Bottom water reservoir pressure cone wheel mining development design method based on double-branch horizontal well

Abstract

The invention discloses a bottom water reservoir pressure cone wheel mining development design method based on a double-branch horizontal well. The method comprises the steps that the well spacing thickness limit and the horizontal well type are determined; determining the well number, the well location and the target spot of the oil reservoir, and combining every two horizontal wells; a multi-stage well completion mode is adopted, and two underground well positions are implemented by using one well slot through track design; designing a bifurcated opening position and a main shaft pump position; in the initial stage of production, commingling production is carried out on the branch horizontal wells at the high, middle and low positions; and after the water content is increased, carrying out turn mining. The liquid amount treatment requirement in the peak period is only 50% of that of a conventional design, and when the branch well subjected to cone pressing is opened for independent production, the obvious water reducing and oil increasing effects are achieved. According to the method, the design problems that the required number of bottom water reservoir development well slots is large and the requirement for the liquid amount processing capacity is high can be solved, the economic benefits of bottom water reservoir development can be improved, and a design basis is provided for offshore oil reservoir development.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development and exploitation, and in particular to a bottom water reservoir cone wheel production and exploitation design method based on a double-branch horizontal well. Background Art

[0002] During the development of offshore reservoirs with strong bottom water, horizontal wells are often used to reduce the production pressure differential and thus slow bottom water coning. Although horizontal wells increase the drainage area, they still exhibit rapid water cut increases, high single-well liquid production, and prolonged periods of high water cut during development. 70% of a well's cumulative oil production occurs after the water cut reaches 90%. The development of offshore bottom water reservoirs requires long-term operation under high water cuts and high liquid volumes. As production progresses, the oilfield's demand for the offshore platform's liquid handling capacity and platform slot resources gradually increases, posing a significant challenge to the development of offshore bottom water reservoirs. Therefore, reducing the field's peak liquid volume and utilizing the platform's limited slot resources to maximize geological reserves are key to the efficient development of offshore bottom water reservoirs.

[0003] Traditional development design for bottom-water reservoirs relies on conventional horizontal well deployment, characterized by the following characteristics: 1) One horizontal well is deployed per slot; 2) All horizontal wells deployed in the reservoir are put into production sequentially, with the water cut rapidly increasing as production progresses, typically reaching over 90% within three months, after which the rate of increase gradually slows; 3) Once the water cut reaches 95% or higher, high-volume production is maintained, typically maintaining a well production rate of 2,000 cubic meters per day, until the field reaches its peak liquid production; 4) During peak liquid processing, individual wells must be shut down when daily production drops below a certain threshold. After shut-in, new adjustment wells are drilled using the released slot resources. This conventional design approach, when applied to offshore bottom-water reservoir development, requires more slot resources and increased liquid handling capacity. This results in oversized offshore platforms, reducing the economic viability of bottom-water reservoir development and leading to the failure of many bottom-water reservoirs to be effectively developed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical problems and propose a design method for cone-wheel production and development of bottom water reservoirs based on double-branch horizontal wells.

[0005] To achieve the above objectives, this application provides the following technical solutions:

[0006] A design method for cone-turbine production and development of bottom water reservoirs based on double-branch horizontal wells includes the following steps:

[0007] S1. Collect basic data of target reservoir;

[0008] S2. Determine the well thickness limit based on the target reservoir basic data;

[0009] S3. Determine the horizontal well type based on the target reservoir basic data;

[0010] S4. Determine the number and location of wells in the reservoir and obtain target points;

[0011] S5. Combine two underground horizontal wells horizontally or vertically to form a branch horizontal well;

[0012] S6. Using a single well slot, perform a multi-stage completion design, enabling one well slot to accommodate two underground well locations.

[0013] S7. Design the bifurcation and main wellbore pump locations based on the characteristics of the tubing string. Design the bifurcation to be located in the middle of the wellbore depth, with the main wellbore pump installed near the bifurcation.

[0014] S8. Determine the time for combined production of each branch based on the numerical modeling results. In the early stages of production, adopt a combined production method.

[0015] S9. Determine the single production time for high, middle, and low oil sections based on the oil column height and combined with viscosity, geological reservoir factors;

[0016] S10. After the combined production time, carry out rotation production and close one of the two branches of the branch horizontal well M a Press the cone to make another branch M b Sole mining;

[0017] S11. Branch M b When the single collection time is reached, close branch M b , reopen another branch M a ;

[0018] S12. Branch M a When the single collection time is reached, close branch M a , reopen another branch M b ;

[0019] S13. Similarly, according to step S10, repeat steps S11 and S12 until the single well shutdown condition is met.

[0020] Furthermore, in step S1, based on the target block fluid and special core test data, the reservoir characteristic parameters of different layers are collected and organized. The basic data of the target reservoir include formation crude oil viscosity, reservoir permeability, water body energy, reservoir type, reserve scale, maximum liquid volume per well, phase permeability curve, single well production capacity of oil well, crude oil density and oil layer thickness.

[0021] Further, in step S2, based on the reservoir basic data of the target block, with the preset tonnage of cumulative oil production per well as the objective function, the cumulative oil production index per well under different well placement thickness limits is obtained through numerical simulation research, and the relationship diagram between the cumulative oil production per well and the well placement thickness is plotted. The well placement thickness when the preset tonnage of the cumulative oil production per well objective function is reached is the well placement thickness limit.

[0022] Further, in step S3, the horizontal well types include conventional horizontal wells and long horizontal wells.

[0023] Further, in step S4, combining the basic geological reservoir parameters of the target block, according to the expected recovery rate of the bottom water reservoir and the target of increased oil production per well, the number of wells in the reservoir is determined, the well positions are optimized, and the horizontal well target points of the target reservoir are obtained; the relationship between the number of wells in the reservoir and the recovery rate: after the number of wells increases to a certain amount, increasing the number of wells further, the change in the recovery rate is not significant. Determine the total number of horizontal wells to be arranged in the reservoir, and obtain the target point coordinates of each well.

[0024] Further, in step S5, according to the pairwise combination of well trajectory, plane position, physical property differences of the horizontal sections of two wells, and oil column height factors, multiple pairs of branched horizontal wells are formed by horizontal well plane combination, and the horizontal wells located at the high, middle, and low positions are pairwise combined.

[0025] Further, in step S6, a double-branched horizontal well layout is designed, and the azimuths of the two branches are approximately parallel.

[0026] Further, in step S7, considering the influence of the opening degree of the two horizontal branches on the horizontal section spacing, the bifurcation point needs to be moved up as much as possible to leave enough space for build-up; considering the problem of trajectory anti-collision, a position with sparse surrounding trajectories needs to be selected as the bifurcation point to increase the separation coefficient between trajectories; considering that the pump setting depth needs to be above or adjacent to the bifurcation point position, and the production pump needs to be deepened as much as possible to be close to the oil layer, the bifurcation point position needs to be moved down as much as possible, preferably below the dynamic liquid level.

[0027] Further, in step S8, through numerical simulation research, it is determined to adopt the combined production method in the initial production stage, and the highest cumulative oil production is taken as the recommended combined production time.

[0028] Further, in step S9, the single production time of the high-position branch well is 3 years, the single production time of the middle-position branch well is 2.5 years, and the single production time of the low-position branch well is 2 years.

[0029] In summary, the technical effects and advantages of the present invention are as follows: based on the determination of the basic parameters of the geological reservoir in the target block, the present invention determines the well thickness limit and the horizontal well type, determines the number of reservoir wells, well locations and targets according to relevant indicators, and performs pairwise combinations of horizontal wells. Then, a multi-stage completion mode is adopted, and two underground well locations are implemented using one well slot through trajectory design, thereby reducing the number of well slots required for the bottom water reservoir and reducing the platform scale. Then, based on the demonstration results of the combined production time and the single production time, combined production is carried out during the low water content and low liquid production period, and rotation production is carried out after the water content rises, and then the cycle is repeated. This technical method can effectively reduce the scale of liquid treatment and well slot design for such bottom water reservoirs, thereby greatly improving the economic benefits of the development of such bottom water reservoirs, and providing a design basis for the development of such offshore reservoirs. The present application can solve the design problems of a large number of well slots required for the development of bottom water reservoirs and high liquid processing capacity requirements, and can effectively reduce the scale of liquid treatment and well slot design for such bottom water reservoirs, greatly improving the economic benefits of the development of such bottom water reservoirs, and providing a design basis for the development of such offshore reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a flow chart of a method for designing and developing a double-branch horizontal well in a bottom water reservoir according to a first embodiment of the present invention;

[0032] Figure 2 This is a graph showing the relationship between the oil column height and the cumulative oil production of a single well in a bottom water reservoir in Example 1 of the present invention;

[0033] Figure 3 Schematic diagram of the principle of well layout in the high, middle and low parts of the bottom water reservoir in the first embodiment of the present invention;

[0034] Figure 4 This is a relationship diagram between the number of wells in a bottom water reservoir and the recovery factor in Example 1 of the present invention;

[0035] Figure 5 This is a schematic diagram of well layout in the high, middle and low parts of a bottom water reservoir in Example 1 of the present invention;

[0036] Figure 6 Schematic diagram of a combination of double-branch horizontal wells at high, middle and low locations in a bottom water reservoir in Example 1 of the present invention;

[0037] Figure 7 Schematic diagram of a double-branch horizontal well in a bottom water reservoir in Example 1 of the present invention;

[0038] Figure 8 Schematic diagram of the bifurcation point position of the dual-branch horizontal well in the bottom water reservoir in the first embodiment of the present invention;

[0039] Figure 9 Optimization relationship diagram of the initial combined production time of the dual-branch well in the bottom water reservoir in the first embodiment of the present invention;

[0040] Figure 10 Single production time at different high, medium, and low positions of the dual-branch horizontal well in the first embodiment of the present invention;

[0041] Figure 11 Comparison of the indexes between the design scheme and the conventional design scheme in the first embodiment of the present invention;

[0042] Figure 12 Oil-water relative permeability curve of Oilfield C in the second embodiment of the present invention;

[0043] Figure 13 Relationship diagram between the oil column height and the cumulative oil production per well in Oilfield C in the second embodiment of the present invention;

[0044] Figure 14 Schematic diagram of the heel and toe of the horizontal section in Oilfield C in the second embodiment of the present invention;

[0045] Figure 15 Relationship chart of different well numbers and recovery factor in Oilfield C in the second embodiment of the present invention;

[0046] Fig.16 Well pattern diagram of the bottom water reservoir in Oilfield C in the second embodiment of the present invention;

[0047] Figure 17 Combination schematic diagram of the dual-branch horizontal well in the bottom water reservoir of Oilfield C in the second embodiment of the present invention;

[0048] Figure 18 Optimization of different combined production times of the dual-branch horizontal well in Oilfield C in the second embodiment of the present invention;

[0049] Fig.19 Optimization of single production time at different high, medium, and low positions in Oilfield C in the second embodiment of the present invention;

[0050] Fig. 20 Comparison of the indexes between the design scheme and the conventional design scheme in Oilfield C in the second embodiment of the present invention. Specific implementation manner

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] The object of the present invention is to provide a development design method for dual-branch horizontal wells in bottom water reservoirs, which can solve the design problems of large demand for the number of development wellbores and high demand for liquid handling capacity in the above-mentioned bottom water reservoirs, thereby reducing the scale of offshore platforms and improving the economic efficiency of offshore bottom water reservoir development, and providing a basis for aspects such as the configuration of dual-branch wells in oilfields, production systems, and completion methods.

[0054] Embodiment 1

[0055] This embodiment provides a pressure cone wheel production development design method for bottom water reservoirs based on dual-branch horizontal wells, which is highly operable and widely applicable. As Figure 1 shown, it mainly includes the following steps:

[0056] The first step is to collect the basic data of the target reservoir. Collect the basic data required for geological reservoir scheme design, such as the crude oil viscosity, reservoir permeability, oil column height, and relative permeability of the target reservoir, as shown in Table 1 specifically.

[0057] Table 1 Example table of basic data required for geological reservoir scheme design

[0058]

[0059] The second step is to determine the well placement thickness limit according to the basic data of the target reservoir. For example, in this embodiment, with the cumulative oil production per well of 43,000 tons as the objective function, the cumulative oil production index per well under different well placement thickness limits is obtained through numerical simulation. Taking the well placement thickness as the X-axis and the cumulative oil production per well as the Y-axis, draw the relationship diagram between the cumulative oil production per well and the well placement thickness. The well placement thickness when the cumulative oil production per well reaches the objective function of 43,000 tons is 9.0 m, which is the well placement thickness limit, as specifically shown in Figure 2 .

[0060] The third step is to determine the type of horizontal well according to productivity, structural amplitude, etc. The types of horizontal wells include conventional horizontal wells and long horizontal wells. Classification is carried out according to the length of the horizontal well. In this embodiment, considering the heterogeneity of the formation (the horizontal section level difference is less than 5) and the water avoidance thickness difference (H toe - H heel) not exceeding 5 m (that is, the water avoidance thickness difference between the toe and heel of the horizontal well is less than 5 m), the length of the horizontal well is determined to be 400 - 600 m. As Figure 3 .

[0061] Step 4: Determine the number and locations of wells in the reservoir to obtain the target points. Based on the expected recovery rate of the bottom water reservoir, the incremental oil production per well, and other objectives, determine the number of wells in the reservoir, optimize the well locations, and obtain the horizontal well target points of the target reservoir. In this embodiment, as Figure 4 shown, regarding the relationship between the number of wells in the reservoir and the recovery rate, after the number of wells increases to 6, further increasing the number of wells results in little change in the recovery rate. Six wells are the optimal solution. As Figure 5 shown, based on the geological characteristics and development objectives of the reservoir, it is determined that a total of 6 horizontal wells (H1 - H6) need to be arranged in the reservoir, and the target point coordinates of each well are obtained.

[0062] Step 5: Combine the underground horizontal well locations pairwise in the plane or longitudinally to form a single branched horizontal well. Combine them pairwise according to factors such as well trajectories, planar positions, physical property differences in the horizontal sections of the two wells, and oil column height. As Figure 6 shown, the 6 horizontal wells are combined in the plane to form 3 pairs of branched horizontal wells M a高 and M b高 , M a中 and M b中 , M a低 and M b低 .

[0063] Step 6: Use a single wellbore to conduct a multi - stage completion design so that two underground well locations can be implemented in one wellbore, as Figure 7 shown.

[0064] Implement the multi - stage completion design: Adopt multi - stage completion technology at each well location to achieve precise control and efficient exploitation of two well locations in one wellbore. Design the layout of the double - branched horizontal well. The azimuths of the two branches are approximately parallel, and the spacing needs to be minimized under the premise of considering no mutual interference during the production process to ensure full utilization of underground resources.

[0065] Step 7: Considering the well depth and the liquid production of the two branched wells, design the position of the bifurcation point and determine the position of the main wellbore pump. The bifurcation point is designed to be located in the middle of the well depth, and the main wellbore pump is installed near the bifurcation point. Figure 8 shown.

[0066] The position of the bifurcation point of the double - branched well trajectory needs to comprehensively consider the horizontal branch spacing, trajectory anti - collision, pump setting depth, and fluid level. As Figure 8 shown, considering the influence of the opening of the two horizontal branches on the horizontal section spacing, the bifurcation point needs to be moved upwards as much as possible to leave enough build - up space. Considering the trajectory anti - collision problem, a position with sparse surrounding trajectories needs to be selected as the bifurcation point to increase the separation coefficient between trajectories. Considering the pump setting depth, it needs to be above or adjacent to the bifurcation point, and the production pump needs to be deepened as much as possible close to the oil layer. The bifurcation point needs to be moved downwards as much as possible, preferably below the fluid level, to ensure that the production pump can generate sufficient lifting force.

[0067] Step 8: Determine branch M based on the numerical simulation results a and branch M b The combined mining time T 合 .like Figure 9 shown.

[0068] Through numerical simulation research, it was determined that commingled production should be adopted in the early stage of production to quickly increase production. The initial commingled production time was designed to be 1 year, 2 years, and 3 years respectively. The one with the highest cumulative oil production was finally recommended as the commingled production time T. 合 .

[0069] The ninth step is to determine the single production time T of different parts of high, medium and low oil column according to the oil column height and geological reservoir factors such as viscosity. 单 (T 高单 、T 中单 、T 低单 ).like Figure 10 shown.

[0070] Through numerical simulation, considering the differences in oil column height, crude oil density, structural amplitude, etc., the degree of water cone drop after shutting in oil wells in high, medium and low positions was studied respectively, and optimization was carried out by shutting in wells for 1.0, 2.0, 2.5, 3.0 and 4.0 years respectively. After optimization, it takes 3 years, 2.5 years and 2 years for the water cone in high, medium and low positions to fall back to the interface. That is, the high position wells need to be shut down for 3 years before being opened for separate production to achieve the best cone pressure effect, and the medium and low positions need to be shut down for 2.5 years and 2 years before being opened for separate production to achieve the best cone pressure effect. Therefore, the single production time of high, medium and low positions is set to =T 高单 、T 中单 、T 低单 They are 3 years, 2.5 years and 2 years respectively.

[0071] Step 10. Close branch M a , single pick another branch M b .

[0072] Formulate the mining order: first branch M a Perform apheresis and reach apheresis time T 单 (T 高单 、T 中单 、T 低单 ) and then close M a , open branch M b Perform apheresis. b Reaching apheresis time T 单 (T 高单 、T 中单 , T low order), close M b , restart M a Carry out single mining, and so on and so forth in this order of mining.

[0073] Step 11, M b Reaching apheresis time T 单 (T 高单 , T 中单 , T 低单 ) and then close M b , reopen another branch M a .

[0074] Step 12, M a Reaching apheresis time T 单 (T 高单 , T 中单 , T 低单 ) and then close M a , reopen another branch M b .

[0075] Step 13. Repeat steps 11 and 12 according to step 10, and so on, until the single well shutdown condition is met.

[0076] In the early stage of production, the branch horizontal wells at high, medium and low positions are combined for production; after the water cut rises, one of the two branches of the branch horizontal well is closed. a Press the cone to make another branch M b Separate mining, usually high-level branch wells (M 高 ) Produce T alone 高单 3 years, the middle branch wells (M 中 ) Production T 中单 2.5 years, low-lying branch wells (M 低 ) Production T 低单 2 years; after the expiration of the independent mining period, the branch horizontal well M b Press the cone to open the previously closed branch M a Mined separately, waiting for M a When the time for solo mining is up, close branch M a Open branch M b , and then the cycle repeats. Single-well shut-in conditions are state-of-the-art. For example, daily fluid production cannot exceed a set value, the minimum bottomhole pressure cannot fall below a set value, and the well is automatically shut down when the water cut exceeds 95%. These set values are determined based on specific operating conditions.

[0077] The technical method provided by the present invention determines the thickness limit of well layout and the type of horizontal wells based on the basic parameters of the geological reservoir in the target block, and then determines the number of reservoir wells, well locations and target points according to relevant indicators, and then combines the horizontal wells in pairs. Then, a multi-stage completion mode is adopted to implement two underground well locations using one well slot through trajectory design, thereby reducing the number of well slots required for bottom water reservoirs and reducing the platform scale. Then, based on the demonstration results of combined production time and single production time, combined production is carried out during the low water content and low liquid production period, and rotation production is carried out after the water content rises. This technical method can effectively reduce the liquid treatment and well slot design scale of such bottom water reservoirs, thereby greatly improving the economic benefits of the development of such bottom water reservoirs and providing a design basis for the development of such offshore reservoirs (see Table 2 and Figure 11 ).

[0078] Table 2: Comparison of key parameters between the method of this embodiment and the conventional method design scheme

[0079]

[0080]

[0081] Example 2

[0082] The double-branch horizontal well development design is now carried out based on the basic parameters of a C bottom water oilfield. The basic parameters are: the reservoir depth is -1500m to -1830m, the average porosity is 30.5%, and the average permeability is 2400×10 -3 μm 2 The production layer is Guantao Formation, which is divided into Guantao Formation I oil group and Guantao Formation III oil group. The viscosity of Guantao Formation I oil group is 523mPa·s, and the viscosity of Guantao Formation III oil group crude oil is 296mPa·s.

[0083] This embodiment provides a dual-branch horizontal well development design method, including:

[0084] The first step is to collect basic data of the target reservoir. Collect the basic data required for geological reservoir design, such as crude oil viscosity, reservoir permeability, oil column height, phase permeability curve, etc. Figure 12 .

[0085] Table 3C Oilfield Basic Data

[0086]

[0087] The second step is to determine the well thickness limit based on the basic data of the target reservoir. Taking the cumulative oil production of 70,000 tons per well as the target function, numerical simulation is conducted to obtain the cumulative oil production index of a single well under different well thickness limits. With the well thickness as the X-axis and the cumulative oil production of a single well as the Y-axis, a relationship diagram of the cumulative oil production of a single well and the well thickness is drawn. The thickness that reaches the target cumulative oil production of a single well is the well thickness limit. Figure 13 In Oilfield C, the cumulative oil production per single well needs to reach over 70,000 tons, and the well placement thickness limit is 15 m.

[0088] In the third step, determine the horizontal well length based on productivity, structure, physical properties of the horizontal section, etc. Considering the heterogeneity of the formation (it is recommended that the permeability ratio of the horizontal section is less than 5) and the water avoidance thickness difference (H toe - H heel) does not exceed 5 m (i.e., the water avoidance thickness difference between the toe and heel of the horizontal well is less than 5 m), determine the horizontal well length. For example, Figure 14 Based on the actual situation of Oilfield C, determine the horizontal well length to be 400 - 800 m.

[0089] In the fourth step, determine the number of wells and well locations in the reservoir to obtain the target points. According to the expected recovery rate of the bottom - water reservoir, the incremental oil production per single well and other targets, determine the number of wells in the reservoir, optimize the well locations, and obtain the horizontal well target points of the target reservoir.

[0090] For example, Figure 15 The relationship diagram between the number of wells and the recovery rate shows that in the initial stage, as the number of wells increases, the recovery rate increases significantly. When the number of wells exceeds 12, the incremental recovery rate becomes significantly slower. Therefore, a 12 - horizontal - well plan is recommended. As Fig.16 shown, according to the reservoir geological characteristics and development targets, it is determined that a total of 12 horizontal wells (A1H - A12H) need to be arranged in the reservoir, and the target point coordinates of each well are obtained.

[0091] In the fifth step, combine the underground horizontal well locations pairwise in the plane or longitudinally to form a branched horizontal well. Combine them pairwise according to factors such as well trajectories, plane positions, physical property differences of the horizontal sections of the two wells, and oil column height. For example, Figure 17 shown, 12 horizontal wells are combined pairwise in the plane to form 6 pairs of branched horizontal wells. Among them, A1Ma and A1Mb are high - position wells, A2Ma and A2Mb, A3Ma and A3Mb are middle - position wells, and A4Ma and A4Mb, A5Ma and A5Mb, A6Ma and A6Mb are low - position wells.

[0092] In the sixth step, use one wellbore to conduct a multi - stage completion design so that two underground well locations can be implemented in one wellbore. The principle is the same as that of Embodiment 1, as Figure 7 shown.

[0093] Implement the multi - stage completion design: Adopt multi - stage completion technology at each well location to achieve precise control and efficient exploitation of two well locations in one wellbore. Design a double - branched horizontal well layout. The azimuths of the two branches are approximately parallel, and the spacing needs to be minimized on the premise of considering no mutual interference during the production process to ensure the full utilization of underground resources.

[0094] The seventh step is to design the bifurcation position based on the well depth and the production volume of the two branch wells, and determine the position of the main wellbore pump. The bifurcation position is designed to be in the middle of the well depth, and the main wellbore pump is installed near the bifurcation. The principle is the same as in Example 1. Figure 8 shown.

[0095] The bifurcation point position of the double-branch well trajectory needs to comprehensively consider the horizontal branch spacing, trajectory collision prevention, pump hanging depth and dynamic liquid level. Figure 8 As shown, considering the impact of the opening of the two horizontal branches on the spacing between horizontal sections, the bifurcation point needs to be moved upward as much as possible to leave sufficient space for deflection. To prevent collisions between tracks, the bifurcation point should be selected at a location with sparse surrounding tracks to increase the separation coefficient between tracks. Considering that the pump hanging depth needs to be above or near the bifurcation point and the production pump needs to be as deep and close to the oil layer as possible, the bifurcation point should be moved downward as much as possible, below the dynamic liquid level, to ensure that the production pump can generate sufficient lifting force.

[0096] Step 8: Determine branch M based on the numerical simulation results a and M b The combined mining time T 合 The numerical simulation results of C oilfield show that when the combined production time T 合 When the cumulative oil production is the highest at 2 years ( Figure 18 As shown), determine branch M a and M b The combined mining time T 合 For 2 years.

[0097] The ninth step is to determine the single production time T of different parts of high, medium and low oil column according to the oil column height and geological reservoir factors such as viscosity. 单 (T 高单 、T 中单 、T 低单 ).

[0098] Through numerical simulation, it is determined that the combined production method should be adopted in the early stage of oil well production to quickly increase production. According to the differences in oil column height and viscosity, the cumulative oil of different wells in high, medium and low positions under different rotation production cycles is recommended, and the highest cumulative oil is the recommended single production time. 单 (T 高单 、T 中单 、T 低单 ). C oil field T 单 (T 高单 、T 中单 、T 低单 ) are 3 years, 2.5 years and 2 years respectively (e.g. Fig.19 shown).

[0099] Step 10: After the combined mining time T 合 After that, close branch M a , single pick another branch Mb .

[0100] Formulate the mining order: first branch M a Perform single collection and reach the single collection time (high, medium and low parts T 高单 、T 中单 、T 低单 M will be closed after 3 years, 2.5 years and 2 years respectively a , open branch M b Perform apheresis. b Time to single collection (high, medium and low parts T 高单 、T 中单 、T 低单 After 3 years, 2.5 years and 2 years respectively, the M b , restart M a Perform single collection, and so on.

[0101] Step 11, M b Time to single collection (high, medium and low parts T 高单 、T 中单 、T 低单 After 3 years, 2.5 years and 2 years respectively, the M b , reopen another branch M a .

[0102] Step 12, M a Time to single collection (high, medium and low parts T 高单 、T 中单 、T 低单 After 3 years, 2.5 years and 2 years respectively, the M a , reopen another branch M b .

[0103] Step 13. Repeat steps 11 and 12 according to step 10, and so on, until the single well shutdown condition is met.

[0104] In the early stage of production, the branch horizontal wells at high, medium and low positions are combined for production; after the water cut rises, one of the two branches of the branch horizontal well is closed. a Press the cone to make another branch M b Separate mining, usually high-level branch wells produce separately 高单 In 3 years, the middle branch wells produced T 中单 2.5 years, low-lying branch well production T 低 Single 2 years; after the independent mining period is up, close the branch horizontal well M b Press the cone to open the previously closed branch M a Mined separately, waiting for M a When the time for solo mining is up, close branch Ma Open branch M b , and then the cycle repeats.

[0105] The technical method provided in this embodiment determines the well thickness limit and horizontal well type based on the basic parameters of the geological reservoir in the target block, and then determines the number of reservoir wells, well locations and target points according to relevant indicators, and then combines the horizontal wells in pairs. Then, a multi-stage completion mode is adopted to implement two underground well locations using one well slot through trajectory design, thereby reducing the number of well slots required for bottom water reservoirs and reducing the platform scale. Then, based on the demonstration results of the combined production time and the single production time, the initial production period is the low water content and low liquid production period. After the combined production time, that is, after the water content rises, rotation production is carried out. This technical method can effectively reduce the liquid treatment and well slot design scale of such bottom water reservoirs, thereby greatly improving the economic benefits of the development of such bottom water reservoirs and providing a design basis for the development of such offshore reservoirs (see Table 4 and Fig. 20 ).

[0106] Table 4: Comparison of key parameters between the method of this embodiment and the conventional method design scheme

[0107]

[0108] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0109] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A design method for pressure cone wheel production development of bottom water reservoir based on dual-branch horizontal well, characterized in that It includes the following steps: S1. Collect basic data of the target reservoir; S2. Determine the well placement thickness limit according to the basic data of the target reservoir; S3. Determine the type of horizontal well according to the basic data of the target reservoir; S4. Determine the number of wells and well locations in the reservoir to obtain the target points; S5. Combine the underground horizontal well locations pairwise in the plane or longitudinally to form a multilateral horizontal well; S6. Use one wellbore to conduct multistage completion design so that two underground well locations can be implemented in one wellbore; S7. According to the characteristics of the pipe string, design the position of the bifurcation point and the position of the main wellbore pump. The bifurcation point is designed to be in the middle of the well depth, and the main wellbore pump is installed near the bifurcation point; S8. Through the numerical simulation results, determine the combined production time of each branch. In the initial production stage, adopt the combined production method; S9. According to the oil column height, combined with viscosity and geological reservoir factors, determine the single production time of the high, middle, and low parts; S10. After the combined production time, cyclic production is carried out, and one of the two branches of the branched horizontal well, branch M, is closed. a Cone fracturing is performed to allow the other branch M b to be produced separately; Branch M in S11 b After reaching the apheresis time, close Branch M b , reopen another Branch M a ; S12. Branch M a After reaching the apheresis time, close Branch M a , reopen another Branch M b ; S13. And so on. According to step S10, repeat steps S11 and S12 until the single well shutdown condition is touched.

2. The design method for pressure cone wheel production development of bottom water reservoir based on dual-branch horizontal well according to claim 1, characterized in that, In step S1, based on the fluid and special core test data of the target block, collect and sort out the reservoir characteristic parameters of different horizons. The basic data of the target reservoir includes formation crude oil viscosity, reservoir permeability, water body energy, reservoir type, reserve scale, maximum liquid volume per well, relative permeability curve, single well productivity of oil wells, crude oil density, and oil layer thickness.

3. The design method for pressure cone wheel production development of bottom water reservoir based on dual-branch horizontal well according to claim 1, characterized in that, In step S2, based on the reservoir basic data of the target block, with the preset tons of cumulative oil production per well as the objective function, obtain the cumulative oil production index per well under different well placement thickness limits through numerical simulation research, draw the relationship diagram between cumulative oil production per well and well placement thickness, and the well placement thickness when the preset tons of the cumulative oil production objective function per well is reached is the well placement thickness limit.

4. The design method for bottom water reservoir pressure cone wheel production and development based on double-branch horizontal wells according to claim 1 is characterized in that: In step S3, the types of horizontal wells include conventional horizontal wells and long horizontal wells.

5. The cone-breaking wheel production development design method for bottom water reservoirs based on dual-branch horizontal wells according to claim 1, characterized in that, In step S4, combined with the basic geological reservoir parameters of the target block, according to the expected recovery rate of the bottom water reservoir and the target of increased oil production per well, determine the number of wells in the reservoir, optimize the well locations, and obtain the horizontal well target points of the target reservoir. The relationship between the number of wells in the reservoir and the recovery rate: after the number of wells increases to a certain amount, increasing the number of wells further will not result in much change in the recovery rate. Determine the total number of horizontal wells to be arranged in the reservoir and obtain the target point coordinates of each well.

6. The design method for pressure cone wheel production development of bottom water reservoir based on double-branch horizontal well according to claim 1, characterized in that In step S5, according to factors such as well trajectory, plane position, physical property differences of the horizontal sections of two wells, and oil column height, combine them pairwise. The horizontal wells are combined pairwise in the plane to form multiple pairs of multilateral horizontal wells, and the horizontal wells located in the high, middle, and low parts are combined pairwise.

7. The design method for bottom water reservoir pressure cone production and development based on double-branch horizontal wells according to claim 1 is characterized in that: In step S6, design the layout of the double-branch horizontal well, and the azimuths of the two branches are approximately parallel.

8. The cone driving and wheel production development design method for bottom water reservoirs based on dual-branch horizontal wells according to claim 1, characterized in that, In step S7, considering the influence of the opening of the two horizontal branches on the horizontal section spacing, the bifurcation point needs to be moved up as much as possible to leave enough build-up space; considering the trajectory anti-collision problem, a position with sparse surrounding trajectories needs to be selected as the bifurcation point to increase the separation coefficient between trajectories; considering that the pump setting depth needs to be above or adjacent to the bifurcation point, and the production pump needs to be deepened as much as possible to be close to the oil layer, the bifurcation point position needs to be moved down as much as possible, preferably below the flowing fluid level.

9. The design method for bottom water reservoir pressure cone wheel production and development based on double-branch horizontal wells according to claim 1, characterized in that: In step S8, through numerical simulation research, determine to adopt the combined production method in the initial production stage, and the recommended combined production time is when the cumulative oil production is the highest.

10. The design method for bottom water reservoir pressure cone wheel production and development based on double-branch horizontal wells according to claim 1, characterized in that: In step S9, the single production time of the high-position branch well is 3 years, the single production time of the middle-position branch well is 2.5 years, and the single production time of the low-position branch well is 2 years.

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