US3244103A

US3244103A - Electrical safety detonator

Info

Publication number: US3244103A
Application number: US345242A
Authority: US
Inventors: Gerald V Spickard
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1964-02-17
Filing date: 1964-02-17
Publication date: 1966-04-05
Anticipated expiration: 1983-04-05

Description

April 5, 1966 G. v. sPlcKARD ELECTRICAL SAFETY DETONATOR Filed Feb. 17, 1964 I NVEN TOR.

ATTORNEY United States Patent O 3,244,103 ELECTRICAL SAFETY DETONATR Gerald V. Spickard, Houston, Tex., assignor to Schlumberger Weil Surveying Corporation, Houston, rllex., a corporation of Texas Filed Feb. 17, 1964, Ser. No. 345,242 2 Claims. (Cl. M12-28) This invention relates to electrical safety detonators for use in well bores in detonating explosive shaped charges and, more particularly, relates to detonators which are useful where exposed to excessive well bore pressures and temperatures.

In general, weil bore perforating apparatus using shaped charges may be conveniently divided into the so-called carrier-type and the so-called capsule-type apparatus. The relative advantages and disadvantages of the two types need not be described herein, it being suficient to note that the present invention has a particularly useful application with capsule-type well perforators, such as that shown in Patent No. 2,981,185.

- Generally, in capsule-type perforators, shaped charges are individually encapsulated so as to be waterproof. The shaped charges are either linked together to form a chain-like assembly of charges or arranged on a mounting, such as a strip, for lowering into a well bore which is to be perforated. A waterproof blasting cord for detonating the shaped charges is secured to the rear of each charge and a waterproof electrically operated detonator or blasting cap is provided for igniting or detonating the blasting cord. A blasting cap or detonator typically includes a primer explosive which is ignited when an igniter wire is heated by an electric current. The primer explosive, in turn, sets off a booster explosive which develops sufficient energy to detonate the lesssensitive explosive in the blasting cord. Accordingly, to detonate the shaped charges, an electrical current is passed from the surface of the ground through electrical conductors of a cable to the detonator in the well bore. Passage of current through the blasting cap igniter then initiates a chain reaction which subsequently detonates the shaped charges.

It will be appreciated that the components of such capsule perforators, e.g., the blasting cap, blasting cord and encapsulated shaped charges, are subjected to the ambient conditions in the well bore and that these components will generally fail, or at best not function properly, should well iiuids leak into them before they are operated. Accordingly, considerable effort has been expended in devising duid-tight components to keep pace with the higher pressures and temperatures corresponding to the ever-increasing depths to which oil wells are currently being drilled.

A particular source of failure heretofore has been caused by well fluids under pressure leaking into a sealed detonator at the point where the insulated electrical leads enter the sealed detonator case. Such leakage is generally attributed to the inability of common electrical insulations to withstand high pressures without leaking as well as the difficulty inmaintaining a fluid seal between the insulation and the metal conductor itself. As a consequence, it has been found that conventional detonators give serious trouble in service where ambient well conditions exceed 8,00010,000 p.s.i.g, and approximately 200 F.

It is, therefore, an object of this invention to provide a new and improved detonator means for well bore shaped charge perforators which are capable of reliable operation at high pressures and temperatures.

Another object of this invention is to provide new and improved detonator means which have a high-pressure fluid-tight seal.

It is a further object of this invention to provide new and improved detonator means with positive sealing against uid leakage around electrical conductors entering the detonator means.

The detonator means of the present invention is comprised of a hollow metal blasting-cap case having an open end and arranged to receive a conventional electrically ignited blasting cap which has at least one electrical conductor connected thereto. A metal closure member arranged for fluid tight sealing in the open end is provided with a passage therethrough for sealingly receiving a metal conductor pin which is electrically insulated by a surface treatment.

When the detonator means is assembled, the conductor pin is sealingly engaged within the closure member passage and a blasting cap conductor is internally connected within the case to the inner end of the conductor pin. The outer or external end of the conductor pin is adapted for subsequent connection to a source of electrical energy.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a sectional view of a preferred embodiment of a detonator constructed in accordance with the principles of the present invention; and

FIG. 2 is an enlarged view of a portion of FIG, l.

As seen in FIG. l, a hollow blasting cap case 10 is formed of metal with sucient thickness and strength to withstand high pressures encountered in a well bore. Case 10 has a centrally located longitudinal cavity or bore 11 which is closed at one end by a transverse web 12 and has an opening 13 at the other end. The opening 13 of cavity 11 is counterbored, as at 14, to form an intermediate annular shoulder 15 facing the opening.

A conventional electrically ignited blasting cap 16 is disposed within cavity 11 with its nose in close proximity to web 12 and its

electrical leads

17, 18 extended toward opening 13. A metal closure member 19 is sized for reception in counterbore 14 and has two

longitudinal passages

20, 21 extending therethrough. Although closure member 19 could be sealed by soldering and the like, a peripheral groove 22 is provided around closure member 19 to receive an O-ring 23.

As seen in FIGS. l and 2, the

passages

20, 21 through closure member 19 are counterbored, as at 24 and 25, to provide intermediate outwardly facing

shoulders

26, 27.

Metal pins

28, 29, of a metal which conducts electricity easily, are sized for reception in

passages

20, 21. Each of these conductor pins has an intermediate enlarged-

diameter portion

36, 31 which respectively have

peripheral grooves

32, 33 for receiving O-rings 34, 35'. Although other means for connecting could be provided, it is preferred to form short

axial passages

36, 37 into each end of

conductor pins

28, 29 for receiving the ends of electrical conductors.

It will be understood, of course, that conductor p-

ins

29, 29 must be electrically isolated from one -another as Well as from closure member 19 and receptacle 1.0. Accordingly, it is preferred to make conductor pins 2S, 29 of aluminum and, as indicated by the dotted markings on pin `29 in FIG. 2, to hard-anodize the coextensive outer surfaces of

conductor pins

28, 29 that could be brought into contact with closure member 19. It has been found that for the relatively low voltages customarily used in the perforating art, such hard-anodizing to a depth of about 0.00l-0.002 inch provides an excellent electrical insulation or dielectric on the surfaces of the conductor pins while still permitting transmission of electricity through the central portion of the body of the pins. Accordingly, it will be appreciated that by anodizing the

conductor pins

28, 29, only the annular spaces around the pins require fluid sealing and that now a high-pressure O-ring sealing member can be successfully used to seal olf this space.

Although it is not essential, it is nevertheless preferred to make closure member 19 also of aluminum and hardanodize at least its outer surfaces to provide a second insulating surface should one of the conductor pins be inadverently shorted to the closure member. The use of aluminum will also permit the surfaces of

passages

20, 21 to be anodized should further insulation be desired.

At the opposite end of case from closure member 19, an axial recess 40 is provided for receiving either the end of a detonating cord or, where necessary, a conventional Huid-tight encapsulated booster charge 41. Booster charge 41 is customarily provided with a recess 42 into which the end of a detonating cord (not shown) is inserted and secured while assembling the perforating apparatus. The lbooster charge 41 is disposed within recess 40 with its inner end being separated from the inner end of blasting cap 16 by only the transverse web 12 of case 10. Thus, it will be appreciated that when blasting cap 16 is detonated, the explosion thereof will perforate web 12 and detonate booster charge 41.

In assembling the detonator of the present invention,

conductor pins

28, 29 are sealingly disposed within

passages

20, 21 of closure member 19, and, as seen in FIG. 2, the exposed ends of blasting cap

electrical leads

17, 18 are inserted into axial passages 37 in the inner ends of conductor pins and crimped and xed in place, as at 39. Similarly, short lengths of

electrical conductors

42, 43 are inserted into the axial passages 36 in the outer ends of

conductor pins

28, 29 and crimped and fixed in place as shown at 38. The bared terminal ends of

conductors

42, 43 are then temporarily twisted together, as at 44, to ensure that stray electrical charges will not prematurely detonate blasting cap 16. O-ring 23 is disposed within peripheral groove 22 of closure member 19, and the sub-assembly inserted into cavity 11 of case 10.

The remaining terminal portion of counterbore 13 is then filled with electrically nonconductive plastic 45, such as an epoxy, to secure

conductor pins

28, 29 and closure member 19, as well as to prevent well uids from contacting the outer ends of

conductor pins

28, 29.

The booster charge 41 is inserted into axial recess 40 at the opposite end of receptacle 19 and similarly sealed in place with a plastic material 46.

Although anodized aluminum is the preferred material for

conductor pins

28, 29, similar results could be obtained with other metal-surfacing processes, such as phosphating, where such treatment of an electrically conductive metal will produce an electrically nonconductive surface around the pin.

Accordingly, -it will be appreciated that the new and improved detonator of the present invention is capable of withstanding the extreme pressures and temperatures encountered in deep well bores. The electrical conductors are positively uidly sealed `as well as electrically insulated in such a manner as to provide a new and improved detonator capable of withstanding high well temperatures and pressures without leaking uids which otherwise would short electrical leads and deactivate the blasting cap.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a detonator including a hollow case with an open end; an electrically-ignited blasting cap disposed within said case; and a metal closure member sealingly closing said open end against entry of fluid and having at least one passage extending therethrough, the improvement comprising: an electrically-conductive metal conductor member providing an electrical connection between said blasting cap and the exterior of said closure member and having a shoulder abutting said closure member and peripheral surface portions received in complementary surface portions of said passage, at least one of said metal conductor and closure members being of aluminum and having its surface portions anodized to provide electrical 4insulation between said members; and seal means for pressure sealing said conductor member in and relative to said closure member including an annular sealing ring sealingly engaged between said metal conductor and closure members.

2. In a detonator including a hollow metal case with an open end and an electrically-ignited blasting cap disposed within said case, the improvement comprising: a metal closure member having at least one passage eX- tending therethrough and sealingly engaged with said case to close said open case end against entry of uids, said passage having an outwardly-facing shoulder intermediate its ends; an electrically-conductive metal conductor member extending through said passage into said case and electrically connected to said blasting cap, said conductor member having an enlarged diameter portion complementarily received in the outer portion of said passage `and adapted to engage said `outwardly-facing shoulder, at least one of said metal conductor and closure members being of aluminum and having its coextensive surface portions anodized to provide electrical insulation between said members; and means for uidly sealing said metal conductor member relative to said closure member consisting of an annular sealing ring disposed in said outer passage portion and sealingly engaged between said closure member and said enlarged diameter portion of said metal conductor member.

References Cited by the Examiner UNITED STATES PATENTS 1,516,009 11/1924 Grant et al. 102-28 X 1,617,675 2/ 1927 Djidics 102--28 2,161,636 6/1939 Rankin et al 204-1 2,953,720 9/ 1960 Engel 315-209 2,981,186 4/1961 Stresau 102-28 3,059,576 10/1962 Haefner 102-28 3,110,845 11/1963 Ott 102-28 X 3,159,103 12/1964 Bagley 102-28 3,175,492 3/1965 Reyne et al 102-28 BENJAMIN A. BORCHELT, Primary Examiner.

R. V. LOTTMANN, Assistant Examiner.

Claims

1. IN A DETONATOR INCLUDING A HOLLOW CASE WITH AN OPEN END; AN ELECTRICALLY-IGNITED BLASTING CAP DISPOSED WITHIN SAID CASE; AND A METAL CLOSURE MEMBER SEALINGLY CLOSING SAID OPEN END AGAINST ENTRY OF FLUID AND HAVING AT LEAST ONE PASSAGE EXTENDING THERETHROUGH, THE IMPROVEMENT COMPRISING: AN ELECTRICALLY-CONDUCTIVE METAL CONDUCTOR MEMBER PROVIDING AN ELECTRICAL CONNECTION BETWEEN SAID BLASTING CAP AND THE EXTERIOR OR SAID CLOSURE MEMBER AND HAVING A SHOULDER ABUTTING SAID CLOSURE MEMBER AND PERIPHERAL SURFACE PORTIONS RECEIVED IN COMPLEMENTARY SURFACE PORTIONS OF SAID PASSAGE, AT LEAST ONE OF SAID METAL CONDUCTOR AND CLOSURE MEMBERS BEING OF ALUMINUM AND HAVING ITS SURFACE PORTIONS ANODIZED TO PROVIDE ELECTRICAL INSULATION BETWEEN SAID MEMBERS; AND SEAL MEANS FOR PRESSURE SEALING SAID CONDUCTOR MEMBER IN AND RELATIVE TO SAID CLOSURE MEMBER INCLUDING AN ANNULAR SEALING RING SEALINGLY ENGAGED BETWEEN SAID METAL CONDUCTOR AND CLOSURE MEMBERS.