to low through -onduit 56 -n the direction of arrow 56A on y under the high pressure water hammer pulses generated by _h sudden closing or valve 54.

[OG301 Water hammer induced pressure pulses in conduit 52 are transmitted by pulse transmission conduit 56 Into main conduit 57 where they continue to propagate downstream into the drill string. As the bore or the drill string is typically smalle- than the bore of conduit 57 and othe- conduits through which the mud passes at the surface, the intensity of the Pulses increases as the pulses pass into the smaller diameter bore of he drill string. The pulses may be applied at underground locations to enhance drl2llng performance as described below. Pulses man' also be transmi ted upstream toward pump 45. k pulsation dampens- 147 mG' be provided in main 'ins 57 downstream G- pump 45 and upstream or pulse transmission condui 56 to reduce the ef,ec of SAo generator 20 on the operation of pump 45.

[00313 A shut o' valve 46 and check valv" 47 allow users to isolate SAP generator 20 from the main -low of defiling mud 21 while defiling operations are ongoing. By disconnecting SAP generator 20, drllllng/penerralon races with and without SAP generator 20 can be compared. Further, the operating parameters of SAP generate_ 20 can be adjusted during d-l ins opera ions so op i.lze the performance o_ the do Lana rig.

2] During operation o the apparatus, some cril ing mud 21 -lows in the direction o arrow 53 through flog: control Valve 48 into conduit 52 S 7;o-w-=rd interrupter valve 54. Valve controller 5 causes valve 54 to repeatedly open for a time long enough for -low or drllng mud to be established in conduit 52 and then close relarivel7- suddenly.

Each time this sequence of events occurs z water hummer pulse is generated in condui_ 52. The sudden closure of interrupter valve 54 causes kinetic energy of the mud flowing in conduit 52 to be converted into a high pressure acoustic pulse. The lntens_ y of the acoustic pulse increases in IS roort2n to the velocity of the mud flow in condu t 5 approximately according to the equatlor.: = x Vs x 77 (1, where A?= pressure increase due to water hammer; @= specific mass of drilling muds Vs= velocity of sound in d-'linc mud; and, V = velocity of mud flow in conduit 52.

Further details on the mathematics and physical effects of -water hamper can be found in VG--IOUS texts or, fluid mechanics, including 7iicto- 'A Streeter and E. Benjamin W>,lle's Fluid.=chanics (7 h edition), McGrawH.-'ll Book Company (1979).

[00333 Hater hammer pressure pulses resulting -ram the sudden closures avs1 He 5 travel upstream -tom closed valve 5h, at he velocity c the speed - 16 of sound in the drilling mud inside conduit 52.

This pressure pulse also propagates into conduit 56. Check valve 7 opens and allows the pressure pulse to propagate Into main flow conduit 57. The pressure pulses travel at the speed of sound in the drilling mud through stand pipe 22 and down through the drill string to drill bit 30. The pressure pulses cause oscillations in the,-low of drilling mud exiting through the nozzles of drill bit 30.

This enhances cleaning of Line bottom of well bore 34 and helps to achieve improved drilling penetration rates.

4] Figure 2A is a schma_ic view of a drill rig according to an alternative embodiment or the invention comprising an. alternative SAD g=neato- 35. In this embodiment, dl2linc mud exiting Tom Slav generator 35 is returned to the main flow o_ dri ding mud in conduit 57. The construction OF SAP genera o'- 35 is shown i?. detail in Figure SIB.

venturi 37 is provided In main condul 57. Ventur_ 3, acts as jet pump. The pressure within main conduit 57 is reduced at point 59, which, is in a volume adjacent to venture-' 37. The volume ma; comprise an. annular region surroundln venture 37.

Mud exiting from down stream por_ 44 o- nterrupte valve 54 is returned to main partial Flow of drilling mud 53 at point 59. The pressure difference between junction 145 at which defiling mud reflows into SAP generator 35 and pain_ 59 drives The '-low or drilling mud '.nrougn SAP generator 35.

SAP generator 35 run-ions ct;ewise in th- same manner as the SA generator 20 dscribed above.

High intensity acoustic pulses are delivered into main condui_ 57 at point 40. valve 58 is provided to facilitate isolating SAP generator 35 from main conduit 57. It should be noted that entry o the acoustic pulse can be also inorpora=d down stream, into the venturi arrangement 37.

5] SAP generator 35 provides the advantages that it permits better monitoring of the drilling mud flow and of mud loss in the well bore. It further allows more -legibility in terms of installation. I should be noted that SAP generator may be constructed so that the acoustic pulses are coupled to main conduit 57 at a point i n the venturi arrangement down stream -ram venturi 37.

[00361 figures on and 3B show an ale_na--'ve S.Z.

generator 41 pursuant to an alternative embodiment of this invention. SAP gnera_inc,- circuit 41 is incorporated into a tool 42, which is placed below swivel 24. Cool 42 is pre erably Placed above Kelly cock 25 and kelly 26. SAP generator 41 operates similarly to S.P generator 35, be introduces pulses dlrectiv into the drill string. The pulses do no. need ro trave through flexible hose 43. All other things being equal, SAP generator 41 should produces pulses or higher intensity at droll bi_ 30 than the embodiments described above. Venturi arrangement 37 is incorporated into a lower tool body 6a. A Lop tool sub 65 has G conduit 60 hat al aces c oo-- or- of the main flo7vv- o di33- mud - 18 21 to enter SAP generator 41. Interrupter valve 54 can be a self regulating valve operated by the water hammer itself as is described in US patent No. 5, 54 , 255 (Ma Her), a_ Figures 8 and 9 which As incorporated herein by reference.

7] The main advantage of SAP generator 41 is the' generated acoustic pulses are inserted direct!:, into the drill string and do not have to travel through rubber hose 43, which may tend to somewhat attenuate the pulses. The main disadvantage is Char it is not as easily accessible or servicing and adjustment as SAP 20 or SAP 35.

8] Figure shows an alternative SAP generator pursuant to an alternative embodiment or thins invention. S2o generator 135 is similar to Sac generator 20, save for the fact that it lacks a pulse transmission conduit 56 and che] valve 47.

Pressure guises gene_aed by the sudden closure o interrupter valve 54 rave' upstream From valve 54 and enter mai a. conduit 57 at junction 145.

[OQ39] S2o genera For 135 has an additional flow 2: control valve 148 located between down stream pore 44 of interrupts valve 54 and mud tank 32. Seconc' flow control valve 148 allows the back pressure on valve 54 to be adjusted. Depending upon the construction of valve 54, the performance o valve 54 may be adjusted by alelng the back pressure.

[00401 The SAP generator 135 of Figure 4 has the advantage of simplicity. Flow control valves 48 and 148 car. be adjusted so that just enough drilling mud IiOWS through SAP generator 135 when valve 54 is open to reduce the flow and pressure in main conduit 57 downstream from junction 45.

1] When valve 54 is opened some drilling mud Is diverted through valve 54. A reduced pressure (in some cases zero pressure) pulse propagates downstream through the drilling mud from point 145.

The pressure pulse affects the pressure at jet nozzles in bit 30. When valve 54 is subsequently closed, a water hammer is generated upstream from valve 54. When the water hammer reaches point 145 mud is no longer diverted toward valve 54 and all of the mud Mowing in the upstream pompon o- condui 57 moist be a-ried downstream from poin' by conduit 57. mbe pressure a' poin' 145 Increases until the mud flowing a_ locations downstream 'ram, point 145 is accelerated. The resulting pressure pulse propagates downstream to affect the pressure at jet nozzles in bit 30.

2] Figure 5A shows a drill rig including a SAP generator 135 in which valve 54 and valve controller 55 are provided by an interrupter mechanism 120. interrupter mechanism 120 can be used to advantage in any o- the SAP generators described above. Figures oB and 5C are more defog- ' ed views o_ interrupter me-har.ism 120.

[00431 Interrup er mechanism 120 comprises a valve member 127 which bears against a valve seat 127A. Valve member is biassed into a -losed position by a spring 128. An air bladder 129 contains compressed air (which can be supplied through a port 125). Air bladder 129 applies forces to valve member 127 which tend to move valve member 127 into an open position wherein drilling mud can flow from an inlet chamber 122 between valve member 127 and valve seat 127A into an outlet chamber 123.

Drilling mud can enter inle chamber 122 through inlet passage 121. D''lling mud can leave outlet chamber 123 through outlet passage 124.

4] In operation, compressed air is admitted into bladder 12g until V2 lve member 127 Is moved in o its open position agains, the force exe-tea by spring 128. As soon as this occurs, drl'llug mud begins to flow from lnle' chamber 122 co outle_ chamber;23. As drill ng mud begins to flow through downstream choke valve 148 a nack-pressure is developed. This back pressure, combined with the forces exerted on valve member 127 by flowing fluid cause valve member 127 to move into its closed position. The closure of -a've member 127 causes a water hamme' pulse to propaga e upstream from input chamber 121. Valve member 127 is maintained in its closed position by the pressure pulse (and underlying static pressure). When the pressures pulse reaches main condui_ 57, or another place There luld can -loo- to relieve pressure, G negative pu se propagates bar]; toward lnerrupe mecrlanlsm 120. Upon arriv21 o- the negati-Te pulse, valve member 127 is pulled open and the cycle repeats itself.

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5] An advantage of interrupter mechanism 120 is the it can be constructed in a robust manner and the frequency of gene'-aed pulses can be easily and continuously changed. The operation o_ mechanism 120 can be adjusted by varying the air pressure in bladder 129 and varying the settings of downs'ream choke valve 148 and valve 48.

6] An accumulator 146 may be provided upstream -ram interrupter mechanism 120 to increase the du-aion of acoustic pulses. In general this is non required and has the disadvantage of reducing the intensive of the acous ic pulses propagated cow! the drill string.

7] in the foregoing embodiments of the invention, intense acoustic pulses are generated at the sur ace by a SAP generator. The pulses are lntrodu-=d into the drilling mud which is flowin down the drill string. The pulses propagate down 2: the d111 string to the bit. At the bit the pulses cause variations in the mud -low which can increase the e--icienov or the drilling operation. '"he intense acoustic pulses (positive and/or negative) can also be used to actuate downhole cools. The tools can be Of simple rebus_ construction. One class a- too s the_ may be actuated by acoustic pulses according to the lnver._ion ncluces tools which lmpar mechanical vibration to tne drill cit.

Such tools may suddenly force the drill bi_ downwardly upon the arrival of a pulse a, the tool. In the alternative, such tools may ii-4 a lower portion of the dr ll

string slightly in response to the zrriva or z pulse and then drop 4-he lower portion o- the d_ili string after the pulse has passed. Other types of Doris such as drilling jars may also be actuated be- the acoustic pulses of the invention.

8] Figure 6 is a schematic vies- o_ a rotary drill-ng apparatus which includes multiple piston telescopi- tool 66 mounted in the drill string above di2i bit 30. Pulses qene_ated by SAD generator 35 are conveyed down through the c l- string as described above. When the pulses reason multiple piston telescopic Tool 66 the tool ens sliabtly-, thereby accelerating the drill bit into the Formation being drilled. This embodiment of the invention can significantly vibrate the entire dril_ swing 67, thus reducing friction between dri'' s ring 67 and well bore 68. The vibration o dril bit 30 also enhance percussive action o_ drill b-al the bottom. of hole 34, resulting in faster drilling and lower torque requirements.

9] Figures 7 and 8 show z longitudinal sectional view o- a multiple piston telescopic tool 66 _r normal and extended positions respec_ very.

Too 66 -s coupled to a bottom end of a section of one dr -- -l'a 28 v__ a coupe no which, or example comprises a convenional hreaded coupling gS. Tool 66 includes a ram 69 which is coupled to drill bit 30 an a connection 70. Connection 70 may be a conventional threaded coupling. Ram 69 bears splices 96 and is received within a female-splined member 89 as shown in Figures 8 and 9. Splines 96 provide a torque coupling between female spliced member 89 and ram 69. Ram 6g can therer-ore slide longitudinally within the body or tool 66 without interrupting the transmission of rotational motion to drill bit 30. A top end o ram 69 is coupled to a pair of pistons 72, 74. Ram 69 and pistons 72 and 74 can move longitudinally in tool 66 as a unit.

The arrival at tool 66 of a pressure pulse propagating through the drilling mud in bore 79 forces pistons 72 and 74 downwardly. Thisr in turn, causes ram 69 to move from the norma: position shown in Figure 7 to fine extended position shown. n Figure 8.

0] In the illustrated tool So each or pistons 72 and 74 is slidably disposed within a hous ng.

Piston 72 is disposed within housing 90. Piston 74 is disposed within a housing 91. Housing 90 is coupled to housing 91 by a suitable coupling, such as threaded coupling 92. Housing 91 is coupled to a top sub 93 at a suitable coupling, such as threaded coupling 94. Housing 90 is coupled to female-spllned member 89 which receives ram 69 b\ a suitable couple ng such as a threaded coupling 91A.

1] Each pison is locaed beween a pair o cavities. Cavities 77 and 78 are upwardly adjacent to pistons 72 and 74 respectively. Cavities 77 and 78 are each in fluid communication with bore 79. In the illustrated embodiment apertures 81 and 82 are provided for this purpose. Cavities 83 and 84 are downwardly adjacent co pistons 72 and 74 respectively. Cavities 83 and 84 are each in fluid communication with the well bore 31 outside of tool 66. In the illustrated embodiment apertures 85 and 86 are provided for this purpose.

[0052; A cavity, 76 is also defined between the upper end of ram 6 and housing 90. This cavity is in Livid communication with bore 79, Bob example by way of apertures 80. Shaft seals 87 and piston seals 88 seal cavities 76, 77 and 78.

[0053lThe number o_ pistons may be varied. One or more pistons mall be used. Preferably two or more pistons are provided. An additional piston may be added simp'v by, coupling a piston like piston 72 between pistons 72 and 74 and a housing 'ike housing 91 between housings 91 and 92.

[0054J Figure 7 shows multiple piston telescopic tool 66 when no acoustic pressure pulse is presen and tool 66 is in its closed position. When a pressure pulse propagating down bore 79 reaches area 97, the Pressure adrilling mud in area g7 is suddenly increased. This causes drllllng mud co be forced into cavities 76, 77 and 78 via apertures - is - 80, 81 and 82 respectively. The increased pressure witrln cavities 76, 77 and 78 acting or, projected piston areas results in an axal Force or. ram. 6g.

Ah s force drives ram 69, and drill bit 30, into the bottom of hole surface 4. For example, a pressure pulse or 1, 500 psi acting on total area of in: will produce an axial force o- -2Q,OOO lbs.

This axial force will cause drill bit 30 to be thrus' against the bottom of hole 34, while reaction to this axial orce will lift the part o the drill string situated above multiple piston telescopic _ool 66. Relative telescopic movement is indicated by "E" on Figure 8. When the pressure pulse has passed the weight of the drill s ring above multiple piston telescopic tool 66 wilt cause too' 66 to collapse back into its normal position and thereby _ osing gap E. The dropping do ll s ring will also deliver addi_i Oral 'impact forces applied to dr ll hi- 3G.

[OQ55] Figure lO is a schematic view o G drilling rig according to an alternative embodiment o- this nvention. In the apparatus of Figure lo, high pressure pulses generated at SAP generator 35 are conveyed down the drill string through a mul iple piston telescopic too' 98, mounted above on_ or more lower dolly collars 99, and agendas bin sup 29 and droll bit 30. This embodimen- provides for vigorous axial vibration of the bottom part or the drill' string, allowing in some instances to drill percuss velv w thou need To_ G classical drill bi_ 30.

6] Figures 11 and 12 show a longitudinal sectional view of a multiple piston telescopic tool 98. A bottom part of tool 98, identified by "L", is j similar to the multiple piston telescopic tool 66 r shown in Figures 7 and 8, except that: bottom part L is adapted to be coupled to a top section or a lower drill collar 9. In the illustrated embodiment, ram 69A in bottom part L comprises a male thread 100, which can be screwed to drill collar 9g.

cavities 76, 77 and 78 are in fluid communication w th outside well bore 31 instead of bore 79. In the illustrated embodiment, holes 101 are provided for this purpose.

cavities 83 and 8 are in Fluid communication with inside bore 79 instead of outside well bore 31. In the illustrated embodiment, holes 1C3 are provided for this purpose.

7] A top part of tool 98 comprises a spring housing 104, which is coupled Lo a third piston housing 114 via threaded connection 105. Piston 74 comprises a piston mandrel extension 106 which extends into spring housing 104. A spring is connected between spring housing 104 and mandrel extension 106. The spring has a very large spring constant. The spring is compressed whenever the piston mandrel e,.tension 106 moves longitudinally upwardly or downwardly inside spring housing 104.

In the isles ra ed embod meet, z stack o disk -.7- springs 107 is on mand,-e2 e>,enson 10o between.

washers 105A and 1095. Washer- lO9A abuts a step in the outside of mandrel extension 106. Washer lO9B abuts the bottom o- c cop sub 111 which is coupled to sprlog housing 104 v_= t:nAeaded connection 112.

[00581 Ram 69A and othe- Paris of the d-ll string below tool 98 are supported by a sarer7 nut 108.

Safest, nut 108 is locked in plac^- by a screw 110.

Tool 9R is coupled o the drill string at,ts top end via c threaded connection 113.

FOODS] Figure 12 shows multiple piston telescoclc tool 98 wner. the pressure- within bore 102 is at its IS low of- zero value. Figure 3 shows mul-iple piston telescopic tool 98 when a high pressure pulse- bar propaga'_c-d down.-he d---l s ring and is passing through no-e 102 of roof 98. The pressure pulse increases the pressure- or- drilling mud in bore 102 and c users d'il2_ng mug' to be forced into _aviies 83 and 84. This causes a fore_ to am on pistons 7o an^' 74 so as to drive the pistcr.s upwardly. When the pistons move upwardly the portion O' the drill string located below tool 98 Is also lifted upwal:7 and spring 107 is compressed. A_te'^ the effect of the pressu'= pulse has dissipated, loaded stack of disk springs 107 wil' dynamical!\' rescuer.

bottom part of tool 98 Lo its initial pos tion, _hus result ng in a slgnif cant percussive blow to bottom hole 34.

- 28 - roo603 For example, G pressure pulse of 1,500 pa mu2lplied by a combined piston area a- 50 ir.9 wll produce an ax.iGl listing force o 90,000 'es. In a lyrical drilling apparatus the weight or lower drill collars 99, and other elements (such as drill bit 30! located below mu_iple piston telescopic tool 98, is approximately 3,000 - 6,000 lbs. Spring 107 will therer-ore elastically absorb the resultant axial force and retu n bottom end of the drill string with such a forc- so as to produce extreme percussive blows to bottom hole 34. These percussive blows can enhance drilling penetration rates, particularly when the formation being drilled 's hard.

[00611 Figure 13 illustrates schematically anothe- simple tool -Rich mabe used to imcar' ibraion -G G drill bait. Too 200 comprises a spliced ram. 202 which is slidably disposed wi kiln a femGle-spiined peg 204. Ram 202 is coupled to.= drill big.. Female splinen' part 204 is coupled to the upper portion of the drill string. A diameter a- bore 79 is reduced at or in ram 202. Ram 202 thereby presents an upwardly facing surface 208.

3 When a pressure pulse propagating down bore 79 increases the pressure acting on surface 208 ram 202 (and the dr'2l bit) are hammered downwardly.

[00623 P,s will be apparent co those sI'lled in, the

art in the l-gin. of the oregolng disclosure, mar.

aleratior.s and modiicaions are possible in the - 09 - practice of -h-s invention without depar ins rom the spirit or scope thereof. For example:

While the foregoing description details the

generation of high intensity pulses by interrupting the flow of the drilling mud pressurized by mud pump 45 a separate pump could be used to provide flowing drilling mud for use in generating high pressure pulses.

While the flowing fluid medium which is used to generate high pressure pulses is described above as being drill ng mud, a separate circuit in which high pressure pulses are developer by creating water hammers in a different fluid medium, such as wate', could be used to generate high pressure pulses which are then coup' ed into the drill ng mud being pumped down drill string.

Other techniques could be used to- generating high pressure pulses wh ch are propagated down through the drill string. For example, z pistol. capable a_ being Ferry suddenly accelerated -ould be locate_ to transmit high intensity pulses into the flowing drilling mud 57. The piston could be on G very high energy electromechanical transduce', for e',amDle.

Other types of tool such as drl'iing jars may be constructed SO as to be operable by hick intensity pulses propagated from one surface according co the invention. - 30

3] A-cording-, the scope of the ten ion is o be construed in accordance with the s>stance = I' Ed his he lo' long be, 2 a.= .

Claims (27)

1. CLAIMS: 1. A method for underground drilling, the method comprising: a)

   generating high intensity pressure pulses at the surface of an area to be drilled; b) coupling the high intensity pressure pulses into drilling mud being pumped into a drill string so that the high intensity pressure pulses propagate down the drill string to an underground location; and, c) doing work at the underground location with the high intensity pressure pulses, wherein generating the high intensity pressure pulses comprises causing drilling mud to flow in a first conduit and suddenly and periodically interrupting the flow of drilling mud in the first conduit.
2. 2. The method of claim l wherein the work comprises causing a flow of drilling fluid through nozzles in a drill bit at the bottom of the drill string to fluctuate.
3. 3. The method of claim l wherein the work comprises operating a downhole tool.
4. 4. The method of claim 3 wherein operating the downhole tool comprises forcing a portion of the drill string which includes a drill bit suddenly downwardly.
5. 5. The method of claim 3 wherein operating the downhole tool comprises lifting a portion of the drill string which includes a drill bit upwardly and compressing a spring.
6. 6. The method of claim 1 wherein causing drilling mud to flow in the first conduit comprises diverting a portion of a main flow of drilling mud from a mud pump to the drill string into the first conduit.
7. 7. The method of claim 6 comprising returning mud which has flowed through the first conduit to a mud tank.
8. 8. The method of claim 6 comprising providing a point at which a hydrostatic pressure of drilling mud flowing toward a drill string in a main conduit is reduced and introducing mud which has flowed through the first conduit into the main conduit at the point of reduced pressure.
9. 9. The method of claim 8 wherein providing the point at which hydrostatic pressure is reduced comprises providing a jet pump and causing drilling mud flowing in the main conduit to pass through the jet pump.
10. 10. The method of any of claims 1 to 9 practiced on a drilling rig having a drill string suspended from a swivel and a flexible hose carrying drilling mud into the swivel for passage down the drill string and coupling the high intensity pressure pulses into drilling mud being pumped into a drill string is performed upstream from the flexible hose.
11. The method of any of claims 1 to 9 practiced on a JO drilling rig having a drill string suspended from a swivel and a flexible hose carrying drilling mud into the swivel for passage down the drill string and coupling the high intensity pressure pulses into drilling mud being pumped into a drill string is ]5 performed downstream from the swivel.
12. 12. A method for underground drilling, the method comprising: a) generating high intensity pressure pulses at the surface of an area to be drilled; b) coupling the high intensity pressure pulses into drilling mud being pumped into a drill string; c) allowing the high intensity pressure pulses to propagate down the drill string to an underground location; and, c) allowing the high intensity pressure pulses to do
13. 13. The method of claim 12 wherein the work comprises causing a flow of drilling fluid through nozzles in a drill bit at the bottom of the drill string to fluctuate. s
14. 14. The method of claim 12 wherein the work comprises operating a down hole tool.
15. 15. The method of claim 14 wherein operating the downhole lO tool comprises forcing a portion of the drill string which includes the drill bit suddenly downwardly.
16. 16. The method of claim 14 wherein operating the downhole tool comprises lifting a portion of the drill string IS which includes the drill bit upwardly and compressing a spring.
17. 17. The method of any one of claims 12 to 16 wherein generating the high intensity pressure pulses comprises causing drilling mud to flow in a conduit and suddenly and periodically interrupting the flow of drilling mud in the conduit.
18. 18. The method of claim 17 wherein causing drilling mud to flow in a conduit comprises diverting a portion of a main flow of drilling mud from a mud pump to the drill string into the conduit.
19. 19. The method of claim 18 comprising returning mud which has flowed through the conduit to a mud tank.
20. 20. The method of claim 18 comprising providing a point at which a hydrostatic pressure of drilling mud flowing toward a drill string in a main conduit is reduced and introducing mud which has flowed through the conduit into the main conduit at the point of reduced pressure.

    lo
21. 21. The method of claim 20 wherein providing a point at which a hydrostatic pressure of drilling mud flowing toward a drill string in a main conduit is reduced comprises providing a jet pump and causing drilling mud flowing in the main conduit to pass through the jet pump.
22. 22. The method of any of claims 12 to 21 practiced on a drilling rig having a drill string suspended from a swivel and a flexible hose carrying drilling mud into the swivel for passage down the drill string and coupling the high intensity pressure pulses into drilling mud being pumped into a drill string is performed upstream from the flexible hose.
23. 23. The method of any of claims 12 to 21 practiced on a drilling rig having a drill string suspended from a swivel and a flexible hose carrying drilling mud into the swivel for passage down the drill string and coupling the high intensity pressure pulses into drilling mud being pumped into a drill string is performed downstream from the swivel.
24. 24. Underground drilling apparatus comprising: a) a drill string; b) a mud pump; c) a main conduit carrying mud pumped by the mud pump toward the drill string; d) pulse generator means located at the surface for generating high intensity pressure pulses; e) pulse transmission means for coupling high intensity pressure pulses generated by the pulse generator means into mud being pumped toward the drill string.
25. 25. A downhole tool described herein.
26. 26. A method practiced in using a downhole tool as described herein.
27. 27. Apparatus for underground drilling as described herein.