A four-dimensional identification method for dominant seepage channels in thick oil layers

Abstract

The present application relates to the technical field of dominant percolation channel identification, in particular to a four-dimensional identification method for dominant percolation channel in thick oil layer. The method mainly solves the problems of large workload, difficult judgment, high cost and low efficiency of the existing methods for identifying dominant percolation channel. The four-dimensional identification method for dominant percolation channel in thick oil layer comprises the following steps: establishing a theoretical model, simulating tracer flow through the theoretical model; injecting different tracer liquids into each injection well around the target well; determining the dominant percolation channel according to the tracer fluid detection results of the target well, and determining the evolution state of the dominant percolation channel according to the identification results of the dominant percolation channel. The four-dimensional identification method for dominant percolation channel in thick oil layer can realize directional and quantitative identification of dominant percolation channel and tracking simulation of dominant percolation channel, reduce cost, improve work efficiency, provide basis for in-layer accurate dynamic analysis and adjustment, and greatly improve recovery efficiency.

Description

Technical Field

[0001] This invention relates to the field of dominant flow channel identification technology, specifically a four-dimensional identification method for dominant flow channels in thick oil layers. Background Technology

[0002] Currently, methods for identifying dominant seepage channels include well logging, inter-well dynamic monitoring, well testing, and coring data. Well logging requires coordination with other data to first determine the dominant channels and then summarize the relationships. Inter-well dynamic monitoring requires on-site testing and monitoring, which involves a large workload, high cost, and quantitative judgment. Well testing requires measuring bottom hole flowing pressure and performing field interpretation, but it is influenced by many factors, making judgment difficult and prone to multiple interpretations. Coring data requires theoretical research and comparison of data from different periods, which is labor-intensive, time-consuming, and inefficient. Summary of the Invention

[0003] To overcome the shortcomings of existing methods for identifying dominant seepage channels, such as high workload, difficulty in judgment, high cost, and low efficiency, this invention provides a four-dimensional identification method for dominant seepage channels in thick oil layers. This method can achieve directional and quantitative identification of dominant seepage channels, as well as tracking and simulation of dominant seepage channels, reducing costs, workload, and improving work efficiency. It provides a basis for precise dynamic analysis and adjustment within the layer, and can significantly improve the recovery rate.

[0004] The technical solution of this invention is: a four-dimensional identification method for dominant seepage channels in thick oil layers, comprising the following steps:

[0005] S1. Establish a theoretical model and simulate tracer flow using the theoretical model;

[0006] S2. Inject different tracer liquids into each injection well surrounding the target well;

[0007] S3. Based on the tracer fluid detection results of the target well, identify the dominant seepage channels and determine the evolution state of the dominant seepage channels based on the identification results.

[0008] Furthermore, the tracer flow simulation in step S1 includes: setting different injection concentrations and injection times of the tracer fluid, and clarifying the impact of different injection concentrations and injection times on the tracer flow simulation results.

[0009] Furthermore, in step S2, different tracer fluids are injected into each injection well to determine the initial state tracer fluid concentration and the tracer fluid injection time.

[0010] Furthermore, the tracer fluid detection results in step S3 include: tracer fluid production curve, concentration field map of each tracer fluid, and tracer fluid distribution ratio map.

[0011] Furthermore, in step S3, the connectivity between the water well and the oil well is determined based on the tracer fluid production concentration of the target well.

[0012] Furthermore, in step S3, the main direction of incoming water is determined based on the concentration field maps of each tracer fluid.

[0013] Furthermore, in step S3, the dominant seepage channels are identified by analyzing the proportion of incoming water based on the tracer fluid distribution ratio diagram.

[0014] Furthermore, step S3 also includes describing the different seepage characteristics and development status exhibited by the dominant seepage channels at each stage.

[0015] Furthermore, step S3 also includes determining the development degree of dominant seepage channels based on tracer fluid distribution maps at different times, and describing the size and direction of dominant seepage channels, changes in oil saturation and water content between wells, sand bodies, and physical property parameters.

[0016] The present invention has the following beneficial effects: By adopting the above-mentioned scheme, the present invention employs a dominant seepage channel identification technology based on tracer flow simulation. Through precise monitoring using tracer flow simulation, dominant seepage channels can be quantitatively identified, and a deeper understanding of the development degree and impact of dominant seepage channels over time can be obtained. This allows for a more in-depth understanding of the role and influence of dominant seepage channels in oil reservoirs, effectively guiding dynamic analysis and adjustment, as well as tapping remaining oil potential, providing strong support for the rational development of oilfields. Simultaneously, this method saves significant costs associated with tracers, eliminating the need for on-site tracer injection for monitoring, reducing workload, and improving work efficiency. Based on the judgment results of tracer flow simulation, water can be shut off in ineffective reservoirs, and injection can be stopped or controlled in reservoirs with high flow rates, providing strong support for optimizing water injection schemes. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention;

[0018] Figure 2 This is a tracer fluid flow rate diagram of well L10-282 in layer 2+31 of Sa II in this invention;

[0019] Figure 3 This is a partition diagram of the tracer fluid flow rate of well L11-283 in layer 2+31 of Sa II in this invention, showing its distribution across surrounding oil wells.

[0020] Figure 4 This is a tracer fluid distribution map from L10-283 in January 1980, as described in this invention.

[0021] Figure 5 This is a tracer fluid distribution map from L11-283 in January 1980, as described in this invention.

[0022] Figure 6 This is a diagram showing the distribution ratio of the tracer fluid in 1980 in this invention;

[0023] Figure 7 This is the tracer fluid distribution map from 1976 used in this invention;

[0024] Figure 8 This is the tracer fluid distribution map from 1978 used in this invention;

[0025] Figure 9 This is the tracer fluid distribution map from 1980 used in this invention;

[0026] Figure 10 This is the tracer fluid distribution map from 1982 used in this invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Depend on Figure 1 As shown, a four-dimensional identification method for dominant seepage channels in thick oil layers mainly includes the following steps:

[0029] S1. Establish a theoretical model and use the theoretical model to simulate tracer flow.

[0030] To minimize the impact on the fluid while ensuring simulation accuracy, different injection concentrations and injection times must be considered when constructing the theoretical model. Low, medium, and high concentrations were selected to obtain the specific impact of concentration changes on the tracer flow simulation results. Short, medium, and long injection times were also set to observe how time variations affect the distribution and flow trajectory of the tracer fluid.

[0031] During the simulation, parameters such as flow rate, velocity, and direction of the tracer fluid under different injection concentrations and injection times were recorded and analyzed in detail. By comparing and analyzing the simulation results, the specific parameter setting methods for tracer flow simulation technology can be clarified, providing strong theoretical support for tracer flow simulation in practical applications.

[0032] S2. Based on the results of the tracer flow simulation in step S1, inject different tracer fluids into each injection well surrounding the target well. When injecting the tracer fluid, use tracer flow simulation technology to define a unique tracer fluid identifier for each injection well, define the initial state tracer fluid concentration and tracer fluid injection time, and perform tracer flow simulation.

[0033] S3. Based on the tracer fluid detection results of the target well, identify the dominant seepage channels and determine the evolution state of the dominant seepage channels based on the identification results.

[0034] The tracer fluid detection results include: tracer fluid production curve, tracer fluid concentration field map, and tracer fluid distribution scale map. Based on the tracer fluid production curve, such as... Figure 2 and Figure 3 By analyzing the production concentration of tracer fluids in the target well, the connectivity between the water well and the target oil well can be determined. Based on the concentration field maps of each tracer fluid, such as... Figure 4 and Figure 5 By comparing the tracer fluid distribution, the main direction of water inflow can be determined. Based on the tracer fluid distribution scale map, such as... Figure 6 By analyzing the proportion of incoming water volume to identify dominant seepage channels, the number of dominant seepage channels, their formation time, the corresponding contribution rate of water wells, and the location changes of dominant seepage channels over time can be obtained. Furthermore, inefficient and ineffective injection well layers can be identified, and dominant seepage channels can be quantitatively analyzed, enabling the directional and quantitative identification of dominant seepage channels.

[0035] Simultaneously, considering the time dimension, the evolution state of dominant seepage channels is determined based on the identification results. This process involves multiple stages, each exhibiting different seepage characteristics and development states. The development degree of dominant seepage channels is judged based on tracer fluid distribution maps at different times, and the scale and direction of dominant seepage channels, changes in inter-well oil saturation and water cut, sand bodies, and physical property parameters are described. This not only quantifies dominant seepage channels but also identifies their location and development degree in four-dimensional space.

[0036] This invention innovates a dominant seepage channel identification technology based on tracer flow simulation. Through precise monitoring using tracer flow simulation, dominant seepage channels can be quantitatively identified, and their development and impact over time can be understood more deeply. This allows for a deeper understanding of the role and influence of dominant seepage channels in oil reservoirs, effectively guiding dynamic analysis and adjustments, as well as tapping remaining oil potential, thus providing strong support for the rational development of oilfields. Simultaneously, this method saves significant costs associated with tracers, eliminating the need for on-site tracer injection and monitoring, thereby improving work efficiency. Based on the results of tracer flow simulation, water can be shut off in ineffective reservoirs, and injection can be stopped or controlled in reservoirs with high flow rates, providing strong support for optimizing water injection schemes.

[0037] The present invention will be further described in detail below through embodiments, but it should be noted that the present invention is not limited to these embodiments.

[0038] Example 1:

[0039] The method of using the L10-282 well group of layer 2+31 of Sa II is used as an example to illustrate the application of the present invention.

[0040] The target well is L10-282. A unique tracer fluid is injected into each water well surrounding L10-282. The tracer fluid migrates towards the oil wells along with the injected water. After a period of time, the tracer fluid can be detected in the oil wells connected to it. Figure 2 This is a flow rate diagram of the tracer fluid produced from well L10-282. Due to formation heterogeneity and varying connectivity between oil and water wells, the tracer fluid reaches the oil wells at different rates, meaning the time it takes for the oil wells to encounter the tracer fluid is inconsistent. Figure 2 The tracer fluid production curves show that two tracer fluids can be detected in the oil wells. These two tracer fluids originate from wells L11-283 and L10-283, respectively, indicating that these two water wells in the well group are connected to oil well L10-282. Furthermore, the graph also shows that the concentration of the tracer fluid from L11-283 is significantly higher than the other tracer fluid, indicating that the connectivity between water well L11-283 and oil well L10-282 is better, followed by L10-283.

[0041] Figure 3 This is a split diagram of the tracer fluid flow rate of well L11-283 in the surrounding oil wells. As can be seen from the diagram, the tracer fluid from well L11-283 mainly flows to well L10-282, indicating that well L11-283 and oil well L10-282 have good connectivity.

[0042] Figure 4 This is a tracer fluid distribution map of well L10-283 from January 1980. Figure 5 This is a concentration field map of the tracer fluid from well L11-283 in January 1980. By comparing the two maps, it can be seen that the tracer fluid from L11-283 has a high concentration around the oil well. Therefore, for oil well L10-282, the main water inflow direction of this well group is well L11-283.

[0043] Figure 6This is a tracer fluid distribution map from January 1980. It shows that the water inflow from the L10-283 direction accounted for 14.02%, and the water inflow from the L11-283 direction accounted for 85.98%. Therefore, it can be inferred that the main water inflow direction was from well L11-283, forming a dominant seepage channel. Meanwhile, after water shut-off measures were implemented in well L10-282 in 1989, the water cut decreased by 2.3 percentage points. These measures validate that the tracer flow simulation method is accurate and feasible for identifying dominant seepage channels.

[0044] Example 2:

[0045] The following is a detailed explanation of the development of the dominant seepage channels from a time perspective:

[0046] I. Initial Stage

[0047] Figure 7 This is a tracer fluid distribution map from 1976, during a period before dominant seepage channels had formed. A key characteristic is the absence of tracer fluid at the production end. At this time, the fluid distribution within the reservoir was relatively uniform. As water injection progressed, water began to migrate along the high-permeability zones of the reservoir, but these channels were not yet fully developed and had limited impact on fluid flow. Inter-well oil saturation varied between approximately 72% and 71%, with a single well water cut of 0%.

[0048] II. Mid-term stage

[0049] Figure 8 , Figure 9 These are tracer fluid distribution maps from 1978 and 1980, depicting the formation and development of dominant flow channels, characterized by the initial discovery of tracer fluids at the produced end. With prolonged water injection, dominant flow channels gradually enter their development phase. During this stage, due to long-term scouring and erosion by water flow, the high-permeability zone in the reservoir continuously widens and deepens, forming more pronounced dominant flow channels. These channels gradually connect within the reservoir, becoming the main pathways for fluid flow. At this point, the fluid distribution within the reservoir begins to become uneven, with a significantly increased fluid flow velocity within the dominant flow channels, while fluid flow in other areas is inhibited. The sedimentary facies types at the location of the dominant flow channels are channel and main body, with an effective thickness of 0.8-1.01 m³, porosity of 26.41%-28.71%, and permeability of 279.6-525.7 mD. At this point, the length of the dominant seepage channel is approximately 300m (about twice the well spacing of this well network), and the width is approximately 150m (about once the well spacing of this well network), forming along the main flow direction. The oil saturation between wells varies from approximately 71% to 36.56%, and the water cut of a single well varies from approximately 0% to 66.90%.

[0050] III. Later Stage

[0051] Figure 10This is a tracer fluid distribution map from 1982, depicting a period of intensified development of dominant seepage channels, characterized by a stable and unchanging tracer fluid flow rate at the production end. In the later stages of water injection development, dominant seepage channels have fully developed and stabilized, playing a dominant role in fluid flow. Due to the long-term scouring of large amounts of injected water and the flow of oil phases, the cementation between reservoir rock particles is continuously weakened, and some reservoirs even experience sand production. At this time, the length of the dominant seepage channels is approximately 370m (approximately 2.5 times the well spacing of this well network), and the width is approximately 180m (approximately 1 well spacing of this well network), with their size remaining essentially unchanged. These changes further intensify the development of dominant seepage channels, making it easier for injected water to form ineffective circulation along these channels, leading to a decrease in oil production rate. Inter-well oil saturation varies by approximately 36.56%-36.41%, and single-well water cut varies by approximately 66.90%-73.02%.

[0052] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for four-dimensional identification of dominant seepage channels in thick oil layers, characterized in that... Includes the following steps: S1. Establish a theoretical model and simulate tracer flow using the theoretical model; S2. Inject different tracer liquids into each injection well surrounding the target well; S3. Based on the tracer fluid detection results of the target well, identify the dominant seepage channels and determine the evolution state of the dominant seepage channels based on the identification results.

2. The four-dimensional identification method for dominant seepage channels in thick oil layers according to claim 1, characterized in that: The tracer flow simulation in step S1 includes: setting different injection concentrations and injection times of the tracer fluid, and clarifying the impact of different injection concentrations and injection times on the tracer flow simulation results.

3. The four-dimensional identification method for dominant seepage channels in thick oil layers according to claim 1, characterized in that: In step S2, different tracer fluids are injected into each injection well to determine the initial tracer fluid concentration and the tracer fluid injection time.

4. The four-dimensional identification method for dominant flow channels in thick oil layers according to claim 1, characterized in that: The tracer fluid detection results in step S3 include: tracer fluid production curve, concentration field map of each tracer fluid, and tracer fluid distribution ratio map.

5. The four-dimensional identification method for dominant seepage channels in thick oil layers according to claim 4, characterized in that: In step S3, the connectivity between the water well and the oil well is determined based on the tracer fluid production concentration of the target well.

6. The four-dimensional identification method for dominant seepage channels in thick oil layers according to claim 4, characterized in that: In step S3, the main direction of incoming water is determined based on the concentration field diagrams of each tracer fluid.

7. The four-dimensional identification method for dominant seepage channels in thick oil layers according to claim 4, characterized in that: In step S3, the dominant seepage channels are identified by analyzing the proportion of incoming water based on the tracer fluid distribution ratio diagram.

8. The four-dimensional identification method for dominant flow channels in thick oil reservoirs according to any one of claims 4-7, characterized in that: Step S3 further includes describing the different seepage characteristics and development status of the dominant seepage channels at each stage.

9. The four-dimensional identification method for dominant flow channels in thick oil layers according to claim 8, characterized in that: Step S3 further includes determining the development degree of dominant seepage channels based on tracer fluid distribution maps at different times, and describing the size and direction of dominant seepage channels, changes in oil saturation and water content between wells, sand bodies, and physical property parameters.

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