CN1049037C - Low resistance electrical heater - Google Patents

Abstract

A subterranean electrical heater comprising an electrical heating cable (9, 10) arranged in a partly cased well borehole (1) having a heating core comprising about 6 percent by weight of nickel and about 94 percent by weight of copper, a mineral insulation surrounding the heating core, a sheath surrounding the mineral insulation, cement (23) securing the heating cable (9, 10) in the well borehole (1) in the formation zone (22) to be heated; and a means (1, 2) to supply electrical power through the heating cable (9, 10).

Description

Low resistance electrical heater

The present invention relates to being arranged in the mine drilling improvement in order to the underground resistance heater of heating earth formation.

Be applicable to the resistance heater of the long section heating of subterranean formations has been developed the several years.The exploitation of these heaters is electrodes of having made to hold the oil formation structure when being used for making the regional carbonization of hydrocarbon-containiproducts, with the coefficient of mining that improves oil and reclaim hydrocarbon from oil shale.

U.S. Pat 2732195 discloses a kind of method of utilizing underground heater to create electrode.This employed heater can heat 20 to 30 meters section in underground oil shale, the temperature of arrival is 500 ℃ to 1000 ℃.Iron or evanohm resistance are used as the core parts of heating.These heating elements are owing to extending on the long section and having rational heat flux, so have high value and need sizable voltage.Preferably use more low-resistance material, in addition, preferably use malleable material, so that can create heater more economically.

Underground heater with copper heating core parts is disclosed in U.S. Pat 4570715.This core has low resistance, and it can make that having rational element voltage when heating longways the sub-surface section falls.In addition, because copper is a kind of material of stretching of opening up, this heater can be made very economically, and this class heater can heat 1000 feet long earth formations, arrive 600 ℃ to 1000 ℃ temperature, and its supply voltage is 1200 volts, add heat capacity is 100 to 200 watts every foot.But copper also has shortcoming as heating element, and when the temperature of copper heating element raise, resistance value then increased with undesirable rate of rise.If a section of heater coil overheats, this hot-zone section resistance increase will cause cascading, and it can cause the damage of element.

The underground heater that use has the stratie of lower temperature coefficient not only should improve the stability of its temperature, and power circuit is simplified.

Therefore the object of the present invention is to provide a kind of improvement electric heater that can heat long section subsurface formations, heating element wherein has low temperature-coefficient of electrical resistance and low resistance value, and uses the core of ductile metals material.

For this purpose, this subsurface electrical heaters comprises according to the present invention:

A) at least one can be arranged in the heating cable in the mine drilling, comprises the nickel of about 6% weight and the copper of 94% weight in the core that it comprises; And

B) device that electric current is provided to heating cable.

In the time of in this corronil is incorporated into this heating cable, has just obtained to have the benefit of low resistance heater and followed benefit with low resistance temperature coefficient.This heating cable material also is malleable.A kind of like this heater, thereby can be used to the temperature that sub-surface section heatedly arrives 500 ℃ to 1000 ℃, employed voltage is 400 to 1000 volts.

This heater wire damages not too easily prematurely because cable in the resistance value of hot-zone section very near the resistance value of all the other line segments.Thereby thereby focus seldom can cause lasting temperature rising to cause too early damage owing to bigger resistance.The resistance value of this element also seldom changes between original cold conditions and operating temperature.Thereby simplified power circuit.When heater is as heating being provided at long subsurface formations section and arriving temperature range when being 600 ℃ to 1000 ℃ heater, the low-resistance value of stratie of the present invention and the advantage of low resistance temperature coefficient are very great.Can heat 1000 feet long sections with this class heater.

Now the present invention is further described with reference to accompanying drawing, its accompanying drawing is:

Fig. 1: the schematic diagram that is arranged on the heater of the present invention in the mine;

Fig. 2: the graphics of the heating element of tape insulation of the present invention and shell;

Fig. 3: according to the cross section sketch plan of electricity cable of the present invention and heating cable connector; And

Fig. 4: the sectional view of this top, heating cable bottom part.

Heater of the present invention is any heater of using therein elongate elements, this long unit Part must use has low-resistance material. Copper is exactly so a kind of material, but copper is owing to it The temperature-coefficient of electrical resistance height is easy to form focus. A kind of have about 6% weight nickel and 94% weight The alloy of copper, be considered to low electrical resistant material, it has quite low resistance and low electricity simultaneously The resistance temperature coefficient. This has just caused very simple power circuit and seldom has been tending towards forming heat The point. It is hydrocarbon that elongate elements heater of the present invention can be used in exploitation and the danks of underground petroleum The exploitation of compound. Such heater is called as the mine heater usually.

Being used for putting into practice a preferred basic heater design configuration of the present invention, to be described in the U.S. special Among the sharp US4570715, this patent is quoted as proof in conjunction with conduct at this. This mine heater also can Other structure form, because the present invention is a kind of general improved heater core body metallurgy Material, it can be applied in the multiple long heater structure.

The reason that is tending towards forming " focus " that can cause that early stage heater core spare damages for minimizing Can from the various heater cores " nominal resistance " that may use relatively see. This mark Claim that resistance is the metal electric resistance when the metal electric resistance is divided by room temperature when a temperature. Because The metal electric resistance almost changes with temperature linearly, if when the core temperature raises, rise at one The metal that has low nominal resistance under the high temperature will have low-down relatively hot exporting change The nominal resistance of nickel and copper is about respectively 5.8 and 4.8 in the time of 800 ℃. And " close for No. 30 The gold " nominal resistance in the time of 800 ℃, be about 2.2. The alloy that contains 6% nickel and remaining sum and be copper exists Normal resistance in the time of 800 ℃ only is about 1.5. This has just reflected the heater core spare in expectation The main advantages of life-span aspect.

Nichrome has good normal resistance. In the time of 800 ℃, its normal resistance only Be about 1.12. But its resistance value in the time of 800 ℃ be the nickel resistance value more than three times and be about 27 times of copper resistance value. Nichrome neither a kind of extending metal. Although nickel chromium closes Gold utensil has low-down normal resistance, because its high resistance and lack ductility and make it not Can conform with the needs as long heating core.

In a preferred embodiment of the invention, heater is to have in metal-back skin inside The mine heater of heater core spare. Heater core spare is spaced apart by one with the metal-back skin Come, and in this space, filled inorganic insulating materials. This is upper with shell heater element cable Port is connected with service cable. Service cable is thermally-stabilised and with similar insulation and shell The cross-sectional area that the cable of skin, the core spare that it comprises have and the ratio of resistance can make it right The heat that the heater element transmits its generation of electric current then is low-down value. This service cable Be preferably copper shell skin, inorganic insulation and copper core, and have enough big cross-sectional area, so that Must make at the electric current that whole needs are provided and be heated in the section when producing selected temperature itself Only produce inappreciable heat.

Surrounded in the cable of conductive core part the connecing of core spare by inorganic insulation and metal-back skin The metal sleeve pipe of the most handy quite short length of head surrounds, and it is mutual that this sleeve closure cable core Welding or the part that is connected to each other. This kind electrical connection will form connection resistance, and it is at least formation The resistance value of the cable core with minimum resistance that connects. Simultaneously, around the cable core of joint The most handy a kind of special insulating materials is wrapped, and the electrical resistivity property that this insulating materials has is pressed Strong and heat conductivility at least substantially equals together the performance of cable insulation material.

Fig. 1 illustrates a mine drilling 8, and it passes " topsoil " 20 and section 21 and 22 of earth formation with extending.Section 22 is exactly the section that needs heating.

Can see from top to bottom: electricity cable 1 and 2, one selected thermoelectricity well loggings 3 that heater assembly is reeled by a pair of available reel are formed.Thermocouple 4 is being suspended in midair by thermocouple wire 5 and is being hung tight by a sinker 6.This thermocouple can utilize rotating drum 7 to rise or descend.The preferred embodiment is that heating cable is directly adhered on its position, as shown in fig. 1 with cement.In this preferred heater, on the section that its assembly housing does not extend to heater and heated.Be heated the interface of section 22 with the section 21 that need not heat, electricity cable 1 and 2 is connected via cable connector 11 and 12 with heating cable 9 and 10.Heating cable extends downwardly into the bottom that is heated section.In the bottom of heating cable, the heater chipware utilizes terminating plug 13 to be grounding on the cable shell skin.Terminating plug can utilize a device such as coupling 12 to be electrically connected.

Thermoelectric well logging, electricity cable and heating cable can be suspended in the housing.If when they were suspended in the housing, the bottom of this housing should be sealed, in case liquid enters.Liquid appears at temperature is restricted, and this is because the liquid evaporation rises on the housing, and condensation in the housing above heating cable.The liquid that is condensed can drop on the heating cable then, obtains high temperature so just stop.The preferred embodiment does not comprise housing as shown in fig. 1 in being heated section 22.Heating cable and electric heating well logging are bonded in the hoistway boring 8 with cement 23.When heating cable was bonded in the hoistway boring with cement, this heating cable shell skin must be that the material that can protect heating cable to avoid being corroded is done, because heating cable is exposed in the underground composition.

Be bonded in hoistway boring with cement thermoelectricity well logging and heating cable and removed the protection that is heated the stratum middle shell, just reduced the expense of insulation widely.If the use housing, housing must be with expensive material manufacturing, because it is in the environment of high temperature and corrosion.When removing housing, because not at heating cable vapor space on every side, thereby also improved hot transmission.Also can use a hoistway boring than minor diameter.Than the consequence of the boring of minor diameter be with heating cable with cementitious required cement than case bonding required cement in the outer hole is lacked, and the boring cost has been reduced thereupon.For eliminating liquid enters housing the problem of housing seal is also just avoided by having eliminated housing.Heating cable directly is bonded in the boring with cement,, has also just eliminated thermal expansion and wriggling owing to heating cable is fixed on their initial position.

Fig. 2 represents the preferred structure layout of this heating cable and electricity cable.With reference to Fig. 2, the chipware 100 of a conduction by the compacted inorganic insulating material spare 101 of a ring-type around, the latter is surrounded by a metal-back skin 102.The metal-back micromicro selects to be made for two-layer (not shown).Can when beginning, make quite thin internal layer, then can be with the thicker skin of erosion-resisting material in a separating step.

Fig. 3 has represented the details of Fig. 1 center tap 11.The electricity cable of being made up of conduction chipware 100 is surrounded by an inorganic insulation that compresses 101, is covered with a shell skin 102 on the latter.The conduction chipware of this electricity cable preferably copper do and have an enough big cross-sectional area, produce big heat when preventing in working order.The shell skin of this electricity cable is copper preferably.One section transitional crust skin 103 is upwards stretched by the link of electricity cable, avoids being corroded because of the high temperature near heating cable with the containment vessel skin.This containment vessel skin is preferably got and heating cable shell leather material identical materials.The containment vessel micromicro is to extend several feet to 40 feet even longer, and best distance is about 40 feet.This segment distance guarantee to make electricity cable not can because of be exposed near the heating cable high temperature down and damaged.

In Fig. 3, heating cable shell skin is illustrated as preferred two-layer shell skin, i.e. an inner casing skin 108 and an incrustation 107.The chipware of heating cable 104 is soldered on the chipware 100 of electricity cable.The cross-sectional area of heating cable 104 and resistance are such: for example can produce 50 to 250 watts every meter heat when operating current.Splicing sleeve 105 and outlet sleeve 106 move on the electricity cable or heating cable in welding cable core the place ahead.After chipware 104 and 100 was lived by weldering, splicing sleeve 105 also was soldered on the position on the electricity cable.Then, to the space of heating cable chipware 104, be filled into inorganic insulating material 101 around electricity cable chipware 100.Utilize subsequently outlet sleeve 106 moved in the space between splicing sleeve and the heating cable and make this inorganic insulating material 101 by compression.After outlet sleeve is pressed into this space, utilizes welding connecting mode that it is welded to and form sealing on the incrustation 107 of heating cable and the splicing sleeve 105.Joint 12 among Fig. 1 also is similar structure.

In order to use the present invention, preferably enough little of the diameter of cable shell skin and thickness so that cable can reel, also can easily reel by reel and pine around and unlikelyly the shell skin is curled or insulation materials is moved.The diameter of the conduction chipware in the cable then can change, and with the electric currents that allow to flow through different amounts and produce significantly big or inappreciable heat, is used for heating cable or electricity cable is decided on this conductive core material.

When using heating cable to have housing in mine, the shell skin of this heating cable is the individual layer shell skin done of No. 316 stainless steels or similar material preferably.When heating cable does not have housing, when directly being bonded in the boring with cement, preferably uses the double shells skin.Its internal layer and skin preferably all use INCOLOY800 (INCOLOY is a trade (brand) name).All the thickness of shell skin preferably is about 1/4th inches, though 1/8th inches to 1/2nd inches thickness also is admissible, they depend on desired running time, and the corrosivity of operating temperature and working environment is determined.

What Fig. 3 showed is a single core cable spare, but the most preferably cable is made into and has two cores or three cores.Each equal portability electric current in a plurality of chipwares, just having removed needs heating cable and electricity cable in parallel.In most preferred embodiment of the present invention, single phase alternating current power supply needs every cable two cores, and three-phase alternating-current supply needs every cable three cores.

The heating cable chipware is preferably in opposite place, the end ground connection in end that is connected to electricity cable with it.Comprise the preferred end plug 13 that connects by conduction end coupling 12 among Fig. 1.Fig. 4 has showed preferred end plug.This connector 13 is pressed in the end sleeve pipe 14, and the latter is welded on the shell skin 107 of heating cable in advance.This end plug is forced to be pressed into sleeve pipe and is made inorganic insulating material 101 pressurizeds.This end plug is brazed on the heating cable chipware 104 and is welded on the sleeve pipe of end then.End plug on each heating cable can link together with folder, as shown in Figure 1.When the heating cable that uses has a plurality of chipware, on the end plug each chipware is provided with a hole, and this connector as with being electrically connected of cable.

Use low electrical resistant material to simplify power circuit widely as the heating cable core, this is owing to the electric current to heater can adopt the control of zero cross point and not adopt phase shifting angle control.Difference between the cold and thermal resistance of the copper chipware heater cable of prior art is big, thereby in order to produce identical heat output, the difference between the h and c electric current is also big.

It is to utilize to allow whole supply voltages to pass through heating cable in the setting cycle number time that the zero cross point electric heater triggers control, it triggers " crossing zero cross point ", at this moment instantaneous voltage is zero, and the complete cycle that lasting conducting ascertains the number turn-offs when the instantaneous voltage zero passage.Keep then blocking the cycle that ascertains the number, so that can control the heat output that produces by heating cable.This system is designed to " blocking-up " 15 or 20 cycles in per 60 cycles.If when sort circuit must be to the significant heater setup parameter of resistance change, this control was unpractical, arrives very big numerical value because the resistance of this variation can cause required electric current.Thereby the triggering of crossing zero cross point is unpractical to the copper core heater of prior art, and heater generally can be adopted but it is the low electrical resistant material chipware.The control that alternately triggers that the copper core heater of prior art is required is that phase shifting angle triggers.It is that the part of each power-up period is delivered to the heater chipware that phase shifting angle triggers.The supply of electric power be begin to last till voltage zero-cross by non-zero voltage till.Because system's supply voltage is begun by a voltage difference, will cause significant peak current, this electric current must be that system designs to such an extent that can bear.The electric power control of therefore crossing zero cross point is always more desirable, and it is superior adopting the system of zero cross point electric power control.

Thermoelectric well logging can be set in being provided with the mine drilling of heater of the present invention.Thermoelectric well logging can be arranged in the hoistway that has housing or do not have housing, and when hoistway did not have housing, thermoelectric well logging must be a metal, and its thickness is able to take the corrosion of underground environment.The surveying record method of thermoelectric well logging and temperature is good with for example U.S. Pat 4616705 disclosed methods.Because it is considerable that the expense of thermoelectric well logging and temperature sensing device is set, only it is contemplated that and heating the thermoelectricity well logging that the stratum section is provided with peanut that is heated of mine.

Comprising the subterranean formations that changes thermal conduction characteristic may need to use the heating cable of segmentation, and they have the mine heter temperature distribution that every foot heat output is adjusted to be provided near more constant.A kind of like this segmentation heater is described in the U.S. Pat 4570715.Low electrical resistant material core mine heater has reduced the trend that focus takes place significantly, just having reduced mine heater chipware widely will have the needs that change thermal output relatively with underground heat conductivility regionality for this, but with the technology of heater wire segmentation is useful, and is that maximum heat output is reached the earth formation of setting is needed.

Claims (10)

1. low resistance electrical heater comprises:

A) at least one is arranged on the electric heating cable in the mine drilling, and this cable comprises at least one heating chipware, centers on the metal-back skin and the electrically insulating material between metal-back skin and chipware of chipware,

B) one provides the device of electric current to electric heating cable,

It is characterized in that this chip comprises the nickel of 6% weight and the copper of 94% weight.

2. according to the heater of claim 1, it is characterized in that: also comprise at least one power unit, wherein comprise at least one thermally-stabilised cable, it comprises a chipware, inorganic insulation and shell skin, wherein the cross-sectional area of chipware is littler than the heating cable significantly with the heat of the unit supply voltage that combination produced of resistance.

3. according to the heater of claim 1, it is characterized in that: wherein heating cable keeps and any liquid isolation that flows to or flow out earth formation in a housing.

4. according to the heater of claim 1, it is characterized in that: wherein heating cable utilizes cement directly to bond on the position, and is fixed in the mine without housing.

5. according to the heater of claim 1, it is characterized in that: wherein the combination of heating cable chipware cross-sectional area and resistance is corresponding to setting along the last heat conductivility of section distance in the heated earth formation so that along the zonal increase of the last average resistance of heater distance with reduce the relative amplitude that had and position and adjacent formations structure in the regionality increase of heat conductivility be associated with the amplitude and the position of minimizing.

6. according to the heater of claim 1, it is characterized in that: but wherein the hoistway heater is to utilize roll device to insert the drum cable of hoistway boring.

7. according to the heater of claim 1, it is characterized in that: wherein heating cable is by two chipwares in the shell skin, chipware is separated each other and with the electrically insulating material that chipware and shell skin separate, apply a top and bottom composition of electrical power.

8. according to the heater of claim 7, it is characterized in that: wherein two chipwares in the shell skin are connected in the bottom.

9. according to the heater of claim 1, it is characterized in that: wherein heating cable is by three chipwares in the shell skin, electrically insulating material that chipware is separated each other and that chipware and shell skin are separated, a three-phase power supplies to three top and bottoms on the chipware to be formed, and wherein three cables are connected by the conductive connecting device in the cable bottom.

10. according to the heater of claim 9, it is characterized in that: wherein heating cable is bonded in the hoistway with cement, and does not have the housing round heating cable.

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