Method for improving recovery efficiency in middle and later periods of SAGD (Steam Assisted Gravity Drainage) of heterogeneous super heavy oil reservoir and injection-production well pattern

Abstract

The invention provides a method for improving the recovery ratio in the middle and later periods of SAGD (Steam Assisted Gravity Drainage) of a heterogeneous super heavy oil reservoir and an injection-production well pattern. The method comprises the steps that steam is injected after circulating preheating is conducted on an SAGD well pair, and after huff-puff preheating and electric heating preheating are conducted on an electric heating horizontal well, long-pipe steam injection and short-pipe oil extraction are conducted; when the recovery degree is 30-35%, a catalytic modifier is injected into the electrically-heated catalytic modification branch well, non-condensate gas is injected into the injection well of the SAGD well pair in an accompanying mode, the injection amount of the non-condensate gas is increased while the steam injection amount is gradually reduced according to a set proportion, and the injection amount of the non-condensate gas is increased while the steam injection amount is gradually reduced according to the set proportion; the ground volume ratio of the injection amount of the steam to the injection amount of the non-condensate gas reaches a preset ratio; the electric heating horizontal well is converted into continuous oil extraction, and electric heating auxiliary production is carried out; when the recovery degree is 55-60%, reducing the water equivalent steam with the preset mass, and additionally injecting non-condensate gas until gas drive is converted; and in the gas injection oil extraction production stage, non-condensate gas is continuously injected till the yield reduction value of the SAGD well pair is the lowest yield threshold value.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal oil production, and in particular relates to a method for improving the recovery rate of a heterogeneous super-heavy oil reservoir SAGD in the middle and late stages and an injection-production well network. Background Art

[0002] Extra heavy oil has low light component content, high colloid and asphaltene content, and has the characteristics of high viscosity, high density and poor fluidity. my country has relatively rich heavy oil resources, and the current proven heavy oil resources are 19.87 billion tons. The distribution of my country's heavy oil resources is controlled by the Alpine tectonic domain and the Pacific Rim tectonic domain, and is mainly distributed in the eastern and western regions. Most of my country's heavy oil resources are continental deposits of the Mesozoic and Cenozoic eras, and a small amount is marine deposits of the Paleozoic era. The reservoir is mainly clastic rock, with high porosity, high permeability and loose cementation. More than 70 heavy oil fields have been discovered in basins such as the Songliao Basin, Junggar Basin, Tarim Basin, and Tuha Basin. The Liaohe Oilfield in the northeast has the largest reserves of heavy oil, followed by the Shengli Oilfield in the east and the Karamay Oilfield in Xinjiang in the northwest. my country's heavy oil reservoirs are characterized by continental deposition, serious oil layer heterogeneity, complex geological structure, and many reservoir types.

[0003] Super heavy oil plays an important role in high-end products, such as high-end lubricants. In recent years, my country's dependence on foreign oil has increased, requiring domestic super heavy oil production to continue to improve and increase production. Super heavy oil SAGD development technology has entered the industrial development stage, and many oil reservoirs have entered the middle and late stages. How to achieve safe and efficient recovery in the middle and late stages of SAGD is one of the urgent problems to be solved in this field. Summary of the invention

[0004] In order to improve the recovery factor of heterogeneous super heavy oil reservoirs in the mid-to-late stage SAGD development, the embodiment of the present invention provides a method for improving the recovery factor of heterogeneous super heavy oil reservoirs in the mid-to-late stage SAGD and an injection-production well pattern.

[0005] To achieve the above purpose, the technical solution proposed by the present invention is as follows:

[0006] In a first aspect, an embodiment of the present invention provides a method for improving oil recovery in a heterogeneous super-heavy oil reservoir in the middle and late stages of SAGD, comprising:

[0007] Deploy the injection and production well network: intensify the electrically heated horizontal wells on both sides of the SAGD well pair, and intensify the electrically heated catalytic reformed multi-branch wells on the top of the SAGD well pair;

[0008] SAGD production stage: After the SAGD well pair is circulated and preheated, steam is injected to switch to the cavity expansion production stage, and the electrically heated horizontal well is preheated by huff and puff and electrically heated to switch to long-tube steam injection and short-tube oil production;

[0009] GCEASAGD production stage: when the recovery degree is 30-35%, inject catalytic modifier into the electrically heated catalytic modification branch well, inject non-condensable gas into the injection well of the SAGD well pair, reduce the steam of preset mass of water equivalent in unit cycle time, gradually reduce the steam injection amount according to the set ratio while increasing the injection amount of non-condensable gas, until the surface volume ratio of the steam and non-condensable gas injection amounts reaches the preset ratio;

[0010] When the steam chamber of the SAGD well pair is connected to the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is switched to continuous oil production, and electrically heated assisted production is performed; when the recovery degree is 55-60%, the steam of a preset mass of water equivalent is reduced within a unit cycle time, and the injection of non-condensable gas is increased, and the increase in the amount of injected non-condensable gas is controlled to be a preset multiple interval of the reduction in the amount of steam, until switching to gas drive;

[0011] Gas injection and oil production stage: non-condensable gas is continuously injected to utilize the waste heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to the minimum production threshold, and production is terminated.

[0012] In one or some optional embodiments, the method of adding electrically heated horizontal wells on both sides of the SAGD well pair and adding an electrically heated catalytic reformed multi-branch well on the top of the SAGD well pair includes:

[0013] The electrically heated horizontal wells are respectively intensified at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the distance between the two electrically heated horizontal wells is a first distance range;

[0014] The electrically heated catalytically modified multi-branch wells are densely populated at a second distance range between the top of the SAGD well pair and the top of the oil layer. The branch lengths of the electrically heated catalytically modified multi-branch wells are within the second length range. The branch directions are the four corners of the oil layer and can cover at least one of the SAGD well pairs.

[0015] In one or some optional embodiments, the injection rate of the catalytic modification agent into the electrically heated catalytic modification branch well is 1% to 5% of the crude oil production rate.

[0016] In one or some optional embodiments, the catalytic modifier is:

[0017] Taking the total mass of the catalyst fluid as 100wt%, 10wt% to 50wt% of toluenesulfonyl hydrazide and hydrazine hydrate, 10wt% of at least one of tetralin, tetralone and decalin, 5wt% of coking inhibitor, and the rest being oil phase solvent, the catalyst fluid and water mixed in a mass ratio of 9:1.

[0018] In one or some optional embodiments, the coking inhibitor includes at least one of a sulfur-containing compound, a phosphorus-containing compound, an organic sulfur-phosphorus compound, a metal organic compound, a metal inorganic salt or oxide, a rare earth compound, a boron compound, and an organic polysiloxane sulfide.

[0019] In one or some optional embodiments, the heating temperature of the electrically heated catalytic reforming branch well is 240°C to 260°C.

[0020] In one or some optional embodiments, the electric heating power for electric heating assisted production of the electric heating horizontal well is 1000-1500 W / m.

[0021] In one or some optional embodiments, when the recovery degree is 55-60%, the initial velocity of the injected non-condensable gas is 4000-8000 m / s. 3 / d.

[0022] In one or some optional embodiments, during the gas injection oil production stage, the continuous non-condensate gas injection rate is 15000-35000 m / s. 3 / d.

[0023] In one or some optional embodiments, the non-condensable gas includes at least one of methane and nitrogen.

[0024] In a second aspect, an embodiment of the present invention provides an injection-production well pattern for improving the recovery rate of a heterogeneous super-heavy oil reservoir in the middle and late stages of SAGD, comprising:

[0025] A SAGD well pair, electrically heated horizontal wells located on both sides of the SAGD well pair, and an electrically heated catalytically upgraded multi-branch well located on top of the SAGD well pair;

[0026] In the SAGD production stage, the SAGD well pair is used for circulation preheating, and then steam is injected to switch to the cavity expansion production stage; the electrically heated horizontal well is used for preheating by huff and puff and electric heating, and then switched to long-tube steam injection and short-tube oil production;

[0027] In the GCEASAGD production stage: when the recovery degree is 30-35%, the electrically heated catalytic reforming branch well is used to inject catalytic reforming agent, and the injection well of the SAGD well pair is used to inject non-condensable gas, reducing the steam of a preset mass of water equivalent in a unit cycle time, gradually reducing the steam injection amount according to the set ratio while increasing the injection amount of non-condensable gas, until the surface volume ratio of the steam and non-condensable gas injection amounts reaches the preset ratio;

[0028] When the steam chamber of the SAGD well pair is connected to the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is used to switch to continuous oil production and perform electrically heated assisted production; when the recovery degree is 55-60%, the injection well of the SAGD well pair is used to reduce the steam of a preset mass of water equivalent within a unit cycle time, and increase the injection of non-condensable gas, and control the increase in the amount of injected non-condensable gas to be a preset multiple interval of the reduction in the amount of steam, until switching to gas drive;

[0029] In the gas injection and oil production stage: the injection well of the SAGD well pair is used to continuously inject non-condensable gas to utilize the waste heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to a minimum production threshold, thereby terminating production.

[0030] In one or some optional embodiments, the electrically heated horizontal wells are respectively located at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the well spacing between the two electrically heated horizontal wells located on the left and right sides of the SAGD well pair is a first distance range;

[0031] The electrically heated catalytically modified multi-branch well is located at the top of the SAGD well pair at a second distance range from the top of the oil layer. The branch length of the electrically heated catalytically modified multi-branch well is within the second length range. The branch direction is the four corners of the oil layer, and it can cover at least one of the SAGD well pairs.

[0032] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0033] The method for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD is provided in an embodiment of the present invention. The improved SAGD well pattern containing densely electrically heated horizontal wells and electrically heated catalytically modified branch wells is adopted to provide a production operation method corresponding to three stages, and the key operation points and conversion timing of the three oil production stages of SAGD cavity expansion production, GCEASAGD, and gas injection enhanced oil production are strengthened. The gradual transition of each stage is conducive to the stability of the steam chamber; the coordinated operation of gas-assisted cavity expansion, catalytically modified branch wells and electrically heated horizontal production wells is proposed, which is helpful to accelerate the expansion of the steam chamber, reduce the viscosity of heavy oil and increase the oil production rate; the injection of gas in the late stage effectively utilizes the waste heat of the steam chamber, realizes the recycling of gas, achieves the effect of energy saving and carbon reduction and cost saving, and improves the production effect of the whole SAGD process.

[0034] The method for improving the recovery rate of the SAGD mid-to-late stage of heterogeneous super-heavy oil reservoirs provided by the embodiment of the present invention adopts an improved SAGD well network structure, which is conducive to accelerating mid-to-late stage oil production while saving energy and reducing carbon dioxide emissions. An electrically heated horizontal well is intensified on both sides of the SAGD well pair, which is beneficial to mobilizing the residual oil at the edge, while quickly increasing the oil production rate and increasing the controlled reserves of the well pair; an electrically heated catalytically modified branch well is intensified on the upper part of the SAGD well pair, which is beneficial to reducing the residual oil saturation of the reservoir, improving the oil production rate and the final recovery rate. The SAGD well pair, the electrically heated horizontal well and the electrically heated catalytically modified branch well are put into production at the same time, and the simultaneous arrangement of the branch wells reduces the risk of steam leakage in the intensified branch wells in the mid-to-late stage. The combination of multiple enhanced oil production measures to increase the oil production rate of the entire stage also achieves the effect of reducing carbon and energy. The layout position of the catalytically modified branch well conforms to the migration law of steam, strengthens the utilization of the heat in the steam chamber, and reduces the viscosity of the super-heavy oil.

[0035] The method for improving the recovery rate of heterogeneous super-heavy oil reservoir SAGD in the middle and late stages provided by the embodiment of the present invention first accelerates the establishment of the connection of two large and one small steam chambers through steam throughput and electric heating assistance, and accelerates the exploitation of super-heavy oil through catalytic modification branch wells and gas-assisted SAGD in the middle stage of development. After the steam chamber expands to the top, the SAGD well pair adopts catalytic modification agent to assist production, and after the steam chamber expands to the top boundary, the SAGD well pair adopts non-condensable gas to assist production. The non-condensable gas reduces Subcool and gathers at the top of the steam chamber to form an insulation layer, reducing the heat loss of the steam chamber during the exploitation process, stabilizing the production rate and improving the oil-gas ratio to a certain extent; at the same time, the catalytic modification agent injected into the top catalytic modification branch well, under the displacement and diffusion of non-condensable gas and steam, fully reacts with the super-heavy oil by using the heat of the steam chamber, achieving the effect of in-situ modification of super-heavy oil and reducing the viscosity of crude oil, further improving the oil recovery rate, and playing an effective role in the mobilization of residual oil. Heated horizontal wells assisted SAGD production can effectively exploit the residual oil between wells, and the final recovery rate can reach more than 65%.

[0036] The method for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD provided by the embodiments of the present invention, the injection of catalytic modifiers in the middle stage of development, and the use of densely packed electric heating production wells effectively speed up the oil production rate, mobilize the remaining oil in the triangular zone at the edge of the steam chamber, and reduce the residual oil saturation. The large-scale injection of gas in the late stage of development fully utilizes the waste heat of the steam chamber to ensure the continuous production of SAGD in the late stage. It is conducive to improving the oil production rate in the middle and late stages of development while improving the final recovery rate.

[0037] The SAGD mid- and late-stage recovery method for heterogeneous super-heavy oil reservoirs provided by the embodiment of the present invention uses non-condensable gas, catalytic modifier and electric heating, which reduces the use of steam by 20% and reduces the emission of carbon dioxide. With the large amount of gas injected in the late stage, 80-90% of the gas can be recovered and utilized again, reducing the cost per ton of oil. It is low-carbon and environmentally friendly while reducing costs.

[0038] The method for improving the recovery rate of a heterogeneous super-heavy oil reservoir in the middle and late stages of SAGD provided in an embodiment of the present invention adopts a novel catalytic modifier. Toluenesulfonyl hydrazide (TSH) and hydrazine hydrate (HH) are added to the catalytic modifier, which can accelerate the reaction rate at the same temperature and effectively realize the catalytic modification of super-heavy oil.

[0039] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 A schematic flow chart of a method for improving oil recovery in a heterogeneous super-heavy oil reservoir SAGD in the middle and late stages provided by an embodiment of the present invention;

[0043] Figure 2 An improved well pattern distribution diagram of a heterogeneous super-heavy oil reservoir SAGD provided by an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the SAGD cavity expansion production stage assisted by an electrically heated horizontal well in an embodiment of the present invention;

[0045] Figure 4 Schematic diagram of the connection between steam and air cavity of electrically heated horizontal well assisted SAGD in an embodiment of the present invention;

[0046] Figure 5 Schematic diagram of the steam (gas) chamber in the GCEASAGD stage in an embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of the gas cavity in the gas injection stage in the later stage of the embodiment of the present invention;

[0048] Figure numbers: 1 is a production horizontal well of the SAGD well pair, 2 is an injection horizontal well of the SAGD well pair, 3 is an electrically heated horizontal well, and 4 is an electrically heated catalytic reforming branch well. DETAILED DESCRIPTION

[0049] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0050] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of methods consistent with some aspects of the present invention as detailed in the appended claims.

[0051] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0052] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] Glossary:

[0054] Heterogeneous super-heavy oil reservoir: crude oil viscosity at 50°C is greater than 50,000 mPa·s, porosity is greater than 0.28, permeability is greater than 1,000 mD, oil layer depth is 150-1,600 m, oil layer thickness is greater than 10 m, and heterogeneity coefficient is less than 1.5.

[0055] SAGD: Steam is injected to reduce the viscosity of the super-heavy oil in the formation. The mobile crude oil after viscosity reduction is produced using gravity as the driving force.

[0056] GCEASAGD: A technology developed by using gas-catalyst-electric heating to assist SAGD.

[0057] Subcool: refers to the difference between the saturated steam temperature corresponding to the bottom hole pressure of the horizontal production well and the bottom hole fluid temperature of the horizontal production well. It reflects the height of the vapor-liquid interface between the injection and production wells and is an important parameter for measuring the development effect and control level of the SAGD injection and production wells.

[0058] The inventors found that when the super-heavy oil reservoir enters the middle and late stages, there are the following development difficulties: ① The viscosity of super-heavy oil is high, and conventional thermal recovery technology consumes a large amount of steam, resulting in poor recovery of heavy oil; ② Due to the large heterogeneity of the oil layer, the heat loss of the steam chamber increases in the middle and late stages, the oil-gas ratio and daily oil production decrease, the water content increases, and there is a lot of unused residual oil between wells. For the problems faced, on the one hand, it is necessary to effectively reduce the viscosity of super-heavy oil and increase the fluidity of crude oil, and on the other hand, it is necessary to improve the thermal utilization rate of steam to achieve the role of "green and low-carbon recovery" in the middle and late stages of super-heavy oil development. Conventional thermal recovery technology is applied to heterogeneous super-heavy oil reservoirs, but the oil-gas ratio is low, the production declines rapidly, and the effect of improving the recovery rate is limited. After further research and development, the inventor provides a method and injection-production well network for improving the recovery rate in the middle and late stages of SAGD for heterogeneous super-heavy oil reservoirs, which integrates electric heating horizontal well technology, catalytic upgrading technology, branch well technology, and gas-assisted SAGD technology. The method can greatly improve the recovery rate in the middle and late stages of super-heavy oil development, effectively utilize the remaining oil in super-heavy oil reservoirs, and improve the steam dryness and steam drive efficiency. The comprehensive enhanced oil recovery method solves the problem of poor utilization effect and low utilization degree of heterogeneous super-heavy oil reservoirs.

[0059] The embodiment of the present invention provides a method for improving the recovery rate of a heterogeneous super-heavy oil reservoir SAGD in the middle and late stages, referring to Figure 1 As shown, the method includes:

[0060] S101: Deploy an injection-production well network: Add more electrically heated horizontal wells on both sides of the SAGD well pair, and add more electrically heated catalytically modified multi-branch wells on the top of the SAGD well pair.

[0061] In the above step S101, electrically heated horizontal wells are added on both sides of the SAGD well pair, and an electrically heated catalytic reformed multi-branch well is added on the top of the SAGD well pair, specifically including:

[0062] The electrically heated horizontal wells are respectively intensified at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the distance between the two electrically heated horizontal wells is a first distance range;

[0063] The electrically heated catalytically modified multi-branch wells are densely populated at a second distance range between the top of the SAGD well pair and the top of the oil layer. The branch lengths of the electrically heated catalytically modified multi-branch wells are within the second length range. The branch directions are the four corners of the oil layer and can cover at least one of the SAGD well pairs.

[0064] In a specific embodiment, the preset specific range may be 40-50 meters, the first length range may be 200-300 meters, the first distance range may be 80-100 meters, and the second length range may be 50-200 meters. Figure 2 As shown, two electrically heated horizontal wells 3 are added beside the SAGD well pair, and the electrically heated horizontal well 4 is parallel to the SAGD well pair, with a horizontal distance of 40 to 50 m. The length of the electrically heated horizontal well 3 is 200 to 300 m, and the well spacing is 80 to 100 m. An electrically heated catalytic modified multi-branch well 4 is added on the top of the SAGD well pair, with a branch length of 50 to 200 m, and branch directions of the four corners of the oil layer. The electric heating power is 1000 to 1500 W / m, and it is located 2 to 5 m below the top of the oil layer, which can cover one or more SAGD well pairs.

[0065] The method for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD provided by the embodiments of the present invention has controllable safety risks. In the early stage of oil field development, SAGD horizontal well pairs, densely packed horizontal wells with electrical heating, and catalytic reforming branch wells are arranged to avoid the risk of steam and other gas leakage in the dense well network in the middle and late stages.

[0066] S102: SAGD production stage: After cyclic preheating of the SAGD well pair, steam is injected to switch to the cavity expansion production stage, and the electrically heated horizontal well is preheated by huff and puff and electrically heated to switch to long-tube steam injection and short-tube oil production;

[0067] S103: GCEASAGD production stage: When the recovery rate is 30-35%, the catalytic modifier is injected into the electrically heated catalytic modification branch well, and the non-condensable gas is injected into the injection well of the SAGD well pair, and the steam injection amount is gradually reduced according to the set ratio while the injection amount of non-condensable gas is increased until the ground volume ratio of the steam and non-condensable gas injection amounts reaches the preset ratio.

[0068] In an embodiment of the present invention, the heated catalytically modified branch well can be put into use when the recovery rate is 30-35%. During this stage, the daily oil production decreases, the oil-gas ratio decreases, the water content increases, the steam chamber expands horizontally to the maximum, and begins to enter the decline stage. Catalytic modifiers are added through the catalytically modified branch wells. The injection speed of the catalytic modifiers is determined according to the rate of crude oil production. The injection speed of the catalytic modifiers added to the electrically heated catalytically modified branch wells is 1% to 5% of the crude oil production rate, that is, 10 to 50 kg of catalytic modifiers are injected for every ton of crude oil produced.

[0069] In the embodiment of the present invention, the above-mentioned catalytic modifier is: based on the total mass of the catalyst fluid as 100wt%, 10wt% to 50wt% of toluenesulfonyl hydrazide (TSH) and hydrazine hydrate (HH), 10wt% of at least one of tetralin (THN), tetralone, and decalin, 5wt% of coking inhibitor, and the rest is oil phase solvent, and the mass ratio of the catalyst fluid to water is 9:1.

[0070] In a specific embodiment, the coking inhibitor includes at least one of sulfur-containing compounds, phosphorus-containing compounds, organic sulfur-phosphorus compounds, metal organic compounds, metal inorganic salts or oxides, rare earth compounds, boron compounds and organic polysiloxane sulfides.

[0071] In a specific embodiment, the heating temperature of the electrically heated catalytic reforming branch well is 240°C to 260°C.

[0072] The catalytic modifier provided by the embodiment of the present invention: ① The reason for using toluenesulfonyl hydrazide (TSH) and hydrazine hydrate (HH) to achieve catalytic modification of crude oil: Toluenesulfonyl hydrazide (TSH) and hydrazine hydrate (HH) can easily react with crude oil to produce diimine through a large number of chemical reactions. As an intermediate molecule, diimine has a high tendency to attack double bonds and can effectively hydrogenate crude oil; diimine can undergo hydrogenation reaction under mild conditions of 240°C to 260°C, and such mild conditions can be achieved in oil reservoirs; light components generated by the reaction after hydrogenation of crude oil can dissolve and reduce viscosity with crude oil. ② Tetrahydronaphthalene (THN), tetralone and decahydronaphthalene reduce the viscosity of super-heavy oil, and can also act as solvents to dilute hydrocarbon macromolecular free radicals, reduce the chance of free radical collision, inhibit polymerization and coke formation, effectively break the C-S bonds and long carbon chains of heavy components, and make the reaction proceed in the direction of hydrodesulfurization, thereby reducing the molecular weight of heavy oil, reducing the asphaltene content, and reducing the viscosity of heavy oil. ③ The oil-soluble solvent can fully mix and react with the oil phase, effectively reducing the viscosity of the crude oil, enhancing the displacement effect of the super-heavy oil from the top of the oil layer to the production well, and reducing the residual oil saturation.

[0073] The present invention innovatively proposes adding a catalytic modifier branch well and a new catalytic modifier. A catalytic modifier branch well is added at the upper part of the SAGD well at a distance from the top of the oil layer, and the catalytic modification effect of the super-heavy oil is effectively improved by utilizing the migration law of steam. The proposed new catalytic modifier toluenesulfonyl hydrazine (TSH), hydrazine hydrate (HH) and other additives have the characteristics of low reaction temperature and easy to produce through a large number of chemical reactions, effectively reducing the viscosity of crude oil.

[0074] In an embodiment of the present invention, the unit cycle time may be days, and the preset mass of water equivalent may be 2 tons of water equivalent. After the injection wells of the SAGD well pair are injected with non-condensable gas, the injection wells of the SAGD well pair begin to enter the gas injection stage, and gradually reduce the proportion of steam, reducing 2 tons of water equivalent steam per day, and injecting a corresponding proportion of gas at the same time, and finally the ground volume ratio of the steam and gas injection amount is about 1:25.

[0075] In a specific embodiment, the non-condensable gas includes at least one of methane and nitrogen.

[0076] Gas-assisted SAGD in the embodiment of the present invention: ① Using a bare heat-insulated pipe or a bare oil pipe, while injecting steam into the pipe, continuously or in a slug-type manner injects gas into the annular space of the oil casing, which can play a heat-insulating role and reduce heat loss in the wellbore. At the same time, due to the gravity differentiation of the gas, the gas gathers at the top of the steam chamber, reducing heat loss and increasing the swept volume of the steam. ② Non-condensable gas has good expansion properties and can supplement the formation energy.

[0077] The electric heating technology used in the embodiment of the present invention can reduce the viscosity of crude oil, improve the fluidity of crude oil, reduce the injection pressure, and at the same time, increase the temperature of the catalytic modifier and accelerate the reaction rate with crude oil.

[0078] The mining method provided by the present invention first adopts the SAGD development technology and realizes enhanced mining in the middle and late stages. The synergistic effect of the mid-term non-condensable gas, catalytic modifier and dense electric heating production wells reduces the well spacing between SAGD well pairs, increases the mobilization reserves of SADG well pairs and the oil production rate of the whole process mining.

[0079] S104: when the steam chamber of the SAGD well pair is connected with the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is switched to continuous oil production and electrically heated assisted production is performed; when the recovery degree is 55-60%, the steam of a preset mass of water equivalent is reduced within a unit cycle time, and the injection of non-condensable gas is increased, and the increase in the amount of injected non-condensable gas is controlled to be a preset multiple interval of the decrease in the amount of steam, until switching to gas drive;

[0080] In the embodiment of the present invention, when the steam chamber of the SAGD well pair is connected with the steam chamber of the electrically heated horizontal well 3, the electrically heated horizontal well 3 stops long-tube steam injection and short-tube oil production and switches to continuous oil production operation, and at the same time, the electrically heated horizontal well 3 is electrically heated to assist production, and the electric heating power is 1000-1500W / m; when the recovery degree is 55-60%, 2t of water equivalent steam is reduced every day, and the initial velocity of the injected gas is 4000-8000m 3 / d, the increase in injected gas volume is 3 to 4 times the volume of reduced steam volume, and the amount of steam is gradually reduced to switch to gas drive.

[0081] The method for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD provided by the embodiment of the present invention adopts a method of intensifying production by gas and electric heating in the late stage of SAGD development. The large amount of gas injection replenishes the energy of the formation. Considering the characteristics of the steam chamber developing to the maximum and the high temperature in the late stage of SAGD, this measure fully utilizes the waste heat of the steam chamber while reducing heat loss, which can effectively displace the super-heavy oil, reduce the residual oil saturation of the pores to less than 5%, increase the available reserves, reduce the use of steam, and achieve the effect of reducing costs and energy saving and low carbon. The electrically heated production well replenishes the heat in the area near the production well, reduces the viscosity of the super-heavy oil, and improves the flowability of the crude oil.

[0082] S105: Gas injection and oil production stage: non-condensable gas is continuously injected to utilize the residual heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to a minimum production threshold, and production is terminated.

[0083] In a specific embodiment, in the above step S105, during the gas injection oil production stage, the continuous non-condensate gas injection rate is 15000-35000 m3 / d.

[0084] During the gas injection oil production stage, the densely-insulated electrically-heated horizontal wells can continuously produce oil and carry out electrically-heated assisted production. The electrically-heated catalytic modified branch wells can continuously inject catalytic modifiers and carry out electrically-heated assisted production to increase the utilization effect of the remaining oil.

[0085] In the embodiment of the present invention, the final injection gas injection speed is 15000~35000m 3 / d, 80-90% of the gas can be recovered and used again, using the waste heat of the steam chamber. Two electrically heated infill horizontal wells are located on both sides of the injection and production horizontal well pair, in the residual oil that is difficult to reach the steam chamber, increasing the mobility of the residual oil that is difficult to mobilize. When the production of the SAGD well pair drops to about 3t / d, that is, when there is no economic benefit, production is terminated.

[0086] The method provided by the present invention adopts a combination of multiple enhanced production methods in the SAGD production process, effectively improving the development effect of different stages, and at the same time providing transition marks of different stages, realizing a gradual transition of different stages. Catalytic modifiers assist SAGD to reduce the viscosity of super-heavy oil, gas-assisted SAGD oil production reduces heat loss and improves the oil-gas ratio, and horizontal electric heating production wells assist SAGD to improve oil production rate and oil-gas ratio, effectively reducing the use of steam, increasing the use of green and environmentally friendly energy, and reducing the production cost of the entire production process, and the final recovery rate reaches more than 65%.

[0087] In order to make a clearer description of the SAGD mid- and late-stage enhanced oil recovery method for heterogeneous super-heavy oil reservoirs provided by the embodiment of the present invention and verify the effectiveness of the method, the following is a detailed description of the embodiment of the present invention by taking the implementation plan of a certain oil field and the process of predicting and comparing the production effect of the present invention patent with that of the full-stage SAGD as an example:

[0088] This example discloses an on-site implementation plan for a certain oil field, and predicts and compares the production effects of the patent of the present invention with those of the full-stage SAGD.

[0089] Basic reservoir parameters: reservoir burial depth 200m, porosity 32%, oil saturation 75%, horizontal permeability 1500mD, vertical permeability 1200mD, oil layer thickness 20m, temperature 20℃, viscosity 2334000mPa·s under reservoir temperature conditions.

[0090] First, deploy SAGD enhanced oil production well network:

[0091] Design and deploy SAGD enhanced oil production well patterns in the production area of ​​super heavy oil reservoirs, such as Figure 2 As shown, the well network has at least one pair of SAGD wells (i.e., injection horizontal well 1 and production horizontal well 2), two electrically heated horizontal wells 3 and one electrically heated catalytic reformed multi-branch well 4. The injection horizontal well 1 is deployed at the bottom of the oil layer, the production horizontal well 2 and the injection horizontal well 1 are located on the same vertical plane, 4 to 6 meters apart vertically, the horizontal distance between the production horizontal well 2 and the two electrically heated horizontal wells 3 is 45 meters, and the electrically heated catalytic reformed multi-branch well 4 is deployed 2 meters away from the top of the oil layer.

[0092] Next, the SAGD cavity expansion production phase is carried out in the early stages of development:

[0093] After the SAGD wells are connected for circulation preheating, the injection horizontal well 1 continuously injects steam, the wellhead dryness is 85%, the steam injection rate is more than 100t / d, the bottom hole pressure is 3MPa, the production horizontal well 2 is continuously drained, and the inter-well pressure difference between the injection horizontal well 1 and the production horizontal well 2 is controlled at 0.2-0.6MPa. After the electric heating horizontal well 3 is preheated and preheated by electric heating, it switches to circulation production, using long pipe for continuous steam injection and short pipe for continuous drainage and electric heating at the same time. The long pipe steam injection rate is controlled at 20t / d, and the bottom hole pressure is controlled at 2.5MPa.

[0094] The steam chamber entered the horizontal stage, and the average daily oil production entered the peak production stage. After 5.5 years of production, the daily oil production of the SAGD well reached 42t / d, and the daily oil production of the electrically heated horizontal well 3 reached 11t / d. Figure 3 .

[0095] Then, in the late stage of development, we enter the GCEASAGD generation stage:

[0096] After 10 years of production, the steam chamber expanded to the edge of the oil layer top, and the daily oil production began to decline, turning to the GCEASAGD enhanced oil production stage. The daily oil production of SAGD wells reached 50t / d, and the daily oil production of the electrically heated horizontal wells reached 13t / d, increasing the oil production by more than 10%, and stable production for more than 6 years. The schematic diagram of the connection between the steam / gas chamber of the electrically heated horizontal well assisted SAGD is shown in Figure 4 . SAGD mid- and late-stage enhanced oil recovery method gas / catalytic reforming / electric heating assisted SAGD generation stage steam / gas cavity schematic diagram see Figure 5 .

[0097] Finally, the late stage of development enters the gas injection and oil production stage

[0098] In this stage, the steam chamber is expanded to a maximum recovery rate of 65%. A large amount of gas is injected to utilize the residual heat of the steam chamber to supplement the displacement energy, achieving a stable production of about 550 days. After this stage, the final recovery rate reaches 71%. The schematic diagram of the gas chamber in the late stage of the SAGD mid-to-late enhanced oil recovery method is shown in the figure. Figure 6 .

[0099] Table 1 Production forecast of this implementation scheme

[0100] Technology Comparison Time (year) Recovery rate Oil-gas ratio SAGD 13 52.6 0.19 Mining method of the present invention 18 71 0.23

[0101] As shown in Table 1, from the production situation, the effective production time of dual horizontal well SAGD is 13 years, the final recovery rate is 52.6%, and the oil-gas ratio is 0.19. However, the economically effective production time of the mining method provided by the embodiment of the present invention is about 18 years, and the final recovery rate is 71%. Among them, the recovery degree of GCEASAGD generation stage is 30%, and the recovery degree of injection gas production stage is 6%.

[0102] The method for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD provided by the embodiment of the present invention provides an improved SAGD well network. First, the connection between two large and one small steam chambers is accelerated through steam throughput and electric heating assistance. In the middle stage, the super-heavy oil production is accelerated through catalytic modification of branch wells and gas-assisted SAGD; a production operation method under a new SAGD well network is provided, which is divided into three oil production stages: SAGD expansion production, GCEASAGD generation stage, and gas injection enhanced oil production, to improve the production effect of the entire SAGD process. The injection of gas reduces the heat loss in the production process, the catalytic modifier reduces the viscosity of the super-heavy oil, and the heated horizontal well-assisted SAGD production can effectively produce the remaining oil between wells, and the final recovery rate can reach more than 65%.

[0103] Based on the same inventive concept, the embodiment of the present invention also provides an injection-production well pattern for improving the recovery rate of a heterogeneous super-heavy oil reservoir SAGD in the middle and late stages, referring to Figure 2 As shown, including:

[0104] A SAGD well pair, electrically heated horizontal wells located on both sides of the SAGD well pair, and an electrically heated catalytically upgraded multi-branch well located on top of the SAGD well pair;

[0105] In the SAGD production stage, the SAGD well pair is used for circulation preheating, and then steam is injected to switch to the cavity expansion production stage; the electrically heated horizontal well is used for preheating by huff and puff and electric heating, and then switched to long-tube steam injection and short-tube oil production;

[0106] In the GCEASAGD production stage: when the recovery degree is 30-35%, the electrically heated catalytic reforming branch well is used to inject catalytic reforming agent, and the injection well of the SAGD well pair is used to inject non-condensable gas, reducing the steam of a preset mass of water equivalent in a unit cycle time, gradually reducing the steam injection amount according to the set ratio while increasing the injection amount of non-condensable gas, until the surface volume ratio of the steam and non-condensable gas injection amounts reaches the preset ratio;

[0107] When the steam chamber of the SAGD well pair is connected to the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is used to switch to continuous oil production and perform electrically heated assisted production; when the recovery degree is 55-60%, the injection well of the SAGD well pair is used to reduce the steam of a preset mass of water equivalent within a unit cycle time, and increase the injection of non-condensable gas, and control the increase in the amount of injected non-condensable gas to be a preset multiple interval of the reduction in the amount of steam, until switching to gas drive;

[0108] In the gas injection and oil production stage: the injection well of the SAGD well pair is used to continuously inject non-condensable gas to utilize the waste heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to a minimum production threshold, thereby terminating production.

[0109] In a specific embodiment, the electrically heated horizontal wells are respectively located at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the well spacing between the two electrically heated horizontal wells located on the left and right sides of the SAGD well pair is a first distance range;

[0110] The electrically heated catalytically modified multi-branch well is located at the top of the SAGD well pair at a second distance range from the top of the oil layer. The branch length of the electrically heated catalytically modified multi-branch well is within the second length range. The branch direction is the four corners of the oil layer, and it can cover at least one of the SAGD well pairs.

[0111] The specific implementation method of the injection-production well pattern for improving the recovery rate of the heterogeneous super heavy oil reservoir SAGD in the middle and late stages provided by the embodiment of the present invention can refer to the detailed description of the method for improving the recovery rate of the heterogeneous super heavy oil reservoir SAGD in the middle and late stages in the above-mentioned embodiment 1, and will not be repeated here.

[0112] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict. The present invention is not limited to any single aspect, any single embodiment, or any combination and / or permutation of these aspects and / or embodiments. Each aspect and / or embodiment of the present invention can be used alone, or in combination with one or more other aspects and / or other embodiments.

[0113] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for improving oil recovery in the middle and late stages of SAGD in heterogeneous super-heavy oil reservoirs, characterized in that: include: Deploy the injection and production well network: intensify the electrically heated horizontal wells on both sides of the SAGD well pair, and intensify the electrically heated catalytic reformed multi-branch wells on the top of the SAGD well pair; SAGD production stage: After the SAGD well pair is circulated and preheated, steam is injected to switch to the cavity expansion production stage, and the electrically heated horizontal well is preheated by huff and puff and electrically heated to switch to long-tube steam injection and short-tube oil production; GCEASAGD production stage: when the recovery degree is 30-35%, a catalytic modifier is injected through the electrically heated catalytic modification branch well, and non-condensable gas is injected into the injection well of the SAGD well pair, and the steam of a preset mass of water equivalent is reduced within a unit cycle time, and the steam injection amount is gradually reduced according to a set ratio while the injection amount of non-condensable gas is increased, until the surface volume ratio of the steam and non-condensable gas injection amounts reaches a preset ratio; When the steam chamber of the SAGD well pair is connected to the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is switched to continuous oil production, and electrically heated assisted production is performed; when the recovery degree is 55-60%, the steam of a preset mass of water equivalent is reduced within a unit cycle time, and the injection of non-condensable gas is increased, and the increase in the amount of injected non-condensable gas is controlled to be a preset multiple interval of the reduction in the amount of steam, until switching to gas drive; Gas injection and oil production stage: non-condensable gas is continuously injected to utilize the waste heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to the minimum production threshold, and production is terminated.

2. The method according to claim 1, characterized in that The method of adding electrically heated horizontal wells on both sides of the SAGD well pair and adding an electrically heated catalytic reformed multi-branch well on the top of the SAGD well pair comprises: The electrically heated horizontal wells are respectively intensified at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the distance between the two electrically heated horizontal wells is a first distance range; The electrically heated catalytically modified multi-branch wells are densely populated at a second distance range between the top of the SAGD well pair and the top of the oil layer. The branch lengths of the electrically heated catalytically modified multi-branch wells are within the second length range. The branch directions are the four corners of the oil layer and can cover at least one of the SAGD well pairs.

3. The method according to claim 1, characterized in that The injection rate of the catalytic reformer into the electrically heated catalytic reforming branch well is 1% to 5% of the crude oil production rate.

4. The method according to claim 1, characterized in that The catalytic modifier is: Taking the total mass of the catalyst fluid as 100wt%, 10wt% to 50wt% of toluenesulfonyl hydrazide and hydrazine hydrate, 10wt% of at least one of tetralin, tetralone and decalin, 5wt% of coking inhibitor, and the rest being oil phase solvent, the catalyst fluid and water mixed in a mass ratio of 9:

1.

5. The method according to claim 4, characterized in that The coking inhibitor includes at least one of sulfur-containing compounds, phosphorus-containing compounds, organic sulfur-phosphorus compounds, metal organic compounds, metal inorganic salts or oxides, rare earth compounds, boron compounds and organic polysiloxane sulfides.

6. The method according to claim 4, characterized in that The heating temperature of the electrically heated catalytic reforming branch well is 240°C to 260°C.

7. The method according to claim 1, characterized in that The electric heating power for electric heating assisted production of the electric heating horizontal well is 1000-1500 W / m.

8. The method according to claim 1, characterized in that When the recovery rate is 55-60%, the initial injection velocity of non-condensable gas is 4000-8000m 3 / d.

9. The method according to claim 1, characterized in that During the gas injection oil production stage, the continuous non-condensate gas injection rate is 15000~35000m 3 / d.

10. The method according to claim 1, characterized in that The non-condensable gas includes at least one of methane and nitrogen.

11. An injection-production well pattern for improving the recovery rate of heterogeneous super-heavy oil reservoirs in the middle and late stages of SAGD, characterized in that: include: A SAGD well pair, electrically heated horizontal wells located on both sides of the SAGD well pair, and an electrically heated catalytically upgraded multi-branch well located on top of the SAGD well pair; In the SAGD production stage, the SAGD well pair is used for circulation preheating, and then steam is injected to switch to the cavity expansion production stage; the electrically heated horizontal well is used for preheating by huff and puff and electric heating, and then switched to long-tube steam injection and short-tube oil production; In the GCEASAGD production stage: when the recovery degree is 30-35%, the electrically heated catalytic reforming branch well is used to inject catalytic reforming agent, and the injection well of the SAGD well pair is used to inject non-condensable gas, reducing the steam of a preset mass of water equivalent in a unit cycle time, gradually reducing the steam injection amount according to the set ratio while increasing the injection amount of non-condensable gas, until the surface volume ratio of the steam and non-condensable gas injection amounts reaches the preset ratio; When the steam chamber of the SAGD well pair is connected to the steam chamber of the electrically heated horizontal well, the electrically heated horizontal well is used to switch to continuous oil production and perform electrically heated assisted production; when the recovery degree is 55-60%, the injection well of the SAGD well pair is used to reduce the steam of a preset mass of water equivalent within a unit cycle time, and increase the injection of non-condensable gas, and control the increase in the amount of injected non-condensable gas to be a preset multiple interval of the reduction in the amount of steam, until switching to gas drive; In the gas injection and oil production stage: the injection well of the SAGD well pair is used to continuously inject non-condensable gas to utilize the waste heat of the steam chamber to affect the remaining oil in the steam chamber until the production of the SAGD well pair decreases to a minimum production threshold, thereby terminating production.

12. The well pattern according to claim 11, characterized in that: The electrically heated horizontal wells are respectively located at a preset distance range in the horizontal direction on the left and right sides of the SAGD well pair, the length of the electrically heated horizontal well is a first length range, and the well spacing between the two electrically heated horizontal wells located on the left and right sides of the SAGD well pair is a first distance range; The electrically heated catalytically modified multi-branch well is located at the top of the SAGD well pair at a second distance range from the top of the oil layer. The branch length of the electrically heated catalytically modified multi-branch well is within the second length range. The branch direction is the four corners of the oil layer, and it can cover at least one of the SAGD well pairs.

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