US3171481A - Method of multiple string open hole cementing including the step of sealing off the annulus - Google Patents

Description

March 2, 1965 c. c. BROWN 3,171,481

METHOD OF MULTIPLE STRING OPEN HOLE CEMENTING INCLUDING THE STEP OF SEALING OFF THE ANNULUS Filed Aug. 22, 1962 (RGG ATTOEA/EYS United States Patent 0 METHOD OF MULTIPLE STRING OPEN HOLE CE- MENTING INCLUDING THE STEP 0F SEALKNG OFF THE ANNULUS Cicero C. Brown, Brown Oil Tools, Inc., R0. Box 19236, Houston, Tex. Filed Aug. 22, 1962, Ser. No. 218,660 6 Claims. (Cl. 166-28) This invention relates to cementing of wells and particularly to open hole cementing of wells in which are disposed a plurality of pipe strings.

In recent years in the oil and gas well industry a form of oil and gas well completions, commonly known as tubingless completions, have become widely used. In this type well completion, the usual surface casing is set to a relatively shallow depth and the well bore is then drilled to the desired depth necessary to intersect a plurality of producing zones. To complete the several zones for production, a number of tubing strings, depending on the number of zones to be completed, will be run into the well bore, the pipe strings being usually of differing lengths, depending on the depth of the zone with which each is to be connected, All of the pipe strings are then cemented in the open hole by pumping cement down one of the strings and up around all of the others in the well bore until the cement fills the interval between the bottom of the bore hole and the end of the surface casing. Usually an excess of cement is pumped in in order to raise the level of the cement in the well bore to a point above the bottom of the surface casing to insure a tight seal with the surface casing. One difficulty is experienced with this method in that the earth formations comprising one or more of the zones may break down after the cement has been pumped to the proper height, due to the hydrostatic pressure which will be exerted thereon by the column of cement and well bore fiuid, with the result that such zone or zones will take all of the cement pumped above such zone or zones and thereby prevent elfective cementing to the desired elevation in the bore hole. Such zones are commonly referred to in the drilling industry as thief zones.

Accordingly, it is a primary object of this invention to provide a cementing method for multiple pipe string completions which obviates the difliculty mentioned above.

In accordance with this invention, a cementing method for multiple string wells is provided which includes the step of sealing-01f the well bore about .the several pipe strings at a point above the production zones subject to breakdown, in order to relieve those zones of the excessive hydrostatic pressure from above, and thereby obviate the possibility that any of the zones which are to be cemented will break down and cause ineffective cementing, as described above.

Further, in accordance with this invention, as the in troduction of the cement is completed, the zones are additionally relieved of the hydrostatic heads of fluid generally present in the bores of the several pipe strings and this additional step further assures effective relief of the zones from any excessive hydrostatic pressures.

A further object is to provide a system for multiple pipe string open hole cementing, including a hydraulic pressure actuated packer, for accomplishment of the principal objects mentioned above.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates a useful embodiment in accordance with this invention.

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In the drawing:

FIG. 1 is a diagramamtic view of a well equipped with at least two pipe strings for effecting production from at least two zones, showing one stage in the cementing operation with the packer unset; and

FIG. 2 is a view similar to FIG. 1, showing the packer set and the cementing operation completed.

Referring to the drawing, there is shown a well bore W which has been drilled through upper and lower producing zones, designated Z and Z respectively.

The usual surface casing C is shown installed in the upper portion of the well bore and equipped at the surface with a conventional wellhead H in which two parallel strings of tubing T and T are supported. The wellhead equipment for enclosing and supporting the upper ends of the tubing strings is entirely conventional and the details thereof do not form a part of this invention. The upper end of casing C is equipped with a valved outlet 0. The tubing strings are equipped at the surface with control valves V and V respectively. Both tubing strings are connected to a hydraulic pressure-actuatable packer P of any suitable and known form. The form of the packer herein illustrated is described in detail in my copending application Serial No. 857,739, filed December 7, 1959, now Patent 3,068,942. The details of the packer do not form a part of this invention but the system herein described desirably includes such a fluid-pressure actuated packer in order to permit setting of the packer without manipulation of the tubing strings. As illustrated, the packer comprises a generally cylindrical body 10 having a pair of longitudinally extending parallel passageways 11 and 12 coaxial, respectively, with tubing strings T and T which are screwed into the upper ends of the respective passageways. The lower ends of the passageways receive the lower sections T and T of tubing strings T and T respectively. Packer P carries an annular resilient seal element 13 aotuatable by endwise compression to be expanded and maintained in sealing engagement with the wall of well bore W to thereby seal-off between the packer body and the bore wall. To effect the endwise compresison, the lower end of the seal element is secured to a stationary abutment 14 formed on the exterior of the packer body and a sleeve piston 15 is secured to the upepr end of the seal element. The upper end of the packer body 10 carries an annular enlargement which forms a cylinder head 16 about which the skirt of sleeve piston 15 will be slidably disposed. Cylinder head 16 carries an annular packing 17 to slidably seal with the bore of sleeve piston 15. The end of sleeve piston 15, which is secured to the upper end of seal element 13, carries an internal annular piston head 18 slidably disposed about the packer body below cylinder head 16 to define therebetween the expansible pressure chamber 19 which is in communication with passageway 12 through radial ports 29 opening through the wall of body 10. Seal packing 21 is disposed between piston head 18 and the exterior of body 10 to form a slidable seal between these members. Lower section T of tubing string T extends through zone Z and will eventually form the connection for production from that zone to pipe string T Lower section T has mounted in the bore thereof a shear sleeve 22 which is secured thereto by means of a shear pin 23. The upper end of sleeve 22 defines a valve seat adapted to receive a closure ball 24 by means of which the bore of tubing string T may be closed below ports 20, as will subsequently appear. Just above shear sleeve 22, the bore wall of lower Section T; is provided with a plurality of plug anchoring teeth 25, for purposes also to be described hereinafter. Lower section T of tubing string T which will eventually form the connection for production from zone Z to pipe string T carries a valve cage 26 in which is disposed a downwardlyclosing check valve'27 cooperating with a port 28. The lower end of valve cage 26 is secured to a length of screen pipe 29 which may take a portion of the cement; during the cementing cycle.

The cementing operation is conducted in the following manner: At the beginning of the'operation, valve V will be closed and pipe string T will be filled with well fluid or drill-ing mud which will be held. therein. by closing of check valve 27. A first quantity of cement M the volume of which is predetermined in the conventional manner to be sufficient to fill the well bore annulus about both pipe strings from a point just below the lower end-of lower section T to a point above the lower end of easing C, will be introduced into. the well bore through pipe string T fluid and closed-oil at valve V the body of' cement M cannot enter this pipe string and will, therefore, only displace the portion F of fluid in the well bore which extends above the lower end of lower section T Closure ball 24 will be inserted inipipe string T t follow a predetermined volume of cement M so as to lodge on the upper end of shear sleeve 22 when this pre-.

determined volume of cement M has passed into the well boreand then close-off the lower end of the bore of pipe string T A second body of cement M follows the first body of cement M through pipe string T and is in turn followed by a cementing plug 30, of conventional design equipped with toothed slips 31 adapted to engage anchor teeth 25, as will appear hereinafter. Plug 30 is followed by a suitable displacing fluid D in the usual manner.

bore and thereby relieve formations Z and Z of this load. Contemporaneously, reverse check valve 27 will similarly hold the hydrostatic head pressure of the fluid column in pipe string T off of the earth formatioins comprising zones Z and sothat setting of the cement can occur while minimumloading is exerted on'zones down under the cementing pressures.

Since the bore of pipe string T is filled'with When closureball 24 seats on sleeve 22 and closes the bore of pipe string T continued pumping of cement and the following displacing fluid will increase the pressure of the fluid in pipe string T As this pressure build up it will be directed through ports 20 into pressure chamber 19, moving piston 18 downwardly to expand the packer and seal-off the wellbore about the several pipe strings at a point above zones Z and Z and thereby immediately relieve these zonesfrom the hydrostatic pressure exertedby the column of cement and any over-lying well bore liquids in the well bore, thereby accomplishing the prii maryfunction of the procedure in invention. a

' As the pump pressure builds above thepacker-setting pressure, which, for example, may be 1000 pounds per accordance with thissquare inch, the increase inpressure'will exceed the breaking strength of shear pin 23, which will havebeen selected to break at pressures above the predetermined packersetting pressure. Shear pin'23 will then break and shear sleeve 22 and closure ball 24'will be expelled from the lower end of lower section T and will fall into the bottom of the well bore (FIG. 2).

When the pressure in pipe string T is building up,-

valve V on pipe string T will be opened, so that when placement of this remaining well bore fluid to thereby assure that the entire well bore from the very bottom to the desired elevation in casing C will be filled with cement. When the-predetermined quantity of cement M has been discharged from lower section T ,plug 30 will have I attained the lower end of section T and slips 31 will become locked in anchor -teeth25. llugltl will then be held against reverse movement inpipe string T and will act to take the head pressure of the column of displacing fluid in pipe string T oil of the'cement in the well It will be undertood that the displacing of the successive bodies of cement and the intervening operation of setting the packer will occur rapidly and continuously so that the head pressure of the total column of liquid cement on zones Z and Z will be exerted only for a very brief period before the packer is actuated. Subsequent setting or hardening of the cement will take place after the head pressures of the fluid columns in the well bore and in the bores of pipe strings T and T 'willhave been relieved from Zones Z and Z Thus, the possibility of breakdown of either zone and consequent loss of cement with a resultant imperfect cement job will be reduced to a minimum.

It willl also be evident that the cementing method in accordance with this invention may be employed in' multiple pipe string cementing where the well bore'is equipped with more than two strings of pipe adapted to communicate with a corresponding number of producing zones. Any one of the severalpipe strings may be employed as thecementing string, each of the other pipe strings being equipped as pipe string T of the illustrative embodiment.

Ordinarily, the several pipe strings willbe of different lengths corresponding generally to the depths of the respective production zones to which they are to be communicated, asin the'illustrative embodiment. The cementing string may be the shorter string or it may be any of' the others, without altering the primary procedural steps of the method,.which, comprises three principal steps: (1) placing of the main body of cement in the well bore, (2) the closing-off of the bore of the cementing string;

a and (3) setting the'packer.

It will beevident that the cementingiprocedures are subjectto variations and modifications which are encomequipped with a plurality of pipe strings extending to the elevations of the several earth zones, the 'method'which comprisesthe stepsof:

p (a) introducing into the wellbore through one of. said pipe strings a quantity of cement sufllcient to fill said well here to an elevated height above said zones while maintaining the lower ends of all the other pipe strings closed against downward flow of fluid therefrom, i

. V (b) thereafter before the cement has time to set sealing oil the ,well bore about all of the pipe strings at'a point adjacent and abovesaid zone which is subject to breakdown whereby to relieve the latter zone from the hydrostatic pressure of the cement V above'saidpoint'; and I I (0) closing the lower end of said one of said pipe strings.

,2. In cementing of a well bore intersecting a plurality of earthfzones, at least one of which is a thief zone subject to breakdown under'cernenting pressures, said well bore being equipped with a plurality of pipe strings extending tothe elevations of the several earth zones, the

. method which comprises the steps of:

(a) introducing into the wellbore through one of said pipe strings a quantityof cement sufiicient to fill said well bore to an elevated height above said thief zone while maintaining, the lower ends of all the other pipestrings closed against downward flowof fluid therefrom, whereby to relieve said thief zone 1 of the hydrostatic pressure of fluid in said other pipe strings,

(b) thereafter before the cement has time to set sealing off the well bore about all of the pipe strings at a point adjacent and above said thief zone whereby to relieve the latter from the hydrostatic pressure of the cement above said point; and

(c) closing the lower end of said one of said pipe strings whereby to relieve said thief zone of the hydrostatic pressure of fluid in said latter pipe string.

3. In the cementing of a well bore intersecting a plurality of earth zones at least one of which is a thief zone which is subject to breakdown under cementing pressures, said well bore being equipped with a plurality of pipe strings extending to the elevations of the several earth zones, the method which comprises the steps of:

(a) mounting about the several pipe strings a fluidpressure expansible packer means positioned to seal off the well bore about the several pipe strings at a point adjacent and above said thief zone,

(12) introducing into the well bore through one of said pipe strings a quantity of cement sufficient to fill said well bore to an elevated height above said zones while maintaining all the other pipe strings closed off against downward flow of fluid therefrom;

() closing off the lower end of said one of said pipe strings after said quantity of cement has been introduced in the well bore; and

(d) before the cement has time to set actuating said packer means to seal off the well bore above said thief zone.

4. In the cementing of a well bore intersecting a plurality of earth zones at least one of which is a thief zone which is subject to breakdown under cementing pressures, said well bore being equipped with a plurality of pipe strings extending to the elevations of the several earth zones, the method which comprises the steps of:

(a) mounting about the several pipe strings a fluidpressure expansible packer means positioned to seal off the well bore about the several pipe strings at a point adjacent and above said thief zone, said packer means being in fluid-pressure communication with one of said pipe strings;

(b) introducing into the well bore through said one of said pipe strings a quantity of cement sufficient to fill said well bore to an elevated height above said zones while maintaining all the other pipe strings closed off against downward flow of fluid therefrom;

(0) closing off the lower end of said one of said pipe strings after said quantity of cement has been introduced in the well bore; and

(d) before the cement has time to set increasing the fluid pressure in said one of said pipe strings sufficiently to actuate said packer means to seal off the well bore above said thief zone.

5. In the cementing of a well bore intersecting a plurality of earth zones at least one of which is a thief zone which is subject to breakdown under cementing pressures, said well bore being equipped with a plurality of pipe strings extending to the elevations of the several earth zones, the method which comprises the steps of:

(a) mounting about the several pipe strings a fluidressure expansible packer means positioned to seal off the well bore about the several pipe strings at a point adjacent and above said thief zone, said packer means being in fluid-pressure communication with one of said pipe strings;

(b) introducing into the well bore through said one of said pipe strings a quantity of cement sufficient to fill said well bore from a point near the lower end of said one of said pipe strings to an elevated height above said zones while maintaining all the other pipe strings closed off against downward flow of fluid therefrom;

(c) initially closing off the lower end of said one of said pipe strings after said quantity of cement has been introduced in the well bore;

((1) thereafter before the cement has time to set increasing the fluid pressure in said one of said pipe strings sufficiently to actuate said packer means to seal off the well bore above said thief zone;

(2) re-opening said one of said pipe strings and introducing therethrough an additional quantity of cement into the well bore to displace well bore fluid into the other pipe strings; and

(f) then re-closing the lower end of said one of said pipe strings.

6. In the cementing of a well bore intersecting a plurality of earth zones at least one of which is a thief zone which is subject to breakdown under cementing pressures, said well bore being equipped with a surface casing terminating at a substantial elevation above said zones and with a plurality of pipe strings extending to the elevations of the several earth Zones, the method which comprises the steps of:

(a) mounting about the several pipe strings a fluidpressure expansible packer means positioned to seal off the well bore about the several pipe strings at a point adjacent and above said thief zone, said packer means being in fluid-pressure communication with one of said pipe strings;

(b) introducing into the well bore through said one of said pipe strings a quantity of cement sufiicient to fill said well bore to an elevated height extending into the lower end of said casing while maintaining all the other pipe strings closed off against downward flow of fluid therefrom;

(0) closing off the lower end of said one of said pipe strings after said quantity of cement has been introduced in the well bore; and

(d) before the cement has time to set increasing the fluid pressure in said one of said pipe strings to actuate said packer means to seal off the well bore above said thief zone.

References Cited in the file of this patent UNITED STATES PATENTS 3,022,823 Caldwell et al. Feb. 27, 1963

Claims (1)

1. IN THE CEMENTING OF A WALL BORE INTERSECTING A PLURALITY OF EARTH ZONES, AT LEAST ONE OF WHICH IS SUBJECT TO BREAKDOWN UNDER CEMENTING PRESSURES, SAID WELL BORE BEING EQUIPPED WITH A PLURALITY OF PIPES STRINGS EXTENDING TO THE ELEVATIONS OF THE SEVERAL EARTH ZONES, THE METHOD WHICH COMPRISES THE STEPS OF: (A) INTRODUCING INTO THE WELL BORE THROUGH ONE OF SAID PIPE STRINGS A QUANTITY OF CEMENT SUFFICIENT TO FILL SAID WELL BORE TO AN ELEVATED HEIGHT ABOVE SAID ZONES WHILE MAINTAINING THE LOWER ENDS OF ALL THE OTHER PIPE STRINGS CLOSED AGAINST DOWNWARD FLOW FLUID THEREFROM, (B) THEREAFTER BEFORE THE CEMENT HAS TIME TO SET SEALING OFF THE WELL BORE ABOUT ALL OF THE PIPE STRINGS AT A POINT ADJACENT AND ABOVE SAID ZONE WHICH IS SUBJECT TO BREAKDOWN WHEREBY TO RELIEVE THE LATTER ZONE FROM THE HYDROSTATIC PRESSURE OF THE CEMENT ABOVE SAID POINT; AND (C) CLOSING THE LOWER END OF SAID ONE SAID PIPE STRINGS.

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