US3330349A

US3330349A - Method and apparatus for multiple string completions

Info

Publication number: US3330349A
Application number: US395784A
Authority: US
Inventors: William D Owsley; Jr Charles D Manson; John C Holden
Original assignee: Halliburton Co
Current assignee: Halliburton Co
Priority date: 1964-09-11
Filing date: 1964-09-11
Publication date: 1967-07-11
Anticipated expiration: 1984-07-11

Description

y 11, 1967 w. D. OWSLEY ETAL 3,330,349

METHOD AND APPARATUS FOR MULTIPLE STRING COMPLETIONS 3 Sheets-Sheet 1 Filed Sept. 11, 1964 INVENTORS JOHN C-IIOLDEN,

char/@455 aJvn/vaazv-wa W/AL/AM 0.0144545),

BY PM, W @AH M ATTORNEYS 1957 w. D. OWSLEY ETAL 3,330,349

METHOD AND APPARATUS FOR MULTIPLE STRING COMPLETIDNS Filed Sept. 11, 1964 3 Sheets-Sneet 2 ATTORNEYS July 11, 1967 w. D. OWSLEY ETAL 3,330,349

METHOD AND APPARATUS FOR MULTIPLE STRING COMPLETIONS Filed Sept. 11. 1964 5 Sheets-Sheet 5 5 m m M w J mklfs am BY QM, D0 S- H ATTORNEYS United States Patent 3,330,349 METHOD AND APPARATUS FOR MULTIPLE STRING COMPLETEONS William D. Owsley, Charles D. Manson, Jr., and John C.

Holden, Duncan, Okla, assignors to Halliburton Company, Duncan, Okla, a corporation of Deiaware Filed Sept. 11, 1964, Ser. No. 395,784 14 Claims. (Cl. 166-21) This invention relates to multiple string completions, and more particularly to the directional drilling of auxiliary bore holes from a primary bore hole.

In drilling offshore wells, it is more economical to drill several wells from the same platform location than to move the drilling platform short distances to drill the adjacent wells. A common method of drilling multiple wells from the same well site is directional drilling. A primary bore hole which is substantially vertical is drilled first. The drill string is then raised and a Whipstock is run in the bore hole on the end of a drill string of a smaller diameter. When the whipstock engages the bottom of the hole the drill string moves downwardly relative to the whipstock and the drill bit is deflected outwardly at an inclined angle by the whipstock. If the whipstock is of the removable type, it is necessary to raise the drill string again to retrieve the whipstock before continuing to drill the auxiliary bore hole. For these reasons, it is preferable to use a fixed type whipstock for deflecting a plurality of drill strings in offshore drilling.

If there are to be two or more auxiliary bore holes to be drilled from the primary bore hole, there must be at least two separate whipstocks and drill strings in the primary bore hole. Due to the forces imposed on the whipstocks and to prevent their movement in the primary bore hole, it is necessary to cement the whipstocks in position. If the whipstocks are all placed at about the Same elevation in the primary bore hole, they should all be cemented simultaneously. The internal pressure differentials in the casing strings and the interference between the adjacent casing strings make it difficult to run the several casings in the primary bore hole simultaneously, although this is desirable for economical operation. Furthermore, since the whipstock partitions the casing string in which it is inserted, cement cannot flow out of the bottom of the casing string, as is necessary to ensure a firm bond between the pipe and the formation.

Accordingly, it is an object of this invention to provide method and apparatus for guiding and cementing multiple strings of casing in a bore hole.

It is a further object of this invention to provide method and apparatus for multiple directional drilling of auxiliary bore holes from a primary bore hole.

It is another object of this invention to provide method and apparatus for simultaneously guiding and setting multiple strings of casing in a bore hole.

These objects are accomplished in accordance with a preferred embodiment of the invention by a multiple string cementing tool having a plurality of strings of pipe secured together in substantially parallel relation and having their lower ends secured in a hollow shoe. Whipstock wedges are mounted in one or more of the pipes. The shoe has a perforated bottom wall and several holes in its top wall adjacent the casing strings. One of the pipes communicates with the interior of the hollow shoe for supplying cement slurry to the shoe. After the primary bore hole has been drilled, the multiple string cementing tool, which has each of its pipes secured to the end of an individual casing string, is run in the primary bore hole. Cement slurry is then pumped down one of the pipes and into the interior of the hollow shoe, where the cement sprays out through the holes and perforations 3,33%,349 Patented July 11, 1967 in the cementing shoe. The spray of cement slurry prevents channelling of the cement and assures a good bond with the formation. The holes in the top of the shoe assure that sufiicient cement also will flow into the spaces between the pipes to form a solid foundation for the pipes. A portion of the cement may also flow out of the lower end of the cementing string, depending on whether the pipe is fully or partially plugged below the cementing shoe port. After the cement has set, a drill string is run in one of the pipes containing a whipstock wedge and the Wedge deflects the drill string outwardly through a window in the pipe for drilling an auxiliary bore hole in the formation at an angular deflection.

This preferred embodiment and several modifications thereof are illustrated in the accompanying drawings in which:

FIG. 1 is a side elevational view, partially in section. of the multiple string cementing tool of this invention;

FIG. 2 is a bottom plan view of the tool; FIG. 3 is a cross sectional view of the tool along the line 33 in FIG. 2;

FIG. 4 is a cross sectional view of the tool along the line 4-4 in FIG. 1;

FIG. 5 is a cross sectional view of the tool along the line 55 in FIG. 1;

FIG. 6 is a cross sectional view of the tool along the line 66 in FIG. 1;

FIG. 7 is a cross sectional view of the tool along the line 7-7 in FIG. 1;

FIG. 8 is an elevational view of a modified form of the cementing tool of this invention;

FIG. 9 is a perspective view of a modified form of the hollow cementing shoe, having a conical shape;

FIG. 10 is a perspective view of another modification of the hollow shoe; and

FIG. 11 is a perspective view of still another modified form of the hollow shoe wherein the lower surface is substantially spherical.

The multiple string cementing tool of this invention according to a preferred embodiment has three

pipes

2, 4 and 6. The number of pipes in the tool depends on the number of auxiliary bore holes that are desired. Generally, there must be at least one pipe provided for each auxiliary bore hole. The pipes are secured together by being welded to a central mandrel 8. Althought the

pipes

2, 4 and 6 are preferably welded to the mandrel 8 by discontinuous welds substantially throughout the length of the mandrel 8, they may also be secured to the mandrel by any other suitable means. Braces 12 are also welded or otherwise secured between

adjacent pipes

2, 4 and 6, to provide additional rigidity. A plurality of centralizer -springs 14 are mounted on the

pipes

2, 4 and 6, and on the braces 12 for maintaining the tool centered in the bore hole. Each centralizer spring 14 has one end rigidly secured to the brace 12 or the pipe, respectively, and the opposite end is received in sliding engagement in a bracket 16 which is welded or otherwise secured to the brace 12 or the pipe. The brackets 16 permit longitudinal displacement of one end of the springs 14 as they are compressed in the bore hole, but the resiliency of the springs 14 urges the tool to be centered in the bore hole. The upper end of each of the

pipes

2, 4 and 6 is coupled to an individual casing string 18 by conventional couplings.

In the form of the invention shown in FIG. 1, in which there are three pipes secured together, two of the pipes have elongated slots or windows 20 formed on the outer side thereof and a whipstock wedge 22 rigidly mounted in the pipe and reinforced by spacer elements 24 at intervals along the length of the wedge. Fluid may flow into and out of the space behind the wedge 22 through a hole 25 in the wall of each pipe 2 and 4. The sectional portion of the tool shown in FIG. 1, is taken along the line 11 in FIG. 5. The whipstock wedges 22 may be spaced longitudinally of the tool at any desired location.

The remaining pipe 6, which does not have a whipstock Wedge mounted therein, serves as a conduit for the cement slurry and may have a plug 26 either fully or partially closing the lower end thereof or be unplugged as desired. The lower ends of the other pipes 2 and 4 are plugged and are enclosed by a hollow shoe 28, while the lower end of the mandrel 8 is closed by a plug 30. The hollow shoe 28 includes a band 32 which encircles the three

pipes

2, 4 and 6, as shown in FIGS. 2 and 7. A bottom plate 34 is secured around the lower edge of the band 32 by Welding, or it may be integral therewith. The shoe 28 has ribs 36 which reinforce the band 32' and the bottom plate 34. A top plate 38 having large holes therein corresponding to the diameters of the

pipes

2, 4 and 6 is secured along the upper edge of the band 32 by welding, or it may be integral therewith. The top plate 38 is also provided with small holes or openings 40, The top plate 38 is spaced above the reinforcing ribs 36 to provide fluid communication between the pipes and the ribs. The shoe 28 on the lower end of the

pipes

2, 4 and 6 not only provides for distribution for the cement slurry,

but also protects the ends of the pipes while the tool is being run in the bore holes.

A port 42 in the cementing pipe 6. is aligned with the space between the top of the ribs 36 and the top plate 38 for conducting cement slurry intothe shoe 28. As shown in FIGS. 2 and 7, the bottom plate 34 has a plurality of perforations 44 and cement which is pumped down the pipe 6 is diverted through the. port 42 by the plug 26 to the interior of the shoe 28. From the shoe, the cement flows upwardly through the openings 40 and around the

pipes

2, 4 and 6. The cement also flows downwardly through the perforations 44 where it is sprayed outwardly below the shoe.

The plug 26 has a passageway 46 formed therein and a portion of the cement slurry flows through the passageway without entering the interior of the shoe 28. It is desirable to have cement slurry flowing out of the bottom of the string at a relatively high rate for clearing obstructions and ensuring a good bond with the surrounding formation. One danger of having a high rate of How of cement slurry, however, is that the cement may channel upwardly around the string and not deposit sufficient quantities of cement around certain portions of the tool to form a strong bond. To overcome the problem of channelling, the cement slurry is sprayed through the perforations 44 and upwardly through the holes 40 to ensure good distribution of the cement around the tool, The passageway 46 may be enlarged to increase the rate of flow of cement slurry, or it may be eliminated entirely so that all of the cement flows through the perforations 44 in the holes 40. If bore hole conditions are such that channelling is not likely to occur, the plug 26 may be" removed.

In operation, each of the

pipes

2, 4 and 6 of the multiplespring cementing tool of this invention is coupled to an individual casing string 18 by a coupling and the tool is lowered into a bore hole. When the desired depth is reached, cement slurry is pumped down one of the casing strings 18 and into the pipe 6. The cement flows through the port 42 to the interior of the shoe 28 and through the passageway 46 into the well bore. The cement in the shoe 28 is sprayed downwardly through the perforations 44 and upwardly through the openings 40. Cement may also fill the space between the whipstock wedge and the wall of the pipes 2 and 4 by flowing through the holes 25. After the cementing is complete and the cement has set, a drill string is run in the pipe 4, where it is deflected outwardly by the whipstock wedge 22 through the slot or window 20 and drills a hole through the cement and into the formation. After completion of the drilling of the first auxiliary bore hole, another drill the band 62.

string is lowered in the pipe 2 and is deflected outwardly by the whipstock wedge 22 through the window 20, and drills a hole through the cement and into the formation. Although there are three pipes shown in the embodiment of FIG. 1, there may be more than two pipes containing whipstock wedges, provided the bore hole is sufliciently large to accommodate the pipes.

A modified form of the invention is illustrated in FIG. 8. The tool shown in FIG. 8 schematically represents a tool having a plurality of strings, as represented by the pipe 52 and the remaining strings which have whipstock Wedges therein are represented by the string 50. There may be one or more such strings 50, provided the bore hole is sufliciently large to accommodate the pipes. In

this form of the invention, each of the pipes 50 and 52,

has a whipstock wedge 54 rigidly secured therein and has a slot 56 in alignment with the wedge 54. The pipes 50 and 52 are secured to a central 'hollow mandrel 58 by welding or other suitablemeans, and the lower ends of the pipes 50 and 52 and the mandrel 58 are enclosed by a shoe 60. The shoe includes a cylindrical band 62 and a bottom plate 64 which is secured along its edge to the band 62 by welding, or it may be integral therewith. The bottom plate 64 extends across the ends of the pipes 50 and 52, thereby sealing them against fluid communica tion with the interior of the pipes. A top plate 66 has holes therein of substantially the same diameter as those of the pipes 50 and 52 and is secured along its marginal edge by welding or other suitable means to the band 64. V

Cement slurry flows out of the shoe through perforations 66 in the bottom plate 64 and through holes 70 in the top plate. The interior of the shoe is reinforced by ribs 72 which are secured between the mandrel 58 and A plug 74 formed by drillable material, such as cement, or by a drillable device, suchv as a limit plug 'or a bridge plug, is inserted in the pipe 52 above the whipstock Wedge 54. A port 76 extends through the walls of the pipe 52 and the mandrel 58 and the upper end of the hollow mandrel 58 is permanently plugged. The lower end of the mandrel 58 is open and communicates with the interior of the shoe 60.

To prevent the cement from flowing from the annulus upwardly in the pipe 50 by entering the slot 56 in the other whipstock string 50, a solid baflle collar 78 is placed at the top of the string 50. A conventional float collar 80 is provided in the cementing string to provide a landing base for a cementing plug and a back pressure valve to prevent reentry of the cement into the pipe 52.

In operation, cement slurry is pumped down the string, through the float valve 80 and into the pipe 52, where it is diverted into the interior of the hollow mandrel 58 by the plug 74 through the ports 76. The cement slurry flows from the mandrel 58 into the interior of the shoe 68, where it flows outwardly through the perforations70 and the holes 72 to ensure uniform distribution of the cement slurry and to accomplish a cleaning action.

Although the cementing shoe 28, as shown in FIGS. l to 7, is substantially triangular in cross section, the

shoes

28 and 60 may have other shapes. For example, as shown in FIG. 9, a shoe 82 is circular in cross section and has a conical lower plate 84 which is secured along its edge to the cylindricalb-and 86. Another alternative for the shape of the shoe is shown in FIG. 10. The shoe: 88 has a lower plate 90 which is substantially conical, but the band 92 to which the bottom plate is secured is substantially triangular in cross section. The modified shoes 82 and 88 function as wedges when the tool is being run in the bore hole, and during cementing, the

Another modified form of the shoe is shown in FIG. 11.

In this form, the shoe 94 has the lower plate 96 which is substantially spherical and the band 98 encircling the pipe is substantially triangular. Each of the bottom plates 84, 90 and 96, has an opening through which the cementing string 100 extends. Each of the other strings containing whipstock wedges are closed by the bottom plates 84, 90 and 96, respectively. A .plug may be inserted in the end of the cementing string 10% for fully or for partially closing the cementing string and thereby diverting a portion or all of the cementing slurry into the interior of the respective shoes, as desired.

The multiple cementing tool of this invention permits multiple strings of casing to be lowered simultaneously into a bore hole and the shoe on the lower end of the tool protects the ends of the pipes as they are being run into the bore hole. The shape and arrangement of holes in the shoe provide a uniform distribution of cement around the outside of the tool, without interfering with the use of the permanent whipstocks which are secured in position when the tool is cemented in the bore hole.

While this invention has been illustrated and described in several embodiments, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.

We claim:

1. A multiple string cementing tool comprising a hollow shoe, a plurality of pipes, means for securing together said pipes in substantially parallel relation, said shoe encircling said pipes and being secured thereto, means for conducting fluid between the interior of one of the pipes and the interior of the shoe, said shoe having a plurality of openings in the wall thereof said shoe having an upper side and a lower side, said upper side intersecting said pipes at a point spaced from the end of the pipes, said pipes extending through the shoe and terminating at said lower side of the shoe, and means for partially plugging said one pipe, whereby cementing fluid which is pumped down said one pipe is diverted through the conducting means into the shoe and also flows outwardly through the end of said one pipe.

2. A multiple string cementing tool comprising a hollow shoe, a plurality of pipes, means for securing together said pipes in substantially parallel relation, said shoe encircling said pipes and being secured thereto, means for conducting fluid between the interior of one of the pipes and the interior of the shoe, said shoe having an upper side and a lower side, said upper side intersecting said pipes at a point spaced from the end of the pipes, said pipes extending through the shoe and terminating at said lower side of the shoe, said first and second sides having holes communicating with the interior of the shoe, and means for plugging at least one of said pipes, whereby multiple strings of pipe may be run in a well and cemented effectively.

3. A multiple string cementing tool according to claim 2 wherein said lower side of the shoe is spherical.

4. A multiple string cementing tool according to claim 2 wherein said lower side of the shoe is substantially conical.

5. A multiple string cementing tool comprising a hollow shoe, a plurality of pipes, means for securing together said pipes in substantially parallel relation, said shoe enclosing the ends of said pipes and having a plurality of openings through the wall thereof, means for conducting fluid between the interior of one of said pipes and the interior of the shoe, another of said pipes having an elongated slot therein, and means in said other pipe for diverting a drill string outwardly through the slot, whereby an auxiliary well bore may be drilled after the tool is cemented in the primary well bore.

6. A multiple string cementing tool comprising a hollow mandrel, a hollow shoe secured to the end of the mandrel, a plurality of pipes, each of said pipes being secured to the exterior of the mandrel and having one end secured in the hollow shoe, said shoe having a plurality of openings through the wall thereof, and means for conducting fluid from the interior of one of the pipes through the mandrel to the interior of the shoe whereby cement is sprayed through the openings in the shoe.

7. A multiple string cementing tool comprising a hollow mandrel, a hollow shoe secured to the end of the mandrel, a plurality of pipes secured to the exterior of the mandrel and each having one end secured in the hollow shoe, said shoe having a plurality of openings through the wall thereof, one of said pipes having an elongated slot therein, means in said one pipe for divert ing a drill string outwardly through the slot, and means for conducting fluid between the interior of one of the pipes and the interior of the shoe whereby cement is sprayed through the openings in the shoe.

8. A multiple string cementing tool comprising a hollow mandrel, a hollow shoe secured to the lower end of the mandrel, a plurality of pipes, each of said pipes being secured to the exterior of the mandrel and having one end secured in the hollow shoe, said shoe having a plurality of openings therein, one of said pipes having an elongated slot therein, means in said one pipe spaced above said shoe for diverting a drill string outwardly through the slot, a plug in said one pipe spaced above said diverting means, and means for conducting fluid between the interior of said one pipe above said plug and the interior of the mandrel, said mandrel having a port communicating with the interior of the shoe, whereby cement is sprayed through the openings in the shoe.

9. A multiple string cementing tool comprising a hollow mandrel, a hollow shoe secured to the end of the mandrel, a plurality of pipes, each of said pipes being secured to the exterior of the mandrel and having one end secured in the hollow shoe, said shoe having a plurality of openings through the wall thereof, one of said pipes having an elongated slot therein and having a whipstock wedge secured in the pipe in alignment with the slot, a plurality of plates secured between adjacent pipes at spaced intervals along the pipes, and spring means mounted on the plates for centering the pipes in a bore hole.

10. A multiple string cementing tool comprising a hollow shoe, a plurality of pipes, means for securing together said pipes in substantially parallel relation, said shoe enclosing the end of each of said pipes and having .a plurality of openings through the wall thereof, and means for conducting fluid between the interior of one of said pipes and the interior of the shoe, at least two of said pipes each having an elongated slot therein and havin a whipstock wedge secured in the pipe in alignment with the slot, whereby a drill string in each of said slotted pipes is directed outwardly through its respective slot.

11. A multiple string cementing tool comprising a hollow shoe, a plurality of pipes, means for securing together said pipes in substantially parallel relation, said shoe enclosing the end of each of said pipes and having a plurality of openings through the wall thereof, and port means communicating between the interior of one of said pipes and the interior of said shoe, said shoe having a plurality of ribs extending radially between the pipes, a band extending around and secured to said pipes and said ribs, an upper plate having its edges secured to the band and having holes therein, and a lower plate having its edges secured to the band and having holes therein, said upper and lower plates having aligned openings therein for receiving said pipes, whereby cement is sprayed upwardly around the pipes and downwardly through the holes.

12. A multiple string cementing tool according to claim 11 wherein said band is cylindrical.

13. A method of drilling multiple well bores comprising drilling a primary well bore, running in the well bore at least a pair of easing strings having a common tool on the end thereof, said tool having a hollow perforated shoe on the lower end thereof and pipes secured together 7 in side by side relation and at least one of said pipes having a whipstock wedge secured therein, conducting cement from a casing string through one of said'pipes to the interior of said hollow shoe, discharging cement from said hollow shoe into the primary well bore below the shoe, and running a drill string in the pipes having said wedges, whereby the tool is securely cemented in the well bore and the drill string is diverted by the whipstock wedges to drill an auxiliary well bore.

14. A method of drilling multiple well bores comprising drilling a primary well bore, running in the Well bore at least a pair of casing strings having a common tool on the end thereof, said tool having a hollow perforated shoe on the lower end thereof and a plurality of pipes secured together in side by side relation, and at least two of said pipes having whipstock wedges secured therein, each of said pipes being secured individually to the lower end of a casing string and having its lower end secured in said hollow shoe, conducting cement slurry through a casing string and a pipe to the interior of the hollow shoe, discharging cement from said hollow shoe into the well bore below the shoe and above the shoe, and running a drill string in the pipes having said References Cited UNITED STATES PATENTS 1,523,928 1/1925 Berney et al. 166-242. 1,716,925 6/1929 7 Loomis 166242 X 1,762,012 '6/1930 Every 175-402 X 1,900,163 '3/1933 Dana et al 17561 X 1,900,164 3/1933 Dana ct a1. 1-75-61 1,901,454 3/1933 Kelly 166-1175 X 1,923,448 8/1933 McCoy et al. 166-'117.5 2,492,079 12/1949 Wiley 17561 X 3,050,121 8/1962, Garrett et al. 166-21 X 3,086,592 4/1963 Hoch 16646 X 3,108,639 10/1963 Brooks 166-241 20 CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, Examiner.

I. A. CALVERT, Assistant Examiner.

Claims

5. A MULTIPLE STRING CEMENTING TOOL COMPRISING A HOLLOW SHOE, A PLURALITY OF PIPES, MEANS FOR SECURING TOGETHER SAID PIPES IN SUBSTANTIALLY PARALLEL RELATION, SAID SHOE ENCLOSING THE ENDS OF SAID PIPES AND HAVING A PLURALITY OF OPENINGS THROUGH THE WALL THEREOF, MEANS FOR CONDUCTING FLUID BETWEEN THE INTERIOR OF ONE OF SAID PIPES AND THE INTERIOR OF THE SHOE, ANOTHER OF SAID PIPES HAVING AN ELONGATED SLOT THEREIN, AND MEANS IN SAID OTHER PIPE FOR DIVERTING A DRILL STRING OUTWARDLY THROUGH THE SLOT, WHEREBY AN AUXILIARY WELL BORE MAY BE DRILLED AFTER THE TOOL IS CEMENTED IN THE PRIMARY WELL BORE.
6. A MULTIPLE STRING CEMENTING TOOL COMPRISING A HOLLOW MANDREL, A HOLLOW SHOE SECURED TO THE END OF THE MANDREL, A PLURALITY OF PIPES, EACH OF SAID PIPES BEING SECURED TO THE EXTERIOR OF THE MANDREL AND HAVING ONE END SECURED IN THE HOLLOW SHOE, SAID SHOE HAVING A PLURALITY OF OPENINGS THROUGH THE WALL THEREOF, AND MEANS FOR CONDUCTING FLUID FROM THE INTERIOR OF ONE OF THE PIPES THROUGH THE MANDREL TO THE INTERIOR OF THE SHOE WHEREBY CEMENT IS SPRAYED THROUGH THE OPENINGS IN THE SHOE.
13. A METHOD OF DRILLING MULTIPLE WELL BORES COMPRISING DRILLING A PRIMARY WELL BORE, RUNNING IN THE WELL BORE AT LEAST A PAIR OF CASING STRINGS HAVING A COMMON TOOL ON THE END THEREOF, SAID TOOL HAVING A HOLLOW PERFORATED SHOE ON THE LOWER END THEREOF AND PIPES SECURED TOGETHER IN SIDE BY SIDE RELATION AND AT LEAST ONE OF SAID PIPES HAVING A WHIPSTOCK WEDGE SECURED THEREIN, CONDUCTING CEMENT FROM A CASING STRING THROUGH ONE OF SAID PIPES TO THE INTERIOR OF SAID HOLLOW SHOE, DISCHARGING CEMENT FROM SAID HOLLOW SHOE INTO THE PRIMARY WELL BORE BELOW THE SHOE, AND RUNNING A DRILL STRING IN THE PIPES HAVING SAID WEDGES, WHEREBY THE TOOL IS SECURELY CEMENTED IN THE WELL BORE AND THE DRILL STRING IS DIVERTED BY THE WHIPSTOCK WEDGES TO DRILL AN AUXILIARY WELL BORE.