Background
This invention relates to a high ambient liquid pressure-resistant electrical connector for connecting a solenoid actuated valve having a plurality of terminals to a multi-conductor electrical cable for use with an airgun lowered down into ambient liquid in a well, wherein the electrical connector may be subjected to high ambient liquid pressures.
In accord with new seismic surveying techniques, powerful impulses are generated underground in liquid in boreholes and are utilized to investigate subsurface geological conditions and formations. The powerful impulses are generated by pressurized gas discharging apparatus referred to as airguns which are fired when the highly pressurized gas is caused to be abruptly released or discharged from the airgun into the surrounding environment. Firing of the airgun is accomplished by the actuation of a solenoid valve for causing flow of pressurized gas through a passageway in the airgun, and this valve is actuated by sudden electrical energization through conductors in an electrical cable.
The integrity of the electrical connections must be maintained in difficult environmental conditions where liquid pressures deep in a borehole are extremely high. The advent of ever increasing depths of drilling in order to find new sources of petroleum increases the problem. If liquids leak or seep into the regions where the electrical terminals of the solenoid valve are connected to the electrical conductors of the cable, such connections may become short circuited or disrupted, thus causing expensive interruption of the seismic surveying.
Summary of the Disclosure
Accordingly, it is an object of this invention to provide a new and improved high ambient liquid pressure-resistant electrical connector for an airgun which prevents liquids from leaking or seeping into the regions where electrical connectors for connecting the cable to the airgun are located.
Another object of this invention is to provide a new and improved cable connector assembly for an airgun which is suitable to be lowered down deep into wells where liquid pressures are extremely high.
Still a further object of this invention is to provide a new and improved high ambient liquid pressure-resistant electrical connector for use with various types of equipment in well logging operations and other environments which is simple in construction, easy to assemble and disassemble, and which will conveniently fit into small size boreholes.
Another object of this invention is to provide a new and improved logging cable connector assembly which provides continuous protection against liquids seeping into regions where the electrical terminals and electrical connectors are located in the assembly regardless of the depths of the borehole to which the assembly is lowered.
In carrying out this invention in one illustrative embodiment thereof, a high ambient liquid pressure-resistant electrical connector is provided which connects a plurality of electrical conductors of an electrical cable to a plurality of terminals of a solenoid valve mounted on an airgun. A connector housing has a lower end and an upper end, with the lower end being mounted to an airgun. Cable clamp means are associated with the upper end of the connector for encircling the electrical cable near an end of the cable from which extend a plurality of electrical conductors attached to respective terminals of the solenoid valve of the airgun. The cable clamp means includes gripping means for providing a mechanical grip on the electrical cable encirled by the clamp means. The connector housing defines a fluid sealant chamber for enclosing the electrical terminals and adjacent portions of the respective conductors connected to the terminal. The conductor housing includes at least one barrier means for engaging the cable and being positioned between the first fluid sealant chamber and the cable clamp means. The barrier means engages the cable for providing a barrier against ambient liquid seeping past the barrier towards the electrical terminals. A cylinder space is defined in the connector housing having an inner end communicating with the fluid sealant chamber and an outer end in communication with a port of the connector housing exposed to the ambient thereby subjecting the outer end of the cylinder to ambient pressure. A movable piston is mounted in the cylinder space and has a force applying means coupled thereto for applying a continuous force for urging the piston toward the inner end of the cylinder space along with the force of ambient pressure acting on the piston. The fluid sealant chamber is provided with filling means communicating therewith and with the inner end of the cylinder space for filling the fluid sealant chamber and the inner end of the cylinder space with a waterproof fluid sealant. The water-proof fluid sealant is thus under ambient pressure plus additional pressure resulting from the continous force on the piston for enabling the fluid sealant under this additional pressure to resist seepage of ambient liquid into the fluid sealant chamber enclosing the terminals and adjacent portions of the respective conductors connected thereto.
A second sealant chamber containing fluid sealant material similarly maintained at a pressure exceeding ambient pressure is shown surrounding the end of the cable sheath where the electrical conductors exit from the cable sheath for preventing the seepage of ambient liquid within the cable sheath around the conductors.
Brief Description of the Drawings
The invention, together with further objects, aspects, advantages and features thereof will be more clearly understood from the following description taken in connection with the accompanying drawings in which like elements will bear the same reference numerals throughout the various views.
FIG. 1 is a perspective view of the logging cable connector assembly in accordance with the present invention.
FIG. 2 is an enlarged top view of FIG. 1 with certain parts broken away.
FIG. 3 is a side elevational view of FIG. 2.
FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 3 and shown enlarged.
FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 3, shown enlarged.
FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 3.
FIG. 7 is an enlarged axial sectional view taken along line 7--7 of FIG. 4.
FIG. 8 is a similarly enlarged axial sectional view taken along line 8--8 of FIG. 2.
Description of the Preferred Embodiments
Referring now to FIG. 1, the high ambient liquid pressure-resistant electrical cable connector assembly in accordance with the present invention is referred to generally by reference numeral 10 and includes an upper housing 12, an intermediate housing 14, and a lower housing 16 attached by machine screws 19 to a top airgun housing 18 of a cylindrical airgun 20. Only the upper end portion 18 of the airgun 20 is shown because the airgun itself may be conventional. The lower connector housing 16 has a solenoid valve 22 mounted therein for use in firing the airgun 20. Since the airgun 20 and solenoid valve 22 are conventional they will not be further described, and for detailed information about them, reference may be made to U.S. Pat. Nos. 3,379,273; 3,653,460; 3,808,822; 3,997,021; 3,271,924 and 4,472,794.
A multiple conductor electrical cable 24 is led to the cable connector assembly 10 through a cable clamp 26 associated with the upper connector housing 12. As will best be seen in FIG. 8, an upper end portion 31 of the upper connector housing 12 includes a first gasket seal arrangement 27 comprising a locking nut 28 having spanner-wrench sockets 30 therein, a washer 32 and a cable gasket barrier 34 surrounding the outside diameter of the cable sheath. Tightening the nut 28 in its threaded socket 29 in the upper housing end portion 31 causes the gasket 34 to jam snuggly around the outside diameter of the cable sheath.
The cable clamp 26 is split longitudinally and is fastened together around the cable 24 by machine screws 36 for gripping the cable. The lower end of the cable clamp 26 embraces the upper housing end portion 31, as seen in FIG. 8, in attached relation thereto by inturned shoulders 33. Thus, the electrical cable 24 runs longitudinally through the cable clamp 26 and through the gasket seal arrangement 27 into the upper housing 12.
A high pressure air supply hose 40 is connected through the connector assembly 10 to the airgun 20 for supplying the airgun with high pressure compressed air. This high pressure hose is attached by a hose fitting 38 and supplies a passage 42 extending longitudinally through the connector assembly 10 as will best be seen in FIGS. 3 and 8. The lower housing 16 of the connector assembly 10 includes a longitudinally extending external flange 43 for the purpose of containing the pressurized air supply passageway 42 which extends directly to an air supply passage 45 (FIG. 3) in the airgun top housing 18, thereby supplying the airgun 20 with high pressure compressed air. It is to be noted from FIG. 3 that the longitudinal external flange 43 enables the air supply passage 42 to extend past the solenoid valve 22.
The intermediate connected housing 14 (FIG. 4) is provided with "PORTS" 1 and 2 which will be explained more in detail hereafter for subjecting certain elements of the connector assembly 10 to ambient pressure. FIG. 4 includes a cross-section of the two halves 26-1 and 26-2 of the cable clamp 26 secured onto the cable 24 in gripping relationship by machine screws 36. The high pressure hose 40 extends along the outside of the cable clamp 26 in a channel 41.
The electrical cable 24 enters into the upper connector housing 12 through the gasket seal arrangement 27 as explained above. The cable 24 exits from the upper housing 12 (Please see FIG. 8) through a second gasket seal arrangement 47 comprising gasket barrier 44 which surrounds the outside diameter of the cable 24, a washer 46 and a locking nut 48 having spanner-wrench sockets 49 therein and screwed into a threaded socket 51. The cable 24 continues through a connector housing washer 50 and through a center gasket barrier 52 in a wire insert holder 54 which is provided with O-ring seals 56 and seats in an axial bore 53 in the intermediate connector housing 14. This axial bore 53 terminates at an internal annular shoulder 55 which serves to position the wire holder insert 54. The juncture of upper housing 12 and connector housing 14 is also provided with a plurality of O-ring seals 58 for preventing ambient liquids from entering the connector 10. The outer sheath 57 of the cable 24 is ended within the gasket barrier 52 in the wire insert holder 54. The inner cable sheath 59 extends through an axial passage 61 in the wire insert holder 54 and enters a fluid sealant chamber D. The inner cable sheath 59 is terminated in this sealant chamber D in the wire insert holder 54 which is filled with waterproof fluid sealant material 60, for example waterproof silicone grease, through a passage 62 leading into chamber D as will be explained later. The individual conductors 25 of the cable 24 surrounded by waterproof sealant 60 in this chamber D pass through a pair of wire inserts 64 and 65 having a gasket barrier 66 sandwiched therebetween for accommodating seven insulated conductors 25.
Two pairs of these conductors 25 are connected to terminals 67, 69 of the solenoid valve 22 for firing the airgun 20. Two of these conductors 25 are joined to one of the pair of leads 71 from a pressure transducer 68, and the seventh conductor 25 is connected to the other transducer lead 71. The transducer 68 senses the sudden pressure increase in ambient liquid caused by firing of the airgun, and this transducer transmits a signal up to the well head through the conductors 25 connected to its leads 71 for letting the operators up near the well head know that the airgun has fired properly and also to indicate and record the exact instant of firing.
The individual electrical conductors 25 of cable 24 then pass through the annular shoulder 55 and enter into chamber B in the connector housing 14 filled with waterproof sealant 60 through a grease fitting 75 (see FIG. 7) which communicates with this sealant chamber B through a passageway 77 (FIG. 7). A connector support 70 encircles the solenoid valve terminals 67, 69 and has four of the conductors 25 connected therein to the solenoid valve 22 in the lower connector housing 16. The transducer leads 71 pass through an insulating washer 72 and are sealed in the connector housing 14 by sealing screw 74.
As best seen in FIG. 7, the intermediate connector housing 14 is provided with a first cylinder space 76 carrying an axially movable piston 78 for movement therein and acted upon by a force-applying means in the form of a spring 80. This first cylinder space 76 (which is also called chamber "A") communicates with the ambient liquid surrounding the connector housing 14 through a PORT 1 on the upper end thereof. An inner end of the piston 78 applies pressure to fluid sealant 60 in this chamber A, and this chamber A communicates with chamber B through a passageway 82 (FIG. 7). A second cylinder space 84 (which is also called chamber C) is diametrically located from said first cylinder space 76 in the housing 14 and carries an axially movable piston 86 therein. This second piston 86 has a force applied thereto by a spring 88, and this piston applies the spring-loaded force to fluid sealant 60 in the chamber filled with waterproof sealant which is in communication with chamber D through passageways 90 and 62. The second cylinder space 84 communicates with ambient liquid through a PORT 2 on the upper end of the housing 14. Accordingly, ambient liquid pressure is applied through the respective PORTS 1 and 2 to each of the pistons 78 and 86 together with the continuous force resultant from the axial thrust supplied by the respective springs 80 and 88. A grease fitting 92 is provided for supplying sealant 60 through a passage 94 and passage 62 into chamber D and through passageway 90 to chamber C as illustrated in FIG. 5. The other grease fitting 75 previously described feeds waterproof sealant through passage 77 (FIG. 7) to chamber B and through passageway 82 (FIG. 7) into chamber A as shown in FIG. 7.
In operation, the connector assembly 10 is assembled with the individual conductors 25 of the electrical cable 24 connected to the terminals 67, 69 for the solenoid valve 22 and connected to the leads 71 of the transducer 68, thereby providing all of the connections which are desired to be made. Waterproof sealant 60 is then supplied through the grease fittings 75 and 92 to fill the chambers A, B, C and D with waterproof sealant material. This filling action of the fluid sealant 60 pushes the respective pistons 78 and 86 away from the inner ends of their respective cylinders 76 (chamber A) and 84 (chamber C), thereby compressing the respective springs 80 and 88 for causing these springs to exert continuous forces on the fluid sealant in the inner ends of chambers A and C. The pistons 78 and 86 being spring-loaded by springs 80 and 88, respectively, exert an initial constant predetermined first pressure P1 on the waterproof sealant 60 in chamber A and in chamber C, respectively, along with an additional variable ambient pressure P2 which enters through the PORTS 1 and 2 and which depends at any given moment upon the depth of the connector assembly 10 below the surface of the liquid in the well and depends upon the density (specific gravity) of this liquid in the well.
Consequently, the sealant 60 in communicating chambers A and B is subjected to the advantageous additive resultant of the variable ambient liquid pressure P2 plus the predetermined pressure P1.sub.80 produced by the axial thrust of the spring 80.
This pressure P.sub.A+B in chambers A and B can be expressed as:
Therefore, the sealant 60 in chambers A and B will be maintained at pressure P.sub.A&B which is always at the predetermined pressure difference P1.sub.80 above the variable ambient liquid pressure P2.
Similarly, the sealant 60 in communicating chambers C and D is subjected to the advantageous additive resultant of the variable ambient liquid pressure P2 plus the predetermined pressure P1.sub.88 produced by the axial thrust of the spring 88 (which may be the same as or different from the thrust of the spring 80). This pressure P.sub.C&D in chambers C and D can be expressed as:
Therefore, the sealant 60 in chambers C and D will be maintained at pressure P.sub.C&D which is always at the predetermined pressure difference P1.sub.88 above the variable ambient liquid pressure P2.
Since this fluid sealant 60 is always at a pressure level exceeding ambient pressure by a predetermined amount, this fluid sealant resists the leakage or seepage of ambient liquid into the fluid sealant chambers B and D which enclose the terminal connections 67, 69 and adjacent portions of the conductors 25 connected thereto. As the airgun 20 is lowered into a borehole and the ambient liquid pressure increases, the additional spring-loaded pressure P1 continues to act on the sealant 60 surrounding the connections and conductors, thus advantageously preventing external liquid or gases in the borehole liquid from entering into these connector areas.
In summary, the sealant 60 in chambers A and B is always sujected to a pressure greater, (for example in the range from 0.20 to 10 pounds per square inch greater) than ambient liquid because the force of the spring 80 is always added to the ambient pressure which is applied to the piston 78 through PORT 1. Similarly, the sealant in chambers C and D is always subjected to a pressure greater (for example, in the range from 5 to 80 pounds per square inch greater) than ambient liquid because the force of spring 88 is always added to the ambient pressure which is applied to the piston 86 through PORT 2.
The upper housing 12 is readily assembled to the intermediate housing 14 by machine screws 96 and their joint is sealed by O-rings (FIG. 8) described above. Similarly, the lower housing 16 is readily assembled to the intermediate housing 14 by machine screws 98, and their joint is sealed by O-rings 100 (FIGS. 7 and 8). The connector support 70 is sealed to the wall of chamber B by an O-ring 102 (FIG. 8). The connector support 70 and intermediate housing 14 are oriented with respect to each other by a locator pin 104 so that the respective conductors 25 are not inadvertently twisted during assembly of the whole cable connector 10.
The cable 24 is intended to suspend the entire weight of the airgun 20, the solenoid valve 22 and the cable connector 10. Thus, this cable, for example a "Logging Cable", contains at least one longitudinally extending stress-bearing member. For example, in this embodiment each of the seven conductors 25 is a multiple-strand flexible conductor. The exterior sheath 57 of the cable 24 comprises two layers of armor-like steel strands having opposite helical lay. It is the multiple steel strands in the sheath 57 which have suitable tensile strength for supporting the entire weight of the connector assembly, 10, airgun 20 and solenoid valve 22 plus the accumulated weight of hundreds or even thousands of feet of the cable 24 itself when suspended down in a borehole or well in the earth. Therefore, the cable clamp 26 itself is designed for providing a very strong grip on the cable 24 and a strong connection onto the upper end portion 31 of the upper housing 12 of the cable connector assembly 10. This connector assembly 10 may be used with other types of waterproof electrical cable 24.
Inviting attention back to the two pistons 78 and 86 (FIG. 7) and their respective springs 80 and 88, it will be noted that these pistons have relatively long cylindrical sleeve skirts 106 and 108, respectively, integral with their heads 78 and 86. The compression springs seat against the piston heads and are received within the hollow interiors of the piston skirts 106, 108. This telescoping arrangement of the compression springs within the piston skirts enables relatively long springs to be employed for providing relatively long piston travel in a compact space. The long piston travel maintains pressure on the fluid sealant 60 for continuing reliable operation even if the chamber A or C happens to become only partially filled with sealant, due to some inadvertent leakage of sealant out of the connector 10.
This connector assembly 10 may be used to advantage deep within any body of water, for example deep within an ocean, where high ambient liquid pressure exists.
Since other changes and modifications varied to fit particular operating requirements and enviroments will be apparent to those skilled in the art, the invention is not considered limited to the examples chosen for purposes of illustration, and includes all changes and modifications which do not constitute a departure from the true spirit and scope of this invention as claimed in the following claims and equivalents thereto.