Horizontal well drainage composite sagd oil production method

Abstract

The application relates to a horizontal well drive and discharge composite SAGD oil production method, which comprises the following steps: arranging a steam injection horizontal well at an oil production layer; arranging a production horizontal well below both sides of the steam injection horizontal well respectively; carrying out steam stimulation on the oil production layer through the steam injection horizontal well and the production horizontal well until thermal connection is established between the steam injection horizontal well and the production horizontal well; carrying out steam displacement and gravity discharge on the oil production layer, so that crude oil enters the production horizontal well and the crude oil is produced through the production horizontal well. The steam displacement and the gravity discharge exist simultaneously, the oil production capacity is enhanced, the thin oil layer recovery rate is improved, and the SAGD implementation limit of the thin oil layer is widened from 12m to 8m.

Description

Technical Field

[0001] This application relates to the petroleum industry, and in particular to displacement and draining technologies. Background Technology

[0002] SAGD (Steam-Assisted Gravity Driving) is a cutting-edge technology for developing extra-heavy oil. Its extraction mechanism involves injecting high-dryness steam into a steam injection well. The steam rises and overlaps the formation, forming a steam chamber. This steam chamber expands upwards and laterally, exchanging heat with the crude oil in the reservoir. The heated, viscosity-reduced crude oil and steam condensate drain under gravity into horizontal production wells below. The steam chamber continues to expand, gradually occupying more crude oil volume. Invented by Dr. Butler in 1978, this technology has been widely applied in some oilfields both domestically and internationally. In China, the Xinjiang Oilfield and Liaohe Oilfield have successfully introduced SAGD technology and implemented it in extra-heavy oil reservoirs, achieving good development results. It has significantly reversed the trend of continuously declining annual oil production from steam injection, offering high oil recovery rates and low extraction costs. Its technological advantages have been recognized by the petroleum industry and it is considered one of the most efficient thermal recovery technologies. SAGD utilizes the continuous expansion of the steam chamber to generate heat, and the heated crude oil drains downwards under gravity into horizontal wells at the bottom of the reservoir. The effective expansion of the steam chamber, i.e., the size of the drainage space, directly determines the oil production of SAGD. Therefore, the thickness of the continuous oil layer is a decisive factor in the effectiveness of SAGD. Consequently, for thin oil layers, the limited drainage space affects the final recovery rate of SAGD. Summary of the Invention

[0003] This application provides a horizontal well drainage combined with SAGD oil recovery method to solve the technical problem of low SAGD recovery rate in thin oil layers.

[0004] This application provides a horizontal well drainage combined with SAGD oil recovery method, which includes the following steps:

[0005] Arrange steam injection horizontal wells at the oil-producing layer;

[0006] Production horizontal wells are arranged below both sides of the steam injection horizontal well;

[0007] Steam is injected and pumped into the oil-producing formation through the steam injection horizontal well and the production horizontal well until thermal communication is established between the steam injection horizontal well and the production horizontal well.

[0008] The oil-bearing formation is subjected to steam displacement and gravity drainage to allow crude oil to enter the production horizontal well, and the crude oil is extracted through the production horizontal well.

[0009] In some embodiments of this application, the total thickness of the oil-bearing reservoir is 8m or more.

[0010] In some embodiments of this application, the total thickness of the oil-bearing reservoir is 8-12m.

[0011] In some embodiments of this application, the vertical distance between the steam injection horizontal well and the production horizontal well is 0-9m.

[0012] In some embodiments of this application, the vertical distance between the steam injection horizontal well and the production horizontal well is 3-5m.

[0013] In some embodiments of this application, the steam huff and puff cycle is 8-12 cycles.

[0014] In some embodiments of this application, the bottom steam dryness of the steam injection horizontal well is 60% or more.

[0015] In some embodiments of this application, the steam injection rate during the steam displacement process is not less than 150 t / d.

[0016] In some embodiments of this application, the injection-production ratio is 1.2-1.4 during the steam displacement and crude oil extraction process.

[0017] The technical solutions provided in this application have the following advantages compared with the prior art:

[0018] The horizontal well displacement combined SAGD oil recovery method provided in this application embodiment arranges production horizontal wells below both sides of the steam injection horizontal well, innovating the original one-injection-one-production dual-horizontal-well SAGD into a one-injection-two-production mode. The purpose of steam injection is not only for preheating, but also to continue injecting steam for displacement after establishing thermal connection. Accordingly, the production horizontal wells originally located directly below the steam injection horizontal well are set up as two, arranged below both sides of the steam injection horizontal well, to receive the displaced crude oil. Due to the simultaneous effects of steam displacement and gravity drainage, the crude oil recovery capacity is enhanced, the recovery rate of thin oil layers is improved, and the implementation limit of thin oil layer SAGD is widened from 12m to 8m. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1Oil saturation field diagrams of the oil-bearing reservoirs to be extracted at different stages;

[0022] Figure 2 A graph showing the predicted daily oil production during the combined displacement and drainage stage under different oil layer thicknesses;

[0023] Figure 3 A graph showing the cumulative oil production prediction curves during the combined displacement and drainage stage under different oil layer thicknesses;

[0024] Figure 4 A statistical chart showing the recovery rate during the combined displacement and drainage stage at different reservoir thicknesses;

[0025] Figure 5 A statistical chart of the oil-gas ratio during the combined displacement and drainage stage under different oil layer thicknesses;

[0026] Figure 6 A statistical chart showing the recovery rate of injection wells at different vertical distances;

[0027] Figure 7 A graph showing the predicted daily oil production of injection wells at different vertical distances;

[0028] Figure 8 This is a temperature field diagram of the oil-bearing reservoir after 10 cycles of steam huff and puff.

[0029] Figure 9 Statistical charts showing the recovery rate and oil-steam ratio during the combined displacement and drainage stage under different bottom hole steam dryness;

[0030] Figure 10 Statistical charts showing the recovery rate and oil-steam ratio during the combined displacement and venting stage at different steam injection rates;

[0031] Figure 11 This is a statistical chart showing the recovery rate and oil-gas ratio during the combined displacement and venting stage under different production-injection ratios. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Unless otherwise specified, the terminology used herein should be understood as having the meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any conflict, this specification shall prevail.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] Existing thin-layer oil recovery methods suffer from low SAGD recovery rates.

[0036] The technical solution provided in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0037] This application provides a horizontal well drainage combined with SAGD oil recovery method, which includes the following steps:

[0038] S1: Arrange steam injection horizontal wells at the oil-producing layer;

[0039] S2: Production horizontal wells are arranged below both sides of the steam injection horizontal well;

[0040] S3: Steam is injected into the oil-producing formation through the steam injection horizontal well and the production horizontal well until thermal communication is established between the steam injection horizontal well and the production horizontal well;

[0041] S4: Steam displacement and gravity drainage are performed on the oil-bearing layer to allow crude oil to enter the production horizontal well, and crude oil is extracted through the production horizontal well.

[0042] In step S3, steam injection is a conventional technique in the field. The steam injection process involves injecting a certain amount of steam into the oil well, shutting the well in for a period of time, and allowing the heat energy of the steam to diffuse into the oil layer. The purpose of steam injection is to establish thermal connectivity.

[0043] In step S4, during the steam displacement process, as steam is injected, a steam cavity gradually forms. Due to the steam over-coverage effect, a connection is formed at the top of the oil layer. In the 6-10 meter range of the steam injection horizontal well, displacement is the primary function. After the crude oil approaches the vertically traction steam cavity of the production horizontal well, gravity drainage occurs. The above process constitutes the combined displacement and drainage stage, which is the main oil production period, with a stage recovery rate of up to 35%.

[0044] Figure 1 The diagram shows the oil saturation field of the oil-bearing reservoir at different stages during the implementation of this application. Figure 1 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 1 It is evident that after the thermal connection is established, due to steam pressure, a small amount of crude oil from the reservoir to be produced enters the production horizontal well; during the combined displacement and drainage stage, from the initial stage to the later stage of displacement and drainage, the crude oil in the reservoir is significantly transferred to the production horizontal well, and after continuous production, the amount of crude oil in the reservoir is significantly reduced.

[0045] The existing SAGD implementation limit is 12m. Figure 2 The predicted curves of combined daily oil production during the drainage and dewatering stage are shown when the oil layer thickness is 5m, 6m, 8m, and 10m. Figure 3 The cumulative oil production prediction curves during the combined displacement and drainage stage are shown when the oil layer thickness is 5m, 6m, 8m, and 10m. Figure 4 The results show the recovery rate during the combined dissipation and drainage stage when the oil reservoir thickness is 5m, 6m, 8m, and 10m. Figure 2 , Figure 3 and Figure 4 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. The results show that daily oil production, cumulative oil production, and recovery rate are all positively correlated with reservoir thickness. When the continuous thickness is greater than 8m, peak daily oil production exceeds 40t / d, and the stage recovery rate reaches over 30%. Therefore, this application can broaden the implementation limit of SAGD in thin reservoirs from 12m to 8m.

[0046] in addition, Figure 5 The oil-steam ratio during the combined displacement stage is also shown for oil layer thicknesses of 5m, 6m, 8m, and 10m. High-pressure steam is more expensive; a higher oil-steam ratio means lower costs. Figure 5 It is evident that the oil-gas ratio is the same when the oil layer thickness is 6m and 8m, which means that the steam cost per unit of oil production is the same. However, the total oil production of an oil layer with a thickness of 6m is necessarily lower than that of an oil layer with a thickness of 8m. Taking other costs into account, since these costs include one-time costs such as equipment and well placement, the unit oil production cost of an oil layer with a thickness of 8m is lower than that of an oil layer with a thickness of 6m.

[0047] Further considering oil reservoir thicknesses of 5m and 10m, compared to a 6m thickness, it can be observed that at a 5m thickness, the unit oil production cost increases as the total oil production decreases, and also increases as the oil-steam ratio decreases. Compared to an 8m thickness, at a 10m thickness, the unit oil production cost decreases as the total oil production increases, and also decreases as the oil-steam ratio increases. Therefore, it can be generally concluded that as the oil reservoir thickness increases, the unit oil production cost decreases.

[0048] Therefore, when an oil layer with a thickness of 8m has already reached a peak daily oil production of over 40t / d and a stage recovery rate of over 30%, as the thickness continues to increase, the daily oil production, cumulative oil production, and recovery rate will all increase accordingly, while the unit oil production cost will decrease. This indicates that the thickness range of 8-12m is a suitable thickness range for oil production. The conclusion that this application expands the implementation limit of SAGD for thin oil layers from 12m to 8m is a relatively scientific one.

[0049] Traditional SAGD operations involve a one-injection-one-production configuration, typically employing a steam injection horizontal well and a production horizontal well. The production horizontal well is usually positioned directly below the steam injection horizontal well. The primary purpose of steam injection is to heat the reservoir; displacement is minimal, and crude oil is mainly drained into the production horizontal well by gravity. Internationally, the standard for SAGD selection is typically 15m, while in China, the Xing VI formation of the Du 84 block in the Liaohe Oilfield has broadened this standard to 12m, but this still falls far short of the 8m standard used in this case.

[0050] This application proposes to arrange production horizontal wells below both sides of the steam injection horizontal well, innovating the original dual-horizontal-well SAGD (one injection, one production) mode into a one-injection, two-production mode. The purpose of introducing steam is not only for preheating, but also, after establishing thermal connectivity, to continue injecting steam for displacement. Correspondingly, the production horizontal wells, originally located directly below the steam injection horizontal well, are now two, arranged below both sides of the steam injection horizontal well to receive the displaced crude oil. Due to the simultaneous effects of steam displacement and gravity drainage, the crude oil recovery capacity is enhanced, the recovery rate of thin oil layers is increased, and the implementation limit of thin oil layer SAGD is widened from 12m to 8m.

[0051] In some embodiments of this application, the total thickness of the oil-bearing reservoir is 8m or more.

[0052] As mentioned above, this application is applicable to oil-bearing formations with a total thickness of more than 8m. Prediction results show that the peak daily oil production exceeds 40t / d, and the stage recovery rate reaches more than 30%.

[0053] In some embodiments of this application, the total thickness of the oil-bearing reservoir is 8-12m.

[0054] The existing limit for SAGD implementation is 12m. Oil reservoirs with a thickness of 8-12m are the newly expanded scope of implementation in this application.

[0055] In some embodiments of this application, the vertical distance between the steam injection horizontal well and the production horizontal well is 0-9m.

[0056] In some embodiments of this application, the vertical distance between the steam injection horizontal well and the production horizontal well is 3-5m.

[0057] Figure 6 The final recovery rate of injection wells (steam injection horizontal wells and production horizontal wells) at different vertical distances is shown. Figure 6 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 6 As can be seen, a high recovery rate can be achieved with a vertical distance of 0-9m, while the highest recovery rate can be achieved with a vertical distance of 3-5m.

[0058] Figure 7 The daily oil production prediction curves of injection wells at different vertical distances are shown. Figure 7 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 7 As can be seen, higher daily oil production can be achieved at vertical distances of 0-7m, while it is slightly lower at a vertical distance of 9m.

[0059] Therefore, in general, a vertical distance of 0-9m is feasible, while a vertical distance of 3-5m is the preferred range.

[0060] In some embodiments of this application, the steam huff and puff cycle is 8-12 cycles.

[0061] Figure 8 The temperature field diagram of the oil reservoir to be produced is shown after 10 cycles of steam huff and puff. Figure 8 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 8 It can be observed that a preliminary thermal connection has been established between the steam injection horizontal well and the two production horizontal wells, with the temperature at the connection point reaching approximately 80℃. Simulation results indicate that the reservoir pressure drops to 3–3.5 MPa, and the temperature and pressure meet the conditions for the combined displacement and drainage stage.

[0062] In some embodiments of this application, the bottom steam dryness of the steam injection horizontal well is 60% or more.

[0063] Figure 9 The results show the recovery rate and oil-steam ratio during the combined displacement and drainage stage under different bottom hole steam dryness. Figure 9 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 9 It can be observed that when the bottom-hole steam dryness is below 60%, the recovery rate increases rapidly as the bottom-hole steam dryness continues to increase; when the bottom-hole steam dryness is above 60%, the recovery rate remains relatively stable as the bottom-hole steam dryness continues to increase, while the oil-steam ratio shows a significant upward trend. This indicates that controlling the bottom-hole steam dryness above 60% is more appropriate.

[0064] In some embodiments of this application, the steam injection rate during the steam displacement process is not less than 150 t / d.

[0065] Figure 10 The results show the recovery rate and oil-gas ratio during the combined displacement and venting stage at different steam injection rates. Figure 10 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 10It can be observed that when the steam injection rate increases from 100 t / d to 150 t / d, the recovery rate increases rapidly; when the steam injection rate is above 150 t / d, the recovery rate tends to stabilize. Therefore, the steam injection rate should be maintained above 150 t / d to maximize the recovery rate.

[0066] In some embodiments of this application, the injection-production ratio is 1.2-1.4 during the steam displacement and crude oil extraction process.

[0067] Figure 11 The recovery rate and oil-gas ratio during the combined displacement and venting stage are shown under different production-injection ratios. Figure 11 The results were obtained through numerical simulation calculations based on simulated reservoir information and existing SAGD-related empirical data. Figure 11 It can be observed that when the production-injection ratio is 1.2, the stage recovery rate and oil-gas ratio are both relatively ideal; as the preferred scheme, when the production-injection ratio is 1.2, the stage recovery rate and oil-gas ratio reach their peak values.

[0068] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0069] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. For associations involving three or more related objects described using "and / or", it indicates that any one of the three related objects can exist alone, or at least two of them can exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0070] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A horizontal well drainage combined with SAGD oil recovery method, characterized in that, The horizontal well drainage combined SAGD oil recovery method includes the following steps: A steam injection horizontal well is installed at the oil-producing layer; A production horizontal well is arranged below each of the two sides of the steam injection horizontal well; Steam is injected and pumped into the oil-producing formation through the steam injection horizontal well and the production horizontal well until thermal communication is established between the steam injection horizontal well and the production horizontal well. Steam displacement and gravity drainage are performed on the oil-bearing formation to allow crude oil to enter the production horizontal well, and crude oil is extracted through the production horizontal well. The total thickness of the oil-bearing layer to be extracted is 8-12m; The vertical distance between the steam injection horizontal well and the production horizontal well is 3-5m; The bottom steam dryness of the steam injection horizontal well is above 60%; During the steam displacement and crude oil extraction process, the oil recovery-injection ratio is 1.2-1.4; The steam huff and puff cycle is 8-12 cycles; During the steam displacement process, the steam injection rate shall not be less than 150t / d.

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