US2562340A - Weight-graduated wire cable - Google Patents

Description

July 31, 1951 R. STANTON 2,562,340

WEIGHTGRADUATED WIRE CABLE Filed June 17, 1950 2 Sheets-Sheet 1' 3nnentor ZenL Sfanzon 2 Sheets-Sheet 2 INVENTOR.

July 31, 1951 R. STANTON WEIGHT-GRADUATED WIRE CABLE fioberil. Stanton a I .6 2 w a a p 4 au 6 0 l fi .1. g 2

Filed June 17, 1950 Patented July 31 1 951 IG T GK DU EDIWIHEQA E Robert-Ii. Stanton, Muncy, Rm, assignon=to..lnnes:- 8n Laughlin. Steel: Gorporatinm. Pittsburgh; ,Pa., amnporatim of rlienns van a nrli at mune Serial N; .68510 5 Claims. (01. 5 7.1145.)

This invention relates to wire; rope -or cable, and-is particularly-concerned with cable adapted fjor well drilling bythe cable toolmethod and similar uses.

As generally practiced, the cable tool method of drilling wells suchvasoil and gas wells comprises the lifting and-dropping by a rope or cable and appropriatehoist-ingmeans of a relatively heavy drillgbit upon the formation to be drilled. This method; of drilling-is'well adapted to relatively shallow. holes. and. requires simple. apparatus which can beeasily transported over the frequently diflicult terrain; in which. drilling proceeds. Itsis limited to relativelyshallow holes, however, because of theweight' of; the cable itself which must be payed out, to reach great depths.- The upper; portion of thecable must, of course support not only the weight of the tools but also the weightof'th'e cable in the hole, and even though wire cablesof high tensile strength are. commonly; employed. the. deptlnof. a, hole which can be economically drillediinthisway is limited. If stronger,v and thereforeheavier, cablesare. used topermit drillingto greater-depths, the weight ofthe cable to be transportedandthe sizeand weight. of the hoisting apparatus. must be corresponding-1y. increased, which. in, turn. increases thedifficul-ty of .transportin the field. In practice it. isgenerally consideredlthat theeco: nomical limit of cable tooldrilling isabout 6 ,000 feet if an adequate safetyfactor of cable strength is tobe maintained.

The. lower endofthe cable in.the hole carries only the weight of the drilling. tools, and the weight. carriedby. any successive sectionof cable increases gradually towardthe topof the hole. Conventional. cables. therefore provide anv unnecessarily large. factor, of safety at the.bottom ofthe hole,..and. represent excess weight at. this pointwhich mustbe borne by, the upper. portion of.- the cable.

In.thev past, attempts have beenpmade; to in-. crease the economic-ultimate:depthof cable tool drilling by providing a, drilling cable tapering frpma relatively smalldiameter at the bottom end to a. larger diameter'at. the upper. end, and for a given total weight these cablesdo permit the suspension. of. a. drillbit. andgreater length of. cable at a given factor. of safety thanispossible. with conventional cable. However, tapered cables are difficult to make. Eurthermore, they have not enjoyed muchpracticalsuccess in cable tooldrilling because they donot .allovvv the cable tooldriller, or tool. pusher as he is. commonly termedto-judgethe progress of drilling, byhis usual: method. Tool ushers, quite; generally gauge the progress of their drilling by Whatthey 22 call thefeel of the'rope-; that is; the vibration transmitted from the tools to the taut= cable at the top of the hole. Ithas beemfoundin+practice that a tapered cabl'e alters the characterof this-transmitted vibration to-suchanextent that; itcannot be used as aguide by thetool pusher in the same manner-= as vibrations set up in as cable" of uniform diameter. Drilling with a-taperedcable, therefore, tends to-- besl'o wen than conventional drilling: and more prone te -kinking: or-breaking of the cable; sticking: oftools in -thei hole;- or damage to-= these tools:

It is therefore an object of" my invention-to provide a cableforcabl'e tool drilling-which is offuniform diameter throughout its length but-has a unit weight and tensile strength which in.-" creases from the bottom" tothetop. It is another=object-of my -invention to provide such a; cable which has a-- more uniform safety factor: throughout its-length. It is still anothen object. of myinvention-to provide such aweightegradu'n ated cable which transmits vibratory impulses ine substantially the same manner as: conventionali drillihgcables:

invention comprises a wire cable or rope of' conventional layand conventional section having' individual wires which; although of'con-a stant diamete1 oven the length of the cable, arenot homogeneous; These composite wiresw which ferm the" strands; which inturn: comprise the cable, are in generalcomposed of steel: atithe upper end -oflthecable but of a metal-lighter than steel at the bottom of the cable. The relative lengths: of steel and lighter metal inthe com. positewires areadjusted sethat successive crossa sections along the: cableshow a ratio of lighter. metal to steelwhich increases by graduated amounts from one end: to: the other. A cable made. accordingto my. invention. therefore. ex hibits. a. uniform diameter; but progressively, de; creasing. unit weight. andultimate tensilestrpngtli. from one end to the other.

Reference; is now made to the figures which illustratethe cross-section of. a strand ofsuch. a. able- Fi' ure l. i5 3. cross section through a strandof a cable; of myinvention illustrating acon-van.- tional' arrangement of;wires.,.

Figuresm, 2b; and 2carecross sections through a cable strand embodying. my invention taken through successive portions of" thflstrand; The successive portions of the strand illustrated in this figure are'tabulated in'llablel following;

The strand shown is from a.- -inch 6-strand cable-of- 25 wire perstrand. The center wire or core: surrounded b wires; 2a: hrpu h. fsixzsmaller. wiresa known-.1 si illerr wires mm: .31;

3 inclusive, are laid between successive pairs of wires 2a through 2 The exterior of the strand is composed of 12 wires, 4a through 4m. The core wire I and the wires of roups 2 and 4 are shown as having the same diameter, but it is not essential to my invention that this be the case. A cable according to my invention could be made with all the 25 wires shown in the figures of composite construction. At the upper end of the cable all wires would be steel; at the lower end all wires would be metal lighter than steel. The junctions or transition points at which the composition of wire would be changed from steel to the lighter metal could be staggered along the length of the cable to provide a gradually diminishing unit weight from the top of the cable to the bottom. For cable tool drilling, however, I find it desirable to provide a cable comprising a number of wires which are steel from top to bottom, and, to obtain the desired graduation in unit weight of cable, a number of composite wires.

The three grades of steel commonly used in wire rope for drilling cable are mild plow steel having an average ultimate tensile strength of 206,000 pounds per square inch, plow steel having an average ultimate tensile strength of 230,000 pounds per square inch, and improved plow steel having an average ultimate tensile strength of 264,000 pounds per square inch. It will be understood that the steel wires in my cable may be ofone, two or all of these grades of steel, or in fact of other grades if they prove economical.

The metal lighter than steel which I prefer to use is aluminum, although my invention is not limited to this metal in combination with steel, or in fact to any specific metals. The aluminumv generally used for Wire rope has an average tensile strength of about 70,000 pounds per square inch, and is only a little over one-third as heavy as steel. It is therefore possible to obtain a maximum over-all graduation in cable weight from top to bottom of nearly 3 to 1, and a similar graduation in cable tensile strength of between 3 and 4 to 1. Furthermore, aluminum and teel-may be used together in the same strand or cable without damaging electrolytic corrosion taking place as, although aluminum is slightly anodic to steel, it quickly forms a protective coating and behaves in a more or less neutral fashion.

One embodiment of my invention is a cable 7,000 feet long comprising 6 identical strands of 25 wires, each of these trands being composed of .4 21) illustrates the 4500-5000 feet section and Figure 20 illustrates the 5000-5500 feet section.

The strand length is measured from the end which would be at the bottom of the hole in drilling. It will be seen that a strand formed as tabulated above has a proportion of steel to aluminum that increases in steps from one end to the other. Other arrangements of wires in the strand are possible, and my invention embraces a cable constructed of several strands, each of which may consist of a different arrangement of steel and aluminum wires. In every such case, however, the diameter of the cable remains uniform from 'top to bottom as do the diameters of the strands and the individual wires composing each strand.

The mechanical properties of a cable comprising 6 identical strands arranged as in Table I are listed below. The tool weight assumed in calculating the safety factor was 3,500 pounds for the first 3,000 feet of hole drilled, 2,500 pounds for the next 2,000 feet, and 2,200 pounds for the last 2,000 feet. These weights correspond aluminum wires of the grade above mentioned and steel wires of all three grades above mentioned, arranged as in the following table.

Table I Strand I iength Steel Wires Aluminum Wires Feet 02,500.. l 1; 2a through 2]; 30.

th h

4a through 4m (Mild Plow St el e roug 4a through 4m (Plow Steel) awe-7,000-..

Plow Steel); 4a through 4m (Plow Steel).

As has been mentioned, Figure 2a illustrates the 4000-4500 feet section tabulated above, Figure 1 Rounded to nearest whole number.

Wire strands, according to my invention, may be conveniently manufactured in either of two ways. The first method employs separate spools of steel and aluminum wire at the strander. stranding is commenced with steel wires, for example, if the cable'is to be formed with all wires of steel at one end, or with wires of steel and wires of aluminum if it is desired to have some wires of the latter metal throughout the cable. After the desired number of feet of strand of the initial arrangement of wires is formed, the strander is stopped and the desired steel wires are cut and joined to aluminum wires of the same diameter. The stranding machine is then started up and the stranding continued for a measured footage, and the machine again stopped and additional steel wire is cut and joined to aluminum wire, and so on. The second method of manufacture, and one that I prefer to employ, requires the composite wires used in each strand to be formed in advance of the stranding. The required length of steel wire is measured, cut, and then joined to the required length of aluminum wire to form each composite strand, and these strands are reeled up on spools which are then loadedv into the stranding machine. The stranding of these prefabricated composite wires can then proceed without in terruption. It will be understood that the aluminum and steel wires may be joined by welding or other suitable means.

As cable formed according to my invention must be utilized so that the light end is the loadcarrying end, it is necessary that the two ends of the cable be marked so that identification of the light and heavy ends respectively may be made. 1

Although I prefer to use aluminum as the lighter weight metal in the composite wires of my cable, other light weight metals may be used, such as magnesium, or light metal alloys such as the alloys of aluminum, zinc and magnesium.

Although I have described and illustrated the present preferred embodiment of my invention, it will be understood that the invention is not limited thereto but may be otherwise embodied or practiced within the scope of my claims.

I claim:

1. A cable composed of continuous wires, including a plurality of composite wires formed of steel at one end and a metal lighter than steel at the other, the junctions between steel and lighter metal in the composite wires being staggered over the length of the cable.

2. A cable composed of continuous composite wires formed of steel at one end and a metal lighter than steel at the other, the junctions between steel and the lighter metal being staggered over the length of the cable to provide a progressive decrease in unit cable weight from one end to the other.

3. A cable composed of continuous wires of substantially constant cross-section, including a plurality of composite wires formed of steel at one end and a metal lighter than steel at the other, the junctions between steel and lighter metal in the composite wires being staggered over the length of the cable to provide a progressive decrease in unit cable weight from one end to the other.

4. A cable composed of continuous wires, including a plurality of composite wires formed of steel at one end and a metal lighter than steel at the other, the junctions between steel and lighter metal in the composite wires being staggered over the length of the cable to provide a cable of substantially uniform diameter but progressively decreasing unit weight from one end to the other.

5. A cable composed of continuous wires, including a plurality of composite wires formed of steel at one end and aluminum at the other, the junctions between steel and aluminum in the composite wires being staggered over the length of the cable to provide a progressive decrease in unit cable weight from one end to the other.

ROBERT L. STANTON.

No references cited.

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