WO2012150906A1

WO2012150906A1 - Thermo-pulse generator

Info

Publication number: WO2012150906A1
Application number: PCT/SG2011/000170
Authority: WO
Inventors: Vasily Petrovich KOBIAKOV; Ivan Nikitovich GARANZHA; Vladimir Grigorevich MELNIK
Original assignee: Rusinko Pte Ltd
Priority date: 2011-05-03
Filing date: 2011-05-03
Publication date: 2012-11-08
Also published as: MX2012015029A

Abstract

[0040] The present invention describes a thermo-pulse heat generator (100) for increasing permeability of bottomhole rock formation of oil wells and for increasing oil well output. The thermo-pulse heat generator (100) includes a body tube (110, 110a, 110b, 110c), filled with blocks (105) of a heat-evolving composition, is joined to a heat exchanger assembly (180, 180a) at a bottom end and a head-adapter assembly (140) at a top end of the body tube (110, 110a), etc. The heat exchanger assembly (180, 180a) increases heat transfer from molten products of combustion of the heat-evolving blocks (105) to the well fluid yet acting as a trap to minimise the molten metals in the products of combustion from being released into the well casing (10).

Description

THERMO-PULSE GENERATOR

Field of the Invention

[001] The present invention relates to oil production industry, in particular, to a thermo- pulse heat generator for stimulating the production of oil wells by treating the bottomhole rock formation.

Background [002] Oil wells that have been supplying oil for many years often experience reduction in oil extraction as the oil wells age. This is particularly encountered in the fields with increased viscosity oil, which contains increased amount of contamination such as paraffin, resin, etc. When oil well production is reduced, the bottomhole zone is treated to improve permeability of the surround rock formation. Known methods for stimulating the production of oil wells are shock treatments using explosives, acid treatment, hydraulic fracturing and high energy gas fracturing. Description of these known stimulating methods are given in the background of US Patent No. 6,732,799, assigned to Challacombe.

[003] High energy gas fracturing is a recent technology employed in fracturing oil-bearing rock formation around a well's bottomhole without the problems inherent in explosive and acid treatments. Russian Patent No. 2138630, assigned to Silen Company Ltd, describes a sealed metal enclosure having an air chamber and a fuel chamber. The air and fuel chambers are separated by a membrane. The fuel material comprises a first part containing at least an iron-aluminium thermite, a second part containing at least ammonium nitrate and a third part containing components of the first and second parts. The fuel material according to this patent does not produce molten products of combustion and thus there is insufficient thermal power for the treatment of oil wells. In addition, combustion of this fuel material generates a gas phase, which prevents beneficial phenomenon of implosion of well fluids.

[004] In another approach, Russian Patent No. 2295637, assigned to the Institute of Structural Makrokinetics and Materials Science, describes a solid-flame heat generator for treating bottomhole zone of oil wells. This heat generator is contained in a sealed enclosure made from a metal pipe. The sealed enclosure contains a stack of pressed fuel blocks. At either end of the fuel blocks, there is an igniter and an electrode assembly. The electrode assembly has an electric discharge gap for initiating combustion of the fuel blocks. Near both ends of the fuel block stack, the enclosure has at least two weakened local areas in the form of dead-end (or blind pits) or in the form of cross-windows with sealed membrane plugs. The bottom end of the enclosure is packed with a heat insulator whilst the top end of the enclosure has an internal thread for connection with a cable connector. The space below the threaded end at the top end is also packed with a heat insulator. The fuel blocks are made of high-energy thermite mixtures containing one or more oxidants in the form of solid metal oxides and one or more metal-reducing agents. These fuel blocks combust in an adiabatic temperature of 2500-3000 deg. C without emitting any gas phase and produce about 3-4 MJ/kg of heat when the rate of combustion is about 1 to about 2 m/s. Combustion of the fuel blocks generates a sharp rise in temperature and pressure inside the sealed enclosure. The outside surface temperature of the sealed enclosure reduces to about 420 deg. C from about 2500-3000 deg. C inside the enclosure, due to heat loss to the surrounding well fluid. This temperature is enough to start boiling of the well fluid on the outside surface of the enclosure. [005] At the same time, the high pressure and temperature inside the enclosure burst the weakened pits or windows thereby causing the products of combustion to disperse into the well fluid. The resulting hydraulic and thermal shocks in the well fluid increase permeability of the rock formation surrounding the bottomhole. [006] Combustion of the fuel blocks according to RU 2295637 produces molten combustion products and the thermal power generated is thus veiy powerful. However, these molten combustion products are released through the ruptured pits or windows of the enclosure into the gap between the walls of the enclosure and well casing. As a result, the molten combustion products containing molten metals become welded to the walls of the enclosure and well casing. This causes problems for subsequent normal operation of the oil wells. [007] It can thus be seen that there exists a need for another type of high-energy heat generator that can provide efficient transfer of heat to the well fluid and yet overcoming problems of the prior art.

Summary

[008] The following presents a simplified summary to provide a basic understanding of the present invention. This summary is not an extensive overview of the invention, and is not intended to identify key features of the invention. Rather, it is to present some of the inventive concepts of this invention in a generalised form as a prelude to the detailed description that is to follow.

[009] The present invention describes a thermo-pulse heat generator for increasing permeability of oil-bearing rock formation. The thermo-pulse heat generator is used to produce intense heat pulses to radiate from the thermo-pulse heat generator. Intense boiling of the well fluid results in pressure pulses radiating from the thermo-pulse heat generator which then cause thermo-hydraulic fracturing of the oil-bearing rock formation and unclogging of pores/cracks in the perforation interval of the well casing. At the same time, there is also a complex interplay of beneficial cavitation and hydraulic implosion.

[0010] In one embodiment, the present invention provides a thermo-pulse heat generator comprising: a body tube, wherein its internal cavity is substantially stacked with blocks of a compacted heat-evolving composition; a head-adapter assembly operable to connect with an upper end of the body tube; and a heat exchanger assembly operable to connect with a lower end of the body tube; wherein the head-adapter assembly comprises an electrode assembly operable to produce a spark-arc discharge to initiate combustion of the blocks of compacted heat-evolving composition. [0011] In one embodiment, the body tube comprises a membrane disposed near a bottom end of the body tube to form a sealed chamber for combustion of the heat-evolving blocks. The membrane may be welded with the body tube or formed integrally or unitarily on a cap member, which is located in the body tube. [0012] In another embodiment, the heat exchanger assembly comprises two or more co- axially disposed cylinders. The bottom end of the two or more co-axially disposed cylinders is closed by a bottom plug and the walls of co-axial cylinders comprise slots. The slots may be longitudinal to or at an angle to the respective axis of the co-axial cylinder.

[0013] In another embodiment, walls of the co-axially disposed cylinders comprise rows of holes, which may be longitudinal to or at an angle to the respective axis of the co-axial cylinder. Preferably, the slots or rows of holes on separate two or more co-axially disposed cylinders are azimuthally displaced in relation to each other.

[0014] In another embodiment, the heat exchanger comprises a perforated insert disposed at an upper end of the heat exchanger. Preferably, the perforated insert has perforations formed in an area within the inside diameter of the inner and/or innermost cylinders.

[0015] In yet another embodiment, the head-adapter assembly has a hollow stem. The hollow stem has a stepped cavity and a fluoroplastic insert with a centre hole is disposed in the stepped cavity. Preferably, a sealing screw is threadedly disposed in the stepped cavity, wherein operation of the sealing screw into the stepped cavity squeezes the fluoroplastic insert to form a seal both around an electric wire going therethrough to the electrode assembly and in the stepped cavity.

Brief Descri ption of the Drawings

[0016] This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

[0017] FIG. 1 illustrates a thermo-pulse heat generator according to an embodiment of the present invention;

[0018] FIG. 2A illustrates a sectional view of a body of the thermo-pulse heat generator shown in FIG. I according to another embodiment of the present invention; FIG. 2B illustrates a sectional view of a lower part of a body of the thermo-pulse heat generator shown in FIG. 1 according to another embodiment of the present invention; FIG. 2C illustrates a sectional view of a lower part of a body of the thermo-pulse heat generator shown in FIG. 1 according to another embodiment of the present invention; FIG. 2D illustrates a sectional view of a lower part of a body of the thermo-pulse heat generator shown in FIG. 1 according to another embodiment of the present invention;

[0019] FIG. 3A illustrates a sectional view of a heat exchanger assembly of the thermo- pulse heat generator shown in FIG. 1 according to another embodiment of the present invention; FIG. 3B illustrates angular orientation of coaxial tubes of the heat exchanger shown in FIG. 3A;

FIG. 3C illustrates a sectional view of a heat exchanger assembly according to another embodiment of the present invention. [0020] FIG. 4 illustrates a sectional view of a head-adapter assembly of the thermo-pulse heat generator shown in FIG. 1 according to another embodiment of the present invention; and

[0021] FIG. 5 illustrates an installation of the thermo-pulse heat generator shown in FIG. 1 according to yet another embodiment of the present invention.

Detailed Description [0022] One or more specific and alternative embodiments of the present invention will now be described with reference to the attached drawings. It shall be apparent to one skilled in the art, however, that this invention may be practised without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals or series of numerals will be used throughout the figures when referring to the same or similar features common to the figures. [0023] FIG. 1 shows a thermo-pulse heat generator 100 according to an embodiment of the present invention. As shown in FIG. 1, the thermo-pulse heat generator 100 comprises a body 1 10, a head-adapter assembly 140 connected to an upper end of the body and a heat exchanger assembly 180 connected to a lower end of the body 1 10. The body 1 10 is made from a hollow metal pipe. In one embodiment, the body pipe 1 10 is made of steel, with an outside diameter of about 51 mm, an inside diameter of about 43 mm and a length of about 2000 mm; in another embodiment, the steel body pipe 1 10 has an outside diameter of about 95 mm, an inside diameter of about 85 mm and a length of about 2000 mm. In another embodiment, the body pipe 1 10 is made of aluminium.

[0024] FIG. 2A shows a sectional view of the body 110 of the above thermo-pulse heat generator 100 according to an embodiment of the present invention. As shown in FIG. 2A, near the lower end of the body 1 10, there is disposed a membrane 1 12 in the hollow cavity of the body 1 10. The membrane 1 12 is made of a metal and it separates the hollow cavity of the body into two chambers, an upper chamber 1 14a above the membrane 1 12 (as seen in FIG. 2A) and a lower chamber 1 14b below the membrane 1 12. The lower chamber 1 14b is defined by a sleeve 120. The membrane 1 12 is a thin circular disk, with a thickness of about 3% of its outside diameter. Preferably, the membrane 1 12 has annular collars 1 13 on one or both face surface(s). As shown in FIG. 2 A, the body pipe 1 10 and the sleeve 120 are welded together with the membrane 1 12 being located therebetween. The annular collars 1 13 help one to align the body pipe 1 10, the membrane 1 12 and the sleeve 120 together during welding. As can be seen from FIG. 2A, the free end of the sleeve 120 has an external stepped end 122, which is threaded. The threaded end 122 is provided for connection with an internal thread 189 on the heat exchanger 1 80 (as seen in FIG. 3A or 3C). The upper end of the body tube 1 10 has an internal thread 1 19 which is dimensioned to fit with a thread 146 on the head-adapter assembly 140 (shown in FIG. 4). When assembled with the head-adapter assembly 140, the upper chamber above the membrane 1 12 becomes a sealed or airtight chamber 1 14a. [0025] As shown in FIG. 2A, the upper chamber 1 14a above the membrane is stacked with blocks 105 of a heat-evolving composition. The heat-evolving composition is a powder mixture of one or more oxidants in the form of metal oxides and one or more of reducing agents (which include metals and/or non-metals). Each block 105 of the heat-evolving composition is compacted into a cylindrical block. For eg., with a body tube of 43 mm inside diameter, each block 105 is about 42 mm diameter, about 40 mm long and weighs about 120 g, so that a body tube of 2m length contains 50 blocks or a load of about 6 kg of the heat-evolving composition. The heat-evolving composition has an average specific heat of about 4.5 MJ/kg. In use, a load of 6 kg of the heat-evolving composition produces about 27 MJ of heat energy and the entire stack of the blocks 105 burns inside the sealed chamber 1 14a for an average duration of about 4.5 s, thereby producing about 6MW of heat power. [0026] FIG. 2B shows a sectional view of a lower part of a body 1 10a according to another embodiment of the present invention. As shown in FIG. 2B, a membrane 1 12a is disposed in the hollow cavity of the body pipe 1 10a near the pipe's lower end. In contrast with the above embodiment, the membrane 1 12a is formed integrally with a cap member 130. The outside cylindrical surface of the cap member 130 has one or more grooves 132. Each groove 132 is shaped and dimensioned to receive a seal 133, such as an "O" ring, lip or packing seal. The lower end of the body pipe 1 10 has two internal steps, 1 16, 1 17. The outer step 1 16 has a bigger diameter and is threaded. When assembled, the cap element 130 is located within the step 1 17 whilst a threaded sleeve 120a is fitted in the threaded step 1 16. As seen in FIG. 2B, the threaded sleeve 120a is longer than the threaded step 1 16 so that the threaded sleeve 120a extends out 122 for connection with the heat exchanger 180, like in the above embodiment.

[0027] FIG. 2C shows a sectional view of a lower part of a body 1 10b of the above thermo- pulse heat generator 100 according to another embodiment of the present invention. The body 1 1 Ob is similar to that of the body 1 10 (shown in FIG. 2A) except that it has a sleeve 120b, which is longer in length than sleeve 120 and there are a number of radial holes 124 in the sleeve 120b.

[0028] FIG. 2D shows a sectional view of a lower part of a body ] 10c of the above thermo- pulse heat generator 100 according to another embodiment of the present invention. The body 1 10c is similar to that of the body 1 10a (shown in FIG. 2B) except that it has a sleeve 120c, which is longer in length than sleeve 120a and there are a number of radial holes 124 in the sleeve 120c.

[0029] FIG. 3A shows a sectional view of the heat exchanger assembly 1 80 of the above thermo-pulse heat generator 100 according to another embodiment of the present invention. As shown in FIG. 3A, the heat exchanger assembly 180 comprises two co-axial cylinders 182, 184. As seen from FIG. 3A, the inner cylinder 184 is relatively shorter than the outer cylinder 182. The lower ends of the cylinder 182,184 are closed by a bottom plug 186. The bottom plug 186 has two steps 187, 188, which are threaded for respective connections with mating ends of the cylinders 182, 184. The wall of each cylinder 182, 184 has a plurality of spaced apart longitudinal slots 183,185. Preferably, the slots 183, 185 on the two co-axial cylinders 182, 184 are substantially the same length. As seen in FIG. 3A, the slots 183, 185 are closer to the top, ie. LI is longer than L2. Preferably, the slots 183, 185 on the cylinders 182, 184 are of the same numbers, so that when they are assembled with the bottom plug 186, the slots 1 83, 185 on the cylinders are azimuthally displaced relative to each other, as shown in FIG. 3B. The upper end of the outer cylinder 182 has the internal thread 189. The internal thread 189 is operable to engage with the threaded end 122 of the above sleeve 120, 120a, 120b, 120c. [0030] In the above embodiment of the heat exchanger assembly 180, only two co-axial cylinders 182, 1 84 are shown for illustration. As the outer diameter of the outer cylinder 182 is preferably and substantially the same diameter as the body tube 1 10, the amount of heat of combustion of the heat-evolving blocks 105 and volumes of products of combustion determine the number of co-axial cylinders 182,184 and their lengths. The amount of heat of combustion and volumes of products of combustion also determine the number of slots 1 83, 185 on the cylinders 182,184, their sizes and lengths. To ensure strength and rigidity of the cylinders 1 82, 184, each of the slots 183, 1 85 may be implemented in staggered sections or segments, as shown in FIG. 3C, instead of a single long slot.

[0031] In another embodiment, a heat exchanger assembly 180a comprises a perforated insert 1 90. As shown in FIG. 3C, the heat exchanger 1 80a is similar to the heat exchanger 180 except that the perforated insert 190 fits within the inside diameter of the outer cylinder 182 and is disposed between the top end of the inner cylinder 184 and the threaded end 189. Perforations 192 on the insert 190 are longitudinal but are formed within an area defined by the inside diameter of the inner cylinder 184. The amount of heat of combustion and the volumes of products of combustion also determine the numbers and sizes of the perforations 192.

[0032] On the above cylinders 182, 184, the slots 183, 185 are shown to be longitudinal along the axes of the cylinders. In another embodiment, it is possible that the slots 183, 185 are formed at an angle to the axis of the respective cylinder. Preferably, the number and the angle of the slots on the inner and outer cylinders are the same and when assembled together with the bottom plug 186, the slots 183, 185 are azimuthally displaced as shown in FIG. 3B. In yet another possible embodiment (not shown in the figures), instead of forming slots, linear rows of holes or rows of holes in a checkerboard pattern are formed on the cylinders 182, 184. The rows of holes are aligned parallel to or at an angle to the axis of the respective cylinder 182, 184. Again, the holes on the inner and outer cylinders 1 82, 184 are azimuthally displaced as shown in FIG. 3B.

[0033] FIG. 4 shows a sectional view of the head-adapter assembly 140 of the above thermo-pulse heat generator 100 according to another embodiment of the present invention. As shown in FIG. 4, the head-adapter assembly 140 comprises generally a hollow bell- shaped shell 142 and a hollow stem 144. The free upper end of the stem 144 has an internal thread 145 and an electric connector 150 is threadedly engaged with the internal thread 145. The hollow centre of the stem 144 is an elongate but stepped cavity 152. A lower part 153 of the stepped cavity 152 is relatively larger and it opens into an interior cavity 141 of the bell-shaped shell 142. Disposed inside the lower stepped cavity 153 is a sealing bush 154. The sealing bush 154 is made of a fluoroplastic material, such as teflon. Both the sealing bush 1 54 and the electric connector 150 each has a centre hole that is dimensioned to receive an electric wire 156 to an electrode assembly 170. As shown in FIG. 4, a lower end of the stepped cavity 153 is threaded and a sealing screw 158 is threadedly engaged therein. The sealing screw 158 also has a centre hole to receive the electric wire 1 56. To seal the step cavity 153, the sealing screw 158 is turned threadedly into the stepped cavity 153 to compress the sealing bush 154. The sealing bush 154 being relatively soft and compliant becomes squeezed radially and longitudinally inside the cavity 153, thereby forming a seal both around the electric wire 156 and in the step cavity 153. [0034] Also as shown in FIG. 4, a generally hat-shaped element 160 is disposed in the interior cavity 141 of the bell-shaped shell 142, with a brim 162 of the hat-shaped element 160 being substantially smaller than an outside diameter of the bell-shaped shell 142. An interior of the hat-shaped element 160 is packed with a heat insulator 164. The heat insulator 164 provides a barrier to the spread of heat from combustion of the heat-evolving blocks 105. On the outside surface, near the mouth of the bell-shaped shell 142, the bell- shaped shell 142 is threaded 146. The threaded end 146 is dimensioned to fit with the thread end 1 19 at the upper end of the bbdy tube 110, 110a, 110b, 110c so that, when assembled, the brim 162 of the hat-shaped element 160 is clamped between the bell-shaped shell 142 and the body tube 110, 1 10a, etc. Near the threaded end 146, there are a number of grooves 147 on the outside surface of the bell-shpaed shell 142. Each of the groove 147 is shaped and dimensioned to receive an "O" ring seal. Further up on the external surface of the stem 144, there is another set of threads 148 and "O' ring grooves 149. As will be appreciated later, an armoured logging cable 530 as seen in FIG. 5 is terminated with a cable socket 540. The cable socket 540 is connected to the head-adapter assembly 140 via the threads 148. "O" ring seals disposed in grooves 147 and 149 prevent fluid ingress into . the interface between the head-adapter assembly and the cable socket 540. In use, a logging truck 510 with a winch 520 (see FIG. 5) uses the armoured cable 530 to lower the thermo- pulse heat generator 100 into a well casing 10 of an oil well so that the thermo-pulse heat generator 100 is suspended in the perforation interval 20 of the well casing.

[0035] Referring back to FIG. 4, the electric wire 156 extends through the hat-shaped element 160 and insulation 164, and terminates at the electrode assembly 170. The other end of the electrode assembly 170, that is, after the spark-arc gap, is grounded to the head- adapter assembly 140 and an electric path is completed at a spark-arc generator 560 (see FIG. 5). In another embodiment, the electric path from the head-adapter assembly 140 to the spark-arc generator 560 is completed by going through a pin in the electric connector 1 50 and one or more electric wires inside the armoured cable 530. [0036] FIG. 5 shows an installation of the thermo-pulse heat generator 100 according to an embodiment of the present invention. As shown in FIG. 5, the thermo-pulse heat generator 100 is lowered on the armoured logging cable 530 into the well and is suspended at a perforation interval 20. An electric pulse from the spark-arc generator 560 on the logging truck 510 is sent via the armoured logging cable 530 to the electrode assembly 170 where an electric arc discharge is generated to initiate combustion of the heat-evolving blocks 105. Once combustion of the blocks 105 is initiated, a combustion front exceeding 3000 deg. C propagates from the top to the bottom of the stack of heat-evolving blocks 105 at a speed of about 1 m/s and releases an enormous amount of exothermic energy. Due to intensive heat transfer to the well fluid surrounding the thermo-pulse heat generator 100, the temperature on the external wall of the body tube 1 10 reduces to a range from about 600 deg. C to about 700 deg. C (depending on the down-hole pressure). This temperature in the downhole pressure is sufficient for the heated surface of the thermo-pulse heat generator 100 to cause the well fluid to boil.

[0037] When the combustion wave front reaches the bottom of the stack of the blocks 105, the membrane 1 12 becomes melted and the molten products of combustion (including metals and slags) fall down into the heat exchanger assembly 180. The slags, such as oxide products which are less dense than the molten metals, may flow out of the hole 124 in the sleeve 120b, 120c. When the perforated insert 190 is used, the perforations 192 cause the molten products of combustion to flow in jets into the heat exchanger assembly 180, thereby increasing contact area of the molten products of combustion with the well fluid. With the present invention, the heat exchanger assembly 1 80 provides direct contact of the molten products of combustion with the well fluid and allows an enormous amount of heat power to be transferred to the well fluid, as compared to those heat generators mentioned in the background section. Direct contact of molten products of combustion with the well fluid results in intense superheating of the well fluid, formation of vapour-water mixture and intense turbulent flows in the well-bore fluid. The resultant pressure pulses spread radially from the heat generator 100. The well fluid is prevented from moving to the bottom of the well and fluid flow to the top is restricted by a preventer 550 at the well head. The water-vapour pressure pulses then penetrate through the perforations 20 in the well casing 10 and the intense heat melts the wax-tar deposits that clogged cracks and pores in the surrounding rock formation. As the superheated well fluid loses its temperature, the water vapours collapse and result in the phenomenon of cavitation. Cavitation causes mechanical impact, which not only cleans the clogged pores and cracks in the surrounding rock formation but also expands the channels for oil to flow. Following the cooling and cavitation of the superheated well fluid, the well fluid rushes back to fill the cavity of the burned out thermo-pulse heat generator 100 thereby resulting in implosion of the well fluid. Implosion is thought to be beneficial in removing the wax-tar deposits that may be present in the cracks and pores of the oil-bearing rocks. As is appreciated, the present invention therefore provides a thermo-pulse heat generator 100 that is operable to produce a concentrated heat power source to an oil well bottomhole zone. In use, the concentrated heat power source produces intense heat pulses that spread radially and longitudinally along the thermo-pulse heat generator 100. Intense boiling of the well fluid causes pressure pulses to radiate from the thermo-pulse heat generator. The radiating intense heat and pressure pulses result in thermo-hydraulic fracturing of the surrounding oil bearing rock formation and unclogging of the pores and cracks. At the same time, there is also a complex interplay of beneficial cavitation and hydraulic implosion. The thermo- pulse heat generators 100 according to the present invention have been tested with very positive results.

[0038] Besides increasing heat transfer to the well fluid, the heat exchanger 180, 1 80a also serves as a trap for molten metals present in the molten products of combustion of the heat- evolving blocks 105. The molten metals cool down and form ingots, which collect at the bottom of the heat exchanger 1 80, 1 80a and are easily removed for disposal.

[0039] While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the invention. The scope of the present invention is now defined in the claims and as supported by the description and drawings:

Claims

CLAIMS:

1. A thermo-pulse heat generator comprising:

a body tube, wherein its internal cavity is substantially stacked with blocks of a compacted heat-evolving composition;

a head-adapter assembly operable to connect with an upper end of said body tube; and

a heat exchanger assembly operable to connect with a lower end of said body tube; wherein said head-adapter assembly comprises an electrode assembly operable to produce a spark-arc discharge to initiate combustion of said blocks of compacted heat- evolving composition.

2. A device according to claim 1, wherein said body tube comprises a membrane disposed near a bottom end of said body tube to form a sealed chamber for combustion of said heat-evolving blocks.

3. A device according to claim 1 or 2, wherein said membrane is welded with said body tube.

4. A device according to claim 1 or 2, wherein said membrane is integrally or unitarily formed on a cap member, which is located in said body tube.

5. A device according to claim 3 or 4, wherein said body tube below said membrane has a plurality of radial holes.

6. A device according to any one of the preceding claims, wherein said heat exchanger assembly comprises two or more co-axially disposed cylinders.

7. A device according to claim 6, wherein a bottom end of said two or more co-axially disposed cylinders is closed by a bottom plug.

8. A device according to claim 7, wherein walls of said two or more co-axially disposed cylinders comprise slots.

9. A device according to claim 7, wherein said slots are longitudinal to or at an angle to respective axis of said two or more co-axially disposed cylinders.

10. A device according to claim 8 or 9, wherein each of said slot is staggered into two or more segments.

1 1. A device according to claim 7, wherein walls of said two or more co-axially disposed cylinders comprise rows of holes.

12. A device according to any one of claims 8-1 1, wherein said slots or rows of holes on separate said two or more co-axially disposed cylinders are azimuthally displaced in relation to each other.

13. A device according to any one of the preceding claims, wherein said heat exchanger comprises a perforated insert disposed at an upper end of said heat exchanger.

14. A device according to claim 13, wherein said perforated insert has perforations formed in an area within inside diameter of an inner and/or innermost cylinder(s) of said two or more co-axially disposed cylinders.

15. A device according to any one of the preceding claims, wherein said head-adapter assembly has a hollow stem, with said hollow stem having a stepped cavity and a fluoroplastic insert with a centre hole is disposed in said stepped cavity so that said fluoroplastic insert is operable to be squeezed to form a seal both around an electric wire going therethrough to said electrode assembly and in said stepped cavity.

16. A device according to claim 1 5, further comprising a sealing screw being threadedly disposed in said stepped cavity, wherein operation of said searing screw into said stepped cavity squeezes said fluoroplastic insert to form said seal.