US2632631A - Drilling mud flow system - Google Patents

Description

March 24, 1953 GRIFFIN AL 2,632,631

DRILLING MUD FLOW SYSTEM Filed May 6, 1949 5 Sheets-Sheet 1 '7 I I nLocx noon II is "as: SWIVEL sumo m F I G I KELLY JOIN nauw RR:

32 3 v sTeAu TO PUMPS 22 22 I RILL PIPE PUMPS common. 7 b 23 ROTARY Y 32b I nun Pll' 25 I 5 L Q v nun RELEASE VALVE ETURN j g PIPE 24 sane snnxzn IUD- RETURN DITOH Harold E Griffin,

Robert R. Crooksfon, INVENTORJ.

AGENT March 24, 1953 H. F. GRIFFIN ETAL DRILLING MUD FLOW SYSTEM Filed. May 6, 1949 3 Sheets-Sheet 2 DELAY CONTROL HUD RELEASE VALVE IDLING SPEED REGULATOR STEAM TO PUIPS AIR SUPPLY DUAL CONTROLLER OELAY CONTROL FIG.

AIR SUPPLY IU'D RELEASE z u z a a K G u u c E m u 5\ w R E L n m \l 8 R N T .T 8 M U c U o M ,v 3 X E 3 MASTER IDLING SPEED DELAY CONTROL R w l lu 6 E R 7 4 FIG. 3.

PUIP SPEED REGULATOR m my "M f I 0 R mm a .D H Ov R STEAI AGENT March 24, 1953 H. F. GRIFFIN ETAL 2,632,631

DRILLINGMUD FLOW SYSTEM Filed may 6, 1949 J "s Sheets-Sheet :5

FIG. 5.

. Harold E Griffin,

Robert. R. Crooksfoh;

INVENTORS.

AGENT.

Patented Mar. 24, 195 3 UNITED STATES PATENT OFFICE DRILLING MUD FLOW SYSTEM Harold F. Grifiin and Robert R. Crookston, Houston, Tex., assignors, by mesne assignments, to Standard Oil Development Company, Elizabeth, N. J., a corporation of Delaware Application May 6, 1949, Serial No. 91,708

4 Claims.

The present invention relates to earth boring operations. More particularly the invention is directed to a method and to apparatus for con.- trolling flow of a fluid drilling mud during the drilling of deep wells.

As the drilling of Wells has developed to deeper and deeper horizons. beneath the surface f the earth, it has become more more important that the drill operator should have complete control of the pumpi :of drilling fluid downward into the borehole.

In the course of drilling operations, it is often necessary to stop circulation of drilling mud in order to change .drill bits, to lengthen the drill stem, or to make measurements in the borehole. Because the pump pressures involved are'quite high, sometimes reaching several thousand pounds per square inch, and because of the abrasive nature of the drilling mud, it has here.- tofore been the practice to stop circulation of mud by shutting on the driving power for the pumps thereby .completely stopping the pumps and mud circulation.

While this method of stopping circulation has been almost universally employed in rotary drilling operations, it has not been entirely satisfactory primarily for the reason that the mud pumps oftenlose their prime and fail to regain suction when restarted. Occasionally when suction is suddenly regained, the pumps build up tremendous pressures which may blow out protective relief valves or may even break pump lines or the pump mechanism-itself. Regardless of causes and eiiects, experience has shown that much time which could "be spent in advancing the drill bit into the earth is lost as a result of the practice of stopping and starting mud pumps.

We have now devised a method and apparatus whereby this needless loss of time has been greatly reduced. Briefly stated, the method of our invention contemplates continual driving of the mud pumps so that drilling fluid is continually pumped therethrough. During normal drilling operations "when it is desirable to inject drilling mud into the well bore, the mud pumps are operated at'a normal speed and the drilling mud is forced under pressure through a conventional feed line, stand pipe, and drill stem, and thence upwardlyt h-roughthe well bore andback to the mudreservoir. Whenit becomesnecessary to stop injection of drilling mud into the well,

the speed of operation of the 'mud pumps isfirst reduced from normal operating speed to a low idling speed such that the pressure head developed. thereby may be insufficient to overcome the hydraulic head .of fluid in the standpipe. Thereafter a release valve is opened permitting the mud from the pump outlet or mud feed line t9 r turn 1i ec.t-1y to the mud reservoir through a byp s n ath wh ch e c de th dr em n 611 QQY 1 a t r-dam h the practice o our me i n. h mu um s ar no st p d e e t'fcr re a o e vi ng o t PIJI IPS- Fu t e o e. fl id ass om th pumps throu h t e fe d l ne a d standp n the ce to t e r l s em s n ver blocke ff a b the o in o a val e- When it is d s red to resume mod circulation to the orehole, the mu release valve is closed while the pumps are opera ine at i in spe d; the speed of the pumps and the consequent pressure head developed thereby, is then increased to a desired operating value.

Whi e the method of our invention may be practiced by manual manipulation of apparatus elements in proper sequence, we prefer to conduct certain ofv the steps. automatically and preferably by r mote control. Accordingly, our invention also includes a combination of apparatus elements whereby the circulationof fluid mud into a borehole may be started or stopped from 'a single location, such as from the derrick door which may he remote from the mud pumps.

The method and apparatus. of our invention may best be understood by reference to the accompanying drawinginwhich:

Figure 1 is a perspective View showing the location of various. apparatus elements which may be employed in practicing one embodiment of our invention; Figure 1 is'not, drawn to scale and no attempt has been made to show all ofthe connecting conduits employed in the control mechanism of our invention. Figure 1 isintended to illustrate an appropriate location of major control elements shown in Figures 2 and 3 Figure 2: is a diagrammatic flow sheet of one embodiment of apparatus, includingconnecting gonduits, suitable for the practice of pur'i'nvenion;

Figure 3 is. a diagrammatic flow sheet of another embodiment of apparatus providing flexible control of a plurality of pumps in accordance with ourinvention;

Figure 4 is an elevation view, partly in section, of a pneumatically operated mud release valve adapted to be used in the practice ofour inven tiongand Figure 5 is an elevation view, partlyin section, of another mud release valve which may be opened pneumatically and be caused to close by springac-tion' In the accompanying drawings and in the following description, it is assumed for purposes of illustration that the mud pumps are steam driven reciprocating pumps. However it will b e apparent toworkers skilled in the art that the method of our inventionmaybe readilyapplied to. other types ofpumpsand to other types of power for actuating these pumps-byminor modi 3 ficationor substitution of equivalent control elements suited to the types of pumps and power.

Referring first to Figure 1, the numeral |I designates a conventional well drilling derrick structure having a floor I2. The floor l2, in usual practice, is generally elevated about 10 or 15 feet above the surface of the earth. Centrally located in the floor of the derrick is a rotary table l3 which is employed to rotate a tubular kelly joint I i upon the lower end of which is affixed a suitable length of tubular drill pipe l5. Kelly joint I4 and drill pipe I5 collectively may be said to constitute a drill stem on the lower end of which is afiixed a conventional rotary drill bit (not shown).

Suspended by cables |6 from a crown block at the top of derrick H is a travelling block carrying an elevator hook H3 and a conventional swivel joint I9. Swivel joint I9 is connected to kelly l4 and provides means whereby drilling fluid introduced therein through flexible mud hose 2!) may be forced downward through the drill stem. Mud hose 29 is connected to the upper end of a standpipe 2| which generally is supported by one leg of derrick ll. In conventional drilling practice standpipe 2| extends in upright direction from floor |2 to approximately one-half the height of the derrick. A mud feed pipe 22 is connected to the bottom end of standpipe 2| and is, generally, manifolded to the outlets of a plurality of mud pumps 23, although in some installations pipe 22 may be connected to the outlet of a single pump. Pump means 23 are commonly located at an elevation below the lower end of standpipe 2| and adjacent a mud reservoir or pit 24 which may be an earthen pit arranged at any convenientlocation near derrick II. In marine drilling operations, mud reservoir 24 may be a tank suitably arranged on a barge or other support adjacent the derrick, and mud feed pipe 22, in this instance, may include a suitable flexible section.

Pump means 23 are provided with suction lines 25, which may be manifolded as desired, connecting the inlet ports thereof with mud reservoir 24. Each pump is preferably provided with actuating 'means such as, for example, a reciprocating steampiston or a suitable equivalent. Accordingly, in Figure 1, a steam line 26, which connects at one end to a steam generator (not shown), is indicated as connected to pump means 23 through branch lines 25a and 26b. It will be understood that this showing represents connection of the steam lines to suitable means for actuating the respective pumps.

In the conventional operation of a well drilling rig, as thus far described with reference to Figure 1, drilling mud is withdrawn from reservoir 24 by pump means 23 and is forced thereby through mud feed pipe 22, standpipe 2|, mud hose 20, swivel joint l9, kelly l4 and drill pipe l5 into the earth borehole. After passing out of the drill bit on the lower end of the drill pipe, the mud passes upward through the borehole into surface casing (not shown) beneath the derrick floor and ultimately passes into mud return pipe 21 from whence it is discharged into a shale shaker 28 or other means for separating drill cuttings from the mud. The recovered mud is then returned to reservoir 24 through a suitable conduit, such as mud ditch 29.

The method and apparatus thus far described is old and conventional in the art. In accordance with our invention, we provide a conduit 31 ich may branch from feed pipe 22 at any 4 unobstructed position between theoutlet of pump means 23 and the base of standpipe 2|. Conduit 33 is preferably arranged to spill drilling fluid into reservoir 24. At any desired position in conduit 39, and conveniently on the outer end thereof, we provide a mud release valve 3 However, we prefer not to block fluid communication between feed line 22 and standpipe 2|, as by the installation of a blocking valve, at any position between the outlets of pump means 23 and standpipe 2|.

In accordance with our invention, we also provide one or more throttling valves 32a and 32b either in steam header 26 or in branch lines 26a and 2622. When pump means 23 are other than steam operated, it will be apparent that throttling valves 32a and 3211 will be replaced by other equivalent means adapted for use with the particular type of power employed and capable of throttling the speed of pumps 23. Although valves 3|, 32a and 32b. may be manually controlled valves, in a preferred embodiment of our invention, these valves are remotely controllable in roper sequence from a single station such as by controller 33 arranged conveniently adjacent other drilling controls above the derrick floor. Suitably, controller 33 may operate valves 3|, 32a and 32b by varying fluid pressures applied to actuating mechanisms thereof. If desired, however, controller 33 may operate valves 3|, 32a and 32b in proper sequence by a system of levers or by electrical actuating means.

When it is not desired to employ the remote control feature of our invention, valve 3| and throttling means 32a and 32b are individually controlled by manual adjustment. During normal operations when drilling mud is injected into the well bore, valve 3| is fully closed and throttling means 32a and 32b are each adjusted so that pumps 23 operate at a normal speed and develop a pressure sufficient to force drilling mud through the conventional circuit hereinbefore described. When it is desired to stop the injection of mud into the well bore, throttling means 32a and 3211 are each manually closed far enough to reduce the speed of operation of pumps 23 to a low idling speed without stopping them. Thereafter, valve 3| is manually opened thereby permitting the mud passing through the pumps to return directly back to mud pit 34. If kelly i4 is now disconnected from drill pipe |5, as, for example, to permit insertion of an additional stand of drill pipe, it will be found that drilling mud standing in kelly l4 will syphon back to reservoir 24 through stand pipe 2|, feed line 22, by-pass line 30 and valve 3|.

Throttling means 32a. and 32b are maintained at the idling speed adjustment described above and valve 3| is maintained open at all times when it is not desired to inject mud into the borehole. When it becomes desirable to resume injection of mud into the well bore, valve 3| is first manually closed and throttling means 32a and 32b are thereafter opened until pumps 23 are returned to normal operating speed.

Turning now to Figure 2, a combination of pneumatic elements adapted to control the operation of valves 3| and 320. will be described. In Figure 2, the controller 33 may be a dual-control, air valve of a type commonly employed in the actuation of the air brakes of vehicles. Details of the structure of controller 33 will not be described herein since this structure is well known in the pneumatic controller art and is typically illustrated by the Type B Flexair pressure congas in --a pipe 39.

I into pipe 39.

,trol valve manufactured by Westinghouse Air Brake Company of Wilmerding, Pennsylvania. Insubstanoe, controller 33 comprises two independently operated piston valves adapted to regulate the pressure of a compressed gas, such as compressed air supplied from a source (not shown) through pipe 34, and to deliver a constant pressure into either pipe 35 or "pipe 35. When the handle of controller '33 is in a position intermediate between the positions designated 33 and 33b, pneumatic pressure in pipes '35 and 36 is exhausted to the atmosphere and supply pipe 34 is blocked. On the other hand, when the handle of controller 33 is moved toward a position indicated by either 33a or 331), a controlledpressure is delivered either into pipe 35 or pipe 36, respectively. While conducting operations in accordance with our method, controller 33 is rarely operated in the intermediate position but is set in this position only when it is desired to stop completely the operation of pump means 23. I

The pipe 35 is-connected to deliver pneumatic pressure tothe diaphragm chamber of a diaphragm actuated, spring return, four-way valve 31. The structure of valve '31 is well known in the art and may be illustrated by the four-way, single diaphragm operated valve manufactured "by'Valvair Corp. of Akron, Ohio. Valve 31 is arranged so that, when pressure is applied to the diaphragm chamber through pipe 35, the diavalve to permit transmission of compressed gas from pipe 34 into a pipe 38 and simultaneously to exhaust to the atmosphere any compressed When pressure is removed from the diaphragm chamber of valve 37, the

spring return thereof moves the valve element 'sothat pressure in pipe 38 is vented to theat- -mosphere and pressure in pipe 34 is transmitted In accordance with a preferred form of our invention pipes 38 and 39 are connected to "cylinders on opposite sides'of a piston of mudrelease valve 3| in a manner which will -betdescribed more fully in connection with Figure Application of positivepneumatic pressure in pipe 313 causes valve 3| to open while applicationof pressure in pipe 39 causes valve :31 to close. Sothat a predetermined delay between the pneumatic actuation of diaphragm valve'3l andthe opening of valve 3| may'occur, aspeed "control valve 4|] is preferably "arranged in pipe 38 between valves 3| and 31. "Speed control valve may be a conventional speed controlcomprising needle and check valves offering *resistance to flow inthe'direction from valve 31 "to 'valve 3 lbutlittle-or no' resistance toflow in theopposite direction.

lesshown in the drawing, pipe 35 is-also cona conventional "pressure reducing valve capable of maintaining a, predetermined fixedpressure mammal between the s'upply and delivery p'res'sures. Preferably th fpressure fdifierential 'snou1d betconvenientlyadjustableiwithinzdesired limits. Regulator 44 is adjusted to reduce'the 31. Figure Z and serves a "function similar thereto. :Pipes 38 and 39 'connectvalve "3'1 to'mud release were . 6 pneumatic pressure to such an extent that valve 32a will open only part way when full pneumatic pressure is delivered into pipe 35.

It is to be noted that, with the operating handle of controller 33 in the position designated 33a, pipe 36 is vented to the atmosphere. In this position, the piston or plunger of dual check valve 42 takes up a position to prevent flow of compressed gas from pipe 4| to pipe 33.

When the handle of controller 33 is moved from position 33a to position 3319, pressures in pipes 35 and M are vented to the atmosphere and substantially the full pneumatic pressure from line 32 may be delivered to the diaphragm chamber of valve 32a thereby fully opening this valve and permitting pumping means 23 to operate at full speed. A speed control valve 45, substantially identical to valve 43, is preferably included in pipe 33 between controller 33 and check valv 42 in order to delay the opening of valve 32a subsequent toactuation'of valve 3|.

Figure 3 illustrates a preferred combination-of elements particularly adapted to "control the flow of drilling fluid when pumping means 23 comprises two or more pumps "operating either in parallel or in series. In the embodiment shown in Figure 3, the dual controller '33 of Figure 2 is replaced by a similar controller 33' having a single pneumatic valve which is actuated by movement of the control handle from the position '33a toward the position indicated by the broken line .33'b. Compressed gas --is supplied iro'ma source (not shown) through pipe'34. The pressure of the gas passing through controller 33' 'islregulated in accordance with movement of the control handle and is transmitted through pipe 35 to the diaphragm chamber of 'four way valve Valvetlmay be .identical'to the valve 31 of Figure '2. However, pipe 33 does not include the speed controlvalve til. 'Furthermorepipe 38 is "branched and connects "to a pipe 46 which leads "to 'on'e'side of dual checkvalve 42. A'speed controlvalve '45 and a regulating "relief 'valve 41 are arranged in line "43 'to provide adjustable delay action and over-all .speedregulation,respectively.

The mechanism of regulating .valve 47 is similar to that "of controller 33' but, 'for operating con- 50 .ing lever, valve 41 preferably has a rotating handle venience, instead of having a toggle-type actuatadapted to be setandlockedin a desire'd'position. As will be seen from Figure 3, the pipe 4| branches from pipe ,35, delivers into 'dual check valve 32 and from thence intoipipe 43. Pipe s3 is preferably branched int-o a'plurality of pipes 43a, 431), etc. which connect tothe diaphragm chambers of valves 32a, 3212, etc. arranged in steam lines 23a, 26b, etc. So thatthespeed of each of the plurality of pumps'in pump means 23"may lee-individually adjusted, regulating valves 48a and llfi'bare preferably installed in pipes 43a and 431), respectively. Valves 48a and 18b may be substantially identical to valve 4'1.

In a practical installation of the' combination of apparatus'el'ements shown in'Figure'3, diaphragmvalve 3?, dual check valve "42, speed control valve "65, and regulating valve 41 -'may'be conveniently installed upona' control board along with control1er33'. Mudrelease valve3| "may I be installed at some distancefrom controller '33 and preferably adjacent mud reservoir :24. like- "'wise, diaphragm valves 32 az and (32b .-and--individual pump regulating valves 48a and' z 4Bb-. are preferably installed adjacent pump means 23 .chamber of valve which may be a considerable distance from controller 33. Under these conditions, it is desirable to provide on the aforementioned control board a plurality of block valves 45a and 49b in pipes 43a and 4317, respectively, so that any one of the plurality of pumps may be put out of service as desired. Also, since pipes 43a and 431) may be of considerable length, it is desirable that there be installed in each of these lines adjacent the diaphragm chambers of each of valves 32a and 32?) quick release valves such as 50a and 501). Quick release valves 50a and 50b are well known in the pneumatic control art and may consist of a diaphragm so arranged that, when pneumatic pressure is applied to one side of the diaphragm, an exhaust port is closed before compressed gas is delivered to a chamber, such as the diaphragm 32a. When the pneumatic pressure applied to the diaphragm of the quick release valve is reduced below a predetermined value, the diaphragm is pressed by a spring to close the supply port and open an exhaust passage from the aforementioned chamber to the atmosphere. Thus, the chamber may be more quickly exhausted than it would be if the exhaust path for the chamber were through a long length of pipe. In the embodiment of Figure 3, valves 50a and 501) permit valves 32a and 32b to close quickly in response to a reduction in supply pressure caused by regulation of valve 33 or valve 41. Operation of the system illustrated in Figure 3 is as follows:

When it is desired to stop circulation of mud to standpipe 2|, the handle of controller 33 is moved from the normal operating position 33'b to the position 33%. Pneumatic pressure in the pipes 35 and 4| is thereby vented to the atmosphere causing the mechanism of valve 31 to move into a position whereby full supply pressure from pipe 34 is transmitted into pipes 38 and 46. The pressure in pipe 46 is transmitted through speed control 45 to idling speed regulator 41, thence through dual check valve 42 to pipe 43 and subsequently to the diaphragm chambers of valves 2a and 32b. Since regulator 41 is used as a master contro1 of pump idling speed, the pneumatic pressure is reduced in this valve and, because of the presence of quick-release valves 50a and 56b in lines 43a and 43b, diaphragm valves 32a and 32b quickly operate to supply only sulficient steam to the pumps to operate them at an idling speed.

Substantially simultaneously with the abovedescribed operations, pneumatic pressure in pipe 39 is vented to the atmosphere through valve 31 and pressure in pipe 38 is transmitted to valve 3| causing the latter to open and by-pass mud from'the outlet of pump means 23 to reservoir 24.

When it is desired to resume circulation of mud to standpipe 2|, the handle of controller 33' is moved from the position 33a toward the position 33b. Such movement causes pneumatic pressure to be admitted into pipes 35 and 4| and the diaand 32b.

8 As indicated hereinbefore, valves 48a and 48b are preferably employed only to regulate the speed or load of one pump relative to another. Accordingly, when valve 3| is closed, the speed of operation of pump means 23 and the pressure head developed thereby are normally controlled by the amount of pressure transmitted through valve 33'. and this pressure, in turn, is a function of the movement of the control lever in the directionfrom position 33a toward position 33'b.

Referring now to Figure 4, a preferred embodiment of the mud release valve, designated generally by the numeral 3| and mentioned in connection with the description of Figures 1, 2, and 3, is shown. The numeral 5| designates a pipe nipple having an integral flanged end 52. Nipple 5| is adapted to be affixed at the end of the pipe 33 (Figure 1). Abutting against flange 52 is a second flange 53 which is a part of tubular valve body 54. Flange 53 may be held in abutment against flange 52 by stud bolts 55. Valve body 54 includes a central wall member 56 which divides body 54 into a mud chamber 51 and a pneumatic cylinder 58. The outer end of cylinder 58 is closed by a cap member 59 screw threadedly engaged over the outer end of body 54. A plurality of mud ports 66 is arranged in the walls of chamber 51 between flange 53 and central wall 56. The area of ports 60 is made as large as possible so that resistance to flow of fluid mud therethrough will be a minimum.

Passing centrally through wall member 56 and co-axially with respect to chamber 51 and cylinder 58 is an opening 6| which serves as a guide or bearing for a longitudinally slidable shaft 62. Integral with one end of shaft 62 and internally of chamber 51 is piston-like member 63. Piston 63 is longitudinally movable throughout the length of mud chamber 51 and is adapted to close completely the central bore of nipple 5| by contact with suitable sealing means such as a rubber O ring 64 inserted in a suitable concentric groove 65. On the end of shaft 62 opposite to piston 63 is a second piston 66 disposed in cylinder 58. Piston 66 is secured to shaft 62 by means of a screw-threaded nut 61 or other suitable means.

To prevent leakage of pneumatic fluid around piston 66, the latter is preferably provided with one or more piston rings, such as rubber 0 rings 68 seated in ring groove 69. Similarly, leakage of pneumatic fluid around shaft 62 is prevented by one or more similar rings 10 seated in grooves 1| cut in the walls of passage 6|.

An opening 12, communicating with the pipe 38 of Figures 2 and 3, is provided for introduction of pneumatic fluid between wall member 56 and piston 66. Also a passage 13 extends throughout the length of shaft 62 so that fluid mud may enter chamber 58 behind piston 66.

In chamber 58, between piston 66 and cap member 53, is a second piston 14 carried by solid shaft 15. Leakage of pneumatic fluid around piston 14 is prevented by one or more piston rings or rubber 0 ring 16 seated in grooves 11. Shaft 15 protrudes through a central opening 18 in cap member 59 and leakage of pneumatic fluid around the shaft is prevented by one or more sealing rings 19 seated in groove cut in the walls defining opening 18. An opening 8| through cap member 59 provides communication with the pipe 39 shown in Figures 2 and 3.

During the operations heretofore described in connection with Figures 2 and 3, pneumatic pressure applied to piston 66, through pipe 38 and opening 12, forces this piston to move toward 9 cap member 59 thereby pulling piston-like member 63 out of sealing relation with ring 64. Thereupon mud fluid is permitted to flow through nipple and out through openings 69. Upon exhausting pneumatic pressure from the portion of chamber 58 defined between wall 56 and piston 66, as by exhausting pneumatic fluid through line 38, the release of mud through openings 60 may be stopped by application of suflicient pneumatic pressure through line 39 and opening 8! to piston 14. Application of this pressure causes piston 14 to. move away from cap 59 and toward wall member 55. Piston 66, shaft 62 and member 63 move with piston 66 until member 63 is brought into sealing contact with ring 64 and the valve is thus closed. After the valve is closed and fluid pressure has built up within nipple 5|, pneumatic fluid may be exhausted through pipe 39 without permitting the valve to open since mud fluid pressure is transmitted through passage 13 into the portion of chamber 58 between pistons 66 and 14. However, when suflicient pneumatic pressure is again introduced through pipe 38, any mud fluid entrapped between pistons 66 and 14 flows back through passage 13 and permits the valve to open.

Turning now to Figure 5, a self-closing valve is shown which is somewhat similar to the valve described with reference to Figure 1. The valve shown in Figure 5 differs from that shown in Figure 4 in the respect that a spring 82 performs the basic function of piston 14. As will be seen from the drawing, one end of helical spring 82 bears against piston 66 and urges the latter toward wall member 56. The opposite end of spring 82 bears against a cap 59' which may be threadedly engaged on body member 54. Cap 59 contains no opening equivalent to the opening Bl shown in Figure 4. A tubular member 83, having openings 84, is screw threadedly engaged upon the end of shaft 62 in place of the nut 61 in order to hold piston 66 upon the shaft and also to serve as a guide for spring 82 and minimize nonhelical distortion thereof during, compression. Openings 84 permit mud fluid to enter chamber 58 between piston 66 and cap 59.

When a valve of the type shown in Figure 5 is employed in one of the systems described in connection with Figures 2 and 3, the systems may be simplified by omitting pipe 39 and by substituting a three-way valve in place of the four-way valve 31.

Although our invention has been described and illustrated by reference to specific embodiments thereof, it will be apparent to workers skilled in the art that various modifications and substitutions of equivalents may be made without departing from the scope and spirit of the appended claims.

We claim:

1. In a system for circulating fluid mud in earth boring operations including a mud reservoir, pump means having an inlet and an outlet and adapted. to pump fluid mud, driving means operatively connected to said pump for actuating the latter, means connecting the inlet of said pump to said reservoir, and a mud feed pipe connecting the outlet of said pump to the base of a standpipe elevated above the pump, the improvement which comprises, in combination, a conduit branched from said feed pipe and capable of discharging fluid mud from the outlet of said pump into said reservoina release valve in said conduit interposedbetween said feed pipe and said reservoir, throttling means associated with said driving means and adapted to control actuation of said pump, and a control means operatively connected to both said release valve and said throttling means for sequential operation thereof, said control means being adapted to close partially said throttling means and then to open fully said release valve and also being adapted to close fully said release valve and then to open said throttling means.

2. A system in accordance with claim 1 in which said release valve and said throttling means each include actuating means responsive to changes in pressure of a fluid and said control means includes a master valve for altering fluid pressures applied to said actuating means.

3. A system for controlling fluid mud circulation to a borehole in the earth comprising, in combination, a mud reservoir, a pump having an inlet and an outlet and adapted to pump said mud, driving means for driving said pump, throttling means for controlling the speed of said driving means, means for conducting mud from said reservoir into said pump, means including an elevated stand pipe and a mud feed pipe providing open fluid communication between said outlet and said stand pipe for conducting mud from the pump into the borehole, a conduit for discharging mud from said feed pipe into said reservoir, a release valve interposed in said conduit between said feed pipe and said reservoir, and a control means operatively connected to both said release valve and said throttling means for sequential operation thereof, said control means being adapted to cause partial closing of said throttling means and then full opening of said release valve and also to cause subsequent full closing of the release valve before opening the throttling means.

4. In the drilling of wells in the earth wherein drilling fluid is injected into a well bore from a pool of drilling fluid in a normal path of flow during selected periods of time and wherein injection of drilling fluid through said normal path of flow is interrupted during other periods of time, the method of continuing flow of drilling fluid which comprises injecting drilling fluid into the well bore at a selected rate of flow and returning the drilling fluid from the well bore to said pool during said selected period of time through the normal path of flow, substantially reducing the rate of flow of drilling fluid, establishing a path of flow for said drilling fluid separate from and excluding a major portion of the normal path of flow, and returning the drilling fluid at the reduced rate of flow to said pool through said separate path of flow during said otherperiods of time.

HAROLD F. GRIFFIN. ROBERT R. CROOKSTON.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Laufier et a1. July 16, 1940

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