Adjustment method of reservoir development layer series and well pattern and carbonate reservoir development method

Abstract

This invention discloses a method for adjusting reservoir development layers and well patterns, as well as a method for developing carbonate reservoirs. The method for adjusting reservoir development layers and well patterns includes: dividing the reservoir into Class I and Class II reservoirs according to a set classification standard, with Class I reservoirs exhibiting better permeability and homogeneity than Class II reservoirs; splitting the vertical well reverse nine-spot well pattern used for reservoir development into two sets of five-spot well patterns, and separately performing stratified water injection development on Class I and Class II reservoirs until the first predetermined stage; combining the two sets of five-spot well patterns into a new reverse nine-spot well pattern, and using the new reverse nine-spot well pattern for water injection development on Class I reservoirs. This method differentiates the well pattern configuration based on the different physical properties and reserve utilization difficulties of different types of reservoirs, achieving stratified water injection for oil production and solving problems such as single-layer breakthrough, large differences in vertical water drive effects, low reserve utilization, and severe ineffective water circulation. It maximizes the adjustment and rational utilization of old well patterns, reduces drilling and completion investment, and is highly operable.

Description

Technical Field

[0001] This invention relates to the field of reservoir exploration and development technology, and in particular to methods for adjusting reservoir development strata and well patterns, as well as methods for developing carbonate reservoirs. Background Technology

[0002] The Middle East's thick and complex carbonate reservoirs account for 65% of the total remaining recoverable reserves. Their complex characteristics present numerous challenges during development, primarily manifested in hidden interlayers, complex pore-throat structures, unclear internal reservoir structure, difficulty in effectively utilizing large-scale reserves, and a lack of targeted engineering and supporting technologies. These Middle Eastern carbonate reservoirs are extremely thick, with oil layers reaching 400-500 meters in thickness and burial depths of approximately 2000-3000 meters. Water injection is necessary to replenish energy during extraction. In the early stages of development, a flexible reverse nine-point well pattern was typically used for combined vertical well production. However, after long-term water injection, the overall water cut of the reservoir increases. Due to the high permeability of porous carbonate reservoirs, significant differences in interlayer permeability lead to single-layer surges, large variations in vertical water drive effectiveness, low reserve utilization, and severe ineffective water circulation. To address these technical challenges, it is necessary to research a method for adjusting the development strata and well pattern of a super-thick carbonate reservoir, thereby improving overall reserve utilization and water drive efficiency.

[0003] Existing adjustment methods generally involve gradually densifying the well network from the 900m reverse nine-point method to the 630m five-point method and then to the 450m densified five-point method, or directly using stratified oil production and stratified water injection. Summary of the Invention

[0004] The inventors discovered that existing methods for adjusting well networks in the development of thick carbonate reservoirs, such as the incremental densification method, fail to consider the differentiated characteristics of each layer, rely on early activation of high-yield layers for rapid production, and cannot avoid the impact of injected water rushing along high-permeability layers. Direct stratified oil production and water injection, on the other hand, involves numerous wells and significant investment, making adjustments difficult for oilfields with already well-established well networks. To at least partially address these technical problems, the inventors developed this invention, providing, through specific implementation methods, a method for adjusting reservoir development layers and well networks, as well as a method for developing carbonate reservoirs, thereby improving overall reserve utilization and water drive efficiency.

[0005] In a first aspect, embodiments of the present invention provide a method for adjusting reservoir development layers and well patterns, comprising:

[0006] According to the established classification criteria, the reservoir is divided into Class I and Class II reservoirs. The permeability and homogeneity of Class I reservoirs are better than those of Class II reservoirs.

[0007] The vertical well reverse nine-point well network used for reservoir development is divided into two sets of five-point well networks. The two sets of five-point well networks are used to carry out stratified water injection development of the Class I and Class II reservoirs respectively, until the first set stage.

[0008] The two sets of five-point well patterns are combined into a new reverse nine-point well pattern, and the new reverse nine-point well pattern is used to carry out water injection development of the type I reservoir.

[0009] Secondly, embodiments of the present invention provide a method for developing carbonate reservoirs, comprising:

[0010] Water injection development was carried out on carbonate reservoirs using the methods described above.

[0011] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0012] (1) The method for adjusting the reservoir development layer system and well network provided in the embodiments of the present invention takes into account the differentiated characteristics of each layer, and configures the well network differently according to the different physical properties of different types of reservoirs and the different difficulties in mobilizing reserves. Water injection wells are injected in layers to achieve layered water injection for oil production, which solves problems such as single-layer breakthrough phenomenon, large differences in vertical water drive effect, low reserve mobilization degree and serious ineffective water circulation.

[0013] (2) The method for adjusting reservoir development layers and well networks provided in this embodiment of the invention takes into account the problems of numerous wells and large investments in stratified oil production and stratified water injection. For oilfields with already well-developed well networks, the adjustment is even more difficult. The invention innovatively proposes the ideas of well network splitting, well network merging, and well network conversion. The original inverted nine-point well network is split into two sets of five-point well networks, which are used to carry out stratified water injection development of Class I and Class II reservoirs respectively. After the first setting stage, the two sets of five-point well networks are combined into a new inverted nine-point well network, which is used to continue water injection development of Class I reservoirs. After the second setting stage, some development wells in the new inverted nine-point well network are converted into water injection wells, resulting in a converted well network, which is then used to continue water injection development of Class I reservoirs. This maximizes the adjustment and rational utilization of old well networks, unlike existing stratified oil production and stratified water injection methods that involve numerous wells and large investments. Furthermore, it reduces drilling and completion investment and is highly operable.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0016] Figure 1This is a flowchart of the method for adjusting the reservoir development system and well pattern in Embodiment 1 of the present invention;

[0017] Figure 2A This is a diagram showing the change in the planar position of the injection and production wells in the first five-point well network of the reservoir in Embodiment 2 of the present invention;

[0018] Figure 2B This is a diagram showing the vertical stratigraphic variation of the injection and production wells in the first five-point well network of the reservoir in Embodiment 2 of the present invention.

[0019] Figure 3A This is a diagram showing the change in the planar position of the injection and production wells in the second and fifth point well network of the reservoir in Embodiment 2 of the present invention;

[0020] Figure 3B This is a diagram showing the vertical stratigraphic variation of the injection and production wells in the first five-point well network of the reservoir in Embodiment 2 of the present invention.

[0021] Figure 4A This is a diagram showing the change in the planar position of injection and production wells in the new reverse nine-point well pattern of the reservoir in Embodiment 2 of the present invention;

[0022] Figure 4B This is a diagram showing the vertical stratigraphic variation of injection and production wells in the new reverse nine-point well network in the reservoir according to Embodiment 2 of the present invention.

[0023] Figure 5A This is a diagram showing the change in the planar position of injection and production wells in the well network after reservoir conversion in Embodiment 2 of the present invention;

[0024] Figure 5B This is a diagram showing the vertical stratigraphic changes of injection and production wells in the well network after reservoir conversion in Embodiment 2 of the present invention.

[0025] Figure 6 This is a flowchart illustrating the specific implementation of the method for adjusting the reservoir development strata and well pattern in Embodiment 2 of the present invention.

[0026] Figure 7A This is a schematic diagram of the planar position adjustment of the oil reservoir injection and production wells in Embodiment 2 of the present invention;

[0027] Figure 7B This is a schematic diagram of the vertical stratigraphic adjustment of the reservoir injection and production wells in Embodiment 2 of the present invention;

[0028] Figure 8A This is a schematic diagram of the planar position adjustment of the injection and production wells in the carbonate oil reservoir in Embodiment 2 of the present invention;

[0029] Figure 8B This is a schematic diagram of the vertical stratigraphic adjustment of the carbonate oil reservoir injection and production well in Embodiment 2 of the present invention;

[0030] Figure 9 This is a diagram illustrating the implementation effect of a carbonate reservoir in Embodiment 1 of the present invention. Detailed Implementation

[0031] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0032] Existing technologies have several problems. In existing methods for adjusting well networks in the development of thick carbonate reservoirs, the incremental densification method does not consider the differentiated characteristics of each layer, relies on high-yield layers for rapid production in the early stages, and cannot avoid the impact of injected water rushing along high-permeability layers. Direct layered oil production and water injection require numerous wells and significant investment, making adjustments difficult for oilfields with already well-established well networks. To address these issues, this invention provides a method for adjusting reservoir development layers and well networks, as well as a method for developing carbonate reservoirs.

[0033] Example 1

[0034] Embodiment 1 of the present invention provides a method for adjusting the reservoir development system and well pattern, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0035] Step S11: According to the set classification criteria, classify the reservoir into Class I and Class II reservoirs.

[0036] The permeability and homogeneity of Class I reservoirs are better than those of Class II reservoirs.

[0037] When dividing development layers, i.e., dividing reservoir types (each type of reservoir is a development layer), the following principles should be followed: the number of development layers should not be too large, 2-3 development layers are appropriate; different development layers have different lithofacies types; different development layers have different development dynamic characteristics; the layers should be separated by interlayers to facilitate well pattern adjustment in the later stages of development.

[0038] Based on the results of comprehensive geological research, different lithofacies types and their distribution can be identified, and different development strata can be divided by combining the results of fluid production profile testing and MDT testing.

[0039] Based on the basic reservoir physical properties, heterogeneity parameters, fluid properties, and production dynamics of different reservoir systems, the development difficulty of different systems is determined, and they are classified into Class I and Class II reservoirs. Class I reservoirs are relatively homogeneous and relatively easy to develop, and can be developed using well patterns with larger well spacing. Class II reservoirs are highly heterogeneous and difficult to develop, requiring well patterns with smaller well spacing to effectively control reserves.

[0040] The presence of interlayers separating Class I and Class II reservoirs provides a geological basis for stratified water injection development and facilitates the splitting, merging, and adjustment of well networks in the later stages of development.

[0041] Optionally, if there are reservoirs with even worse physical properties and heterogeneity, they can be further classified into three categories. Category III reservoirs have lower permeability and homogeneity than Category II reservoirs; they carry the highest development risk and are typically developed using a separate well network.

[0042] Step S12: The vertical well reverse nine-point well network used for reservoir development is split into two sets of five-point well networks. The two sets of five-point well networks are used to carry out stratified water injection development of Class I and Class II reservoirs respectively, until the first set stage.

[0043] Figure 2A and Figure 3A The well network on the left is a set of vertical well reverse nine-point well networks for reservoir development, which includes multiple well groups. Each well group contains one central water injection well and eight production wells. Furthermore, among the eight production wells, four are side production wells and four are corner production wells. The minimum injection-production well spacing is d.

[0044] The vertical well reverse nine-point well network used for reservoir development can be divided into two sets of five-point well networks. This could include forming the first five-point well network by combining the water injection wells and corner production wells from the vertical well reverse nine-point well network. (See [link to relevant documentation]). Figure 2A As shown on the right; the central injection well and the side production wells in the vertical well reverse nine-point well network are combined to form the second five-point well network, see [link / reference]. Figure 3A As shown on the right.

[0045] For the first five-point well network for developing Class I reservoirs, all perforated sections of production wells in the network that are not located in Class I reservoirs will be sealed. For the second five-point well network for developing Class II reservoirs, all perforated sections of production wells in the network that are not located in Class II reservoirs will be sealed. Since the first and second five-point well networks share injection wells, all perforated sections of injection wells shared by the two five-point well networks in reservoirs other than Class I and Class II reservoirs will be sealed.

[0046] Before using two sets of five-point well networks to carry out stratified water injection development of Class I and Class II reservoirs respectively, it may also include installing packers between the perforated sections of Class I and Class II reservoirs in the central water injection wells of the first and second five-point well networks. The packers are located within a set range around the wellbore of the central water injection well to facilitate stratified water injection control.

[0047] The minimum injection-production well spacing of the first five-point well pattern becomes The minimum injection-production well spacing of the second five-point well network remains d. Therefore, the first five-point well network with a relatively large injection-production well spacing can be used for stratified water injection development of Class I reservoirs, while the second five-point well network with a relatively small injection-production well spacing can be used for stratified water injection development of Class II reservoirs.

[0048] Step S13: Combine the two sets of five-point well patterns into a new reverse nine-point well pattern, and use the new reverse nine-point well pattern to carry out water injection development of a type of reservoir.

[0049] If the water drive sweep volume of the central injection well in one of the two five-point well networks used for stratified water injection development of Class II reservoirs reaches a set condition, and / or the water flooding degree of the corresponding production well reaches a set condition, the perforation of the central injection well in the Class II reservoir is sealed, and a perforation is added in the Class I reservoir of the corresponding production well to enhance production in the Class I reservoir. This process continues until all perforations of the central injection wells in the Class II reservoirs are sealed, resulting in a new reverse nine-point well network, which is used only for developing Class I reservoirs. See [link to relevant documentation]. Figure 4A As shown.

[0050] Based on the water drive sweep volume of the Class II reservoir well network and the order of water flooding of oil wells from high to low, the original well spacing five-point method for exploiting Class II reserves is used to adjust the exploitation layers in batches, either upward or downward. The corresponding water injection wells are used to seal the perforated sections of the Class II reservoir, so that it is merged with the Class I reservoir well network into a set of reverse nine-point injection-production well network with an injection-production well spacing d. Only Class I reservoirs are exploited. This process is equivalent to densifying the Class I reservoir well network.

[0051] In some embodiments, the method may further include: after water injection development of a type of reservoir using a new inverted nine-point well pattern up to a second predetermined stage, converting some development wells in the new inverted nine-point well pattern into water injection wells according to predetermined conversion rules to obtain a converted well pattern; and using the converted well pattern to water injection development of a type of reservoir to further tap the remaining oil potential of the type of reservoir.

[0052] Furthermore, this could include converting corner wells in the new reverse nine-point well network into water injection wells, i.e., densifying the injection wells in the reverse nine-point well network to achieve adjustment of the reverse nine-point well network. See [link to relevant documentation]. Figure 5A As shown.

[0053] The method for adjusting the reservoir development layer system and well network provided in Embodiment 1 of the present invention considers the differentiated characteristics of each layer and configures the well network differently according to the different physical properties of different types of reservoirs and the different difficulties in reservoir utilization. Water injection wells are used for layered water injection to achieve layered water injection oil production, which solves problems such as single-layer breakthrough phenomenon, large differences in vertical water drive effect, low degree of reserve utilization, and serious ineffective water circulation.

[0054] Considering the issues of numerous wells and high investment associated with stratified oil production and water injection, adjustments are even more challenging for oilfields with already well-developed well networks. This paper innovatively proposes a method of well network splitting, merging, and conversion. The original inverted nine-point well network is split into two sets of five-point well networks, which are used to conduct stratified water injection development of Class I and Class II reservoirs, respectively. After the first setting stage, the two sets of five-point well networks are combined into a new inverted nine-point well network, which is then used to continue water injection development of Class I reservoirs. After the second setting stage, some development wells in the new inverted nine-point well network are converted into water injection wells, resulting in a converted well network, which is then used to continue water injection development of Class I reservoirs. This method maximizes the adjustment and rational utilization of existing well networks, differing from existing stratified oil production and water injection methods that involve numerous wells and high investment. It also reduces drilling and completion costs and is highly feasible.

[0055] In some embodiments, the thickness of the oil layer in the reservoir is greater than a set thickness threshold.

[0056] The extraction method described in this invention is only economically viable when the oil layer thickness in the reservoir exceeds a set thickness threshold.

[0057] Example 2

[0058] Embodiment 2 of the present invention provides a specific implementation process for a method of adjusting the reservoir development strata and well pattern, taking the M major W giant porous carbonate reservoir in the Middle East as an example.

[0059] The M reservoir, the subject of this study, is a typical bioclastic limestone reservoir with a very thick reservoir, averaging 200-300m. It has medium porosity and low permeability and was officially put into production in the 1990s. It has been in production for more than 20 years and has been injecting water on a large scale for more than 6 years. Currently, it uses a reverse nine-point vertical well with a well spacing of 900m to inject and produce oil in the three layers of K1, K2 and K3. The overall oil production rate and recovery rate are low.

[0060] Current development status and major development challenges:

[0061] The K1, K2, and K3 strata exhibit significant differences in sedimentary characteristics and reservoir properties. K1 represents a subtidal and open platform facies environment, with shoal bodies as the main sedimentary bodies. K2 is dominated by an intertidal and restricted lagoon environment, accompanied by tidal channel dissection, and consists primarily of tidal channels and intertidal sedimentary bodies. K3 represents a subtidal, platform-margin shoal, and slope facies environment, primarily characterized by grain shoals. These significant differences in sedimentary characteristics lead to substantial differences in their physical properties. A stable interlayer, C2, is distributed throughout the entire oilfield between K1 and K2. Vug pores are developed in the K31 burrowing layer and some locally high-permeability layers in K2, resulting in severe vertical heterogeneity. The thickness and average permeability of different layers are shown in Table 1.

[0062] Current development status:

[0063] During the extraction process, the injected water surged along the high-permeability layer of K3 dissolution pores and the tidal channel of K2, resulting in poor utilization of other reservoirs. The huge inter-layer contradictions caused the water cut of single wells to rise rapidly and the water drive effect of different layers to vary greatly. K3 is the main water-absorbing layer, while K2 and K3 have high oil production, as shown in Table 2. The fluid production and water absorption profile test of nearly 150 wells shows that the overall reserve utilization rate is low, only 40%, as shown in Table 3.

[0064] Table 1. Vertical stratigraphic parameters of the research target

[0065] Layer sedimentary environment Stratum thickness (m) Permeability (mD) K1 Qiutan body 40 30～50 K2 Tide 50 100 K31 Slope, high-permeability solution pit 12 500～4000 K32 slope, micropore 80 5～15 K4 micropores 60 1～5 total 240 38

[0066] Table 2. Statistical table of fluid production and water absorption profile tests of 150 wells in the past two years.

[0067] Layer Oil production Proportion Water production Proportion Liquid production Proportion Water absorption Proportion K1 95447 27.2 20050 29.2 115497 28 142522 25.8 K2 126115 36.0 15463 22.5 141578 34 150936 27.3 K3 128801 36.8 33098 48.2 161900 39 259179 46.9 total 350363 68611 418975 552637

[0068] Table 3. Statistical table of fluid production and water absorption profile tests of 150 wells in the past two years.

[0069]

[0070] The significant differences between reservoir layers have led to a gradual decline in the overall injection and production effect of vertical wells. Currently, all old wells have reached water, with water cut ranging from 2% to 20%. The increased water production has put enormous pressure on surface wet oil treatment, which cannot be handled and has resulted in well shutdowns. Consequently, the current well operating rate is less than half, which seriously affects the oilfield's production capacity and the achievement of production and operation goals. There is an urgent need to adjust this unsuitable development layer system and development well network to meet the urgent demand for rapid production increase in the oilfield.

[0071] The method for adjusting reservoir development layers and well patterns provided in Embodiment 2 of this invention has the following implementation process: Figure 6 As shown, it includes the following steps:

[0072] Step S61: Divide the M reservoir into three strata: K1, K2 and K3.

[0073] Based on four principles—significant differences in interlayer sedimentary characteristics and reservoir properties; the material basis for stratified development; different development characteristics (e.g., pressure depletion); a combined production span >150m; severe interlayer interference; and poor vertical mobility of water channeling in high-permeability layers—the M reservoir is divided into three strata: K1, K2, and K3. Specific parameters are shown in Table 4.

[0074] Table 4. Stratigraphic Parameters

[0075]

[0076] Based on reservoir development and considering the overlapping characteristics of tidal channels at different stages, K2 layer exhibits strong heterogeneity, with production and water injection mainly concentrated in the tidal channels, while the lagoon portion has relatively low production. This makes well network deployment and activation difficult, thus classifying it as a Class II reservoir. K1, with strong homogeneity, is relatively easier to activate and is therefore classified as a Class I reservoir. K3 is currently the main water-channeling layer, therefore, activation using a separate well network is tentatively considered.

[0077] Based on the above-mentioned development layer division, adjustments will be made to the development well network under the general injection-production well network of vertical wells and reverse nine-point wells to improve the utilization rate of reserves in each layer. This will be implemented in stages:

[0078] Step S62: The 900m vertical well reverse nine-point well network used for reservoir development is divided into a 1250m five-point well network and a 900m five-point well network, which are used to develop Class I reservoir (K1) and Class II reservoir (K2) respectively. The central water injection well adopts layered water injection.

[0079] The 900m vertical well reverse nine-point well network used for reservoir development was split into two sets of five-point well networks. The central water injection well and the corner production well in the original vertical well reverse nine-point well network were combined to form a 1250m five-point well network (see the changes in the plane position of the injection and production wells for details). Figure 2A As shown, the variation of vertical stratigraphic positions in injection and production wells is illustrated in [reference needed]. Figure 2B (As shown); the central injection well and the side production wells in the original nine-point well network of the vertical well form a 900m five-point well network (see the changes in the plane position of the injection and production wells for details). Figure 3A As shown, the variation of vertical stratigraphic positions in injection and production wells is illustrated in [reference needed]. Figure 3B (As shown). A packer is installed between the perforated sections of the Class I and Class II reservoirs in the central injection well to carry out stratified water injection development of the Class I and Class II reservoirs. A 1250m five-point well pattern is used to develop Class I reservoir K1, and a 900m five-point well pattern is used to develop Class II reservoir K2.

[0080] Step S63: Combine the 1250m five-point well network and the 900m five-point well network into a new reverse nine-point well network, and use the new reverse nine-point well network to carry out water injection development of a Class I reservoir.

[0081] If the water drive sweep volume of the central injection well in the 900m five-point well network used for stratified water injection development of Class II reservoirs reaches a certain level, and / or the water flooding degree of the corresponding production well reaches a certain level, then the perforations of the central injection well in the Class II reservoir will be sealed in batches, and perforations will be patched in the Class I reservoir of the corresponding production well to increase production, until all perforations of the central injection wells in the Class II reservoirs are sealed, resulting in a new reverse nine-point well network, which is only used for developing Class I reservoirs. For changes in the planar positions of injection and production wells, see [link to relevant documentation]. Figure 4A As shown, the variation of vertical stratigraphic positions in injection and production wells is illustrated in [reference needed]. Figure 4B As shown.

[0082] Step S64: After the new reverse nine-point well network has been used to develop the reservoir to a certain extent through water injection, the corner wells in the new reverse nine-point well network are converted into water injection wells to obtain the converted well network. The converted well network is then used to continue to develop the reservoir through water injection.

[0083] For changes in the planar position of injection and production wells, see [link to relevant documentation]. Figure 5A As shown, the variation of vertical stratigraphic positions in injection and production wells is illustrated in [reference needed]. Figure 5B As shown.

[0084] The adjustment method proposed in Embodiment 2 of this invention firstly splits the current generalized nine-point injection-production well network into two sets of five-point well networks. Well spacing is configured based on the reservoir properties and reservoir utilization difficulty of different formations, with water injection wells performing stratified water injection for oil recovery. Then, through sealing and perforation, the two sets of five-point well networks are merged into a reverse nine-point well network with the original well spacing to develop single-layer production, effectively densifying the well network. Finally, it is adjusted and converted back to a five-point well network, undergoing further adjustments. The changes in the planar positions of the injection and production wells throughout the entire process are detailed below. Figure 7A and Figure 8A As shown, the variation of vertical stratigraphic positions in injection and production wells is illustrated in [reference needed]. Figure 7B and Figure 8B As shown. This method solves to some extent the problems that traditional methods cannot address, such as water channeling along high-permeability layers, large differences in water drive effects between layers, low reserve utilization, and low water injection efficiency under general injection and production. Moreover, it reduces drilling and completion investment and is highly operable.

[0085] The existing 430 development wells in the main oil reservoir M were adjusted, and the feasibility of the method was verified by comparing it with the original plan. The original plan was to gradually re-complete and exploit the K1 layer of all old wells over 5 years, fracturing and injecting water to increase the water injection volume, and later deploy 98 wells in the K2 layer as an independent well network.

[0086] Using the method proposed in Embodiment 2 of this invention, all old wells are split into 1250m five-point well networks and 900m five-point well networks to develop K1 and K2. It is considered that the K2 layer wells will be re-completed in 2032 to develop the K1 layer. The K3 layer is partially flooded and will not be considered for the time being. In 2035, the corner wells will be converted into water injection wells to develop the K1 layer. The simulation prediction effect is good. Compared with the original plan: (1) The production output at the end of the contract period has been increased. By controlling the water cut, the cumulative oil production at the end of the contract period will increase by 690 million barrels, the stable production period will be extended by 2 years, and the water cut will be basically the same; (2) Good development benefits have been achieved. There is no need to drill new wells in K2, saving drilling and completion costs of US$490 million (US$5 million / well); water injection wells do not need to be fractured, reducing fracture costs by US$38.13 million (US$465,000 / well, 82 wells), saving a total investment of US$520 million. See Figure 9 The diagram shown illustrates the implementation effect of Example 2.

[0087] The method proposed in Embodiment 2 of this invention is simple to operate and technically mature. It can achieve well pattern adjustment and conversion using domestic layered water injection technology, plugging and perforation technology, without the need for fracturing technology. It can realize the overall utilization of the reservoir profile and is expected to be able to effectively adjust the well pattern of old wells in the huge thick oil reservoir in Iraq, which accounts for half of the reserves in the Middle East. It can save investment in new well drilling, completion and fracturing injection, improve water injection efficiency and alleviate the bottleneck of surface treatment capacity that is common in the Middle East.

[0088] Based on the inventive concept of this invention, embodiments of this invention also provide a method for developing carbonate reservoirs, including:

[0089] Water injection development was carried out on carbonate reservoirs using the methods described above.

[0090] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0091] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0092] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term “comprising” as used in the specification or claims is interpreted in a manner similar to the term “including,” as it is understood when used as a conjunction in the claims. Additionally, the use of any term “or” in the specification of the claims is intended to mean “non-exclusive or.” The terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A method for adjusting reservoir development layers and well pattern, characterized in that, include: According to the established classification criteria, the reservoir is divided into Class I and Class II reservoirs. The permeability and homogeneity of Class I reservoirs are better than those of Class II reservoirs. The vertical well reverse nine-point well network used for reservoir development is divided into two sets of five-point well networks. The two sets of five-point well networks are used to carry out stratified water injection development of the Class I and Class II reservoirs respectively, until the first set stage. If the water drive sweep volume of the central injection well and / or the water flooding degree of the corresponding production well in one of the two sets of five-point well networks used for stratified water injection development of Class II reservoirs reach the set conditions, then the perforation of the central injection well in the Class II reservoir is blocked, and a perforation is added in the Class I reservoir of the corresponding production well, until all perforations of the central injection wells in the Class II reservoir are blocked, resulting in a new reverse nine-point well network. The new reverse nine-point well network is used for water injection development of the Class I reservoir until the second set stage. Then, according to the set conversion rules, some development wells in the new reverse nine-point well network are converted into water injection wells, resulting in a converted well network. The converted well network is then used for water injection development of the Class I reservoir. The method of splitting the vertical well reverse nine-point well network used for reservoir development into two sets of five-point well networks specifically includes: forming a first five-point well network by combining the central water injection wells and corner production wells in the vertical well reverse nine-point well network used for reservoir development; and forming a second five-point well network by combining the central water injection wells and side production wells in the vertical well reverse nine-point well network.

2. The method as described in claim 1, characterized in that, The method of using the two sets of five-point well networks to carry out stratified water injection development of the Class I and Class II reservoirs respectively includes: The first five-point well pattern is used to carry out stratified water injection development of the type of reservoir; The second five-point well pattern is used to carry out stratified water injection development of the second type of reservoir.

3. The method as described in claim 1, characterized in that, Before using the two sets of five-point well networks to carry out stratified water injection development of the Class I and Class II reservoirs respectively, the method further includes: A packer is installed between the Class I and Class II reservoir perforated sections of the central injection well in the two sets of five-point well networks. The packer is located within a set range around the wellbore of the central injection well.

4. The method as described in claim 1, characterized in that, The process of converting a portion of the development wells in the new reverse nine-point well network into water injection wells according to the set conversion rules specifically includes: The corner wells in the new reverse nine-point well network will be converted into water injection wells.

5. The method according to any one of claims 1 to 4, characterized in that, There is an interlayer between the Class I reservoir and the Class II reservoir.

6. The method according to any one of claims 1 to 4, characterized in that, Also includes: According to the established classification criteria, the oil reservoir is divided into three types of reservoirs, and the permeability and homogeneity of the three types of reservoirs are inferior to those of the second type of reservoir. The three types of reservoirs are developed using a set well pattern.

7. The method according to any one of claims 1 to 4, characterized in that, The thickness of the oil layer in the reservoir is greater than a set thickness threshold.

8. A method for developing carbonate reservoirs, characterized in that, include: Water injection development of carbonate reservoirs is carried out according to any one of claims 1 to 7.

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