Horizontal well flooding and drainage combined SAGD oil extraction method

Abstract

The invention relates to a horizontal well driving and discharging combined SAGD oil extraction method. The horizontal well driving and discharging combined SAGD oil extraction method comprises the following steps that a steam injection horizontal well is arranged at a layer to be subjected to oil extraction; production horizontal wells are arranged below the two sides of the steam injection horizontal well respectively; performing steam huff and puff on the to-be-exploited oil layer 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; and steam displacement and gravity oil drainage are carried out on the to-be-exploited oil layer, so that crude oil enters a production horizontal well, and the crude oil is exploited through the production horizontal well. The method has the effects of steam displacement and gravity oil drainage at the same time, so that the recovery capacity of crude oil is enhanced, the recovery efficiency of a thin oil layer is improved, and the SAGD implementation limit of the thin oil layer is widened from 12 m to 8 m.

Description

Technical Field

[0001] The present invention relates to the field of petroleum, and in particular to displacement and oil drainage technology. Background Art

[0002] SAGD (steam-assisted gravity drive) development technology is a cutting-edge technology for developing super-heavy oil. Its production mechanism is to inject high-dryness steam into the steam injection well, and the steam will overlap upward in the formation to form a steam chamber. The steam chamber will expand upward and laterally, and heat will be exchanged with the crude oil in the oil layer. The heated and reduced-viscosity crude oil and steam condensate will be discharged to the horizontal production well below by gravity. The steam chamber will continue to expand and occupy the volume of crude oil. This technology was invented by Dr. Butler in 1978. At present, it has been promoted and applied in some oil fields at home and abroad. Xinjiang Oilfield and Liaohe Oilfield in China have successfully introduced SAGD technology and successfully implemented it in super-heavy oil reservoirs, achieving good development results, greatly reversing the situation of continuous decline in annual oil production due to steam throughput. It has high oil production rate and low production cost. Its technical advantages have been recognized by people in the oil industry and is considered to be one of the thermal recovery technologies with the highest recovery rate. SAGD development technology uses the continuous expansion of the steam chamber to bring heat. After the crude oil is heated, it will be discharged downward by gravity to the horizontal well at the bottom of the reservoir for production. The effective expansion of the steam chamber, i.e. the size of the drainage space, directly determines the SAGD oil production. Therefore, the thickness of the continuous oil layer is the decisive factor in the SAGD effect. Therefore, for thin oil layers, the limitation of the drainage space affects the final SAGD recovery factor. Summary of the invention

[0003] The embodiment of the present application provides a horizontal well flooding composite SAGD oil production method to solve the technical problem of low SAGD recovery rate in thin oil layers.

[0004] The present application provides a horizontal well flooding composite SAGD oil production method, the horizontal well flooding composite SAGD oil production method comprising 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] Performing steam stimulation on the oil-producing 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;

[0008] The oil layer to be produced is subjected to steam displacement and gravity drainage to allow crude oil to enter a production horizontal well, and crude oil is produced through the production horizontal well.

[0009] In some embodiments of the present application, the total thickness of the oil-producing layer is more than 8 m.

[0010] In some embodiments of the present application, the total thickness of the oil-producing layer is 8-12 m.

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

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

[0013] In some embodiments of the present application, the steam throughput is performed for 8-12 cycles.

[0014] In some embodiments of the present application, the bottom hole steam quality of the steam injection horizontal well is above 60%.

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

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

[0017] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0018] The horizontal well flooding and drainage composite SAGD oil production method provided in the embodiment of the present application arranges production horizontal wells below both sides of the steam injection horizontal well, and innovates 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 to preheat, but also to continue to inject steam for displacement after establishing thermal connection, and accordingly, the production horizontal well originally located directly below the steam injection horizontal well is set into two, and arranged below both sides of the steam injection horizontal well to receive the displaced crude oil. Due to the simultaneous existence 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0021] Figure 1It is the oil saturation field map of the oil-producing layer at different stages;

[0022] Figure 2 It is the daily oil production prediction curve diagram in the flooding and drainage composite stage under different oil layer thickness;

[0023] Figure 3 It is the prediction curve of cumulative oil production in the flooding and drainage composite stage under different oil layer thicknesses;

[0024] Figure 4 It is a statistical diagram of the recovery degree in the flooding and drainage composite stage under different oil layer thicknesses;

[0025] Figure 5 It is a statistical diagram of the oil-gas ratio in the flooding composite stage under different oil layer thicknesses;

[0026] Figure 6 It is a statistical chart of recovery factor of injection and production wells at different vertical distances;

[0027] Figure 7 It is the daily oil production prediction curve of injection and production wells at different vertical distances;

[0028] Figure 8 The temperature field diagram of the oil-producing layer after 10 cycles of steam stimulation;

[0029] Fig. 9 The statistical diagram of the recovery degree and oil-gas ratio in the flooding composite stage under different bottom-hole steam quality;

[0030] Fig.10 The statistical diagram of the recovery degree and oil-gas ratio in the flooding and drainage composite stage at different steam injection rates;

[0031] Fig.11 Statistical diagram of the recovery degree and oil-gas ratio in the flooding and drainage composite stage under different production-injection ratios. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] Unless otherwise specified, the terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. In the event of a conflict, this specification takes precedence.

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

[0035] The existing thin oil layer oil production has the technical problem that the SAGD recovery rate is not high.

[0036] The technical solution provided by the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0037] The present application provides a horizontal well flooding composite SAGD oil production method, the horizontal well flooding composite SAGD oil production method comprising the following steps:

[0038] S1: Arrange steam injection horizontal wells at the oil layer to be produced;

[0039] S2: arranging production horizontal wells below both sides of the steam injection horizontal well;

[0040] S3: performing steam stimulation on the oil-producing layer 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-producing layer to allow crude oil to enter the production horizontal well, and crude oil is produced through the production horizontal well.

[0042] In step S3, steam huff and puff is a conventional technical means in the art. The working process of steam huff and puff is to first inject a certain amount of steam into the oil well, shut down the well for a period of time, and wait for the heat energy of the steam to diffuse into the oil layer. The purpose of steam huff and puff is to establish the thermal connection.

[0043] In step S4, during the steam displacement process, as the steam is injected, the steam cavity is gradually formed, and under the influence of steam overburden, a connection is formed at the top of the oil layer. The 6-10 meter range of the steam injection horizontal well is mainly displacement, and the crude oil approaches the production horizontal well and vertically pulls the steam cavity to form gravity oil drainage. The above working process is a composite stage of displacement and drainage, which is the main oil production period, and the stage recovery degree can reach 35%.

[0044] Figure 1 The oil saturation field diagram of the oil-producing layer at different stages during the implementation of the present application is shown. Figure 1 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Figure 1 It can be seen that after the thermal connection is established, due to the steam pressure, a small amount of crude oil in the oil-producing layer enters the production horizontal well; in the composite stage of flooding and drainage, from the early stage of flooding to the late stage of flooding, the crude oil in the oil layer is significantly transferred to the production horizontal well, and after continuous production, the amount of crude oil in the oil layer is significantly reduced.

[0045] The existing SAGD implementation limit is 12m. Figure 2 The predicted curves of composite daily oil production in the flooding composite stage are shown when the oil layer thickness is 5m, 6m, 8m and 10m respectively. Figure 3 The cumulative oil production prediction curve in the flooding and drainage composite stage is shown when the oil layer thickness is 5m, 6m, 8m and 10m respectively. Figure 4 It shows the recovery degree of the flooding and drainage composite stage when the oil layer thickness is 5m, 6m, 8m and 10m respectively. Figure 2 , Figure 3 and Figure 4 It is obtained through numerical simulation calculation based on simulated oil layer information and existing SAGD related empirical data. The results show that daily oil production, cumulative oil production and recovery degree are positively correlated with thickness. When the continuous thickness is above 8m, the peak daily oil production exceeds 40t / d, and the stage recovery degree reaches more than 30%. Therefore, this application can expand the implementation limit of thin oil layer SAGD from 12m to 8m.

[0046] in addition, Figure 5 It also shows the oil-gas ratio of the flooding composite stage when the oil layer thickness is 5m, 6m, 8m, and 10m respectively. The cost of high-pressure steam is higher, and the higher the oil-gas ratio means the lower the cost. Figure 5 It can be seen that when the oil layer thickness is 6m and 8m, the oil-gas ratio is the same, which means that the steam cost per unit oil production is the same, but when the oil layer thickness is 6m, its total oil production must be lower than that of the oil layer with a thickness of 8m. Taking other costs into consideration, since these costs include one-time costs such as equipment and well layout, the unit oil production cost of the oil layer with a thickness of 8m is lower than that of the oil layer with a thickness of 6m.

[0047] Further considering the oil layer thickness of 5m and 10m, compared with the thickness of 6m, it can be found that at the thickness of 5m, the unit oil production cost increases with the decrease of the total oil production, and the unit oil production cost will also increase with the decrease of the oil-gas ratio. Compared with the thickness of 8m, at the thickness of 10m, the unit oil production cost decreases with the increase of the total oil production, and the unit oil production cost will also decrease with the increase of the oil-gas ratio. Therefore, it can be basically considered that as the thickness of the oil layer increases, the unit oil production cost decreases accordingly.

[0048] Therefore, when the oil layer with a thickness of 8m has reached a peak daily oil production of more than 40t / d and the stage recovery rate has reached more than 30%, as the thickness continues to increase, the daily oil production, cumulative oil production and recovery rate will all increase accordingly, and the unit oil production cost will decrease accordingly. This shows that the thickness range of 8-12m is a suitable thickness range for oil production. This application is a more scientific conclusion to widen the implementation limit of thin oil layer SAGD from 12m to 8m.

[0049] The traditional SAGD operation mode is one injection and one production, that is, one steam injection horizontal well and one production horizontal well are arranged. Usually the production horizontal well is arranged directly below the steam injection horizontal well. The main purpose of steam injection is to heat the oil layer, and the displacement effect is very small. It mainly relies on gravity drainage to make the crude oil in the oil layer enter the production horizontal well. Usually, the SAGD screening standard abroad is 15m. The domestic Liaohe Oilfield Du 84 Block Xing VI Group has widened the SAGD screening standard to 12m, but it is still far from the 8m in this case.

[0050] The present application arranges production horizontal wells below both sides of the steam injection horizontal well, and innovates the original dual horizontal well SAGD of one injection and one production into one injection and two production mode. The purpose of introducing steam is not only to preheat, but also to continue to inject steam for displacement after establishing thermal connection, and accordingly, the production horizontal well originally located directly below the steam injection horizontal well is set into two, and arranged below both sides of the steam injection horizontal well to receive the displaced crude oil. Due to the simultaneous existence 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 SAGD for thin oil layers is widened from 12m to 8m.

[0051] In some embodiments of the present application, the total thickness of the oil-producing layer is more than 8 m.

[0052] As mentioned above, the present application is applicable to oil-producing layers with a total thickness of more than 8 m. The prediction results show that the daily oil production during the peak period exceeds 40 t / d, and the stage recovery degree reaches more than 30%.

[0053] In some embodiments of the present application, the total thickness of the oil-producing layer is 8-12 m.

[0054] The existing SAGD implementation limit is 12m. The oil-producing layer with a thickness of 8-12m is the newly expanded implementation range of this application.

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

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

[0057] Figure 6 The figure shows the final recovery rate of injection and production wells (horizontal steam injection wells and horizontal production wells) at different vertical distances. Figure 6 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Figure 6 It can be seen that a vertical distance of 0-9m can achieve a higher recovery rate, while a vertical distance of 3-5m can achieve the highest recovery rate.

[0058] Figure 7 The daily oil production prediction curve of the injection and production wells at different vertical distances is shown. Figure 7 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Figure 7 It can be seen that the vertical distance of 0-7m can achieve higher daily oil production, and the vertical distance of 9m is slightly lower.

[0059] Therefore, generally speaking, a vertical distance of 0-9 m is a feasible range, and a vertical distance of 3-5 m is a preferred implementation range.

[0060] In some embodiments of the present application, the steam throughput is performed for 8-12 cycles.

[0061] Figure 8 The temperature field diagram of the oil-producing layer after 10 cycles of steam stimulation is shown. Figure 8 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Figure 8 It can be observed that the steam injection horizontal well and the two production horizontal wells have initially established thermal connectivity, with the temperature at the connectivity reaching about 80°C. The simulation results show that the reservoir pressure drops to 3-3.5 MPa, and the temperature and pressure meet the conditions for the flooding and drainage composite stage.

[0062] In some embodiments of the present application, the bottom hole steam quality of the steam injection horizontal well is above 60%.

[0063] Fig. 9 The recovery degree and oil-gas ratio of the flooding composite stage under different bottom hole steam qualities are shown. Fig. 9 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Fig. 9 It can be observed that when the bottom hole steam dryness is below 60%, as the bottom hole steam dryness continues to increase, the recovery rate increases rapidly; when the bottom hole steam dryness is above 60%, as the bottom hole steam dryness continues to increase, the recovery rate remains basically stable, and the oil-gas ratio shows a significant upward drive. This shows that it is more appropriate to control the bottom hole steam dryness above 60%.

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

[0065] Fig.10 The recovery degree and oil-gas ratio of the flooding and drainage composite stage at different steam injection rates are shown. Fig.10 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Fig.10It can be observed that when the steam injection rate increases from 100t / d to 150t / d, the recovery rate increases rapidly; when the steam injection rate is above 150t / d, the recovery rate tends to be stable. Therefore, the steam injection rate should be maintained above 150t / d to maximize the recovery rate.

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

[0067] Fig.11 The recovery degree and oil-gas ratio of the flooding and drainage composite stage under different production-injection ratios are shown. Fig.11 It is obtained through numerical simulation calculation based on simulated reservoir information and existing SAGD related empirical data. Fig.11 It can be observed that when the production-injection ratio is 1.2, the stage recovery degree and the oil-gas ratio are relatively ideal; as a preferred solution, when the production-injection ratio is 1.2, the stage recovery degree and the oil-gas ratio reach their peak values.

[0068] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0069] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. refer to "including but not limited to". Moreover, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single (individual) or plural (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b, and c can be single or multiple, respectively.

[0070] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A horizontal well flooding composite SAGD oil production method, characterized in that: The horizontal well flooding composite SAGD oil production method comprises the following steps: Arrange steam injection horizontal wells at the oil-producing layer; Production horizontal wells are arranged below both sides of the steam injection horizontal well; Performing steam stimulation on the oil-producing layer 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; The oil layer to be produced is subjected to steam displacement and gravity drainage to allow crude oil to enter a production horizontal well, and crude oil is produced through the production horizontal well.

2. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: The total thickness of the oil-producing layer is more than 8 m.

3. The horizontal well flooding composite SAGD oil production method according to claim 2, characterized in that: The overall thickness of the oil-producing layer is 8-12 m.

4. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: The vertical distance between the steam injection horizontal well and the production horizontal well is 0-9m.

5. The horizontal well flooding composite SAGD oil production method according to claim 4, characterized in that: The vertical distance between the steam injection horizontal well and the production horizontal well is 3-5m.

6. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: The steam throughput is performed for 8 to 12 cycles.

7. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: The bottom hole steam quality of the steam injection horizontal well is above 60%.

8. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: During the steam displacement process, the steam injection rate is not less than 150t / d.

9. The horizontal well flooding composite SAGD oil production method according to claim 1, characterized in that: During the steam displacement and crude oil production process, the production-injection ratio is 1.2-1.4.

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