US2879846A - Process and apparatus for preventing loss of drilling fluid - Google Patents

Description

March 31, 1959 Filed March 4, .1955

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A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID 6 Sheets-Sheet 1 Arden H. Dawson, Jr. INVENTOR.

BY MM 3% P ocEss AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID A. 'H. DAWSON, JR

March 31 1959 6 Sheets-Sheet ?2 Filed March 4, 1955 6 Sheets-Sheet 3 TL 7 w III! Fig 8 Arden H. Daws on, Jr.

March 31, 1959 A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID Filed March 4, 1955 March 31; 1959 A. H. DAWSON, JR 2,879,846

PRQCESSANI. APPARATUS FDR PREVENTING LOSS OF DRILLING FLUID 6 Sheets-Sheet 4 Filed March 4, 1955 Arden H. Dawson, Jr.

IN VEN TOR.

BY W-fin March 31, 1959 A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID 6 Sheets-Sheet 5 Filed March 4,' 1955 Arden H. Dawson, .lr.

uvmvrox.

BY on! March 31, 1959 A. H. DAwsoN, JR 2,879,846

. PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID v Filed March 4, 1955 6 Sheets-Sheet 6 i 'j Fig. /8 Fig.l6 5' 220 o 26 p242 46 o 48 262 -264 I o v 252- I ;22 ,4 220 224 i 2 1 255 254 Em 226 3 j i 450 Z 2 232 i GEE); 24a i 246 2 2 244 1 Z 1 v f o I 4 I 230 Q a o '26 -48 2 go 228 22a 44 a 2 7 Q o o 4 2 a 2 O Q /7 o A Fig. /9

, Arden H. Dawson, Jr. M INVENTOR.

l 3 3 BY @4052. min aw Em United States Patent PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID Arden H. Dawson, In, Texhoma, Okla.

Application March 4, 1955, Serial No. 492,174 19 Claims. (Cl. 166-23) This invention comprises novel and useful improvements in a process and apparatus for preventing loss of circulation of drilling fluids and more specifically relates to novel methods and apparatuses whereby lost circulation materials in the form of drilling mud additives may be mechanically introduced in relatively high concentrations directly at a region of a thief formation at which cirulation losses are occurring.

The present application comprises a continuation-inpart of my prior copending application, Serial No. 345,- 447, filed March 30, 1953, now US. Patent No. 2,815,- 190, issued December 3, 1957, and bearing the same title as that of the present application.

The general purpose of this invention is to provide apparatuses and methods whereby the sealing of a porous formation may be effected with as much precision and certainty, and with as little delay, as possible.

The principal object of this invention is to provide a method and apparatus whereby concentrations of drilling mud additives, and in particular, such concentrations which are in excess of those which are capable of being 'handled by conventional drilling fluid pumps, may be introduced into a well bore for sealing porous formations.

A further object of the invention is to provide a method and apparatus wherein the concentration of drilling mud additives in a drilling fluid, as delivered by conventional drilling fluid pumps into a mud circulation system,

may be greatly increased at a predetermined region of a thieving formation to effect, by the increased concentration, a more eflicient sealing action upon the porous formation.

Yet another purpose of the invention is to provide a process and apparatus in conformity with the foregoing objects wherein the concentration of a drilling mud additive or lost circulation material in a drilling fluid may 'be temperarily increased at a predetermined region of a well bore to effect a more efficient sealing of a porous or leaky formation therein.

A still further object is to provide an apparatus and method whereby slugs or plugs of lost circulation material, at various desired concentrations, may be formed and delivered to a formation by a conventional mud cir' culating system, and without any limit to the concentration of the lost circulation material being imposed by the elements of the mud circulatory system.

An additional important object of the invention is to provide a method and apparatus whereby a constant flow at a uniform rate of a given concentration of a drilling mud additive in a drilling mud may be introduced into the circulating systemand whereby, within the well bore, a quantity of the drilling mud additive may be concentrated and continuously or intermittently delivered in highly concentrated form to a predetermined portion of a well bore to seal porous formations therein.

A further primary object of the invention is to provide a process and apparatus whereby conventional drilling fluid pumps may be rendered eflective to deliver considice erably greater concentrations of drilling mud additives or lost circulation materials in a drilling fluid than had been heretofore possible.

Still further important objects of the invention are to provide apparatuses and methods whereby lost circulation material may be continuously supplied into the drilling fluid circulating system of a well by conventional mud circulating pumps therefor, and at a degree of concentration of the lost circulation material which is consistent with present practice, and yet wherein a predetermined but variably adjustable increase in the concentration of the lost circulation material may be obtained for discharge into the well bore at a selected location therein to more effectively seal a thief or porous formation by virtue of the controlled increase in the concentration or density of the lost circulation material. f

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

Figure 1 is a somewhat diagrammatic view, parts being broken away and shown in section, of the well bore showing an apparatus in accordance with the present invention applied thereto;

Figure 2 is an enlarged elevational view, parts being broken away and shown in vertical section, of a concentrating device for increasing the concentration of drilling mud additives in drilling mud;

Figure 3 is a vertical sectional detail view, taken upon upon an enlarged scale, substantially upon the plane indicated by the section line 4-4 of Figure 2;

Figure 5 is a view similar to Figure 2, but of a second embodiment of the mud additive concentrating and discharging device;

Figure 6 is a view similar to Figure 2 but showing a third embodiment of the concentrating device, a part thereof being broken away;

Figure 7 is a view similar to Figure 2, but showing another or fourth embodiment of a concentrating device, a part thereof being broken away;

Figure 8 is a view of the embodiment of Figure 7, but showing the same in a position for discharging a concentration of drilling mud additives;

Figure 9 is a view similar to Figure 2, but showing still another or fifthembodiment of a concentrating device, a part thereof being broken away;

Figures 10 and 11 are views similar to Figure 2, showing still further sixth and seventh embodiments of the concentrating device, parts thereof being broken away;

Figure 12 is a perspective view of the means for discharging concentrated lost circulation material from the concentrating devices of Figures 2, 5 and 6;

Figure 13 is a view similar to Figure 2 but showing an eighth embodiment of the concentrating device;

Figure 14 is a detail view taken in horizontal section substantially upon the plane indicated by the section line 14-14 of Figure 13;

Figure 15 is a fragmentary view in vertical section of a ninth embodiment of the concentrating device, being a slight modification of the structure of Figure 13;

Figure 16 is a view in vertical section of a tenth embodiment of the concentrating device in accordance with this invention; v

Figure 17 is a detail view upon an enlarged scale taken in vertical section substantially upon the plane indicated by the section line 17---17 of Figure 16;

Figure 18 is a detail view taken upon an enlarged scale and in vertical section of the swivel connection by which the concentrating device is carried by the drill string; and

Figure 19 is a detail view in vertical section of the modified constructionof the lower end of the, concentrating device of Figures, 16 and 17..

It is well known in the oil well drilling industry that the maintaining of a continuous circulation in the well bore of a drilling fluid, commonly known as drilling mud, is essential for eflicient and economical drilling operations. Further, it is common knowledge that the well driller is often confronted by serious problems resulting from two basic types of drilling fluid losses into formations penetrated by the well bore.

The first of these losses, commonly referred to as water-loss or filtration involves a relatively small, slow loss of the filtrate during. filtration of a drilling fluid by certain, finely porous, filter-like formations. Waterloss may be controlled almost as desired by regulating the composition or properties of the drilling fluid, thereby regulating the sealing action. of the residue, commonly known as wall-cake which is deposited upon the filtermg surface of such strata during this filtration process. The control of water-loss is very often extremely important, but practically no difficulty in maintaining circulation of drilling fluid is presented due to water-loss.

The second type of loss, commonly referred to as loss of circulation or lost returns occurs due to penetration by the well bore of porous or leaky formations, sometimes called thief formations or lost circulation zones, containing permeable pore spaces, fractures, faults, fissures, cavities and the like which are relatively large, causing correspondingly large and rapid losses of drilling fluid. Loss of circulation may result due to permeable pore spaces ranging in size from those immediately larger than will effectively filter dispersed colloidal material from a colloidal suspension or drilling fluid, as in the foregoing filtration process which results in water loss, to very large caves and caverns which may contain migrating water or communicate with the atmosphere. Improper handling of drilling fluids or heavy muds may break down certain formations, compress unconsolidated strata or lift overburden to form cavities which cause loss of circulation. Loss of circulation is a problem in itself, but may result in a number of other fatal effects upon the well drilling operation.

In order to attempt to prevent loss of circulation, it has become customary to introduce drilling mud additives commonly known as lost circulation materials into the drilling mud for the purpose of sealing or clogging the porous, thief formations with such material and thereby prevent loss of the drilling fluid into such formations. Various materials have been employed for this purpose with varying degrees of success.

In general, however, it is desirable to employ as great a concentration of the lost circulation materials in the drilling fluid as can be handled, by the pumps and other elements of the drilling mud circulating system, without excessive difficulty. Obviously, a greater concentration of the drilling mud additive at a leaky formation will more quickly and more certainly seal and plug the same, preventing further loss of circulation and permitting the normal drilling operation to be continued. However, in present systems for circulating drilling fluids, there are definite limits to the amounts or concentrations of lost circulation material which may be employed therein. Thus, an unduly high concentration of such material will tend to clog the pumps, and other elements of the system, necessitating shutdowns while the obstructions are cleaned therefrom. In general, therefore, it may be stated that the concentration of the drilling mud additives in the drilling mud has a relatively constant limit imposed or determined by the characteristics of the mud pumps and other elements of they drilling fluid circulatory system.

The present invention aims to overcome these difliculties by devising a process and an apparatus whereby lost circulation material may be discharged in a well bore in concentrations which are independent of the capacities of the mud pumps, valves and other elements of a drilling fluid circulator system.

Embodiment of Figures 1-4 and 12 Reference is now made first to Figures 1-4 and 12 "which show one satisfactory embodiment of apparatus for practicing the principles of this invention. The numeral 10 designates in general a drilling rig of any conventional design for operating a drilling pipe or drill stem 12 which is positioned inside the well bore 14. At its lower end, the drill pipe 12 has swivelly attached thereto a concentrating device indicated generally by the numeral 16 and of a construction to be set forth hereafter, an anchor or tail pipe 18 being disposed below and carried by the concentrating device. In the view of Figure 1, the drill pipe is shown as lowered in the well with the anchor pipe 18 resting upon the bottom of the same.

It should be understood that the concentrating device 16 may be disposed at any convenient position along the drill pipe 12 when suflicient anchor pipe 18 is employed to engage the bottom of the well.

Referring now more specifically to Figure 2, it will be apparent that the concentrating device indicated at 16 consists of a plurality of elements. Thus, there is provided a cylindrical or sleeve member 20 which in its upper end has a chamber 22 which slidably and rotatably receives a cylindrical member 24 which is secured to the lower end of the tubular drill stem 12 and also is fixedly secured to the upper end of an inner tubular member 26 which extends into the interior of the sleeve member 20. A suitable internal flange or guide 28 is provided for journaling the inner tubular member 26 within the upper end of the sleeve member 20 and performs other functions indicated hereinafter. At any convenient position adjacent its lower end, the sleeve member 20 has fixedly secured thereto an external flange or plate 30, and a formation packer 32 is movably positioned upon the sleeve member 20 below the flange or collar 30 and upon its lower surface is engaged by a movable collar member 34 which is slidable upon the exterior of the sleeve member 20.

Slidably received upon the lower end of the sleeve 20, is a lower casing member 36 to the lower end of which is secured the anchor pipe 18. A plurality of suitable outlet apertures 37 and a suitable longitudinal slot 38 are provided in the lower casing member 36, the slot receiving a pin 40 carried upon the exterior of the lowermost portion of the sleeve 20 whereby the member 36 is retained upon the sleeve 20 and prevented from relative rotation thereon but is allowed a limited vertical or axial movement with respect to the sleeve 20. The upper end of the lower casing 36 abuts the member 34 whereby when suflicient weight of the drill stem 12 rests upon the anchor pipe 18 upon the bottom of the well bore 14, this weight applied by the members 30 and 34 to the formation packer 32 will radially expand the latter, as shown in Figure l, to cause engagement of the same with the walls of the well bore and thus prevent rotation of the packer and the exterior elements of the concentrator 16 which are fixedly attached thereto. If desired, the packer 32 may constitute a fluid tight seal in the well bore, although for the basic purpose of this invention, it is sutficient that the packer shall prevent rotation of the sleeve 28 and hold the same stationary during rotation of the drill stem 12 and the inner tube member 26 asset forth hereinafter.

As will be more readily apparent from Figures 2 and 12, the inner tubular member 26 is provided in its upper portion with a suitable aperture or port forming an inlet 42 which opens into the interior of the sleeve 20 below the partition 28 therein. This inlet thus establishes communication between the interior of the drill stem 12 and the annular chamber or space 44disposed between the sleeve 20 and the axially disposed tubular member 26 therein and also with the interior of the tubular member 36.

A spiral vane 46 constituting a spiral conveyor screw is integrally formed upon the tubular member 26 and extends throughout any desired portion of the length of the same, it being observed that this conveyor screw 46 is of such size that its periphery will contact the inner surface of the tubular sleeve 20, while the pitch of the screw may progressively decrease from its upper to its lower end, although this is not essential to the operation of this invention. It will be apparent that when the drill stem is rotated, the conveyor screw 46 will rotate therewith within the chamber 44, constituting an impeller for the material within the sleeve as set forth hereinafter. The sleeve 20, as shown more clearly in Figures 3 and 4, is provided with a plurality of apertures or ports 48 therein. These apertures may be arranged in any desired pattern and over any desired portion of the cylindrical surface of the sleeve 20, and they may be of any desired shape or size. Preferably, however, these ports are funnel-shaped or conical, having their apex portions 50 opening into the interior of the sleeve 20 and into the chamber 44, and having their discharge or base portions 52 enlarged and disposed upon the exterior of the sleeve.

The operation of the apparatus as described above is as follows. By means of the conventional mud pump and associated elements, not shown, drilling fluid containing lost circulation material or drilling mud additives at any suitable concentration as dictated by conventional practice is fed downwardly through the drill stem 12 and is discharged into the annular space 44 of the concentrator 16 through the inlet apertures 42 in the inner tubular member 26. The drilling mud additive, as referred to herein comprises any undissolved material capable of being mechanically screened from a drilling fluid, and is depicted in the drawings by the numeral 54. The liquid phase of the drilling mud passes from the annular chamber 44 through the apertures 48 of the sleeve 20 and out of the concentrator 16 into the well bore 14. The reduced or apex inner ends of the ports 48 areof such size that although they will permit free passage of drilling fluid, they will oppose or restrict flow therethrough of the drilling mud additive. It will then be seen that the sleeve 20 of the concentrator 16 functions as a screen for separating the lost circulation material or at least a substantial portion of the same from the drilling mud which is a fluid carrier therefor.

Consequently, as the additive is screened from and separated from the drilling mud, it is retained and concen-' trated in the chamber 44. As the inner tubular member 26 rotates, the conveyor screw 46 thereon will wipe across and clean the ported cylindrical interior surface of the sleeve 20. Further, the conveyor screw will feed the retained material downwardly through the sleeve 20 into the tubular member 36 and out of the concentrator 16 through the outlet apertures 37 which, preferably, are larger than or otherwise offer less resistance to the passage of concentrated lost circulation material than do-the screening apertures 48.

The screening action of the concentrator may be enhanced by the employment of a variable or other suitable resistance to flow atthese outlet apertures 37, as set forth hereinafter. However, sufficient screening action at the screening apertures 48 may be obtained by the initial employment of conventionally high concentrations of lost circulation material in a low viscosity drilling mud, by pumping relatively large volumes of drilling fluid containing the drilling mud additive under similar high pressures into the concentrator 16, by the employment of a conveyor screw of decreasing pitch or incorporating other apertures 48 offer more resistance to the passage of concentrated lost circulation material than the outlet apertures 37, they offer less resistance to flow of drilling fluid than do the outlet apertures 37 by virtue of being disposed higher in the concentrator 16 and nearer the mud pumps. The concentrator 16 may in some instances be primed by manually plugging the same with lost circulation material before lowering the same into the well bore.

I There will thus be a discharge from the concentrator 16 of highly concentrated lost circulation material which .will move towards thief formations and being of a much greater concentration than could pass through the pumps and'the mud circulatingsystem will more effectively sea] the formation.

lt will be apparent that the principle of this invention lost circulation material while discharging or passing the liquid phase of the drilling fluid until the concentrated material is discharged through the outlet apertures 37 of the concentrator 16. v

Figure 1 indicates at 54 a concentrated mass of lost circulation material as being discharged from the outlet apertures 37 in the tubular member 36 into the well bore for sealing porous formations and preventing loss of drilling mud therein.

Modification of Figure 5 The embodiment of apparatus described hereinbefore is equally susceptible to use with other arrangements. Thus, instead of the formation packer 32 securing the sleeve against rotation, an arrangement such as that illustrated in Figure 5 may be employed.

Thus, a sleeve 60 is provided which is identical with the sleeve 20 except that the formation packer 32, the fixed and movable flanges 30 and 34 and the lower casing sleeve 36 are omitted. At its lower end, the sleeve 60 is instead provided with serrations or teeth 62 which are adapted to engage the bottom of the well bore 14 and thus anchor the sleeve 60 against rotation in the well. However, this arrangementrmay also be employed above the bottom of the- Well when used in conjunction with anchor pipe 18, by providing a serrated or anchoring foot upon the lower end of the tail pipe. The sleeve 60 is provided with the outlet aperture 37, for the discharge of concentrated drilling mud additives, and are identical with the outlet apertures 37 in the tubular sleeve 36 as set forth her'einbefore.

Received within the sleeve 69 is the inner tubular member 26, as previously described, and having the conveyor screw 46 thereon and the inlet aperture 42, together with the swivel consisting of the cylindrical member 24 rotatable within the chamber 22 disposed above the partition 28. The sleeve 60 is, of course, apertured at 48 in the same manner as the sleeve 20 and except for the means .for preventing rotation of the sleeve, is in every respect identical with the sleeve 20. Accordingly, a further explanation of the operation of this arrangement is believed to be unnecessary.

In both of the embodiments of Figures 1-4 and of Figure. 5, the concentrator is disposed on the lower end of the drill pipe near the bottom of the well or is ;used in conjunction with varied lengths of anchor pipe. How ever, andas set forth hereinafter, as shown in Figure 6, it is possible to, provide a form of concentrator which may bedisposed at any desired elevation within a well bore without the use of anchor pipe and which'is carried by suitable resistance therein and although the screening 15 a drill pipe as the latter hangs in the well bore.

At its lower end, the sleeve 60 is internally threaded, at 61, these threads preferably extending from above the uppermost outlet aperture to below the lowermost aperture. One or more externally threaded hollow sleeves or rings 63 are engaged in the threads 61, being provided with central passages 65 which are of such size as to oppose substantially no resistance to fluid flow therethrough. Alternatively, if desired, the passages 65 may be of such predetermined size as to effect any desired resistance to flow. By adjustment of the rings axially of the sleeve member 60, the upper and/or lower edges of the rings may be caused to mask or obstruct the area of the outlet openings 37 to any desired extent, thereby efiecting a variable adjustable restriction of flow through the discharge apertures. Thus, the pressure required to force the concentrated lost circulation material from the concentrator, and consequently the degree of concentration effected upon the material, may be controllably varied. In this form of restrictor, the adjustment above mentioned will be made before the concentrating device is lowered into the well bore.

This form of flow restrictor, consisting of the adjustable masking rings 63 may be utilized with the embodiment of Figures l4 above mentioned, and also with the forms of Figures 9, l3 and 15.

Modification of Figure 6 Attention is directed more specifically to Figure 6 which shows a means whereby the concentrator may be disposed at any desired position in a well. In this figure, there is illustrated a sleeve '70 which, as in the preceding embodiments, has a cylindrical chamber 22 for rotatably and slidably receiving a cylindrical member 24 which is fixedly secured to the lower end of the drilling pipe 12 and which is also rigidly secured to the upper end of the inner tube 26. The latter member is, of course, rotatably journaled in the partition 28 which divides the chamber 22 from the annular chamber 44 within the sleeve 70. The inner tubular member 26 is likewise provided with a discharge port 42 which is disposed within the chamber 44, and is also provided with the integral helical screw member 46 as in the preceding embodiments.

However, adjacent its lower end, below the funnelshaped perforations 48, the casing 70 is provided with an expansible formation packer 72. The latter is retained between an annular external flange 74 on the lower end of the casing 70 and an upper flange 76. The packer 72 is provided with an annular chamber 78 therein which surrounds the imperforate lower end of the sleeve 70. A

tubular U-shaped conduit 30 has its hollow legs communicating with the chamber 78 within the formation packer 72 and upon its midportion has a stationary upstanding tubular neck 82 which is swivelly received within the open lower end of the tubular member 20.

Thus, when the outlet course of the fluid from port 42 through the ports 4-8 is restricted or plugged as by the clogging with concentrated lost circulation material of the annular chamber 44, the pressure of the drilling mud from the interior of the drill pipe 12 is supplied to the stem 82 and to the conduits 80 and from thence into the chamber 78 for expanding, by hydraulic pressure, the packer '72 into engagement with the wall of the well bore, thereby holding the sleeve 70 against rotation. The member 72 is thus a pressure operated holding means which is intended to perform the same function as the packer 32 or the teeth 62 in the preceding embodiments. The sleeve 70 is suitably opened at its lower portion to form the outlet port 84 for discharging the concentrated lost circulation material. The operation of the screw impeller 46 is identical with that of the preceding forms, the differ" ences of this latest modification residing in the hydraulic holding means for preventing rotation of the casing 70; and the concept and structure whereby the concentrator may be disposed at any particular formation through which the well bore passes.

Modification of Figures 7 and 8 In all of the preceding embodiments, it will be noted that the drill stem itself has been employed as a source of power for operating the screw impeller to compress and discharge the concentration of drilling mud additives from the concentrator unit; and further, that the concentrated material is discharged continuously therefrom. In Figures 7 and 8, there is disclosed a still further apparatus for performing the same general purpose; but using the pump pressure as the contracting and discharging means and for effecting an intermittent or batch discharge of slugs of concentrated material.

Thus, there is provided a sleeve which is adapted to be secured in any suitable way to the lower end of a drilling stem. The lower end of the sleeve 90 is provided with previously mentioned fluid straining or concentrating ports 48, and an inner tubular member 92 is disposed axially and fixedly on the interior of the sleeve 90, being secured therein as by integral lugs or brackets 94. Adjacent its lower end, the tubular member 92 is provided with a partition 96 through which is slidably received a rod 98 having a piston 100 rigidly secured to the upper end of the same and slidable Within the inner tube 92. A compression spring 102 is disposed within the member 92 below the piston 100 and above the partition 96 for yieldingly urging the piston rod into its uppermost position as shown in Figure 7. The lower end of the rod 98 is screw threaded to adjustably receive the hub 104 of a closure valve 106 for closing the open lower end of the sleeve 90. A look nut 108 is employed to maintain the valve in an adjusted position upon the rod 98.

In this form of the invention, the spring 102 normally retains the valve in closed position whereby the lost circulation material passing down the drill stem into the upper end of the sleeve 90 will accumulate and become concentrated in the perforated lower end of the sleeve 90 above the closed valve member 106. This concentration will continue, as the liquid phase of the drilling mud passes through the screen ports 48, leaving the larger particles of lost circulation material within the seeve. As this collection of material begins to clog and reduce the area of the ports 48 through which the drilling mud passes, the pump pressure upon the drilling fluid will increase until such time as the valve 106 is opened by this increasing pressure against the resistance of the spring 102 as shown in Figure 8, and the concentrated material will be discharged under the pump pressure as a slug.

It will thus be apparent that the pressure will periodically increase until such time as the same is sufficient to open the valve, whereupon the concentrated mass of lost circulation material will be intermittently discharged in slugs or batches. In this form of the apparatus, the concentration and quantity of material discharged and the frequency of the discharging operations is regulated by the pumping pressure and volume and the compression of the spring 102, the latter being ad'ustable as to its strength by varying the position of the hub 104, valve 106 and nut 108 upon the threaded end of the rod 98.

Modification of Figure 9 Still another form of intermittently discharging concentrating and pump pressure actuated device is disclosed in Figure 9. In this form, the attachment 109, fixedly attached in any suitable manner on the lower end of the drill stem 12, terminates in a spring closed check valve 110 and is provided with a sleeve 112 slidable thereon which has a suitable longitudinal slot 114 in which is engaged a pin 115 carried by the extension or attachment 109, this pin permitting a limited longitudinal movement of the sleeve 112 but preventing rotation of same relative to the drill stem. A compression spring 116 may be secured to the drill stem extension 109 in any suitable manner and at its lower end bears against the upper end of the sleeve 112 for urging the latter downwardly upon the drill stem extension 109, as shown in Figure 9.

Below the end of the drill stem extension 109 which contains the non-return check valve assembly 110, the sleeve 112 is provided with the usual funnel-shaped or conical strainer or screening perforations 48 previously described. Slidably received within the open lower end of the sleeve 112 is a cylindrical plunger 117 having an externally flanged closed lower end 118 and a compression spring 120 interposed between this flange and the bottom of the sleeve 112. This spring urges the plunger 117 downwardly with respect to the sleeve 112. Movement of the plunger is limited by pins 121 and longitudinal slots 123 similar to 115 and 114, as previously described.

The plunger 117 is provided with a port or set of ports 122 which is adapted to move into and out of register with corresponding ports 124 formed in the lower end of the sleeve 112. The arrangement is such that when the plunger 117 is forced inwardly of the sleeve 112, the ports 122 and 124 will register whereby the interior of the sleeve will be discharged or vented through the aligned ports into the well bore. However, when the plunger is moved outwardly of the sleeve 112 under the influence of the spring 120, the ports are moved out of registry, whereby the funnel-shaped apertures 48 will constitute the only means of exit from the sleeve 112.

In this arrangement, the drilling mud including the lost circulation material will be introduced through the interior of the drill stem 12 and the extension 109 into the interior of the sleeve 112. The liquid phase of the drilling mud will pass through the apertures 48 being strained therefrom and leaving behind the larger particles of the lost circulation material. This latter material will accumulate and collect in the chamber between the valve assembly 110 and the closed bottom end of the plunger 117. At suitable selected intervals, either controlled automatically or manually as desired, the drill stem may be lowered until the plunger 117 or an attached length of anchor pipe, not shown, rests upon the bottom of the well, and until the weight of the drill stem causes the plunger 117 to move mwardly of the sleeve 112 against the spring 120. When this occurs, the ports 122 and 124 being in registration, the lost circulation material will be discharged in a slug or batch through these ports 122 and 124 by the forcing action of the downward movement of the drill pipe extension 109 and attached check valve assembly 110 against the uppercompression spring 116 together with the hydraulic pressure exerted by the mud pumps.

Thus, a highly concentrated mass or batch of the drilling mud additive is discharged into the well bore for treating leaky formations. As soon as the drill stem is lifted, however, the spring 120 will close the ports 122 and 124, the upper spring 116 will force the sleeve 112 downward with respect to the drill pipe extension 109 and attached check valve assembly 110 thereby re-exposing the cleaned screening apertures 48 for repeating the straining phase of the operation. The weight of any anchor pipe which may be employed will assist the springs 120 and 116 in performing this function of resetting the device.

The form of adjustable flow restrictor disclosed in Figure may also be incorporated into this embodiment. Thus, the rings 63 of Figure 5 may be screw threadedly engaged in the hollow plunger 117 for controlling the ports 122 thereof in the samemanner disclosed in connection with the ports 37 of Figure 5. In this arrangement, while the ports 22 are continuously held open by the weight of the drill stem while the head 118 is on the bottom of the well bore, the adjustable rings 63 will provide an adjustable control of the degree of concentration of the material passing from the ports 122, 124.

In this embodiment, it is possible to produce an initial discharge of a plug having a maximum concentration of material by causing the weight of the drill stem to open the ports 122, 124 and thereafter cause a continuous discharge of a different concentration of lost circulation material to supplement the action of the plug initially discharged.

Modification. of Figure 10 Shown in Figure 10 is a basic form of concentrating device which illustrates the fundamental principles of the invention and which consists of a section of pipe of any desired length, open at both ends and perforated with any number of screening apertures 48 of any size or shape. The concentrator, as shown in the figure, employs the previously mentioned, preferred, conical apertures 48 which will efliciently screen lost circulation material from a drilling fluid and which are less likely to become clogged with the drilling mud additive. It should be understood that very high concentrations of lost circulation material may be obtained and efiectively used to seal porous thief formations by the employment of this basic concentrator.

When this concentrating device is attached to and included between an upper and a lower section of drill pipe conventionally disposed within a well bore, thereby forming a perforated section of the drill stern and drilling fluid is pumped into the string, which is open at its lowermost end, the drilling mud will tend to follow the course of least resistance through the screening apertures 48 since more pressure is required to pump the same out the lowermost open end of the drill stem. Therefore, should the drilling fluid contain lost circulation material, it is obvious that the drilling mud additive may be screened from the drilling fluid, retained and concentrated within the string as the drilling mud leaves the device through the screening apertures 48.

It is readily apparent that the efliciency of this screening and concentrating action may be increased by increasing the area of port of the screening apertures 48, thus decreasing the resistance to flow through the same. This may be accomplished by increasing the number of apertures 48 or the size thereof. The screening and concentrating action may also be augmented by increasing the resistance to flow below the screening apertures 48 as by placing the concentrator higher in the drill string or including a suitable restriction below the concentrator as set forth more fully hereinafter. The lower end of the sleeve or pipe 130 is internally threaded at 131 to receive the externally threaded metering bushing or sleeve 133 which has an aperture 135 of a predetermined area. It is contemplated that plugs having metering apertures of different areas may be interchangeably inserted in the sleeve 130 to vary the resistance to flow therethrough.

Such restriction may also be in the form of a suitable drill bit which will permit the drilling operation during the employment of a concentrating device.

As the concentration of lost circulation material is formed by this arrangement, it is forced downwardly through the lower section of drill pipe, which is disposed below the concentrator, and out through the open lowermost end of the drill string into the well bore by the hydraulic pressure exerted by the mud pumps.

It will be noted that as the lower section of drill pipe, which is disposed below the concentrator, becomes filled with the downwardly moving highly concentrated lost circulation material, the resulting friction will constitute a resistance below the screening apertures 48 and augment the screening and concentrating action as previously described. Therefore, the efiiciency of this arrangement is necessarily limited to the pressures available for discharging the concentrated drilling mud additive out of the string through the outlet at its open lowermost end. Otherwise, the whole lower section of the string may become plugged with the concentration, requiring operations to be discontinued. However, this form of concentrating device may not only be placed at any position within the pipe string, but may be attached at the lowermost end of the same.

Figure 11 is very similar to the embodiment of Figure 10, but indicates a sleeve 140 having a restriction 142 of any form below the screening apertures 48 for increasing the efficiency of the screening and concentrating action previously described.

Reference has been made hereinbefore to provision for the adjustable restricting or throttling of flow of the concentrated lost circulation material through the discharge apertures of the various embodiments of apparatuses disclosed herein as a means for controlling the degree of concentration of the lost circulation material; and/ or the frequency or rate of its discharge.

In both of the embodiments of Figures and 11, as well as in that of Figure 5, the flow restrictors are of the preset adjustable type, being applied prior to lowering of the concentrating device in the well bore. This restrictor may be included in any of the concentrating devices of Figures 6, 7 and 11.

Modification of Figures 13 and 14 This embodiment very closely resembles the form of the invention disclosed in Figure 5, including a generally cylindrical casing 150 having a partition 152 in its upper portion to define a chamber 154 thereabove in which is rotatably mounted a swivelling connection 156 by means of which the drill stem 12 is connected to the upper end of the inner tube 158 having the conveyor blades 160 thereon. The portion of the sleeve below the partition 152 is provided with the previously mentioned strainer or screening apertures 48 for the purposes previously set forth. Just below the partition 152, the tube 158 is provided with one or more discharge apertures 162 by means of which drilling fluid with lost circulation material admixed therewith may be discharged into the chamber 164 disposed beneath the partition 152.

At its lower end, the perforated portion of the sleeve 150 is diametrically enlarged, as at 166, to form a valve chamber for intermittently discharging slugs or batches of concentrated lost circulation material, as set forth hereinafter. The open lower end of the enlargement 166 is internally threaded, as at 168, for receiving the externally threaded neck 170 of an internally threaded sleeve or bushing 172. The latter is provided with one or more discharge apertures 174 extending through the side wall of the same, and externally threaded rings 176 are threadedly engaged in the internally threaded sleeve 172 and are axially adjustable therein to adjustably mask or throttle the outlet openings 174.

The lower edge of the sleeve 172 may be either open or closed, as desired, and is provided with a plurality of serrations 178 whereby the lower end of the concentrator may be securely held in a stationary manner upon the bottom of a well bore to prevent rotation of the same.

Within the enlarged lower end 166, there is provided a valve assembly for controlling the intermittent discharge of slugs of concentrated material. Conveniently, as will be apparent from Figure 14, this valve assembly consists of a stationary, preferably semi-circular plate 180 which is secured to a portion of the inner Wall of the enlarged housing portion 166, and has a substantially diametrically extending edge across the interior of the housing.

Cooperation with the stationary valve member 180 is a similar plate 182 which is welded or otherwise rigidly secured to the lower end of the tube 158 for rotation therewith. As will be apparent from Figure 13, the adjacent edges of the plates 180 and 182 are disposed in overlapping relation so that as the valve member 182 rotates, it will alternately close and open the passage by the stationary valve member 180.

As will be noted, the cross-sectional area of the mem- "ber 166 has been considerably enlarged'with respect'to that of the chamber 164 in order that there shall be ample passage area to permit passage of the concentrated material from the chamber 164 during the intermittent periods when the valve is opened.

It will be, of course, understood that the valve plates and 182 may be constructed to provide any desired area of passage therebetween, and also to provide any desired duration during which the passage is open as well as any desired interval between the opening and closing of the passage.

Except for the intermittent valve action in releasing the concentrated material in the form of slugs from the chamber 164, the arrangement of Figures 13 and 14 may be considered as identical with that of Figure 5, previously described.

Modification of Figure 15 In Figure 15, there is disclosed an application of the principles of Figures 5 and 13 to the arrangement of Figure 2. The numeral discloses the lower portion of a casing corresponding to the casing 20 of Figure 2, and in which is received the lower end of the inner tube 26 having the helical auger screw'46 thereon, as previously described. At its lower end, the sleeve 190 is externally threaded, as at 192, and is internally threaded as at 194. A bushing 196 is internally threaded, as at 198, for screw threaded engagement upon the threads 192 of the sleeve 1%. At its lower end, the bushing 196 is diametrically reduced to provide a depending portion 200, to which any desired length of tail or anchor pipe 202 may be secured. This latter pipe is preferably closed at its-lower end, as shown, and the interior of the sleeve 190 communicates with the well bore through the discharge apertures 204.

A pair of externally threaded rings 206 and 208 are provided for engagement with the threaded portions 194 and 198 for adjustably masking or controlling the discharge apertures 204. These rings function in the same manner as previously referred to control rings 63 in the embodiment of Figure 5.

A rotary valve member consisting of a fixed valve plate 210 and a rotary valve plate 212 is provided. These valve plates are arranged in the same manner and correspond to the valve plates 180 and 182 of the form of Figure 13.

It is believed that the operation of this form will be now clearly understood from the previous explanation with regard to Figures 5 and 13. By means of the tail pipe 202, the discharge openings 204 may be placed at any desired position within a well bore, and the size of these openings may be varied by the control rings 206 and 208 in order that the rotary valve assembly 210, 212 may periodically time the discharge of batches or slugs of concentrated lost circulation material from the concentrator into the well bore.

Modification of Figures 16-I9 A still further form of concentrating device is disclosed in Figures 16-19. In this form, there is provided a sleeve 220 which has its upper portion imperforate and provided with a swivel assembly, indicated generally by the numeral 222 and which is shown in detail in Figure 18. Throughout any desired proportion of its length, the sleeve 220 is provided with the previously mentioned strainer or screening apertures 48, and a stem 26 which may be either tubular or solid is disposed in the sleeve and is provided with the conveyor blade 46, all as previously set forth in connection with the other embodiments of the invention.

As shown best in Figure 17, the lower end of the casing 220 is internally threaded at 224 for the reception of a cylindrical body 226. The latter is provided with a pair of elongated slots 228 and a central axially extending dividing web or rib 230 is provided therein. The

13 I the slots to provide a transverse passage 232 which constitutes a discharge port for the cylindrical body 226. At its lower end, the cylindrical body 226 is provided with an open bore 234 which is normally closed by a cap 236 having a plurality of fins 238 upon its bottom surface. It will thus be seen that the body 226 and the cap 236 constitute a closure means for the open lower end of the concentrator sleeve 220, as shown in Figure, 17. Alternatively, as shown in Figure 19, the sleeve 220 may be closed at its lower end as by a plug 240 for a purpose which will be subsequently set forth.

Referring now more particularly to Figure 18, it will be seen that the swivel assembly 222 comprises a hollow mandrel 242 which intermediate its ends is provided with an annular enlargement in the form of a ring or collar 244. This collar is slidably received in the bore of the sleeve 220, and a rubber O-ring 246 is seated in cooperating peripheral grooves in the wall of the sleeve and of the collar 244, to prevent leakage of drilling fluid past the collar. Disposed above the collar is an antifriction bearing assembly 248 of any desiredcharacter which rests upon the collar and is retained therein by the lower externally threaded portion 250 of the gland 252. The gland surrounds the mandrel and at its upper open end is provided with a chamber 254 in which is received a further antifriction bearing assembly 256 which surrounds the mandrel and which is retained in the chamber by the lower end of the packing nut 258. An O-ring 260 is also provided between the packing nut 258 and the Wall of the chamber 254 in order to prevent leakage of fluid through this packing assembly. The packing nut 258 is threadedly engaged upon the mandrel and is retained thereon as by a locking nut 262 which is provided with a setscrew 264. The mandrel 242 at its upper end is connected in any desired manner to the drill stem 12 previously mentioned, whereby drilling fluid having lost circulation material admixed therewith may be supplied through the mandrel into the interior of the sleeve 220.

At its lower end, the mandrel 242 extends into the chamber 4-4 formed between the conveyor shaft 26 and the wall of the casing 220, and is provided with one or more apertures or ports 266 for discharging fluid into the chamber 44. The upper end of the conveyor shaft 26, whether hollow or solid, is received within and fixedly secured to the open lower end of the mandrel, as shown in Figure 18.

It will thus be apparent that the conveyor screw is journaled in the casing in such a manner that the casing may be readily held stationary in the well bore in any of the manners previously described while the rotation of the drill stem will, in turn, cause rotation of the conveyor.

It is to be understood that the above described swivelling arrangement disclosed in Figure 18 may be readily applied at any of the swivels previously mentioned in connection with the other embodiments of the invention.

Method of operation When in the drilling of well bores, a porous or thief formation is encountered of such character as to require extraordinary concentrations of lostvcirculation material in order to seal the same and regain circulation, the following method may be employed.

A concentrator sleeve is primed and then attached to the end of the drill string. The sleeve may be primed by closing the lower end of the concentrator sleeve, as by the closure plug 240, and then coupling the sleeve to a mud circulating system. As the drilling fluid containing the lost circulation material admixed therewith is circulated through the concentrator, the liquid phase of the same will be strained through the screening openings 48, leaving the larger particles of the additive in the casing. This is continued until the desired concentration of lost circulation material is attained, and for this purpose, 1'0- 14 tation may be imparted to the screw for further compressing and compacting such material. With the concentrator thus primed, the closure plug 240 is removed and the appropriate connection made in accordance with the various embodiments set forth in this application for the discharge of the concentrated material therefrom. With the primed concentrating device then applied to the end of a drill stem, the latter is lowered in the well bore until the concentrator device is at the location at which the loss of circulation occurred. Thereafter, as drilling fluid is supplied by the mud circulating system, rotation of the drill stem will cause the conveyor screw to force the batch of concentrated material from the device into the well bore where it will be carried into the fissures and crevices which it is intended to seal. It will be noted that in addition to this initial slug or plug of material discharged from the concentrator, the continued operation of the latter will cause a subsequent and sequential flow of the concentrated lost circulation material from the device into the well bore, either continuously or in intermittent batches, depending upon the type of apparatus hereinbefore disclosed, which is employed. In order to facilitate the action of the lost circulation material in sealing the leak, the device may be raised or lowered periodically during its operation so as to distribute the material along a selected portion of the height of the well bore.

It is an important characteristic of this invention that by means of a continuous flow of drilling mud containing lost circulation material admixed therewith in a proportion in accordance with conventional practice and capacity of existing conventional mud pumping equipment, there may be selectively secured very highly concentrated batches of lost circulation material; and these batches may be discharged intermittently at regular intervals into the formation to be sealed, or may be discharged continuously at a lesser concentration; or, combinations of the same may be effected.

In some instances, where a fine porous formation is encountered, it may be found preferable to under-ream the same in order that when the formation is sealed, the passage of the drill bit into the bore to resume its drilling operation may not scrape any of the sealing material adhering as a thin sheath to the interior of the well bore.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation as shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the appended claims.

What is claimed as new is as follows:

1. A method of preventing the loss of circulating drilling fluid from a well bore into a porous formation, which comprises inserting into a well bore having drilling fluid therein a pipe containing a discrete batch of lost circulation material, introducing into said pipe and circulating through said pipe and well bore drilling fluid having lost circulation material admixed therewith in a lesser proportion than that of said discrete batch and thereby displacing said batch from the pipe into the well bore, conveying by said circulating drilling fluid said batch fro-m said pipe into said porous formation and thereby initiating sealing of the latter, completing sealing of the porous formation by the application thereinto of the admixed lost circulation material in said drilling fluid.

2. A method of preventing the loss of circulating drilling fluid from a well bore into a porous formation, which comprises inserting into a well bore having drilling fluid therein a pipe containing a discrete batch of lost circulation material, introducing into said pipe and circulating through said pipe and well bore drilling fluid having lost circulation material admixed therewith in a.

lesser proportion than that of said discrete batch and thereby displacing said batch from the pipe into the well bore, straining the introduced drilling fluid during its passage through said pipe and removing therefrom a portion of the drilling fluid thereby increasing the concentration of the lost circulation material in the remainder of the drilling fluid, conveying by said circulating drilling fluid said batch from said pipe into said porous formation and thereby initiating sealing of the latter, completing sealing of the porous formation by the application thereinto of the admixed lost circulation material in said concentrated remainder of said drilling fluid.

3. The method of claim 2 wherein said step of displacing said batch from the pipe into the well bore includes the steps of alternately preventing and effecting flow of said concentrated remainder from said pipe into 'said well bore at uniform time intervals whereby said concentrated remainder is intermittently discharged from said pipe into said well bore at uniform time intervals.

4. An apparatus for preventing loss of a circulating drilling fluid from a well bore into an adjoining porous formation comprising; a pipe disposed in a well bore, means introducing into said pipe and circulating through said pipe and well bore a drilling fluid having a lost circulation material admixed therewith, a concentrator connected to said pipe and receiving drilling fluid therefrom for increasing in a portion of said drilling fluid the proportion of lost circulation material over the proportion of the latter in said introduced drilling fluid, said concentrator having a discharge passage for said portion opening into said well bore, said concentrator including a spiral conveyor and means associated therewith for straining drilling fluid from the introduced drilling fluid admixed with lost circulation material, means causing rotation of said spiral conveyor, valve means connected to and driven by said spiral conveyor and disposed in and controlling said passage for effecting intermittent, periodic discharge of said portion of drilling fluid in separate batches from said concentrator into said well bore.

5. The combination of claim 4 wherein said valve means comprises a stationary plate partially closing said passage and a movable plate connected to said spiral conveyor and slidably engaged and cooperating with said stationary plate for periodically completely closing said passage.

6. The combination of claim 4 wherein said introducing means includes a passage in said spiral conveyor having an exit into said concentrator.

7. The combination of claim 4 including means anchoring said concentrator against rotation in a well bore.

8. The combination of claim 4 wherein said rotation causing means for said spiral conveyor comprises means mounting the latter upon and connecting the latter to said pipe and means for rotating said pipe.

9. The method of claim 2 wherein the step of straining the drilling fluid is performed continuously and without interruption and wherein said step of displacing said batch from said pipe into the well bore includes the steps of alternately preventing and effecting the discharge of said concentrated remainder from said pipe into said Well bore at uniform time intervals whereby said concentrated remainder is intermittently and periodically discharged from said pipe into said well bore as discrete slugs.

10. The method of claim 2 wherein the step of straining the drilling fluid is performed continuously and without interruption and wherein said step of displacing said batch from said pipe into the well bore includes the steps of alternately preventing and effecting the discharge of said concentrated remainder from said pipe into said well bore at uniform time intervals whereby said concentrated remainder is intermittently and periodically 16 discharged from said pipe into said well bore as discrete slugs, and at uniform time intervals.

11. The method of claim 2 wherein the step of straining the drilling fluid is performed continuously and without interruption and wherein said step of displacing said batch from said pipe into the well bore includes the steps of alternately preventing and effecting the discharge of said concentrated remainder from said pipe into said well bore at uniform time intervals whereby said concentrated remainder is intermittently and periodically discharged from said pipe into said well bore as discrete slugs, and at uniform time intervals, and in uniform quantities.

12. The combination of claim 4 including a pair of discharge ports disposed in spaced relation in said discharge passage each communicating with said discharge passage and spaced longitudinally thereof and discharging said separate batches at spaced locations in said well bore.

13. The combination of claim 12 including a flow regulator disposed in said discharge passage between said discharge ports and proportioning flow of said batches therethrough.

14. A concentrator for use in a well bore for increasing the proportion of a lost circulation material in a portion of a circulating drilling fluid having a lost circulation material admixed therewith, comprising; a casing having a cylindrical chamber therein with fluid inlet means and fluid outlet means therefor, said chamber having a wall with strainer openings therethrough, a spiral conveyor mounted in said casing and feeding drilling fluid from said inlet means to said outlet means and straining drilling fluid from said chamber through said strainer openings and thereby effecting an increased proportion of lost circulation material in the portion of the drilling fluid discharged from said outlet means, means for causing rotation of said spiral conveyor in said chamber, valve means establishing controlled communication between said chamber and the exterior of said casing for effecting intermittent, period discharge of said portion of drilling fluid from said outlet means in uniform amounts and at uniform time intervals, means operatively connecting said valve means to said spiral conveyor for actuation by the latter.

15. The combination of claim 14 including a valve housing for said valve means mounted upon said casing.

16. The combination of claim 14 including a valve housing for said valve means mounted upon said casing, said valve means comprising a stationary plate in said housing partially obstructing flow therethrough and a. movable plate slidably engaging and cooperating with said stationary plate to periodically stop flow through said housing and periodically stopping flow through said outlet means.

17. The combination of claim 16 wherein said movable plate is attached to said spiral conveyor.

18. The combination of claim 14 including a valve housing for said valve means mounted upon said casing,

said housing including means for anchoring the latter against rotation in a well bore.

19. The combination of claim 14 wherein said spiral conveyor has a fluid passage opening into said chamber, said passage comprising part of said fluid inlet means.

References Cited in the file of this patent UNITED STATES PATENTS 2,083,625 White June 15, 1937 2,167,190 Vietti July 25, 1939 2,187,895 Sanders Jan. 23, 1940 2,207,334 Reynolds et al. July 9, 1940 2,652,117 Arendt et al Sept. 15, 1953

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