US 2935021 A
Description (OCR text may contain errors)
May 3, 1960 J. R. NILEs 2,935,021
WELL TREATING APPARATUS Filed April 4. 1956 68 78 2 T 60\` T /J'-lm l 38 ,J g- \88 74 U50 66 l? |54 (/84- .l ufecoun/` *82 L I, /no/fca/or i :e -f i y l VH 7 ,2o i0/ 2?" q 1 /o I l, A
IN VEN TUR. Joh n A. Niles nected in series with the perforating device.
Unite arent WELL TREATING APPARATUS John R. Niles, St. Clair Shores, Mich., assigner to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application April 4, 1956, Serial No. 575,991
'5 Claims. (Cl. 10220) 1 This invention relates to a method of and apparatus for selectively operating from a cable having a single insulated conductor two electrically operated bore hole logging or treating devices.
`Oil or gas wells are often completed by running a string of casing to the bottom of the bore hole and then forcing cement through the casing and into the space between the. well bore wall and the casing. Cementing the casing in place in the well bore effectively prevents uids emanating from one or more strata along the well bore from contaminating another stratum. However, the cementing operation usually seals off the oil producing strata as well as those strata which are capable of producing undesired fluids or which are capable of absorbing uids.
Customarily the casing and cement are perforated adjacent to the oil producing strata in order to permit oil from the producing strata to enter the casing. Perforation of the casing and well bore wall (including cement) is usually accomplished by suspending a perforating gun (which contains bullets or shaped explosive charges) from a suitable electric cable and lowering the gun into the well bore until the gun is beside the producing formation, and then firing the gun.
Although the depth the producing formation lies bclow the surface of the earth is usually known from data taken as the well is drilled, it is not customary to rely onsuch data in determining where the casing is tov be perforated. Usually a radioactivity log is made of the vformationsadjacent to the well bore and the perforating gun. or guns are disposed, for firing, at the depth or depths indicated by the well survey of the radioactivity of the formations. The locating of the perforating gun adjacent to the desired formation has, in the past, been somewhat time consuming in that the well bore logging device is first lowered into the well bore to make the log of radioactivity of the adjacent formations and then must be removed from the well bore before the perforating gun is lowered into the well bore. Usually the well' bore logging devicev and the perforating gun are lowered, 'although at different times, on the same cable in order to avoid possible errors in depth measurement which might occur it two different cables were used.
Accordingly, a yprincipal object of this invention is to provide an improved apparatus and method for selectively operating a well bore surveying device and a well bore perforating gun from an electrical cable having only on insulated conductor. f
In accordance with this inventionV there is provided a radiation detector and a well bore perforating device electrically connected in parallel to the same insulated conductor of a cable, there beinga spark gap device con- The cable supports the devices as they are lowered into a well bore. The radiation detector and the perforating device are physically disposed side by side. as they are lowered into the well bore., The radiation detector' is operable at a potential which is Aincapable of breaking down the spark 2,935,021 Patented May 3,119.60.--
The invention, as well as additional objects and advan.-
tages thereof, will best be understood when the followingl detailed description is read in connection` with the accompanying drawing, in which the single figure shows in, diagrammatical form, the apparatus of this, invention.
Referring to the drawing, there is shown a well bore, indicated generally by the numeral 10, extending from the surface 12 of the earth through various strata or earth formationsl 14, 14a, 14h. The well bore 1t) contains a string of casing 16 which extends from ythe earths surface 12 to. near the bottom 18 of the well bore 10. Thespace between the casing 16 and the wall 29 of the well bore is illed with cement 21 from the bottom 18 of the well bore to a point along the wall of the well bore which is abovek zones which produce unwanted fluids.
Disposed within the well bore 10 is a cable, indicated generally by the numeral 22, which includes an inner, insulated conductor-24 and a grounded conductor 26 which is commonly, but not necessarily, the me-tal vsheathing which surrounds the inner conductor 24. The conductor 26 thus comprises the load carrying part of the cable 22.
Above the surface 12, the cable 22 passes overfa sheave I 27 supported by a derrick 28 and is coiled onto ay reel 30. The inner conductor 24 of the cable 22 is connected to a comrnutator element 32 on the reel 30 and electrical, connection to the insulated conductor 24 of the cable 22 is made through a brush contact member 34. As illustrated in the drawing, it is assumed that the outer con--y ductor 26 is the metal, load carrying outer part of the cable 22v and that the conductor 26 is grounded', as indicated by the ground connections 36, 38 at any convenient point, as through the reel 30 and derrick 28 to the earth 12, for example.
A perforating gun 40, which includes an electrical ring means 42 associated with it, is held by the lower end 44 of the cable 22 and has its tiring means electrically connected to the inner conductor 24 of the cable through a calibrated spark gap 45. The iiring means is also grounded, as indicated by the ground connection 46.V A condenser 48 is connected in parallel with the tiring means` 42- The condenser capacitance is large with re.` spect to the line capacitance to insure that accidental discharge of the line capacitance would not detonatethe tiring means 42.
A Geiger-Muller tube 50, has its anode-52 connected to the conductor 24 of the cable through a series resistor 54 and is disposed beside the perforating gun, 4.0. The cathode electrode 56 of the radiation detector 50' is grounded through the ground connection 58.v Y Y A power source, indicated generally by the numeralV 60 is illustrated as two batteries 62, 64 connected in series with the cathode of the battery 64 grounded, as at 66. The lead 68 connects the two batteries 62, l6 4 to a terminal of a multiple terminal switch 70; The lead 72 connects the anode of the battery 62 to another terminal of the switch 70. The switchf70 is coupled' through a series resistor 74 and lead 76 to the commutais coupled` to the commutator bar 34 through the lead i electrical connections between the conductor 24 and the.
gun 40 and detector 50 being made through suitably enclosed connectors (not shown) to prevent the inner conductor 24 from being grounded directly and not through the desired loads (that is, through the detector 50 and the gun 40). The Geiger-Muller tube 50, is energized by connecting the arm S8 of the switch 70 to the anode lead 68 of the battery 64. It will be assumed that the battery 64 provides a direct current potential, say 1000 volts, which is suicient to energize and operate the tube 50 but is not sufficient to break down the calibrated spark gap 45 which may comprise two spaced apart electrodes in a hermetically sealed container filled with a suitable gas at a suitable pressure. An example of the general type of spark gap 45 is a T-R (transmit-receive) box unit used to short out antenna leads to radar receivers during the time a powerful nearby transmitter is in operation.
The spark gap 45 may, for example, be one which will not break down (ionize the gas between its terminals) at the potential required to operate the radiation detector 50 but which will break down when a higher potential is applied to detonate the perforating gun 40.
With the radiation detector energized, the detector 50 and gun 40 are moved up and down the well bore to determine the radioactivity of the adjacent earth formations. As gamma rays from the various formations strike the detector 50, pulses are transmitted up the cable 22 and are coupled through the lead 84 and condenser 86 to a pulse count indicator 80 of suitable design.
When the radioactivity survey indicates that the gun 40 and detector 50 are disposed beside the desired earth strata or formation 14, the switch 78 is then closed to short out the resistor 74 which is a current limiting resistor. (With the current limiting resistor in the firing circuit, the current passing through the firing circuit with the spark gap 45 broken down and conducting, would be insufcient to detonate a tiring means 42 such as a blasting cap which requires at least an ampere of current.) The resistor 74 also provides an impedance across which the pulses from the detector 50 are built up. The arm 88 of the switch 70 is then turned to the terminal connected to the lead 72 and the full potential (batteries 62, 64 connected in series) of the power source 60 is applied across the tiring circuit and across the radiation detector 50. The series resistor 54 prevents an unduly large current passing through the tube 50 in event the tube 50 ionizes and breaks down when the high, gun firing potential is applied across the tube, thus permitting a sufcient voltage to be developed across the resistor 54 to permit the ring of the gun 40.
Although batteries 62, 64 have been described as the component parts of the power source 60, a rectified A.C. power source, suitably filtered, may also be used to provide the direct current needed for the operation of the Geiger-Muller tube.
When the full potential, say 2,000 volts, of the power source 60 is applied to the tiring source, the spark gap 45 ionizes and breaks down, applying the full potential of the power source 60 across the detonating or firing means 42. Under such conditions suicient current (usually an ampere or more as compared with a few milliamperes to operate the tube 50) flows through the firing means 42, usually a blasting cap, to detonate or re the perforating gun 40. The perforating gun 40 may be of the structural type shown in U.S. Patent No. 2,733,657 to C. M. Bryant, et al., for example, and having detonating means of the blasting cap type requiring an ampere or more of current. The charges of the gun, which usually are of the well known shaped charge type, perforate the casing and cement when tired, permitting 4 uid from the adjacent earth formations 14 to flow into the casing 16. The explosion attendant to the tiring of the gun 40 normally shatters the gun 40, the spark gap 45, and the Geiger-Muller tube 50, leaving no large sections of material to possibly interfere with the operation of the well.
While the radiation detector 5t) has been described as being disposed in side-by-side relationship with the gun V 40, the detector 50 could be disposed either above or below the gun 40. In event the detector 50 is not disposed beside the gun 40, an explosive charge (adapted to be detonated when the gun 40 is fired) could be placed adjacent to or aimed at the detector 50 to insure that the detector 50 was broken up into very small fragments.
The Geiger-Muller tube may be made of glass tubing having a wire anode axially disposed therein. The tube is filled with a suitable gas at a suitable pressure, as is well known in the art of making Geiger-Muller tubes, to permit the operation of the tube at a desired potential. The cathode of the tube may, for example, be an aquadag coating on the outer wall of the glass tube. The above description of a Geiger-Muller tube is merely by way of example to show one suitable tube. Other Geiger-Muller tubes may be used in accordance with this invention.
The detonating device 42 may alternatively comprise an electrical resistance element.
The resistor 74, mentioned before, is inserted in series with the lead 76 to the commutator brush 34 to prevent enough current being passed through the conductor 24 t0 fire the perforating gun 40 in event the full output of the power source 60 were accidentally applied to the A conductor 24. The switch 7S permits the shorting out of the resistor 74 when it is desired to tire the gun 40.
It is thus apparent that this invention provides a simple means for locating a perforating gun 40 opposite a desired earth formation as the gun 40 is lowered in a well bore 10. This invention eliminates the usual time consuming separate radioactivity survey run into the well bore 10 and permits survey and tiring of the perforating gun to be done in one instrument run into the well bore.
l. Apparatus for locating a desired earth formation which is penetrated by a well bore and for positioning an explodable perforating device adjacent to said desired earth formation and then detonating said perforating device, comprising, a cable having a single insulated conductor and a ground return conductor therein, said cable having an upper end and a lower end, a rst circuit comprising a resistor and a Geiger-Muller tube comprising an anode electrode and a cathode electrode, said Geiger- Muller tube being disposed beside said perforating device,
^ said resistor having a terminal which is electrically connected to said anode electrode and having another terminal which is electrically connected to said insulated conductor at the lower end of said cable, said cathode being electrically connected to said ground return conductor at the lower end of said cable, a second circuit comprising a calibrated spark gap having two electrodes, a current actuated detonating means for said perforating device, said detonating means having two electrical leads thereto, and a condenser, one electrode of said spark gap being electrically connected to said insulated conductor at the lower end of said cable, another electrode of said spark gap being connected to one electrical lead of said detonating means, the other electrical lead of said detonating means being electrically connected to said ground return conductor at the lower end of said cable, said condenser being electrically connected in shunt across said detonating means, a radiation pulse count indicator, means coupling said pulse count indicator to said insulated conductor of said cable, a power source having high and intermediate output potentials, and means for selectively applying said potentials between detonating means includes a resistance heater element.
4. Apparatus in accordance with claim 1, wherein said detonating means is a part of a well bore perforating device.
5. Apparatus for locating a desired earth formation which is penetrated by a well bore, for positioning an explodable perforating device adjacent to said desired earth formation and then detonating said perforating device, comprising, a cable having a single insulated conductor and a ground return conductor therein, said cable having an uptzr end and a lower end, a first circuit comprising a Geiger-Muller tube comprising an anode electrode and a cathode electrode, said tube being disposed beside said perforating device, said anode electrode being connected to said insulated conductor at the lower end of said cable, said cathode being electrically connected to said ground return conductor at the lower end of said cable, la second circuit comprising a calibrated spark gap having two electrodes and a current actuated detouatlng means for said perforating device, said detonating means having two electrical leads thereto, one electrode of said spark gap being electrically connected to said insulated vconductor at the lower end of said cable and another electrode of said spark gap being connected to one electrical lead or" said detonating means, the other electrical lead of said detonating means being electrically connected to said ground return conductor at the lower end of said cable, a radiation pulse count indicator, means couplingv said pulse count indicator to said insulated conductor of said cable, a power source having high and intermediate output potentials, and means for selectively applying said potentials between said insulated conductor and said ground return conductor.
References Cited in the file of this patent UNITED STATES PATENTS.
2,309,835 Fearon Feb. 2, 1943 2,349,041 Hare May 16, 1944 2,370,909 Martin Mar. 6, 1945 2,725,821 Coleman Dec. 6, 1955 2,732,518 Bricaud Jan. 24, 1956