WO2010016775A1 - Methodology for waterproofing primed seismic explosive assemblies - Google Patents

Abstract

A method of preparing an explosive assembly for seismic prospecting including the steps of preparing or providing a substantially tubular container (1) containing an explosive composition (5) that fills the container from one end and extends to an empty zone (9) adjacent the other end, inserting at least one detonator (6) into the explosive composition from the empty zone, and injecting a polymeric composition or sealant into the empty zone in such a manner that it polymerises to provide a matrix which substantially embeds at least part of the detonator and the wires (7) adjacent the detonator to at least substantially closes any liquid pathway to the detonator via the empty zone.

Description

"METHODOLOGY FOR WATERPROOFING PRIMED SEISMIC EXPLOSIVE

ASSEMBLIES"

TECHNICAL FIELD The present invention relates to methodology for waterproofing primed seismic explosive assemblies and related methodology.

BACKGROUND ART

Explosives are used as a sonic energy source for the purpose of seismic prospecting. For that purpose it is usual (A) to combine, in a pack, the explosive and the detonator, (B) to place it down the hole at a desired specified depth and (C) to await an appropriate time for firing when a Seismic recording team is available.

There are various types of Seismic explosives product offerings in the market depending upon the type of chemical formulation. They can be classified as cast molecular explosives (eg, Pentolite, TNT based), emulsion and Slurry explosives (AN based) and nitro-glycerine based dynamites.

Most of Seismic explosives products available in the market are packaged into screw able plastic canisters. The explosives are filled into the plastic canister which has some form of housing to accommodate the detonator(s). In case of Molecular based explosives (eg, PETN, TNT, RDX etc) the detonator tunnels are cast into the explosives to accommodate the detonator(s). The seismic system normally consists of various other components which may comprise of top cap, spiders, nose cones, speedy loader, end caps etc.

Examples of range of seismic explosive product offering can be seen at Dyno Nobel site at www.dynobel.com. Austin powder at www.austinpowder.com. and Orica at www.oricaminingservices.com.

Explosives charges are primed just prior to loading into the shot hole. It is illegal and unsafe to keep primed charge on the surface for any given time unless they are just prepared prior to loading straight into the shot hole.

Once the shot hole is loaded with the primed charges, normally the hole is temped with stemming material which can either be drill cuttings, different types of gravels, or bentonite etc.

For many operational reasons the primed shot holes may have to sleep over long period to time before they are fired. In some instances the sleep time may go from few weeks to many months and in such circumstances there is a significant risk of misfire of explosives particularly in the shot holes which are filled with water column. We propose, and have as an object, embedding at least part of each detonator and the wires to the detonator(s), preferably using part of a plugged casing assembly carrying the explosive as a mould, with a matrix which, immediately or soon thereafter will waterproof at least part of the detonator(s) and its interface with explosives. It is important in our view, not only to achieve appropriate waterproofing of the detonator and its interface, but also to avoid any heat generation which may result in temperature degradation which may cause explosion of the detonator. Temperature degradation can occur at temperatures as low at those experienced with fast set epoxy polymeric compositions (for example the T.P.60 Casting and Encapsulating Resin system of Adhesive Technologies Limited causes unwanted temperatures).

We propose embedding the detonator, and its interface with explosives, with settable material(s) (eg, a polymeric matrix) which is less exothermic than fast set epoxy systems yet nonetheless sets to a waterproof matrix. Ideally, we envisage the temperature of the set or polymerisation to be experienced by the detonator should be no higher than ambient temperature. It is therefore a further or alternative object of the present invention to provide, suitable for use in seismic prospecting, a primed seismic explosive assembly that waterproofs against water intrusion to the detonator and to its interface with explosives.

DISCLOSURE OF INVENTION The present invention is directed to assemblies, methods of preparation, use, etc of such prepared explosive assemblies.

The invention also is a method for priming explosives and assemblies of primed explosives for seismic prospecting reliant upon a compartmentalised housing and a polymeric sealant composition. In another aspect the invention is a method of preparing an explosive assembly useful for seismic prospecting, said method comprising or including the steps of preparing or otherwise providing a substantially tubular container (eg, a casing component) containing an explosive composition filling the container from, or from adjacent, one end and extending to an empty zone or a partial partition to an empty zone adjacent the odier end, inserting and/or associating at least one detonator into and/or with the explosive composition from said empty zone, and injecting a polymeric composition or sealant into the empty zone in such a manner that it polymerises or otherwise holds a form to provide a matrix which at least substantially embeds at least part of the detonator(s) and the wires thereto adjacent the detonator(s) thereby to at least substantially close any liquid pathway to the detonator(s) via said empty space. Preferably the polymeric composition or sealant, or both, cures and is not exothermic, or is of low exothermicity, during cure.

Preferably said empty zone is closed at or adjacent said other end.

Preferably the closure is by a fitting that plugs with said tubular container [eg, by a male or female inter-engagement (screw or bayonet or other)] or otherwise closes the end.

Preferably said insertion and/or associating of at least one detonator into and/or with the explosive composition involves placement of one or more detonator via a port in a partion or disc in the tubular casing component and/or into a passageway preformed in the explosive composition. Preferably said passageway aligns with an opening in a said partition of the container.

Preferably said insertion and/or association of the detonator(s) involves passing the wires of the detonator(s) out from the empty zone through a wall port of said tubular container.

Preferably the injection of the polymeric composition is into the empty zone of the tubular container when only after its end has been closed. Preferably the injection is reliant upon an injection port and a potential egress port, the latter preferably being used for the detonator wires and held back spue.

Preferably said potential egress port is protected by taping, a membrane or other. The egress port preferably is the only port from which wires of the detonator(s) pass.

In a further aspect the invention consists in a primed explosive assembly comprising or including a casing assembly, an explosive contained within said casing assembly, at least one detonator within said casing assembly in at least substantial contact with the explosive within said casing assembly, at least one wire or cord from the or each detonator passing out of said casing assembly, and a waterproofing matrix at least partly embedding the or each detonator and die wire(s) or cord(s) to the detonators within at least part of said casing assembly.

Preferably the waterproofing matrix was of low exothermicity or nonexothermic during partial (prior to downhole placement) or full cure (whether prior to or post downhole placement). Preferably said casing assembly includes a plug (screw, bayonet or otherwise) engaged to a tubular component or part of the casing assembly and said matrix, as a flowable unset composition, has been injected into the casing laterally thereof between said plug and said explosive within said casing.

Preferably a ported disc is transverse to the tubular axis within the tube and such port(s) receives or each receives, a detonator. Preferably at least two ports are provided into said casing body.

The present invention also consists in a primed explosive assembly resulting from a method of the present invention.

In yet a further aspect of the present invention consists in a single or pattern shot for seismic exploration that relies upon one or more primed explosive assemblies of the present invention.

And yet a further aspect of the present invention consists in a methodology or procedures substantially as herein described with or without reference to one or more of the accompanying drawings. And yet a further aspect the invention consists in assemblies or components suitable for assemblies substantially as herein described with reference to any one or more of the accompanying drawings.

And yet a further aspect the present invention consists in the use of polymeric or otherwise settable waterproofing compositions substantially as herein described for the purpose of waterproofing the detonator/wire interface in a primed explosive assembly.

And yet a further aspect the present invention consists in the use of polymeric compositions substantially as herein described for the purpose of waterproofing joints in wires (preferably to detonators of primed explosive assemblies substantially as herein described).

Preferably said polymeric material is associated with the joint of the wires in a confinement (eg, a junction box or the like).

Such jointing can be desirable to get through slower velocity upper layers down to faster velocity lower layers.

In yet a further aspect the present invention consists in any or all of the inventions herein described. As used herein "settable material" or "waterproofing matrix" or "polymeric material" includes widiin its ambit any suitable material diat sets (preferably below 70°C) (preferably to a waterproof elastic form) and/or which will set sufficiently, in less than two hours (preferably less than one hour) (most preferably less than 30 minutes), to enable its insertion downhole even below water yet which takes longer than 15 minutes to set completely and preferably much longer than two hours. A suitable material includes any of the following self curing polymeric systems: a high viscous, sag resistant adhesive based on a modified silane ("MS") polymeric system which cures to an elastic product eg, typified by Henkel TEROSTAT-MS 9399 which can be used alone or in conjunction with epoxy resin and curing agent. It can be mixed at 20°C to cure over 1 hour but be water insertable within minutes. This MS system sealant/etc, cures at temperatures not greatly in excess of 20°C with little or no exothermic behaviour. It has a Tensile Strength of 3MPa and a shear strength of 2MPa. Both are greater strength characteristics than the pressure even at 1200m depth in water. A polyure thane primer such as Henkel's TEROSTAT 8517H may be used to improve/promote adhesion of an MS or other compatible sealant matrix to the surfaces to be denied, as water pathways to the detonators, ie, the filling sealant matrix keys to the surface adhesive. TEROSTAT 8517H is a solvent based system of Methyl ethyl ketone, Ethyl acetate, Hexane, 1 ,6-diisocyanato-, homopolymer, and Henkel proprietary additives. any injectable compound or composition [eg, as disclosed in http: / /faculty.uscupstate.edu/Uever/Polymer%20 Resources/Classification.htm#thermoplastics or http://www.polymerexpert.bi2/PolymersandComposites.html] which exhibits an ability to fill and to keep filled the empty zone while providing a waterproof characteristic to protect the detonator(s) and does not generate temperatures above 70°C. Preferably it is a self curing component or mix of components able to provide the desired outcome, whether with or without fillers. Any appropriate sealant system of a waterproof matrix forming type can be used. As used herein "detonator" preferably refers to Seismic electric and/or seismic electronic detonators such as can be sourced from, for example, Davey Bickford/Nitro Bickford, France, Dyno Nobel, USA. Maxam, Spain Orica Mining Sendees. Likewise the "dBX Geoprime main" casing component of a container or casing assembly as herein described. As used herein the term "and/or" means "and" or "or", or both. As used herein the term "(s)" following a noun includes, as might be appropriate, the singular or plural forms of that noun.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art. BRIEF DESCRIPTION OF DRAWINGS

A preferred form of the present invention will now be described with reference to accompanying drawings in which

Figure 1 shows the three main components of the pat, there being a main tubular casing with an internal partitioning member through which one or more detonator can be placed and from which detonator wires can be emergent, a pointed bottom cap and a enclosing top cap, Figures 2A through 2N show a procedure in accordance with the present invention whereby it is possible to prime die explosive and then almost immediately place the explosive down a bore hole, and Figure 3 shows a cross section of a typical (generic) assembly of Figures 2A to 2N.

In a preferred form of the present invention, plastic components are coupled together to provide the assembly as shown in Figure 3.

This comprises a main plastics tube 1 as the casing. It includes an apertured disc 2 to sit on or over the explosive composition 5. The casing tube 1 includes a female direaded region at its top end and a male threaded region at its lower end respectively to receive the male thread of a top cap 3 and the female thread of a bottom cap 4. The top cap 3 or bottom cap or end cover can locate or include wings or other disposable members adapted to allow dropping of die assembly down a bore hole that reduce its likelihood to rise under die hydrostatic pressure of intruding water prior to the borehole being optionally backfilled. Shown in Figure 3 is the cast or otherwise fill of a suitable explosives mixture 5. Moulded blind passages of the cast explosive locate the two Seismic specs detonators 6 (ie, Positioned via the ports of disc 2).

The wires 7 of the electrical detonators emerge from die casing 3 via a taped over port 8 and die empty zone 9 is filled in totality so as to embed die top of the detonators 6 with a suitable waterproofing settable material or polymeric material as a matrix diat has been inserted via the injection port 10, through which die wires do not pass, diereby to deny a water pathway via eidier of ports 8 and 10 to the detonators. The port 8 can be used widi taping (after wire passage) to act to resist spue.

The sequence of such arrangement will now be described by reference to Figures 2A through to Figures 2N common references for lie or similar components to the embodiment of Figure 3 are used in Figures 1 to 2N.

Figure 2A shows post assembly, a typical dBX explosive charge in the tubular casing of Dyno Nobel but capped at each end in our standard manner, the detonator wire 7 protruding from the side entry port 8 in the casing tube 1. Figute 2B shows, once inserted into the casing, the folding back of the detonator 6 onto itself and its reinsertion into the casing.

Figure 2C shows the detonator 6 being inserted through the aperture disc 2 into either of the internal detonator blind passages. These passages are housed inside the main explosive component of the product (dBX).

Figure 2D shows the detonator 6 fully inserted and ready to be sealed.

Figure 2E shows the end or top cap 3 being screwed into place.

Figure 2F shows assembly to its final form.

Figure 2G shows a half hitch in the detonator wire around the base of the main assembly. This will alleviate pressure at the wire/detonator interface.

Figure 2H shows adhesive tape 11 taping of the wires half hitched in two places to the casing.

Figure 21 shows preparation of a settable material (eg, "Terostat" compound) using a twin port caulking gun and ribbon blender nozzle. Figure 2J shows port 10 into the tubular casing body (1 opposite the side entry port 8) being used for the injection.

The injection nozzle is then inserted into this port 10 as in Figure 2K and the ("Terostat") composition is injected. The injection allows the tacky compound to flow into the empty zone to be filled and there it selfcures to a resilient waterproof matrix 9. Figure 2L shows the main entry port 8 showing, as a spue, the composition. The port 8 should be blocked with finger and additional compound will flow fully to fill the empty zone to and into the threaded region of the plug cap and completely seal the cavity.

As shown by Figures 2M and 2N, both the rear injection port 10 and the main port 8 are sealed widi the settable matrix. The entire internal cavity is filled with the matrix and completely covering the internal detonator ports in the disc 2 and to the explosive 5, the detonators 6 and wire 7 at their zone near the detonators.

Depending on ambient temperatures preferably the settable composition will begin to go off within 10-15 minutes of injection. It will be several hours before the product is completely set, although this will continue to happen while submerged in water. It is sufficiently protection, as it selfcures, for the detonator and wires.

Claims

CLAIMS:

1. A method of preparing an explosive assembly useful for seismic prospecting, said method comprising or including the steps of preparing or otherwise providing a substantially tubular container (eg, a casing component) containing an explosive composition that fills the container from, or from adjacent, one end, and extends to an empty zone, or a partial partition to an empty zone, adjacent the other end, inserting and/or associating at least one detonator into and/or with die explosive composition from said empty zone, and injecting a polymeric composition or sealant into die empty zone in such a manner that it polymerises or otherwise holds a form to provide a matrix which at least substantially embeds at least part of the detonator(s) and the wires diereto adjacent the detonator(s) thereby to at least substantially close any liquid pathway to the detonator(s) via said empty space.

2. A method of claim 1 wherein the polymeric composition or sealant, or both, cures and is not exothermic, or is of low exothermicity, during cure.

3. A method of claim 1 or 2 wherein said empty zone is closed at or adjacent said other end.

4. A method of claim 3 wherein said empty zone is closed at said odier end by a closure fitting.

5. A method of any one of the preceding claims wherein said insertion and/or associating of at least one detonator into and/or with the explosive composition involves placement of one or more detonator via a port in a partition or disc in the tubular casing component and/or into a passageway preformed in the explosive composition.

6. A method of claim 5 wherein a said passageway aligns with an opening in a said partition of the container.

7. A method of any one of the preceding claims wherein said insertion and/or association of the detonator(s) involves passing the wires of the detonator(s) out from the empty zone through a wall port of said tubular container.

8. A method of any one of the preceding claims wherein the injection of the polymeric composition or sealant is into the empty zone of the tubular container after its said other end has been closed.

9. A method of claim 8 wherein the injection is reliant upon an injection port.

10. A method of claim 9 wherein said potential egress port is protected by taping, a membrane or other.

11. A method of claim 9 or 10 wherein the egress port preferably is the only port from which wires of the detonator(s) pass.

12. A primed explosive assembly comprising or including a casing assembly, an explosive contained within said casing assembly, at least one detonator within said casing assembly in at least substantial contact with the explosive within said casing assembly, at least one wire or cord from the or each detonator passing out of said casing assembly, and a waterproofing matrix at least partly embedding the or each detonator and the wire(s) or cord(s) to the detonators within at least part of said casing assembly.

13. An assembly of claim 12 wherein the waterproofing matrix was of low exothermicity or nonexothermic during partial (prior to downhole placement) or full cure (whether prior to or post downhole placement).

14. An assembly of claim 12 or 13 wherein said casing assembly includes a plug (screw, bayonet or otherwise) engaged to a tubular component or part of the casing assembly and said matrix, as a flowable unset composition, has been injected into the casing laterally thereof between said plug and said explosive within said casing.

15. An assembly of any one of claims 12 to 14 wherein a ported disc is transverse to the tubular axis within the tube and such port(s) receives or each receives, a detonator.

16. An assembly of claim 15 wherein at least two ports are provided into said casing body.

17. A primed explosive assembly resulting from a method of any one of claims 1 to 11.

18. A single or pattern shot for seismic exploration that relies upon one or more primed explosive assemblies of any one of claims 12 to 16.

19. A methodology or procedures substantially as herein described with or without reference to one or more of the accompanying drawings.

20. Assemblies or components suitable for assemblies substantially as herein described with reference to any one or more of the accompanying drawings.

21. Use of polymeric or otherwise settable waterproofing compositions substantially as herein described for the purpose of waterproofing the detonator /wire interface in a primed explosive assembly.

22. Use of polymeric compositions substantially as herein described for the purpose of waterproofing joints in wires to detonators of primed explosive assemblies substantially as herein described.

23. The use of claim 22 wherein said polymeric material is associated with the joint of the wires in a confinement (eg, a junction box or the like).

24. The use of claim 23 wherein the joining is to get through slower velocity upper layers down to faster velocity lower layers.