Method for identifying a preferential flow path

Abstract

The present application relates to a kind of identification method of dominant percolation channel, belong to oilfield development technical field.The present application first describes the basic geological characteristics of reservoir according to the geological element influencing dominant percolation channel;According to the historical well pattern adjustment data, determine injection-production well pattern, different well group injection-production effect direction parameter value obtained from historical production situation;Then, according to the reservoir engineering method, determine the water passing multiple and permeability in injection-production effect direction;Comprehensive production dynamic monitoring data further analyzes the water passing multiple in different injection-production direction, and determines the lower limit value of physical property and water passing multiple in different level dominant percolation channel;Finally, delineate different level dominant percolation channel, realize the identification of dominant percolation channel.The present application integrates dynamic and static data, overcomes the traditional dynamic monitoring data-based dominant channel identification, improves the precision of dominant percolation channel prediction.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for identifying a dominant seepage channel, and belongs to the technical field of oilfield development. BACKGROUND

[0002] Water injection development method is widely used in various oilfields as an important enhanced oil recovery method. In the long-term water injection development process, the injection water soaking and scouring effect causes different degrees of modification of the reservoir, and the micro properties of the reservoir change due to physical and chemical effects, resulting in changes in reservoir parameters. The driving force and scouring force of the injection water cause erosion and denudation of the reservoir rock mineral particles and intergranular cement, making the pore throat smooth or the throat space enlarged, increasing the coordination number of the pore throat, and forming a "dominant seepage channel" in the throat with a larger high-permeability reservoir area, which affects the further development of the oilfield. It is imperative to determine the direction of the dominant seepage channel. The conventional method for identifying the dominant seepage channel of the oil reservoir mainly relies on single well point dynamic monitoring data and dynamic analysis, which has many subjective factors, high cost, and few well points, and it is difficult to fully promote and improve the development effect of injection-production structure adjustment. SUMMARY

[0003] The purpose of the present application is to provide a method for identifying a dominant seepage channel to solve the problem of low identification accuracy caused by dynamic analysis in the development process of water injection reservoirs.

[0004] The present application provides a method for identifying a dominant seepage channel, which comprises the following steps:

[0005] 1) Obtain the geological elements affecting the dominant seepage channel in the area to be identified;

[0006] 2) Determine the injection-production well pattern according to the historical well pattern adjustment data, and determine the water production of the oil well in the injection-production well pattern;

[0007] 3) Determine the water passing multiple and the average permeability between the injection and production wells in the injection-production effect direction;

[0008] 4) Interactively analyze the obtained water passing multiple and average permeability to determine the dominant channel division standard;

[0009] 5) Use the obtained dominant channel division standard to semi-quantitatively identify the dominant seepage channel of the target area.

[0010] The application determines injection-production well pattern in combination with dynamic and static data of production well, and then obtains parameter values in different injection-production corresponding directions of different well groups in combination with historical production conditions; water breakthrough multiple and permeability in injection-production effective direction are determined through reservoir engineering method, injection-production effectiveness in different injection-production directions is further analyzed by comprehensively analyzing production dynamic monitoring data, lower limit values of reservoir physical property and water breakthrough multiple in injection-production effectiveness relationship are determined by using statistical method, finally, dominant seepage channel is identified on plane, different type dominant channel distribution area is circled, and basis for well pattern comprehensive adjustment + fluid flow diversion of water drive reservoir is provided. The application identifies dominant seepage channel into fine description under dynamic monitoring constraint, overcomes the traditional identification of dominant channel mainly based on dynamic monitoring data, and improves the prediction accuracy of dominant seepage channel.

[0011] Further, in order to accurately determine the water production of the oil well in the injection-production well pattern, the implementation process of the step 2) is as follows:

[0012] a. Statistics of injection wells and production wells are performed to determine the injection-production well pattern;

[0013] b. It is determined that the production well in the historical injection-production well pattern is a single-way corresponding well number or a multi-way corresponding well number;

[0014] c. The yield splitting coefficient in the injection-production corresponding direction is determined by using the oil well permeability, the water well permeability and the oil-water well spacing;

[0015] d. The water production of the oil well in the injection-production well pattern is determined according to the yield splitting coefficient.

[0016] Further, the calculation formula of the yield splitting coefficient γ is as follows:

[0017] γ=(K1+K2) / 2L2

[0018] Wherein, K1 is the oil well permeability in the injection-production well pattern, K2 is the water well permeability, and L1 is the oil-water well spacing.

[0019] Further, in order to accurately determine the water breakthrough multiple, the determination process of the water breakthrough multiple in the step 3) is as follows:

[0020] A. The perforation thickness of the oil-water well in the injection-production well pattern is counted to determine the average thickness in different injection-production directions;

[0021] B. The recovery efficiency and the single reservoir coefficient of the to-be-identified area are counted, the sweep area in different injection-production directions is determined according to the obtained average thickness and the parameters obtained in the step 2);

[0022] C. The water breakthrough multiple in different injection-production directions is determined according to the sweep area.

[0023] Further, the calculation formula of the sweep area S1 in the step B is as follows:

[0024]

[0025] wherein E R is recovery efficiency, β is single storage coefficient, Q1 is water production of oil well in injection-production well pattern, is average thickness in different injection-production directions.

[0026] Further, the geological elements include reservoir structure, sedimentary microfacies, porosity, permeability, heterogeneity and oil-bearing area. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flow chart of the method for identifying the dominant seepage channel of the present application;

[0028] Figure 2 is a scatter plot of the A fault block permeability and tracer concentration in an embodiment of the present application;

[0029] Figure 3 is a scatter plot of the A fault block physical property and water passing multiple in an embodiment of the present application;

[0030] Figure 4 is a planar distribution map of the A fault block dominant channel in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application will be further described in conjunction with the accompanying drawings.

[0032] The dominant seepage channel refers to a low-resistance seepage channel locally formed in the reservoir due to geological and development factors, and after water injection development, the injected water forms obvious dominant flow along this channel to produce a large amount of invalid circulation of injected water. The formation of the dominant seepage channel of the reservoir plays an important role in the distribution and migration of fluid, and affects the formation and distribution of remaining oil. In the process of water injection development, the injected water mainly migrates along the dominant seepage channel, and the injected water has a high swept degree; the non-dominant seepage channel such as the river channel side edge with small relative thickness, low permeability and slow pressure transmission speed has a low swept degree of injected water, and the remaining oil saturation is relatively high.

[0033] Therefore, the present application provides a method for identifying the dominant seepage channel, which firstly describes the basic geological characteristics of the reservoir according to the geological elements affecting the dominant seepage channel; determines the injection-production well pattern according to the historical well pattern adjustment data, and obtains the parameter value of the injection-production effect direction of different well groups according to the historical production situation; then determines the water passing multiple and permeability in the injection-production effect direction according to the reservoir engineering method; further analyzes the water passing multiple in different injection-production directions according to the production dynamic monitoring data, and determines the lower limit value of the physical property and water passing multiple in the dominant seepage channel of different levels; finally circulates the dominant seepage channel of different levels to realize the identification of the dominant seepage channel. The implementation process of the method is as shown in Figure 1As shown, the following takes the A fault block as an example to describe the implementation process of the present application in detail.

[0034] 1. Determine the geological features of the region to be identified.

[0035] The present application describes the basic geological features of the reservoir according to the geological elements affecting the dominant seepage channel, wherein the reservoir geological elements include structure, perforation thickness, porosity, permeability, and oil-bearing area, providing basic data for later production splitting.

[0036] The structure and oil-bearing area in this step are based on the drawing of the sublayer plan, which determines the range of the study area.

[0037] β = φ * S o * γ / B o

[0038] In the formula, φ is the porosity of the oil layer, S o is the original oil saturation of the oil layer, γ is the density of crude oil, and B o is the volume coefficient.

[0039] 2. Determine the injection-production well pattern according to the historical well pattern adjustment data, and determine the parameters of the corresponding direction on different injection-production well patterns.

[0040] The parameters of the corresponding direction on the injection-production well pattern determined in this step refer to the water production, which is obtained through the historical production situation, and the specific implementation process is as follows:

[0041] a). Statistics of injection wells and production wells to determine the historical injection-production well pattern;

[0042] b). Determine whether the production wells in the historical injection-production well pattern are single-way corresponding well numbers or multi-way corresponding well numbers;

[0043] c). Statistics of the permeability K1 of the oil well, the permeability K2 of the water well, and the well spacing L1 of the oil and water well in the injection-production well pattern to determine the production splitting coefficient γ in the injection-production corresponding direction, such as single-way corresponding oil and water wells, and the splitting coefficient γ is 1;

[0044] γ = (K1 + K2) / 2L2

[0045] d) Determine the water production Q1 of the oil well in the historical injection-production well pattern;

[0046] Q1 = Q * γ

[0047] 3. Determine the water passing multiple and the average permeability between the oil and water wells in the injection-production effective direction.

[0048] According to the oil reservoir engineering method, the water passing multiple and the average permeability between the oil and water wells in the injection-production effective direction are determined, and the injection-production effect in different directions is further analyzed by comprehensively analyzing the production dynamic monitoring data:

[0049] a). Statistics of the perforation thickness H of the oil and water wells in the injection-production well pattern, to determine the average thickness in different injection-production directions

[0050] b). Statistics of the recovery efficiency E of the target layer R , and the single reservoir coefficient β, ignoring the influence of the formation water, i.e. the water production of the oil well is the injection amount of the injection well in the injection-production direction, to determine the swept area S1 in different injection-production directions;

[0051]

[0052] c) Determination of the water breakthrough multiple λ in different injection-production directions;

[0053]

[0054] d) Dynamic monitoring data mainly from polymer concentration analysis, and further determination of the influence of tracer concentration on the dominant channel by using the tracer concentration and permeability intersection graph, according to which three regions of permeability to tracer concentration are determined, providing a basis for the identification standard of the dominant channel in the later stage.

[0055] The scatter plot statistics of the permeability and tracer concentration of the A fault block obtained by the above process are shown in Figure 2 .

[0056] 4. Interactive analysis of the obtained water breakthrough multiple and the average permeability between the oil and water wells (ignoring the influence of other geological factors), to determine the division standard of the dominant channel.

[0057] According to the water breakthrough multiple and the average permeability between the oil and water wells obtained in step 3, the physical properties (permeability) and the water breakthrough multiple are interactively analyzed by using the method of probability statistics, an intersection graph is drawn, and the lower limit of the permeability and the water breakthrough multiple of the dominant flow channel is determined according to the intersection graph.

[0058] For this embodiment, the water breakthrough multiple and the permeability of the A fault block obtained in step 3 are interactively analyzed, and the obtained intersection graph is shown in Figure 3 , and the division standard and classification evaluation table of the dominant channel of the A fault block determined based on the intersection graph are shown in Table 1.

[0059] Table 1

[0060]

[0061] 5. Semi-quantitative identification of the dominant flow channel of the target area by using the obtained division standard of the dominant channel.

[0062] For this embodiment, the division standard in Table 1 is used to divide the dominant channel of the A fault block, and the planar distribution of the dominant channel of the A fault block is shown in Figure 4The application is applied to the identification of the advantage channel of A fault block. The advantage channel direction and area of the water drive reservoir are identified on the plane by using the established advantage channel identification standard. The advantage channel type is divided by comprehensively dividing multiple indexes on the plane. Different development countermeasures are proposed for different advantage seepage channels. The purpose is to improve the development effect of the reservoir.

[0063] According to the identification and evaluation results of the advantage seepage channel in the region, it is considered that the oil-bearing area of the Ⅳ1, 2 and 9 layers of the A fault block is large, the effective thickness is large, the reserve scale is large, and there is a potential for further improving the recovery rate. By using well pattern comprehensive adjustment and tertiary oil recovery technology, it is expected that 169.35×104t of geological reserves can be produced, the initial production capacity of a single well is about 3-4t, and according to the oil price of 60$ / bbl, considering drilling, fracturing, ground investment and operation cost, sales tax, crude oil commodity rate, loan interest rate and the like, it is expected that 13.1×104t of cumulative oil can be realized at the end of the fifteenth year, the recovery rate can be improved by 3.22%, and the economic benefit can be increased by 3.5 million yuan.

[0064] During 2016-2019, 6 production well sites were put into production in the A fault block, the stage oil increment was 2000t, the average initial single well production reached 3-10t / d, and the further improvement of the recovery rate of the main oil layer in the region became a reality, which had good economic benefit and popularization effect.

Claims

1. A method for identifying dominant seepage channels, characterized in that, The identification method includes the following steps: 1) Obtain geological elements that influence the dominant seepage channels in the area to be identified; 2) Determine the injection-production well network based on historical well network adjustment data, and determine the water production of oil wells in the injection-production well network. The process is as follows: a. Conduct a statistical analysis of water injection wells and oil production wells to determine the injection-production well network; b. Determine whether the oil wells in the historical injection-production well network are unidirectionally corresponding well numbers or multidirectionally corresponding well numbers; c. Determine the production splitting coefficient in the corresponding injection-production direction using oil well permeability, water well permeability, and the distance between oil and water wells. When the oil and water wells are in a unidirectional correspondence, the splitting coefficient... The production splitting coefficient is 1. The calculation formula is: ； in The permeability of oil wells within the injection-production well network. For water well permeability, This refers to the distance between oil and water wells. d. Determine the water production of oil wells within the injection-production well network based on the production splitting coefficient; 3) Determine the water permeability ratio in the injection-production direction and the average permeability between oil and water wells; 4) Perform cross-sectional analysis on the obtained water flow ratio and average permeability, draw a cross-sectional diagram, and determine the lower limit of permeability and lower limit of water flow ratio based on the cross-sectional diagram as the criteria for dividing the dominant channel; 5) The lower limits of permeability and water flow ratio of the obtained dominant channel division standard are used to semi-quantitatively identify the dominant seepage channels in the target area.

2. The method for identifying dominant seepage channels according to claim 1, characterized in that, Step 3) further includes: A. Statistically determine the perforation thickness of oil and water wells within the injection-production well network, and determine the average thickness in different injection-production directions; B. Statistically determine the recovery rate and single-reservoir coefficient of the area to be identified, and determine the swept area in different injection and production directions based on the obtained average thickness and the parameters obtained in step 2). C. Determine the water flow ratio for different injection and production directions based on the swept area.

3. The method for identifying dominant seepage channels according to claim 2, characterized in that, The method also includes using a cross-plot of tracer concentration and permeability to further determine the effect of tracer concentration on the dominant channel, and based on the cross-plot, three regions are identified where permeability affects tracer concentration.

4. The method for identifying dominant seepage channels according to claim 2, characterized in that, The affected area in step B The calculation formula is: ； in For recovery rate, For single storage coefficient, This refers to the water production of oil wells within the injection-production well network. The average thickness is given in different injection and extraction directions.

5. The method for identifying dominant seepage channels according to claim 1, characterized in that, The geological elements mentioned include reservoir structure, sedimentary microfacies, porosity, permeability, heterogeneity, and oil-bearing area.

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