CN1009670B - Method and device for heating underground region of long distance up to high temp. - Google Patents

Abstract

The present invention relates to a heater containing reelable armoured cables insulated with inorganic matter. The heater can heat a long section of underground stratum up to a high temperature for a long time. The cables are of high conductivity and can heat up the stratum to a temperature between 600 and 1000 DEG C at a basically uniform rate of more than 300 W/M approximately. The cables also have a partial electric resistance curve correlated to the heat conductivity of the stratum and thermal stability of the material, so the cables can supply the heater with electric power and support.

Description

Method and device for heating underground region of long distance up to high temp.

The present invention relates under quite high temperature, the heating of the long period that the longer interval of underground structure layer is carried out, refer more particularly to a kind of resistance heated technology, this technology can be heated to selected temperature in a certain interval underground structure layer in the time more than several years, approximately from 600 to 1000 ℃ of temperature selectable ranges, the rate of heat addition is more than 300w/m.

Know that some the interval heating to underground structure layer under higher temperature are useful than the long time.Available benefit comprises: the pyrolysis of oil shale structure layer, and the curing of uncured structure of container can make the hydro carbons of resulting heat from oils or tar enter the production area as the generation of the large-scale carbonizing zone of electrode use in the container, or the like.The technology that can realize above-mentioned time has been included in some patent, United States Patent (USP)s more described as follows.United States Patent (USP) the 2nd, 732 makes referrals in No. 195, uses the electric heater with iron or evanohm resistor, 20～30 meters interval in the subterranean oil shale can be heated to 500 to 1000 ℃ temperature.G.A. Smith's (Smith) United States Patent (USP) the 2nd, 781, make referrals to for No. 851, up to 250 ℃ temperature the time, use a kind of Low ESR heating cable that constitutes by insulation inorganic matter and copper sheath, it includes three conductors to prevent the formation of gaseous product production period hydrate, and this heater is done mechanical support by steel band and is immersed in the oil groove with anticorrosion.United States Patent (USP) the 3rd, 104, make referrals to for No. 705, use by " any heater that can produce efficient heat ", remaining hydrocarbon comes the molding sand of curing vessel in the heating molding sand up to fixed degree, but also introduced the not electric heater of heat explanation of a kind of its model, it was worked 25 hours in the time of 865 ℃.United States Patent (USP) the 3rd, 131, introduced a kind of electric heater No. 763, it can trigger the underground container oxidation reaction, introduced the another kind of heater that has resistance wire in addition, resistance wire by insulation materials on the helix tube and marshalling, this heater can heat fluid ratio such as the air that feeds in the container, United States Patent (USP) the 4th, 415, introduced a kind of technology that can form a carburization zone electrode in an oil-containing structure of container for No. 034, method is with the heating time more than 12 months under the temperature of height to 815 ℃ of the fluid in the bore hole of no outer tube.

United States Patent (USP) the 3rd, 114 has also been announced a kind of electric heater that is used to reduce drilling well Central Plains oil viscosity No. 417, and it includes insulated cable, conductive core line, insulating layer and protective metal shell.

Just the applicant can determine up to now, known being used for descending long the only limiting to of causing that the method and apparatus in 1 year can accomplish of structure layer only heating in 60 meters long or shorter interval heatedly under 600 to 1000 ℃, and generally be with structure of container in flow into or the fluid that flows out contacts, so also cooled off by fluid.In all cases, it is useful making the temperature in the interval more than 60 meters of underground structure layer remain on about 600 to 1000 ℃, and wherein, heat flows into this interval speed greater than 300w/m, and heat time heating time is super in a few years.Yet, in recent representational application, most of insulation materials will lose efficacy soon, and big and height cost of most of needed cross-sectional areas of metal that use as resistance makes the people be difficult to accept, and the voltage of Shi Yonging is also high simultaneously is difficult to acceptance and danger close.In addition, under these temperature, usually as the metal of electric conductor supply electric power, connecting material or cable cover(ing) can soften, and begins to produce plastic strain or fusing.

Up to now, just known to the applicant, about how realizing length about more than 60 meters, the rate of heat addition is greater than 300w/m, and heating-up temperature equals or to approach this problems softening or fusion temperature of most of materials unresolved for many years.

For example, another more is similar to the heater that the different structure of introducing in the prior art is provided with feature, when 450 ℃ of heating, has just lost efficacy in two days greatly.Different therewith a kind of heater structures of reeling are made up of the heater block with two No. 316 parallel stainless steel bands, and each steel band size is that the about 2.5cm of width, thickness are about 0.15cm.Place small-sized heat-resisting Electric insulator along the heater length direction every 1 meter and separate heating element.Such structure can provide a kind of heater of reeling.During greater than 60 meters, it makes comparatively economical in length, and can produce the power more than the 330w/m when adding the electromotive force of 1200 volts of less thaies.

The heater of this structure aims at that oil well uses and the heat resistant type of design is cementitious in a unlimited boring with commercially available, expects that this cement makes heating element and flows into from stratum on every side or the fluid that flows out keeps contactless state.But when on probation, this heater is very fast again to have lost efficacy, and reason is that underground water has seen through cement by the crack.Although these water have evaporated, it still can stay some salt deposits, and it finally can form the salt bridge that constitutes conductive path, because short circuit or chemically induced corrosion or both effects simultaneously make this heater failure.Sign in this point, it seems in the structure of hydrocarbon-containiproducts, so a kind of heater will lose efficacy rapidly, even under anhydrous situation, also can lose efficacy owing to the conducting element short circuit that produces carbon distribution and produce thereupon.

This shows that in the stratigraphic structure heating means of prior art, on the length direction of heater, providing of heat is uniform.When stratigraphic structure to be heated was made up of the stratum with different thermal conductivity, this even heating was very disadvantageous.In the higher stratum of thermal conductivity, heat will flow away from wellhole soon.And in the low stratum of thermal conductivity, heater block just is difficult to release heat, thereby forms focus at this place.So, will be uneven along the temperature radial distribution of wellhole, promptly in the identical distance of distance wellhole, will there be different temperature on different stratum.The appearance of this situation is for the production right and wrong border of oil harmful.

For avoiding occurring focus, the practice in the past is to make traditional heater obtain cooling.For this reason, heater is placed wellhole, and the oil of producing to flow through wellhole in heating process, thereby have only the heat of part can be used to heat stratigraphic structure.Another shortcoming of prior art is for fear of the focus appearance, can only adopt length to lack the heater of (approximating the thickness on a stratum).

The objective of the invention is to the underground structure layer interval of long distance at high temperature heated, and keep long time.And a kind of electric heater is installed, and making to have a heating element in the heated interval at least, the basic composition of said heating element or heating element group is: (a) conductive cores or conductor.They at high temperature have quite low resistance, (b) surround the insulation materials of fuse, these insulation materials have the insulated metal sheath that thermal conductivity resistive quite high under the high temperature, tensile strength, (c) fuse and outer bread, and this sheath has softening resistance tensile strength and creep resistance quite high under the high temperature.Along being heated the interval described electric heater of installing, make heater have resistance curve with variable in distance, (such as, can decide according to of the combination of fuse cross-sectional area with the unit length resistance) this curve is with relevant with the characteristic between distance along being heated thermal conductivity between stratigraphic region.These characteristics are relevant mutually, to such an extent as to the temperature of heater is becoming quite high along the lower position of some heat conduction in described interval.Like this, along on the whole heating interval, the speed that this heater produces heat and imports the stratum into is constant basically.

In the present invention, provide heating to pass the method for one section boring of subsurface formations, having comprised:

At least one electric heating cable is set, it mainly comprises: the conduction central authorities heart yearn that lower resistivity (a) is arranged, (b) insulating layer that constitutes around the non-conductive heat stable material solid particle piece by compacting of described heart yearn and (c) around the protective metal shell of above-mentioned heart yearn and insulating layer, it has goodish anti-softening characteristic and tensile strength.

At least settle a described heating cable,, described heater located in the boring of well so that heater cable to be provided so that heater is along being placed on heating stratum section, simultaneously with flow to and flow out the fluid isolation that is heated the stratum; And

Making alive makes the heater operation, and institute's making alive should be enough to produce about 600 to 1000 ℃ temperature along heater, injects so that carry out heat with described basic uniform rate, and the speed that heat injects is decided according to the thermal conductivity on adjacent stratum.

The present invention also provides a kind of well heater, comprising:

At least one heating cable, it includes more low-resistance conducting metal heart yearn; Center on heart yearn and high thermal stability is arranged and the compacting particles of inorganic material isolator of resistance; Center on heart yearn and isolator and have high thermal stability and the protective metal shell of tensile strength.

At least one bringing-up section, it extends in one section boring and comprises at least one described cable.

At least one low-temperature zone; It comprises at least one thermally-stabilised cable; Its heart yearn, insulant and sheath material are at least substantially identical with described heating cables; But the combination matching of its heart yearn cross-sectional area and resistance makes it produce the heat of the heat much less that produces than described heating cables under added voltage; The connection that connects 3 described low-temperature zone can provide electric power to heating cables from the upper Kong Weiliang away from enough from described heating cables; And generation is far below the temperature of heating cables vicinity

Described heater also comprises the supporting arrangement that supports heating cable, it makes heating cable be positioned to be close to the position that is heated the stratum, and keep with inflow and to flow out the fluid on these stratum isolated, and the conveying device that described heating cable transmits electric power under described selected voltage.

In preferred forms, the impedance of heater block fuse and the combination of its cross-sectional area are selected, make the resistance of each km be approximately 21 to 40, the heat production ability on every meter length is at least 300W.And total voltage is lower than under the situation of about 1200V between selected core and the heater block, should have the ability that obtains the selection fixed temperature between 600 to 1000 ℃.

The fuse of heater block preferably uses the non-conductive inorganic material powder piece insulation of compacting.In optimum implementation, the resistance that these insulants have, compressive strength and thermal conductivity characteristics at least should be substantially with compacting after the performance of pure zirconia magnesium powder suitable.

In each described heater block, the protective metal shell that wraps in insulation conductive cores outside is preferably selected the steel sheath for use, diameter that it has and wall thickness should be able to make it become the heating cable parts that can reel, it should have at least substantially the suitable tensile strength of performance, creep resistant and softening temperature characteristic with the heating cable parts of No. 316 stainless steel sheaths of being familiar with about 1cm diameter, 1mm wall thickness.

By metal as the heating cable parts of sheath electric and be connected with power supply equipment aspect mechanical two, comprise feed cable.Special requirement be, can enter in the sleeve for making elongated parts, heating element and electricity cable both are the cables that can reel, and they are wrapped on the Winder.

When enforcement is of the present invention, near heater block is placed between stratigraphic region to be heated, and should avoid contacting with the fluid of this place, stratum inflow or outflow.At this moment the heater block of Fang Zhiing can be used on the selected temperature of this ground layer for heating to 600 between 1000 ℃.Because do not contact with the fluid that flows and heated condition under high temperature, can be radiated on the intransitable material of fluid from heater block by the almost net quantity of heat that heater block produced, and can conduct by these materials and contiguous stratum, have only little heat to lose from heater block because of the thermal convection current process.There, heat is left and takes away in the molecule heating of fluid then.

The best method that realizes this heater block insulation is that they are wrapped the impervious material of fluid.Such as the tube wall that is sleeve pipe, this sleeve pipe in the end of heater bottom with potted line or welding sealing, perhaps make this sleeve pipe reach institute's heating interval below.And fill out envelope and/or connect a graduating valve with cement, the cement capping of sleeve bottom or similar thing should be positioned at from heater place enough far away, to avoid producing the crack because of thermoinduction makes cement.

A kind of length of the manufacturing according to the present invention is 6 meters heater,, successfully works 6 months when this heater is heated to 600 ℃ with on the casing pipe sleeve of bottom sealing-in in its outside.

In preferred forms of the present invention, received on the thermally-stabilised cable of steel sheath of similar approach insulation as the last nose end of the heating element cable of sheath by steel, it comprises a kind of cable core thicker than heating element cable, thereby the heat that produces lacks than heating cable.This thermally-stabilised " low-temperature zone " cable preferably is with copper sheath, with inorganic material insulation and and have the copper core and enough big section area should be arranged, when making it in being provided in the thermal treatment zone, produce the required electric current of selected temperature, only produce unconspicuous heat.

In the present invention, inorganic insulating material and protective metal shell encase conductive core in the cable, and the short metal sleeve of the most handy length in fuse junction entangles, and sleeve pipe entangles fuse and is welded together (or being other the connection that is electrically connected).This electrical connection should guarantee that contact resistance is equally low with the position low-resistance electric cable core resistance that is connected at least.In addition, preferably a kind of insulating powder graininess material is squeezed in around the fuse point of contact, the resistive of this material, characteristics such as compressive strength and pyroconductivity should equate with cable insulation material at least substantially.

The invention has the advantages that to make nearly all heat all send borehole wall to, and do not have heat by the fluid removal that upwards flows.Can avoid heater block to produce focus by the present invention, thereby can continue to heat with higher temperature (about 600 to 1000 ℃) chronically.

Now, with reference to the accompanying drawings detailed explanation is done in invention, in the accompanying drawings:

Fig. 1 represents to be installed in the heater of the present invention in the sleeve pipe.

Fig. 2 is the schematic three dimensional views that has the heater block of sheath of the present invention.

Fig. 3 Fig. 4 shows the contact that is applicable to copper of the present invention and steel sheath cable.

Fig. 5 is the interconnected three-dimensional assembling schematic diagram in a pair of heater parts lower end among the present invention.

Fig. 6 and Fig. 7 are for being applicable to power circuit principle figure of the present invention.

Fig. 8 is the schematic illustration of the selected method in the sleeve pipe that heater is installed in of the present invention.

Fig. 1 has expressed the well 1 that contains pit shaft 2, and it passes " table soil " layer, and the zone 3,4 and 5 of subterranean formation zone to be heated.The intransitable plate washer 6 of fluid is equipped with in the bottom of pit shaft 2, as the plate washer of welding or pour into (not shown) with cement paste, such as with cement thermally-stabilised but heat conduction.

The almost net quantity of heat that the sleeve pipe overall structure that is used for this technology is produced in should providing and guaranteeing to hole is used for the conduction heating on stratum on every side.This can flow by any fluid between stratum around stoping and heating element and realize.Heating element encases with a kind of impermeable wall of sealing below heating element, such as casing.Cut off contacting of flowing into or flow out in heating element and the adjacent formations, they are in basically because of adding hot fluid do not move and transmit in the hot environment.Therefore, the heat that produces of the heater speed of from the boring of well, discharging basically by limit with the degree of the thermal conductivity on adjacent stratum, the sleeve pipe thermal treatment zone on.

This structure is just observed from top to bottom and can be known, but heater assembly is made up of a pair of rolled power cable 7 that inserts sleeve pipe from reel 8, but only drum cable is made up of copper conductor, it is insulated the copper sheath of bag around isolator with tightly compacted magnesia powder; Can just can be used as this cable from the MI type feed cable that BICC Cables Corp. (BICC PYrotenoxLtd) obtains.

Fig. 2 has represented a kind of optimum structure setting of conductive cores bundle of the inorganic insulating material that is surrounded by compacting around it, and the insulation materials outside is surrounded by protective metal shell.Conductive cores 10 is surrounded by the ring-type inorganic insulating material 11 of compacting, and its outside is surrounded by protective metal shell 12.For the diameter and the thickness that are used for sheath of the present invention is preferably little of the cable that a kind of " can reel " can be provided, promptly this cable can be wound on the reel easily and launch from the line tube, and can not wrinkle sheath or the phenomenon of insulation materials redistribution takes place.The diameter of conductive cores bundle should change in the cable, so that can be by the electric current of different sizes in the cable when producing bigger or less heat.

As shown in Figure 1, joint 9 is received feed cable 7 on thermally-stabilised " low-temperature zone " cable 13.Cable 13 provides low-temperature space (details of joint 9 is shown among Fig. 3) in " thermal treatment zone " top of heater system.But feed cable and the low-temperature zone cable 13 that is connected with it preferably have the drum cable of structure as shown in Figure 2.Each low-temperature zone cable 13 all has its diameter but sheath that steel be made of close with the feed cable diameter, and it preferably or basically is equivalent to stainless steel, as No. 316 stainless steels.With respect to feed cable, it is long-pending that the conductor of low-temperature zone cable 13 or fuse preferably have small cross section, but will not produce or transmit the heat that the copper that is enough to damage feed cable or other sheath or feed cable and low-temperature zone cable are received contact together even as big as making the low-temperature zone cable can transmit the required full load electric current in the thermal treatment zone.This has just formed gentle but not too hot low-temperature space can progressively reduce from Heating Zone Temperature like this.

At contact 14 places, low-temperature zone cable 13 is received (details of contact 14 is shown among Fig. 4) on the middling speed heater block cable 15.In middling speed heating cable 15, fuse such as the cross-sectional area that is the copper core should be significantly less than the fuse cross-sectional area of low-temperature zone cable 13.In each cable 15, relation between the cross-sectional area of conductive core and its resistance preferably makes each cable 15 all can produce selected temperature between about 600 to 1000 ℃, simultaneously according to electromagnetic field electromotive force between selected fuse and sheath, heat with the speed that is higher than about 330w/m, and this kinetic potential between fuse and sheath should be greater than 1200 volts (breakdown voltages).Certainly, when needed, can comprise the higher or lower multistage rate of heat addition along the fixed section heating cable of given section heating cable of Different Strata.

At contact 16 places, middling speed heating cable 15 and flank speed heating cable 17 join (with respect to illustrated situation).Cable 15 with 17 and contact 16 be identical with 18 structure, difference is that cable 17 contains the conductive cores with small cross sectional, so that produce heat according to given electromotive force with the speed of the moderate rate that is higher than cable 15.

Contact 18 is received flank speed heating cable 17 on the moderate rate heating cable 19.Contact 18 can be identical with contact 16, and cable 19 can be identical with cable 15.

At end contact 20, the conductive core of cable 19 is welded together in a chamber, in they of this chamber are electric insulation (details of end contact 20 is shown among Fig. 5) end contacts 20, receive on the part structural support 21 with mechanical means, parts 21 are added with heavy rod 22, support component 21 is installed is for by means of the mechanical connection carriage 23 that is provided with at interval, all feed cables and heating cable are partly played the supporting role of vertical direction.

In situation shown in Figure 1, subsurface formations to be heated comprises the zone 3 and 5 with different thermal conductivitys, and zone 3 and 5 has close thermal conductivity, but interval 4 thermal conductivity is high a lot.

As road as known to those of skill in the art would, the existence and the position in abnormal layer in a certain interval of subsurface formations or zone can utilize many known methods to detect.For example make the well that is filled with drilling mud one class fluid reach the temperature balance, after this, just can be in the intraassay temperature of fluid and/or adjacent rock with the change in depth characteristic curve.Such temperature measuring curve has been represented the characteristic of the depth relationship between the close stratigraphic region of well of thermal conductivity and edge.Composition of layer is with the change curve of the degree of depth peripherally for density curve sound velocity curve and electrical conductivity curve, well, and similarly measurement also can be used to determine near the thermal conductivity characteristics curve of part the well between stratigraphic region to be heated.As what known, the measurement along the average properties of existence in this is interval depended in the same long interval with the minimum detection of testing tool distance in such determining.Like this, only reflect usually along the characteristic average of about 0.6 to 3 meter or long slightly distance of length with the variation characteristic curve of distance along a certain interval of boring.

As shown in Figure 1, when including the high thermal conductivity district in the interval on stratum to be heated (as interval 4), thisly deserve redress unusually, such as connecing the less cable of the preceding paragraph diameter, as cable 17.Perhaps use another kind of method, or additionally at least one section additional heating cable, (it can have identical the core cross-sectional area and the rate of heat addition with cable 15) be (as interval 4) placement along the high thermal conductivity interval.Such adjustment should change total cross-sectional area of heating cable core corresponding to the variation thermal conductivity on adjacent stratum, so that all roughly the same facing to the some place heating speed on this stratum at all.

When the heating in inhomogeneous interval will continue the long time, be preferably in the electric heater that uses this model when beginning to heat, wherein the relative rate of heat addition along high thermal conductive zone (as interval 4) is not added to the same high degree with the corresponding thermal conductivity in this stratum, and the rate of heat addition in high-conductivity layer drops to below the average conduction in whole interval to be heated.Then, through replenishing former mounted heating cable and export by additional heating cable for example is installed after being inapparent a period of time with respect to total heat time heating time, will increase along the rate of heat addition of high thermal conductive zone.

If unusual low heat conductivity interval is contained in interval to be heated, then one section thermally-stabilised power transmission cable of cross-over connection is answered in this interval, as cable 13, so that obtain a heat production speed that reduces being complementary or compensating with low heat conductivity, so that the trend that temperature increases (being caused by slowly distributing of heat in the boring) can not cause that unwanted temperature rises.At least should use a thermally-stabilised power transmission cable, the cable 13 that for example has big core cross-sectional area passed a certain low speed heating interval to heating current.

Consider a kind of copper core of the present invention and electric heating cable now.When core diameter was constant, the resistance of unit length also was constant.In uniform environment, this cable along its whole length with same speed heat production.But, in the well between sub-average a certain stratigraphic region boring, to rise along the temperature of this one deck along its thermal conductivity, reason is that the speed ratio of heat discharging is lower.This temperature increase will make the resistance of copper core increase, thereby the rate of heat addition is increased.Such position can become along temperature on the direction of the thermal treatment zone quickens rise " focus ".

According to the present invention, in these cases, the diameter of this heating cable core should be adjusted so that have the core diameter of increase when beginning near the low heat conductivity stratum.The part of adjusting like this in uniform stratum will heat with lower speed, thereby obtain lower temperature.But in the boring on contiguous low heat conductivity stratum (suitable in addition adjustment), the rate of heat addition of adjustment member will increase with the increase of temperature.Then, heating speed will equate with the heating speed of other parts in the boring substantially under the temperature higher slightly than the boring other parts, and at this moment, the heat that is produced begins by the lower stratum discharging of contiguous heat conduction.

In general, thermal conductivity and average differ and reach 30% zone and can be compensated at an easy rate between the underground stratigraphic region that is heating.The method that realizes this point is the fuse cross-sectional area increasing 10～15% with heating cable, or equivalently in conjunction with adjusting heating cable core cross-sectional area and resistance.A certain low heat conductivity stratum in the stratum, for example low by 20% than the average in interval to be heated, then the unit distance all-in resistance of adjacent heater should be less than the average in whole interval.It should be enough low so that under above temperature, will make along the rate of heat addition of this layer along the hot arc increase of the heater resistance of low heat conductivity layer to be heated interval Mean Speed near whole than the average heating-up temperature high 20% in whole interval.

In this technology, be to make heat enter the driving force on stratum to being heated stratum temperature inside gradient from holing inner.Like this, this temperature gradient is similar in the water-driven process pressure gradient as driving force.But in this technology, resistance and provide a special advantage along the characteristic curve of heater distance and thermal conductivity and along the correlation between the characteristic curve that is heated zone distance, this condition is desirable, yet but can not obtain this condition when water-driven.In this technology, in the low heat conductivity layer, this gradient increases with the increase of heter temperature.Under the situation of water-driven,, also do not find any method that can accomplish this point although wish the gradient of increase along less permeable layer yet.In this technology, help improve heat along having of the increase gradient of low thermal conductive layer and import the uniformity that is heated the stratum into.

Fig. 3 has represented the details of contact 9.As shown in the drawing, feed cable 7 has protective metal shell, and for example copper sheath, its diameter are greater than the diameter with the low-temperature zone cable 13 of steel sheath.The most handy welding method of center conductor of cable couples together.Short steel sleeve 30 is housed around the contact, and be welded on or heat after be enclosed within on the protective metal shell of cable 7.Sleeve pipe 30 preferably has enough big internal diameter, so that form enough big annular space between the steel sleeve of it and cable 13, makes it to hold the shorter steel sleeve 31 on the sheath circumference that is enclosed within cable 13.Before inserting short sleeve 31, the space of full annular basically between central module 10 and 10a and the sleeve pipe 30 is filled up with powder shape inorganic insulating material, such as using magnesia.Such material preferably is placed on the interior volume between the sheath of annular space inside between center part and the sleeve pipe 30 and sleeve pipe 30 and cable 13 simultaneously, and preferably by vibrating compacting powder material block.Sleeve pipe 31 also can push the space between the sheath of sleeve pipe 30 and cable 13, so that make inorganic powder owing to its thrust obtains further compacting.Then, with sleeve pipe 30 and 31 and the sheath of cable 13 weld together.

Fig. 4 has represented the details of contact 14, and it has represented the details of other contact in the steel sheath heating cable, as contact 16 and 18.The structure of this contact situation with contact 9 basically is identical.Yet, loaded onto steel sleeve 32 with for example machinery or welding method, it has the internal diameter that dwindles and is enclosed within part 32a on the sheath circumference of cable 13, and sleeve pipe 32 also has a large diameter part, makes to leave annular space between the sheath of sleeve pipe 32 and cable 15.After center conductor was welded together, sleeve portion 32a was soldered on the sheath of cable 13.Annular space between sleeve pipe 32 and center conductor is inserted powder shape insulation materials, collar tube sub-assembly 33 is pushed with these material powders of compacting, and be welded to subsequently on the sheath of cable 15.

Fig. 5 has represented the details of end contact 20.As shown in the figure, cable 19 passes the hole in the steel seat 20, so that make its a bit of 19a put in cylinder open in the steel seat middle body.The conductive cores of cable is welded together at solder joint 34 places, and the sheath of cable is soldered on the steel seat 20 at solder joint 35 places.The most handy thermally-stabilised electrically insulating material of the center conductor of cable surrounds, and for example uses a large amount of compacting powder shape inorganic matters and/or ceramic materials dish (not shown), subsequently central opening is sealed the steel plate (not shown) of for example burn-oning., preferably form groove 36 and match with this member by heater being received on the elongated cylindrical member 21 when supporting heater when as illustrated in fig. 1 so that the end is easy to connect with this member along the outside of end contact 20.

In general, power supply component can comprise almost any interchange or straight-flow system that this type heater is heated with higher rate (for example, 330w/m) at least.

Fig. 6 and 7 is that the best of power supply unit that is used for the heater of this type is provided with figure.As shown in Figure 6, such structure comprises the silicon controlled rectifier (SCR) (SCR that in two groups of circuit of secondary transformer TS and double base heater two are routine mutually, in parallel _s).Although one group of SCR in principle _sJust much of that, but use SCR like the category at another branch road _sHas unique benefit.The wiring diagram of examination Fig. 7, it has represented the start-up circuit FC of heater and simplification.At first, suppose SCR _sTurn to " the full startup " state.Being added on the resistor AB that represents the heater branch road and the AC will be the alternating current of 480V virtual value, and each heater branch road obtains it half.When the B point reached 240V, the C point was negative 240V, vice-versa.Because this is that balance sysmte and two heater branch roads have equal resistance, then A names a person for a particular job and remains on zero volt state or be actually earth potential.The heating cable sheath is received on the ground connection centre cap of the secondary TS of transformation.Because the A point is represented the welded contact of end 20, so with regard to practical purpose, the electrical potential difference between this contact and shell will be zero.Contact with each other on these electrical equipment but pass through without any electric current.On the point in two branch road the place aheads of heater, the electrical potential difference between sheath and central conductor increases, and finally reaches the maximum value of plus or minus 240V.

By adopting two cover silicon controlled rectifier (SCR) and zero voltage switching modes, this state still can keep under part control.Adopt zero voltage switching, power supply is not that whole conductings are exactly all to disconnect.Each reverse parallel connection circuit will begin the whole half cycle of conducting from voltage over zero.Therefore, the output of gained is complete cycle or all-wave control.Proportional with time benchmark or sampling period realization output with the time.What two SCR passed through in the sampling period is a week or integer multiples.This situation is as good as with whole conductings.

During not conducting increment, adopt the advantage of the second cover silicon controlled rectifier (SCR) just to show.Open and close the electric current in the circuit, only use a pair of SCR in the branch road _sThat's all.Yet when only using when a pair of, heater still is connected to an end of transformer, because this point rises, falls between+240 volts and-240 volts, comprises that the voltage of the whole heater that A is ordered also will rise, fall between+240 volts and-240 volts.On the other hand, when in two branch roads, all using the silicon controlled rectifier (SCR) switch, will disconnect with transformer secondary output on electric, and will remain on circuit last residing current potential, i.e. zero volt current potential when disconnecting at the whole heater of the whole off periods of silicon controlled rectifier (SCR).

When borehole heater is placed into boring and in about temperature when operation more than 600 ℃, load (being the weight/cross-sectional area of weight support component), thermal expansion and creep are three factors that play an important role, and they have determined this position (considerable time) is located and how to be remained on to heater how.For example, for the heater of pressing Fig. 1 manufacturing and installation, when central structure member 21 is that its internal diameter is 1.25cm, the stainless steel tube period of the day from 11 p.m. to 1 a.m of 1.75cm, the coefficient of thermal expansion of invar and two kinds of metals of copper is approximately 16 * 10 ^-6Cm/cm ℃, 300 meters long bringing-up sections will expand into about 304 meters long when temperature reaches 800 ℃.

When adopting shown in Figure 1 the setting, be preferably this expansion slot milling.The position of heater is configuration so preferably, so that bear pressure load (because it is shelved on the foot of hole or the borehole wall all around) in its lower end after the expansion, and the upper end is still hanging and bearing tension loading, and neutral point is positioned at the somewhere, middle part.

Because stainless creep, bringing-up section will be extended with given pace.As to be added to load factor on the heater stainless steel structure parts be 480 crust (gar), will per hour increase 0.3cm in the bringing-up section of 300 meters of 700 ℃ of durations, or annually increase 266cm, or increased 26.6m(in 10 years as it not have the words that rupture before this).

Fig. 8 has represented to eliminate the arrangement step of the variety of issue that causes owing to load, thermal expansion creep, as shown in the figure, a pair of heating cable (such as the cable among Fig. 1 15) is on fixing drum barrel, and this heating cable is looked is enough to form the helical that extends through heated zone: (a) their following nose end is connected with heater termination device (such as the terminator among Fig. 1 20).This terminator be connected to coiling lead or load bearing component (such as the parts 21 of Fig. 1) (b) their last nose end be connected to inorganic matter insulated power cable (such as cable among Fig. 1 7) on the cable drum 40.Fixedly drum barrel 41 around heating cable is supported so that it is around lead 21.Lead is drawn in the pit shaft by weight (being the weight 22 among Fig. 1).When lead 21 or load bearing component descend, pull out heater cable circle 15 from fixing drum barrel 41, so that their spirals are round load bearing component.Heater cable 15 only at their terminator 20 places, is linked on the load bearing component 21.

When load bearing component 21 descends, pull out heater cable circle 15 from fixing drum barrel, and suitably make it stretching, extension can freely enter pit shaft 43.In this process, when load bearing component stopped to descend, some tension force in the heater cable circle were released.And cable ring 15 weight own have had supporting, and remaining load is actually zero.When load bearing component 21 recovered to descend, heater cable circle 15 from bottom to top broke away from well bore wall in succession.

When heater is removed from well, make speed that heater cable 15 upwards draws hurry up than the speed that promotes load bearing component 21, this makes cable ring break away from well bore wall from top to bottom in succession, and whole like this assembly just can throw off and take out.

The wavelength WL of heater cable circle or the frequency of heater cable circle, i.e. distance between the moiety of helix as shown in the figure, depends on the fixedly diameter of drum barrel 41 and the internal diameter of pit shaft 43.When the wavelength of cable ring 15 was about 0.6m, it was in the long wellbore section of the 305m of 6.35cm that cable ring is inserted into internal diameter, and the length of cable needs than more than 305 meters 3.7 meters.

Because this heater cable step is only allowed very little thermal expansion or creep, the pressure that the setting of expanding causes will cause the elongation of cable metal parts.For example, it can cause the copper or the about 0.001cm of steelwork component elongation of the cable of every 0.075cm.Owing to utilizing the friction between the borehole wall and cable ring to avoid the gravitation load on the structure member, thereby creep unlikely appears.

The applicant finds, though the melting point of copper is 1080 ℃, and will deliquescing under much lower temperature, and it has only very little creep resistance under any temperature, and it can be configured for current carring cable heart yearn of the present invention.When the copper core is surrounded by the compacting powdered inorganic isolator (such as magnesia) in the copper sheathing, this isolator such as cable cover(ing) will retrain and fix the center copper core.Even the copper core is the cylindricality lead of a diameter 3mm, also can be heated to the temperature more than 800 ℃ safely.It is expected to reach the several years 800 ℃ life expectancy, and a 4.2mm cylindricality copper core of 12 meters far away cold section steel bushing cable is arranged approximately from 800 ℃ of bringing-up sections, and its temperature will be hanged down 200 ℃, promptly is lower than the condensing temperature (about 600 ℃) of suitable scolder.But in copper sheath rolled power cable, the about 8.25mm copper core of diameter can easily provide the high temperature bringing-up section used power, only produces a little heat simultaneously.

Usually, be used for heating cable circle of the present invention or central electric conductor at 600 ℃ to 1000 ℃, resistivity is lower than about 50m Ω mm in the time of can being included in 800 ℃ ²Any simple metal or the alloy of/m.The suitable especially material of doing heart yearn that contains has the copper of pure basically (promptly at least 99%) or nickel (the nickel heart yearn will have bigger effective diameter, when the copper core diameter is 0.3cm, be with the nickel wire of the about 0.5cm of diameter) substantially, or chromium-copper alloy.

Because the temperature-coefficient of electrical resistance of good conductor (such as copper or nickel) is all quite high, if a focus has appearred in heater, the resistivity at focus place will increase, and higher resistivity will cause more and more higher temperature.When the unique channel of in fact getting rid of heat around the heating element is when conducting away heat by adjacent stratum, can be exaggerated naturally along this temperature ascendant trend at any focus place on the length direction of any bringing-up section.The thermal conductivity on this stratum may be low as refractory brick.Thereby, in this technology, determine that part of thermal conductivity distribution that is heated the stratum of next-door neighbour's well is very important.According to this information, can be arranged total cross-sectional area of bringing-up section conductive cores, with the local low heat conductivity of compensation, in order to avoid focus therefore occurs; Or the local high stratum thermal conductivity of compensation, in order to avoid therefore low temperature is constantly developed, thus cause reducing along the heat that these sections inject.

Usually, be applicable to that the present invention central authorities weight bearing parts or lead parts can be any metal pipe or chain substantially, or similar thing, it can boring with heater fill-in well together in so that the weight of carrying heater.In optimum implementation, central authorities' weight bearing structure member (as the parts among Fig. 1 21), the heat-resisting stainless steel tube of reeling that preferably can negative load, the size of such pipe preferably can adapt with the bore diameter of well and the heater mounting method that is adopted substantially.It is best less to hole, and the installation of heater and power transmission cable is preferably adopted from reel they are sent into method in the well.The weight bearing parts preferably adopt the size that can reel, and greater than about 2.5cm, or wall thickness is no more than 0.3cm such as diameter.

By the container that mud is housed is arranged on well head, can import the such measuring cell of thermocouple by the weight bearing parts, be heated the temperature regime of section in order to the record edge.In addition, by near the well head this weight bearing pipe bottom, can inject and/or remain on the pit shaft (such as the pit shaft 2 of Fig. 1) of sealing to the inactive gas that resembles nitrogen or the argon, so that heating element is surrounded by non-corrosive air.

Claims (17)

1, the heating method of one section wellhole of passing subsurface formations comprises:

At least one heating cable is set, it mainly comprises: the conduction central authorities heart yearn that lower resistivity (a) is arranged, (b) insulating layer that constitutes around the non-conductive heat stable material solid particle piece by compacting of described heart yearn and (c) around the protective metal shell of above-mentioned heart yearn and insulating layer, it has goodish anti-softening characteristic and tensile strength

Described heating cable provides heat for heater,

It is characterized in that: described heater is located in wellhole so that heater is along being placed on heating stratum section, simultaneously with flow to and flow out the fluid isolation that is heated the stratum; And

Making alive makes the heater operation, and institute's making alive should be enough to produce about 600 ℃ to 1000 ℃ temperature along heater, injects so that carry out heat with described basic uniform rate, and the speed that heat injects is decided according to the thermal conductivity on adjacent stratum.

2, by the described method of claim 1, wherein be heated section and have 60 meters long at least.

3, by the described method of claim 1, wherein heater is arranged on fluid sealing mode in the wellhole of heater.

4, by the described method of claim 1, it is characterized in that described heating electric heating is being reeled, and send in the wellhole from least one coiler device.

5, by the described method of claim 1, it is characterized in that described heater comprises such part at least along its length: wherein resistance per unit length is different from the other at least one section above-mentioned resistance of heater.

6, by the described method of claim 1, it is characterized in that heated zones has at least the rate of heat addition of a part to obtain increasing by laying at least one additional heating cable at least, this building-out cable is parallel at least one other cable.

7, by the described method of claim 3, it is characterized in that heater and wellhole are provided with through the following steps:

The heat-resisting hollow pipe of the liquid impermeable of in wellhole, installing, it runs through and is heated section and obtains sealing in the bottom, its layout can prevent basically wellhole inner be heated any liquid flow of appearance between the stratum.

Lead parts are moved into described pipeline, and the bottom of this lead is added with weight so that it keeps straight and upright, and it is pulled through pipeline;

The nose end of going into the well of above-mentioned heating cable is connected to described guiding parts, heating cable is wound on the drum barrel of guiding parts, and wellhole end on it is connected on the described feed cable.

When above-mentioned guiding parts moves into pipeline, from drum barrel move roll out around the heating cable circle, thereby make cable spirally around guiding parts, and drop in their pipeline by guiding parts, when the immigration of described guiding parts is ended, the tension force of downward direction is released, cable then lean against on their duct wall, and be supported along wall by friction.

Continue guiding parts and heater cable are moved into pipeline, be moved to the position that the next-door neighbour is heated the stratum section up to heater cable.

8, press the described method of claim 7, it is characterized in that described guide pipe is the stainless steel tube of can reeling, its connection makes length major part bottom owing to the weight bearing parts when these parts thermal expansions of it and cable rest in the load that is under pressure on the duct bottom of holding them.

9, the wellhole heater comprises:

At least one heating cable, it comprises contains more low-resistance conducting metal heart yearn; Center on heart yearn and high thermal stability is arranged and the compacting particles of inorganic material isolator of resistance; Center on heart yearn and isolator and have high thermal stability and the protective metal shell of tensile strength,

At least one bringing-up section, it stretches in one section wellhole and comprises at least one described cable;

At least one low-temperature zone, it comprises at least one thermally-stabilised cable, its heart yearn, insulant and sheath material are identical with described heating cable at least substantially, but the combination matching of its heart yearn cross-sectional area and resistance makes it produce the heat of the heat much less that produces than described heating cable under added voltage, the connection of described low-temperature zone makes it can be from providing electric power from described heating cable last wellhole position enough far away to heating cable, and generation is far below the temperature of heating cable vicinity

It is characterized in that described heater also comprises: the supporting arrangement of supporting heating cable, it makes heating cable be positioned to be close to the position that is heated the stratum, and keeps with inflow and to flow out the fluid on these stratum isolated, and

Under described selected voltage to the described heating cable conveying device that transmits electric power.

10, by the described wellhole heater of claim 9, the combination matching that it is characterized in that heating cable heart yearn cross-sectional area and resistance is to be provided with reference to thermal conductivity and distribution mode along the described distance that is heated the stratum section, has relative amplitude relative amplitude and the position relevant with the position that increases and reduce with the part of the thermal conductivity on adjacent stratum so that average resistance increases with reducing with the part along the distance of heater.

11,, it is characterized in that cable can reel, and comprise (a) its resistance at least substantially as the low conductive core line of basic fine copper by the described wellhole heater of claim 10; (b) around the isolator of described heart yearn, it has resistance, compressive strength and the thermal conductivity of the magnesia powder agglomates that is equivalent to compacting at least substantially; (c) around the protective metal shell of described heart yearn, its diameter and wall thickness can provide and equal 316 stainless tensile strength, creep resistant and softening properties at least substantially.

12,, it is characterized in that described bringing-up section comprises a part at least like this by the described wellhole heater of claim 9; The resistance per unit length that the combination matching of its at least one cross-sectional area and resistance provides is different from other at least one section resistance per unit length.

13, by the described wellhole heater of claim 9, it is characterized in that the combination matching of heart yearn resistance and cross-sectional area makes the resistance of unit strength equate substantially on the bringing-up section of wellhole heater.

14,, but it is characterized in that wellhole heater and the feed cable that links are to insert drum cable in the wellhole with roll device by the described wellhole heater of claim 9.

15, by the described heater of claim 9, it is characterized in that heater comprises a pair of described heating cable and described heating cable power transmission device, comprising:

AC power;

The transformer that its ground connection centre cap is connected with the heating cable sheath;

Each output of transformer is all by comprising two heart yearns reverse, that circuit silicon controlled rectifier (SCR) in parallel is connected to a heating cable, and the mode of its configuration of circuit makes each and every one lights complete half cycle of conducting from voltage zero by silicon controlled rectifier (SCR);

Described rectifier is carried out the silicon controlled rectifier hot-swap route of switching at zero point.

16, by the described heater of claim 15, it is characterized in that described heating cable heart yearn is electrically connected mutually at the nose end of going into the well that is heated section.

17, by the described heater of claim 9, it is characterized in that at least one described heating cable includes contact, wherein:

The cable core of heating cable heart yearn and the insulation of another root inorganic matter and band protective metal shell is electrically connected, so that the electric conductivity of joint is equally high with a poorest heart yearn of electric conductivity in the cable core that connects at least.

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