US2959225A - Pressure-proportioning device - Google Patents

Description

Nov. 8, 1960 A. P. ROBERTS 2,959,225

PRESSURE-PROPORTIONING DEVICE Filed Feb. 10, 1958 2 Sheets-Sheet '1 Fla-'4 Alan P. Roberts Inventor 5W 4. Attorney Nov. 8, 1960 A. P. ROBERTS PRESSURE-PROPORTIONING DEVICE 2 Sheets-Sheet 2 Filed Feb. 10, 1958 OION o Inventor Alan P. Roberts By% M Attorney the borehole wall.

PRESSURE-PROPORTIONING DEVICE Alan P. Roberts, Tulsa, Okla., assignor, by mesne assignments, to Jersey Production Research Company Filed Feb. 10, 1958, Ser. No. 714,140 9 Claims. 61. 166-147) This invention relates to a pressure-proportioning device. It relates more particularly to a pressure-proportioning device for distributing the mud column load between well packers when at least two packers are spaced longitudinally in a borehole between the outer wall of a tubular member disposed within the borehole and the borehole wall for reducing hydrostatic pressure in a part of the borehole.

In the drilling operations in which a borehole is drilled in the earth in order to locate formations or reservoirs from which oil or gas may be obtained, it is quite frequently advantageous and desirable to isolate the area in which the bit is drilling from the remainder of the an nular space between the drill pipe and the walls of the well bore. It is known that by reducing the hydrostatic pressure on the face of the formation being drilledpdrill- States Patent 6 ing efliciency will be greatly increased. A recent technique developed which takes advantage of this factor for" increasing drilling efliciency is the so-called air or gas drilling method. In this method a drill bit is suspended at the lower end of a string of drill pipe which is supported from the surface of the earth and is rotated from the surface in a conventional manner. A drilling fluid is' forced downward through the drill string through the drill bit and back up to the surface through the annulus between the drill pipe and the walls of the borehole. The drilling fluid serves primarily to carry the rock cuttings from the drill bit to the surface and to cool the drill bit. It is readily seen that the use of air or gas, replacing drilling mud or water as the cleaning medium, gives rather substantial improvement in penetration rates and bit life.

However, it should be noted that the use of air or gas as a cleaning medium is not without problems. Perhaps the greatest single obstacle in the way'of using air or gas as a cleaning medium is the water or other fluid encountered in the various formations penetrated by the borehole. The ingress of water into the borehole and down the same to the bit may be a serious problem. The water wets the cuttings and causes balling of the cuttings and if the volume of water is suflicien-t, the balling will plug the hole or stick the drill pipe, thus causing the abandonment of the air or gas drilling operation. One method of overcoming this obstacle is the use of a drill string suspended within a casing. The air is circulated down through the drill string and back to the surface through the annulus between the drill string and the casing. A packer is set between the casing and the wall of the borehole and a drilling mud of a proper density is then used to fill the annulus between the casing and It is thus seen that this permits a pressure to be kept on the water or other fluid-producing formations which the well bore has penetrated. Quite frequently it has been found that one packer will not sustain the great weight of the mud column. Therefore, in such cases one or more additional packers must be set.

' The use of two or more packers is, of course, beneficial in that the column of mud can-be more easilysustained.

rai'lgement,

. upwardly.

2959,23 Patented Nov. 8, 1950 The pressure-proportioning device uses the principle of using difierential areas exposed to the pressure of the mud column above a top packer and the pressure in the space between the packers. A preferred embodiment of the pressure-proportioning device includes a piston with a circumferential recess intermediate its ends and a housing for receiving the piston in a sealingly and slidable relationship. The area of the top of the piston which is subjected to the downward force of the pressure of the mud column in the annulus between the casing and the borehole wall above the top packer is reduced to a de- H sired percentage of the area of the bottom of the piston which is subjected to the upward force of the pressure of the fluid in the annular cell between the two packers. It is thus seen that if the ratio R between the pressure in the annular cell between the packers to the pressure in the annulus above the packers, is equal to the ratio R: of the effective area of the top of the piston to the area of the bottom end of the piston, there is no movement of the piston. If the ratio R decreases below R ..the piston will move downwardly; and conversely if the ratio R is greater than the ratio R the piston will move When the two ratios are again equal, the piston will assume a neutral position. If the ratio of the pressure in the annular cell between the packers and the pressure in the annulus above the packers is below the ratio of the areas of the ends of the piston, the piston moves downward, thus opening a conduit means which permits fluid to flow from the annulus above the packers to the annular cell between the packers. When the ratio of the pressure in the annular cell and the pressure in the annulus above the packer reaches the desired value, the piston is returned to its neutral position thereby closing the conduit means. If the pressure in the annular cell between the packers becomes too high, the piston moves upward thus opening a conduit establishing fluid communication between the annular cell between the packers and the space below the packers. The pressure in the annular cell is reduced to the desired proportion of the pressure of the mud column in the annulus above the top packer at which time the piston returns to its normal or neutral position, thus closing the passageway means.

Various objects and a complete understanding of the invention will become apparent from the following detailed description taken in conjunction with the accompanied drawing in which:

Fig. 1 is a schematic diagram illustrating the proportioning device when used with two packers which are spaced longitudinally in a borehole between the outer wall of a tubular member and the borehole well; i

Fig. 2 is an enlarged and more detailed view of the proportioning device illustrated in Fig. 1 showing the piston of the device in a neutralposition;

- Fig. 3 is a partial fragmentary sectional view taken along the line IIIIlI of Fig. 2; Fig. 4 is a fragmentary cross section taken substantially at IVIV of Fig. 2;

Fig. 5 is similar to Fig. 2 and shows a piston in'its lowermost position; and, g

Fig. 6 is similar to Fig. 2 and shows a piston in its uppermost position and a modification of the po'rt ar- Referring to the drawing there is illustrated the best mode contemplated for carrying out the invention. Reference numeral 12 refers to the wall of a borehole drilled through an underground formation. Tubular cylinder 14 is suspended within the borehole and includes an upper section 16, sub 20 which is rigidly attached to the upper section as shown at '18, and a lower section 22 rigidly attached to the sub as shown at 24. 7 An "upper packer 26 and a lower packer 28 are supported from the tubular cylinder 14 in a longitudinally spaced relationship. These packers may be any conventional type and may be expandable by either'inflatable or mechanical means. The packers are shown in their expanded position and separate the annulus between the tubular cylinder 14 and the wall of the borehole into three compartments which for convenience will be referred to as annulus 30 which is that space above upper packer 26 and between the outer wall of the tubular support and the wall of the borehole, an annular cell '32 which is that space between the packers and between the outer wall of the tubular cylinder 14 and the wall of the borehole, and annular space 34 below packer '28 and between the wall of the borehole and the outer wall of the tubular support.

Sub 20 also serves as the valve body and has defined therein main valve cylindrical chamber 36 which has its axis preferably in substantially the same direction as the axis of the tubular cylinder 14. A reduced piston cylindrical chamber 38 is also provided in sub 20 and on the same axis as the axis of cylinder 36 and longitudinally abuts cylindrical chamber 36. A piston 40*is slidably mounted in cylindrical chamber 36 with the longitudinal dimension of the piston being less than the "longitudinal dimension of the cylindrical chamber36.

.iP iston 40 has a circumferential recess 42 intermediate of its ends. The piston is urged upwardly by a resilient fmember such as spring 44 disposed at the lower end of cylindrical chamber 36 and below the lower end of piston 40. It is preferred that one end of spring 44 f is attached to sub 20 at 53 and the other end to piston "40fat 51. An area-proportioning rod 46 is rigidly atf tached to or made an integral part of the top portion of piston 40. Rod 46 is slidably fitted within piston cylinder 38 and is'insertable therein in a sealing relationship. Seals such as O-ring seals 48 may be used to assure a seal. Piston cylinder 38 may be either air filled or It is preferred that one end of to piston 40 at 49. When piston 40 is in a neutral'position, springs 44 and 50 are preferably under neither tension nor compression. A neutral position of piston 40 is such that recess 42 is above'ports 64'and-68and below i ports 56 and 60 as shown in Fig. 2. This is also the xposition of piston 40 when there is no fluid pressure exerted upon either area 94 shown in Fig. 3 or on'area 96 shown in Fig. 4. Valve body or cylindrical chamber '36 has an upper port 52 in its upper end and above the upper end of piston 40. Port 52 through conduit 54 establishes fluid communication between annulus 30 and the interior of chamber 36 above piston 40. Valve 1 chamber 36 has an upper intermediate port 56 which "through conduit means 58 establishes fluid communica- VQV tion between annular cell 32 and the interior'of' chamber 36. A second upper intermediate port 60 is lateral- Q ,ly and circumferentially spaced in chamber'36 from port 56. Port 60 together with conduit '62 provides fluid communication between theinterior of'valve chamber 36 and annular space 34.

lt will be noted that when the piston is in the posifias asfl h w l .F sf the drawing the valved 'pass'a'geWay means between annular cell-32 and the '{annular space 34 is closed. When the piston i's-movedupward it is readily seen that this valved passageway is open as recess 42 is so positioned on piston 40 as to align with ports 56 and 60 when piston 40 is in its uppermost position. This is shown in Fig. 6 and in this position ports 64 and 68 are still covered by piston 40 and sealing elements 68, 80, and 82 sealingly engage piston 40 in fluid excluding engagement. A lower intermediate port 64 together with conduits 54 and 66 establishes fluid communication between annulus 30 and the interior of cylindrical chamber 36. A second lower intermediate port 68 is provided for cylindrical chamber 36 and is circumferentially and laterally spaced from port 64. A lower port 70 is provided in cylindrical chamber 36 and is positioned below the lower end of piston 40. A conduit 72 connects ports 68 and 70. A port 74 is provided in the lower end of cylindrical chamber 36 and is circumferentially and laterally spaced from port 70. A conduit 76 together with a conduit 58 establishes fluid communication between the annular cell 32 and the interior of cylindrical chamber 36 below piston 40. When piston 40 is in its lowermost position, the various components are so designed that recess 42 is aligned with ports 64 and 68. In other words when spring 44 is fully compressed, recess 42 of piston 40 is aligned with ports 64 and 68. At this position, sealing elements 84 and 86 still engage piston 40 in fluid excluding engagement. This is shown in Fig. 5. It is thus seen that valved conduit means establishing fluid communication between annulus 30 and annular cell 32 is established through conduit 54, conduit 66, recess 42, conduit 72, the interior of cylinder 36, and conduits 76 and 58. I

Various modifications of the port arrangement of Fig. 2 may be made. For example, in Fig. 6 port 52A opens into the upper end of cylindrical chamber 36. Port 70A is illustrated as opening into the other endof cylindrical chamber 36.

Piston 40 may be fitted within cylindrical chamber 36 with a maximum tolerance of approximately .001 inch which is normally adequate to prevent any leakage through the valve. However, for most drilling muds it will be preferred to use sealing means such as illustrated in Fig. 2. This includes seal 80 below ports 64 and 68, seals 82 and 83 between ports 56 and 60 and ports 64 and 68, and seal 84 above ports 56 and 60. These seals 80, 82, 83 and 84 may be O-ring seals or other types such as V seals. Seal 86 is provided in recess 88 at port 60 and likewise a seal 90 is provided in recess 92 of port 68. Seals 86 and 90 are preferably of the V type.

As hereinbefore disclosed, the pressure-proportioning "device operates on the principle of using differential areas exposed to the mud column pressures above the top packer and in the annular cell between the packers to move a floating piston which opens the proper valve ports'so as to distribute the pressure. For example, if it is desired for packers 26 and 28 to each support onehalf of the mud column load, that is, the pressure drop across packer 26 is to be equal to one-half the mud column load, then the area 94 of the top of the piston exposed to the pressure above the top packer would be one-half area. 96 of the bottom of piston 40 which is exposed to the pressure of the fluid in the annular cell 32 between the packers.

When the packers are initially set the hole is usually full of mud.- After the packers are set, the mud is blown 5 pressure in the annulus 30 above the top packer. It is thus seen that the product of the pressure of the fluid in -the annular cell 32 times area 96 of the piston is approxilmately twice that of the'product of the pressure of -the =--fl'uid* in annulus 30 times-the area- 94. Inthis caselthe piston will have axial movement upward. This causes recess 42 of the piston to align with ports 56 and 60 of the valved cylinder. This permits fluid to flow from annular cell 32 to the annular space 34 as the pressure in the annular space 34 is reduced by being removed therefrom by the air or gas. When the pressure in the annular cell 32 is equal to one-half the pressure in the annulus 30, it is seen that the upward and downward forces on the piston due to the fluid pressure in annulus 30 and annular cell 32 is equal. The resilient means such as springs 44 and 50 urges the piston downwardly into a neutral position thus stopping the flow of fluid from annular cell 32 through the valved body to the' annularspace 34. Springs 44 and 50 are preferably designed such that they are not under tension or compression when the piston is in a neutral position. The recess 42 in piston 40 is so positioned that at this neutral position it will be above ports 64 and 68 and below ports 56 and 60, as shown in Figure 1. It is also seen that at this point the passageway from the annulus 30 to the annular cell 32 is closed. If the pressure in an-- nular cell 32 should exceed one-half the pressure in annulus 30, it is obvious that the piston 40 will be urged upwardly as the pressure of the fluid in annular cell 32 times the area 96 is greater than the product of the pressure of the fiuid in the annulus 30 times the area 94. Recess 42 will'then be aligned with ports 56 and 60. Fluid isthen released from annular cell 32 to the annular space 34 below the bottom packer. When the pressure in annular cell 32 is reduced to one-half the pressure in annulus 30, the piston will once more be urged into its neutral position which, as shown in Figure 1, will effectively close the passageway means from the annular cell 32 to the annular space 34. If the pressure in annular cell 32 drops below one-half the pressure in annulus 30, it is obvious that piston 40 will be urged downwardly thus aligning ports 64 and 68 with recess 42. The pressure in annular cell 32 then builds up until it is equal to one-half the pressure in annulus 30 at which time the piston is returned to its neutral position closing the conduit means from annulus 30 to annular cell 32. It is of course understood that by varying the ratio of area 94 with respect to 96, any desired weight distribution can be accomplished between annulus 30 and the annular cell 32. It is also understood that additional packers and additional pressure-proportioning devices may be utilized together for any desired pressure distribution over any desired numb-er of packers.

When the piston moves upward, spring 50 is compressed and spring 44 is under tension; and, when the piston 40 moves downwardly, spring 44 is compressed and spring 50 is under tension. It is thus seen that both springs 44 and 50 tend to urge the piston into a neutral position. It is contemplated that the pressure required to move piston 40 from its neutral position is approximately five pounds. This inertia of the piston would have a negligible effect upon the proportioning of the load to the two individual packers when compared to the total load of the mud column which may be as high as 3,000 pounds per square inch for a 6,000 foot hole.

There are many uses for this proportioning device. One use contemplated is the drilling operation in which a different fluid is used as the circulating medium for removing the cuttings from that which is in the annulus behind the casing. In such a case, the drill string is suspended within the casing. The two packers support the mud column between the casing and the borehole wall with the mud serving primarily to seal the formations or prevent flow therefrom. The packers will be used to keep the mud load from being exerted upon the bottom of the borehole as the formation is being drilled. Air or other fluid is then circulated down through the drill string through the drill bit where it picks up cuttings and carries them back up to the surface through the annulus between the drill string and the casing. An exclaimed in US. Patent No. 2,338,670 issued to Sewell.

on January 4, 1944. Other uses for this system will be obvious to those skilled in the art.

It is to be understood that various changes and modifications in this invention may be made without departing from the scope thereof.

The invention claimed is:

1. In a drill string having spaced packers thereon for sealing off the annulus between the drill string and the borehole wall, pressure proportioning device mounted in said string intermediate said packers for controlling the pressure differential across the upper of said two vertically spaced packers which comprises a tubular body, a differential piston and cylinder assembly'mounted in the wall of said tubular body, said piston having opposite end portions with fluid pressure actuatable surfaces, the fluid pressure actuated surface on the first end portion of said piston having a lesser cross-sectional area than the fluid pressure actuated surface on the opposite end portion thereof; the wall of said cylinder being provided with a first port above said first end portion, second and third laterally spaced ports at a first intermediate level in said cylinder wall, fourth and fifth laterally spaced ports at a second intermediate level in said cylinder wall, and a sixth port in said cylinder wall below said opposite end portion of said piston, a first conduit interconnecting said first port with the exterior of said string of drill pipe above the upper of said packers, a second conduit inter-' connecting said fourth port with said first conduit, a third conduit interconnecting the exterior of said assembly between said packers with said sixth port, a fourth conduit interconnecting said second port with said third conduit, a fifth conduit interconnecting said fifth port with said third conduit, a sixth conduit interconnecting the exterior of said assembly below the lower of said packers with said third port; a transverse passageway in said piston intermediate its length positionable to intercommunicably connect said second and third ports in one extreme position of said piston within said cylinder and intercommunicably connect said fourth and fifth ports when in the opposite extreme position.

2. An apparatus as defined in claim 1 including biasing means tending to position said transverse passageway at a point intermediate its two extreme positions.

3. An apparatus as defined in claim 1 wherein said passageway is a circumferential recess around said piston.

4. In a drill string having spaced packers thereon for sealing off the annulus between the drill string and the borehole wall, a pressure-proportioning sub mounted in said string intermediate said packers for controlling the pressure differential across the upper of said two vertically spaced packers which comprises: a first cylindrical chamber in the Wall of said sub, said first chamber being provided with a first port in the upper end thereof, second and third ports laterally spaced at a first intermediate position along the wall of said first chamber, fourth and fifth ports laterally spaced along the Wall of said first chamber at a second intermediate position, and a sixth port near the lower end of said first chamber; a second chamber having a smaller diameter than said first chamber and coaxially aligned with and opening into said first chamber; a piston member having a first section in a sealing and slidable relationship within said first chamber and a second section slidable within said first and second chambers and having a sealing relationship with said second chamber, the first section of said piston having a transverse passageway intermediate its ends; first conduit means interconnecting the exterior of said sub above said upper packer with said first and fourth ports; second conduit means interconnecting the exterior of said sub between said packer with said second port and said sixth port; third conduit means interconnecting the exterior of said sub below said lower packer with said third port; a

fourth conduit means interconnecting said fifth port with said sixth port; said piston and said first chamber being further characterized such that said transverse passageway in said piston. is' positionable to intercommunicably' connect said second and third ports in one extreme position of said piston within said cylinder and intercommun'ic'ably connect said fourth and fifth ports when in the opposite extreme position. I I I 5. An apparatus as defined in claim 4 including biasing means to position said piston means within said first chamber with said transverse passageway at. a. point intermediate its two extreme positions.

6. An.apparatus as defined in claim 5 wherein said passageway is a circumferential recess around said piston.

7. In a drill string having spaced packers thereon for sealing oh the annulus between the drill string and the borehole wall, a pressure-proportioning device mounted inv said string intermediate said packer for controlling the pressure dififerential across the upper of said two vertically spaced packers which comprises: a tubular body, a differential piston and cylinder assembly mounted on the wall of said tubular body, said piston having opposite end portions with fluid pressure actuatable surfaces, the fluid pressure actuated surface on a first end portion of said piston having a lesser cross-sectional area than the fluid pressure actuatable surface on the opposite end portion thereof; the wall of said cylinder being provided with afirst port above said first end portion, second and third laterally spaced ports at a first intermediate level infsaid cylinder wall, fourth and fifth laterally spaced ports at a second intermediate level in said cylinder wall, and sixth I and seventh ports laterally spaced at a lower level in saidcylinder wall below said opposite end portion of said piston; a'first conduit interconnecting-said firstportwiththe exterior of said string of drill pipe above the upperof said packers and with said fourth portrasecondconduit interconnecting the exterior'of said-assembly be tween said packers with said secondport'andsaid sixthport; a fourth conduit interconnecting said fiftlr'port witlf said seventh port; a fifth conduit interconnecting thex terior of said assembly below the lower of said packer with said third port; a transverse passageway insaid pis ton intermediate its length positionable to intercommuni" cably connect said second and third ports in oneextreme References Cited in the file of this patent- UNITED STATES PATENTS 2,813,587 Mounce Nov. 19; 1957 Bierman Mar. 31} 1953 gym Ens-4

Images