DE2634137A1 - Hydrocarbon deposit electric induction heating - in situ by induction coil enclosing selected deposit section - Google Patents

Abstract

A method for heating natural underground deposits of hydrocarbons, esp. the tar sands of Canada and the oil shales of Colorado and elsewhere, is based on electrical induction heating of a certain section in situ. The heating coils pref. surround the selected area in a continuous or broken spiral and the heating is continued until the hydrocarbons are fluid enough to be extracted by pumping. Process is less expensive method than mining the complete sand beds and extracting the small hydrocarbon percentage. The large amt. of hydrocarbons required to generate enough heat for liquefaction by underground combustion.

Description

E r w ar m u n g e i n e r K o h 1 e n w-a s s e r -

fabric deposition.

The invention relates to the heating of an inshesandere naturally occurring materials in underground deposits, e.g. a deposit of sand with entrapped or bound crude oil.

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 bl.

Efforts have been made to extract the oil for years. Various recovery methods are suggested been. to these include the proposal to mine the sand and then remove the crude oil from the Extract sand. However, with the dismantling and the associated extraction are unacceptable high capital investments, high energy consumption, ecological damage and costs linked for extraction and refining.

Further 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 in Alberta are xnd therefore 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 electricity 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 is to be extracted can be restricted. Rather, the steam tends to blow out of the treated deposit. Up to 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 Dissolving quartz and displacing clay, resulting in flow and separation problems.

Furthermore, it has also been proposed to use part 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. However, to date, these methods have remained largely unsatisfactory 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.

The invention is based on the consideration that extraction methods for the extraction of oil from bituminous sands and the like are much more satisfactory would be if there was a satisfactory method of heating a large enough Volume of bituminous sand in place, i.e. in situ without excessive Consumption or excessive destruction e.g. by burning, charring, etc., des there would be crude oil trapped in the sand.

Accordingly, the object of the invention is to provide a possibility to heat a specific section of a hydrocarbon deposit Specify the place where there is no significant combustion of the hydrocarbon constituents on the spot within the boundaries of the nature of the constituent parts of the deposit, the environmental conditions and the devices used.

The inventive solution to this problem is characterized by electrical induction heating of a particular section of a particular underground deposition of naturally occurring hydrocarbons, in particular a deposit of sand with entrapped crude oil, in place.

In this context, the term "hydrocarbons" refers to one or more components of crude oil, lignite or other naturally occurring underground deposits understood, some of which are trapped in deposits of other substances, e.g. sand are made up of the elements hydrogen and carbon, sometimes with additional other elements.

The electrical induction heating of a specific section of the underground deposition can be effected by running alternating current through it flowing one or more underground conductors along such a path or such ways are guided that the volume to be treated of the hydrocarbon deposit is essentially enclosed. The volume is then "essentially enclosed", if it is surrounded by the conductive path in such a way that when an alternating current is passed through it an electromagnetic field is created, the strength of which is at least a considerable Section of the enclosed volume everywhere is as large as it is by induction can comfortably heat to a desired temperature, the level of which for relief the extraction of the hydrocarbons is sufficient. With appropriate determination The shape and location of the conductive path or path becomes practical within the total mass of the enclosed volume of the deposit generates heat, thereby the temperature of practically the entire mass of the treated portion of the deposit can actually be brought to such a high value that the extraction of the Hydrocarbons e.g. from artificial sources is possible.

Difficulties with the invention are due to serious non-uniformity the heating process, as it was previously in the process with pressurized steam and the Procedures with electrical current or resistance heating have occurred, avoidable, because the electrical induction heating according to the invention on the properties the heated mass is based. A bituminous sand deposit usually contains it individual quartz sand particles covered by a film of water, between which there are with the crude oil (together with suspensions of clay and other impurities) filled spaces are located. Both the bitumen and those with a water film Coated quartz particles can individually extract energy from the applied electromagnetic Field within the section of the deposit enclosed by the conductive path absorb. Therefore, the temperature of the entire heated mass will be within Gradually increase the volume enclosed by the current path when alternating current is present in the Ladder flows. It is possible that a Occasional local fillet occurs. However, this is true for the procedure as a whole irrelevant.

When the temperature of the underground hydrocarbon deposit has reached the desired value, the hydrocarbons can using known or yet to be developed extraction methods are extracted. the Invention, however, is not based on the heating of the underground deposit subsequent extraction process directed; with the invention is only the Warming is sought as such, which is then followed by the extraction or that of the extraction is accompanied. In this context it is thought that the Induction heating is continued for at least part of the period, which is required for the extraction of the crude oil.

There are BohFlösungen known, with which in the earth not only straight, vertical drill holes, but also other drill holes. These Drilling methods can be used to create a suitable underground path for one or more conductors are used, which then carry the alternating current, with which the induction heating one of the leader or from the ladders substantially enclosed section of an underground crude oil deposit is effected. With many common ones based on electrical induction heating Devices a helical coil or wire lead is used, whereby the content of the volume enclosed by the helix by induction for is heated to the purpose intended by the designer. Ideally, a Toroid-shaped line coil used, since with a toroid or torus the one with a End losses associated with helical lines are avoided. To the difficulties and avoid the hassle of drilling continuously curved paths connected, an underground helical path through each other connected rectilinear drill holes are simulated, which are at suitable angles run in relation to the vertical and on the surface at different, predetermined Points end. One or more conductors can be inserted into these drilled channels and are connected to one another by conventional methods in such a way that a continuous conductive path arises, which an economically significant volume of a selected enclosing underground crude oil deposit. If you then go through this conductive The way an alternating current flows, becomes the bulk of the material that is inside of the volume substantially enclosed by the conductive path is arranged by Induction heated.

The voltage, current, frequency and waveform of the alternating current and the duration of the application are chosen so that the temperature of the conductive path essentially enclosed mass increased to a desired value, sufficient to gasify, vaporize or liquefy the crude oil promote it in appropriate Collection wells and other areas can flow from which it can be used in a subsequent stage of crude oil production.

can be extracted.

Although the invention is primarily for use in the extraction was intended by crude oil from the bituminous sands of Alberta, it is for others too Applications of Benefit .-- In Colorado and other areas of the United States there are large blschist stores. The blister deposits lie occasionally free on the surface, but are-generally covered by other formations.-Im Kerogen is included or incorporated in the slate. Certainly is with application of the invention on this oil shale -a gradual increase in temperature of the bonded Kerogens-possible within a certain section of the slate, which through Induction is heated according to the Praktis.ch-same methods as described above under Reference to the bituminous sands in Alberta have been explained.

There are also many in North America and other parts of the world Sources of liquid crude oil exhausted with the usual - extraction methods became. Considerable amounts remain in the wells or wells Magnitude of e.g. 70% of the original crude oil deposit in the subsurface. One significant part, possibly half of the crude oil residues remaining in the underground, cannot be obtained economically with currently known methods. With such "exhausted" sources of liquid crude oil, induction heating can be avoided according to the invention probably used to control the temperature of the remaining crude oil deposits to increase underground. One can expect the temperature increase this Deposits the convertibility of the crude oil into gas or steam or its flowability improved, which may result in further extraction of crude oil from such sources is made possible in an economically justifiable framework.

After all, you can find it in many parts of North America and elsewhere as well encounter substantial subterranean lignite deposits. Of these are currently many of them not exploitable, occasionally because of a serious risk of explosion in associated bl and gas deposits. If you gas the lignite deposits, could evaporate or liquefy, an extraction of the hydrocarbon constituents would be possible with methods that have previously been used for oil and gas extraction. Obviously, the invention offers a potentially useful method here as well for heating underground lignite deposits to a temperature at which such an extraction is possible.

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. 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 underground 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. At each end of the helix or the helix extends 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 51 has a relatively low voltage and a high current applied to it. 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 of the volume ABCD within the bituminous sand layer progressively such Achieve 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 decreases outside the helical coil. When the material is within that of the helix 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 pendulum-shaped conductive Distance increases with the intensity of the electromagnetic field generated, as well with the conductivity of the energy absorbing or absorbing material that is arranged within the helix. The degree of energy absorption increases as well within certain limits with increasing frequency. Due to resonance effects can be optimal 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. This is likely because of the low thermal Conductivity of the earth and rock formations above and below a relative a small amount of energy is sufficient.

The film of water, usually consisting of salt water, which the individual Sand particles regularly surrounding many debris in Alberta contributes to absorption of energy from the applied electromagnetic field through those enclosed by the conductor Mass at. However, if the temperature of the mass rises to the boiling point of water, The water boils off as steam. This steam can be used with advantage to generate pressure can be used with which the outflow of the crude oil from the deposit is supported will.

The induction heating explained can also be applied analogously to the Apply oil slate formations found in Colorado.

In the case of residual crude oil deposits in oil fields caused by normal Methods have been exhausted, the existing drill holes could at least introduce them part of the electrical cables used to form the necessary conductive path are necessary.

Of course, the same boreholes could also be used to pump out the liquid are used, which are due to the heating of the remaining crude oil-containing mass results.

Claims Blank page

Claims (13)

Expectations. 1. Process for heating a deposit, in particular an underground deposit naturally occurring hydrocarbons, particularly a deposit of sand with enclosed crude oil, not shown by electrical induction heating a certain section of the deposit in place. 2. The method according to claim 1, d a d u r c h g e k e n nz e i c h n e t that induction heating was facilitated in preparation for the deposit Carries out extraction of hydrocarbons from it. 3. The method according to claim 2, d a d u r c h g e k e n n -z e i c h n e t that induction heating is carried out over a period of time until the Temperature of the section is in a certain temperature range. 4. The method according to claim 2 or 3, d a d u r c h g e -k e n n z e i c h n e t that one can use induction heating during the extraction of hydrocarbons from the deposit continues. 5. The method according to any one of claims 1 to 4, d a -d u r c h g e It is not stated that an alternating current is used for induction heating certain voltage, current, waveform and frequency flow through a conductor leaves, which essentially encloses the section. 6. The method according to any one of claims 1 to 5, d a -d u r c h g e it is not indicated that induction heating can be used on a bituminous Deposition carries out. 7. The method according to claim 6, d a d u r c h g e k e n n -z e i c h n e t that induction heating is carried out on a deposit in which the bitumen is bound in sand. 8. The method according to any one of claims 1 to 5, d a d u r c h g e k It is noted that induction heating is carried out on a deposit, which contains kerogen bound in slate. 9. The method according to any one of claims 1 to 5, d a d u r c h g e k It is noted that induction heating can be applied to a lignite Deposition carries out. 10. The method according to any one of claims 5 to 9, d a d u r c h g e no indication that the conductor is routed in loops or turns, which each enclose part of the section. 11. The method according to claim 10, d a d u r c h g e -k e n n z e i c does not mean that one leads the conductor along a path that is a helix or defines a toroid. 12. 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 the conductor is assembled from sections that form a helix or approximate a toroid. 13. The method according to any one of claims 1 to 12, d a -d u r c h g e k e n n n n e i n e t that one has at least one electrical conductor lengthways at least laid an underground path, the shape and location of which are chosen so that when an electrical voltage is applied to the ends of the conductor, an electrical voltage is applied Circuit is formed, which-a volume comprising the section essentially and that an electric current is allowed to flow through the conductor, its strength, frequency and duration for induction heating of the section to can be selected to a desired temperature.