FR2901838A1 - Heavy crude stimulated recovery performing method, involves arranging vapor communication unit between two chambers, and utilizing vapor communication unit for regulating vapor injection between chambers - Google Patents

Abstract

The method involves generating vapor from a solar collector (7) e.g. cylindrical-parabolic concentrating collector, and injecting the vapor in a steam assisted gravity drainage (SAGD) small sized chamber (2`) of a reservoir (3) and collectively in a chamber (2``). A vapor communication unit is arranged between the chambers, and the vapor communication unit is utilized for regulating vapor injection between the chambers. The chamber (2``) stores the vapor. An independent claim is also included for an optimized installation for stimulated recovery of heavy crude.

Description

Technical area

  The invention relates to the field of the recovery of petroleum crudes, in particular heavy and extra-heavy crudes by the technique of steam injection.

Prior art

  The technical problem is to improve the efficiency of the recovery of heavy and extra-heavy crudes by the technique of steam injection, in particular by the technique often referred to as SAGD (Steam Assisted Gravity Drainage). More precisely, the invention consists in optimizing the combination of solar energy instead of fossil fuels with the means of producing the steam necessary for the recovery of heavy and extra-heavy crudes by the technique of steam injection. .

  Operation of the process for recovering extra-heavy crudes by the technique of steam injection

  The technique of steam injection is a known technique that is well suited to the exploitation of heavy crude deposits at moderate depth (up to a few hundred meters). In its most widespread version - SAGD "Steam Assisted Gravity Drainage" - one uses (Figure 1) two horizontal wells crossing the deposit (3) to exploit. The upper well (1) injects the steam at a temperature of 250 to 350 C, for heating the crude in the swept area (2). The viscosity reduction of the crude allows it to flow down the vapor-swept chamber (4), where the lower well (5) collects the crude and water mixture. The size of the steam-swept chamber increases progressively as operation progresses. Currently, one of SAGD's major problems is the significant greenhouse gas emissions associated with steam production, as it is produced from natural gas or fuel oil. It is estimated that steam production generates about 120 kg of 002 per barrel of crude produced. Separation and reinjection of this gas are particularly expensive. Another problem is the availability of economical fuels for steam production because gas resources are often limited and the use of fuel is expensive. To limit the energy consumption it is common to recover the thermal energy of fluids produced, whose temperature is of the order of 200 or 250 C, to preheat the water for the production of steam.

  In order to improve the efficiency of the recovery of heavy and extra heavy crudes, it is interesting: - to avoid the significant emission of greenhouse gases associated with a conventional steam production (estimated at 120 kg of CO2 per barrel produced on average), - to avoid burning part of the crude oil extracted to produce steam (25% of the quantities produced on average), thus increasing the quantities of crude that can be placed on the market, otherwise says the reserves, - to diversify the sources of energy significantly.

  The use of solar energy instead of fossil fuels for the production of steam in the technique of steam injection overcomes these disadvantages.

  Techniques for capturing solar energy

  Flat solar thermal collectors include an absorbing element behind a glazing ensuring an adequate greenhouse effect, according to a principle known for a long time. The temperatures reached by good sunshine approach 100 C [Thermal solar collectors, Techniques de l'Ingénieur, 2005].

  The evacuation of the absorbent element makes it possible to reduce the heat losses and thus allows higher temperatures, but nevertheless lower than 130 C in general. Since these temperatures can be reached simply by recovering the thermal energy of the fluids produced in an SAGD process, this type of sensor can not meet the intended use.

  The concentrating solar collectors make it possible to obtain significantly higher temperatures (300 ° C. and higher) by focusing the sun's rays towards the absorbing element [B. Rivoire, Solar thermodynamics, in The energy of tomorrow, edited by J. L. Bobin, E. Huffer and H. Niffenecker, EDP Sciences, Les Ulis, France, 2005]. They generally include one or more north-south axis mirrors whose orientation must be controlled to maintain the focus by following the apparent movement of the sun in the sky. This technology includes in particular parabolic trough sensors, the principle of which is relatively simple since their orientation involves only one degree of freedom instead of two in the sensors which aim for a higher concentration factor. Known since the 19th century, these sensors can reach temperatures approaching 500 C in the most recent versions, used on an industrial scale in the deserts of the southern United States to produce about 600 GWh of electricity per year [ Sargent-Lundy, National Renewable Energy Laboratory, Golden, Co, USA, 530-344440, 2003.]. The latter versions use a heat transfer fluid [Sargent-Lundy, National Renewable Energy Laboratory, Golden, Co, USA, 530-344440, 2003] or superheated air [US 6,694,738 B2, 2001] and therefore require a boiler to produce steam from the power plant.

  To simplify the steam generating device, it has been tried to directly generate the steam in the collector tube of the sensor in a pilot device for direct steam generation [M. Muller, Direct solar steam in parabolic trough collectors. Plataforma solar from Almeria (PSA), CIEMAT and DLR, ISBN 84-605-1479-X, 1994; E. Zarza, L. Valenzuela, J. Leon, H. Weyers, M. Eickhoff, M. Eck and K. Hennecke, The DISS Project: Direct Steam Generation in Parabolic Trough Systems. Operation and Maintenance Experience and Update on Project Status, Journal of Solar Energy Engineering 124 (2002) 126-133], but the control of such a system is complex.

  Indeed, the system provides for the direct production of steam in the absorbent element of a parabolic trough sensor by means of a horizontally arranged sensor train, but such an arrangement makes it necessary to have a liquid-vapor separator at the outlet of the solar collectors. . Furthermore, the horizontal arrangement of the sensor 3 may cause unstable flow due to plugs of liquid. Finally, the sensors are arranged in series causing a large fluid flow in each sensor. The implementation of industrial concentration sensors is complex. Existing sensors pivot around an axis beneath the parabolic mirror or coinciding with the center of mass, Solar parabolic trough, https://www.eere.energy.gov/troughnet / pdfs / solar trouqh.pdf, 1996-2006]. As a result, the collector pipe must rotate with the mirror and must be connected by hoses or rotating joints to the water supply and vapor collection network. Tower sensors are another type of concentration sensor, in which steerable mirrors converge the reflected rays at the top of a tower where the absorbent element is located. Used in semi industrial plants such as the Odeillo solar furnace or the Themis plant [B. Rivoire, Solar thermodynamics, in The energy of tomorrow, edited by JL Bobin, E. Huffer and H. Niffenecker, EDP Sciences, Les Ulis, France, 2005], this principle allows to reach even higher temperatures approaching 800 C, but it seems more expensive, because it is necessary to operate the mirrors in two degrees of freedom and the problem of heat transfer fluid (molten salts or molten metal) is more difficult. Application of concentrating solar collectors in the oil field The use of solar energy in the petroleum sector is cited in US Pat. No. 5,058,675 which describes the use of concentrating solar collectors for the production of oil shale. The patent applications US 2003 / 0111223A1, US2003 / 0196810A1, and WO 02/085821A2 describe the enhanced recovery of heavy crudes by mentioning schematically the use of solar collectors at solar concentration. In view of the SAGD, the particular conditions define a specific optimum to be determined. This optimum does not only concern the sensors, but the entire process, and it must therefore also integrate aspects such as the recovery of the thermal energy of the fluids produced, the storage of energy or the arrangement of the sensors.

  Indeed, the use of solar energy as a source of steam production poses a number of difficulties, in particular due to the dispersed and intermittent nature of solar energy, in addition to the technical constraints related to the sensors themselves.

  If we put aside the inequality of sunshine according to geographical areas, the difficulties to be overcome for the use of solar energy for the assisted recovery of heavy crudes are of several types.

  A first difficulty lies in the dispersed nature of solar energy (maximum of about 1 kW / m2 at ground level due to good sunlight), which requires the provision of large sensor surfaces and therefore a high level of investment. If one applies the conversion efficiencies of the solar energy in thermal energy found in the USA and the average quantities of energy necessary for the production by SAGD, one comes to the conclusion that each square meter of sensor authorizes the production of about 1.5 barrels of heavy crude per year. For a project of industrial size (20000 barrels / day) the required sensor area is therefore of the order of 5 km2, which would occupy a floor area of 7-8 km2. These surfaces are important, but nevertheless realistic compared to areas devoted to other energy sectors such as hydroelectric dams for example. Because of the extent to be expected, the reduction of the cost of the concentration sensors is of particular importance for the economics of the process.

  A second difficulty is the intermittent nature of solar energy, which is available in the best cases for a third of the time. At the beginning of the operation, when the steam chamber is still not very developed, the interruption of the steam injection results in a rapid drop in pressure and a condensation of the steam in the chamber, these phenomena counteracting the production. higher. Of course, another source of energy (gas, oil) can be envisaged during periods without sun, but this reduces the expected benefits of the process. It is therefore useful to consider the storage possibilities of the energy produced during sunny periods to supply the process in the hours or days that follow. Another problem posed by the intermittent nature of steam production is the recovery of thermal energy from fluids produced outside periods of sunshine. The solution of storing this thermal energy (gravel bed for example) is certainly possible but expensive, and allows to continue to produce steam only for a few hours after the end of sunshine. The present invention proposes to remedy in particular these two main groups of disadvantages: -Optimization of the cost and performance of parabolic trough sensors for use in assisted recovery of heavy crudes by the technique of steam injection. - Adaptation of the assisted recovery of heavy crudes by steam injection to the intermittent nature of solar energy by the use of a reservoir already exploited as heat storage and by an optimized production rate. SUMMARY OF THE INVENTION The optimized method for assisted recovery of heavy crudes by the steam injection technique, in particular of the SAGD type, comprises the following steps:

  we generate steam from a set of solar collectors,

  said vapor is injected into at least a first zone of

  production of a reservoir and jointly in at least a second

  zone, there are means for communicating the steam between said two zones, using said communication means to regulate the injection of steam between the zones. In a preferred embodiment, the production area is a SAGD chamber. Preferably, said second zone is adapted to be a storage of the steam. Advantageously, the injection of steam is regulated from the second zone during the night phase. In the method according to the invention there can be communications between the steam injection drains, underground drilling or surface. The first production zone and the second zone may be located in the same reservoir or in different reservoirs. Preferably, in the optimized method for assisted recovery of heavy crudes according to the invention, the sensors are inclined and arranged in parallel. Very preferably, the sensors are optimally arranged according to the terrain, the input points of the sensors connected in parallel being located in the same horizontal plane. It is also possible to carry out a hydraulic control to adapt the flow of fluid to the variable thermal power delivered by a set of sensors arranged in parallel. At the beginning or end of the day, the method according to the invention advantageously provides to turn only one sensor out of two towards the sun, the other sensors being arranged so as to minimize the drop shadow. The invention also relates to an optimized system for assisted recovery of heavy crudes by the steam injection technique, in particular of the SAGD type, which comprises: a set of solar collectors for the generation of steam, injection means of steam in at least a first production zone of a reservoir and in at least a second zone, means of communication between the steam injection means of said two zones, means for regulating the injection of the steam between the areas. Preferably, the installation is of the SAGD type. In said installation, the solar collectors are preferably sensors with cylindrical-parabolic concentration, inclined and arranged in parallel. The solar collectors are preferably fixed collector, the parabolic mirror pivoting about the axis of the collector tube so as to leave it rigorously fixed. The installation may include a differential pressure sensor between the steam manifold and the water supply piping and a servo system controlling the flow of liquid water injected as a function of the measured pressure difference. DETAILED DESCRIPTION OF THE INVENTION Description of the optimized method for enhanced recovery of heavy crudes by the technique of steam injection using solar energy according to the invention The optimized method for enhanced recovery of heavy crudes by the injection technique Steam has the following steps:

  we generate steam from a set of solar collectors,

  said steam is injected into at least a first production zone of a reservoir and jointly in at least a second zone; steam communication means are provided between said two zones; said communication means are used to regulate the injection of steam between the zones. Preferably the production area is a SAGD chamber. Preferably, said second zone is adapted to be a storage of the steam. Advantageously, the injection of steam is regulated from the second zone during the night phase. In the method according to the invention there can be communications between the steam injection drains, underground drilling or surface. Preferably, in the optimized method for assisted recovery of heavy crudes according to the invention, the sensors are inclined and arranged in parallel. FIGS. 2A and 2B illustrate the invention in a non-limiting way and describe the use of a tank already operated as heat storage in a SAGD type system. In the optimized method for assisted recovery of heavy crudes by the technique of steam injection (SAGD) using solar energy according to the invention, the production of steam is carried out by direct generation in solar collectors and adapted to the intermittent nature. solar energy in that one uses a tank already exploited as storage of heat. 1st phase: During periods of good sunlight (Figure 2-A), the chamber (2 ") acting as storage is supplied with steam by the sensor field (7). 2nd phase: During non-sunny periods (figure 2-B), we can consider letting the steam of this chamber join one (or more) smaller chamber (s) as they exist at the beginning of operation ( 2 '), in order to limit the pressure drop 9 and the condensation that would occur therein without storage. This storage does not require any specific installation and the thermal inertia of the tanks at the end of operation is sufficient to allow a supply of steam over periods of hours or even days. In the optimized method for assisted recovery of heavy crudes according to the invention, the production rate is advantageously adapted to the recovery of the thermal energy in that: • the lower well (5 ', 5 ") operates in a manner intermittent during the periods when the water for steam production is required to be preheated by means of the exchanger (10), • the condensed liquid water and the heated crude oil accumulate in the bottom of the chamber spraying (4 ', 4 ") during non-sunny periods, • the flow of products (8) varies according to the flow of cold water supply (9). It can indeed be envisaged to leave the lower well (5 ', 5 ") to produce only during the periods during which it is necessary to preheat the water intended for the production of steam by means of the exchanger (10). This amounts to allowing condensed liquid water and warmed crude oil to accumulate in the bottom of the vaporization chamber (4 ") during non-sunny periods (Figure 2-B). This solution avoids the need for specific heat storage to store the thermal energy of the fluids produced while waiting for solar energy to produce steam. Moreover, the method of assisted recovery of heavy crudes by the optimized steam injection technique according to the invention allows a use of solar energy in a complementary and progressive manner during operation. Alternative 1: Additional use of solar energy

  We can consider using solar energy in addition to conventional energy sources (gas, oil) to produce steam. With an average of 6 hours of sunshine a day, the use of solar energy saves 25% of the fuels and CO2 treatment plants needed.

  Variant 2: Gradual use of solar energy during operation The use of solar energy as a supplement is particularly attractive at the beginning of operation, when a reservoir is not yet available to ensure heat storage and when we have not yet installed the entire sensor field. Indeed, the solar power needed to power the SAGD for example in addition to a fossil fuel is only a quarter of the total power, and therefore only a quarter of the sensor area needed for an exclusively solar SAGD (approximately 1.25 km2 for a production of 20 000 barrels / day). In a second phase, the field of sensors can be extended to increase the rate of coverage of needs by solar energy, taking advantage of the operating statistics of the first phase to better size the extension of the sensor field. Preferably, the steam is generated directly in inclined concentration solar collectors. Preferably, the solar energy is produced by means of solar collectors arranged in parallel. Very preferably, the solar collectors are fixed collector, the parabolic mirror pivoting about the axis of the collector tube so as to leave it rigorously fixed. Optimal arrangement of the sensors according to the terrain For direct steam generation in particular, it is advantageous for the input points of the sensors connected in parallel to be located in the same horizontal plane so that the liquid level is identical in the different collecting tubes. . In the case of terrains having good flatness, it will be advantageous to arrange the row of sensors in parallel along an east-west axis, in order to minimize the length of piping. In the case of lands with significant slopes, it will be advantageous to have the sensors of the same row along a contour to avoid large earthworks. Hydraulic control

  Preferably, a hydraulic control is carried out to adapt the flow of fluid to the variable thermal power delivered by the sensor train, a servo system controlling the flow of liquid water injected as a function of the measured pressure difference (by example by means of a controlled valve).

  The set value is set to shApg where e is a number between zero and 1, h is the difference in level between the input and the output of the sensor, Ap is the difference in density between the liquid and the vapor, and g is the acceleration of gravity. Depending on the value of the parameter e, it is possible to produce steam that is slightly overheated (e close to unity) or strongly superheated (values lower than e). In such a system, the steam outlet can be controlled by pressure (again by means of a controlled valve), which makes it possible to control the temperature since it is established so that the saturation vapor pressure is equal to the deposit. In a system designed for low pressure losses, the risk of incomplete vaporization of the water can thus be avoided. Operation at the beginning and end of the day At the beginning and at the end of the day the sun is low on the horizon and the sensors are shaded mutually, and the amount of radiation arriving on each sensor is no longer sufficient to reach the temperature of 250-300 C necessary for the SAGD. Consequently, the optimized method for assisted recovery of heavy crudes according to the invention advantageously provides for turning only one sensor (12A) out of two towards the sun (FIG. 5), the others being arranged so as to minimize the drop shadow ( 12B). In this way the incident radiation flux is increased on the active sensors (12A), which can vaporize the water at a higher temperature. In a set of sensors connected in parallel, the liquid level rises in the non-sunny sensors (12B), which interrupts the flow. The fluid flow is thus concentrated in the 12 sensors receiving the most radiation. The flow thus obtained is restricted, but the fluid is at the desired temperature and pressure. The present invention also relates to an optimized system for the assisted recovery of heavy crudes by the steam injection technique comprising a set of solar collectors for the steam generation. , steam injection means in at least a first production zone of a reservoir and in at least a second zone, communication means between the steam injection means of said two zones, and control means the injection of steam between the zones by means of concentrating solar collectors, where the solar collectors are preferably inclined cylindricoparabolic sensors arranged in parallel. Preferably, the installation is of the SAGD type. Direct Generation of Steam in Inclined Sensors The direct production of steam in the absorbent element of horizontally disposed cylindroparabolic sensors is difficult to implement because of the creation of plugs and necessitates a liquid-vapor separation at the output of solar collectors.

  The present invention contemplates tilting the axis (13) of the sensor (12) by a moderate angle (for example between 5 and 10) to ensure this separation in the sensor itself, thus avoiding the plugs of liquid in the manifold (14) of steam (Figure 3-A). An inclination of a few degrees remains compatible with the desirable length of a cylindrical-parabolic sensor (a few tens of meters) without significantly burdening installation costs.

  Indeed the upper part is raised a few meters at most (for example, elevation of 3 meters for a sensor 30 m long inclined 5). The present invention contemplates a parallel arrangement of the sensors (12) (and the collecting tubes (13)), the liquid arriving through the liquid supply piping (II) and the vapor emerging through a piping output (14) (Figure 3-B). This makes it possible to reduce the flow of fluid in each sensor and thus to facilitate gravity segregation of the vapor bubbles with a slight inclination. This arrangement also has the advantage of distributing the flow as best as possible if the sensors do not all deliver the same thermal power. Indeed the vaporization will be lower in a lower power sensor, resulting in a higher liquid level and therefore an additional obstacle to the flow. A brief sizing calculation shows that the liquid velocities to be expected in a collector of average diameter (5-6 cm) are of the order of one centimeter per second for a sensor 30 meters long by good sunshine, those of steam being of the order of twenty centimeters per second. These speeds are low enough to prevent the steam from driving the liquid (or vice versa). Simplified mechanical design with a fixed collector In order to simplify the system, the present invention advantageously provides a device allowing (FIG. 4 A) to rotate the parabolic mirror (12) around the axis of the collector tube (13) so as to leave the latter rigorously fixed. The absence of moving joints greatly reduces the costs and risks of failure. In, the SAGD device according to the invention, the sensors are fixed collector, the parabolic mirror (12) pivoting about the axis of the collector tube (13) so as to leave it rigorously fixed.

  This rotation movement of the mirror can be obtained for example (FIG. 4-A) by means of a half-ring support (15) of circular shape, centered on the collector tube, resting on bearing rollers ( 16). Holding rollers (17) are also conceivable to ensure a good awning all of the assembly.

In another embodiment (FIG. 4-B), the parabolic mirror (12) could be suspended from bearings (19) located around the collecting tube (13) by means of spacers (18), the collector tube being supported by porticoes (20) from place to place. Hydraulic control Preferably, to adapt the fluid flow rate to the variable thermal power delivered by a set of sensors arranged in parallel, the installation comprises a differential pressure sensor between the steam collector (14) and the supply piping in water (11) and a servo system controlling the flow of liquid water injected as a function of the measured pressure difference (AP) (for example by means of a controlled valve). Figure 3B illustrates this mode of operation without limitation. 15

Claims (15)

  1. Optimized method for enhanced recovery of heavy crudes by the steam injection technique, characterized in that it comprises the following steps: steam is generated from a set of solar collectors (7), injected said vapor in at least a first production zone (2 ') of a reservoir (3) and jointly in at least a second zone (2 "), there are means for communicating the steam between said two zones; said communication means for regulating the injection of steam between the zones.   The method of claim 1 wherein the production zone (2 ') is a SAGD chamber.   3. Method according to claims 1 or 2 wherein said second zone (2 ") is adapted to be a storage of steam.   4. Method according to claims 1 to 3, wherein the steam injection is regulated from the second zone (2 ") during the night phase.   5. Method according to one of the preceding claims, wherein there is communication between the steam injection drains (1 ') and (1 ") underground drilling or surface.   6. Method according to one of the preceding claims wherein the first zone (2 ') and the second zone (2 ") are located in different tanks.   7. Optimized method of assisted recovery of heavy crudes according to one of the preceding claims wherein the sensors (12) are inclined relative to the horizontal and are arranged in parallel.   8. Optimized method of enhanced recovery of heavy crudes according to claim 7 wherein the sensors are optimally disposed according to the terrain, the input points of the sensors connected in parallel being located in the same horizontal plane.   9. Optimized method for enhanced recovery of heavy crudes according to one of claims 7 or 8 in which a hydraulic control is carried out to adapt the flow of fluid to the variable thermal power delivered by a set of sensors (12) arranged in parallel.   10. Optimized method for enhanced recovery of heavy crudes according to one of the preceding claims wherein only one sensor rotates (12A) out of two towards the sun at the beginning or end of the day, the other sensors (12B) being arranged to minimize the drop shadow.   11. Optimized system for enhanced recovery of heavy crudes by the steam injection technique, characterized in that it comprises: a set of solar collectors for steam generation (7), steam injection means (1) '), (1 ") in at least a first production zone (2') of a reservoir (3) and in at least a second zone (2"), communication means between the injection means of the vapor of said two zones, means for regulating the injection of steam between the zones.   12.Installation optimized assisted recovery of heavy crudes by the steam injection technique according to claim 11 of the SAGD type.   13.Installation optimized assisted recovery of heavy crudes by the steam injection technique according to claim 11 or 12 wherein the solar collectors are cylindricoparabolic concentration sensors (12) inclined and arranged in parallel.   14.Installation optimized assisted recovery of heavy crudes by the steam injection technique according to one of claims 11 to 13 wherein the sensors are fixed collector, the parabolic mirror (12) pivoting about the axis of the tube manifold (13) so as to leave it rigorously fixed.   15.Installation optimized assisted recovery of heavy crudes by the steam injection technique according to one of claims 11 to 14 comprising a differential pressure sensor (AP) between the steam collector (14) and the supply piping in water (11) and a servo system controlling the flow of liquid water injected as a function of the measured pressure difference. 17