EP0075515B1 - Method and installation for oil recovery by in situ combustion - Google Patents

Method and installation for oil recovery by in situ combustion Download PDF

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Publication number
EP0075515B1
EP0075515B1 EP82401680A EP82401680A EP0075515B1 EP 0075515 B1 EP0075515 B1 EP 0075515B1 EP 82401680 A EP82401680 A EP 82401680A EP 82401680 A EP82401680 A EP 82401680A EP 0075515 B1 EP0075515 B1 EP 0075515B1
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EP
European Patent Office
Prior art keywords
oxygen
conduit
injection
flame
combustion
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EP82401680A
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German (de)
French (fr)
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EP0075515A1 (en
Inventor
Guy Savard
Robert Gum Hong Lee
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Air Liquide Canada Inc
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Air Liquide Canada Inc
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Priority to AT82401680T priority Critical patent/ATE16624T1/en
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
    • E21B41/0078—Nozzles used in boreholes
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/243—Combustion in situ

Definitions

  • the invention relates to the recovery of petroleum by in situ combustion from deposits located in underground sedimentary formations.
  • Process regulation is essential and complex. To monitor the advance of the combustion front and to predict operational problems, basic data must be obtained and analyzed, in particular the air speed and its pressure, the injection rate of the water, gas evacuation speed in different wells, casing pressures on production wells, gas analysis, oil and water production rate, temperature measurements. Among the other data, which we need more rarely, but on a regular basis, we must mention the density and viscosity of the oil leaving each well, the determination of chlorine in water, the pH of water, the pressure drop of the injectors.
  • the first group of data makes it possible to make calculations on the movement of the forehead, the efficiency of combustion and the use of oxygen.
  • the second set of data makes it possible to make corrections to the calculated data and to prepare for the arrival of the thermal front in a production well.
  • Patent FR-A-1 473 669 discloses a process for recovering petroleum by in situ combustion with the possibility of optionally resorting to the combustion of petroleum from the deposit by an activated combustion gas, such as composed of carbon dioxide, water vapor and enriched with large quantities of oxygen.
  • the invention proposed by this application relates to a process for recovering petroleum by combustion, in situ from a sedimentary formation constituting an oil deposit according to which a gas supporting combustion is introduced such as air or air and water or a gas enriched in oxygen or pure oxygen, by at least one injection well extending from the surface and crossing overburden up to the interior of the deposit, in an injection zone so as to burn part of the oil by creating a flame front, which is advanced to a certain point, and to cause the flow, through a treatment zone, of fluids whose petroleum, to a number of production wells through which fluids are extracted.
  • a gas supporting combustion such as air or air and water or a gas enriched in oxygen or pure oxygen
  • the method according to this proposed invention is characterized in that, when the gas supporting combustion is oxygen, it is introduced by a separate conduit separate from the injection well, this conduit leaving the surface, passing through the dead - land and arriving separately in the deposit near the injection well.
  • the installation for applying this method is characterized in that it also comprises at least one oxygen conduit distinct and separate from the injection well, starting from the surface, passing through the overburden and arriving in the area of treatment at a point located at a distance from the injection well much less than the distance between an injection well and a production well, said conduit being equipped with means for introducing oxygen into the formation.
  • in situ combustion is regulated by the strategic placement of one or more fluid conduits, starting from the surface and crossing the overburden to reach the treatment zone, at a point located at a certain distance from the injection well, the regulating fluid being introduced into the deposit via said conduit, independently of the fluid injected into the injection well.
  • the control fluid introduced is oxygen, serving as auxiliary combustion gas and replacing the injection of a gas supporting combustion such as air in the well. injection.
  • the fluid conduit is located near the injection well, but it is separated by a short distance, so as to allow the establishment, on the surface, of a separate regulation equipment.
  • oxygen and water can be introduced alternately, the oxygen being sent through the fluid conduit and the water through the injection well.
  • a regulating fluid conduit is placed in this zone, and oxygen is introduced to accelerate the flame front and improve the scanning.
  • a regulation duct in this area and introduce appropriate fluids to slow down the flame front and improve the sweep .
  • the invention is preferably used with a conventional in situ combustion model, preferably a multi-well mesh type well layout arrangement, in which air and water are introduced into a well. injection, which leaves the surface and crosses overburden to reach the oil field,. in an injection zone, under conditions leading to the combustion of part of the oil and the flow of part of the oil through a treatment zone to at least one production well, disposed at a certain distance from the injection well.
  • an oxygen introduction conduit is placed strategically, extending from the surface and crossing the overburden to the oil deposit, in the treatment zone.
  • the oxygen conduit is placed near the injection well, but at a sufficient distance so that the equipment for regulating oxygen at the surface is distinct from the equipment. relatively complex regulator at the head of the injection well.
  • the separate oxygen conduit may be approximately 3 to 4.6 m from the injection well.
  • air and water in a representative treatment cycle, are introduced alternately into the injection well to advance the flame front to a certain point.
  • the air injection is then stopped, then the injection well is used to introduce essentially only water.
  • the air is replaced by oxygen, which is introduced into the deposit by the oxygen pipe to continue the advance of the flame front.
  • the invention also relates to a method of recovering petroleum from an underground sedimentary formation by the wet combustion process, method according to which there is an injection well, equipped to introduce air, or l water, or both, under conditions ensuring the combustion of part of the oil by air, and a certain number of production wells, arranged at a certain distance from the injection well, towards which one is s' drain the oil through a processing area.
  • a separate oxygen conduit starts from the surface, passes through the overburden and arrives in the formation treatment area, at a point located at a relatively short distance from the injection well.
  • the injection well is fitted with conventional, relatively complex air and water control equipment. The fact that the oxygen pipe is separated considerably simplifies the surface control system for both the air injection well and the oxygen pipe.
  • FIG. 1 shows a layout arrangement of “three-mesh” wells, comprising three injection wells A, A 1 and A 2 .
  • a series of production wells B are placed, for example, symmetrically with respect to the injection well A, at a certain distance from the latter. Air is injected through the injection well A into the underground formation in an injection area, to allow combustion of the oil.
  • the production wells B located in the production areas are equipped with pumping means so that, when combustion begins in the vicinity of injection well A, the fluids, which include combustion products, water, steam and petroleum, are drawn from the injection zone in the vicinity of well A, through a treatment zone, to reach a production zone at well B.
  • a flame front is produced in the treatment zone between the injection zone and the production zone.
  • a cycle is carried out according to which air is introduced for two days, then water for one day, and this cycle is repeated continuously for several months or several years.
  • the injection well A is located in the center of the mesh and the production wells B are at the corners of the hexagon, at a distance of approximately 122 m.
  • the oil formation can be several tens to several hundred meters from the surface, for example 610 m.
  • the thickness of the formation can range from a minimum of 0.3 m to more than 30 m. For example, most of the oil found in the Lloydminister area occurs in formations about 6 m thick. Exploitation can continue for several months before recovery begins in the production wells of oil from on-site combustion.
  • an oxygen conduit C starts from the surface, crosses overburden and arrives in the oil deposit, in the treatment zone, at a relatively short distance from the injection well A.
  • the oxygen duct C can be 4.6 m from the injection well.
  • the oxygen duct be located at a certain distance from the injection well so as to allow independent realization l 'exploitation of both. In all cases, a fluid must constantly flow through the oxygen pipe and through the injection well. According to the invention, once the flame front has advanced in the treatment zone, to the desired point, the injection of air and water is stopped in the injection well A and the introduction of oxygen in the oxygen line, alternating with the injection of water into the injection well.
  • the production well pumps are turned on and a certain amount of oil is extracted before in situ combustion.
  • the flame can then be lit, for example by lowering a gas burner into the injection well, by sending air or natural gas to promote combustion.
  • the burner can either remain in place or be recovered, depending on the circumstances.
  • Figure 2 is a theoretical view of what happens during in situ wet combustion.
  • This figure is a vertical section through an underground sedimentary formation containing petroleum, also known as an oil deposit, which has undergone wet combustion.
  • the formation consists of an injection zone surrounding the injection well A, intended to introduce air to maintain the combustion of petroleum in the deposit and water to modify the heat transfer according to the method of wet combustion, and a production area surrounding the production well B, intended to extract the fluids pushed forward by the flame front. Between these two zones is a treatment zone, and the different materials making up this zone, at a particular stage of operation, are indicated by legends in the figure.
  • a gas injection tube C is placed strategically in the treatment zone to introduce oxygen intended to promote combustion or to regulate the advance of the flame front, as will be described. in detail below.
  • an oxygen conduit so that it penetrates into the burned region, then introduce oxygen to promote combustion, oxygen which will replace the air injected into well A.
  • a representative method could include two days of oxygen injection and one day of water injection, during the entire treatment period, which can last up to several years.
  • the injection well A is approximately 125 m (a) from the production well B.
  • the thickness of the sedimentary formation is between 0.3 and 30 m, and it can be at a depth of about 610 m, being covered by overburden in which there may be separate additional sedimentary oil formations by rock.
  • Oxygen line C should be placed approximately 3.0 to 4.6 m from the injection well.
  • FIG. 4 represents an installation according to the invention, in vertical section, in an underground formation.
  • the reference A designates an air-water injection well.
  • the well consists of a borehole, lined with a steel casing 15, which starts from the surface, descends through the overburden and arrives in the underground sedimentary formation in which the oil deposit is found.
  • the borehole, outside the casing 15, is suitably filled with standard filling materials which form an envelope 17 internally lining the borehole.
  • the casing 17 is lined with perforations 19 to allow the fluids to exit the borehole.
  • the casing 15 is lined with a casing shoe 21.
  • a lined tube 23 starts from a wellhead 25, located on the surface, to arrive at a “recoverable packer 26, the lower end of which is centered in the envelope 17.
  • An air and water pipe 27 starts from an injection unit, and can send air head or pressurized water to the wellhead 25.
  • Gate valves 29 and 31 are provided, as well as check valves 33 and full-flow valves 35 and 36 for regulating the flow of air or water to the tube 23.
  • the apparatuses placed above from well A are frequently called "Christmas tree".
  • an oxygen conduit C is placed, formed by a borehole housing a steel casing 37 and a concrete casing 36 filling the space between the borehole and the casing.
  • An oxygen tube 41 which extends beyond the casing 37 and passes through a recoverable "packer” 43 to come out from below, extends into the borehole.
  • the oxygen tube starts from the surface, crosses the overburden and enters the underground sedimentary formation, in the treatment zone located between the injection well A and the production wells.
  • oxygen 45 starts from a pressurized oxygen source, passes through a full-flow valve 47 and arrives at the oxygen tube 41. Since only oxygen is introduced into the conduit C, the tube 41 does not need to be made of an expensive stainless steel such as that which is necessary for the injection well A where the presence of water causes corrosion. In addition, only relatively simple oxygen control equipment is required.
  • the lower end of the oxygen tube has a safety injector D, which is described in detail below.
  • Figure 5 is an enlarged partial vertical section of the bottom of the oxygen conduit.
  • the end of the tube 41 carries an external thread intended to receive a cylindrical connector member 51 over its entire length.
  • the member 51 has an internal bore, which has a cylindrical part 53, enlarged and tapped, meshing with the end of the pipe 41.
  • the bore narrows into a frustoconical part 54 to arrive at a groove 55, which defines the inlet of a throttled central cylindrical passage 57.
  • the lower end of the element 51 has an annular recess 58, which receives the end of a pipe 59 made of nickel alloy.
  • the pipe 59 and the connector member 51 are welded to each other at 61.
  • a tip element 63 is mounted at the lower end of the pipe 59.
  • the element 63 has a cylindrical body over its entire length, with an upper annular recess 60 receiving the end of the pipe 59.
  • the element 63 and the pipe 59 are welded to each other at 65.
  • the body of the element 63 has a central passage, which has an upper frustoconical part 67 narrowing to a short cylindrical groove 69, then widening in part frustoconical 71 ending in a shorter and wider frustoconical part 73.
  • Parts 51 and 63 are made of a non-fissurable nickel alloy.
  • the dimensions of the oxygen pipe depend to a large extent on the force required to pull the packer.
  • the smallest diameter would be approximately 51 mm, the largest of 254 mm, 178 mm corresponding to a practical intermediate diameter. This diameter must be sufficient to allow the introduction of cement.
  • a tube with a diameter of 51 mm is sufficient.
  • the maximum diameter corresponds to a pipe which can be part of the well itself and still be cemented.
  • the pressure is generally the same as that of air, and is between 28 and 70 kg / cm 2 .
  • An empirical calculation method calculates the pressure, which will be about half a pound for 30 cm deep. The specific pressure depends on both the depth and the porosity of the formation.
  • the boreholes can have any diameter.
  • a plunger is provided to expel the cement.
  • a unit on the surface supplies oxygen at low pressure at a rate of at least 18 tonnes per day, and compresses it to a pressure of 28 to 70 kg / cm 2.
  • the oxygen pipe must be equipped with to allow rapid replacement of oxygen with other fluids.
  • At least part of the passage, through which the oxygen-containing gas is introduced, must be throttled so as to have a diameter such that the speed of the gas is greater than the maximum speed of the flame likely to to occur.
  • This injector has throttled grooves, arranged in series, followed by an outlet opening of increasing diameter intended to allow the expansion of the gas. in order to reduce its speed and minimize the sanding effect inside the casing.
  • the safety injector as shown can be used not only for oxygen, but also for oxygen mixed with another fluid having desirable properties for the in situ combustion of a hydrocarbon deposit, for example CO 2 , N 2 air, H 2 0, etc ...
  • the tube downstream of the packer must resist cracking in contact with oxygen, heat, corrosion and erosion. Besides this, the tube must have maximum security. In an oil formation, for example, there may be disturbances and fuel seepage inside and around the injection tube. '
  • a hydrocarbon can burn in the presence of air giving a flame having a certain speed. If the same hydrocarbon burns with oxygen, its flame propagation rate may be much higher.
  • the methane-air mixture gives a maximum flame propagation speed of 0.46 m / s, while the methane-oxygen flame has a maximum propagation speed of 4.57 m / s.
  • the hydrogen-air mixture has a maximum flame propagation speed of 3 m / s, while the hydrogen-oxygen flame has a maximum flame propagation speed of 14 m / s.
  • the flame propagation speed H 2 -0 2 is approximately 19.81 m / s under a pressure of 21 kg / cm 2 , approximately 28.35 m / s under a pressure of 63 kg / cm 2 , and 30.48 m / s under a pressure of 105 kg / cm 2.
  • a nozzle can be installed at the outlet of the tube, to accelerate the oxidizing gas to a speed greater than the maximum speed of propagation of the flame, to avoid a flashback in the tube.
  • one or more other nozzles can be placed upstream of the outlet nozzle, to resist any backfire.
  • the flow rate of the oxidizing gas through the tube (which has sufficient mechanical strength) is high enough for the speed of the gas to be greater than the maximum speed of propagation of the flame likely to be at the level of the well. injection, it is not necessary to use nozzles accelerating the oxidizing gas.
  • nozzles can be in the form of a straight bore, or they can be of a venturi type, such as that shown in FIG. 5, intended to avoid cracks in contact with oxygen which would reduce the resistance mechanical, and to prevent any backfire in the tube.
  • it is relatively resistant to corrosion.
  • a tube with a diameter of 50.8 mm, nomenclature 80 is used (that is to say a tube having an external diameter of 60.31 mm and an internal diameter of 49.21 mm, the spacing of its walls being 5.5 mm), for its mechanical strength, because it has a free length of 550 m.
  • a venturi nozzle is placed at the bottom, at the injector outlet. As additional security, another nozzle is placed upstream.
  • the injector is designed, for example, for an oxygen flow rate of 84,950 m 3 / day under a pressure of 31.5 kg / cm 2 at ambient temperature.
  • the groove of the venturi nozzle has a diameter of about 11.4 mm, which allows the oxidizing gas to '' have a speed of 30.5 m / s, a speed which is higher than any flame propagation speed that can be encountered at the bottom of an injection well or an oxygen pipe.
  • the outlet orifice (s) of the injector may be in the form of one or more holes. Each hole must be dimensioned so as to give the oxidizing gas injected a speed greater than the maximum flame propagation speed that can be encountered.
  • the downhole injector can only be used for oxidizing gas or a mixture of gases, or it can be used alternately with water injection, intermittently.
  • it can be used for the oxidizing gas and the mixture of gases with the other injected fluids (for example H 2 0 and / or air), injected into the formation by another injection well.
  • the other injected fluids for example H 2 0 and / or air
  • water, air or other fluids need not be free of hydrocarbons (e.g. petroleum).
  • all the fluids intended for the injection well must be injected into the formation using only this single injector, all the fluids must be free of petroleum, in particular when the oxidizing gas is oxygen.
  • the invention is characterized by the introduction, defined in a strategic manner, of oxygen instead of air as a gas promoting combustion; by oxygen is meant here an oxygen having a volume concentration of 90% (under normal conditions), or more, and preferably a concentration of at least 99.5%.
  • the theoretical scanning efficiency which can be obtained with oxygen is about 45 to 50%, which is considerably lower than when using air. Indeed, there is less nitrogen ballast and a higher partial pressure of C0 2 in the oxygen combined with the coke. There is more C0 2 in the oil, which decreases its viscosity, increases the production rate and decreases the entrainment of nitrogen in the production well. It is difficult to dissolve the emulsion that forms at the production well when using air as the combustion promoting gas. When using oxygen, the emulsion formed is easier to dissolve.
  • the product leaving the production well, when using air contains petroleum and sand, water, gas, C0 2 and nitrogen, a little methane, a little hydrogen and a little sulfur.
  • the tube must simply have sufficient mechanical strength to withstand the forces applied during its installation, and its outlet orifice must be suitably shaped so as to withstand the temperatures to which it may be exposed.
  • the tube When, for example, the duct is installed in front of the flame front, the tube can be protected by a jacket of water or thick cement. There must always be a flow of fluid through the tube, in the same way as in the injection well, to avoid any backflow in the conduit.
  • the extreme flexibility of using a pipe of this type for injecting oxygen is clear from the description above.
  • conduits can go up to levels below which water is injected into the injection well in the case of wet combustion.
  • oxygen can be introduced near the bottom of the oil deposit or at intermediate points.

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Abstract

Enhanced recovery of oil from subterranean sedimentary formations by an in-situ combustion method employing a pattern of an injection well and several production wells, spaced-apart by a treatment zone. Combustion is controlled by placing at least one fluid conduit in a treatment zone and introducing a control fluid through it to modify the flame front. Oxygen may be introduced to take over from combustion air initially introduced through the injection well, to sustain combustion and advance the flame front. Water may be injected through the injection well, alternating with the oxygen through the control conduit to continue a wet combustion method started with air. The strategic placing of control conduits and the introduction of appropriate fluids may be employed to improve the sweep geometry by advancing the flame front or retarding it, or invading areas behind it. Safety means is provided for introducing the oxygen at a velocity greater than the maximum flame velocity encountered in the flame front.

Description

L'invention concerne la récupération du pétrole par combustion in situ à partir de gisements se trouvant dans des formations sédimentaires souterraines.The invention relates to the recovery of petroleum by in situ combustion from deposits located in underground sedimentary formations.

Des procédés de récupération du pétrole par combustion in situ à partir de formations souterraines sont décrits dans les textes publiés suivants : « The Petroleum Reservoir ·, cours de formation accélérée de Selley, Anstey et Dono- hue, International Human Resources Develop- ment Corporation, Boston, Mass, 1981 ; le manuel « Enhanced Recovery of Residual and Heavy Oils », 2e édition, sous la direction de M. M. Schumacher, édité par Noyes Data Corporation, Parkridge, New Jersey, Etats-Unis, 1980 ; « Heavy Oil Recovery by In Situ Combustion par le Dr Phillip D. White, Texas Petroleum Engineers Inc., Dallas, Texas, communication présentée par la S.P.E., Section Dallas, séminaire de formation continue, printemps 1980 ; « Twenty Years Ope- ration of an In Situ Combustion Project », par Jenkins et Kirkpatrick, Petroleum Society of C.I.M., 1978 ; et un article intitulé « ln Situ Combustion Process - Results of a Five-Well Field Experiment, Southern Oklahoma,., par Moss, White et McNeil, Magnolia Petroleum Company, Dallas, Society of Petroleum Engineers of AIME, présenté lors de la 33e Réunion Annuelle d'Automne de la Société, Houston, du 5 au 8 octobre 1958.Processes for recovering petroleum by in situ combustion from underground formations are described in the following published texts: “The Petroleum Reservoir ·, accelerated training course by Selley, Anstey and Donohue, International Human Resources Development Corporation, Boston, Mass, 1981; the manual "Enhanced Recovery of Residual and Heavy Oils", 2 nd edition, edited by MM Schumacher, edited by Noyes Data Corporation, Parkridge, New Jersey, USA, 1980; “Heavy Oil Recovery by In Situ Combustion by Dr. Phillip D. White, Texas Petroleum Engineers Inc., Dallas, Texas, paper presented by SPE, Dallas Section, continuing education seminar, spring 1980; “Twenty Years Operation of an In Situ Combustion Project”, by Jenkins and Kirkpatrick, Petroleum Society of CIM, 1978; and an article entitled "ln Situ Combustion Process - Results of a Five-Well Field Experiment, Southern Oklahoma,., by Moss, White and McNeil, Magnolia Petroleum Company, Dallas, Society of Petroleum Engineers of AIME, presented at the 33 rd Annual Fall Society Meeting, Houston, October 5-8, 1958.

L'article de White indique qu'en 1979, les procédés de combustion in situ ne représentaient encore qu'un faible pourcentage de la totalité de la production du pétrole par les méthodes thermiques. Il en conclut que l'un des éléments dissuasifs réside en ce que les procédés par combustion exigent un effort technique beaucoup plus intense que les autres procédés. En effet, ces. procédés nécessitent des équipements bien conçus destinés à la régulation des puits, à une -collecte rapide et précise des données, à une analyse rapide des données et, également, des opérateurs sur le terrain parfaitement formés. L'article indique que ces améliorations ne pourront être apportées que si ce type de procédé est très largement répandu.White's article indicates that in 1979, in situ combustion processes still represented only a small percentage of the total production of petroleum by thermal methods. He concludes that one of the dissuasive elements is that the combustion processes require a much more intense technical effort than the other processes. Indeed, these. processes require well-designed equipment for well regulation, rapid and accurate data collection, rapid data analysis, and also fully trained field operators. The article indicates that these improvements can only be made if this type of process is very widespread.

La régulation du procédé est essentielle et complexe. Pour suivre l'avance du front de combustion et pour prévoir les problèmes d'exploitation, il faut obtenir des données de base et les analyser, en particulier la vitesse de l'air, et sa pression, le taux d'injection de l'eau, la vitesse d'évacuation des gaz dans les différents puits, les pressions de cuvelage sur les puits de production, l'analyse du gaz, le taux de production de l'huile et de l'eau, les mesures de la température. Parmi les autres données, dont on a besoin plus rarement, mais d'une manière régulière, il faut citer la densité et la viscosité du pétrole sortant de chaque puits, le dosage du chlore dans l'eau, le pH de l'eau, la chute de pression des injecteurs. Le premier groupe de données permet de faire des calculs sur le mouvement du front, l'efficacité de la combustion et l'utilisation de l'oxygène. Le deuxième ensemble de données permet d'apporter des corrections aux données calculées et de se préparer à l'arrivée du front thermique dans un puits de production.Process regulation is essential and complex. To monitor the advance of the combustion front and to predict operational problems, basic data must be obtained and analyzed, in particular the air speed and its pressure, the injection rate of the water, gas evacuation speed in different wells, casing pressures on production wells, gas analysis, oil and water production rate, temperature measurements. Among the other data, which we need more rarely, but on a regular basis, we must mention the density and viscosity of the oil leaving each well, the determination of chlorine in water, the pH of water, the pressure drop of the injectors. The first group of data makes it possible to make calculations on the movement of the forehead, the efficiency of combustion and the use of oxygen. The second set of data makes it possible to make corrections to the calculated data and to prepare for the arrival of the thermal front in a production well.

On connaît par le brevet FR-A-1 473 669 (Deuts- che Erdôl) un procédé de récupération de pétrole par combustion in situ avec la possibilité de recourir éventuellement à la combustion du pétrole du gisement par un gaz de combustion activé, tel que composé d'anhydride carbonique, de vapeur d'eau et enrichi de grandes quantités d'oxygène.Patent FR-A-1 473 669 (German Erdôl) discloses a process for recovering petroleum by in situ combustion with the possibility of optionally resorting to the combustion of petroleum from the deposit by an activated combustion gas, such as composed of carbon dioxide, water vapor and enriched with large quantities of oxygen.

On connaît également par le brevet US-A-3 007 520 (FREY) un procédé similaire dont le gaz de combustion est éventuellement de l'oxygène, mais également de l'air, du CO et autres, les gaz de combustion étant introduits dans le gisement par des puits d'injection. Dans aucun de ces procédés des précautions ne sont prises pour séparer l'une de l'autre, l'introduction de l'oxygène dans le gisement et l'introduction dans le gisement des autres gaz de combustion.Also known from US-A-3 007 520 (FREY) is a similar process in which the combustion gas is optionally oxygen, but also air, CO and the like, the combustion gases being introduced into the deposit by injection wells. In none of these methods precautions are taken to separate from one another, the introduction of oxygen into the deposit and the introduction into the deposit of other combustion gases.

L'invention proposée par cette demande a pour objet un procédé de récupération de pétrole par combustion, in situ à partir d'une formation sédimentaire constituant un gisement de pétrole selon lequel on introduit un gaz entretenant la combustion tel que de l'air ou de l'air et de l'eau ou un gaz enrichi en oxygène ou de l'oxygène pur, par au moins un puits d'injection s'étendant de la surface et traversant des morts-terrains jusqu'à l'intérieur du gisement, dans une zone d'injection de façon à brûler une partie du pétrole en créant un front de flamme, qu'on fait progresser jusqu'à un certain point, et à provoquer l'écoulement, à travers une zone de traitement, des fluides dont le pétrole, vers un certain nombre de puits de production par lesquels les fluides sont extraits.The invention proposed by this application relates to a process for recovering petroleum by combustion, in situ from a sedimentary formation constituting an oil deposit according to which a gas supporting combustion is introduced such as air or air and water or a gas enriched in oxygen or pure oxygen, by at least one injection well extending from the surface and crossing overburden up to the interior of the deposit, in an injection zone so as to burn part of the oil by creating a flame front, which is advanced to a certain point, and to cause the flow, through a treatment zone, of fluids whose petroleum, to a number of production wells through which fluids are extracted.

Le procédé selon cette invention proposée est caractérisé en ce que, lorsque le gaz entretenant la combustion est de l'oxygène, on l'introduit par un conduit distinct et séparé du puits d'injection, ce conduit partant de la surface, traversant les morts-terrains et arrivant séparément dans le gisement à proximité du puits d'injection.The method according to this proposed invention is characterized in that, when the gas supporting combustion is oxygen, it is introduced by a separate conduit separate from the injection well, this conduit leaving the surface, passing through the dead - land and arriving separately in the deposit near the injection well.

L'installation d'application de ce procédé est caractérisée en ce qu'elle comprend également au moins un conduit d'oxygène distinct et séparé du puits d'injection, partant de la surface, traversant les morts-terrains et arrivant dans la zone de traitement en un point situé à une distance du puits d'injection beaucoup moindre que la distance entre un puits d'injection et un puits de production ledit conduit étant équipé de moyens pour introduire dans la formation de l'oxygène.The installation for applying this method is characterized in that it also comprises at least one oxygen conduit distinct and separate from the injection well, starting from the surface, passing through the overburden and arriving in the area of treatment at a point located at a distance from the injection well much less than the distance between an injection well and a production well, said conduit being equipped with means for introducing oxygen into the formation.

Selon le procédé de l'invention, la combustion in situ est régulée par la mise en place stratégique d'un ou plusieurs conduits de fluide, partant de la surface et traversant les morts-terrains pour arriver à la zone de traitement, en un point situé à une certaine distance du puits d'injection, le fluide de régulation étant introduit dans le gisement par l'intermédiaire dudit conduit, indépendamment du fluide injecté dans le puits d'injection. Selon un mode de réalisation préféré de l'invention, le fluide de régulation introduit est de l'oxygène, servant de gaz auxiliaire de combustion et remplaçant l'injection d'un gaz entretenant la combustion tel que l'air dans le puits d'injection. Dans ce cas, le conduit de fluide se trouve à proximité du puits d'injection, mais il en est séparé par une faible distance, de façon à permettre la mise en place, à la surface, d'un équipement de régulation distinct. Dans le cas d'un procédé de combustion par voie humide, on peut introduire alternativement l'oxygène et l'eau, l'oxygène étant envoyé par le conduit de fluide et l'eau par le puits d'injection.According to the method of the invention, in situ combustion is regulated by the strategic placement of one or more fluid conduits, starting from the surface and crossing the overburden to reach the treatment zone, at a point located at a certain distance from the injection well, the regulating fluid being introduced into the deposit via said conduit, independently of the fluid injected into the injection well. According to a preferred embodiment of the invention, the control fluid introduced is oxygen, serving as auxiliary combustion gas and replacing the injection of a gas supporting combustion such as air in the well. injection. In this case, the fluid conduit is located near the injection well, but it is separated by a short distance, so as to allow the establishment, on the surface, of a separate regulation equipment. In the case of a wet combustion process, oxygen and water can be introduced alternately, the oxygen being sent through the fluid conduit and the water through the injection well.

Selon un autre mode de réalisation, quand, lors de la surveillance du front de flamme propagé par l'air provenant du puits d'injection, on détecte une zone froide dans laquelle le front de flamme se déplace par exemple trop lentement pour s'immiscer dans la géométrie de la disposition d'implantation de puits et pour l'efficacité du balayage, on place un conduit de fluide de régulation dans cette zone, et on introduit de l'oxygène pour accélérer le front de flamme et améliorer le balayage. Ou bien encore, si lors de la surveillance, on voit que le front de flamme avance trop rapidement dans une certaine zone, on peut introduire un conduit de régulation dans cette zone et introduire des fluides appropriés pour ralentir le front de flamme et améliorer le balayage.According to another embodiment, when, when monitoring the flame front propagated by the air coming from the injection well, a cold zone is detected in which the flame front moves, for example too slowly to interfere in the geometry of the well layout arrangement and for the scanning efficiency, a regulating fluid conduit is placed in this zone, and oxygen is introduced to accelerate the flame front and improve the scanning. Or again, if during monitoring, we see that the flame front is advancing too quickly in a certain area, we can introduce a regulation duct in this area and introduce appropriate fluids to slow down the flame front and improve the sweep .

L'invention est de préférence utilisée avec un modèle classique de combustion in situ, de préférence une disposition d'implantation de puits du type à mailles à plusieurs puits, dans lequel on introduit de l'air et de l'eau dans un puits d'injection, qui part de la surface et traverse les morts-terrains pour arriver dans le gisement de pétrole, . dans une zone d'injection, dans des conditions conduisant à la combustion d'une partie du pétrole et à l'écoulement d'une partie du pétrole à travers une zone de traitement vers au moins un puits de production, disposé à une certaine distance du puits d'injection. Selon l'invention, on place d'une manière stratégique un conduit d'introduction d'oxygène, s'étendant de la surface et traversant les morts-terrains jusqu'au gisement de pétrole, dans la zone de traitement. Selon un mode de réalisation de l'invention, le conduit d'oxygène est placé à proximité du puits d'injection, mais à une distance suffisante pour que l'équipement de régulation de l'oxygène à la surface soit distinct de l'équipement de régulation relativement complexe se trouvant à la tête du puits d'injection. Par exemple, dans une disposition d'implantation de puits du type à mailles hexagonales à plusieurs puits, dans laquelle le puits d'injection est situé à environ 122 m de plusieurs, par exemple six puits de production, le conduit d'oxygène séparé peut se trouver à environ 3 à 4,6 m du puits d'injection.The invention is preferably used with a conventional in situ combustion model, preferably a multi-well mesh type well layout arrangement, in which air and water are introduced into a well. injection, which leaves the surface and crosses overburden to reach the oil field,. in an injection zone, under conditions leading to the combustion of part of the oil and the flow of part of the oil through a treatment zone to at least one production well, disposed at a certain distance from the injection well. According to the invention, an oxygen introduction conduit is placed strategically, extending from the surface and crossing the overburden to the oil deposit, in the treatment zone. According to one embodiment of the invention, the oxygen conduit is placed near the injection well, but at a sufficient distance so that the equipment for regulating oxygen at the surface is distinct from the equipment. relatively complex regulator at the head of the injection well. For example, in a multi-well hexagonal mesh type well layout, in which the injection well is located about 122 m from several, for example six production wells, the separate oxygen conduit may be approximately 3 to 4.6 m from the injection well.

Dans ce mode de réalisation, l'air et l'eau, dans un cycle de traitement représentatif, sont introduits alternativement dans le puits d'injection pour faire avancer le front de flamme jusqu'à un certain point. On arrête alors l'injection d'air, puis on utilise le puits d'injection pour introduire essentiellement uniquement de l'eau. On remplace l'air par de l'oxygène, qui est introduit dans le gisement par le conduit d'oxygène pour continuer l'avance du front de flamme.In this embodiment, air and water, in a representative treatment cycle, are introduced alternately into the injection well to advance the flame front to a certain point. The air injection is then stopped, then the injection well is used to introduce essentially only water. The air is replaced by oxygen, which is introduced into the deposit by the oxygen pipe to continue the advance of the flame front.

L'invention concerne aussi un mode de récupération du pétrole à partir d'une formation sédimentaire souterraine par le procédé de combustion par voie humide, mode selon lequel on a un puits d'injection, équipé pour introduire de l'air, ou de l'eau, ou les deux, dans des conditions assurant la combustion d'une partie du pétrole par l'air, et un certain nombre de puits de production, disposés à une certaine distance du puits d'injection, vers lesquels on fait s'écouler le pétrole à travers une zone de traitement. Un conduit d'oxygène séparé part de la surface, traverse les morts-terrains et arrive dans la zone de traitement de la formation, en un point situé à une certaine distance, relativement faible, du puits d'injection. Le puits d'injection est équipé d'un appareillage de régulation classique, relativement complexe, de l'air et de l'eau. Le fait que le conduit d'oxygène soit séparé simplifie considérablement le système de régulation à la surface tant pour le puits d'injection d'air que pour le conduit d'oxygène.The invention also relates to a method of recovering petroleum from an underground sedimentary formation by the wet combustion process, method according to which there is an injection well, equipped to introduce air, or l water, or both, under conditions ensuring the combustion of part of the oil by air, and a certain number of production wells, arranged at a certain distance from the injection well, towards which one is s' drain the oil through a processing area. A separate oxygen conduit starts from the surface, passes through the overburden and arrives in the formation treatment area, at a point located at a relatively short distance from the injection well. The injection well is fitted with conventional, relatively complex air and water control equipment. The fact that the oxygen pipe is separated considerably simplifies the surface control system for both the air injection well and the oxygen pipe.

L'invention sera mieux comprise au vu de la description qui suit et des dessins annexés, qui représentent des exemples de réalisation de l'invention, dessins dans lesquels :

  • la figure 1 est un schéma, en vue de dessus, illustrant une disposition d'implantation de trois mailles de puits, équipés selon l'invention ;
  • la figure 2 est une coupe verticale schématique d'une formation souterraine sédimentaire, à grande échelle ;
  • la figure 3 est un diagramme schématique montrant une courbe représentative de la répartition des températures dans une formation qui a subi un procédé classique de combustion in situ, à l'échelle de la figure 2 ;
  • la figure 4 est une coupe verticale schématique, partiellement en élévation, d'une formation dans laquelle est placée une installation de combustion par voie humide équipée selon l'invention ;
  • la figure 5 est une coupe verticale d'un injecteur de sécurité selon l'invention.
The invention will be better understood on the basis of the description which follows and of the appended drawings, which represent exemplary embodiments of the invention, drawings in which:
  • Figure 1 is a diagram, in top view, illustrating an arrangement of the layout of three mesh wells, equipped according to the invention;
  • Figure 2 is a schematic vertical section of a large-scale sedimentary underground formation;
  • Figure 3 is a schematic diagram showing a curve representative of the temperature distribution in a formation which has undergone a conventional process of combustion in situ, on the scale of Figure 2;
  • Figure 4 is a schematic vertical section, partially in elevation, of a formation in which is placed a wet combustion installation equipped according to the invention;
  • Figure 5 is a vertical section of a safety injector according to the invention.

La figure 1 représente une disposition d'implantation de puits « à trois mailles», comprenant trois puits d'injection A, A1 et A2. Une série de puits de production B sont placés par exemple d'une manière symétrique par rapport au puits d'injection A, à une certaine distance de ce dernier. On injecte de l'air à travers le puits d'injection A dans la formation souterraine dans une zone d'injection, pour permettre la combustion du pétrole. Les puits de production B se trouvant dans les zones de production sont équipés de moyens de pompage de sorte que, quand la combustion commence au voisinage du puits d'injection A, les fluides, qui comprennent des produits de combustion, de l'eau, de la vapeur et du pétrole, sont entraînés de la zone d'injection au voisinage du puits A, à travers une zone de traitement, pour arriver à une zone de production au puits B. Un front de flamme est produit dans la zone de traitement entre la zone d'injection et la zone de production.FIG. 1 shows a layout arrangement of “three-mesh” wells, comprising three injection wells A, A 1 and A 2 . A series of production wells B are placed, for example, symmetrically with respect to the injection well A, at a certain distance from the latter. Air is injected through the injection well A into the underground formation in an injection area, to allow combustion of the oil. The production wells B located in the production areas are equipped with pumping means so that, when combustion begins in the vicinity of injection well A, the fluids, which include combustion products, water, steam and petroleum, are drawn from the injection zone in the vicinity of well A, through a treatment zone, to reach a production zone at well B. A flame front is produced in the treatment zone between the injection zone and the production zone.

Selon un mode représentatif d'une combustion classique par voie humide, on effectue un cycle selon lequel on introduit de l'air pendant deux jours, puis de l'eau pendant un jour, et l'on répète ce cycle d'une manière continue pendant plusieurs mois ou plusieurs années. Par exemple, le puits d'injection A est situé au centre de la maille et les puits de production B se trouvent aux coins de l'hexagone, à une distance d'environ 122 m. La formation pétrolifère peut se trouver à de plusieurs dizaines à plusieurs centaines de mètres de la surface, par exemple à 610 m. L'épaisseur de la formation peut aller d'un minimum de 0,3 m à plus de 30 m. Par exemple, la plus grande partie du pétrole que l'on rencontre dans la zone de Lloydminister se présente dans des formations d'épaisseur d'environ 6 m. L'exploitation peut se continuer pendant plusieurs mois avant que ne commence la récupération, dans les puits de production, du pétrole provenant de la combustion in situ.According to a representative mode of a conventional wet combustion, a cycle is carried out according to which air is introduced for two days, then water for one day, and this cycle is repeated continuously for several months or several years. For example, the injection well A is located in the center of the mesh and the production wells B are at the corners of the hexagon, at a distance of approximately 122 m. The oil formation can be several tens to several hundred meters from the surface, for example 610 m. The thickness of the formation can range from a minimum of 0.3 m to more than 30 m. For example, most of the oil found in the Lloydminister area occurs in formations about 6 m thick. Exploitation can continue for several months before recovery begins in the production wells of oil from on-site combustion.

Selon l'invention, un conduit d'oxygène C part de la surface, traverse les morts-terrains et arrive dans le gisement de pétrole, dans la zone de traitement, à une certaine distance, relativement faible, du puits d'injection A. Par exemple, dans la disposition d'implantation représentée, le conduit d'oxygène C peut être à 4,6 m du puits d'injection.According to the invention, an oxygen conduit C starts from the surface, crosses overburden and arrives in the oil deposit, in the treatment zone, at a relatively short distance from the injection well A. For example, in the layout arrangement shown, the oxygen duct C can be 4.6 m from the injection well.

Bien que cette distance ne soit pas critique, il n'en reste pas moins qu'il est souhaitable que le conduit d'oxygène se trouve à une certaine distance du puits d'injection de façon à permettre de réaliser d'une manière indépendante l'exploitation de l'un et de l'autre. Dans tous les cas, un fluide doit s'écouler en permanence à travers le conduit d'oxygène et à travers le puits d'injection. Selon l'invention, une fois que le front de flamme a avancé dans la zone de traitement, jusqu'au point souhaité, on arrête l'injection d'air et d'eau dans le puits d'injection A et on introduit de l'oxygène dans le conduit d'oxygène, en alternance avec l'injection d'eau dans le puits d'injection.Although this distance is not critical, the fact remains that it is desirable that the oxygen duct be located at a certain distance from the injection well so as to allow independent realization l 'exploitation of both. In all cases, a fluid must constantly flow through the oxygen pipe and through the injection well. According to the invention, once the flame front has advanced in the treatment zone, to the desired point, the injection of air and water is stopped in the injection well A and the introduction of oxygen in the oxygen line, alternating with the injection of water into the injection well.

Dans une opération caractéristique de démarrage, on met en marche les pompes du puits de production et on extrait une certaine quantité de pétrole avant la combustion in situ. On peut ensuite allumer la flamme, par exemple en descendant un brûleur à gaz dans le puits d'injection, en envoyant de l'air ou du gaz naturel pour favoriser la combustion. Le brûleur peut ou bien rester en place, ou bien être récupéré, selon les circonstances.In a typical start-up operation, the production well pumps are turned on and a certain amount of oil is extracted before in situ combustion. The flame can then be lit, for example by lowering a gas burner into the injection well, by sending air or natural gas to promote combustion. The burner can either remain in place or be recovered, depending on the circumstances.

La figure 2 est une vue théorique de ce qui se passe lors d'une combustion in situ par voie humide. Cette figure est une coupe verticale d'une formation souterraine sédimentaire contenant du pétrole, également dénommée gisement de pétrole, qui a subi une combustion par voie humide. La formation se compose d'une zone d'injection entourant le puits d'injection A, destiné à introduire de l'air pour entretenir la combustion du pétrole dans le gisement et de l'eau pour modifier le transfert de chaleur selon la méthode de combustion par voie humide, et d'une zone de production entourant le puits de production B, destiné à extraire les fluides poussés en avant par le front de flamme. Entre ces deux zones se trouve une zone de traitement, et les différentes matières composant cette zone, à un stade particulier de l'exploitation, sont indiquées par des légendes sur la figure. Selon l'invention, un tube d'injection de gaz C est placé d'une manière stratégique dans la zone de traitement pour introduire l'oxygène destiné à favoriser la combustion ou réguler l'avance du front de flamme, comme on va le décrire en détail ci-après. Par exemple, dès que le front de flamme est arrivé en un certain point (voir figure 2), on peut placer un conduit d'oxygène, de façon à ce qu'il pénètre dans la région brûlée, puis introduire de l'oxygène pour favoriser la combustion, oxygène qui remplacera l'air injecté dans le puits A. Dans le cas d'une combustion par voie humide, on peut alterner l'introduction d'oxygène dans le conduit d'oxygène et l'introduction d'eau dans le puits d'injection. Une méthode représentative pourrait comprendre deux jours d'injection d'oxygène et un jour d'injection d'eau, pendant toute la période de traitement, qui peut durer jusqu'à plusieurs années.Figure 2 is a theoretical view of what happens during in situ wet combustion. This figure is a vertical section through an underground sedimentary formation containing petroleum, also known as an oil deposit, which has undergone wet combustion. The formation consists of an injection zone surrounding the injection well A, intended to introduce air to maintain the combustion of petroleum in the deposit and water to modify the heat transfer according to the method of wet combustion, and a production area surrounding the production well B, intended to extract the fluids pushed forward by the flame front. Between these two zones is a treatment zone, and the different materials making up this zone, at a particular stage of operation, are indicated by legends in the figure. According to the invention, a gas injection tube C is placed strategically in the treatment zone to introduce oxygen intended to promote combustion or to regulate the advance of the flame front, as will be described. in detail below. For example, as soon as the flame front has arrived at a certain point (see Figure 2), one can place an oxygen conduit, so that it penetrates into the burned region, then introduce oxygen to promote combustion, oxygen which will replace the air injected into well A. In the case of wet combustion, one can alternate the introduction of oxygen into the oxygen duct and the introduction of water into the injection well. A representative method could include two days of oxygen injection and one day of water injection, during the entire treatment period, which can last up to several years.

Dans la disposition d'implantation du type comportant trois mailles à sept puits représentée à la figure 1, le puits d'injection A est à environ 125 m (a) du puits de production B. La zone de traitement, entre le puits A et les puits B, couvre environ 4 hectares. L'épaisseur de la formation sédimentaire est comprise entre 0,3 et 30 m, et elle peut être à une profondeur d'environ 610 m, en étant recouverte par des morts-terrains dans lesquels il peut y avoir des formations pétrolifères sédimentaires supplémentaires séparées par de la roche. Le conduit d'oxygène C doit être placé à environ 3,0 à 4,6 m du puits d'injection.In the layout arrangement of the type comprising three meshes with seven wells represented in FIG. 1, the injection well A is approximately 125 m (a) from the production well B. The treatment zone, between well A and wells B, covers approximately 4 hectares. The thickness of the sedimentary formation is between 0.3 and 30 m, and it can be at a depth of about 610 m, being covered by overburden in which there may be separate additional sedimentary oil formations by rock. Oxygen line C should be placed approximately 3.0 to 4.6 m from the injection well.

La figure 4 représente une installation selon l'invention, en coupe verticale, dans une formation souterraine. Sur cette figure, le repère A désigne un puits d'injection d'air-eau. Le puits est formé d'un puits de forage, garni d'un cuvelage en acier 15, qui part de la surface, descend à travers les morts-terrains et arrive dans la formation sédimentaire souterraine dans laquelle se trouve le gisement de pétrole. Le trou de forage, à l'extérieur du cuvelage 15, est rempli d'une manière appropriée de matériaux de remplissage standards qui forment une enveloppe 17 doublant intérieurement le trou de forage. L'enveloppe 17 est garnie de perforations 19 pour permettre aux fluides de sortir du trou de forage. Le cuvelage 15 est garni d'un sabot de cuvelage 21. Un tube garni 23 part d'une tête de puits 25, située à la surface, pour arriver à un « packer récupérable 26, dont l'extrémité inférieure est centrée dans l'enveloppe 17. Une conduite d'air et d'eau 27 part d'une unité d'injection, et peut envoyer à la tête de puits 25 de l'air ou de l'eau sous pression. Des robinets-vannes 29 et 31 sont prévus, de même que des clapets de retenue 33 et des vannes à passage intégral 35 et 36 pour réguler l'écoulement d'air ou d'eau vers le tube 23. Les appareils placés au-dessus du puits A sont fréquemment appelés « arbre de Noël ».FIG. 4 represents an installation according to the invention, in vertical section, in an underground formation. In this figure, the reference A designates an air-water injection well. The well consists of a borehole, lined with a steel casing 15, which starts from the surface, descends through the overburden and arrives in the underground sedimentary formation in which the oil deposit is found. The borehole, outside the casing 15, is suitably filled with standard filling materials which form an envelope 17 internally lining the borehole. The casing 17 is lined with perforations 19 to allow the fluids to exit the borehole. The casing 15 is lined with a casing shoe 21. A lined tube 23 starts from a wellhead 25, located on the surface, to arrive at a “recoverable packer 26, the lower end of which is centered in the envelope 17. An air and water pipe 27 starts from an injection unit, and can send air head or pressurized water to the wellhead 25. Gate valves 29 and 31 are provided, as well as check valves 33 and full-flow valves 35 and 36 for regulating the flow of air or water to the tube 23. The apparatuses placed above from well A are frequently called "Christmas tree".

A une certaine distance du puits d'injection A, est placé un conduit d'oxygène C, formé d'un trou de forage logeant un cuvelage en acier 37 et une enveloppe en béton 36 remplissant l'espace entre le trou de forage et le cuvelage. Un tube d'oxygène 41, qui se prolonge au-delà du cuvelage 37 et traverse un « packer » récupérable 43 pour ressortir par le bas, s'étend dans le trou de forage. Le tube d'oxygène part de la surface, traverse les morts-terrains et pénètre dans la formation sédimentaire souterraine, dans la zone de traitement se trouvant entre le puits d'injection A et les puits de production B. Une conduite d'alimentation en oxygène 45 part d'une source d'oxygène sous pression, traverse une vanne à passage intégral 47 et arrive au tube d'oxygène 41. Comme, seul de l'oxygène est introduit dans le conduit C, le tube 41 n'a pas besoin d'être réalisé en un acier inoxydable onéreux tel que celui qui est nécessaire pour le puits d'injection A où la présence d'eau provoque une corrosion. De plus, on n'a besoin que d'un équipement de régulation de l'oxygène relativement simple.At a certain distance from the injection well A, an oxygen conduit C is placed, formed by a borehole housing a steel casing 37 and a concrete casing 36 filling the space between the borehole and the casing. An oxygen tube 41, which extends beyond the casing 37 and passes through a recoverable "packer" 43 to come out from below, extends into the borehole. The oxygen tube starts from the surface, crosses the overburden and enters the underground sedimentary formation, in the treatment zone located between the injection well A and the production wells. oxygen 45 starts from a pressurized oxygen source, passes through a full-flow valve 47 and arrives at the oxygen tube 41. Since only oxygen is introduced into the conduit C, the tube 41 does not need to be made of an expensive stainless steel such as that which is necessary for the injection well A where the presence of water causes corrosion. In addition, only relatively simple oxygen control equipment is required.

L'extrémité inférieure du tube d'oxygène possède un injecteur de sécurité D, qui est décrit en détail ci-après.The lower end of the oxygen tube has a safety injector D, which is described in detail below.

La figure 5 est une coupe verticale partielle agrandie du fond du conduit d'oxygène. L'extrê- mité du tube 41 porte un filetage extérieur destiné à recevoir un organe connecteur 51 cylindrique sur toute sa longueur. L'organe 51 possède un alésage intérieur, lequel possède une partie cylindrique 53, élargie et taraudée, engrénant avec l'extrémité du tuyau 41. L'alésage se rétrécit en une partie tronconique 54 pour arriver à une gorge 55, qui définit l'entrée d'un passage cylindrique central étranglé 57. L'extrémité inférieure de l'élément 51 possède un évidement annulaire 58, qui reçoit l'extrémité d'un tuyau 59 en alliage de nickel. Le tuyau 59 et l'organe connecteur 51 sont soudés l'un à l'autre en 61.Figure 5 is an enlarged partial vertical section of the bottom of the oxygen conduit. The end of the tube 41 carries an external thread intended to receive a cylindrical connector member 51 over its entire length. The member 51 has an internal bore, which has a cylindrical part 53, enlarged and tapped, meshing with the end of the pipe 41. The bore narrows into a frustoconical part 54 to arrive at a groove 55, which defines the inlet of a throttled central cylindrical passage 57. The lower end of the element 51 has an annular recess 58, which receives the end of a pipe 59 made of nickel alloy. The pipe 59 and the connector member 51 are welded to each other at 61.

Un élément de bout 63 est monté à l'extrémité inférieure du tuyau 59. L'élément 63 possède un corps cylindrique sur toute sa longueur, avec un évidement annulaire supérieur 60 recevant l'extrémité du tuyau 59. L'élément 63 et le tuyau 59 sont soudés l'un à l'autre en 65. Le corps de l'élément 63 possède un passage central, lequel possède une partie tronconique supérieure 67 se rétrécissant jusqu'à une courte gorge cylindrique 69, puis s'élargissant en une partie tronconique 71 se terminant par une partie tronconique plus courte et plus large 73. Les pièces 51 et 63 sont en un alliage de nickel non fissurable.A tip element 63 is mounted at the lower end of the pipe 59. The element 63 has a cylindrical body over its entire length, with an upper annular recess 60 receiving the end of the pipe 59. The element 63 and the pipe 59 are welded to each other at 65. The body of the element 63 has a central passage, which has an upper frustoconical part 67 narrowing to a short cylindrical groove 69, then widening in part frustoconical 71 ending in a shorter and wider frustoconical part 73. Parts 51 and 63 are made of a non-fissurable nickel alloy.

Les dimensions du conduit d'oxygène dépendent pour une grande part de la force nécessaire à la traction du « packer ». Le diamètre le plus petit serait d'environ 51 mm, le plus grand de 254 mm, 178 mm correspondant à un diamètre intermédiaire pratique. Ce diamètre doit être suffisant pour permettre d'introduire du ciment. En ce qui concerne l'introduction de l'oxygène, il suffit d'un tube d'un diamètre de 51 mm. Le diamètre maximum correspond à un conduit qui peut faire partie du puits proprement dit et être quand même cimenté. Pour favoriser la combustion, la pression est généralement la même que celle de l'air, et elle est comprise entre 28 et 70 kg/cm2. Une méthode de calcul empirique permet de calculer la pression, qui sera d'environ une demi-livre pour 30 cm de profondeur. La pression spécifique dépend à la fois de la profondeur et de la porosité de la formation. Les trous de forage peuvent avoir un diamètre quelconque. Il est prévu un piston plongeur pour chasser le ciment. Une unité se trouvant à la surface fournit de l'oxygène à basse pression à raison d'au moins 18 tonnes par jour, et le comprime à une pression de 28 à 70 kg/cm2. Le conduit d'oxygène doit être équipé de façon à permettre le remplacement rapide de l'oxygène par d'autres fluides.The dimensions of the oxygen pipe depend to a large extent on the force required to pull the packer. The smallest diameter would be approximately 51 mm, the largest of 254 mm, 178 mm corresponding to a practical intermediate diameter. This diameter must be sufficient to allow the introduction of cement. Regarding the introduction of oxygen, a tube with a diameter of 51 mm is sufficient. The maximum diameter corresponds to a pipe which can be part of the well itself and still be cemented. To promote combustion, the pressure is generally the same as that of air, and is between 28 and 70 kg / cm 2 . An empirical calculation method calculates the pressure, which will be about half a pound for 30 cm deep. The specific pressure depends on both the depth and the porosity of the formation. The boreholes can have any diameter. A plunger is provided to expel the cement. A unit on the surface supplies oxygen at low pressure at a rate of at least 18 tonnes per day, and compresses it to a pressure of 28 to 70 kg / cm 2. The oxygen pipe must be equipped with to allow rapid replacement of oxygen with other fluids.

Pour des raisons de sécurité, au moins une partie du passage, à travers lequel le gaz contenant l'oxygène est introduit, doit être étranglée de façon à avoir un diamètre tel que la vitesse du gaz soit supérieure à la vitesse maximum de la flamme susceptible de se produire. C'est ce que l'on obtient en utilisant un injecteur tel que celui décrit sur la figure 5. Cet injecteur possède des gorges étranglées, disposées en série, suivies d'un orifice de sortie de diamètre croissant destiné à permettre la détente du gaz dans le but de diminuer sa vitesse et réduire au maximum l'effet de sablage à l'intérieur du cuvelage.For safety reasons, at least part of the passage, through which the oxygen-containing gas is introduced, must be throttled so as to have a diameter such that the speed of the gas is greater than the maximum speed of the flame likely to to occur. This is what is obtained by using an injector such as that described in FIG. 5. This injector has throttled grooves, arranged in series, followed by an outlet opening of increasing diameter intended to allow the expansion of the gas. in order to reduce its speed and minimize the sanding effect inside the casing.

L'injecteur de sécurité tel que représenté est utilisable, non seulement pour l'oxygène, mais aussi pour l'oxygène mélangé à un autre fluide présentant des propriétés souhaitables pour la combustion in situ d'un gisement d'hydrocarbures, par exemple CO2, N2 air, H20, etc...The safety injector as shown can be used not only for oxygen, but also for oxygen mixed with another fluid having desirable properties for the in situ combustion of a hydrocarbon deposit, for example CO 2 , N 2 air, H 2 0, etc ...

Le tube en aval du « packer doit résister à la fissuration au contact de l'oxygène, à la chaleur, à la corrosion et à l'érosion. Outre celà, le tube doit présenter une sécurité maximum. Dans une formation d'hydrocarbures, par exemple, il peut se produire des perturbations et y avoir des suintements de combustibles à l'intérieur et autour du tube d'injection.'The tube downstream of the packer must resist cracking in contact with oxygen, heat, corrosion and erosion. Besides this, the tube must have maximum security. In an oil formation, for example, there may be disturbances and fuel seepage inside and around the injection tube. '

Un hydrocarbure peut brûler en présence d'air en donnant une flamme ayant une certaine vitesse. Si ce même hydrocarbure brûle avec de l'oxygène, sa vitesse de propagation de flamme peut être beaucoup plus élevée. Par exemple, le mélange méthane-air donne une vitesse maximum de propagation de flamme de 0,46 m/s, tandis que la flamme méthane-oxygène présente une vitesse maximum de propagation de 4,57 m/s. Le mélange hydrogène-air présente une vitesse maximum de propagation de flamme de 3 m/s, tandis que la flamme hydrogène-oxygène présente une vitesse maximum de propagation de flamme de 14 m/s. Comme, parmi les différentes espèces possibles que l'on peut rencontrer dans une formation d'hydrocarbures lors d'une combustion in situ, c'est le mélange hydrogène-oxygène qui donne une flamme ayant la vitesse de propagation maximum la plus élevée, il est impératif, du point de vue de la sécurité, de prendre ses précautions contre la vitesse de propagation de cette flamme.A hydrocarbon can burn in the presence of air giving a flame having a certain speed. If the same hydrocarbon burns with oxygen, its flame propagation rate may be much higher. For example, the methane-air mixture gives a maximum flame propagation speed of 0.46 m / s, while the methane-oxygen flame has a maximum propagation speed of 4.57 m / s. The hydrogen-air mixture has a maximum flame propagation speed of 3 m / s, while the hydrogen-oxygen flame has a maximum flame propagation speed of 14 m / s. As, among the various possible species that can be encountered in a formation of hydrocarbons during combustion in situ, it is the hydrogen-oxygen mixture which gives a flame having the highest maximum propagation speed, it it is imperative, from a safety point of view, to take precautions against the speed of propagation of this flame.

Un autre facteur qu'il convient de prendre en considération est l'effet de la pression sur la vitesse de propagation de la flamme. Par exemple, la vitesse de propagation de la flamme H2-02 est d'environ 19,81 m/s sous une pression de 21 kg/cm2, d'environ 28,35 m/s sous une pression de 63 kg/cm2, et de 30,48 m/s sous une pression de 105 kg/cm2. Another factor to consider is the effect of pressure on the speed of flame propagation. For example, the flame propagation speed H 2 -0 2 is approximately 19.81 m / s under a pressure of 21 kg / cm 2 , approximately 28.35 m / s under a pressure of 63 kg / cm 2 , and 30.48 m / s under a pressure of 105 kg / cm 2.

Lors de la conception des tubes d'injection au fond du forage, il faut en outre prendre en compte la résistance mécanique. Pour obtenir la résistance mécanique voulue, le diamètre intérieur du tube est généralement trop grand, de façon à permettre au gaz oxydant de s'écouler à une vitesse suffisamment élevée pour éviter un retour de flamme dans le tube. Dans ce cas, on peut installer une buse à la sortie du tube, pour accélérer le gaz oxydant jusqu'à une vitesse supérieure à la vitesse maximum de propagation de la flamme, pour éviter un retour de flamme dans le tube. Pour avoir une sécurité supplémentaire, on peut placer une ou plusieurs autres buses en amont de la buse de sortie, pour résister à tout retour de flamme.When designing the injection tubes at the bottom of the borehole, mechanical resistance must also be taken into account. To obtain the desired mechanical resistance, the internal diameter of the tube is generally too large, so as to allow the oxidizing gas to flow at a sufficiently high speed to avoid a flashback in the tube. In this case, a nozzle can be installed at the outlet of the tube, to accelerate the oxidizing gas to a speed greater than the maximum speed of propagation of the flame, to avoid a flashback in the tube. For additional security, one or more other nozzles can be placed upstream of the outlet nozzle, to resist any backfire.

Si le débit du gaz oxydant à travers le tube (qui présente une résistance mécanique suffisante) est suffisamment élevé pour que la vitesse du gaz soit plus grande que la vitesse maximum prévue de propagation de la flamme susceptible de se trouver au niveau du puits d'injection, il n'est pas nécessaire de faire appel à des buses accélérant le gaz oxydant.If the flow rate of the oxidizing gas through the tube (which has sufficient mechanical strength) is high enough for the speed of the gas to be greater than the maximum speed of propagation of the flame likely to be at the level of the well. injection, it is not necessary to use nozzles accelerating the oxidizing gas.

Ces buses peuvent se présenter sous la forme d'un alésage droit, ou bien elles peuvent être d'un type à venturi, tel que celui représenté sur la figure 5, destiné à éviter les fissurations au contact de l'oxygène qui diminueraient la résistance mécanique, et à empêcher tout retour de flamme dans le tube.These nozzles can be in the form of a straight bore, or they can be of a venturi type, such as that shown in FIG. 5, intended to avoid cracks in contact with oxygen which would reduce the resistance mechanical, and to prevent any backfire in the tube.

De préférence, on choisira par exemple le monel, pour sa résistance à la combustion au contact de l'oxygène gazeux. De plus, il est relativement résistant à la corrosion. On utilise un tube de diamètre de 50,8 mm, nomenclature 80 (c'est-à-dire un tube ayant un diamètre externe de 60,31 mm et un diamètre interne de 49,21 mm, l'espacement de ses parois étant de 5,5 mm), pour sa résistance mécanique, car il présente une longueur libre de 550 m.Preferably, one will choose for example the monel, for its resistance to combustion in contact with gaseous oxygen. In addition, it is relatively resistant to corrosion. A tube with a diameter of 50.8 mm, nomenclature 80 is used (that is to say a tube having an external diameter of 60.31 mm and an internal diameter of 49.21 mm, the spacing of its walls being 5.5 mm), for its mechanical strength, because it has a free length of 550 m.

Pour éviter un retour de flamme, on place une buse à venturi au fond, à l'orifice de sortie de l'injecteur. A titre de sécurité complémentaire, on place une autre buse en amont.To avoid a flashback, a venturi nozzle is placed at the bottom, at the injector outlet. As additional security, another nozzle is placed upstream.

L'injecteur est conçu par exemple pour un débit d'oxygène de 84 950 m3/jour sous une pression de 31,5 kg/cm2 à la température ambiante. Pour être certain que l'on évitera le retour de flamme grâce à l'une ou l'autre des deux buses, la gorge de la buse à venturi présente un diamètre d'environ 11,4 mm, ce qui permet au gaz oxydant d'avoir une vitesse de 30,5 m/s, vitesse qui est plus élevée que toute vitesse de propagation de flamme que l'on peut rencontrer au fond d'un puits d'injection ou d'un conduit d'oxygène.The injector is designed, for example, for an oxygen flow rate of 84,950 m 3 / day under a pressure of 31.5 kg / cm 2 at ambient temperature. To be sure that the flashback is avoided thanks to one or the other of the two nozzles, the groove of the venturi nozzle has a diameter of about 11.4 mm, which allows the oxidizing gas to '' have a speed of 30.5 m / s, a speed which is higher than any flame propagation speed that can be encountered at the bottom of an injection well or an oxygen pipe.

L'orifice ou les orifices de sortie de l'injecteur peuvent se présenter sous la forme d'un ou plusieurs trous. Chaque trou doit être dimensionné de façon à donner au gaz oxydant injecté une vitesse supérieure à la vitesse maximum de propagation de flamme que l'on peut rencontrer.The outlet orifice (s) of the injector may be in the form of one or more holes. Each hole must be dimensioned so as to give the oxidizing gas injected a speed greater than the maximum flame propagation speed that can be encountered.

L'injecteur au fond du trou ne peut être utilisé que pour le gaz oxydant ou un mélange de gaz, ou bien il peut être utilisé en alternance avec une injection d'eau, de manière intermittente. Par exemple, il peut être utilisé pour le gaz oxydant et le mélange de gaz avec les autres fluides injectés (par exemple H20 et/ou air), injectés dans la formation par un autre puits d'injéction. Dans ce cas, l'eau, l'air ou les autres fluides n'ont pas besoin d'être exempts d'hydrocarbures (par exemple de pétrole). Par ailleurs, si tous les fluides destinés au puits d'injection doivent être injectés dans la formation en n'utilisant que ce seul injecteur, tous les fluides devront être exempts de pétrole, en particulier quand le gaz oxydant est l'oxygène.The downhole injector can only be used for oxidizing gas or a mixture of gases, or it can be used alternately with water injection, intermittently. For example, it can be used for the oxidizing gas and the mixture of gases with the other injected fluids (for example H 2 0 and / or air), injected into the formation by another injection well. In this case, water, air or other fluids need not be free of hydrocarbons (e.g. petroleum). Furthermore, if all the fluids intended for the injection well must be injected into the formation using only this single injector, all the fluids must be free of petroleum, in particular when the oxidizing gas is oxygen.

L'invention est caractérisée par l'introduction, définie d'une manière stratégique, de l'oxygène en remplacement de l'air en tant que gaz favorisant la combustion ; par oxygène, on entend ici un oxygène ayant une concentration en volume de 90 % (dans les conditions normales), ou plus, et de préférence une concentration d'au moins 99,5 %.The invention is characterized by the introduction, defined in a strategic manner, of oxygen instead of air as a gas promoting combustion; by oxygen is meant here an oxygen having a volume concentration of 90% (under normal conditions), or more, and preferably a concentration of at least 99.5%.

Le fait d'utiliser un conduit d'oxygène séparé permet, par rapport à un puits d'injection équipé pour injecter de l'air et de l'eau, d'introduire d'une manière sélective l'oxygène sans faire appel aux dépenses très élevées, du point de vue technique et matériel, d'un puits d'injection équipé pour l'injection d'oxygène. Par exemple, du fait de la présence d'éléments et de composés corrosifs dans l'eau, qui, en présence d'oxygène, ont tendance à accélérer l'action de la corrosion, il est nécessaire d'utiliser dans un puits d'injection des matériaux donnant une protection suffisante contre la corrosion. Ces matériaux peuvent être par exemple des aciers inoxydables, de l'inconel, du monel, de l'haystellite, etc. De plus, la présence de pétrole dans l'air éjecté, provoquée par la lubrification du compresseur d'air, peut, en présence d'oxygène, créer un risque d'explosion. Pour résoudre ce problème, il faut faire appel à des filtres à huiles spéciaux. L'installation nécessaire, pour des raisons de sécurité, à la régulation des débits de l'air et/ou de l'oxygène exige une installation complexe en surface.The fact of using a separate oxygen conduit allows, compared to an injection well equipped to inject air and water, to selectively introduce oxygen without calling for expenses very high, from a technical and material point of view, an injection well equipped for oxygen injection. For example, due to the presence of corrosive elements and compounds in water, which, in the presence of oxygen, tend to accelerate the action of corrosion, it is necessary to use in a well of injection of materials giving sufficient protection against corrosion. These materials can be for example stainless steels, inconel, monel, haystellite, etc. In addition, the presence of petroleum in the ejected air, caused by the lubrication of the air compressor, can, in the presence of oxygen, create a risk of explosion. To solve this problem, special oil filters must be used. The installation necessary, for safety reasons, to regulate the air and / or oxygen flow rates requires a complex installation on the surface.

Si l'on utilise un conduit séparé pour l'injection de l'oxygène, on évite ces problèmes. L'eau ne s'écoule pas à travers le conduit d'oxygène, de sorte que ce dernier est entièrement sec et il n'est pas nécessaire d'utiliser des matériaux anti-corrosion. On peut donc utiliser des tubes en acier moins cher. Compte tenu du coût relativement plus faible de ce conduit d'oxygène, on peut en utiliser plusieurs en des points successifs au fur et à mesure de l'avance du front de flamme. Il peut aussi être souhaitable, dans certaines conditions, d'utiliser de l'oxygène avec différentes concentrations d'air, d'azote ou de dioxyde de carbone ou d'autre gaz en un ou plusieurs points de la disposition d'implantation de puits de façon à produire des effets spéciaux tels que décrits dans la présente invention.If a separate line is used for injection oxygen, these problems are avoided. Water does not flow through the oxygen pipe, so that it is completely dry and there is no need to use anti-corrosion materials. We can therefore use cheaper steel tubes. Given the relatively lower cost of this oxygen pipe, several can be used at successive points as the flame front advances. It may also be desirable, under certain conditions, to use oxygen with different concentrations of air, nitrogen or carbon dioxide or other gas at one or more points in the well layout arrangement. so as to produce special effects as described in the present invention.

Le rendement théorique de balayage que l'on peut obtenir avec de l'oxygène est d'environ 45 à 50 %, ce qui est considérablement plus faible que quand on utilise de l'air. En effet, il y a moins de ballast d'azote et une pression partielle de C02 plus élevée dans l'oxygène combiné au coke. Il y a plus de C02 dans le pétrole, ce qui diminue sa viscosité, augmente le débit de production et diminue l'entraînement d'azote dans le puits de production. Il est difficile de dissoudre l'émulsion qui se forme au niveau du puits de production quand on utilise de l'air en tant que gaz favorisant la combustion. Quand on utilise de l'oxygène, l'émulsion formée est plus facile à dissoudre. Le produit sortant du puits de production, quand on utilise l'air, contient du pétrole et du sable, de l'eau, du gaz, du C02 et de l'azote, un peu de méthane, un peu d'hydrogène et un peu de soufre. Quand on utilise de l'oxygène, il y a très peu d'azote, plus de CO2, moins de sable, d'eau et de méthane. Le débit critique d'air serait d'environ 5 660 m3 par puits et par jour. Avec ce même débit critique, on a cinq fois plus d'oxygène, un débit de production plus élevé, un entraînement plus faible et on récupère un tiers de plus de pétrole.The theoretical scanning efficiency which can be obtained with oxygen is about 45 to 50%, which is considerably lower than when using air. Indeed, there is less nitrogen ballast and a higher partial pressure of C0 2 in the oxygen combined with the coke. There is more C0 2 in the oil, which decreases its viscosity, increases the production rate and decreases the entrainment of nitrogen in the production well. It is difficult to dissolve the emulsion that forms at the production well when using air as the combustion promoting gas. When using oxygen, the emulsion formed is easier to dissolve. The product leaving the production well, when using air, contains petroleum and sand, water, gas, C0 2 and nitrogen, a little methane, a little hydrogen and a little sulfur. When you use oxygen, there is very little nitrogen, more CO 2 , less sand, water and methane. The critical air flow would be approximately 5,660 m 3 per well per day. With this same critical flow, we have five times more oxygen, a higher production flow, a lower entrainment and we recover a third more oil.

Les différents avantages qu'il y a à utiliser l'oxygène, par rapport à l'air, dans une combustion in situ, ont été décrits dans le brevet canadien N° 770 434, Moore du 31 octobre 1967, et dans le brevet des Etats-Unis d'Amérique N° 3 208 519, Moore du 28 septembre 1965. Ces brevets décrivent les avantages qu'il y a à utiliser de l'oxygène ou un gaz contenant jusqu'à 80 % d'oxygène libre. Cependant, le procédé de l'invention ne doit pas être confondu avec ceux décrits dans les brevets de Moore, qui utilisent un puits d'injection, à la fois pour l'oxygène et pour l'eau. Au contraire, selon l'invention, on effectue l'introduction de l'oxygène dans un conduit simple séparé dans lequel l'oxygène peut être envoyé par l'intermédiaire d'un train de tiges de faible coût, par exemple en acier doux au carbone. Le tube doit simplement présenter une résistance mécanique suffisante pour résister aux forces appliquées lors de son installation, et son orifice de sortie doit être convenablement façonné de façon à résister aux températures auxquelles il risque d'être exposé. Quand, par exemple, le conduit est installé en avant du front de flamme, le tube peut être protégé par une enveloppe d'eau ou un ciment épais. Il doit toujours y avoir un écoulement de fluide à travers le tube, de la même façon que dans le puits d'injection, pour éviter tout reflux dans le conduit. L'extrême souplesse d'utilisation d'un conduit de ce type pour l'injection d'oxygène ressort clairement de la description ci-dessus.The various advantages of using oxygen over air in in situ combustion have been described in Canadian Patent No. 770,434, Moore of October 31, 1967, and in the United States Patent. United States of America No. 3,208,519, Moore of September 28, 1965. These patents describe the advantages of using oxygen or a gas containing up to 80% free oxygen. However, the process of the invention should not be confused with those described in the Moore patents, which use an injection well, both for oxygen and for water. On the contrary, according to the invention, the introduction of the oxygen is carried out in a separate simple conduit into which the oxygen can be sent via a low-cost drill string, for example made of mild steel to carbon. The tube must simply have sufficient mechanical strength to withstand the forces applied during its installation, and its outlet orifice must be suitably shaped so as to withstand the temperatures to which it may be exposed. When, for example, the duct is installed in front of the flame front, the tube can be protected by a jacket of water or thick cement. There must always be a flow of fluid through the tube, in the same way as in the injection well, to avoid any backflow in the conduit. The extreme flexibility of using a pipe of this type for injecting oxygen is clear from the description above.

Il existe un certain nombre de brevets décrivant des variantes du procédé de combustion in situ, comportant l'injection d'autres substances en même temps que l'air et/ou l'eau, et il n'est pas jugé nécessaire de les étudier en détail, car elles sont connues dans la technique et n'affectent en rien la réalisation générale du procédé selon l'invention. En outre, il est bien entendu que la représentation de l'implantation des puits est simplifiée. On a représenté une disposition d'implantation de puits à trois mailles, mais il peut y avoir un nombre quelconque de mailles dans le plan d'implantation d'un champ. En outre, on n'a pas représenté les puits d'observations, qui sont souvent utilisés pour étudier la nature des formations sédimentaires souterraines. Il est bien entendu que les différents moyens utilisés dans ce but et pour surveiller l'avance du front de flamme peuvent être utilisés en combinaison avec l'invention.There are a number of patents describing variants of the in situ combustion process, involving the injection of other substances at the same time as air and / or water, and it is not considered necessary to study them in detail, because they are known in the art and do not affect the general implementation of the method according to the invention. In addition, it is understood that the representation of the siting of the wells is simplified. An arrangement of siting of wells with three meshes has been shown, but there may be any number of meshes in the siting plan of a field. In addition, observation wells are not shown, which are often used to study the nature of underground sedimentary formations. It is understood that the various means used for this purpose and for monitoring the advance of the flame front can be used in combination with the invention.

L'utilisation d'un ou plusieurs conduits d'oxygène séparés permet aussi une grande souplesse pour l'injection de l'oxygène dans la formation, non seulement au-dessus de la zone de traitement, mais aussi à différents niveaux. Par exemple, des conduits peuvent aller jusqu'à des niveaux en dessous desquels l'eau est injectée dans le puits d'injection dans le cas d'une combustion par voie humide. Par exemple, l'oxygène peut être introduit au voisinage du fond du gisement de pétrole ou en des points intermédiaires. Quand l'eau a tendance à s'écouler vers le bas et l'oxygène vers le haut, une disposition de ce genre peut améliorer les interactions entre l'oxygène introduit et l'eau injectée en ce qui concerne la propagation et la régulation du front de flamme. Avec un simple conduit, le niveau de l'orifice de sortie peut être plus facilement ajusté qu'avec un puits d'injection.The use of one or more separate oxygen conduits also allows great flexibility for injecting oxygen into the formation, not only above the treatment area, but also at different levels. For example, conduits can go up to levels below which water is injected into the injection well in the case of wet combustion. For example, oxygen can be introduced near the bottom of the oil deposit or at intermediate points. When water tends to flow downwards and oxygen upwards, a provision of this kind can improve the interactions between the oxygen introduced and the water injected with regard to the propagation and regulation of the flame front. With a simple conduit, the level of the outlet can be more easily adjusted than with an injection well.

Les critères concernant les quantités relatives d'oxygène et d'eau qu'il faut injecter aux différents stades de la combustion in situ et dans les différents états produits par cette dernière ont déjà été établis. D'une manière générale, le rapport entre l'eau et l'oxygène libre doit être inférieur à celui auquel la combustion s'éteindrait. Simultanément, il faut injecter suffisamment d'eau dans le puits d'injection pour maintenir la perméabilité à l'eau de la partie chauffée du gisement en arrière du front de flamme et pour réduire la température à l'intérieur de cette partie chauffée. Les quantités précises, pour un traitement donné, dépendent de différents facteurs, comme cela est étudié dans l'état actuel de la technique.The criteria for the relative amounts of oxygen and water to be injected at the different stages of in situ combustion and in the different states produced by it have already been established. Generally, the ratio of water to free oxygen should be less than that at which combustion would go out. Simultaneously, sufficient water must be injected into the injection well to maintain the water permeability of the heated part of the deposit behind the flame front and to reduce the temperature inside this heated part. The precise amounts, for a given treatment, depend on various factors, as is studied in the current state of the art.

Claims (18)

1. Method for oil recovery by in situ combustion starting from a sedimentary formation comprising a deposite of oil and petroleum, respectively, according to which a gas is introduced maintaining the combustion such as air or air and water or a gas enriched with oxygen or pure oxygen, by at least an injection shaft or well extending from the surface and transversing the rubbish until the interior of the deposite, in an injection zone to burn a part of the petroleum creating a flame front which is permitted to progress up to a certain point, and to provoke the discharge of fluids across a treatment zone, such as the petroleum, to a certain number of production shafts by which the fluids are extracted, characterized by that if the gas maintaining the combustion is oxygen, one introduces it through a distinct conduit (C) and separated from the injection shaft, the conduit starting from the surface, transversing the earth roof or rubbish and arriving separately in the deposite near to the injection shaft (A, Ai, A2).
2. Method according to claim 1, by which one introduces air and water through the injection shaft to render the front of the flame advancing to a certain point, characterized by that, in order to continue the advance of the front of the flame beyond this point, one stops the introduction of water and one introduces oxygen by its distinct and separated conduit (C).
3. Method according to claim 2, characterized by that, in order to render the front of the flame to progress beyong a certain point of the treatment zone, one places another distinct conduit (C) behind the front of the flame after its passage by this point and one introduces the oxygen by this other conduit to create a supplemental source of heat behind the said front of flame.
4. Method according to claim 1, characterized by that the oxygen is injected in the distinct and separated oxygen conduit (C) at a speed higher than the maximum propagation speed of the flame in the immediate neighbourhood of the said oxygen conduit (C).
5. Method according to claim 1, characterized by that the advance of the front of the flame across the treatment zone is regulated by locating the supplemental oxygen conduits (C) to the interior of the treatment zone in order to increase the efficiency of flushing.
6. Method according to claim 1, characterized by that if the irregularities disturbing the symmetry of the shape of the combustion in situ occur, one places at least one oxygen conduit (C) separated and distinct of the injection shaft (A, A,, A2) starting from the surface and transversing the rubbish up to the treatment zone, and one introduces oxygen through the said conduit (C) in order to modify the advance of the front of the flame with the end to improve the symmetry of the flushing.
7. Method according to claim 1, characterized by that the flushing symmetry is improved and regulated by locating selectively oxygen conduits (C) and by the introduction of oxygen through the said conduits (C).
8. Method according to claim 1, by which one starts and continues the combustion of petroleum in the deposite by injecting air into the injection shaft, characterized by that one stops the injection of air and one introduces the oxygen by at least one conduit (C) distinct and separated of the injection shaft (A, Ai, A2) and one continues the injection of oxygen in order to render the front of the flame advancing across another part of the treatment zone.
9. Method according to claim 1, by which one introduces water alternating with air in accordance to the advance of the front of the flame across a first part of the treatment zone, characterized in that one injects water into the injection shaft (A, A" A2) alternating with the introduction of oxygen by the oxygen conduit (C).
10. Method according to claim 1, characterized by that one introduces the oxygen by its distinct and separated conduit (C) in order to improve the tracking of the front of the flame in the advance thereof.
11. Method according to claim 1, characterized by that one introduces the oxygen by its distinct and separated conduit (C) at a lower level to that at which the water is injected into the injection shaft (A, A1' A2).
12. Method according to claim 1, characterized by that one injects the oxygen by a plurality of distinct and separated conduits (C) at respectively different levels under the level at which the water is injected into the injection shaft (A, Ai, A2).
13. Method according to claim 1, characterized by that one introduces the oxygen by narrow passages in order to increase its speed of introduction into the treatment zone.
14. Installation of application of the method according to one of the preceeding claims, especially for the petroleum recovery in situ, starting from sedimentary underground formations comprising a deposite of petroleum, this installation comprising production shafts (B) arranged to form a disposition of implantation shafts and injection shafts (A, A1' A2) starting from the surface, transversing the rubbish and arriving in the deposite in an injection zone, the production shafts (B) being equipped with means to extract fluids from the formation and being in a production zone disposed a distance a of an injection shaft, these injection shafts being equipped with means to inject a gas maintaining the combustion, such as air or air and water or a gas enriched with oxygen, the zone of production being separated from the injection zone by a treatment zone, characterized by that it also comprises at least a distinct oxygen conduit (C) separated from the injection shaft (A, A1' A2), starting from the surface, transversing the rubbish and arriving in the treatment zone at a point situated at a distance from the injection shaft (A, A1' A2) much less than the distance a, the conduit (C) being equipped with means to introduce the oxygen into the formation.
15. Installation according to claim 14, characterized by that the means to introduce the oxygen comprise an oxygen conduit (C) formed of a boring which is distinct and separated from the injection shaft (A, A,, A2), comprising an oxygen tube (41) reaching to the ground of the shaft where it traverses a « packer (43) for discharging downwards and terminating through an security injector (D), the oxygen tube (41) being connected at the upper part thereof outside the shaft across a valve (47) to a conduit (45) supplying oxygen, starting from a source of oxygen under pressure.
16. Installation according to claim 15, characterized by that the security injector (D) comprises a cylindrical connector element (51) forming a boring with an internal thread engaging the end of the tube (41), this boring narrowing in a frustoconical part (54) to arrive at a neck (55) defining the entrance of the cylindrical central passage (57), the lower end of the element (51) comprising an annular recess (58) receiving the end of the tube (59).
17. Installation according to claim 16, characterized by that the security injector (D) comprises also an end element (63) mounted at the lower end of the tube (59), comprising a cylindrical body provided with a central passage provided with a upper frustoconical part (67) narrowing to a short cylindrical neck (69) and then enlarging into a frustoconical part (71), thus comprising the form of a nozzle element.
18. Installation according to claim 17, characterized by that the end of the exit (73) of the passage provided in the nozzle element, enlarges in order to permit the release of tension 35 of the oxygen at the orifice of the exit of the oxygen conduit (C).
EP82401680A 1981-09-18 1982-09-16 Method and installation for oil recovery by in situ combustion Expired EP0075515B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82401680T ATE16624T1 (en) 1981-09-18 1982-09-16 PROCESS AND APPARATUS FOR OIL RECOVERY BY COMBUSTION ON SPOT.

Applications Claiming Priority (2)

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CA000386166A CA1206411A (en) 1981-09-18 1981-09-18 Oil recovery by in situ combustion
CA386166 1981-09-18

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EP0075515A1 EP0075515A1 (en) 1983-03-30
EP0075515B1 true EP0075515B1 (en) 1985-11-21

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EP (1) EP0075515B1 (en)
AT (1) ATE16624T1 (en)
BR (1) BR8205528A (en)
CA (1) CA1206411A (en)
DE (1) DE3267617D1 (en)
EG (1) EG16308A (en)
NO (1) NO162091C (en)
OA (1) OA07214A (en)

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Publication number Publication date
ATE16624T1 (en) 1985-12-15
EP0075515A1 (en) 1983-03-30
US4557329A (en) 1985-12-10
CA1206411A (en) 1986-06-24
BR8205528A (en) 1983-08-30
DE3267617D1 (en) 1986-01-02
NO162091C (en) 1989-11-01
NO823162L (en) 1983-03-21
OA07214A (en) 1984-08-31
NO162091B (en) 1989-07-24
EG16308A (en) 1991-06-30

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