DE2636590A1 - Oil extraction from underground deposits - by induction heating in situ to vaporise or gasify the oil - Google Patents

Abstract

Extraction of hydrocarbons from underground deposits comprises electrical induction heating of defined sections of the deposit to a temp. sufficient to vaporise or gasify at least part of the hydrocarbons, with collection of the products. Heating may be sufficient to cause cracking into gas and lower boiling liquid fractions which distil off and are collected. Used esp. for treatment of sand-bound bitumen, slate-bound kerogen and lignite-contg. deposits. Hydrocarbons can be recovered in a safe and economical way without loss by partial combustion or carbonisation, even from the extensive lignite deposits. Part of the refining process is carried out underground, making efficient use of the heat supplied. Some difficult refining problems e.g. sepn. of suspended clays from crude oil from bituminous said deposits, are avoided.

Description

E x t r a k t i o n v o n K o h l e n w a s s e r -

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The invention relates to the extraction of hydrocarbons from underground hydrocarbon deposits.

There are deposits in the northern part of the Canadian province of Alberta so-called "tar sands" (which are probably more correctly called bituminous sands should). Occasionally the deposits are exposed on the surface, but are generally covered by a soil layer of varying thickness. The bituminous Sands contain a large proportion of quartz sand, e.g. 80%, small amounts of clay, approximately 5% water and about 15, but often less, weight percent bitumen. Man estimates that the bituminous sand deposits contain more than 1012 barrels of oil, Efforts to extract the oil have been made for years. Different Recovery methods are suggested been. Belongs to these the proposal to mine the sand and then extract the crude oil from the sand. With the mining and the associated extraction, however, unacceptably high capital investments are required, high energy consumption, ecological damage and costs for extraction and refining tied together.

Other proposals are that crude oil from the sands in place and Site, i.e. extracting in situ without prior removal of the sand. Considering realizing that most minable crude oil deposits are much deeper than that bituminous sands are located in Alberta and therefore have higher temperatures and pressures than If these are exposed, the suggestion was made to enter the Bituminous sands of Alberta to create equal conditions. No success brought the use of alternating current embedded in a bituminous sand deposit at two Electrodes were applied to a section of the bituminous sand deposit through it To heat electricity heat. This was usually due to the formation of charred current paths between the electrodes, which limited the current. Since the thermal Conductivity of the deposits is relatively small, could be caused by heating individual Paths of relatively small dimensions within a bituminous sand deposit also no increase in the overall temperature of the deposit, or at least sufficient large volume of the same can be achieved to a desired value.

Another proposal is to extract crude oil from underground bituminous Extract sand deposits by forcing steam into the deposit and emulsify the bitumen. However, the use of steam requires generation large amounts of process heat on the surface. aside from that there is that Problem that the steam is not always in sufficient measure on that section the deposit from which the crude oil can be extracted can be restricted target. Rather, the steam has a tendency to blow out of the treated deposit. Half a ton of steam was required to produce a barrel of crude oil. In addition, the hot emulsions that have a high pH value tend to To dissolve quartz and displace Ton @u, from which flow and separation problems arise.

Furthermore, it has also been proposed to supply some of the crude oil Burn down on the spot and thereby generate so much heat that the temperature of the remaining part of the crude oil is increased sufficiently enough to turn it into suitable Bores can flow from which it can then be extracted or subtracted. These However, methods have remained largely unsatisfactory to date and would be a great one even if the practical feasibility is satisfactory Part of the energy stored in the underground crude oil due to the combustion process waste.

There are also nuclear explosions, albeit without experimental verification Considered the temperature and pressure in an underground deposit to increase and thereby enable the extraction of at least part of the crude oil. Certainly, however, a nuclear explosion would at least partially destroy the crude oil charred. Also, most or all of the crude oil would be that With such a procedure, if it were at all practicable, it could be won, radioactively contaminated.

Located in Cotorado and other areas of the United States large 1 slate warehouse. Sometimes the oil schist deposits are on the Surface free, but are generally covered by other formations. In Kerogen is enclosed or bound to the Glschinfern.

The extraction of the oil from the slate is also economical to this day not attractive because of the difficult problems associated with the breakup of the oil from the shale.

After all, there are sizable undergrounds in many parts of North America Lignite deposits. An economically viable method of extracting the lignite is not known. The mechanical breakdown has prevailed in the majority of the Cases proven impossible or extremely dangerous because of the serious danger that oil or gas, which are often found in connection with lignite deposits, explodes. The lignite deposits represent a large potential hydrocarbon reserve and there is a need for a safe and satisfactory method of doing this Extraction of these hydrocarbons.

Accordingly, the invention is based on the object of a method indicate with which also such hydrocarbons in safer and more economical Ways can be obtained that cannot be mined with previous methods was.

The inventive solution to this problem consists in a method for the extraction and processing of underground hydrocarbons that are in an underground Hydrocarbon or hydrocarbon containing Are located that by electrical induction heating of a certain deposit Section of the deposit in place to a temperature conducive to evaporation or gasification of at least some of the hydrocarbons in the section is sufficient and then collecting the vaporized or gasified hydrocarbons is marked on the spot.

"Hydrocarbons" means one or more ingredients naturally occurring deposits of crude oil, kerogen, lignite, etc. Understood, those made up of the elements hydrogen and carbon, sometimes including additional ones other elements, are composed.

Heating is preferred within the economically given limits effected approximately uniformly throughout the section of the deposit. Achieved thereby that all parts of the deposit have the same fractions of hydrocarbons deposited after the same or approximately the same period of time, and can for example largely avoid the problem of having some of the deposit coked during a other part still evaporating light fractions at a relatively low temperature releases and in another part of the deposit the volatile fractions are already completely exhausted, so that there are free spaces through which oxygen can penetrate, which causes fires and thereby the recovery is maximally possible Prevents hydrocarbon quantities. The induction heating of the deposit appears the best means of obtaining reasonably uniform heating while avoiding it to be the combustion of hydrocarbons. see for details on this the on patent application filed on the same day "Warming of Hydrocarbon Deposits "by the same applicant, their disclosure is hereby also made part of the content of the present application.

In many cases the hydrocarbon deposit shows a tendency for coking at sufficiently elevated temperatures. The coking products are however, often sufficiently cracked upon further heating so that the hydrocarbon constituents can be driven off as gaseous or vaporized fractions. For cracking a catalyst can be helpful or necessary; in such a case a suitable catalyst through suitable injection holes in the deposit initiate. So first the light fractions, which are at temperatures below the coking temperature in vapor or gas form, from conventional gas or Distillate extraction wells are collected, and then the temperature can be the deposition to the coking temperature and even further to the cracking temperature are raised to produce additional gaseous or vaporized hydrocarbon fractions to be able to collect from the same extraction holes.

During the entire process, some hydrocarbons can be used as Liquids flow or condense from vaporized fractions and then out Liquid collection holes are obtained.

With the invention, the significant advantage is achieved that not only the actual extraction, but also at least part of the refining happens underground. As a result, the heat entered into the subsurface becomes great largely used effectively. Also, some of the more serious ones Refining problems avoided that had to be expected up to now; this includes the problem of Separating suspended clays from crude oil extracted from a bituminous sand store became.

In addition, there is the possibility, after collecting other fractions, which could be driven out following the cracking of the coking products, To introduce or inject air into the subterranean deposit and thereby a combustion of the non-extractable hydrocarbon residues for the purpose of To effect heat generation. This heat can for example through heat exchange can be obtained with the exhaust gases or by injecting water into the hot underground Mass and recovery of the water in the form of steam. The steam can then e.g. to drive turbines for the generation of electricity or as process steam can be used for subsequent refining stages. Other uses for the heat obtained from the subsurface should be able to be found by the expert. It should be noted, however, that the underground remains are very often high May have sulfur content, so that by burning off the residues sulfur dioxide and possibly other gaseous sulphurous compounds arise, -what can be undesirable. Therefore, the final burn-off process step can be used if desired can also be omitted.

Alternatively, the sulfur contained in the gases can be known with Methods can be obtained as elemental sulfur.

From the above it also follows that the invention is not just one Possibility of extracting oil from sand or shale, but also from hydrocarbons from lignite deposits1 has not been available to mankind in practice up to now Were available. Warming an underground Lignite deposit can also be effected with the induction method, as described in the cited other patent application of the applicant is explained in detail.

Like other crude oil deposits, lignite also has a tendency to contribute coke elevated temperature; it can then be converted into gaseous or vaporized hydrocarbon fractions are cracked, which are then in extraction wells essentially in the same Collect in a manner similar to the extraction of crude oil gases or condensed distillates permit.

The following is the invention with further advantageous details explained in more detail using schematically illustrated embodiments. In the drawings show: Figure 1 - a schematic side view of a conductive path and associated electrical devices on the surface for induction heating of a certain section of a bituminous sand deposit or the like, figure 2 - a schematic plan view of the arrangement according to FIG. 1, FIG. 3 - a Schematic view of a pattern of rectilinear boreholes arranged so that the conductive path according to Figure 1 is simulated, Figures 4 and 5 - each one Schematic isometric view of an alternative underground conductive Way for induction heating of a volume of bituminous sand or the like.

The following description usually refers to bituminous Sand deposits. However, this should not be seen as a restriction; that to illustrative methods and the device to be explained according to the invention can analogously also applied to other subterranean hydrocarbon deposits will.

According to Figure 1, a bituminous sand layer 1 lies between an overburden 2 and a rock floor 3. Inside the bituminous sand layer there is an electric one Conductor 11 along an approximately helical or helical path that the Volume ABCD within the bituminous sand layer essentially encloses. In the plan view of the same area according to FIG. 2, the same is true Volume labeled ABEF. Extends at each end of the helix or the helix the conductor 11 along a path or with a section 11a or 11b vertically up to the surface of the earth 4.

From there the conductor is on the surface of the earth with two more exposed ones Sections 11c and 11d led to the secondary winding of a transformer 15. This is placed as close as possible to the point where the conductor leaves the earth, to keep ohmic surface losses small.

The transformer 15 is a step-down transformer, the underground Conductor 11 applied with a relatively low voltage and a high amperage. On the primary side, the transformer 15 is supplied with alternating current from a high-voltage long-distance line 17 via a converter 19 for frequency conversion and waveform change and a control unit 21 fed.

A capacitor 13 is connected in series with the helical conductor 11, the resonance of the conductor 11, which due to its shape a considerable Inductance has caused at the selected operating frequency.

Experimental investigations lead to the expectation that the inductive heat generation in the bituminous sand layer on the frequency of the alternating current flowing in the conductor 11 and also depends on the shape of its waveform, with an additional dependency on the temperature and other parameters during the warming of the underground Dimensions can be given. For this reason the converter 19 is provided; leave with him the frequency and shape of the waveform of the alternating current supplied to the conductor 11 influence in the desired way. However, it should later show that frequency and waveform shape of the alternating current supplied from the trunk line 17 directly are correct, the converter 19 can be omitted and the transformer instead 15 can be connected directly to the long-distance line 17 via the control unit 21. (In North America, trunk line 17 is usually single-frequency AC of 60Hz and sinusoidal waveform).

The control unit 21 should enable the setting of the current intensity, with which the transformer 15 acts on the underground conductor 11. To In a reasonable period of time, the temperature becomes at least a significant proportion it of the volume ABCD progressively one within the bituminous sand layer reach such a value at which the flowability of the crude oil improves so far has that it flows together in a collecting bore or the like. Hence, at least a thermocouple 23 is arranged at a suitable location within the volume ABCD and connected to the control unit 21 via lead wires 25. The thermocouple 23 detects the temperature of the bituminous sand layer in that enclosed by the conductor 11 Section. In its simplest form, the control unit 21 can be a temperature-sensitive Have switch that closes when the thermocouple 23 detected Temperature falls below a certain lower limit, and which opens when the detected temperature rises above a predetermined upper limit.

In the case of industrial induction heating devices, a cylindrical-helical Coil configuration often encountered, since the electromagnetic The field within the helix is strongest and uniform and its intensity outside the helical coil decreases when the material is inside of the helical coil enclosed volume is also relatively uniform, it can therefore be expected that the inductive heat energy to practically any material enclosed by the coil is transferred and a uniform heating of the entire material is achieved will. The above also applies to a toroidal coil, with a toroidal in addition, the end losses occurring with a helix are avoided. if it can therefore be economically justified in the respective situation Toroid or a simulated toroid can be used instead of a helix.

The amount of energy absorption from the bendable conductive path also increases with the intensity of the generated electromagnetic field the conductivity of the energy absorbing or absorbing material that is inside of the helix is arranged. The degree of energy absorption also decreases within certain limits with increasing frequency. Due to resonance effects, an optimal one for a certain situation with regard to energy absorption Frequency result, which can be seen during the heating period and can change during the extraction process.

A helix which is oriented at right angles to the helix according to FIGS. 1 and 2 is, can possibly be produced more easily than the helix according to FIGS. FIG. 4 shows such a helical path, essentially the section or encloses the volume GHIJ which is to be heated by induction.

In any case, the helix according to FIGS. 1 and 2 can be represented by a number Simulate interconnected straight-line conductive paths that are in can be produced in the manner shown in FIG. The conductive paths according to Figure 3 are formed in straight, interconnected boreholes. Vertical drill holes 31 and 71 are made. Drill holes 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67 and 69 are used under appropriate Angles with respect to the earth's surface are made so that these boreholes are mutually exclusive and with the vertical boreholes 31 and 71 at points 73, 75, 77, -79, 81, 83, Cut 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111 and 113, creating a simulated helical or helical path, which begins at point 73 and ends at point 113. Individual conductors can be used in the correct sections, e.g. between the intersection points and between the Earth surface and the points 73 and 113, of said boreholes and arranged are connected to each other at the mentioned intersections in such a way that a continuous conductive path is formed, which begins with the vertical section 31 and ends with the vertical section 71.

Alternatively, according to FIG. 5, several, approximately rectangular conductive Loops are formed, each of which lies within a plane and the planes of the individual loops are parallel to each other, so that an enclosed volume KLMNOP is defined. Of course the rectangular loops stay in one place, e.g. at a corner, open, so that current can flow through the loop. the Loops are then shown on the surface in FIG way interconnected in such a way that between the connection exposed on the surface 123 and the exposed terminal 125 creates a continuous circuit. Further possible arrangements of loops connected in series or in parallel should be able to be found by a specialist.

The overburden and the rocky soil that make up the underground bituminous Sand layers up and down in Alberta regularly have one significantly lower thermal conductivity than the bituminous sand.

Accordingly, it can be expected that heat losses from the crude oil deposits stay small. Heat losses from the volume of the bituminous enclosed by the conductor Sand will generally occur in the transverse direction, namely in areas of the bituminous sand lying outside the volume enclosed by the conductor. These "losses" can be used to advantage, albeit the neighboring volumes or sections of the bituminous sand are inductively heated so that the "loss" of a certain enclosed volume of bituminous sand in a useful manner bituminous to increase the temperature of an adjacent enclosed volume Sand from which crude oil is to be extracted contributes.

In fact, an entire array is thought to be inductively heated Volumes of bituminous sand to be worked on simultaneously and according to a program for continuous drilling, laying of conductors, induction heating and crude oil extraction progressively to adjacent volumes of the crude oil-bearing bituminous sand deposits spread out.

If it is desired for certain reasons, a special volume Keeping bituminous sand at an elevated temperature for long periods of time can the control unit 21 the current which is fed to the underground conductor 11, Adjust so that just the eddy current heat energy to the enclosed volume bituminous sand is released to compensate for the occurring over time small heat losses is sufficient.

Because of the lower thermal conductivity of the earth and rock formations above and below require a relatively small amount of energy sufficient.

Although the simulated helical conductive path according to Figure 3 or other applicable possible configurations, e.g. according to Figure 5, not complete uniform electromagnetic field in the area enclosed by the conductive path The conductive path can generate volume within acceptable limits be designed so that the electromagnetic field in the volume with so sufficient Approximation uniform is that the difference between the highest and the lowest Temperature that can be found in the enclosed volume can be accepted.

The bitumen has a relatively low temperature in its natural state which it is very viscous and hardly flows. After an increase in the temperature of the bitumen due to induction heating to around 95 ° C, it has a viscosity of 2 poise, what corresponds approximately to the viscosity of an SAE-20 engine oil at room temperature. It it is possible that at this temperature some bitumen in the liquid phase in extraction wells flows in at various points of the heated section of the underground bituminous deposit can be deposited in the usual way. Allegedly However is simply raising the temperature to a value on the order of 95 ° C is not enough to extract a large amount of bitumen with reduced viscosity to be able to. In addition, any bitumen available at this temperature will likely become still contain suspended clay particles and other contaminants that are undesirable and are therefore removed from the bitumen in a subsequent refining step Need to become.

When the temperature of the heated mass rises above 95 ° C And when the boiling point of water is reached, the film of water becomes the individual Sand particles usually surround the bituminous sand deposits, boiling and in Try to escape the form of vapor. This steam generation is likely to have both a positive effect as well as have a negative influence on the entire extraction process. In the positive Meaning the steam will generate pressure within the heated dimensions with the result, that by the steam pressure exerted on the bitumen, the bitumen drains into Extraction drilling is facilitated. On the other hand, it carries the individual quartz sand particles enclosing water for the relatively high conductivity of the inductively heated mass at, which is why the mass has a lot less energy from the applied electromagnetic Field can absorb if the water is allowed to escape in vapor form. The latter leaves suitable compensation measures appear advisable. This includes, for example, the return of the steam, so that a certain amount of water in the form of steam within the heated Mass remains. It may also be necessary to use other conductive materials Initiate injection holes in the heated mass. Such further conductive Substances should preferably be in the form of a fluid, i.e. either a gas or a liquid o'er Vapor, or as a solid stream of fine particles. It may also be necessary be the strength of the electromagnetic field applied to compensate for the to increase the expected drop in conductivity of the heated mass.

When the mass is heated to around 1750C, some of the lighter ones will become Fractions of the deposited hydrocarbons pass into vapor or gaseous form and can then use the usual extraction holes to collect these fractions were brought down, are distilled off.

Corresponding extraction methods are known in the prior art. After a further increase in the temperature of the heated mass from 1750C to approximately 3150C will typically lighten at least half of the existing bitumen in shape Fractions be distilled off as gas or vapor. Above 3150C it will Convert remaining bitumen into coke, which is an extremely viscous, almost solid substance is. When the temperature of the coke is increased, the coke will crack at about 370 0C in gaseous or vaporous fractions.

It can be known per se catalysts through suitable injection holes injected into the bulk to help crack the coke.

To obtain most, if not all, of the factions through cracking and distilling the coke can be produced, the mass no longer needs to be heated as 5400C. At this temperature are then probably only approximately 15% of the original bitumen mass remained in the deposit.

Because the temperature of the mass with the induction heating practical uniformly and steadily from the natural temperature to e.g. 5400C can be increased the available hydrocarbon fractions distill away in regular succession, which is why the extraction process explained in some cases must also be viewed as a refining process. Of course they can collected fractions in an aboveground refining process still further Purification, fractionation, etc.

be subjected. However, it can be expected that the distilled off and then collected crude oil fractions from many impurities, e.g. Clay, which would be present if the fractions were collected in the liquid phase. Furthermore, the crude oil can be available at the earth's surface at a relatively high temperature The amount of heat required to complete the crude oil refining process on the earth's surface is reduced compared to the normal case.

Of course, the user of the method according to the invention is free to only the lighter fractions of the entrapped bitumen at temperatures below to distill off from 315 0C. For economic reasons it can only be cheaper extract these lighter fractions and leave the rest in the soil, without going through the explained coking and cracking process. Provides the user Of course, the problem of finding a certain, desired catalyst evenly inject into the deposit. With some underground deposits this can Problem so serious that induction heating of the mass to temperatures over 3150C sensibly forbids.

However, assuming that at least in some cases the coke If the corresponding distillates are cracked, the 15% residual bitumen should be used cannot be obtained economically through further warming alone. If only the water and removed most of the bitumen from the sand are, is this is obviously relatively dry and allows compressed air to be blown through. Correspondingly, the remaining 15% of the bitumen can be burned off, namely at a firing temperature of about 760 ° C, in-which the formation with compressed air is applied. This in-place method known as "fire flooding" can potentially lead to the yield of other recoverable hydrocarbons; in any case, however, the generated heat can be made usable. The hot exhaust gases can use the same holes, which distilled to collect the previously extracted Fractions had been used to be directed to heat exchangers. After burning down What remains is a heated mass of sand with a temperature of approximately 760 ° C. The loss of warmth of the sand to the overburden layers and the soil are likely because of the very small Thermal conductivity, which these layers typically have, can be relatively small. Water could also be injected via injection holes and then shaped be recovered by steam, which initially has a temperature close to 760 ° C, but with further fin pumping of water into the sand deposit would decrease in temperature. At the same time, the steam obtained could be used as a propulsion system of turbines for generating electricity, e.g. for performing induction heating can be used. The steam could also be used as process steam for subsequent cleaning and surface refining processes can be used. Other forms of application for the available thermal energy should be found by those skilled in the art be.

It is expected that an extraction process of the above described Type can also be used with the blale deposits, although the coking and cracking would probably not be used on oil shale because the kerogen of the oil shale from lighter oil fractions composed and therefore the largest proportion of kerogen at temperatures below 5400C without Would distill away coking. On the other hand, the arrangement of the holes is likely significantly more problematic with oil shale than with the bituminous sands in the province Alberta, because fluid-like substances penetrate the sand relatively easily and evenly and can flow through it, which is not necessarily said of slates can.

Essentially the same extraction process as referenced above Bituminous sand deposits described may also apply to at least some of the underground lignite deposits. The lignite deposits which represent the largest part of the existing coal reserves are by the same relatively high conductivity as the underground crude oil deposits in bituminous sands, which is why the electrical induction heating of the Lignite deposits with uniform increase in temperature to the desired Value would be possible. As the lignite deposits are heated, some distill off the lighter hydrocarbon fractions before coke is formed will; the major part, however, will remain as coke, from which the hydrocarbon fractions after cracking in practically the same manner as described above with reference to the bituminous sands has been explained, can be distilled off.

Here, too, there is the option of adding non-extractable residues Burn off on the spot, possibly resulting in a further yield of Hydrocarbons results, but in any case heat is generated by means of suitable Heat exchange methods, e.g. introducing water and withdrawing the water in vapor form, can be obtained.

Substantially similar extraction methods can also be used for recovery further crude oil from previously mined deposits can be used with the usual methods were exhausted.

In some cases, especially with lignite deposits, the Extraction of the hydrocarbons lead to underground cavities with the consequence undesirable subsidence.

Such voids could be filled with refinery waste, sludge, or water be pumped full and used as a sink for undesirable low temperature heat will.

... claims

Claims (13)

Claims, process for the extraction of hydrocarbons from a underground hydrocarbon deposit, g e -k e n n n z e i c h n e t d u r c h electrical induction heating of a specific section of the deposit in place to a temperature that is at least suitable for evaporation or gasification some of the hydrocarbons in the section is enough and by collecting the evaporated or gasified hydrocarbons. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the portion of the deposit is heated to a temperature which is suitable for Cracking of the hydrocarbons in fractions is sufficient, which as gases or vapors distilled off and then collected. 3. The method according to claim 1 or 2, d a d u r c h g e -k e n n z It is not necessary to heat the deposit to a temperature which is sufficient for distillation lighter hydrocarbon fractions which are collected that the deposit is heated to a temperature at which it to coke Residual hydrocarbons in the deposit cause the deposit further heated to a temperature conducive to cracking the coked hydrocarbons sufficient, and that cracked hydrocarbon fractions are distilled off and collects 4. The method according to claim 3, d a d u r c h g e k e n n -z e i c h n e t that in order to facilitate the cracking of the coked hydrocarbons, a Catalyst injected into the deposit. 5. The method according to any one of claims 1 to 4, wherein the deposit possesses bound water in its natural state, which means that n.n z e i c h -n e t that one injects water into the deposit after the temperature the deposit has reached the boiling point of the bound water. 6. The method according to claim 5, d a d u r c h g e k e n n -z e i c h n e t that the water is injected in vapor form. 7. The method according to any one of claims 1 to 6, d a d u r c h g e k It is noted that the extraction is carried out on a deposit which contains bitumen bound in sand. 8. The method according to any one of claims 1 to 6, d a d u r c h g e k It is noted that the extraction is carried out on a deposit which contains kerogen bound in slate. 9. The method according to any one of claims 1 to 6, d a d u r c h g e k It is noted that the extraction is taking place a lignite Deposition carries out. 10. The method according to any one of claims 3 to 9, d a -d u r c h g e it is not noted that following the collection of the cracked hydrocarbon fractions burns off the hydrocarbon residue mentioned in section verb on the spot. 11. The method according to claim 10, d a d u r c h g e -k e n n z e i c This means that during or after the deposition is burned off, heat exchange takes place Withdraws heat. 12. The method according to claim 11, d a d u r c h g e -k e n n z e i c It does not mean that the extracted heat is converted into mechanical energy. 13. The method according to claim 11, d a d u r c h g e -k e n n z e i c This means that the extracted heat can be used as process heat for subsequent refining of the collected hydrocarbons used.