OA16332A

OA16332A - Method and apparatus for thermally treating an oil reservoir.

Info

Publication number: OA16332A
Application number: OA1201300077
Authority: OA
Inventors: Eugeny Nikolaevich Alexandrov; Dmitry Anatoljevich Lemenovski; Zdenek Koller
Original assignee: Tctm Limited
Filing date: 2010-08-24
Publication date: 2015-05-11

Abstract

It is provided a method and an apparatus for continuously thermally treating an oil reservoir, in particular a method and an apparatus for thermally treating an oil reservoir by separately introducing a first and a second composition into an oil well and contacting the first and second compositions in a pay zone of the oil reservoir to initiate a chemical reaction producing heat and gases. With the method and apparatus according to the present invention it becomes possible to simultaneously introduce the compositions into the oil well and to extract the resultant oil or oil containing mixture through the same oil well. For this a sealing device like a packer, and at least one tubing are arranged in the oil well such that the sealing device is positioned in the pay zone of the oil reservoir and that openings in the casing of the oil well are located above and below the sealing device and the tubing extends through the packer and comprises at least one opening below the packer, wherein the packer seals the annular space between the outside of the tubing and the inside of the casing of the oil well so that two fluid passages are provided having no fluid connection inside the oil well. Thermal treatment is achieved by separately introducing the first and second compositions into the oil well through the resultant fluid passages, initiating a chemical reaction by contacting the compositions in the pay zone of the oil reservoir. The chemical reaction can be maintained by introducing at least one of the two compositions and the resultant oil or oil containing mixture can be extracted at the same time through the oil well.

Description

The invention is directed to a method and an apparatus for thermaliy treating an oil réservoir, in particular to a method and an apparatus for thermaliy treating an oil réservoir by separately introducing a first and a second composition into an oil well and contacting the first and second compositions in a pay zone of the oil réservoir to initiate a chemical reaction producing heat and gases.

The method and apparatus according to the présent invention are especially useful for extracting petroleum (in the following also named as crude oil or simply oil) from waterTIooded oil réservoirs.

The extraction of petroleum from an oil réservoir usually starts with recovery methods using underground pressure in the oil réservoir which will force the oil to the surface. 15 Over the lifetime of the oil well the pressure decreases, and it becomes necessary to use other extraction methods such as using pumps or injecting water, natural gas or other gases into the oil well to bring the oil to the surface. After these recovery methods are no longer effective the oil réservoir usually still contains considérable amounts of petroleum being enclosed in small cavities or pores of the rock or sand formations.

To recover also these remaining amounts of petroleum tertiary oil recovery methods are used which mainly hâve the aim to reduce the viscosity of the petroleum. One common method is to inject hot steam into the oil well to heat the petroleum and thus to reduce its viscosity. This method, however, is efficient only up to a depth of about 1 km as otherwise the hot steam will be cooled down before reaching the pay zone. Further, with this method up to 3 to 5 months of injecting hot steam are necessary to heat up the pay zone. For producing the hot steam up to 20 to 30 % of the extracted oil is used so that the efficiency of such method is limited.

The injection of hot steam into the oil well is for instance used in the SAGD method (steam assisted gravity drainage). This method is especially used in Canada to extract oil from Canadian oil sands. In the SAGD method, two parallel horizontal oil wells in a

iength of up to about 200 m are drrfled in the pay zone of the oil réservoir, one about 4 to 6 meters above the other. In the upper well hot steam is injected, and the heated crude oil or bitumen that flows out of the formation, along with any water from the condensation of injected steam is collected by the lower one of the horizontal oil wells and pumped to the surface. As a resuit of the température increase in the heated area of the oil réservoir the viscosity of heavy crude oil or bitumen is reduced which allows it to flow down into the lower wellbore. Further fractures may be generated in the formation as a resuit of differential thermal expansion what further improves the flow of oil to the lower wellbore.

One of the major disadvantages of the SAGD method are the high costs for producing the hot steam. Up to about 20 to 30 % of the extracted oil are needed for its production. Further, as already mentioned above, the injection of hot steam is efficient only up to a depth of about 1 km as otherwise the hot steam will be cooled down before reaching the pay zone. In addition, large amount of water and large water recycling facilities are needed, wherein the availability of water is sometimes a constraining factor.

Alternative^, surfactants or solvents can be injected into the oil well to leach out the petroleum. These methods however, hâve the disadvantages that the extracted petroleum will be contaminated by these chemicals so that additional efforts and costs are necessary to recover the petroleum.

A further tertiary oil recovery method îs characterized in that a chemical reaction is initiated in the pay zone of the oil réservoir to produce hot gases which heat up the oil in the pay zone to reduce its viscosity and to support oil recovery by increasing the pressure in the oil well.

In the Russian patent applications RU 2 100 583 01, RU2 126 084 01 and RU 2 153 065 C1 are disclosed fuel and oxidizing compositions (FOC) being able to produce hot gases after initiating a chemical reaction. These compositions are intended to be introduced into the oil well of an oil réservoir for a thermochemical treatment of the pay zone. These chemical compositions are aqueous solutions containing large amounts of up to 60 % by mass or more of ammonium nitrate, NH4NO3. The other components of these FOC are for instance glycerin, nitric acid, carbamide, potassium permanganate, acetic acid, isopropyi metacarborane and acetylsalicylate. After injection

of the FOC into the oil well it is ignited by initiating a fuse explosion. The décomposition of 1 kg of FOC results in emitting a quantity of heat of about 500-1000 kcal.

These FOC contain an excess of oxygen and hence hâve a substantial oxidizing character, so that with the admixture of petroleum an explosive composition îs created.

Further, aqueous solutions containing large amounts of ammonium nitrate are explosive if the water content is below a critical amount of about 16-18 % by mass. Hence, in view of a safety handling of such compositions the water content is usually above 26-28 % by mass. However, with increasing water contents it becomes more and more difficult to achieve a stable reaction with a high output of heat.

In the RU 2 194 156 C1 the FOC contains mainly the reaction product of nitric acid with an alkanolamine, alkyl amine or alkyl polyamine and up to 2.0 to 35.0 % by mass of an inorganic nitrate such as ammonium nitrate, potassium nitrate, sodium nitrate or calcium nitrate. With such composition a more safety handling was achieved as the amount of ammonium nitrate could be reduced substantially. However, with the usual way of igniting the FOC by means of a fuse explosion, for safety reasons a mass of maximum to 2 tons can be ignited only. After décomposition of the FOC feed with a mass of 1 to tons the whole operation of the FOC delivery and initiating charge insertion has to be repeated so that at an'oil well with a depth of 1 to 2 km not more than about 10 tons of

FOC can be reacted për day. If the oil well depth is about 3 to 4 km the amount of FOC to be reacted per day ivith this method decreases to about 5 tons. Hence, the extent of heating the pay zone and thus the efficacy of this method is limited.

In RU 2 224 103 C1 are described a method and a device for thermochemical treatment of a productive layer. Like in the prior art mentioned before a combustible oxidizing composition comprising ammonium nitrate and water is pumped down into the oil well and is then contacted with an igniting material. The device used with such compositions and described in this document comprises two coaxially arranged pipes for separately introducing the compositions into the oil well. By use of sealing devices an enclosure is formed which encloses the igniting material- At the upper and lower ends of this enclosure shear pins are arranged being abie to open the enclosure and allow ignition of the chemical reaction. However, neither the method nor the device described in RU 2 224 103 C1 are efficient when used în water-flooded oil formations as they do not allow to maintain a stable and continuing reaction in the pay zone of the oil réservoir.

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In WO 2010/043239 A1, the disclosure of which is hereby incorporated by reference, is described a chemical system of gas evolving oil viscosity diminishing compositions (GEOVDC) for stimulatlng the productive layer of an oil réservoir for thermally treating an oil réservoir. These compositions are a thermal gas emitting composition (TGEC) and a reaction initiator stabiliser (RIS). By separately introducing these two compositions into the jOîl weî! and contacting them in the pay zone ofthe oil réservoir a chemical reaction is initiated producing heat and evolving gases so that the extraction of oil (petroleum) is improved. This system allows to initiated and ma intain a stable and continuous reaction so that the compositions can be continuously introduced even after the chemical reaction was initiated. Up to about 100 tons per day can be reacted so that the efficiency of the oil recovery process is improved.

In the WO 2010/043239 A1 are further described different apparatus for thermally treating an oil réservoir by using this chemical system. However, for providing these apparatus it is often necessary to manufacture spécifie components what increases the costs for the thermal treatment. Further, when using the methods and apparatus described in this document it is not possible to introduce the compositions into the oil well and to extract the résultant oil or oil containing mixture at the same time through the same oil well. When' simultaneous thermochemical treatment and oil extraction is intended it is necessary to use one oil well as an injection well and a second oil well as a producing well what limits the efficiency of this method.

It is therefore the object of the présent invention to provide a method and an apparatus for thermally treating an oil réservoir, especially a water-flooded oil réservoir, being simple and cost efficient in use and allowing a flexible control of the steps of introducing and extracting materia into or out of the oii well.

Summary ofthe invention

The above object is sqlved by providing a method of continuously thermally treating an oil réservoir comprising the steps of:

- initiating a chemica reaction producing heat and gases for thermally treating the oii réservoir to obtain extractable oil or an extractable oil containing mixture by separately introducing into an oil well of said oil réservoir a first and a second

composition through separated fluid passages provided in said oil well and contacting the first and second compositions in the pay zone of the oil réservoir;

- maintaining the chemical réaction in the oil réservoir by continuing the introduction of at least one of said first and second compositions; and

- extracting the résultant oil or oil containing mixture during said step of maintaining the chemical reaction through a fluid passage provided in said oil well, wherein inside said oil well the fluid passage used for extracting the oil or oil containing mixture has no fluid connectioni with any fluid passage used for continuing the introduction of at least o'ne of said first and second compositions to maintain the chemical reaction.

The method of the présent invention is based on the principle that in the pay zone of an oil réservoir to be thérmally treated a chemical reaction îs initiated and maintained producing heat for thë thermal treatment and preferably also gases to promote the l

thermal treatment and the extraction of oil. Such chemical reaction is initiated by contacting two compositions (chemical compositions) in the pay zone of the oil réservoir and îs maintained bÿ a continuous introduction of at least one of these two i

compositions. j

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The two compositions are introduced separately into the oil well of the oil réservoir and contacted in the pay zone of the oil réservoir to initiate the chemical reaction. For such separate introduction lof the two compositions at least two separated fluid supply passages are provîdec in the oil well. With these separated fluid supply passages the two compositions can be introduced into the oil well without contacting or admixing before reaching the pay zone.

It is mentioned above, that with the method according to the présent invention the oil or oil containing mixture is extracted during the step of maintaining the chemical reaction. It is, however, the intention that with the method according to the présent invention the oil or oil containing mixture can likewise be extracted after the step of maintaining the chemical reaction was stopped or interrupted.

According to a first embodiment of the method of the présent invention inside said oil well the separated fluid passages used for introducing the first and second compositions hâve no fluid connection, the first and second compositions are passed through openings in the casing of the oil well allowing fluid exchange between the oil well and

the oil réservoir, and the first and second compositions are contacted outside of the casing of said oil well to initiale the chemical reaction.

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With respect to the i first embodiment of the method of the présent invention the separated fluid passages used for introducing the first and second compositions and the l fluid passage used foij^- extracting the oil or oil containing mixture are provided in said oil well by arranging one |or more tubings each comprising at least one opening in its distal end section such that the distal end section of each of the one or more tubings is located in the pay zone of the oil well, and by arranging a sealing device in said oil well such that the openings in the casing of the oil well allowing fluid exchange between the oil well and the oil réservoir are located above and below the sealing device and such

I that one tubing extends through the sealing device, so that the at least one opening in

I the distal end section bf this tubing is located below the sealing device, and the sealing device seals the space between the outside of the tubing extending through the sealing device and the inside of the casing of the oil well.

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According to a second embodiment of the method of the présent invention the separated fluid passages used for introducing the first and second compositions hâve fluid connection in the second compositions are contacted in the pay zone of the oil well (i.e. inside the oil well), wherein the method further comprises the step of transferring the chemical reaction into the oil réservoir by passing the contacted compositions through openings in the casing of the oil well allowing fluid exchange between the oil well and the oil réservoir. !

pay zone of the oil well (i.e. inside the oil well) and the first and cond embodiment of the method of the présent invention the ubings each comprising at least one opening in its distal end

With respect to the se separated fluid passages used for introducing the first and second compositions and the fluid passage used for extracting the oil or oil containing mixture are provided in said oil well by arranging two section such that the distal end section of each tubing is located in the pay zone of the oit well, and by arranging a sealing device in said oil well such that the openings in the casing of the oil well ail are located above and I extends through the sa section of this tubing is iowing fluid exchange between the oil well and the oil réservoir below the sealing device and such that one of the two tubings aling device so that the at least one opening in the distal end located below the sealing device and the at least one opening in

the distal end section! of the other tubing is located above the sealing device and the sealing device seals tljie space between the outside of the tubing extending through the sealing device and thé inside of the casing of the oil well.

In both embodiments |of the method of the présent invention the oil or oil containing mixture being the resuit of the thermal treatment of the oil réservoir is extracted through one of the fluid passades (in the following also named fluid extract passage) provided in the oil well, This fluid extract passage is provided such that inside the oil well no fluid connection is possible· between the fluid extract passage and the fluid passage or fluid passages (in the following also named fluid supply passages) used for supplying the fluids or compositions!^t0 initiate and/or maintain the chemical reaction. That is, inside the oil well the fluid extracted through the fluid extract passage cannot contact or admix with the fluid or fluids introduced through the fluid supply passage(s).

When using the methc necessary to provide ônly one tubing being arranged such that it extends through the sealing device, so that ' located below the sea i are provided, a first fli the casing of the oil w by the inside of the c; separately introduce thi the pay zone of the oil extract the oil or oil containing mixture during said step of maintaining the chemical reaction as then only one fluid passage is needed to maintaining the chemical reaction so that the other one ol

A respective arrangeraient can be derived from the apparatus depicted in Fig. 1 by omitting the outer tubin d of the présent invention according to the first embodiment it is the at least one opening in the distal end section of this tubing is ing device. With such arrangement two separate fluid passages id passage defined by the inside of the tubing and the inside of ' ell below the sealing device and a second fluid passage defined asing of the oil well above the sealing device. This allows to e two compositions and to contact them outside of the oil well in réservoir to initiate the chemical reaction. This further allows to the two fluid passages can be used as the fluid extract passage.

ta 9.

d of the présent invention according to the second embodiment .itions are contacted in the pay zone of the oil well, i.e. inside the

When using the methqi where the two compos oil well, and where the chemical reaction is then transferring into the oil réservoir by passing the contacted necessary to provide ih addition to the above mentioned one tubing (i.e. first tubing) a compositions through openings in the casing of the oil well it is i

second tubing being arranged such that the at least one opening in its distal end section is located in the pay zone of the oil well above the sealing device.

With such arrangemeht of two tubîngs and one sealing device three fluid passages are provided in the oil wèll. One of these fluid passages is defined by the inside of that tubing extending through the sealing device. As the sealing device seals the space between the outside of this tubing and the inside of the casing of the oit well this fluid passage has no fluid connection with the other fluid passages and can be used as the fluid extract passage.

Two further fluid passages are defined by the inside of the other tubing and by the inside of the casing of the oil well. These two fluid passages hâve fluid connection in the pay zone of the oil well as in the distal end section of the other tubing at least one opening is provided in supply passages.

the pay zone. These two fluid passages can be used as the fluid

According to a specif tubîngs are arranged coaxially defining an inner and an outer tubing, the inner tubing extending through the inside of the casing of defined by an annular the casing of the oil ’ between the outside ot arrangement rs depicte c embodîment of the method of the présent invention the two sealing device and defining a first fluid passage (together with the the oil weli below the sealing device), a second fluid passage is space between the outside of the outer tubing and the inside of 7ell and a third fluid passage is defined by an annular space the inner tubing and the inside of the outer tubing. A respective id in Fig. 1.

Wl >f t

It is, however, also possible to arrange the two tubîngs side by side in the oil well in either a spaced or adjacent arrangement.

Such arrangements using at least two tubîngs allow to separately introduce the two compositions or only oie composition and to extract the at the same time the oil or oil containing mixture through the fluid passage (fluid extract passage) defined by the inside of the first tubing extending through the sealing device and the inside of the casing ofthe oil well beilowthe sealing device.

With the method of the different compositions présent invention it is possible to either introduce separately two or to introduce only one composition, but in any case to

simultaneously extract the résultant oil or oil containing mixture through the same oil well. i

For providing the openings in the casing ofthe oil well allowing fluid exchange between the oil well and the oil réservoir the casing may be perforated or slotted.

d the other one of the first and second compositions is introduced

In this spécifie embodiment in the step of initiating the chemical reaction one of the first and second compositions is introduced into the oil well through one of the second and third fluid passages an into the oil well throug i the other one of the second and third fluid passages and in the step of extraetîng the résultant oil or oil containing mixture it is extracted through the first fluid passage.

The first fluid passage defined by the inside of the inner tubing provides a fluid connection to that pari of the pay zone of the oil well located below the sealing device and through the openings in the casing of the oil well also to the oil réservoir. The inner tubing comprises at least one opening in its distal end section wherein this opening may be provided by an open end of the tubing and/or by a perforated or slotted distal end section of the inner tusing. The inner tubing extends through the sealing device such that the at least one opening of the inner tubing is located below the sealing device and no opening is présent above the sealing device. As such sealing device a packer can be used for instance. Th s sealing device or packer seals the résultant annular space between the outside o fluid înjected or extracted through this first fluid passage will not be mixed in the oil well with any of the fluids înjected or extracted through the second and third fluid passages.

the inner tubing and the inside of the casing of the oil well, A

The second and third i the outer tubing encloses the inner tubing. That is, the inner and outer tubing are arranged substantîally distal end section wherein this opening may be provided by an open end of the tubing and/or by a perforated or slotted distal end section of the inner tubing. The at least one opening of the outer tubing is located above the packer and preferably close to the openings in the casing packer.

uid passages are provided by rnserting an outer tubing such that coaxial. The outer tubing comprises at least one opening in its of the oil well being likewise located in the pay zone above the

With the second and tjd fluid passages it Is possible to separateiy introduce (supply) two different fluids into the oil well wîthout admixing them before they reach the pay zone of the oil well. At the distal end section of the outer tubing where the at least one opening is provided thé fluid injected through the second fluid passage, i.e. through the outer tubing, passes the at least one opening in the distal end section of the outer tubing and enters the third fluid passage where the other fluid îs injected.

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The first and second compositions are usually solutions or suspensions and are supplied by means of suitable pumps. As the pumping of the first and second compositions is continüed after contacting them in the pay zone of the oil well the mixed

I compositions are passed through the openings in the casing of the oil well, located above the packer (the sealing device), into the oil réservoir, so that the reaction initiated in the pay zone of the oit well is transferred into the oil réservoir for thermally treating it.

As a resuit of the température increase the viscosity of the oil is reduced and fractures may be generated in the formation what improves extraction of the oil so that oil or an oil containing mixture is obtained being able to penetrate through the openings in the casing located below tt e packer to be extracted through the first fluid passage.

and second compositions.

The chemical reaction n the oil réservoir is maintained by continuing the introduction of at least one of said first

The method of the présent invention as described above is characterized by the steps of introducing the chemical compositions, initiating and maintaining a chemical reaction in the pay zone of the oil réservoir and extracting the oil or oil containing mixture being the resuit ofthe therma treatment.

I of the oil réservoir an apparatus for thermally treating an oil

Thus according to a preferred embodiment this method may further comprise the step of installing in the oil we réservoir comprising a sealing device and a tubing comprising at least one opening in its distal end section, wherein

- the sealing device is positioned in the pay zone of the oil réservoir, such that said openings in the casing ofthe oil well are located above and below the sealing device;

- the tubing comprising at least one opening in its distal end section is arranged in the oil well such that it passes through the sealing device so that the at least one opening

tubing comprising at least one opening in its distal end section defines a third fluid passage and the apparatus allows fluid is located below th^ sealing device and the sealing device seals the résultant annular space between the loutside of the tubing and the inside of the casing of the oil well wherein the inside of the tubing defines a first fluid passage and the inside of the casing of the oil well above thje sealing device defines a second fluid passage.

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According to a further preferred embodiment of this method the apparatus as installed above comprises in addition to the tubing passed through the sealing device, i.e. the first tubing, a second being arranged in the éil well such that the distal end and the at least one opening of the second tubing is positioned in the pay zone above the sealing device wherein the inside of the second tubing exchange between thé second and third fluid passages in the pay zone of the oil well. The first and second tubings may be arranged coaxially so that the first tubing forms an inner tubing and the second tubing forms an outer tubing. It is, however, also possible to arrange the two tubings side by side in the oil well in either a spaced or adjacent arrangement.

In the above steps ol thermally treating an oi installing in the oil well of the oil réservoir an apparatus for réservoir the sealing device may be a packer.

In the method of the présent invention it is further preferred that the packer is positioned in the pay zone of the oil well in a section or area which comprises no openings. That is, the packer is installed below this section the exchange between the in a section being not perforated or slotted, wherein above and casing of the oil well comprises openings allowing the fluid oil well and the oil réservoir.

provide horizontal wells being located in the pay zone of the oîl

It is further preferred to réservoir being in fluid connection with the oil well. These horizontal wells can be used to better distribute the compositions introduced into the oil well and to collect the résultant oil or oil conta ning mixture.

wherein each pair of horizontal wells consist of an upper well

For this at least one psÇir of horizontal wells are drilled in the pay zone of the formation surrounding the oil wel and a lower well. Thé upper and lower wells of one pair of horizontal wells are substantially arranged parallel to each other, i.e. they are substantial vertically aligned

or the upper and lower wells of one pair of horizontai wells are arranged to approach each other. That is, w and lower wells get cio;

each other. In a speci ïc embodiment the approaching upper and lower wells intersect, preferably at their distal ends.

ith growing distance from the oil well the almost horizontal upper iser to each other ending at a distance of about 0.4 to 0.5 m from

The upper ones of the horizontal wells are arranged such that they are in fluid connection with that pàrt of the oil well located above the packer and the lower ones of the horizontal wells are arranged such that they are In fluid connection with that part of the oil well located below the packer.

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When using the first embodiment of the method according to the présent invention where the two compositions are contacted outside of the oil well one of the first and second compositions h supplied through the fluid channel defined by the inside of the tubing and the inside ofthe casing ofthe oil well below the sealing device to the lower ones of the horizontal wells. The other one of the two compositions is supplied through the fluid channel definad by the inside of the casing of the oil well above the sealing device to the upper on as of the horizontal wells. In this embodiment it is preferred that the upper and lower wells of one pair of horizontal wells are arranged to approach each other and it is further preferably at their dista jreferred that the approaching upper and lower wells intersect, i ends to form a reaction zone distant from the oil well.

compositions corne into contact either through cracks between and lower wells or at the point of intersection of the upper and :al reaction producing heat and gases is initiated and a reaction dîI well is created. This allows on the one hand to reduce the

That is, when the two the approaching upper lower wells the chemic zone distant from the thermal load on the casing of the oil well and the sealing device (like a packer) and on the other hand allows to thermally treat a greater area around the oil well.

When the chemical reaction is initiated it is possible to only provide only one of the two compositions through one of the two fluid passages to maintain the chemical reaction and thus to continuously thermally treat the oil réservoir. In that stage of the method it is possible to extract the résultant oil or oil containing mixture through the other one of the two fluid passages.

When using the second embodiment of the method according to the présent invention where the two compôsitions are contacted inside of the oil well and the chemical reaction is transferred ithrough openings in the casing of the oil well into the oil réservoir the contacted composions can be passed through the openings in the casing of the oil well into the upper ones of the horizontal wells so that the réaction can be dîstributed in a large area ofthe oil réservoir. Further, the résultant oil oroil containing mixture can be extracted through the lÎower ones of the horizontal wells to the first fluid passage so that is possible to collect thé oil out of a large area ofthe oil réservoir.

The distance between;the upper and the lower ones of one pair of horizontal wells at their proximal ends adjacent to the oil well dépends on the thickness of the pay zone and the geological structure of the oil-bearing layer. When using the method of the présent invention the distance between the upper and the lower horizontal wells may be 1 to 12 m or even longer. As a preferred range a distance of 3 to 6 m can be defined.

that they may hâve a length of up to 200 m or even longer and a

The length of the horizontal wells is likewise dépendent on the geological structure of the oil-bearing layer so preferred range of up tô 100 m.

the ch emical reaction is initiated and to use as the second initiator stabilizer (RIS) containing chemical compounds înitiating

In the method of the présent invention it is preferred to use as the first composition a thermal gas emitting composition (TGEC) containing chemical compounds producing heat and gases after composition a reaction said chemical reaction when contacting the TGEC.

As such TGEC and

RIS the compositions described in the above mentioned

WO 2010/043239 A1 can be used, for instance.

In the method of the présent invention in the step of maintaining the chemical reaction s or only one of these two compositions can be supplied to the either both composition oil réservoir. When a stable reaction in the pay zone is achieved it is preferred to suspend the introduction of at least one of the first or second chemical compositions and to continue the introduction of the other one of the first or second chemical compositions.

For instance, if the température at the place of reaction is in or above the range of about 200-300 °C the introduction of the RIS can be interrupted as at such températures the TGEC will react stabe also without an additionaî ignition. That is, with the présent invention it is possible to maintain a stable reaction by pumping only TGEC into the oîl well. Below a température of about 180-200 °C în the productive layer the injection of RIS can be resumed. j i

When supplying only one composition it is preferred to provide any liquid oxidizer like an aqueous solution or süspension of one or more of ammonium nitrate, potassium nitrate, sodium nitrate and calcium nitrate as these compounds are relatively cheap. That is, it is preferred to mainly a!dd TGEC.

If the température in tljie pay zone has reached a sufficient high value and if suffirent oxygen is présent in the pay zone an in-srtu combustion of the oil in the pay zone of the oil réservoir can be sÏarted. If such in-situ combustion is established it is no longer necessary to introducejthe first or second composition introduced so far to continue the production of heat and gases. It is sufficient to introduce air as an oxidant to maintain this in-situ combustion of oîl. The air can be introduced through any of the fluid passages having no fluid connection with the fluid passage(s) used for extracting the oil or oil contaîning mixture. Thus the air can be regarded as one of the first and second compositions as it is introduced to maintain the chemical reaction în the oil réservoir.

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With the method of tl· direction of the oil or oi the above mentioned stable reaction is achieved and only one of the compositions needs to be introduced. For this the composition is introduced through the first fluid passage and the oil or third fluid passages.

e présent invention it is further possible to reverse the flow contaîning mixture in the treated area of the oil réservoir when oil contaîning mixture is extracted through the second and/or

This further allows extracting of larger amounts of oil or oil contaîning mixture as the cross-sectional areas of cross-sectional area of tl the second and third fluid passages are usually larger than the he first fluid passage.

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For improve the control of the method of the présent invention the température above and/or below the packer can be measured. For this one ore more température sensors may be installed above and/or below the packer.

With the method of th^ présent invention high températures and high pressure can be achieved in the oil resërvoir. In most of the oil réservoirs water is présent as the resuit of recovery methods injecting water or water vapor, like the SAGD method (steam assisted gravity drainage). With the method ofthe présent invention it becomes possible to also thermally treat such water flooded oil réservoirs. As a resuit of the high températures water va >or is produced and with increasing température and pressure in the treated area this instance the density an>

water vapor changes its physical characteristics, wherein for d solvent power of the water vapor increases.

Further, under the effect of high température and increased pressure there will occur cracking of oil what leeds to an enrichment of light volatile fractions in the crude oil. At this stage viscosity is creatly reduced and solubility of gases in oil and mutual solubility of water and oil greatly increases. The mixture of water, oil and gases becomes more liquid (i.e. less viscous) and thus will more easily pass to the oil well for extraction.

Such effects will be further improved when components of the oil containing mixture reach supercriticai conditions. Following îs given a short overview of the critical température Tr and critical pressure Pr of some of the compounds being présent in the oil containing mixture.

Name		Formula	T_k rci	Pk [MPa]
Methane		ch₄	-82.6	4.60
Propane		C₃H_e	96.7	4.25
Pentane		c₆h₁₂	196	3.33
Octane		CgHig	296	2.49
Decane		CioH₂₂	346	2.08
Dodecane		Ci₂H₂ç	385	1.82
Tetradeca	îe	Ci₄H₃o	422	1.60
Water		h₂o	374	22.1

When one or more components of the oil containing mixture reach supercriticai conditions the effîciency of the oil extraction is further improved.

rl f

i i

antageous in heavily water-flooded oil réservoirs where a high

This is especially adv amount of water is présent in the area around the oil well which reduces efficiency of the usually used reco présent invention aliows efficient oil extraction as high température and pressure is generated directly in the oil-bearing layer. This results in a reduced viscosity of the oil and in an improved splvent power of the water présent in the oil réservoir. Further, thermal stress of the introduced into the oit Vvell to carry out the thermal treatment can be kept small as these components are cooled by the continuously introduced fluids.

very methods. Even in these oil réservoirs the method of the oil well, i.e. the casing of the oil well, and the components

If aluminum in form of introduced as one ofthi réservoir with water, additionally the température in the treated area of the oil réservoir is increased above about 300 to 350 °C arid a sufficient high pressure is reached (about 70 to 200 bar) the oil in the oil réservoir is fine particles or granules of aluminum or an aluminum alloy is e compositions, this aluminum will react in the pay zone of the oil preferably acidic water, to produce hydrogen gas. When subjected a hydrocracking process.

With such hydrocracking process the viscosity of the oil in the treated oil réservoir îs considerably reduced as the more complex hydrocarbon molécules are broken down to simpler hydrocarbon m< aluminum alloys in this réservoir.

lolecules. A further bénéficiai effect ofthe use of the aluminum or process is the réduction of the amount of water présent in the oil

Such hydrocracking process may be further supported by adding suitable métal catalysts such as métal salts of Mn, Fe, Cr, Co, Ni or V.

The présent invention further comprises an apparatus for thermally treating an oil réservoir by separately introducing a first and a second composition into an oil well and contacting the first and second compositions in a pay zone of the oil réservoir to initiate a chemical reaction producing heat and gases, wherein in the pay zone a casing of the oil well comprises openings to allow fluid exchange between the oil well and the oil réservoir, comprising:

ng of the oil well are located above and below the sealing device; at least one opening in its distal end section being arranged in i

I i

- a sealing device being positioned in the pay zone of said oil réservoir, such that said openings in the cas

- a tubing comprisinç the oil well and passed through the sealing device such that the at least one opening is located below the space between the outside of the tubing and the inside of the casing of the oil well, wherein the inside ofthe tubing defines a first fluid passage and the inside of the casing ofthe oil well above the sealing device defines a second fluid passage.

sealing device and the sealing device seals the résultant annular is possible to separately introduce two fluids through the oil well arrangement of the tubîng and the sealing device allows no fluid efined by the inside of the casing of the oil well above the sealing

With such apparatus it and into the pay zone φί the oil réservoir without admîxing the two fluids before reaching the oil réservoir as the contact between the first fluid passage defined by the inside of the tubing and the second fluid passage d< device (or with other v/ords; defined by the annular space between the outside of the tubing and the inside of the casing of the oil well above the sealing device). This allows to initiate a chemical reaction producing heat and gases in the pay zone of the oil réservoir to thermally treat the oil réservoir and to obtain extractable oil or an extractable oil containing mixture.

is further possible to supply through one of the first and second treating the oil réservoir and to extract at the same time the or oil containing mixture through the other one of the first and Therefore, a continuous thermal treatment of an oil réservoir e extraction of oil through one oil well is possible when using the

With such apparatus it fluid passages only one fluid or composition to the oil réservoir to maintain the chemical reaction for thermally obtained extractable oi second fluid passages and at the same time tH apparatus of the prése nt invention. A respective apparatus can be derived from the apparatus depicted in Fig. 1 by omitting the outer tubing 9.

In a preferred embodiment of the apparatus of the présent invention further comprises in addition to the tubing passed through the sealing device, which can be named as the first tubing, a second tubing comprising at least one opening in its distal end section being arranged in the οψwell such that the distal end and the at least one opening ofthe second tubing Is positi oned in the pay zone above the sealing device, wherein the

i

I i

inside of the second tubing defines a third fluid passage and the apparatus allows fluid exchange between the second and third fluid passages in the pay zone of the oil well.

With such preferred embodiment of the apparatus it is possible to separately introduce two fluids or compositions into the oil well through the second and third fluid passages and to contact the two fluids or compositions in the pay zone of the oil well to initiale and maintain a chemical reaction to thermaliy treat the oil réservoir and to obtain extractable oil or an extractable oil containing mixture. With such preferred embodiment of the apparatus it ψ further possible to extract at the same time the obtained extractable oil or oil coptatning mixture through the first fluid passage.

The apparatus of the présent invention is further characterized in that in the area where the sealing device is installed the casing of the oil well comprises no openings. The above mentioned openings provided in the casing of the oil well for a fluid exchange between the oil well and the oil réservoir are located in the pay zone above and below that area.

The sealing device is p referably a packer.

In a spécifie embodiment of the apparatus of the présent invention the first and second tubings are arranged coaxially and the second tubing as an outer tubing encloses the first tubing as an inner by the annular space casing of the oil well between the outside of tubing. In such arrangement the second fluid passage is defined between the outside of the outer tubing and the inside of the and the third fluid passage is defined by the annular space the inner tubing and the inside ofthe outer tubing.

In a spécifie embodiment according to the présent invention theapparatus further comprises at least one pair of horizontal wells, consisting of an upper and a lower well being arranged substantially parallel to each other or being arranged to approach each other, wherein the upper ones of the horizontal wells are in fluid connection with that part of the oïl well loca are in fluid connection with that part of the oil well located below the packer.

:ed above the packer and the lower ones of the horizontal wells élis of one pair of horizontal wells are may be spaced by about 1

The upper and lower w to 12 m, preferably by about 3 to 6 m. Further, the horizontal wells may hâve a length of

I up to about 200 m, preferably of up to 100 m. The horizontal wells may hâve a diameter of about 5 cm.

The apparatus according to the présent invention may further comprise at least one température sensor to [measure the température above and/or below the sealing device

I or packer.

Figures

With respect i

to' the I method and apparatus of the présent invention preferred embodiments are described in the following, wherein references to the enclosed figures are made, wherein:

Figure 1 shows schematically the arrangement of the components of the apparatus according to the prese treated and the fluid passages and flow directions used in the method of thermally treating an oil réservoir ht invention in the pay zone of the oil réservoir to be thermally according to the présent invention; and

Figure 2 shows flow d rections used in another spécifie embodiment of the method of thermally treating an oil réservoir according to the présent invention.

Following are shown the meanings ofthe reference signs used in figures 1 and 2: casing of the oil well pay zone oil réservoir openings in the casing ofthe oil well above the packer openings în the ci inner tubing opening ofthe in packer outer tubing openings of the duter tubing upper well of a pair of horizontal wells lower well of a pair of horizontal wells température sensors asing of the oil well below the packer per tubing first fluid passage third fluid passade second fluid passage first composition (e.g. TGEC) second composition (e.g. RIS) oil or oil containing mixture cheap oxidant (e.g. air) i

i

Detailed description of the présent invention i

In Fig. 1 is schematicàlly shown the arrangement of the components of a preferred embodîment of the apparatus according to the présent invention in the pay zone of the oîl réservoir to be thermally treated. In Fig. 1 are further indicated the fluid passages and flow directions use d in a preferred embodîment of the method of thermally treating an oil réservoir according to the présent invention.

In the pay zone 2 of the oil réservoir 3 the casing 1 of an oil well is perforated at two sections so that openiigs4 and 5 are provided allowing fluid exchange between the inside of the oil well and the oil réservoir suirounding the oil well. Between these two perforated sections a packer 8 is installed in the oil well so that the casing 1 of the oil well comprises openings 4 located above the packer and openings 5 located below the packer.

An inner tubing 6 is inserted into the oil weil and through the packer 8 so that the packer 8 seals the resjitant annular space between the outside of the inner tubing 6 and the inside of the casing 1 of the oil well. The lower end (distal end) of the inner tubing 6 is open to proyide an opening 7 for extracting or injecting a fluid out of or into the oil weil. Thus, the inside of the inner tubing 6 defines a first fluid passage 14.

An outer tubing 9 is insbrted into the oii well such that it encloses the inner tubing 6 and that the inner and outer tubing are arranged substantially coaxial. In the distal end section the outer tubing 9 is perforated to provide openings 10 for allowing fluid exchange between inside and outside of the outer tubing 9. The perforated section of the outer tubing 9 is located close to the openings 4 in the casing of the oil weli above the packer.

t «

«

With such arrangement of an inner and an outer tubing a second fluid passage 16 is defined by the annulai space between the outside of the outer tubing 9 and the inside of the casing 1 of the oil well and additionally a third fluid passage 15 is defined by the annular space betweèn the outside of the inner tubing 6 and the inside of the outer tubing 9.

In the spécifie embodiment illustrated in Fig. 1 two pairs of horizontal wells are arranged extending substantial consiste of an upper vÿell 11 and a lower well 12 being arranged substantially parallel to each other and thus are aligned substantially vertical.

i

The upper wells of the the oil well 1 above tirs packer and the lower wells of the horizontal wells are arranged to contact the perforated section of the oil well 1 below the packer. The upper and lower horizontal wells are sp;

ofabout 200m.

y rectangular from the oil well. Each pair of horizontal wells horizontal wells are arranged to contact the perforated section of aced by about 5 m, hâve a diameter of about 5 cm and a length

The arrangement of such horizontal wells is for instance known from the SAGD method (steam assisted gravitv drainage) where hot steam is injected into the upper ones and oil is extracted through the lower ones of the horizontal wells.

of horizontal wells are depicted. However, it should be noted that

In Fig. 1 only two pairs also only one pair of Horizontal wells and also more than two pairs of horizontal wells can be arranged in fluid connection with the oil well and can be used in the method of thermally treating an oif réservoir according to the présent invention.

Further, two temperattu above the packer and i method of thermally treating the oil réservoir.

ire sensors 13 are provided in the pay zone of the oil well, one one below the packer, to measure the températures during the

Following is described réservoir according to t a spécifie embodiment of the method of thermally treating an oil :1e présent invention.

One step of this method is to install into an oil well of the oil réservoir 3 to be thermally treated a packer 8, an depicted in Fig. 1.

inner tubing 6 and an outer tubing 9 as described above and i

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i

A further step of this method is to separateiy inject two different compositions 17 and 18 into the oil well and contact them in the pay zone 2 of the oil well to initiate chemical reactions producing heat and gases. As these two compositions the thermal gas emitting composition (TGEC) and the reaction initiator stabilizer (RIS) disclosed in 5 WO 2010/043239 A1 can be used for instance. With these compositions it is possible to initiated and maintain a stable and continuous reaction so that the compositions can be continuously introduced even after the chemical reactions were initiated.

Following is provided a description of these compositions which can be used with the method and apparatus of the présent invention.

The TGEC is an aqueous solution or suspension comprising at least one compound selected from the group consisting of hydrazine nitrate, 1,1-di C₂.₆ alkyl hydrazine nitrates and 1,2-di C₂.e alkyl hydrazine nitrates, such as 1,1-dimethyl hydrazine nitrate or 1,2-dimethyl hydrazine nitrate, guanidine nitrate, formamide nitric acid adduct, acetamide nitric acid adduct, acetonitrile nitric acid adduct, urea nitric acid adduct, ammonium nitrate, potassium nitrate, sodium nitrate, calcium nitrate, mono, di and tri Cj_5 alkyl amine nitrates, mono, di and tri C-j.g alkanol amine nitrates, C₂_6 alkylene diamine mono and dinitrates and poly C^g alkylene polyamine polynitrates.

The RIS is a liquid and comprising at least one compound selected from the group consisting of:

- métal borohyd rides MBH₄, wherein M is Li, Na or K;

- aminoboranes (R¹R²R³)NBH3, wherein R¹, R² and R³ are independently hydrogen or C|_io alkyl, or wherein R¹ is an aryl or pyridine with up to 10 carbon atoms and R²and R³ are hydrogen;

- dialkylaluminates MA1H2R¹R², wherein M is Li, Na or K, and R¹ and R² are independently C-i^q alkyl;

- aminoalanes (R'^!R²R³)N AIH₃, wherein R¹, R² and R³ are independently hydrogen or i

C-f-10 alkyl;

- alkali métal nitrites M

NO2; and

- aluminum or aîuminum alloys with magnésium or other metals, which assure stable reaction with alkaline and acidic aqueous solutions.

The TGEC and the RIS are both liquids which can be introduced into the oil réservoir by means of pumps. If the used compounds are not liquid as such they are used as solutions or suspensions in an appropriate solvent. If the TGEC and the RIS are suspensions their viscosity is such that they still are pumpable and can be pumped into 5 the oil well with a rate of up to 4-8 liters per second.

Spécifie examples of compounds which can be used for the TGEC are mono-, di- and triethanolamine nitrates, mono-, di- and triethylamine nitrates, polyethylene polyamine polynitrates, ethylene diamine mononitrate, ethylene diamine dînitrate, alkylidene diamine mono- and dinitrates.

For the TGEC it is preferred to use an aqueous solution or suspension comprising at least one compound selected from the group consîsting of hydrazine nitrate, 1,1-di C₂._salkyl hydrazine nitrates and 1,2-di C₂.₆ alkyl hydrazine nitrates, such as 1,1-dimethyl hydrazine nitrate or 1,2-dimethyl hydrazine nitrate, guanidine nitrate, formamide nitric acid adduct, acetamide nitric acid adduct, urea nitric acid adduct and acetonitrile nitric 15 acid adduct.

The TGEC is preferably the reaction product of reacting nitric acid with the respective amino compounds like reacting hydrazine with nitric acid such that hydrazine nitrate is obtained. By reacting nitric acid with these amino compounds the respective nitrate compounds or nitric acid adducts are obtained.

If the TGEC contains one or more of ammonium nitrate, potassium nitrate, sodium nitrate or calcium nitrate these nitrates are contained in the TGEC with not more than 50 % by mass, preferably not more than 30 % by mass.

The pH value of the TGEC is preferably about 3 to 14 depending on the RIS and TGEC compositions. It is further preferred that the mixture of TGEC and RIS has a pH value 25 <7.

For the above mentioned aminoboranes, dialkylaiuminates and aminoalanes it is preferred that the alkyl moieties R¹, R² and R³ are methyl or ethyl.

For the above mentioned alkali meta! nitrites it is preferred to use sodium nitrite or potassium nitrite.

t r

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If aluminum or an aluminum alloy with magnésium or other metals, which as sur'’ stable reaction with alkaline and acidic aqueous solutions is used for the RIS the aluminum or aluminum alloy can be used as a fine dispersed, pyrophoric material preferably having a particle size of about 1 pm or less and/or in the form of granules preferably having a particle size of about 0.1 to 5 mm, more preferably 1 to 2 mm. The aluminum and aluminum alloys may contain as a further métal also copper, gallium and/or indium.

If the température in the réaction zone of the oil well has reached about 250-300 °C a suspension of such granular aluminum or aluminum alloy in an organic solvent can be introduced into the oil well.

The aluminum is oxidized in an exothermic reaction to give aluminum oxide wherein 7 kg of Al produce a thermal energy of about 50,000 Kcal. For example, to increase the température of 1 kg of the productive layer formation by 100 °C a thermal energy of about 20 Kcal is to be provided, wherein increasing the température of 1 kg of petroleum by 100 ’C requires a thermal energy of about 50 Kcal.

The oxidation of aluminum results in formation of aluminum oxide particies which deposits in the newly formed fractures in the pay zone to hold them open so that the flow of oil towards the oil well and thus the oil extraction is further improved.

If aluminum or aluminum alloys with magnésium or other metals, which assure stable reaction with alkaline and acidic aqueous solutions, is used as the RIS, the chemical system may further comprise a solution or suspension of one or more of an acid or a solution or suspension of one or more of an alkali to be contacted with said aluminum or aluminum alloys.

If aluminum or its alloys are used and introduced into the oil well as a RIS it may be contacted after introduction with an acid or an alkali to initiate and maintain a thermochemical reaction producing heat and gases. For this the acid or alkali can be introduced into the oil well in form of a solution or suspension of one or more acids or of one or more alkalis. As such solutions aqueous solutions of hydrochloric acid (HCI) or sodium hydroxide (NaCH) can be mentioned, for instance.

For preparing the solution or suspension of the RIS any appropriate solvent may be used. In dependence ol the materials used as the RIS such appropriate solvent may be

water or an organic solvent selected from the group consisting of petrol, ligroin, white spirit, kerosene and naphtha. If, for instance, métal borohydrides or amînoboranes are used for the RIS water with a pH value >7 can be used as a solvent. For achteving such pH value ammonia or an alkali métal hydroxide can be added. If a material is used 5 which reacts with water one or more of the above organic solvents may be used.

At the beginning of a thermochemical treatment of an oil well RIS is usually used in the form of alkali métal borohydride in a quantity of about 5-7 % by mass or in the form of alkali métal nitrite in a quantity of about 30 % by mass with respect to the mass of TGEC injected into the oil well. After the chemical reactions are înitiated it is sufficient to use RIS in the form of ^alkali métal borohydride in a quantity of about 1 % by mass or in the form of alkali métal nitrite in a quantity of about 15-20 % by mass with respect to the mass of TGEC. With such chemical system it is possible to react up to several hundred tons of material per day in the pay zone of an oil réservoir, being about 50-100 times the amount of material which can be reacted per day with the Systems and methods reactîng the compositions in a batch wise manner.

Further, in contrast to the FOC used in the prior art, the above described TGEC does not contain an excess of oxygen and thus has no oxidizing character so that no explosive composition is created with the admixture of petroleum. The décomposition of 1 kg of TGEC results in emitting a quantity of heat of about 1000-3200 kcal.

With the illustrated chemical system it is possible to introduce TGEC and RIS into the oil well and to react these materials in the productive layer in an amount of up to about 100 tons per day and thus to produce more heat per time and to improve efficiency of the oil recovery process as it is possible to maintain a stable and continuous reaction by continuously pumping reactive materials into an oil well. With such chemical system a 25 large amount of heat and gases can already be produced with an amount of about 1 ton of reactive materials introduced into the oil well. To achieve a high efficiency of the oil recovery process it is, however, preferred to continuously introduce the reactive materials and thus to introduce at least about 10 tons/day, more preferably at least about 20 tons/day.

With the method and a pparatus according to the présent invention by using the above described compositions it becomes further possible to recover petroleum also from oil

réservoirs containing mainly high viscous petroleum which could not be efficîently recovered by using the methods known so far without introduction of extensive amounts of water.

The RIS or TGEC can additîonally contain one or more soluble métal salts of Mn, Fe, 5 Cr, Co, Ni or V. These metals are abie to catalyze an oxidatron ofthe petroleum, so that addîtional heat can be produced. These métal salts are contained in the RIS in an amount of not more than 10 % by mass with respect to the total mass ofthe RIS.

Especially preferred métal salts are Fe(NO₃)₃, Μη(ΝΟ₃)₂·6Η₂Ο, Mn(Sp₄)*6H2O, KMnO₄, K₂MnO₄, K₂CrO₄, Na₂CrO₄, K₂Cr₂O₇, Na₂Cr₂O₇, Co(NO₃)₃, NH₄VO₃, NaV0₃10 and KVO₃.

Following is given an overview of preferred ratios of the components contained in the TGEC and RIS which can be used with the method and apparatus according to the présent invention. The ratios are expressed as % by mass related to the combined mass of reagents contained in the TGEC and RIS, yet without the solvents used for 15 preparing the respective solutions or suspensions.

The TGEC compounds: 1. hydrazine nitrate i 2. 1,1-di C₂_6 alkyl hydrazine nitrates and 1,2-di C₂-6 alkyl hydrazine nitrates, such as 1,1-dimethyi hydrazine nitrate or 1,2-dimethyl hydrazine nitrate 3. guanidine nitrate 4. formamide nitric acid adduct 5. acetamide nitric acid adduct 6. acetonitrile nitric acid adduct 7. urea nitric acid adduct	in sum 30 - 70 % by mass
The TGEC compounds: 1. Mono-, di- and trie 2. Mono-, dî- and tri < Mono-, di- and trie	thanolamine nitrates '1-5 ^alky· amine nitrates, such as thylamine nitrates	if présent at least 10 % by mass

3. Polyethylene-polyamine polynitrate 4. C-(.₅ alkylidene dîamine mono- and dinitrate, such as Ethylènediamine mononitrate or Ethylènediamine dinitrate
The RIS compounds: 1. métal borohydrides MBH₄ 2. amînoboranes (R¹R²R³)N-BH3 3. dialkylaluminates MAIH₂R¹R² 4. aminoalanes (R¹R²R³)NAIH₃ 5. alkali métal nitrites MNO₂ 6. aluminum or alumtnum alloys with magnésium or other metals, which assure stable reaction with alkaline and acidic aqueous solutions.	1 - 10 % by mass 0.5-5 % by mass 1.5-7 % by mass 3 -10 % by mass 10-35 % by mass 0.3-70 % by mass
Further compounds to be added: Soluble salts of Mn, Fe, Cr, Co, Ni or V Ammonium nitrate, potassium nitrate, sodium nitrate, calcium nitrate Solutions or suspensions of acids (like aqueous solution of HCl) or alkalis (like aqueous solution of NaOH)	1 - 4 % by mass 0-50 % by mass

The TGEC and RIS can be pumped into the oil réservoir with a rate of about 4-8 liters per second.

In the preferred embodiment shown in Fig. 1 the second and third fluid passages hâve different sectional areas of flow such that the second fluid 16 passage allows higher 5 flow rates than the third fluid passage 15. As the TGEC is usually used in a higher amount than the RIS it is preferred to inject the TGEC 17 into the second fluid passage and to inject the RIS 18 into the third fluid passage 15. The injection of the two compositions 17 and 18 can be achieved by using suitable pumps.

i

When reaching the pay zone 2 the two compositions 17 and 18 are mixed as the distal end section of the outer tubing 9 is perforated to provide openings 10 for allowing fluid exchange between the second and third fluid passages. This mixing initiâtes the chemical reactions and as a resuit of continuously pumping down the TGEC 17 and 5 RIS 18 the reacting admîxture ks transferred through the openings 4 in the casing 1 into the upper wells 11 of the pairs of horizontal wells and is thus distributed in the oil réservoir 3.

The chemical réactions produce large amounts of heat and gases. This causes a température increase in the treated area of the oil réservoir what reduces the viscosity 10 of the oil and additionally produces fractures in the formation so that the extraction of oil is further improved. As a resuit a liquid can be collected tn the lower wells 12 of the pairs of horizontal wells and can be extracted through the openings 5 in the casing 1 into the oil well and through the first fluid passage 14 up to the surface. The collected and extracted liquid 19 comprises oil and dépendent on the conditions présent in the oil 15 well also other components. lf the method according to the présent invention is used in water-flooded oil réservoirs the collected and extracted liquid 19 will comprise large amounts of water. In the présent application this liquid will be designated as an oil or oil containing mixture 19.

In contrast to the SAGD method where mainly gravity is the driving force for the 20 collection of oil (usually a mixture of oil and water) in the lower wells the method according to the présent invention additionally uses a pressure increase in the treated area of the oil réservoir for the collection and extraction of the oil or oil containing mixture 19. This increase of pressure is caused by the continuous pumping of liquids 17 and 18 into the oil réservoir and by the initiated reactions producing large amounts of 25 hot gases. The pressure différence between the upper and lower wells of the pairs of horizontal wells may vary from several atmosphères to several tens of atmosphères. This allows a more efficient extraction of oil. The higher pressure values achieved with the method according to the présent invention further causes more crack formations than in the SAGD method and thus further improves oil extraction. The formed cracks will reach the point of pressure relief, i.e. the lower wells 12 where the pressure is decreased by the continuous and intensive extracting of the oil or oil containing mixture 19. Thus, the extraction of oil îs further improved. The improved capability of

producing and collecting extractabie oil or an oil containing mixture is achieved with the method according to the présent invention along the entire length of the horizontal wells (in the présent case about 200 m),

A further advantage of the method according to the présent invention compared to the 5 SAGD method is that much lower amounts of water are întroduced into the oil réservoir.

In the following is provided a doser look onto the method according to the présent invention.

i”

One of the control parameters of the method according to the présent invention are the températures in the oil well above and below the packer 8 where the température 10 sensors 13 are installed. Depending on the température values determined with these température sensors 13 the flow amounts of the injected compositions TGEC and RIS may be regulated.

i

One upper température limit is the maximum température allowed for the packer 8 and the casing 1 of the oil well which usually at least partly consiste of cernent In the 15 following illustration a maximum température of about 300 °C is assumed for the packer 8 and the cernent used for the casing 1 of the oii well. However, it should be noted that also materials can be used for the packer 8 and the casing 1 allowing higher maximum températures so that the method and apparatus of the présent invention are not limited to the aspects mentîoned in the following illustration.

In a first stage the oil réservoir is heated by reacting TGEC and RIS to reach a température at the température sensor 13 below the packer of about 250-280 ^eC. At such température TGEC can react/decompose producing heat and gases without further supply of an initiator (RIS). At this stage the Injection of RIS can be reduced or even suspended. This allows a cost efficient process control as the components ofthe RIS are usually relatively expensive compared to the components used for the TGEC.

In principal, the supply of RIS can be reduced or suspended if the température of the reaction reaches a value of 200 °C or higher. It is then sufficient to supply only TGEC to maintain a stable réaction in the pay zone of the oil réservoir and the TGEC may be supplied through the second and/or third fluid passages 16 and 15.

If a stable température of about 250-280 C îs obtained in the horizontal wells the method according to the présent invention may be varied by also reduce or even suspend the supply of TGEC and by introducing air or any other cheap oxidant supply into the oil réservoir. At that stage a controlled combustion of oil îs possible, a so called 5 low-temperature oil combustion with a reaction température of about 300 °C and with a heat production Q of about 40 MJ per kilogram of burned oil.

Following is given an estimation of the percentage of oil to be burned to heat up the material (like rock) containing the oil to be extracted at the stage where only a reiatively cheap oxidant is supplied to maintain the reaction in the oil réservoir.

As an example of such cheap oxidant potassium nitrate is assumed. About 2-3 kg of potassium nitrate are required to oxidize 1 kg of oil. With the following formula (1) the mass M of heated collecter having a porousness of about 20% is calculated:

Q = C · M ΔΤ (1) wherein:

Q = amount of heat produced,

C = spécifie heat capacity of collecter with oil,

M = mass of collecter with oil,

Δ T = température increase.

The collecter is the material of the oil réservoir containing the oil in its pores.

With a spécifie heat capacity C of 1 kJ/(kg-K) and a température increase Δ T of 100 K and an amount of heat Q of 40 MJ (produced per kg of burned oil) a mass of 400 kg can be calculated. This means, for heating up 400 kg of collecter by 100 K it is required to oxidize 1 kg of oil in the réservoir.

The density of the collecter material (e.g. rock) can be assumed to be about 2.5 kg/l so that this resuit in a volume V of about 160 I of rock having a mass of about 400 kg that can be heated with 1 kg of oil.

that the amount of oil in the pores of the calculated collecter

If ît is further assumed volume is about 32 literls corresponding to about 28 kg of oil. That is, 1 kg of oil îs to be burned to heat up 400 kg of rock comprising 28 kg of oil. Therefore only about 4 % of

t ’ t » i I

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I J ï j i i j .} i the oil contained in the treated area is to be burned to extract oil from this treated oil réservoir.

The price for 2 - 3 kg of potassium nitrate is about 16-20 Russian rubles. This amount of potassium nitrate is necessary to produce about 40 MJ. Therefore, to obtain 1 MJ of heat in the oil réservoir using potassium nitrate, it is required to spend about 0.4 - 0.5 Russian rubles for chemical reagents.

When comparing the costs of the method according to the présent invention with the costs of the SAGD method it can be summarized that the cost for producing hot water vapor to be pumped from surface down into the oil réservoir to supply 1 MJ of heat to the réservoir is abouti 10 times bigger than when using the method according to the présent invention.

One reason for such significant différence is that in the SAGD method the oil or bitumen burned for producing the heat for the thermal treatment is burned at the surface whereas in the présent method the heat is produced directly where it is used for the thermal treatment, i.e. it is produced down in the oil réservoir.

In Fig. 2 are shown flow directions used in a spécifie embodiment of the method of thermally treating an oil réservoir according to the présent invention. In this method, when the above mentioned stage where only one fluid like the TGEC or any other cheap oxidant can be supplied to maintain a constant reaction in the pay zone of the oil réservoir need to be .supplied, such fluid can be introduced through the first fluid passage 14, that is through the inner tubing 6, and îs then forwarded through the openings 5 and the lower well 12 to the oil réservoir. The oil or oil containing mixture 19 is then extracted through the upper wells 11, the openings 4 and through one or both of the second and third fluid passages 16 and 15. Such reversed flow direction regarding the oil in the oil réservoir is possible as the main driving force in the présent method is the pressure différence caused by pumping in the fluid and by the production of large amounts of heat and gases.

With such method a m uch greater sectional area can be used for the extraction of the oil or oil containing mixture, i.e. the sectional areas of the second and third fluid passages, as compared to the embodiment shown in Fig. 1. Further, thefluid introduced into the first fluid passage 14 can be used to cool the packer 8.

In the following is provided an estimation showing that the method of thermally treating an oil réservoir according to the présent invention can be successfully applied at oil 5 réservoirs being intensively water-flooded.

It is assumed that in such heavily water-flooded oil réservoir the pores contain about 90 % of water and about 10 % of oil. The spécifie heat capacity of water is 4.2 kJ/(kg-K).

On basis of the above formula (1) it can be calculated that in such case the oxidation (burning) of 1 kg of oil will cause a température increase of about 80 °C for 400 kg of 10 rock, the pores of which contain 32 liters of fluid (90% water and 10% oil). As a resuit of the heating the viscosity of the fluid (water + oil) will be 4-5 times reduced, the fluid will flow from the réservoir into the oil well and then will be pumped outto the surface.

Thus, it can be summarized that for extracting 3.2 liter of oil it is necessary to burn 1 liter of oil being about one third ofthe oil. With the methods known so far itwas notregarded 15 possible to achieve a cost efficient extraction of oil from such heavily water-flooded oil réservoirs.

With the apparatus and method according to the présent invention it is further possible to introduce fluids for initiating and maintaining a thermal treatment of the oil réservoir while simultaneously extracting the oil.

Claims

Claims

1. A method of continuously thermally treating an oil réservoir comprising the steps of;

5 - initiating a chemical reaction producing heat and gases for thermally treating the oil réservoir to obtain extractable oil or an extractable oil containing mixture by separately introducing into an oil well of said oil réservoir a first and a second composition through separated fluid passages provided in said oil well and

I contacting the first Από second compositions in the pay zone ofthe oil réservoir,

10 - maintaining the chemical reaction in the oil réservoir by continuing the introduction of at least one of said first and second compositions; and

- extracting the résultant oil or oil containing mixture during said step of maintaining the chemical reaction through a fluid passage provided in said oil well, wherein inside said oil well the fluid passage used for extracting the oil or oil 15 containing mixture has no fluid connection with any fluid passage used for continuing the introduction of at least one of said first and second compositions to maintain the chemical reaction.
2. The method according to claim 1, wherein inside said oil well the separated fluid 20 passages used for introducing the first and second compositions hâve no fluid connection, the first and second compositions are passed through openings in the casing of the oil well allowing fluid exchange between the oil well and the oil réservoir, and thé first and second compositions are contacted outside of the casing of said or! well to initiate the chemical reaction.
3.

end section of each of the one or more tubings is located in the well, and by arranging a sealing device in said oil well such that

The method according to claim 2, wherein the separated fluid passages used for introducing the first and second compositions and the fluid passage used for extracting the oil or oil containing mixture are provided in said oil well by arranging one or more tubings each comprising at least one opening in its distal end section such that the distal pay zone of the oil the openings in the casing of the oil well allowing fluid exchange between the oil well and the oil réservoir are located above and below the sealing device and such ί

that one tubing extends through the sealing device, so that the at least one opening in the distal end section of this tubing is located below the sealing device, and the sealing device seals the space between the outside of the tubing extending through the sealing device and the inside of the casing of the oil well.
4. The method according to claim 1, wherein the separated fluid passages used for introducing the first and second compositions hâve fluid connection in the pay zone of the oil well, the first and second compositions are contacted în the pay zone of the oil well, and wherein the method further comprises the step of

I

- transferring the' chemical reaction into the oil réservoir by passing the contacted compositions through openings in the casing of the oil well allowing fluid exchange between the oil well and the oil réservoir.
5. The method according to claim 4, wherein the separated fluid passages used for introducing the first and second compositions and the fluid passage used for extracting the oil or oil containing mixture are provided in said oil well by arranging two tubings each comprising at least one opening in its distal end section such that the distal end section of each tubing is located in the pay zone of the oil well, and by arranging a sealing device in said oil well such that the openings in the casing of i

the oil well allowing fluid exchange between the oil well and the oil réservoir are located above and below the sealing device and such that one of the two tubings extends through the sealing device so that the at least one opening in the distal end section of this tubing is located below the sealing device and the at least one opening in the distal end section of the other tubing is located above the sealing device and the sealing device seals the space between the outside of the tubing extending through (the sealing device and the inside of the casing ofthe oîl well.
6.

The method according to claim 5, wherein the two tubings are arranged coaxially defining an inner and an outer tubing, the inner tubing extending through the sealing device ancl defining a first fluid passage, a second fluid passage is defined by an annular space between the outside ofthe outer tubing and the inside ofthe casing of the oil weli and a third fluid passage is defined by an annular space between the outsic'e ofthe innertubing and the inside ofthe outertubing.
7. The method according to claim 6, wherein in the step of initiating the chemical reaction one of the first and second compositions is introduced into the oil well through one of the second and third fluid passages and the other one of the first

5 and second compositions is introduced into the oil well through the other one of the second and third fluid passages and wherein in the step of extracting the résultant oil or oil containing mixture it is extracted through the first fluid passage.
8. The method according to any of daims 3 and 5 to 7, wherein the sealing device is a 10 packer.
9. The method according to any of daims 3 and 5 to 8, wherein the openings in the casing of the oil well are not located in the area where the sealing device is installed.
10. The method according to any of daims 3 and 5 to 9, wherein at least one pair of horizontal wells, consisting of an upper and a lower well being provided, wherein the upper and lower wells of each pair of horizontal wells are arranged substantially parallel to each other or are arranged to approach each other and wherein the

20 upper ones of the horizontal wells are in fluid connection with that part of the oil well located above the sealing device and the lower ones of the horizontal wells are in fluid connection with that part of the oil well located below the sealing device.
11. The method according to any of the previous daims, wherein the first composition

25 is a thermal gas emitting composition (TGEC) containing chemical compounds producing heat and gases after the chemical reaction is initiated and wherein the second composition is a reaction initiator stabilizer (RIS) containing chemical compounds initiating said chemical reaction when contacting the TGEC.

30
12. The method according to any of the previous daims, wherein during the step of maintaining the chemical reaction the introduction of at least one of the first or second compositions is suspended and the introduction ofthe other one ofthe first i

i j ï i i j

ί i j i i

I i

j j or second compositions is continued when a stable reaction in the pay zone is achieved.
13. The method according to any of claims 6 to 12, wherein the flow directions of the 5 continuously introduced composition and the extracted oil or oil containing mixture in the oil réservoir are reversed by introducing said composition through the first fluid passage and extractîng the oil or oil containing mixture through the second and/or third fluid passages.

10
14. The method according to any of the previous claims, wherein the introduction of the first and second compositions is suspended and only air is introduced through one of the fluid passage to maintain the chemical réaction in the oil réservoir when an ïn-situ combustion ofthe oil in the pay zone ofthe oil réservoir has started.
15 15. The method according to any of claims 3 and 5 to 14, wherein the température above and/or below the sealing device is measured.
16. The method according to any of the previous claims, wherein oil the oil réservoir is subjected a hydrocracking process.
17. An apparatus for thermally treating an oil réservoir by separately introducing a first and a second composition into an oii well and contacting the first and second compositions in a pay zone of the oil réservoir to initiate a chemical reaction producing heat and gases, wherein in the pay zone a casing of the oil well comprises openings to allow fluid exchange between the oil well and the oil réservoir, said apparatus comprising:

- a sealing device being positioned in the pay zone of said oil réservoir, such that said openings in the casing of the oil well are located above and below the sealing device;

- a tubing comprising at least one opening in its distal end section being arranged in the oil well suéh that it is passed through the sealing device so that the at least one opening is located below the sealing device and the sealing device seals the t

ί i

j 37 j

i j résultant annular space between the outside of the tubing and the inside of the ! casing of the oil well, ] wherein the inside of the tubing defines a first fluid passage and the inside of the t \ : casing of the oil well above the sealing device defines a second fluid passage.
18. The apparatus according to claim 17, wherein in addition to the tubing passed through the sealing device, the first tubing, the apparatus further comprises:

- a second tubing comprising at least one opening in its distal end section being i arranged in the oil well such that the distal end and the at least one opening of

I ! 10 the second tubing is positioned in the pay zone above the sealing device

I wherein the inside of the second tubing defines a third fluid passage and the j apparatus allows fluid exchange between the second and third fluid passages in j the pay zone of the oil well.

i

15
19. The apparatus according to claim 17 or 18, wherein the openings in the casing of i

I the oil well are not located in the area where the sealing device is installed.

i
20. The apparatus according to any of claims 17 to 19, wherein the sealing device is a packer.
21. The apparatus according to any of claims 18 to 20, wherein the first and second tubîngs are arranged coaxially and the second tubing as an outer tubing encloses the first tubing as an inner tubing.

25
22. The apparatus according to any of claims 17 to 21, further comprising at least one pair of horizontal wells, consisting of an upper and a lower well, wherein the upper and lower wells of each pair of horizontal wells are arranged substantially paraIle! to each other or are arranged to approach each other and wherein the upper ones of the horizontal wells are in fluid connection with that part of the oil well located

30 above the sealing device and the lower ones of the horizontal wells are in fluid connection with that part ofthe oil well located below the sealing device.

J ί l

Ί i

1 J ί

J ί ί J
23. The apparatus according to any of claims 17 to 22. further comprising at least one température sensor to measure the température above and/or below the sealing device.