Strong heterogeneous oil reservoir old well sidetrack horizontal well design method and system

Abstract

The invention provides a strong heterogeneous oil reservoir old well sidetrack horizontal well design method and system.The method comprises the steps that a high-permeability layer section in a reservoir is recognized, and the relative position relation between a well track of a horizontal section of an existing horizontal well and a high-permeability layer is determined; researching an oil reservoir flooding mode, and researching and depicting a remaining oil distribution rule according to the oil reservoir flooding mode; determining an optimal horizontal well trajectory type of oil reservoir development based on production dynamic data in combination with the relative position relationship between the well trajectory and the high-permeability layer; and according to the remaining oil distribution rule and the existing horizontal well horizontal section well trajectory production research, a sidetracking well target layer of the oil reservoir development horizontal well trajectory is determined, and the well trajectory of the sidetracking horizontal well is optimized. A horizontal well sidetrack drilling track and a construction scheme are optimized, the development effect of sidetrack drilling of a new well is maximized, meanwhile, the old well sidetrack drilling technology and the water plugging technology are combined, the sidetrack drilling scheme is optimized and designed, and compared with common sidetrack drilling, the measure yield increasing effect can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of well logging, and in particular relates to a method and system for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs. Background Art

[0002] Strongly heterogeneous reservoirs developed through horizontal wells are characterized by significant variations in permeability within the reservoir. Due to the presence of high-permeability strata, these reservoirs experience a short water-free recovery period after full waterflooding, rapid water-cut increases, and significant challenges in stabilizing production and controlling water. This is primarily due to the ease with which injected water can channel through the high-permeability strata, leading to rapid flooding of these strata and persistently high water cuts in producing wells. This in turn hinders the effective utilization of the remaining oil in the low-permeability strata, resulting in high water cuts and low production rates for individual horizontal wells and even for the entire reservoir. For these high-water-cut, low-production reservoirs, the well pattern is largely defined and well locations are typically already established. Adding new wells is challenging, as new well locations may conflict with existing ones or simply be unavailable. Furthermore, due to reservoir heterogeneity, the effectiveness of injection-production optimization is limited. Furthermore, long-term production can lead to wear and blockage in the horizontal wellbore, making reentry difficult and preventing profile testing and water shutoff operations. Therefore, horizontal well development of highly heterogeneous reservoirs presents certain difficulties and challenges in terms of waterflooding, oil stabilization and water control, wellbore reentry, and injection-production optimization. Therefore, the development of such reservoirs requires targeted technologies and methods to improve the efficiency and economic benefits of oilfield development.

[0003] Sidetracking a horizontal well is a specialized drilling technique that utilizes specialized sidetracking tools to deviate the drill bit's trajectory from the original wellbore trajectory according to a pre-designed deviation. This technology plays a crucial role in oilfield development, particularly in restoring production from older wells and tapping remaining oil potential. Sidetracking older wells can effectively improve development outcomes and enhance oilfield profitability. Compared to drilling new wells, sidetracking older wells requires less investment and costs, saving approximately half the cost. For horizontal wells in high-water-cut reservoirs, sidetracking older wells can unlock new production capacity, thereby improving oilfield development profitability. For horizontal wells in highly heterogeneous reservoirs, sidetracking can be used to adjust the well trajectory to stabilize production and control water content. This method not only improves oilfield development profitability but also effectively taps remaining oil potential, thereby enhancing oilfield development efficiency. However, to avoid the negative impact of high-permeability strata on new wellbore production, well trajectory design and water shutoff must be comprehensively considered during sidetracking design. Therefore, for horizontal wells in highly heterogeneous reservoirs, the use of sidetracking to adjust the well trajectory is essential. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a method for designing sidetracking horizontal wells in old wells in highly heterogeneous oil reservoirs, the method comprising:

[0005] Identify the high permeability layer in the reservoir and determine the relative position relationship between the horizontal well trajectory of the existing horizontal well and the high permeability layer;

[0006] Study on reservoir flooding pattern and characterize the distribution law of remaining oil based on the study on reservoir flooding pattern;

[0007] Determining the type of horizontal well trajectory for reservoir development based on production performance data and the relative position relationship between the well trajectory and the high permeability layer;

[0008] According to the distribution law of remaining oil and the production research of the horizontal section of existing horizontal well trajectories, the target layer of the sidetracking well trajectory of the horizontal well in oil reservoir development is determined, and the well trajectory of the sidetracking horizontal well is optimized.

[0009] Furthermore, the well trajectory of the sidetracked horizontal well is optimized by:

[0010] Create a seepage barrier within the hyperpermeable layer surrounding the existing wellbore and seal off the original well trajectory; and,

[0011] Determine the relationship between plugging agent dosage and expected economic benefits based on the plugging radius of different high permeability layers.

[0012] The dosage of plugging agent for high permeability layer is determined based on the economic evaluation results, and the high permeability layer of side drilling is plugged.

[0013] Furthermore, the amount of the high permeability layer plugging agent is determined by the high permeability layer plugging radius, redundancy coefficient, average thickness of the high permeability layer, length of the horizontal section and the ratio of the high permeability layer crossflow liquid volume to the total liquid volume.

[0014] Furthermore, the dosage formula of the high permeability layer plugging agent is expressed as:

[0015]

[0016] Among them, V represents the amount of plugging agent, a represents the redundancy coefficient, represents porosity, H represents the average thickness of the high permeability layer, L represents the length of the horizontal section, r represents the plugging radius, and f represents the ratio of the crossflow liquid volume in the high permeability layer to the total liquid volume.

[0017] Furthermore, identifying the high permeability layer in the reservoir and determining the relative position relationship between the horizontal well trajectory of the existing horizontal well and the high permeability layer includes:

[0018] Determine the distribution and characteristics of high permeability layers based on geological data;

[0019] According to the distribution and characteristics of high permeability layers, the well logging curves of the coring wells, the core thin sections of the corresponding cores, and the high permeability layer identification results of the porosity test, the method of identifying high permeability layers in the target reservoir based on the well logging curves is determined;

[0020] According to the high permeability layer identification method, the high permeability layer section is identified based on the horizontal well inclination data and the well logging curve data, and the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer is determined.

[0021] Furthermore, the research on reservoir flooding mode and the characterization of the remaining oil distribution law based on the research on reservoir flooding mode include:

[0022] Study the reservoir water flooding pattern based on the transit well logging data and production logging data;

[0023] Analyze the flow pattern of injected water in the reservoir and the differences in water-flooded intervals according to the reservoir water-flooding pattern;

[0024] The remaining oil distribution law is characterized according to the flow law and the difference in water-flooded intervals.

[0025] The present invention also provides a horizontal well design system for sidetracking old wells in highly heterogeneous oil reservoirs, the system comprising a first determination unit, a regularity characterization unit, a type determination unit and an optimization unit.

[0026] The first determining unit is used to identify a high permeability layer section in the reservoir and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer;

[0027] Regularity characterization unit, used for studying reservoir water flooding patterns and characterizing the remaining oil distribution pattern based on the reservoir water flooding patterns;

[0028] A type determination unit, configured to determine the type of a horizontal well trajectory for reservoir development based on production dynamic data in combination with a relative positional relationship between the well trajectory and the high permeability layer;

[0029] The optimization unit is used to determine the side-drilling target layer of the horizontal well trajectory of the oil reservoir development according to the remaining oil distribution law and the production research of the horizontal section of the existing horizontal well trajectory, and to optimize the side-drilling horizontal well trajectory.

[0030] Furthermore, the optimization unit includes a barrier module and a blocking module.

[0031] The barrier module is used to create a seepage barrier in the high-permeability layer around the existing wellbore and seal the original well trajectory;

[0032] The plugging module is used to determine the relationship between the amount of plugging agent and the expected economic benefits according to the plugging radius of different high-permeability layers, and to determine the amount of plugging agent for the high-permeability layer according to the economic evaluation results to plug the side-drilled high-permeability layer.

[0033] Furthermore, the amount of the high permeability layer plugging agent is determined by the high permeability layer plugging radius, redundancy coefficient, average thickness of the high permeability layer, length of the horizontal section and the ratio of the high permeability layer crossflow liquid volume to the total liquid volume.

[0034] Furthermore, the dosage formula of the high permeability layer plugging agent is expressed as:

[0035]

[0036] Among them, V represents the amount of plugging agent, a represents the redundancy coefficient, represents porosity, H represents the average thickness of the high permeability layer, L represents the length of the horizontal section, r represents the plugging radius, and f represents the ratio of the crossflow liquid volume in the high permeability layer to the total liquid volume.

[0037] Furthermore, the first determination unit includes a first determination module, an identification method determination module and a position determination module.

[0038] The first determination module is used to determine the distribution and characteristics of the high permeability layer based on geological data;

[0039] An identification method determination module is used to determine a method for identifying a high permeability layer in a target reservoir based on the distribution and characteristics of the high permeability layer, the well logging curve of the coring well, and the high permeability layer identification results of the core thin section and porosity test of the corresponding core;

[0040] The position determination module is used to identify the high permeability layer section according to the high permeability layer identification method and the horizontal well inclination data and logging curve data, and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer.

[0041] Furthermore, the regularity characterization unit includes a pattern determination module, a second determination module and a regularity characterization module.

[0042] Pattern determination module, used to study reservoir waterlogging patterns based on transit well logging data and production logging data;

[0043] The second determination module is used to analyze the flow pattern of injected water in the reservoir and the differences in water-flooded intervals according to the reservoir water-flooding pattern;

[0044] The law characterization module is used to characterize the remaining oil distribution law according to the flow law and the difference of the water-flooded layer sections.

[0045] The method and system for designing horizontal wells for sidetracking old wells in highly heterogeneous oil reservoirs of the present invention optimize the horizontal well sidetracking trajectory and construction plan, maximizing the development effect of sidetracking new wellbores. At the same time, the present invention combines the sidetracking technology of old wells with the water plugging technology to optimize the design of the sidetracking plan, which can greatly improve the production increase effect of the measures compared with ordinary sidetracking.

[0046] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 A schematic diagram of a process for designing a horizontal well sidetracking in an old well in a highly heterogeneous oil reservoir according to an embodiment of the present invention is shown;

[0049] Figure 2 A schematic diagram of the original well trajectory of a horizontal well in the prior art is shown;

[0050] Figure 3 A schematic diagram of adding a high permeability layer artificial seepage barrier to the original well trajectory in an embodiment of the present invention is shown;

[0051] Figure 4 A schematic diagram of the trajectory of cement plugging an original well in an embodiment of the present invention is shown;

[0052] Figure 5 A schematic diagram of plugging a high permeability layer encountered by a sidetrack well in an embodiment of the present invention is shown;

[0053] Figure 6 A schematic diagram of a sidetrack well trajectory in an embodiment of the present invention is shown;

[0054] Figure 7 shows a residual oil distribution pattern diagram in an embodiment of the present invention;

[0055] Figure 8 A schematic diagram showing significant differences in water cut rise patterns for different well trajectories in an embodiment of the present invention;

[0056] Figure 9 A schematic diagram of a water cut rise curve for sidetrack wells at different layers with the same fluid production is shown in an embodiment of the present invention;

[0057] Figure 10 A schematic diagram of an optimized sidetracking trajectory in an embodiment of the present invention is shown;

[0058] Figure 11 A schematic diagram of the optimal blocking distance calculation result in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0060] In an embodiment of the present invention, a method for designing a sidetracking horizontal well in an old well of a highly heterogeneous oil reservoir is provided. Figure 1 A schematic flow chart of a method for designing side-drilling horizontal wells in old wells of highly heterogeneous oil reservoirs according to an embodiment of the present invention is shown, the method comprising: identifying high-permeability layer segments within the reservoir, determining the relative positional relationship between the horizontal segment trajectory of existing horizontal wells and the high-permeability layer; studying the water-flooding pattern of the reservoir and characterizing the distribution law of the remaining oil based on the study of the water-flooding pattern of the reservoir; determining the trajectory type of the horizontal well for reservoir development based on production dynamic data in combination with the relative positional relationship between the well trajectory and the high-permeability layer; determining the side-drilling target layer of the horizontal well trajectory for reservoir development based on the residual oil distribution law and the production study of the horizontal segment trajectory of existing horizontal wells, and optimizing the trajectory of the side-drilling horizontal well.

[0061] In an embodiment of the present invention, a specific process is also described. Identifying the high permeability layer section in the reservoir and determining the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer includes: determining the distribution and characteristics of the high permeability layer based on geological data; determining a high permeability layer identification method for the target reservoir based on the logging curve according to the distribution and characteristics of the high permeability layer, the logging curve of the coring well, and the core thin section of the corresponding core and the high permeability layer identification results of the porosity test; identifying the high permeability layer section based on the high permeability layer identification method and the horizontal well inclination data and logging curve data of the horizontal well, and determining the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer.

[0062] Specifically, the development of high-permeability layers within the reservoir is determined using geological data such as core sections and porosity and permeability testing. These data provide detailed information on reservoir physical properties, including porosity, permeability, and rock type. Analysis of this data allows the distribution and characteristics of high-permeability layers to be identified. Based on this information, a log-based method for identifying high-permeability layers within the target reservoir is developed, combining well logs from coring wells with the high-permeability layer identification results from core sections and porosity and permeability testing of the corresponding cores. High-permeability intervals are then identified based on horizontal well inclination data and well logs. Ultimately, the relative positional relationship between the existing horizontal well production trajectory and the high-permeability layer is determined.

[0063] Specifically, the study of the reservoir water flooding pattern and the characterization of the remaining oil distribution law based on the study of the reservoir water flooding pattern include: studying the reservoir water flooding pattern based on the logging data of the pass well and the production logging data; analyzing the flow law of the injected water in the reservoir and the difference in the water flooded layer based on the reservoir water flooding pattern; and characterizing the remaining oil distribution law based on the flow law and the difference in the water flooded layer.

[0064] In the embodiments of the present invention, by combining well logging data with production logging data, such as resistivity logging data of newly drilled wells after water injection development and casing saturation logging, these data are analyzed in depth to summarize the water flooding pattern of the reservoir, analyze the flow pattern of the injected water in the reservoir and the water flooded intervals, and particularly in highly heterogeneous reservoirs, the water flooded intervals of different permeability intervals may vary greatly. On this basis, the distribution pattern of the remaining oil is further characterized, and the spatial distribution of the remaining oil-rich areas is clarified.

[0065] In an embodiment of the present invention, analyzing the impact of horizontal well trajectories on production and clarifying the optimal horizontal well trajectory type includes: based on production dynamic data, combining the relative position relationship between the well trajectory and the high permeability layer, analyzing the impact of the well trajectory on the production effect. Generally speaking, for oil reservoirs with developed high permeability layers, the longer the horizontal section of the production well passes through the high permeability layer or the closer the vertical distance to the high permeability layer is, the higher the oil well production capacity will be. However, it also faces problems such as a short waterless oil production period after water injection, a rapid increase in water content after water breakthrough, and difficulty in taking measures to stabilize oil and control water. Therefore, by analyzing the existing different horizontal well trajectories and production dynamic data, the production dynamic characteristics of wells with different horizontal well trajectories can be sorted out, and the well trajectory type that is most in need of development adjustment among the existing well trajectory types can be analyzed. At the same time, the horizontal well trajectory type that is most suitable for the development of the oil reservoir among the existing well trajectory types can also be clarified.

[0066] In the embodiment of the present invention, the confirmation of the optimal horizontal well trajectory type includes the lowest water content of the produced fluid under the requirement of a certain exact oil production rate. The exact oil production rate is determined based on actual use. In the embodiment of the present invention, the exact rate is not protected.

[0067] Defining the target layer of the sidetracked well and the design of the new horizontal section includes: based on the understanding of the distribution pattern of remaining oil and the impact of the existing horizontal well trajectory on production results, combined with reservoir numerical simulation, clarifying the target layer of the sidetracked well and optimizing the trajectory of the new horizontal section of the sidetracked well, including the target layer, length, production allocation, completion method, etc. of the horizontal section, to determine the best development parameters to achieve the greatest economic benefits.

[0068] In an embodiment of the present invention, optimizing the trajectory of a side-drilled horizontal well includes: creating a seepage barrier in the high-permeability layer around the existing wellbore and plugging the original wellbore trajectory; and determining the relationship between the amount of plugging agent used and the expected economic benefits based on different high-permeability layer plugging radii, determining the amount of plugging agent used to plug the high-permeability layer based on the economic evaluation results, and plugging the high-permeability layer. The optimization design of the high-permeability layer plugging scheme for side-drilled high-permeability layer plugging specifically includes: in order to reduce the adverse effects of high-permeability layer crossflow after side-drilling on the water drive development of the new wellbore, large-scale injection of plugging agents is required before side-drilling construction to create a seepage barrier in the high-permeability layer around the existing wellbore. The amount of plugging agent used is calculated by substituting different high-permeability layer plugging radii r into Formula 1. A numerical simulation model is used to simulate the oil-increasing effect under different high-permeability layer plugging radii. The conductivity after plugging is given by the indoor test results. The oil-increasing amount per ton of plugging agent in different plugging intervals is calculated, and the net present value is measured to clarify the relationship between the amount of plugging agent used and the expected economic benefits. The amount of plugging agent used to plug the high-permeability layer is determined based on the economic evaluation results. The formula for the amount of plugging agent used to plug the high-permeability layer is expressed as:

[0069]

[0070] Among them, V represents the amount of plugging agent, a represents the redundancy coefficient, represents porosity, H represents the average thickness of the high permeability layer, L represents the length of the horizontal section, r represents the plugging radius, and f represents the ratio of the crossflow liquid volume in the high permeability layer to the total liquid volume.

[0071] In the embodiment of the present invention, the optimization scheme of sidetracking potential tapping in highly heterogeneous reservoirs is described in detail with reference to specific drawings. Figure 2 The figure shows the original trajectory of the horizontal well in the prior art. Figure 2 In the middle, the original well trajectory of the horizontal well is located at the bottom of the low permeability layer close to the high permeability layer, and there is a low permeability layer below the high permeability layer; Figure 3 A schematic diagram of adding a high permeability layer artificial seepage barrier to the original well trajectory in an embodiment of the present invention is shown. Figure 3 In the process, a high permeability artificial seepage barrier is set at the contact point between the original well trajectory and the high permeability layer, and the horizontal section of the original well trajectory is further sealed with cement, such as Figure 4 As shown; Figure 5 The schematic diagram of plugging a high permeability layer when a side-drilled well encounters one in an embodiment of the present invention is shown. The dosage of plugging agent for the high permeability layer is determined based on the economic evaluation results. The high permeability layer is plugged around the side-drilled wellbore, and further side-drilling is performed to tap potential, forming an optimized horizontal well in the low permeability layer below the high permeability layer. Figure 6 shown.

[0072] In the embodiments of the present invention, a method for designing a sidetracking horizontal well in an old well of a highly heterogeneous oil reservoir is specifically described through a specific embodiment:

[0073] The K reservoir in the A oilfield is a porous carbonate reservoir with high-permeability strata. During waterflooding, the injected water in reservoirs with high-permeability strata tends to rapidly advance along the thief layers, leading to development challenges such as a short water-free oil production period, rapid increases in water cut, and low water-drive recovery rates. However, for thief-layer reservoirs developed using horizontal well patterns, production enhancement measures are limited after the well pattern is established, making development adjustments difficult. Large amounts of residual oil are difficult to mobilize due to their presence in low-permeability layers. When the distribution of residual oil is clear, sidetracking old wells is an effective method for tapping potential. Its cost is lower than that of densifying the well pattern, and it can directional drill into areas rich in residual oil, achieving the goal of reducing water loss, increasing production, and tapping the potential of the remaining oil.

[0074] Step 1:

[0075] At the bottom of K2-1, there is a high-permeability layer with a large permeability difference from other small layers. It is about 1.2m thick, with an average porosity of 18%, and a permeability ranging from 10-1000mD, with an average of 178mD. The rock type is sand-clast granular limestone, with pores mainly composed of intergranular pores and dissolved pores, and local dissolved caves. The pore connectivity is good, with pore-shrinking throats as the main type, and the main throat radius ranging from 4 to 25μm, which makes a major contribution to the permeability. It is an intermittent high-energy environment deposition. According to stratigraphic comparison and core well data comparison, the high-permeability layer is stably distributed throughout the area and has strong comparability. The thickness gradually becomes thinner from east to west, and the permeability gradually decreases. Combined with logging interpretation and seismic results, the planar distribution of the high-permeability layer can be depicted. The thickness of the entire area is 0.7-1.5m, with an average thickness of 1.2m. In the process of establishing the reservoir geological model, the horizontal well logging data is taken into account to clarify the distribution area and permeability of the high-permeability layer, and finally to clarify the relative position relationship between the horizontal well trajectory and the high-permeability layer, which is convenient for subsequent research.

[0076] Step 2:

[0077] In the present embodiment, after five years of waterflooding, the K reservoir's comprehensive water cut exceeded 60%, marking the initial stage of high water cut. However, its overall recovery rate is currently low, with the geological reserve recovery rate reaching 9.3%. This indicates an initial stage of high water cut and a low recovery rate, leaving a large amount of remaining oil trapped in the reservoir. Under the current well pattern and development method, the recovery rate of the main K2 layer at the end of the contract period is approximately 20%, so a large amount of remaining oil must be recovered during the high water cut phase.

[0078] Resistivity analysis of 66 newly drilled wells after waterflooding identified six types of waterlogging in the K2 reservoir: no waterlogging, K2-3 waterlogging, high permeability layer waterlogging, high permeability layer and K2-3 waterlogging, waterlogging below the high permeability layer, and K2-4 waterlogging. Injection wells are primarily located in the K2-3 layer. Injected water first floods the high permeability layer or K2-3 layer, then slowly moves upward from the bottom K2-3 and downward from the high permeability layer to the K2-2 layer. Initial water penetration is characterized by a medium-high water cut, but after this point, the water cut rises slowly, with the rate of increase significantly slowing.

[0079] Resistivity analysis of 66 newly drilled wells after waterflooding identified six types of waterlogging in the K2 reservoir: no waterlogging, K2-3 waterlogging, high permeability layer waterlogging, high permeability layer and K2-3 waterlogging, waterlogging below the high permeability layer, and K2-4 waterlogging. Injection wells are primarily located in the K2-3 layer. Injected water first floods the high permeability layer or K2-3 layer, then slowly moves upward from the bottom K2-3 and downward from the high permeability layer to the K2-2 layer. Initial water penetration is characterized by a medium-high water cut, but after this point, the water cut rises slowly, with the rate of increase significantly slowing.

[0080] Ultimately, the primary and secondary water flow pathways of the K2 reservoir, driven by the dominant factor of the high permeability layer, were identified. The primary water flow pathway: Injected water enters K2-2 along the K2-3 vertical axis of the well, then migrates horizontally through the high permeability layer, flooding the production well. The secondary water flow pathway: Water migrates horizontally along K2-3 to the lower portion of the well and then vertically upward to the high permeability layer of the well. The degree of flooding near the injection well is slightly higher.

[0081] Figure 7 The residual oil distribution pattern diagram in the embodiment of the present invention is shown. Figure 7 In the case of the high permeability layer of the wells near the production wells, the water saturation increased by 10%-30% within two years of water injection. The water saturation of the wells near the injection wells increased by 10%-35% within 2-4 years of water injection. This shows that the injected water first flooded the high permeability layer of the production wells. The flooding degree of K2-1-2U+K2-1-2L was the highest, followed by K2-2 and K2-3.

[0082] Step 3:

[0083] Based on the aforementioned study of the remaining oil distribution in the K2 reservoir, the remaining oil in the well-controlled area of ​​the K2 layer is mainly distributed in K2-1-1, K2-2, and K2-4. Among them, the K2-2 layer has the most abundant remaining recoverable reserves and has great potential for development. Currently, the production well trajectories of the K2 layer are mainly concentrated near the high permeability layer. The production performance of a few production wells with horizontal sections located in the middle and lower part of the K2-2 layer is significantly better than that of production wells with horizontal sections located near or above the high permeability layer.

[0084] The results of the dynamic model fitting of the entire reservoir show that the high permeability layer has a production rate of more than 30%, with an average oil saturation of 0.45, followed by K2-3, K2-1-2U and the upper part of K2-2. The remaining oil is concentrated in K2-2, K2-1-1 and K2-4 vertically, and mainly concentrated in the area near the oil wells horizontally. The water injection wells are highly flooded.

[0085] Figure 8The figure shows that there are significant differences in the water cut rising patterns of different well trajectories in the embodiment of the present invention. In the left figure, Well1 is the trajectory of the side-drilled horizontal well in the embodiment of the present invention, and Well2 is the trajectory of the horizontal well of the conventional old well in the oil reservoir. In the right figure, the ordinate represents the water cut (water cut, %), and the ordinate represents the cumulative oil production (Cum.Oil, * 10MB). From the growth relationship between the cumulative oil production and the water cut, it can be seen that the cumulative oil production of the side-drilled horizontal well in the embodiment of the present invention will have a higher water cut only when it reaches 140*10MB. The water cut in the embodiment of the present invention is 70%, while the water cut of the conventional old well in the oil reservoir has reached about 70% when the cumulative oil production reaches about 60*10MB. There is a significant difference in the water cut rising pattern of the oil production of the side-drilled horizontal well of the present invention and that of the conventional horizontal well.

[0086] Step 4:

[0087] A study of the production history of wells with different trajectories revealed that well trajectory significantly affects water content and cumulative oil production. Wells located in the lower and middle portions of K2 have better production rates than those closer to the high-permeability zone. Based on previous research, the remaining oil is concentrated in K1-1, K2, and K4. K2 possesses the richest remaining reserves and the best physical properties among the undeveloped areas.

[0088] Figure 9 A schematic diagram of a water cut rising curve of sidetrack wells at different layers with the same fluid production is shown in the embodiment of the present invention. Figure 9 In the figure, the horizontal axis represents time after sidetracking, and the vertical axis represents water cut (%). Comparing the water cut under the same liquid rate in the no-zone, K1-1, K2, and K4 zones, numerical simulation results show that the K2 sidetrack well has better water control and higher liquid production capacity. More importantly, compared with the K1-1 sidetrack well, the K2 sidetrack well can better utilize the larger reserves.

[0089] Step 5:

[0090] According to the distribution law of remaining oil and the production research of the horizontal section of the existing horizontal well trajectory, the target layer of the sidetracking well trajectory of the horizontal well in the reservoir development is determined, and the sidetracking horizontal well trajectory is optimized. Figure 10 FIG. 1 shows a schematic diagram of the optimized sidetracking trajectory in an embodiment of the present invention. Figure 10 In the middle, a seepage barrier is created in the high permeability layer around the horizontal section of the high permeability layer and the main wellbore of the original well trajectory is plugged with cement. The new side drilling wellbore is plugged and the new horizontal well trajectory is set in the low permeability layer to continue operation;

[0091] To mitigate the adverse effects of crossflow from high-permeability zones after sidetracking on waterflooding development in new wellbores, large-scale injection of plugging agents is required before sidetracking to create a seepage barrier within the high-permeability zones surrounding the existing wellbore. The plugging agent dosage was calculated by substituting different high-permeability zone plugging radii (10 to 50 meters) into Equation 1. The plugging agent dosage was used to calculate the plugging cost for different plugging radii, and a numerical simulation model was used to predict the oil production increase effect for each high-permeability zone plugging radius. Figure 11 FIG. 1 is a schematic diagram showing the optimal blocking distance calculation result according to an embodiment of the present invention. Figure 11 In the figure, the horizontal axis represents the incremental oil cost per barrel of oil in the interval, the vertical axis represents the plugging distance of the high permeability layer, and the horizontal line in the figure represents the incremental oil cost limit. According to the actual incremental oil cost limit of the oil field, the optimal plugging radius of the drilling on this side is determined to be 30 meters, and the plugging agent injection requirements under the corresponding conditions are also compiled into the drilling engineering plan.

[0092] Table 1 Calculation of plugging distance, oil increase volume and oil increase cost

[0093]

[0094] In an embodiment of the present invention, a horizontal well design system for sidetracking old wells in highly heterogeneous oil reservoirs is also provided. The system includes a first determination unit, a regularity characterization unit, a type determination unit, and an optimization unit.

[0095] The first determining unit is used to identify a high permeability layer section in the reservoir and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer;

[0096] Regularity characterization unit, used for studying reservoir water flooding patterns and characterizing the remaining oil distribution pattern based on the reservoir water flooding patterns;

[0097] A type determination unit, configured to determine the type of a horizontal well trajectory for reservoir development based on production dynamic data in combination with a relative positional relationship between the well trajectory and the high permeability layer;

[0098] The optimization unit is used to determine the side-drilling target layer of the horizontal well trajectory of the oil reservoir development according to the remaining oil distribution law and the production research of the horizontal section of the existing horizontal well trajectory, and to optimize the side-drilling horizontal well trajectory.

[0099] Specifically, the optimization unit includes a barrier module and a blocking module.

[0100] The barrier module is used to create a seepage barrier in the high-permeability layer around the existing wellbore and seal the original well trajectory;

[0101] The plugging module is used to determine the relationship between the amount of plugging agent and the expected economic benefits according to the plugging radius of different high-permeability layers, and to determine the amount of plugging agent for the high-permeability layer according to the economic evaluation results to plug the side-drilled high-permeability layer.

[0102] Specifically, the amount of the high permeability layer plugging agent is determined by the high permeability layer plugging radius, redundancy coefficient, average thickness of the high permeability layer, length of the horizontal section and the ratio of the high permeability layer crossflow liquid volume to the total liquid volume.

[0103] Specifically, the first determination unit includes a first determination module, an identification method determination module and a position determination module.

[0104] The first determination module is used to determine the distribution and characteristics of the high permeability layer based on geological data;

[0105] An identification method determination module is used to determine a method for identifying a high permeability layer in a target reservoir based on the distribution and characteristics of the high permeability layer, the well logging curve of the coring well, and the high permeability layer identification results of the core thin section and porosity test of the corresponding core;

[0106] The position determination module is used to identify the high permeability layer section according to the high permeability layer identification method and the horizontal well inclination data and logging curve data, and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer.

[0107] Specifically, the regularity characterization unit includes a pattern determination module, a second determination module and a regularity characterization module.

[0108] Pattern determination module, used to study reservoir water flooding patterns based on transit well logging data and production logging data;

[0109] The second determination module is used to analyze the flow pattern of injected water in the reservoir and the differences in water-flooded intervals according to the reservoir water-flooding pattern;

[0110] The law characterization module is used to characterize the remaining oil distribution law according to the flow law and the difference of the water-flooded layer sections.

[0111] The method and system for designing horizontal wells for sidetracking old wells in highly heterogeneous oil reservoirs of the present invention optimize the horizontal well sidetracking trajectory and construction plan, maximizing the development effect of sidetracking new wellbores. At the same time, the present invention combines the sidetracking technology of old wells with the water plugging technology to optimize the design of the sidetracking plan, which can greatly improve the production increase effect of the measures compared with ordinary sidetracking.

[0112] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs, characterized in that: The method comprises: Identify the high permeability layer in the reservoir and determine the relative position relationship between the horizontal well trajectory of the existing horizontal well and the high permeability layer; Study on reservoir flooding pattern and characterize the distribution law of remaining oil based on the study on reservoir flooding pattern; Determining the type of horizontal well trajectory for reservoir development based on production performance data and the relative position relationship between the well trajectory and the high permeability layer; According to the distribution law of remaining oil and the production research of the horizontal section of existing horizontal well trajectories, the target layer of the sidetracking well trajectory of the horizontal well in oil reservoir development is determined, and the well trajectory of the sidetracking horizontal well is optimized.

2. The method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs according to claim 1, characterized in that: Optimizing the well trajectory of a sidetracked horizontal well includes: Create a seepage barrier within the hyperpermeable layer surrounding the existing wellbore and seal off the original well trajectory; and, Determine the relationship between plugging agent dosage and expected economic benefits based on the plugging radius of different high permeability layers. The dosage of plugging agent for high permeability layer is determined based on the economic evaluation results, and the high permeability layer of side drilling is plugged.

3. The method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs according to claim 2, characterized in that: The dosage of the high permeability layer plugging agent is determined by the high permeability layer plugging radius, redundancy coefficient, average thickness of the high permeability layer, length of the horizontal section and the ratio of the high permeability layer crossflow liquid volume to the total liquid volume.

4. The method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs according to claim 2 or 3, characterized in that: The dosage formula of the high permeability layer plugging agent is expressed as: Among them, V represents the amount of plugging agent, a represents the redundancy coefficient, represents porosity, H represents the average thickness of the high permeability layer, L represents the length of the horizontal section, r represents the plugging radius, and f represents the ratio of the crossflow liquid volume in the high permeability layer to the total liquid volume.

5. The method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs according to claim 1 or 2, characterized in that: Identifying a high permeability layer in a reservoir and determining the relative position relationship between the horizontal well trajectory of an existing horizontal well and the high permeability layer includes: Determine the distribution and characteristics of high permeability layers based on geological data; According to the distribution and characteristics of high permeability layers, the well logging curves of the coring wells, the core thin sections of the corresponding cores, and the high permeability layer identification results of the porosity test, the method of identifying high permeability layers in the target reservoir based on the well logging curves is determined; According to the high permeability layer identification method, the high permeability layer section is identified based on the horizontal well inclination data and the well logging curve data, and the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer is determined.

6. The method for designing sidetracking horizontal wells in old wells of highly heterogeneous oil reservoirs according to claim 1, characterized in that: The research on reservoir flooding mode and the characterization of the remaining oil distribution law based on the research on reservoir flooding mode include: Study the reservoir water flooding pattern based on the transit well logging data and production logging data; Analyze the flow pattern of injected water in the reservoir and the differences in water-flooded intervals according to the reservoir water-flooding pattern; The remaining oil distribution law is characterized according to the flow law and the difference in water-flooded intervals.

7. A horizontal well design system for sidetracking old wells in highly heterogeneous reservoirs, characterized by: The system includes a first determination unit, a regularity characterization unit, a type determination unit and an optimization unit. The first determining unit is used to identify a high permeability layer section in the reservoir and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer; Regularity characterization unit, used for studying reservoir water flooding patterns and characterizing the remaining oil distribution pattern based on the reservoir water flooding patterns; A type determination unit, configured to determine the type of a horizontal well trajectory for reservoir development based on production dynamic data in combination with a relative positional relationship between the well trajectory and the high permeability layer; The optimization unit is used to determine the side-drilling target layer of the horizontal well trajectory of the oil reservoir development according to the remaining oil distribution law and the production research of the horizontal section of the existing horizontal well trajectory, and to optimize the side-drilling horizontal well trajectory.

8. The horizontal well design system for sidetracking in old wells in highly heterogeneous oil reservoirs according to claim 7, characterized in that: The optimization unit includes a barrier module and a blocking module. The barrier module is used to create a seepage barrier in the high-permeability layer around the existing wellbore and seal the original well trajectory; The plugging module is used to determine the relationship between the amount of plugging agent and the expected economic benefits according to the plugging radius of different high-permeability layers, and to determine the amount of plugging agent for the high-permeability layer according to the economic evaluation results to plug the side-drilled high-permeability layer.

9. The horizontal well design system for sidetracking in old wells in highly heterogeneous oil reservoirs according to claim 8, characterized in that: The dosage of the high permeability layer plugging agent is determined by the high permeability layer plugging radius, redundancy coefficient, average thickness of the high permeability layer, length of the horizontal section and the ratio of the high permeability layer crossflow liquid volume to the total liquid volume.

10. The horizontal well design system for sidetracking in old wells in highly heterogeneous reservoirs according to claim 8 or 9, characterized in that: The dosage formula of the high permeability layer plugging agent is expressed as: Among them, V represents the amount of plugging agent, a represents the redundancy coefficient, represents porosity, H represents the average thickness of the high permeability layer, L represents the length of the horizontal section, r represents the plugging radius, and f represents the ratio of the crossflow liquid volume in the high permeability layer to the total liquid volume.

11. The horizontal well design system for sidetracking in old wells in highly heterogeneous reservoirs according to claim 7 or 8, characterized in that: The first determination unit includes a first determination module, an identification method determination module and a position determination module. The first determination module is used to determine the distribution and characteristics of the high permeability layer based on geological data; An identification method determination module is used to determine a method for identifying a high permeability layer in a target reservoir based on the distribution and characteristics of the high permeability layer, the well logging curve of the coring well, and the high permeability layer identification results of the core thin section and porosity test of the corresponding core; The position determination module is used to identify the high permeability layer section according to the high permeability layer identification method and the horizontal well inclination data and logging curve data, and determine the relative position relationship between the horizontal section well trajectory of the existing horizontal well and the high permeability layer.

12. The horizontal well design system for sidetracking in old wells in highly heterogeneous oil reservoirs according to claim 7, characterized in that: The regularity characterization unit includes a pattern determination module, a second determination module and a regularity characterization module. Pattern determination module, used to study reservoir waterlogging patterns based on transit well logging data and production logging data; The second determination module is used to analyze the flow pattern of injected water in the reservoir and the differences in water-flooded intervals according to the reservoir water-flooding pattern; The law characterization module is used to characterize the remaining oil distribution law according to the flow law and the difference of the water-flooded layer sections.

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