US3513912A - Magnetic depth indexing means - Google Patents

Description

May 26, 1970 s. T. BOOP MAGNETIC DEPTH mnsxme MEANS Filed Aug. 5, 1967 FIG. I

INVENTOR. GENE II BOOP MARCUS L. BATES United States Patent 3,513,912 MAGNETIC DEPTH INDEXING MEANS Gene T. Boop, 3509 Clearmont, Odessa, Tex. 79760 Filed Aug. 3, 1967, Ser. No. 658,215 Int. Cl. E21b 43/119; H01f 7/02 US. Cl. 166--65 3 Claims ABSTRACT OF THE DISCLOSURE A magnetic device associated with a casing, liner, or tubing of an oil well which enables a magnetic sensing device, such as a collar locator, to position various tools with exactness with respect to a predetermined location downhole of the well head. The magnetic device may consist of a number of magnets arranged in an internal annular groove in the casing, liner, or tubing, and spaced apart by plastic material.

BACKGROUND OF THE INVENTION This invention relates to apparatus for locating tools and the like at a predetermined distance downhole of a borehole with great exactness by the use of a magnetic sensing device such as a collar locator.

In carrying out drilling operations in order to produce hydrocarbons from formations located deep within the ground, the well, or borehole, is generally drilled to a depth of three hundred to one thousand feet, and a surface casing is then cemented into the borehole. The bit is then reduced in size, and the middle portion of the hole drilled, with this operation being called the salt string, or the middle string. The bit is again reduced in size and the oil string drilled. The oil string goes to the bottom of the hole. The borehole is therefore lined with casing which may be called the surface casing, the salt string, and the oil string. The casing is made up of multiple joints of pipe, with a collar threading the joints together. Sometimes a liner is used, especially where it is desired to plug off the old casing. The liner usually has no collar but instead is threaded together by employing male and female threads at opposite terminal ends of each joint of liner.

A collar locator, a device Which measures changes in mass in terms of flux density, is used to determine the position of the various collars with respect to a reference SUMMARY It is desirable, in carrying out certain operations on oil wells, to be able to exactly determine the location of various strata associated with the borehole. The use of a collar locator provides a means by which the well may be calibrated with respect to a location above the borehole. The expedient requires careful observations along with intimate knowledge of the location of the various collars associated with the bore hole. The present invention enables one or more collars having magnetic means associated therewith to be included within the bore hole so as to give a point of index far below the surface of the earth which accordingly provides the oil well technician with a precise means by which the depth being analyzed may be determined. For example, it is consoltion.

It is therefore a primaryobject of this invention to provide a borehole with a magnetic means which enables the exact determination of the depth of the well near a particular strata.

Another object of the present invention is the provision of a casing collar having magnetic means associated therewith which enables a magnetic collar locator to easily and unmistakably determine the presence of the magnetic collar.

Another object of the present invention is the provision of a magnetic means associated with the various tubing, pipe, or casing of a borehole which enables indexing of downhole tools and apparatus with respect to the depth of the Well in an exact and precise manner.

A still further object of the present invention is the provision of magnetic means which enables one to sequentially locate the magnetic means at a predetermined spaced apart interval to enable various zones of the well to be coded to thereby readily identify the various zones of the well.

A still further object of the present invention is the provision of magnetic identifying means associated with the various tubing and the like of an oil well to enable the determination of the exact depth of tools and various apparatus within an oil well.

The above objects are attained in accordance with the present invention by the provision of a magnetic means located a predetermined distance downhole in a borehole.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a portion of an oil well casing showing the depending ends of two sections of tubing connected together by a collar, wherein the collar is made in accordance with the present invention;

FIG. 2 is a fragmentary cross-sectional view of an oil well casing comprised of two depending ends of a liner and showing the present invention operatively associated therewith;

FIG. 3 is an enlarged fragmentary cross-sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of a modification of the device seen in FIG. 3;

FIG. 5 is an enlarged fragmentary representation similar to the embodiment of FIG. 4;

FIG. 6 is a view similar to FIG. 5, but showing a modification thereof;

FIG. 7 is an enlarged cross-sectional view of still another modification of the device seen in FIGS. 1 and 2;

FIG. 8 is a cross-sectional view, similar to FIG. 7, and showing still another modification of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a small portion or section of an oil well casing, as generally illustrated by the arrow at numeral 10. The casing is comprised of a terminal end portion of tubings 12 and 14 which are threadedly connected together in the usual manner by a collar 16. Threads 18 and 20 are spaced apart and an annular groove 22 provided in the illustrated manner therebetween. A magnet 24 having a north and south pole is rigidly afiixed within the groove by epoxy cement 26 and 28. While epoxy cement is recited as being desirable, this term should be understood to include fiber glass resin and the like.

Looking now to FIG. 2, the casing is comprised of a liner which includes the depending ends of a tube, pipe, or the like, as indicated by numerals 30 and 32. The liner includes male and female threads 34. An annular groove 36 is circumferentially described about the inside peripheral wall portion of the liner, with the groove being spaced apart from, adjacent to and clear of the threads. A magnet 38 is secured within the groove 36.

Looking now to FIG. 4, there is illustrated a magnet carried by a collar, tubing, piper, or liner 40, with the tubing having an annular groove 42 circumferentially disposed therein and carrying individual magnets 44 which are spaced apart and cemented in place by fiber glass resin 46.

Looking now to FIG. 5, which is similar in many respects to the embodiment of FIG. 4, there is seen a groove 50 having an upper edge portion 52 circumferentially disposed about the inside peripheral surface of an oil well casing or tubing and wherein there is suitably mounted a multiplicity of magnets 54 which are vertically aligned in parallel relationship with respect to each other and spaced apart thereby leaving spaces 56 therebetween. The magnets 54 may be individual metallic magnets or may be individual rectangular plastic inserts.

The plastic insert is similar to the insert 44 of FIG. 4 when viewed in cross-section, and is of a thickness which enables the inside peripheral wall surface thereof to coincide with, or to be continuous with, the inside diameter of the pipe. It is further preferred to make the length of the insert several times longer than the width thereof.

In FIG. 6 there is seen an annular groove 60, similar to the groove 22 or 36 of FIGS. 1 and 2 respectively, and wherein the groove 60 has a lower marginal edge portion 62 with two aligned rows of small pin like magnets, 64 and 66, disposed therein, leaving an annular groove 68 therebetween. In other words, the annular grooves 60 carry two circumferentially disposed rows of magnets 64 and 66 therein, with each row of magnets being spaced apart with the the groove to leave a smaller groove 68 between the adjacent but spaced apart ends of the rows of magnets.

As seen in FIG. 7, the wall of a pipe or collar 70 is suitably milled to provide an annular groove 72 therein which carries a magnet 74 within the groove. The depend ing ends of the magnet are spaced apart as seen at 76, thereby leaving a north and south pole as illustrated.

The discontinuous ring 74 may be of any desired width which is consistent with the groove dimensions so as to enable the ring to be received within the groove. The ring has an inside diameter slightly greater than the inside diameter of the groove so as to enable the ring to be compressed, placed within the groove, whereupon release of the ring enables it to expand against the outer peripheral groove wall surface where it is rigidly held caged by the compressive force exerted between the ring and the groove wall. The ring is preferably fabricated of a magnetic material which is sufiiciently resilient to enable the spring action of the ring to attain this function.

FIG. 8 shows a groove 82 placed in a wall 80 and carrying two magnets 84 therein with the magnets being more or less C-shaped and having spaced apart depending end portions as seen at 86 and 88. While the poles are arranged N-N and S--S with respect to each other, they may be reversed with respect to each other so as to present unlike poles adjacent each other, although it is preferred to place the poles in the indicated manner of FIG. 8.

Looking again to the embodiment of FIGS. 1 through 3, it will now be seen that the magnet 24 can be cut from a strip of magnetic tape (for example, magnetic tape having the tradename .Magnyl Magnetic Strips; manufactured by Chart-Pak Inc.), with the tape being cut a width and length equivalent to the width and circumferential length of the groove 22. The depth of the groove 22 is preferably slightly deeper than the thickness of the magnetic tape. The magnet is held in place by fiber glass resin which strongly adheres the tape within the groove of the collar as indicated at 22, while at the same time provides a protective film as indicated at 28.

The magnetic tape can alternatively be cut into strips and placed within the groove in the spaced apart manner illustrated by FIG. 4, with the epoxy resin filling the voids 46 therebetween.

Where deemed desirable, magnetized metallic bars may be cemented into the groove in the illustrated manner of FIG. 5.

In the embodiment of FIG. 6, small magnetic needles 64 are aligned Within the groove and secured in place by fiber glass resin which is painted thereon. This expedient provides a double pole magnet wherein like poles may be arranged at the small groove 68 to thereby provide a sharp change in flux at the groove.

In carrying out the present invention, the magnetic means are placed within the casing at predetermined levels near oil or gas bearing strata. It may be desirable, for example, to place a magnetic coupling at various depths, for example each one thousand foot intervals, so as to enable a perforating gun crew to rapidly drop the gun into the hole with no fear of overrunning the gun and hitting the bottom. Furthermore, various depths may be coded, or indexed, by placing a multiplicity of magnets at spaced apart intervals, such as for example, a fifteen thousand foot depth may be suitably indexed by a combination of magnets, assuming this level to be near one of the oil bearing strata.

In carrying out the present invention, assuming that an oil bearing stratum at fifteen thousand two hundred feet is to be perforated, and assuming that the zone has been indexed with the magnetic collar at fifteen thousand feet, the perforating gun is run into the hole with a magnetic collar locator attached thereto, and the gun is stabilized at the fifteen thousand foot level exactly and within a fraction of an inch from the magnet associated with the collar. The gun is then lowered exactly two hundred more feet as measured from the top of the wall, whereupon the perforation is then carried out at the precise location relative to the oil bearing strata, with an error amounting to less than one inch.

I claim:

1. In a borehole located in the ground and having tubular members therein, such as casing or production tubing, means for indexing oil well equipment at predetermined depths within the borehole comprising:

means forming an inwardly opening annular groove within one of said tubular members, said groove adapted to be spaced at a known distance below the surface of the ground;

a permanent magnet rigidly afiixed within said groove;

said magnet being comprised of a plastic material and a multiplicity of individual elongated magnetic bodies, said magnetic bodies being held in spaced apart relationship by said plastic material, each individual body having a length greater than its width, with each body being parallel to each other;

said groove being circumferentially disposed for 360 about the inside peripheral surface of said tubular member, the width of said groove being approximately equal to the length of each said body; and

each of said individual bodies being longitudinally disposed within said groove with respect to said tubular member.

2. The indexing means of claim 1 wherein said permanent magnet has a major diameter equal to the major diameter of the groove, and said permanent magnet has magnets being superimposed above the other row of mag- 5 nets to thereby leave a circumferentially disposed annular groove between each row of individual magnets.

References Cited UNITED STATES PATENTS 2,147,544 2/1939 Potts 166-66 2,228,623 1/1941 Ennis 1664 2,350,832 6/1944 Segesman 16666 X 3,106,960 10/1963 Doak 166-64 X 3,171,486 3/1965 Ownby 166-65 FOREIGN PATENTS 642,353 8/1950 Great Britain.

DAVID H. BROWN, Primary Examiner 0 I. A. CALVERT, Assistant Examiner US. Cl. X.R. 335303

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