US2912932A - Well treating apparatus - Google Patents

Description

Nov. 17, 1959 E. D. AYERS WELL TREATING APPARATUS Filed April 4, 1956 INVENTOR Ear/D. ge/S BY HTTONE YS ire This invention relatesto a method of and apparatus for selectively operating through the same electrical conductors of a supporting cable two electrically operated bore hole logging or treating devices.

Oil or gas wells are often completed by running 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 other strata. However, the cementing operation usually seals ott the oil producing strata as well as those strata which are capable of producing undesired iluids or which are capable of absorbing fluids.

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 from a suitable electric cable and lowering the gun into the well bore until the gun is beside the producing formation, and then ring the gun.

Although the depth below the earths surface of the producing formation is usually known from data taken as the well is drilled, it is not customary to rely on such data in determining where the casing is to be perforated. Usually a radioactivity log is made of the formations adjacent to the well bore and the perforating gun is disposed, for ring, at a depth indicated by the well survey of the radioactivity of the formations. This 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 device and the perforating gun are lowered on the same cable (although at different times) in order. to avoid possible errors in depth measurement which might occur if two diierent cables were used.

Accordingly, a principal 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 the same electrical conductors of a cable containing at least two electrical conductors, one` tector and the perforating device are disposed side by sidel as they are lowered into the well bore. The radiation detector has an anode which is connected directly to the insulated conductor and a ycathode which is connected to a detonating means requiring a relative heavy current (as '2,912,932 Patented Nov. 17, 1959 compared to the detector current) to tire it. The detonating means is connected to a ground return conductor. When the desired radiation pattern is received and identified through radiation counting apparatus located at the surface, the potential on the cable is increased suciently to break down the radiation detector and re the perforating device. Both the radiation detector and `the perforating device are made of frangible material which is broken into small pieces by the explosion of the perforating device.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which:

Fig. l shows, in diagrammatical form, the apparatus of this invention.

Referring to the drawing, there is shown a well bore, indicated generally by the numeral lt), extending from the surface l2 of the earth through various strata or earth formations 14, 14a, Mb. The well bore contains a string of casing i6 which extends from the earths surface 12 to near the bottom i3 of the well bore 1t). The space between the casing 16 and the wall 20 of the well bore is filled with cement 21 from the bottom 18 of the well bore to the earths surface l2, for example.

Disposed within the well bore lil is a cable, indicated generally by the numeral 22, which includes an inner, insulated conductor 24 and a grounded conductor 26 which yis commonly, but not necessarily, the metal sheathing or load carrying part of the cable 22.

Above the surface l2, the cable 22 passes over a sheave 27 supported by a derrick 2S and is coiled onto a reel 39. The inner conductor 24' is connected to a commutator element 32 on the reel 3) 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 conductor 26 is the metal, load carrying outer part of the cable 22 and that the conductor 26 is grounded, as indicated by the ground connections 36, 38 at any convenient point, as through the reel 39 and derrick 28 to the earth 12, for example.

A perforating gun, indicated generally by' the numeral 40, and a radiation detector, a Geiger-Muller tube, indicated generally by the numeral 42, are attached at the lower end 44 of the cable 22. The gun 40 and tube 42 are, in practice, physically disposed side by side. The anode 46 of the tube 42 is electrically connected to the inner or insulated conductor 24- of the cable 22. The cathode 48 of the tube is electrically connected to the detonating means of the gun 4G, commonly a blasting cap S0 requiring an ampere or more of current to detonate it. The blasting cap 50 also is electrically connected to the ground return conductor 26 by any convenient means such as the ground `connection 52.

A fuse 54 which is capable of carrying current of the order of a few milliamperes is connected in shunt across the detonatng means 50. A condenser 56 is also connected in shunt across the detonating means 50. Although the detonating or tiring means 50 for the perforating gun 40 may be a blasting cap, other current actuated devices such as a resistance heating element (not shown) adapted to ignite a powder charge upon the passage through the element of a specified current may be used in ring the gun 40.

A power source, indicated generally by the numeral 6G, 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, 64 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 switch 70 is coupled through a series resistor 74 and lead 76 to the commutator brush 34. A switch 78 is connected in parallel with the resistor 74 and permits the resistor '74 to be lay-passed, for reasons which will be explained later.

A pulse count indicator 80, which may be energized by any suitable source of power (not shown) is connected to ground as indicated by the connection 82 and is coupled to the commutator bar 34 through the lead 84 and the condenser 86.

In operation the perforating gun y4t) and radiation detector 42 are attached to the end 44 of the cable 22 with electrical connections between the conductor 24 and the gun 40 and detector 42 being made through suitably enclosed connectors (not shown) to prevent the inner conductor 24 of the cable 22 from being grounded directly and not through nthe desired loads (tube 42 and gun 40). VThe radiation detector 42, a Geiger-Muller tube, is energized by connecting the arm 88 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 1'000 volts, which is sufficient to energize and operate the tube 42 but is not sufficient to break down the tube and cause it to conduct heavily, thus tiring the detonator means. The fuse 54, which will safely carry the current needed to operate thetube 42, shunts current around the detonating means 50 to the ground return conductor 26 through the ground connection 52.

With the radiation detector energized, the detector 42 and gun 40 are moved up and down the well bore 10V to determine the radioactivity of the adjacent earth formation.

v22 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 4t) and detector 42 are disposed beside the desired earth series) of the power source 60 isapplied across the radiation detector 42 and across the detonating meansV 50, fuse 54, and condenser 56. The Geiger-Muller tube 42 breaks down and conducts heavily when the higher gun tiring potential is applied across the tube 42, thus permitting aisuiicient current to pass through theV detonator means 50 to permit the tiring of the gunr40.

When the full potential, say 2,00() volts, of the power source 60 is applied to the ringsource, the tube 42y ionizes and breaks down, applying the full potential of the power source 60 across the detonating or'tiring means 50.V Under such conditionsA suflicient current ows to blow the fuse 54, causing all the current to flow through the `tiring means 5t), usually a blasting Vcap which res when an ampere of current passes thro'ughV it, to fire the perforating gun 40. The perforating gun 40 may be ofV the structural type shown in `U.S. Patent No. 2,733,657 to C. M. Bryant et al., forexample, whichhas incorporated therein detonating means of the blasting cap type requiring an ampere or more of current to detonate it."

The charges of the gun, which usually are of the Well known shaped charge typejperforate the casing and cement when iirCCL permitting uid yfrom the adjacent earth ,formations 14' tok ow into lthe Vcasing 16.l The explosion attendant to the tiring of the gun 4u normally shatters the gun 40 and theV Geiger-Muller tube 50,'

As gamma rays from the Various formations strike the detector 42, pulses are transmitted up the cable leaving no large sections of material to interfere with the later operation of the well` The perforating gun 40 and Geiger-Muller tube 42 are described heretofore as being disposed side-by-side. The Geiger-Muller tube 42, however, may be disposed either above or below the gun 40. Thus, in operation of the invention when the detector tube 42 is not beside the gun 40, the zone or strata to 'be shot is located by the detector tube 42 and the gun is then raised or lowered a short distance to the indicated shooting position. An explosive charge, adapted to detonate when the gun 40 is tired, should be provided adjacent to the tube 42 to insure that no large pieces of the tube 42 remain to clog the bore hole after the gun 40 is tired.

Further, a rectified alternating current power source, suitably filtered, may be substituted for the batteries 62, 64 of the power source 60.

The Geiger-Muller tubel may be made of glass tubing, having a lwire anode axially disposed therein and a cathode electrode Vdisposed along the inner wall of the tube.

The tube is illed with a suitable gas Vat a suitable pres-Y sure, as is well known in the art of making Geiger-Muller tubes, to permit thek operation of the tube at a desired structures permit their breaking down and conducting suflicient current to iire the gun 40 at potentials within the limitation of insulation of the cable 22.

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 to iire the perforating gun 40 in event the full output of the power source 60 were accidentally applied to the conductor 24. The switch 78 permits the shorting out of the resistor 74 when it is desired to ire the gun 40.

The fuse 54 is not necessary for the operability of this invention, but serves at least a psychological purpose in shunting current around the ring means Sti even though the current used-in operating the tube 42 would be in` suliicient to detonate the firing means.

' p It is thus apparent that this invention provides a simple means for locating a perforating gun 40 opposite a desired earth formation 14a 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 firing of the perforating gun to be done-in one instrumentrun into the well bore.

I claim:

1. Apparatus for locating a desired earth formation 'which is penetrated by a well bore, for positioning an Velectrically connected to said insulated conductor, said cathode beingelectrically connected to one of the leads of said firingmeans, the other of said ieadsjof said ring means being electrically connected to said ground return conductor, Va radiation pulse count indicator, means coupling said pulse count indicator to said insulated conductorofrsaid cable, a power-*source having high and intermediate outputV potentials, and means for selectively applyingsaid potentials ybetween said insulated conductor and said ground return conductor. y

2l Apparatus inraccordance with claim l, whereinsaid i' current actuated'iiring means is a blasting cap which is capable of being detonated on thefpassage therethrough of current o'f the orderof one ampere.

means.

6. Apparatus in accordance with claim l, wherein said means for selectively applying said potentials includes a resistor connected in series with said power source and said insulated conductor and a switch for selectively shunting out said resistor.

References Cited in the le of this patent UNITED STATES PATENTS 2,309,835 Fearon Feb. 2, 1943 2,349,041 Hare May 16, 1944 2,703,053 Castel Mar. 1, 1955 2,732,518 Bricaud Ian. 24, 1956 2,736,260 Schlumberger Feb. 28, 1956

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