US2621742A - Apparatus for cementing well liners - Google Patents

Description

Dec. 16, 1952 c. c. BROWN APPARATUS FOR CEMENTING WELL LINERS 3 Sheets-Sheet l Filed Aug. 26,k 1948 Emv C`. C. Bro wn INVENTOR.

ATTORNEY Filed Aug. 26, 1948 3 Sheets-Sheet 2 Dec. 16, 1952 C, C, BROWN 2,621,742

APPARATUS FOR CEMENTING WELL LINERS 30 Afro/:wir

Dec. 16, 1952 C, Q BROWN 2,621,742

APPARATUS FOR CEMENTING WELL ILINERS Filed Aug. 26, 1948 f 3 Sheets-Sheet 3 V C. C Bro wn /VVENTR A T TORNE Y Patented Dec. 16, 1952 UNITED STATES TENT OFFICE 2 Claims.

This invention relates to a method of cementing a liner in a well and to a novel plugging device for use therein.

In conventional methods of cementing a liner in a well, a section of pipe, commonly designated a liner, which is generally very much vshorter than the full length of the bore hole, is run into the bore hole on a smaller diameter string of pipe by means of which the operations of setting the liner are performed, and through which the cement is pumped for cementing the liner. Conventionally, the lower end of the operating string is inserted inside the upper end of the liner and releasably connected thereto by the usual liner setting tool. Such liners may be provided with an external hanger of conventional construction for supporting the liner on an outer string of casing or may be set in open hole, being supported directly from the bottom of the bore hole. When such a liner has been set at the desired point in the bore hole, cement will be pumped from the surface through the interior of the operating string (running-in string) and the liner, then forced up outside the liner to fill the annular space between the liner and the bore hole or an intermediate casing to the desired height above the bottom, after Which the operating string is Withdrawn and the cement allowed to harden. Conventional liner strings may also include packers for sealing the annular space between the liner and the bore hole or the intermediate casing string.

1n cementing such a liner by generally conventional methods, a slug of cement slurry of a predetermined volume calculated to ll the annular space surrounding the liner to the desired height, will be pumped through the interior of the operating pipe and into the liner from the lower end of which it will pass through a suitable back pressure valve into the annular space. As the interor of the liner string and the annular space will normally be lled initially with drilling mud which must be pushed ahead of the cement slug, the latter must be followed by a slug of a suitable hydraulic fluid, such as drilling mud, of a volume sulicient to displace the cement slug from the interor of the liner and force the cement up the annular space to the desired height While pushing the superimposed column of hydrostatic uid ahead of it. The back pressure valve is employed to prevent backflow of the external column during periods of unbalance of the hydrostatic heads outside and inside the liner string, due largely to the difference in the specific gravities of the cement and mud. In order to assure accurate placing of the cement along the exterior of the liner, great care must be exercised particularly in the calculation of the volume of the displacing fluid. If too great a lvolume is delivered into the cementing string, itV will force the cement slug too far up the annular space and, in the case of short liners, may pass completely above it. If too small a volume is used, the liner Will be only partially cemented and thevresulting cement seal in the annular space may be totally or partially ineffective for the intended purpose. Also, this may leave considerable excess residual cement inside the liner which must later be drilled out. Many failures in liner cementing have resulted from such errors in calculation of the requisite volume of the displacing slug.

In full string cementing, as distinguished from liner cementing, the pipe to be cemented extends from the bottom to the top of the bore hole. In this case, the pipe being of uniform diameter from top to bottom, the problem of accurate placing of the cement has been satisfactorily solved by inserting into the top of the pipe on top of the cement slug, a slidable plug, commonly called a cementing plug, which is then pumped down the pipe by'hydraulic pressure, forcing the cement slug ahead of it until the plug strikes some suitably placed abutment, generally in or near the bottom of the pipe string. The plug lodges on the abutment and effectively plugs the pipe. It also forms a separator between the cement and following mud and thereby prevents contamination of the cement by the mud. The resulting increase in back pressure, indicated on a suitable pressure gauge at the top of the well, serves to advise the operator that the cement slug has been fully displaced from the pipe. No special accuracy in calculation of the volume of displacing fluid is, therefore, necessary in this case.

This sliding plug method has not heretofore been considered to be possible of practical application to liner cementing due to the fact that the operating or running-in pipe is normally necessarily of substantially smaller diameter than the liner and no practical plugging device has heretofore been devised which Will be of Sulliciently small diameter to pass through the operating pipe, and which Will also efficiently seal the bore of the larger diameter liner when it has passed from the operating pipe into the liner.

Also, in the absence of such plugging means in liner cementing, it is often necessary to maintain high pressure in the internal column of fluid, during the time required for the cement to set and harden, to prevent return flow of the cement in the event the back pressure check valve in the liner should leak, a not-infrequent occurrence. The application of such high pressures often has very undesirable effects upon the cementing operation.

Accordingly, among the important objects of the present invention are the provision of an improved method for cementing liners which obviates or eliminates the diiiiculties and disad- 3 vantages of conventional methods; which assures greater accuracy and effectiveness in the placing of the cement in the annular space surrounding the liner; and which serves to keep the operator closely advised of the position of the cement slug at various stages of the cementing operation.

Another important object is the provision of a novel form of plugging device having great utility in the liner cementing method in accord- 'ance with this invention.

Other and more specific objects and advantages of this invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate useful embodiments in accordance with this invention.

In the drawings:

Fig. 1 shows a string of liner cementing tools in position in a well and arranged for cementing the liner in open hole in accordance with one embodiment of the method of this invention and showing the cement slug introduced into the cementing string;

Fig. 2 illustrates an intermediate stage in the cementing operation;

Fig. 3 illustrates the final stage in the cementing operation in which the cement slug has been pushed to its final position between the liner and the wall of the well bore;

Figs. 4, 5 and 6 together illustrate in somewhat enlarged detail the structure and arrangement of the string of tools employed in the embodiment illustrated in Figs. 1, 2 and 3, the positions of the parts of the string corresponding with that illustrated particularly in Fig. 1;

Fig. 7 illustrates in enlarged detail the lower end of the string showing the parts in the positions corresponding to those shown in Fig. 3; and

Figs. 8 and 9 illustrate the construction and arrangement of the parts of the liner cementing string as employed in accordance with another embodiment of this invention, namely, when cementing a liner inside an intermediate casing string.

Referring to the drawings: Fig. l illustrates a well bore I0 in which is inserted a liner II to be cemented therein. It will be understood that liner II may be of any desired length less than that of the well bore and will be of somewhat smaller diameter than the bore hole forming therewith an annular space I1 which is to be filled with cement, generally to a point near the upper end of the liner. Well bore I0, in this embodiment, is not lined with casing except for the upper end, which has the usual surface casing I2 which extends generally for a relatively short distance down the well bore and is provided with a conventional casing head I3 at the surface. A running-in string of pipe I4 of smaller diameter than liner I I extends through casing head I3 and is inserted into the upper end of liner II, being releasably connected thereto by means of a generally conventional liner setting tool, indicated generally by the numeral I5. The lower end of the liner is closed by a back pressure check valve I 6, of generally conventional design adapted to prevent the return of iiuid from annular space I'I into the interior of the liner. Conventional cementing equipment is connected in the usual manner to the upper end of the well in the normal manner and, as schematically illustrated, comprises a tank I8 adapted to contain the cement slurry employed for cementing the liner; a.

tank I9 adapted to contain displacing iiuid, generally drilling mud; and a header connecting the two tanks by means of valved branch pipes 2I and 22, respectively. A valved suction pipe 23 leads from header 20 to the suction of high pressure pump 24 which discharges into a header 25 from which a valved branch pipe 26 leads to the interior of pipe I4. A second valved branch pipe 21 connects to casing head I3 and communicates with the annular space between surface casing I2 and pipe I4. A valved pipe 28 is connected to the upper end of pipe I4 and communicates with the interior thereof and a valved pipe 29 is connected to the casing head and communicates with the annular space between surface casing I2 and pipe I4.

As previously indicated, the liner setting tool l5 is of well known and conventional construction adapted to form a releasable connection between the liner and the running-in pipe, and, as illustrated in the drawings, comprises a tubular body 30 having an internally threaded box member 3| at its upper end for connection of the tool to the lower end of the running-in pipe I4. Body I3 extends for a short distance into the upper end of the bore of liner II and is equipped with a series of downwardly facing resilient swab cups 32 adapted to form seals for the annular space between the liner and the exterior of body 30 to prevent the upward leakage of uid through this annular space. A sleeve 33 is screwed into the upper end of liner II and is provided with an internally threaded section indicated at 34. The upper portion of the setting tool body is provided with an externally splined portion 35 carrying a longitudinally oating externally threaded collar 36 engageable with threads 34. A swivel 3'i is arranged between the upper end of sleeve 33 and an external shoulder on box member 3| of the setting tool. rljhe arrangement of the threaded -connection between collar 36 and sleeve 33 is such that when pipe I4 is rotated in the appropriate direction, collar 3S will unscrew from threads 34 and by reason of its floating arrangement on splined portion 35, will move upwardly thereon until it becomes disconnected from sleeve 33 whereby pipe I4 and the setting tool may be withdrawn from liner -I I. It will be understood that the specific form of setting tool forms no part of this invention, it being necessary only to provide a releasable connection between the liner and the runningin string which may be of any of the conventional forms.

A tubular sleeve 38 is detachably connected to the lower end of body 3B by means of shear pins 39. Sleeve 38 has mounted on the exterior thereof a resilient sleeve 40 having upwardly and downwardly directed ilexible lips 4I and 42, respectively, which are adapted to form fluid tight seals in the annular space between sleeve 3B and liner II when exposed to fluid pressure. The lower end of sleeve 38 carries a slip ring 43, the exterior of slip ring 43 being provided with upwardly facing teeth 44. An annular abutment =45 is formed in the bore of sleeve 38 near its lower end and carries downwardly facing teeth 46. A plurality of passageways 41 extend through the wall of the upper end of sleeve 38 to provide communication between the interior thereof and the annular space between setting tool body 30A and liner Il above resilient sleeve 40. An annular latching abutment 48 having teeth 43 engageable with teeth 44 of slip ring 43, when the latter is forced inside abutment 48, is mounted in the bore of liner II generally adjacent its lower` end and atsome pre-determined distance above valve IB. Passageways 50 extend longitudinally through the body of abutment 4B.

A plugging element, indicated generally by the numeral 5|, is employed in cooperation with sleeve 38 to form a composite cementing plug for liner II, and comprises an elongated generally cylindrical solid body 52, constructed of flexible, resilient material, such as rubber or rubber composition, and adapted to form a slidable seal for the bore of running-in pipe I4 and liner setting tool I5. Body 52 may be provided, as illustrated, with a plurality of vertically spaced, upwardly flaring flexible lips 53, of varying diameters which are adapted to maintain sealing engagement with the bores of the pipe and setting tool during downward passage of the plugging element through the bores of these elements, despite any variations in the diameters of these bores. The lower end of body 52 is rigidly connected to a metallic slip ring 54 adapted to enter the bore of sleeve 33 and carrying toothed slips 55 engageable with teeth 45 to firmly lock these elements together. Body 52 is adapted to follow slip ring 54 into the bore of sleeve 38 above abutment 45 and tightly plug the bore of sleeve 38, in a manner to be described in detail hereinafter.

The cementing of the liner in an open hole in accordance with this invention is conducted in the following manner: The cementing string is made up in the form substantially as above described and as illustrated particularly in Figs. l to '7 exclusive. The string will be inserted into the well bore through casing head I3. As noted previously, liner |I may be of any desired length and running-in string I4 will be of sufcient length to extend to the surface when valve I6 rests on the bottom of the well bore. The setting tool will now be released from the liner in the conventional manner by rotation of pipe I4 in a direction such as to unscrew floating nut 35 from its engagement with sleeve 33. Pipe string I4 and the attached setting tool may now be lifted a short distance to assure that it is released from the liner, without, however, withdrawing setting tool body 3!) from the upper end of the liner. A slug or a suitable cement body 5l of a slurry will now be withdrawn from tank I8 through pipes 2| and 23 by pump 24 and pumped through header and pipe 26 into the bore of cementing pipe I4. It will be understood that during this stage of operations the valve in pipe 22 will be closed as will the valves in pipes 21 and 28, while the valves in pipes 2|, 23, 26 and 29 will be open. A volume of cement slurry sufficient to fill annular space I'I to the desired height will thus be pumped through pipe I4 into liner I I.v As the annular space, as well as the interior of the cementing string, will normally be filled with drilling mud, water or well fluids, the cement slurry, which is normally of higher specific gravity than such fluids, will displace the latter from the interior of the cementing string and up the annular space to the surface where it discharges from the casing head through pipe 29. The downwardly opening swab cups 32 will effectively prevent any back-flow of the cement past the setting tool. When all of the cement slurry has been introduced into pipe I4, plugging element 5I will be inserted into the pipe on top of the I' column of cement. (See Figs. 1 and 4.) Thereupon the valve in pipe 2| will be closed and Athe valve in pipe 22 opened and a quantity of displacing fluid 58, such as conventional drilling mud, will be withdrawn from tank I9 and pumped into pipey|4 on top of the column of cement standing in the cementing string. A s the displacing fluid is pumped into pipe I4, itA will force the column of cement downwardly in the pipe and will `also force plugging element 5| downwardly in its position between the two bodies of fluid. Introduction of the displacing fluid is continued until plugging element 5I enters sleeve 38. The pressure applied to the upper end of body 52 of the plugging element will drive slip ring 54 and slips 55 over teeth 46 in the bore of sleeve 38, body 52 lodging against abutment 45 and body 52 entering the bore of sleeve 38. When this occurs, plugging element 5| will tightly seal the bore of sleeve 38, the column of displacing fluid acting on the upper end thereof and on lips 53 to compress and expand them into tight sealing engagement with the inner wall of sleeve 38. (See Fig. 2.) This will, of course, set up resistance to the further introduction of displacing fluid into pipe I4 and will increase the back pressure on pump 24. This increase in back pressure will immediately be evidenced on the usual pressure gauge 56 on the pump die charge and will immediately advise the operator that the top of the cement slug has now reached the lower` end of the setting tool and is entirely inside the liner. The pump pressure will be permitted to be built up against plugging element 5I to a point at which shear pins 39 will be broken, thereby releasing sleeve 38 from its connection to the lower end of the setting tool. The shearing of pins 39k will likewise be evidenced at the surface by an immediate reduction in pressure on gauge 56. As the pumping continues, sleeve 38, into which plugging element 5I is now rigidlyl locked, will be forced downwardly -by the pressure of the displacing fluid, the pressure being exerted, of course, against the upper end of plugging element 5I and against lip 4I of sealing sleeve 40, whereby the composite plug will form a tight sliding seal in the bore of liner II under the pressure of the displacing fluid. As the composite plug is driven downwardly through the liner, it will displace the column of cement through valve I6 and thence upwardly through annular space I'I unti1 slip ring 43, on the lower end of sleeve 38, enters latching abutment 48 and teeth 44 will become inter-locked with teeth 49 carried by the abutment. (See Figs. 3 and 7.) This will, of course, stop further downward movement of the plug and will again increase the back pressure against pump 24, the resulting reaction on gauge 56 advising the operator that the cement slug has now been displaced to the desired point from the liner and, therefore, to the desired height outside the liner. The engagement of the composite plug with abutment 48 forms a tight plug in the lower end of the liner which will prevent the return movement of the cement into the interior of the liner, should back pressure valve I6 fail to hold. Pipe I4 and the setting tool may now be withdrawn from upperend of the liner and, if desired,v circulation of the displacing fluid or of the mud, may be reversed by closing the Valves in pipes 26 and 29 and opening the valves in pipes 21 and 33, whereby the displacing fluid may be circulated down through the annular space between pipe |4 and the well wall and thence upwardly through the interior of the now open end of the setting tool and thence upwardly through the bore of pipe I4 to the surface and out through pipe 28. By means of this reverse circulation any jlinerf and casing 62;

excess cement remaining above the upper end of the liner may be washed out of the well Without in any way disturbing the column of cement in annular space l1. Pipe I4 and the setting tool may now be withdrawn completely from the well .and the cement allowed to harden thereby completing the cementing operation.

Passageways 41 in sleeve 38 serve as pressure relief ports to permit any fluid which may tend to become trapped between lip 4l and swab cups 32 to discharge into the bore of the cementing string, and will thereby prevent the building up of Vsufficient hydrostatic pressure on the upper end of sealing sleeve 40 as might prematurely break shear pins 39. When plugging element 5| has been forced into the bore of sleeve 38, body 52 and lips 53 will effectively seal passageways 41 so that the full pressure of the displacing fluid will then be exerted on the composite plug.

When the composite plug has been locked into latching abutment 48, as previously described, passageways 50 will permit exertion of the back pressure of the cement column below the plug, particularly in the event of leakage through valve I6, against flexible lip 42 which will thereby be expanded and compressed tightly against the wall of the liner and thereby assure a tight shutoff under all conditions.

It will be seen that by the method above described, it will no longer be necessary to depend upon careful metering of the displacing fluid to assure proper placement of the cement. Positive signals in the form of increases in gauge pressure at the surface are provided, as described, to inform the operator first, when the top ofthe cement slug has entered the upper end of the liner and second, when it has been fully displaced to the desired point in the lower end of the liner.

By the use of the two-part plug, the walls oi the cementing string and liner will be wiped clean of cement andthe insertion of plugging member 5I between the inter-faces ofthe slugs of cement and displacing fluid will prevent any serious contamination of the cement by the displacing fluid and thus assure a better cementing jOb;

rPhe metallic parts of sleeveV 38 and plugging member 5| will ordinarily be constructed of a relatively soft easily drillabler metal, suchl as brass or aluminum, so that they may be readily drilled out when, if desired, aV drill is runinto thel liner to drill out the cement plug remaining in and below the composite plug.

Shear pins 39 are ordinarilyv designed to break at some pre-determined pressure in excess of that normally usedinforcing the cement slurry into position. Pins designed to shear under about 750 pounds per square inch have been found` to' be suitable in the described cementing.. operation.

Fig. 8 illustrates more or less schematically the form of cementing string whencementingalin'er 'inside an intermediate string of casing.` In this embodiment a conventional liner hanger` 60' and apacker 6I willbe connectedinto the. cementing string at the upper end' of' the liner and will be operated in the conventional manner` to hang the` liner at any desired` point along theintermediate casing string 62 and' to expand the packer to form a seal in the annular space between the InV all otherv respectsl the cementing operation will be conducted in the manner previously described.

It will be understood the various alterations and changes may be made in the detailed steps of the method and nin the form of the apparatus heretofore described within the scope of the ap- 'pended claims but without departing from the spirit of this invention.

V What I claim and desire to secure' by Letters Patent is:

l. A plugging device for awell pipe, comprising, a body member insertible for sliding movement in a well pipe, said body member being composed o1 a tubular metallic sleeve having a resilient sleeve mounted onthe exterior thereof, the upper and lower ends of said resilient sleeve having respective upwardly and downwardly outwardly flaring exible lips p'eripherally engageable with -the wall of said pipe, passageways through the wall or said metallic sleeve providing communication between thel interior thereof and the exterior thereof above the upper one of said lips, a solid resilient plug` ymember insertible inthe bore oi said metallic sleeve to close said passageways and to form with said body member a duid-tight composite plug for said pipe, locking means arranged between said metallic sleeve and said plug member for locking said members together, and a second locking meansV carried by the lower end oi said metallic sleeve for irreversible locking engagement by a cooperating locking element mounted in said pipe in the path of movement of said body.

2. A plugging device for a Well pipe, comprising, a body member insertible for sliding movement in a well pipe, said bodyv member being composed of a tubular metallic sleeve having a resilient sleeve mounted. on the exterior thereof, the upper and lower ends of said resilient sleeve having respective upwardly and downwardly outwardly haring flexible lips peripherally engageable with the wall oi said pipe, passageways through the' wall of said metallic sleeve providing communication between the' interior thereof and the exterior thereof above the upper one of said lips, a solid resilient plug member insertible in the bore of said metallic sleeve to' close said passageways and to form with. said' body member a fluid-tight compositev plug for said' pipe, locking means arranged between said metallic sleeve and said plug member forv locking said members together, and' a second locking means including an externally toothed slip ring carried by the lower end of said metallic sleeve for irreversible locking engagement by a cooperating lockingelement mounted in the pipe'in the path of movement of said body.

CICERO- CL BROWN'.

REFERENCES CITED rlhe following references are' of record' in the le of this patent:

UNITED STATES PATENTS Number Name Date l',790,450 rfor-rance' Jan. 27, 1931 1,856,038 Johnson July 5, 1932 2,164,190 Klomp' June27, 1939 2,169,569 O-Donnell .Aug. 15, 1939 21,310,483 Wickersham Feb, 9, 1943 2,481,422 Haynes et al. Sept. 6, 1949

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