US2308072A - Method of cementing oil wells - Google Patents

Description

Jan. 12, 1943.

P. H. GRANGER METHOD OF.v CEMENTZING OIL WELLS Filed My 27, 1941 l m y. 6R E o NOM 3 Ww m r .v

EN a M H MNM, Y m

Patented Jan. 12, 1943 UNITED `STATES PATENT oFI-ICE METHOD F CEMENTING OIL WELLS Paul Il. Granger, Los Angeles, Calif.

Application May 27, 1941, 'Serial No. 395,370

(Cl. 16B-22) 2 Claims.

This invention relates to a method of placing cement through openings in oil well casings.

It has been common practice for some time to place cement through an opening in the casing by means oi a tool suspended from a tubing and provided with spaced packers adapted to seal off a zone in the casing in which the opening is located. The term tubing is used herein to denote a conduit such as a string of pump tubing or drill pipe. Such a cementing operation may be carried out, for example, for the purpose of sealing oif around an opening caused by failure of the casing. In other cases, an opening or a plurality of openings may be purposely made in the casing adjacent a water-bearing stratum so that cement may be forced through the opening or openings into the well around the casing and into the structure to eifect a water seal.

Cement is forced down the tubing and into the` tool so as to flow through the localized zone and out through the opening or openings in the casing into the well and the surrounding formation so as to seal the formation andclose the openings.

It has been common practice to remove the tool from the position of the opening or openings immediately after the cementing operation has been performed, usually by moving the tool upwardly in the casing, in order to prevent the tool from becoming stuck due to formation of -a bond between cement remaining in the localized zone and the cement outside the casing at said position. Under such circumstances there is a decided tendency for cement to flow back through the opening into the casing, sometimes to such an extent that the cementing job is ineaective.

Usually some cement remains in the tool, particularly in the localized zone of the casing sealed off between the packers after the required amount of cement has been forced through the opening. According to some practices the cement remaining in the tool is not forced out or is not perfectly flushed out before the tool is brought to the surface on the tubing string. There is, therefore, a decided tendency for the tool to become jammed in the casing dueto the setting of the cement remaining in the tool and particularly in the zone of the casing sealed olf between the packers.

The term cement is used herein in a broad sense, to include Portland cement, special types of "oil well" cement such as are in common use in well-cementing operations, and other hydraulic cement materials, and, in general, any

material which is adapted to be placed while in fluent or plastic condition and to set or harden to a relatively solid or rigid condition upon standing for a suitable period of time.

A particular object of the invention is to provide a cementing method which prevents the back ilow of cement into the casing after the cement has been forced out through the opening in the casing into the surrounding formation.

Another object of the invention is to provide for the flushing out of excess cement from the tool while preventing the back flow of cement into the casing through the opening which has been cemented.

A further object of the invention is to provide `for the substantially complete removal of cement from the zone in the casing between the spaced packing means after the desired amount of cement has been forced through the opening in the casing.

Further objects and advantages of the invention will become apparent as the description proceeds.

. In the placing of cement through an opening in the casing of a well with a tool suspended within the casing from a tubing and provided with vertically spaced packing means for sealing olf a portion of the casing therebetween, the tool is rst brought into position to seal off between the packing means a localized zone of the casing containing the opening. The tool is preferably positioned with the lowermost packing means adjacent the opening.

Tools of this type are provided with one or more cement ports providing communication between the space between the packing means and the tubing string. For reasons that willi, be brought out subsequently, the cement port or ports are preferably located adjacent the lowermost packing means.

Cement is then forced down the tubing into the localized zone and through the opening. According to one practice of the invention, especially in situations where considerable cement is liable to accumulate in the localized zone, liquid is then forced down the casing around the tubing, through the localized zone, and out through the tubing to substantially completely remove cement from the localized zone. It is preferable that the tool be maintained in the same position during the cementing and flushing operations.

In some situations, especially when using a tool which has a cementing port closely adjacent the lower packing means and when such tool is located with the lower packing means adjacent the cement around the opening has taken at least' an initial set'. This substantially prevents any back ilow of cement through the opening into the casing.

After the tool has been retained in position the within the body II and providing communication betwen the localized zone as at 23a and the space in the casing above the uppermost packing means as at 23D. 'Ihe tube is shown provided with check valve means such as avalve member 24 mounted on aspring arm 25 and desired length of time, substantially the wholeV tool, including the packing means is moved vertically to a different position in the casing, as upwardly to the earthssurface.

I have illustrated examples of apparatus which may be used for carrying out my invention in the accompanying drawing, and referring thereto:

Fig. 1 is a partly sectional elevational view of an oil well with apparatus for cementing therein;

Fig. 2 is a longitudinal section of a cementing4 tool such as illustrated in Fig. 1; and

Fig. 3 is a longitudinal section of a portion of the tool illustrated in* Fig. 2, modified by the addition of a check valve.

Referring to Figs. 1 and 2 of the drawing, a bore hole is indicated at I and is shown provided with acasing 2, havingopenings 3 and 4 therein through which cement is to be placed. Acementing tool 5, shown in detail in Fig. 2, is suspended within the casing on a tubing 6 such as a string of drill pipe or pump tubing, and is provided with spaced packing means such as upper and lower packing cups 'I and 8 which are adapted to seal with the inner walls of thecasing 2 to seal '01T a localized zone in the casing `therebetween as indicatedl at 9. .The tool 5 is shown as comprising a generally cylindrical body member I I to which thepackers 1 and 8 are suitably attached at vertically spaced positions. For example, the uppermost packer 'I may be held in position between a ring I2 secured to the body Il and a conical ring I3 forced toward the ring I2 by means 'of a compression nut I4. Thelower packer 8 may be held in position by a similar construction. The body II is suspended from the tubing 6 by means of a reducing coupling I5 which threadedly engages the tubing and the body.

The lower end of the tool is closed by vmeans ofa partition I6. This partition is shown abutting the lower end of the body member II to which a collar I'I is threadedly secured. A cap member I6 is'shown threaded to the collar I'I and in contact with the partition I6 to hold it in tight engagementwith the lower end of the body member I I. The lower end of the cap member I8 is provided with an opening I9 below thelower packer 8 through which liquids may flow.

The tool is further provided with a by-pass 2| which extends fromthe partition I6, where it communicates with the opening I9, upwardly within the member II and thence outwardly through the wall of the member II as at 22 at a position above theupper packer 1. The tube 2I provides for by-passing4 liquids between the spaces above and below the packing means during vertical movement of the tool in the casing. Such by-passing is generally necessary in view of the tight t the packing means makes with the casing.

Another tube is indicated at 23 extending adapted to maintain the tube 23 closed when the pressure within the localizedzone 9 exceeds the pressure in the space in the casing above the uppermost packing means 'I. Thevalve 24 is adapted to open the passage 23 when the pressure in the space in the casing above the uppermost packing means exceeds the pressure in the localized zone.

The packers I and 8 may be of any suitabletype adapted to maintain a fluid-tight seal with the walls of the casing against pressure within the localized zone between lthe packers, so as to 'prevent ilow of cement past the packers in cementing operations such as described hereinafter. If the upper packer .1 is of a type which will also maintain a. fluid-tight seal when the pressure within the casing above the packer exceeds the pressure between the packers, and if it is desired to remove excess cement from the localized zone by introduction of a. ushing liquid down the casing as described hereinafter, then it is necessary -to provide some means such as the passage 23 and checkvalve 24 for permitting such flushing liquid to ow downward past the position of the upper packer and into the localized zone., However, the tool is shown as provided with packers of the type comprising flexible cups of rubber or the like, facing-inv wardly toward each other, so as to maintain a tight seal by expansion thereof against the casing when the pressure in thelocalized zone between the packers exceeds the pressure above and below such localized zone. When using flexible packing cups of this type, it may not be necessary to provide means such as passage 23 for permitting downward ow of ushing liquid past the upper packer, because the upper packer may be constructed so as to yield sufciently upon excess pressure from above to permit the flushing liquid to ow down between the packer and the casing. v

The tool is further provided with-acement port 26 which provides communication between the inside of the member II and the localized zone between the packers.4 Although more than one port may be employed, I prefer that any -cement port providing .such communication be located closely adjacent the lowermost packing means and preferably at a position below the uppermost edge of such packing means.

It may be assumed that the position of theopenings 3 and 4 is known, as from casing records or as the result of forming said openings at a known depth, or has been located by well-known leak-locating' procedures. The tool is brought into position to seal oil? between the packers `I `and 8 the localizedzone 9 in the portion of the casing containing theopenings 3 and 4. The tool is preferably so positioned as to place thelower packer 8 as close to thelowermost opening 4 as is possible. Wh'ile lowering or raising the -tool into the hole on the tubing the liquid in the cas- .ing is by-passed through the tool through the between the pump and the casing. The conduit 29- is shown with adischarge valve 30 connected thereto between thevalve 32 and thehead 21,

and with apressure gauge 3| located between the.

valve 30 and the head, for indicating the pressure in the casing. Aconduit 33 is shown connected to the upper end of the tubing string 6 and leading to a suitable pump not shown. A shut-off valve is shown at 34 in theconduit 33 and ya dischargevalve 35 is connected to said conduit between thevalve 34 andthe tubing string.llhe conduit 33 is further provided with apressure gauge 36 located between the tubing string and the valve v35. The cementing head includes a packing gland2la for preventing leakage around the outside of the tubing.

` To place cement through theopenings 3 and 4, a suitable cementing material in fluent form, such as a Portland cement slurry, is introduced into theconduit 33 and pumped down the tubing string 6 where it enters the body of the tool 5 and is discharged therefrom through thecement port 26. The cement then flows over thelowermost packer 8 and out through theopening 4, or through bothopenings 3 and 4, into the space around the outside of the casing and into the formation, at the position of the openings and for some distance below and above the openings.

The total amount of cement to be forced down the tubing is determined before the cementing operation is begun, the amount being dictated by knowledge of the situation and experience. When the desired amount of cement has been pumped into the tubing, water or other fluid is introduced and pumped down the tubing to force the remaining cement down to the tool. Suitable Wellknown means is employed for indicating the arrival'of the last of the cement at the tool. Usually a certain amount of liquid is forced down the tubing after this to clear the tool and place as much of the cement as possible through the opening or openings.

Generally when cementing a plurality of ver, tically spaced openings such as theopenings 3 and 4, there will be considerable cement left in the tool at the end of the cementing operation. This cement may be flushed from the tool by pumping liquid into the casing through the conduit 29 while the tool is maintained in position with the packers on opposite sides of the open-f ings in the casing.

Under ordinary4 circumstances the'pressure in the localized zone produced during the cementing operation is somewhat greater than can be Withstood by the casing at positions adjacent the surface. Hence, if an attempt is made to force liquid down the casing from the conduit 29y at a pressure in excess of the pressure which has been established in the localized zone during the cementing operation, there is a good possibility that the upper portions of the casing will rupture. Before starting such circulation, it is therefore preferable to bring the pressure in the localized zone to a level which the casing can withstand. This may be accomplished by opening thevalve 35 and reducing the pressure to a desired Value as indicated by thepressure gauge 36. Since the tool is maintained at the localized cementing zone and the tubing is full of liquid remaining therein at the completion of the cementing operation, the fluid pressure in the localized zone is maintained at least equal to the hydrostatichead of the column oi liquid in the entire length of tubing above the tool, and the maintenance of this pressure at the position of theopenings 3 and 4 serves to prevent back flow of the cement through the openings into the localized zone. By openingvalve 35, the pressure in the localized zone may be reduced to any desire pressure equal to'or greater than such hydrostatic head.

The liquid forced down the casing passes into the localized zone past the position of the upper packing means 1,- either directly between the packer and casing, orthrough the tube 23, since excess pressure from above opens thevalve 24. This liquid flows downwardly through the localized zone and flushes any excess cement out of the zone through thecement port 26 and upwardly through the body and the tubing 6 from which it is discharged through theconduit 33. Since there is no communication between the interior of the tubing 6 and the space within the casing around the tubing. except through the above described path leading through the localized zone between the packing means and thence through the tool body, the flow of the flushing liquid from the casing into the tubing takesplace substantially wholly through the localized zone, thus ensuring removal of cement from said localized zone While maintaining in'said zone a fluid pressure at least equal to the hydrostatic head of the column of liquid in the entire length of the tubing above the tool. By using a tool in which the cement ports are located closely adjacent the lowerymost packing means, such reverse circulation will substantially completely remove from the localized zone all cement remaining therein at the completion of the cementing operation. Any cement in this zone will flow or be carried by the `flushing liquid to the lower end of the zone, and since the flushing liquid is forced to flow` downwardly to the position of .port 26 in order to leave the zone, ai thorough scavenging action is ensured. If cement is left between the tool and the casing it will normally be located within the lowermost cup and just below thecement port 26. Such cement, even if allowed to set, will not prevent subsequent movement of the tool.

The tool is preferably maintained in the cementing position until the cement around the openings in the casing has taken at least an initial set and the above-mentioned fluid pressure is preferably maintained in the localized zone throughout that period. During at least part of that period, and preferably during the first part thereof, the above-mentioned flushing procedure is conducted while maintaining the tool in said cementing position in order to maintain pressure on the cement and give it a chance to set without back flow or channeling.

As illustrated in Fig. 3, the tool may, if desired, be provided with means for preventing down flow through thetube 2| during a flushing operation such as described above. In Fig. 3 the tool is shown modified by the provision of avalve cage 4| suitably secured in the member I8 and containing aball 42 held seated in anopening 43 by means of acompression spring 44. Theball 42 is raised from theopening 43 by upward pressure against it, upon downward movement of the tool, to provide for the upward flow of liquid through the tool from the opening |9 to theopening 22. An excess `of fluid pressure from above as communicated from theopening 22 will force the ball down and close thepassage 43,

preventing the downward flow of liquid through the tube 2l. l l

In some cases the tool may be left in position for several hours after the cement has taken an initial set. The tool, including the spaced packers, after being maintained in position for the desired interval, is then moved vertically in the casing either to the surface or to a position to cement other openings. It is not necessary to disintegrate the packers, as by reaming, in order to move thetool at the completion of the cementing operation.

It will be assumed that general good practice will be followed in placing the cement in the openings to be cemented. Other tools which are suitable for practicing the method of this invention are disclosed and claimed in my copending applications Serial Nos. 347,697 (Patent No. 2,248,169) and 383,589, led July 26, i940, and March l5, 1941, respectively.

My invention is subject to considerable modiflcation, hence I do not choose to be strictly limited to the above illustrative examples, but rather to the scope of the appended claims.

I claim:

1. In the placing of cement through an opening in the casing of a well with a tool suspended Within the casingy from a tubing and provided with vertically spaced packing means for sealing ot a localized zone in the casing therebetween, said tubing being adapted to communicate with the localized zone, the Asteps which comprise: bringing the tool into position in the casing with the packing means located at opposite sides of the opening in the casing to seal olf a localized zone in the portion of the casing containing the opening; forcing cement down the tubing into the localized zone and through the opening; and

thereafter, while maintaining the tool positioned;

with the packing means located at opposite sides of the opening, forcing liquid down the casing around the tubing, through the localized zone, and up through the tubing, the flow of said liquid from the casing into the tubing beingsubstantially wholly through said localized zone between the packing means, whereby cement is substantially completely removed from said zone by the flushing action of said liquid While maintaining in said zone a fluid pressure at least equal to the hydrostatic head of the liquid in the entire length of the tubing above the tool.

2. In the placing of cement through an opening in the casing of a Well with a cementing tool f of the type suspended within the casing from a Cil tubing and provided with upper and lower packers sealing with the interior of the casing at vertically spaced positions to seal oil a portion of the casing therebetween, and having a cementing port providing communication between the tubing and the portion of the casing between the packers, the steps which comprise: bringing -the tool into a cementing position to seal olf a localized zone in the portion of the casing containing the opening; forcing cement down the tubing through the cementing port and through the localized zone into and through the opening; and thereafter retaining the tool in said cementing position until the cement around the opening has taken at least an initial set, while maintaining the tubing full of liquid to maintain in said zone a fluid pressure at least equal to the hydrostatic head produced by the liquid in the tubing; and during at least part of the time said tool is so retained in said cementing position, forcing liquid down the casing around the tubing and into the localized zone, and thence through the cementing port and up through the tubing, the ow of said liquid from the casing into the tubing being substantially -wholly through said localized zone between the packing means, whereby cement is substantially completely removed from said zone by the i'lushing action of said liquid while maintaining such fluid pressure in said zone.

PAUL H. GRANGER.

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