US3593795A - Method and apparatus for drilling and producing wells in a formation susceptible to compaction - Google Patents

Abstract

Apparatus and method for completing a well in a subterranean oil-bearing formation wherein the well is adapted to traverse an area susceptible to compaction. A well is drilled and casing is installed in the well. The casing is provided with expansion joint means so as to prevent buckling of the casing when any compaction occurs in the area susceptible to compaction. The casing is then firmly fixed in position in the well.

Description

c United States Patent 1 13,s93,79s

[72] Inventor Leo P. Broussard. Sr. {56] References Cited UNITED STATES PATENTS 1 "P 828,093 2,230,626 2/1941 Miller 166/242 x [22] F1lcd May 19, 1969 s P d J I 20 1971 2,675,082 4/1954 Hall 166/285 Q Com 2,712,854 7/1955 Creighton... 166/242 l l N k N 2,900,028 8/1959 Hanes 166/242 3,020,962 2/1962 Holmquist... 166/242 3,064,729 1 1/1962 Lindley 166/297 Primary Examiner-Ian A. Calvert [54 1 METHOD AND APPARATUS ron DRILLING AND Mccamy PRODUCING WELLS IN A FORMATION EPMPACTIQN ABSTRACT: Apparatus and method for completing a well in rawmg a subterranean oil-bearing formation wherein the well is [52] U.S. Cl [66/285, adapted to traverse an area susceptible to compaction. A well 166/242, 285/300, 285/301 is drilled and casing is installed in the well The casing is pro- [51] Int. Cl ..E2lb 33/14. vided with expansion joint means so as to prevent buckling of F161 27/12 the casing when any compaction occuns in t he area susceptible [50] Field of Search 166/285, to compaction. The casing is then flrriily'lfiited in position in the well.

A FIXED POINT URRENT) l r ZONE (F INTEREST- L-AL BOTTOM FIXED POINT 1 H Fl rd PATENTEB JUL20 IIIII SHEET 1 UF 2 OP FIXED PoINT (ORIGINAL) i TOP FIXED VI POINT (CURRENT) FIG. 2

PRIOR ART PRIOR ART INVENTOR:

LEO P. BROUSSARD,SR BY:

HIS ATTORNEY PATENlEflJuLzmsn 3,593,795

SHEET 2 BF 2 L TOP FIXED POINT ORIGINAL ZONE OF INTEREST- L-AL P k H r) FIG. 4

lNVENTOR:

LEO R BROUSSARD,SR

HIS ATTORNEY METHOD AND APPARATUS FOR DRILLING AND PRODUCING WELLS IN A FORMATION SUSCEP'IIBLE TO COMPACTION BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to well completion; and, more particularly, to amethod and apparatus for preventing buckling ofa well casing adjacent to areas susceptible to compaction.

2. Description of the Prior Art In Louisiana oil fields, certain oil-bearing formations have shown a tendency to compact after substantial amounts of oil have been removed therefrom. This causes severe problems in regard to the casing and tubing in the wells extending into these formations. In bending, the cement surrounding the well casing cracks and sand is produced. Such bending is detrimental to the working of such wells since it is impossible to run tools and devices down the bent well to carry out remedial operations.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method and apparatus for preventing buckling of wells traversing areas susceptible to compaction.

It is a further object of this invention to provide apparatus which may be readily installed in a well toprevent buckling of the casing thereof adjacent to areas susceptible to compaction.

These objects are preferably carried out by completing a well into an area susceptible to compaction. The well is cased and the casing is provided with expansion joint means so as to prevent buckling of the casing when any wheel of the formation traversed by the well occurs. The casing is then firmly fixed in the well. In a preferred embodiment, the expansion joint means includes a high pressure seal element.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a vertical sectional, partly schematic, view of a well in accordance with the teachings of the present invention;

FIG. 2 is a vertical sectional, partly schematic, view of the well of FIG. I subject to buckling;

FIG. 3 is a vertical sectional, partly schematic, view of the well of FIG. I wherein the well casing is provided with expan' sion joint means in accordance with the teachings of the present invention; and

FIG. 4 is a vertical, partly sectional, view of the expansion joint means of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, FIG. 1 shows a well borehole I extending into a subterranean oil-bearing formation II. Well borehole includes a casing 12 cemented therein by cementing, as at 13. Well borehole 10 may also include atubing string 14 and a packer 15 as is well known in the art for working well borehole 10. The well casing I2 mayalso be perforated with perforations 16 extending through casing I2, cement I3 and into formation 11, as is also well known in the art.

Oil-bearing formation 1] may, for example, be divided into an upper sand-shale area 17, a lower shale area I8, a still lower sand area I9 and a bottom shale area 20. For the purposes of this discussion, it will be assumed that oil-sand area 19 is highly susceptible to compaction. As illustrated in FIG. 1, the zone of interest, i.e., the area in which any buckling of casing 12 is likely to occur due to sand compaction, comprises a top fixed point adjacent to shale area I8 and a bottom fixed point adjacent to the bottom of sand area I9. Thus, axial load on casing I2, prior to production, is substantially negligible.

Referring now to FIG. 2, after production of well borehole 10 through perforations I6 and up tubing string 14 past packer 15, a significant amount of compaction of the sand in the oil-sand area 19 has taken place. Thus, as can be seen in Fig. 2, casing I2, cement l3 and tubing; string I4 show a serious amount of buckling adjacent to sand area 19. The axial load on casing 12 is high, in the order of, for example, 560,000 to l,l00,000 pounds. The top fixed point has shifted by an amount AL to a lower fixed point. Due to the axial loads on casing I2, casing deformation takes place. Such deformation renders the future working within well borehole 10 very difficult and expensive.

Such casing buckling may be prevented by cutting a section of the cemented casing l2 adjacent to the sand area I9 by means of pipe cutters or the like, well known in the art. The cut section of the casing 12 may be so cut as to destroy it for all practical purposes so that the cut pieces fall to the bottom of well borehole I0. This results in shortening the pipe string or casing in the area of compaction, thus relieving the axial stress on casing I2. After cutting, an internal sleeve may be installed between the horizontally cut sections of casing 12; alternatively, the cutaway portion may be otherwise sealed such as by injection of epoxy resin or other suitable sealing means. Nevertheless, the above operation is expensive and alignment of the two casing sections may be difficult once the casing I2 is cut or destroyed. In addition, sand consolidation of sand area 19 is limited and in some cases may be impossible once the casing 12 is destroyed.

Preferably, however, in accordance with the teachings of the present invention, formation II is logged by techniques well known in the art so as to determine the upper and lower limits of sand area 19, i.e., the potentially productive zone. At the places in casing I2 adjacent to these upper and lower limits, or at least adjacent to the interval to be perforated, slip couplings in accordance with this invention are preferably installed, as illustrated in FIG. 3. Thus, a first slip coupling 21 is shown disposed adjacent to the base of sand area 19.

Although two such slip couplings are shown in FIG. 3, obviously one or more couplings may be installed in the well casing I2 within the well borehole 10. Also, as. is well known in the art, short sections in a string of pipe or casing, known as subs," may be installed in a well casing. Here, the sub" is the slip coupling which, as will be discussed further hereinbelow with reference to FIG. 4, is a telescoping section in the casing 12. The subs" (i.e., couplings 2I and 22) are disposed adjacent to sand area 19 which is susceptible to compaction. If necessary to assure the proper location ofcouplings 21 and 22 in the well borehole I0 with respect to the productive zone or zones, such as sand area 19, a collar locator log, as is well known in the art, may be taken prior to cementing the casing I2 in place. After the appropriate slip coupling or couplings are installed, casing I2 is cemented and the productive zones, such as sand area I9, are perforated in a conventional manner, as at perforations I6 with appropriate sand consolidation techniques being applied, where applicable. Pattern perforating for use with more sophisticated sand consolidation placement tools may be effected in a conventional manner as the coupling or couplings do not reduce drift through the casing 12. Thus, as seen in FIG. 3, axial loads induced on casing 12 by compaction of sand area I9 between fixed casing points and by packer forces and/or other forces associated with conventional oil well production practices, are absorbed by slip couplings such as couplings 2ll and 22, thus precluding buckling of casing 12. Although only one such sand area susceptible to compaction has been shown, obviously a plurality of such vertically spaced areas or strata may be traversed by well borehole 10 with appropriate slip couplings installed as required.

Referring now to FIG. 4, a slip coupling in accordance with the teachings of this invention is illustrated. Obviously, all the slip couplings may be similar to slip coupling 21 illustrated in FIG. 4 and described hereinbelow.

Slip coupling 211 includes an inner :member 23 slidably mounted in an outer member 24. Thus, member 23 telescopes into member 24. The upper end of inner member 23 includes a threaded portion 25 for connecting coupling 21 to a stan dard casing coupling (not shown). In like manner, the lower end of outer member 24 includes a like threaded portion 26 for connecting coupling 21 to a standard casing coupling (not shown). in this manner, the slip coupling 2K may be connected at any desired location in casing 12.

lnner member 23 includes an outer circumferential skirt portion such as cylinder 27, preferably of steel or similar material adapted to extend downwardly into a chamber 28, also preferably of steel, extending circumferentially of outer member 24. Cylinder 27 may be threaded onto the outer wall of inner member 23 as indicated by threads 29; alternatively, cylinder 27 may be integral with inner member 23, if desired. In either case, the outer surface of cylinder 27, adapted to slide downwardly into chamber 28, is coated to prevent cement bonding of the inner member 23 in chamber 28. Suitable coating materials may include a pliable rubber sleeve, rubber base material, etc.

A slot 30 extends longitudinally of cylinder 27. A pin 31 fixed in position in chamber 28 is adapted to slidably engage slot 30 so as to prevent rotation and/or premature movement of inner member 23 with respect to outer member 24. Obviously, a plurality of such pins and mating slots may extend circumferentially of chamber 28 and cylinder 27, respectively.

The upper movement of cylinder 27 with respect to chamber 28 is limited by stop means 32 on cylinder 27,

adapted to engage mating stop means 33 in chamber 28. A plurality of O-rings seal cylinder 27 and chamber 28 so as to exclude'debris from the coupling 21. If desired, chamber 28 may comprise an integral member, or, as shown in FIG. 4, be formed of sections threaded to outer member 24 as at threads 34 and 35, respectively, to form an integral chamber for cylinder 27.

A bellows 36 is disposed in chamber 28, fixed at one end 37 by brazing or other means well known in the art on cylinder 27 and the other end 38 to an abutment wall 39 disposed at the lower end or bottom of chamber 28. Bellows 36 provides a pressure seal between inner member 23 and outer member 24. Bellows 36 is preferably ofa thin-walled multi-ply material resistant to corrosion, such as Monel metal. The sealed bellows chamber, that is, the portion of chamber 28 between cylinder 27 and abutment wall 39, is preferably filled with a noncompressible fluid, such as oil, to prevent well bore fluids such as mud or cement from obstructing bellows movement and to lubricate the cylinder and chamber walls.

A pair of valve chambers 40 and 4B are disposed below abutment wall 39. Ports 42 and 43, respectively, lead from the bellows chamber to the respective chambers 40 and 41. Spring-loaded check valves are disposed in chambers 40 and 41, respectively, with springs 46 and 47, respectively, fixed at one end to their respective valve and the other end to the bottom wall of their respective chambers. Relief ports 48 and 49 are formed in chambers 40 and 41, respectively, for allowing displacement of the noncompressible chamber fluid when movement of casing 23 occurs due to axial loading as disc usmed hereinabove.

Conventional piston-type equalizers, such as equalizer 50, to provide for the internal pressure within the bellows chamber are preferably disposed in an equalizer chamber 51 below abutment wall 39. An outlet port 52 connects chambers 51 with the inner bellows chamber and an inlet port 53 is disposed at the lower end of the chamber 51. A similar arrangement is utilized to provide for the external pressure within the bellows chamber. in this equalizer chamber (identical to 51 except for ports) an outlet port 61 connects the equalizer chamber with the outer bellows chamber and an inlet port 60 is disposed at the lower end of the equalizer chamber. The purpose of the pressure equalizer is to equalize the pressure on either side of the bellows with respective pressures outside and inside the casing 24 without allowing external fluid, such as cement, to enter the seaied bellows chamber.

Thus, in operation, as illustrated in FIG. 3 and discussed hereinabove, as axial load is placed on casing 12 as a result of compaction of the sand in sand area 19, slip couplings 21 and 22, previously installed in casing 12 by means of threads 25 and 26, respectively, provide a mechanical means for relieving axial loads on casing 112, thus providing a maximum chance for sand consolidation and a minimum chance for complicated and expensive workovers, especially offshore, associated with casing deformation due to buckling.

Thus, as the casing H2 is disposed to buckle due to axial stress, inner member 23 of slip coupling 2] telescopes downwardly into outer member 24 while maintaining a seal therebetween due to O-rings 34. Pin or pins 3i slide in a slot or slots 31, thereby preventing rotation and/or premature movement between members 23 and 24. Bellows 36 provides a high pressure seal, thereby permitting installation of like couplings opposite all potentially productive zones in formation l1 along with a minimum chance of easing leakage. Such a leakproof connection in a producing zone is important so as to prevent excessive gas production from the top of the producing zone and water production from the base of the producing zone. Check valves 44 and 45, along with equalizer 50, provide an appropriate integral relief system allowing displacement of the noncompressible chamber fluid when casing movement occurs.

In summary, the slip couplings of the present invention, properly installed in well casing, provide casing relief with minimum resistance adjacent to formations susceptible to compaction. The external coating of the upper cylinder 27 prevents cement adhesion and the oil-filled sealed-bellows chamber excludes cement and other foreign material. The low resistance to movement offered by the bellows 36, preferably multi-ply, and the oil-lubricated cylinder and chamber walls insures minimum resistance to movement with maximum relief of axial casing loads.

I claim as my invention:

I. A method of drilling and completing a well in a subter ranean oil-bearing formation wherein at least a portion of said formation is susceptible to formation compaction, the method comprising the steps of:

drilling a well into said formation traversing the portion susceptible to compaction;

installing a well casing in said well;

providing said well casing with joint means adjacent to said portion susceptible to compaction adapted to move from an expanded state to a contracted state relative to changes in compaction of said portion thus preventing buckling of said casing when any compaction occurs in said portion of the formation susceptible to compaction, said joint means being installed in said well casing in substantially its expanded state;

coating at least a portion of said joint means with a material adapted to prevent said portion from adhering to a material to be used to cement said casing in said well; and thereafter cementing said casing firmly in position in said well with cement around said coated portion of said joint means.

2. The method of claim 1 wherein the step of providing said well casing with joint means includes providing said casing with at least one of said joint means disposed adjacent to substantially the top of the portion susceptible to compaction and at least one of said joint means disposed adjacent to substantially the bottom of the portion susceptible to buckling.

3. Apparatus for preventing buckling of a well casing in a well extending into a subterranean oil-bearing formation wherein a least a portion of said formation is susceptible to formation compaction, the apparatus comprising:

a well casing cemented in fixed position in said well adjacent to the portion of said formation susceptible to compaction; and

joint means disposed in said casing adjacent to the portion of said formation susceptible to compaction adapted to move from an expanded state to a contracted state relative to changes in compaction of said portion thus preventing buckling of said casing when any compaction occurs in said portion susceptible to compaction, said joint means being disposed in said casing in substantially its expanded state, said joint means including an inner member telescopingly received in an outer member in a fluidtight relationship, the inner member having first connecting means at its outer end for coupling to a first portion of said well casing and the outer member having second connecting means at its outer end for coupling to a second portion of said well casing, stop means disposed on at least one of said members for preventing the separation of said members, and a chamber containing a bellows means that is interconnected between said inner and outer members for pressure sealing said members.

4. The apparatus of claim 3 wherein said bellows chamber is filled with a noncompressible fluid adapted to prevent extraneous fluids from obstructing the movement of said he! walled, multi-ply bellows and said noncompressible fluid is an oil.

7. The apparatus of claim 3 wherein the outer surface of said inner member is coated with a material adapted to prevent adhesion of said inner member to said cemented portion of said formation traversed by said well.

Claims (7)

1. A method of drilling and completing a well in a subterranean oil-bearing formation wherein at least a portion of said formation is susceptible to formation compaction, the method comprising the steps of: drilling a well into said formation traversing the portion susceptible to compaction; installing a well casing in said well; providing said well casing with joint means adjacent to said portion susceptible to compaction adapted to move from an expanded state to a contracted state relative to changes in compaction of said portion thus preventing buckling of said casing when any compaction occurs in said portion of the formation susceptible to compaction, said joint means being installed in said well casing in substantially its expanded state; coating at least a portion of said joint means with a material adapted to prevent said portion from adhering to a material to be used to cement said casing in said well; and thereafter cementing said casing firmly in position in said well with cement around said coated portion of said joint means.

2. The method of claim 1 wherein the step of providing said well casing with joint means includes providing said casing with at least one of said joint means disposed adjacent to substantially the top of the portion susceptible to compaction and at least one of said joint means disposed adjacent to substantially the bottom of the portion susceptible to buckling.

3. Apparatus for preventing buckling of a well casing in a well extending into a subterranean oil-bearing formation wherein a least a portion of said formation is susceptible to formation compaction, the apparatus comprising: a well casing cemented in fixed position in said well adjacent to the portion of said formation susceptible to compaction; and joint means disposed in said casing adjacent to the portion of said formation susceptible to compaction adapted to move from an expanded state to a contracted state relative to changes in compaction of said portion thus preventing buckling of said casing when any compaction occurs in said portion susceptible to compaction, said joint means being disposed in said casing in substantially its expanded state, said joint means including an inner member telescopingly received in an outer member in a fluidtight relationship, the inner member having first connecting means at its outer end for coupling to a first portion of said well casing and the outer member having second connecting means at its outer end for coupling to a second portion of said well casing, stop means disposed on at least one of said members for preventing the separation of said members, and a chamber containing a bellows means that is interconnected between said inner and outer members for pressure sealing said members.

4. The apparatus of claim 3 wherein said bellows chamber is filled with a noncompressible fluid adapted to prevent extraneous fluids from obstructing the movement of said bellows.

5. The apparatus of claim 4 wherein at least one of said members includes fluid relief means for allowing displacement of the noncompressible chamber fluid when said inner member moves with respect to said outer member.

6. The apparatus of claim 4 wherein said bellows is a thin-walled, multi-ply bellows and said noncompressible fluid is an oil.

7. The apparatus of claim 3 wherein the outer surface of said inner member is coated with a material adapted to prevent adhesion of said inner member to said cemented portion of said formation traversed by said well.

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