A method, apparatus and related equipment for determining a free water interface

Abstract

The present invention discloses a method, apparatus and related equipment for determining the free water interface. The method may include: determining characteristic points in the logging curve based on the logging curve and rock physical properties; tracking the characteristic points in the inter-well formation based on the characteristic points to determine a data set of a series of characteristic points; performing logging curve slicing on the characteristic points in the data set to extract the rock physical property characteristic values in the logging curve of the characteristic points; determining whether the characteristic points are located in the pure water layer to determine whether the resistivity can be approximately processed; if so, regressing the linear relationship between the resistivity and the vertical depth of elevation to determine the free water interface depth; otherwise, regressing the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the vertical depth of elevation and the free water interface depth to determine the free water interface depth. This method is accurate and reliable, and can be proven to be fully applicable to the initial evaluation stage of oil reservoirs through subsequent verification.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas development, and particularly relates to a method, device and related equipment for determining a free water interface. Background Art

[0002] The free water level interface (FWL) is the depth corresponding to the interface where the capillary force between oil and water in the reservoir is zero. The traditional view is that this interface is static and horizontal. The free water level interface is one of the key parameters for reservoir evaluation, accurate reserve calculation and geological modeling in oil and gas exploration and development, and is also an important parameter for reservoir numerical simulation in the process of oil and gas field development. Its accuracy has important research significance for the efficient and reasonable development of oilfields, reducing development risks and improving the economic benefits of oilfield development, especially in the development of overseas oil and gas fields. At present, there are various methods for determining the free water interface, including the drilling method, the hydrostatic method, the logging and core analysis method, the relative permeability curve and the capillary pressure method, etc. Summary of the Invention

[0003] The inventors found that the above methods can only be accurately measured after the engineering implementation. Considering the construction cost, it cannot be effectively carried out in the initial evaluation stage of the reservoir. Therefore, how to determine the free water interface of the reservoir under the condition of lack of experimental and test data, especially in the initial evaluation stage of the reservoir, is a difficult problem that needs to be solved urgently by those skilled in the art.

[0004] In view of the above problems, the present invention is proposed to provide a method, device and related equipment for determining a free water interface that overcomes the above problems or at least partially solves the above problems.

[0005] In a first aspect, an embodiment of the present invention provides a method for determining a free water interface, which may include:

[0006] Based on the logging curve and rock physical properties, determine the characteristic points in the logging curve;

[0007] Based on the characteristic points, trace the characteristic points in the inter-well formation to determine a data set of a series of the characteristic points;

[0008] Perform logging curve slicing on the characteristic points in the data set to extract the rock physical property characteristic values in the logging curve of the characteristic points; the rock physical property characteristic values include: elevation vertical depth, resistivity, acoustic travel time and porosity;

[0009] Judge whether the characteristic points are located in the pure water layer to judge whether the resistivity can be approximately processed;

[0010] If so, regress the linear relationship between the resistivity and the elevation vertical depth to determine the free water interface depth;

[0011] Otherwise, a linear relationship between the logarithm of the regression resistivity and the logarithm of the difference between the vertical depth of elevation and the depth of the free water interface is used to determine the depth of the free water interface.

[0012] Optionally, the linear relationship between the regression resistivity and the vertical depth of elevation to determine the depth of the free water interface may include:

[0013]

[0014] d×lnR t →0, then the linear relationship formula between the resistivity and the vertical depth of elevation is:

[0015] SSTVD=c×d×lnR t +FWL+c

[0016] Wherein, Rt is the resistivity; d and c are intermediate parameters; SSTVD is the vertical depth of elevation;

[0017] The depth of the free water interface is determined according to the above formula.

[0018] Optionally, the linear relationship between the logarithm of the regression resistivity and the logarithm of the difference between the vertical depth of elevation and the depth of the free water interface to determine the depth of the free water interface includes:

[0019] Regress the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the vertical depth of elevation and the depth of the free water interface, determine the fitting curve equation of different characteristic points and the relationship between the fitting true value and the scatter value, so as to determine the depth of the free water interface.

[0020] Optionally, the determining the fitting curve equation of different characteristic points and the relationship between the fitting true value and the scatter value to determine the depth of the free water interface may include:

[0021] If the relationship value between the fitting true value and the scatter value of the fitting curve of different characteristic points is less than or equal to a preset threshold, the average value of the depth of the free water interface determined according to the fitting curves fitted by different characteristic points is determined as the depth of the free water interface;

[0022] If the relationship value between the fitting true value and the scatter value of the fitting curve of different characteristic points is greater than the preset threshold, the depth of the free water interface is determined according to the maximum value of the relationship value between the fitting true value and the scatter value.

[0023] Optionally, after extracting the logging curves of the characteristic points in the data set, it may further include:

[0024] Judging whether the characteristic points are abnormal points according to the acoustic travel time, and removing the abnormal points in the data set.

[0025] Optionally, it may further include: determining whether the feature points in the data set need to be grouped according to the distribution range of the porosity;

[0026] If so, the feature points are divided into at least two groups according to the distribution range of the porosity, and the free water interface depth corresponding to the feature points in each group is determined respectively;

[0027] Otherwise, the feature point concentration area is determined according to the distribution range of the porosity to determine the free water interface depth corresponding to the feature points in the concentration area.

[0028] In a second aspect, an embodiment of the present invention provides an application of the free water interface obtained by the method for determining the free water interface described in the first aspect.

[0029] In a third aspect, an embodiment of the present invention provides a device for determining a free water interface, which may include:

[0030] A feature point determination module, configured to determine the feature points in the logging curve based on the logging curve and rock physical properties;

[0031] A data set determination module, configured to trace the feature points in the inter-well formation based on the feature points to determine a data set of a series of the feature points;

[0032] An extraction module, configured to perform logging curve slicing on the feature points in the data set to extract the rock physical property characteristic values in the logging curve of the feature points; the rock physical property characteristic values include: elevation vertical depth, resistivity, acoustic travel time, and porosity;

[0033] A judgment module, configured to judge whether the feature points are located in the pure water layer to judge whether the resistivity can be approximately processed;

[0034] A free water interface determination module, if the judgment module judges yes, is configured to regress the linear relationship between the resistivity and the elevation vertical depth to determine the free water interface depth; otherwise, is configured to regress the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the elevation vertical depth and the free water interface depth to determine the free water interface depth.

[0035] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the method for determining the free water interface described in the first aspect.

[0036] In a fifth aspect, an embodiment of the present invention provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the method for determining the free water interface described in the first aspect.

[0037] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0038] The embodiments of the present invention provide a method, apparatus, and related equipment for determining a free water interface. The method may include: determining characteristic points in a logging curve based on the logging curve and rock physical properties; tracking the characteristic points in the inter-well formation based on the characteristic points to determine a data set of a series of characteristic points; performing logging curve slicing on the characteristic points in the data set to extract the rock physical property characteristic values in the logging curve of the characteristic points; the rock physical property characteristic values include: elevation vertical depth, resistivity, acoustic travel time, and porosity; determining whether the characteristic points are located in a pure water layer to determine whether the resistivity can be approximately processed; if so, regressing the linear relationship between the resistivity and the elevation vertical depth to determine the free water interface depth; otherwise, regressing the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the elevation vertical depth and the free water interface depth to determine the free water interface depth.

[0039] Based on the logging curve comparison slicing method of characteristic points, a relationship between the free water interface depth, elevation vertical depth, and resistivity is constructed, and then the free water interface depth is determined. This method is accurate and reliable, and through subsequent verification, it can be proved that it can be fully applied to the initial evaluation stage of oil reservoirs.

[0040] Furthermore, in the embodiments of the present invention, based on the ranging curve comparison slicing of characteristic points, a data set with the same or similar rock physical properties is used as the analysis object to analyze the change trend, distribution law, and internal relationship of parameters among the data, which is of great significance for analyzing geological phenomena and performing parameter calculations, and can also be extended to directions such as logging interpretation, data quality control, sedimentary facies analysis, and geological modeling.

[0041] Other features and advantages of the present invention will be described in the subsequent description, and some of them will be obvious from the description or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the written description and the accompanying drawings.

[0042] Next, through the accompanying drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0043] The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention. In the accompanying drawings:

[0044] Figure 1 It is a schematic flow chart of the method for determining the free water interface provided in the embodiments of the present invention;

[0045] Figure 2 Flow chart of the specific free water interface determination method provided in the embodiments of the present invention;

[0046] Figure 3 Schematic diagram of well logging curve comparison slices provided in the embodiments of the present invention;

[0047] Figure 4 Schematic diagram of the specific implementation process for removing abnormal points provided in the embodiments of the present invention;

[0048] Figure 5 Schematic diagram of division in the case of a large data distribution range provided in the embodiments of the present invention;

[0049] Figure 6 Schematic diagram of division in the case of a concentrated data distribution range provided in the embodiments of the present invention;

[0050] Figure 7 Structural diagram of the A oilfield and columnar diagram provided in the embodiments of the present invention;

[0051] Figure 8 Schematic diagram of well logging curve comparison slices of the A oilfield provided in the embodiments of the present invention;

[0052] Figure 9 is Figure 8 Schematic diagram of the acoustic time difference plane obtained after slicing the S2 feature points in (before removing abnormal points);

[0053] Figure 10 is Figure 8 Schematic diagram of the acoustic time difference plane obtained after slicing the S2 feature points in (after removing abnormal points);

[0054] Figure 11 is Figure 8 Schematic diagram of the porosity distribution frequency obtained after slicing the S2 feature points in;

[0055] Figure 12 is Figure 8 Schematic diagram of the fitting relationship between the elevation and resistivity of the S2 feature points in;

[0056] Figure 13 Structural diagram of the free water interface determination device provided in the embodiments of the present invention. Detailed implementation manners

[0057] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0058] In an embodiment of the present invention, a method for determining a free water interface is provided. This method is determined in the case of the absence of test data and experimental data, and does not involve result data obtained from a large amount of engineering data. Therefore, this method can be applied to the initial evaluation stage of an oil reservoir. Refer to Figure 1 and Figure 2 As shown, this method may include the following steps:

[0059] Step S11: Based on well logging curves and rock physical properties, determine the characteristic points in the well logging curves.

[0060] The inventor determines representative extreme points as the characteristic points of the well logging curves by analyzing the characteristics of well logging curves and lithological and physical properties of different wells. These characteristic points are representative and have certain geological significance, including the points with the best physical properties or tight points (such as the maximum flood surface or exposure surface within a sedimentary cycle), and may also include the points with the worst physical properties.

[0061] Step S12: Based on the characteristic points, trace the characteristic points in the inter-well formation to determine a data set of a series of characteristic points.

[0062] In this step, the inventor traces the inter-well formation based on the characteristic points in step S11 to obtain a data set of a series of characteristic points. All the points corresponding to the same characteristic point in this set have the same or similar rock physical properties. Refer to Figure 3 As shown, for example, the resistivity (Rt) of the characteristic point S1 is the largest and the porosity (Poro) is the lowest, and this characteristic point is located at the maximum flood surface of a sedimentary cycle; the resistivity values of the characteristic points S2 and S3 are the lowest and the porosity is the highest, and these characteristic points are located in the high-permeability layer within the interval.

[0063] It should be noted here that in the embodiment of the present invention, when tracing the inter-well formation, it is not traced along the half-amplitude points, but along the above extreme points. In other words, in the embodiment of the present invention, the extreme points (characteristic points) of the inter-well formation are traced, rather than the boundary points of the formation.

[0064] Step S13: Perform well logging curve slicing on the characteristic points in the data set to extract the rock physical property characteristic values in the well logging curves of the characteristic points; the rock physical property characteristic values include: elevation vertical depth, resistivity, acoustic travel time, and porosity.

[0065] In this step, a series of points traced by the feature points are used for well logging curve slicing, which is convenient for extracting the well logging curve and the rock physical property characteristic values therein. The well logging curve includes the original curve values and well logging interpretation results, such as natural gamma (GR), resistivity, acoustic travel time, porosity, permeability, etc. Analyzing the change trend, distribution law and internal relationship of parameters of each feature point's data set is of great significance for analyzing geological phenomena and performing parameter calculations, and this is also the basis for the technical application in this article.

[0066] It should be noted that when the inventor extracts the characteristic values, the characteristic values are extracted strictly according to the feature points to further ensure that the assumed constant variables are basically numerically approximate. At the same time, because the reservoir generally has a certain degree of heterogeneity, that is, the physical properties vary in the plane and vertically, and the largest changes are in porosity and permeability. Even at the same feature point, there is a certain distribution range for porosity and permeability. Therefore, strict quality control is carried out on the extracted values to ensure that the assumed data is a constant value.

[0067] Step S14: Determine whether the feature point is located in a pure water layer to judge whether the resistivity can be approximately processed; if so, execute step S15; otherwise, execute step S16.

[0068] Step S15: Then regress the linear relationship between the resistivity and the vertical depth of elevation to determine the free water interface depth.

[0069] Step S16: Regress the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the vertical depth of elevation and the free water interface depth to determine the free water interface depth.

[0070] In the embodiment of the present invention, when performing the above steps S14 to S16, the above judgment result is substituted into the equation relationship between the resistivity, the vertical depth of elevation, and the free water interface depth pre-constructed. The construction process of the above equation relationship in the embodiment of the present invention can be as follows:

[0071] Capillary pressure data is usually obtained from a very small core sample, and the core sample can only represent a very small part of the reservoir. During the oilfield development process, generally, multiple sets of capillary pressure data are measured using many core samples. In order to facilitate application, it is necessary to combine all the test data to describe the capillary pressure characteristics of the reservoir. Since the capillary pressure-saturation curves in various porous media have many similar characteristics, in the embodiment of the present invention, a general equation is used to describe all the capillary pressure curves. Since capillary pressure is related to rock porosity, interfacial tension, and average pore radius, the dimensionless function obtained by dividing the measured capillary pressure of the core by the reference capillary pressure is defined as the J(S w ) function. The J(S w ) function is a very useful tool in actual reservoir development. Through J(Sw ) The curves of each processed rock sample are relatively concentrated in shape and can reflect the average characteristics of the reservoir.

[0072] In the embodiment of the present invention, it is assumed that there is a layered formation reservoir with a unified free water interface, and a certain small layer has similar petrophysical characteristics. Then, at a certain point above the free water interface in this small layer, the formula (1) is satisfied, that is:

[0073]

[0074] where p c is the capillary pressure (Pa); σ is the oil-water interfacial tension (N / m); θ is the wetting contact angle (°); K is the air permeability (m 2 ); φ is the porosity (%).

[0075] The above capillary pressure p c is expressed by the formula (2) as follows:

[0076] p c =(ρ w -ρ o )×g×H = Δρ×g×H Formula (2)

[0077] where ρ w is the density of water (kg / m 3 ); ρ o is the density of oil (kg / m 3 ); H is the difference between the elevation vertical depth and the free water interface depth (height from the free water interface, m).

[0078] The expression of the water saturation of the rock is shown in the formula (3) as follows:

[0079] S w =γ×[J(S w )] μ Formula (3)

[0080] where γ and μ are the regression coefficients of the J function.

[0081] Substituting the formula (1) and the formula (2) into the formula (3), the formula (4) can be obtained as follows:

[0082]

[0083] Let t be an intermediate parameter, then the formula (4) is simplified to the formula (5) as follows:

[0084] S w =t×H μ Formula (5)

[0085] In the embodiments of the present invention, the inventor established the relationship curve between the resistivity of the oil and gas reservoir rock and the water saturation according to the rock electrokinetic experiment. Then, the functional relationship between the rock resistivity and the water saturation is shown in Formula (6) as follows:

[0086]

[0087] where a is the lithology coefficient related to the lithology; b is the constant related to the lithology; R w is the resistivity of the formation water (Ω·m); m is the cementation exponent; n is the saturation exponent; R t is the resistivity of the hydrocarbon-bearing formation (Ω·m).

[0088] After combining the above Formula (5) and Formula (6), Formula (7) is obtained as follows:

[0089]

[0090] Since the above Formula (7) is a data set of characteristic points obtained based on the well logging curve comparison slice technology, for a data set of a certain characteristic point, the data has similar rock physical property characteristic values, that is, the same values of a, b, m, n, t, R w , K, φ, γ, μ. Therefore, under the condition of the same characteristic point, the above parameters can be assumed to be constants. At this time, there are two variables in the above Formula (7), namely the resistivity R t and the difference H between the elevation vertical depth and the free water interface depth.

[0091] After taking the logarithm of the above Formula (7), Formula (8) can be obtained as follows:

[0092]

[0093] Let: α = -μn, then Formula (9) can be obtained as follows:

[0094] logR t = α × logH + β Formula (9)

[0095] In order to simplify the above Formula (9), let β = α × logλ, where α and β are intermediate parameters.

[0096] The difference between the elevation vertical depth and the free water interface depth in the embodiments of the present invention is expressed as Formula (10) as follows:

[0097] H = SSTVD - FWL Formula (10)

[0098] where SSTVD is the elevation vertical depth; FWL is the free water interface depth.

[0099] From formulas (9) and (10), formula (11) can be obtained as follows:

[0100] R t = λ α ×(SSTVD - FWL) α Formula (11)

[0101] By arranging formula (11), formula (12) can be obtained as follows:

[0102] Let: After arrangement, formulas (13) and (14) are obtained as follows:

[0103]

[0104] From the Taylor expansion, formula (15) is obtained as follows:

[0105]

[0106] If d×lnR t →0, then the above formula (15) can be approximately processed as formula (16) as follows:

[0107]

[0108] Substituting formula (16) into formula (14) gives formulas (17) and (18) as follows:

[0109] SSTVD = c×(1 + d×lnR t ) + FWL Formula (17)

[0110] SSTVD = c×d×lnR t + FWL + c Formula (18)

[0111] Let: i = c×d, k = FWL + c, then formula (19) is obtained as follows:

[0112] SSTVD = i×lnR t + k Formula (19)

[0113] Among them, α, β, λ, c, d, i, and k are intermediate parameters. Under the same reservoir and the same characteristic value, these variables do not change much and can thus be approximated as constants.

[0114] In the embodiments of the present invention, the inventors obtained the theoretical models of the free water interface elevation depth, the depth from the free water interface, and the resistivity through the above - constructed model, and determined the free water interface depth based on this model.

[0115] The above step S14 determines d×lnR t →0. If so, step S15 is executed; otherwise, step S16 is executed. Among them, in step S15, when the resistivity value is relatively low and the feature point is located in the pure water layer, an approximate processing method is used for data processing, that is, d×lnR t is relatively small, d×lnR t →0, then the formula (19) is approximately processed, and the relationship equations between the elevation vertical depth and the resistivity are respectively regressed to determine the resistivity of the feature point located in the pure water layer and the free water interface depth.

[0116] In the above step S15, if d×lnR t is relatively large and cannot be approximately processed, then taking the formula (9) as the object, assuming that the free water interface (FWL) is a certain initial value, and then in the double logarithmic coordinate, according to the comparison slices, the linear relationship between the resistivity Rt at a certain feature point and the height (H) from the free water interface is regressed. Taking the correlation coefficient R 2 of the regression equation as the optimization target, taking a certain iteration step on the basis of FWL, continuously regressing, and at the same time determining the corresponding R 2 for different feature points. When R 2 is the largest, then the FWL at this time is the final free water interface. The above height from the free water interface in the embodiment of the present invention is the difference between the elevation vertical depth (SSTVD) and the free water interface (FWL).

[0117] In an optional embodiment, the implementation of the above step S16 specifically includes: regressing the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the elevation vertical depth and the free water interface depth, determining the fitting curve equations of different feature points and the relationship between the fitting true value and the scatter value, so as to determine the free water interface depth.

[0118] In a specific embodiment, if the relationship value between the fitting true value and the scatter value of the fitting curves of different feature points is less than or equal to a preset threshold, then the average value of the free water interface depths determined according to the fitting curves fitted by different feature points is determined as the free water interface depth; if the relationship value between the fitting true value and the scatter value of the fitting curves of different feature points is greater than the preset threshold, then the free water interface depth is determined according to the maximum value of the relationship value between the fitting true value and the scatter value.

[0119] In an optional embodiment, in order to satisfy the relationships of the above formula (9), formula (13) and formula (19), and in order to obtain an accurate free water interface depth, the inventor ensures that the basic values of the variables of each assumed constant are equal or approximate when pre-constructing the model. Therefore, after extracting the logging curves of the feature points in the data set, it may further include: judging whether the feature points are abnormal points according to the acoustic travel time, and removing the abnormal points in the data set.

[0120] In the embodiments of the present invention, the above abnormal points are feature points where the data values deviate far from the data distribution region. There can be various ways to determine whether the above feature points are abnormal points, and the embodiments of the present invention are not limited to any form.

[0121] In the embodiments of the present invention, a specific method for removing abnormal points is provided. Referring to Figure 4 shown below:

[0122] Step S41: Determine whether the feature points in the data set need to be grouped according to the distribution range of porosity; if so, execute step S42; otherwise, execute step S43.

[0123] Referring to Figure 5 and Figure 6 shown, the porosity distribution maps of the points traced in the formation between different wells for the same feature point. Among them, Figure 5 the porosity distribution is relatively uniform and the distribution range is large. According to step S42, the feature points are divided into several small data intervals, and then data analysis is performed in intervals; Figure 6 the porosity distribution range is concentrated and the interval range is small. Referring to Figure 6 shown, when there is a dominant distribution in a certain distribution interval, it is not necessary to divide the data into several data intervals. Taking the data in the dominant distribution interval as the object, at this time, the data points corresponding to the maximum distribution frequency are selected for regression according to the distribution frequency. As shown in Figure 6, at this time, the data in interval 2 is the maximum dominant distribution interval, and the data in this interval is picked up for analysis to obtain the free water interface depth.

[0124] Step S42: Then divide the feature points into at least two groups according to the distribution range of porosity, and determine the free water interface depth corresponding to the feature points in each group respectively.

[0125] Step S43: Determine the concentrated area of the feature points according to the distribution range of porosity, so as to determine the free water interface depth corresponding to the feature points in the concentrated area.

[0126] In this embodiment, through the above processing of abnormal points, the accuracy of the model depends on the degree of heterogeneity and data quality control. Quality control must be done well before use to ensure the accuracy of the model.

[0127] In another alternative embodiment, still referring to Figure 2 shown, after removing the abnormal points in the data set, it may further include: judging whether the logging track data matches the logging data;

[0128] If so, execute the step of determining whether the feature points in the data set need to be grouped according to the distribution range of the porosity;

[0129] Otherwise, move the characteristic points in the logging track data and logging data.

[0130] In the embodiment of the present invention, the above-mentioned free water interface determination method is based on the logging curve comparison slice method of characteristic points, constructs the relationship between the free water interface depth, the vertical depth of elevation, and the resistivity, and then determines the free water interface depth. Using this method to determine the free water interface of the oil reservoir, the application results show that the results are reliable, and it can be proved through subsequent verification that it can be fully applied to the initial evaluation stage of the oil reservoir.

[0131] In a specific example, taking Oilfield A in a certain area as an example, referring to Figure 5 As shown, the Mishrif Formation is a long-axis anticline structure with inactive tectonic activities and undeveloped faults. According to the analysis of rock physical properties and electrical characteristics by the inventor, the Mishrif Formation is longitudinally divided into 5 segments: Mi1, Mi2, Mi3, Mi4, and Mi5. Among them, Mi4 is the main target oil reservoir, which is subdivided into 5 small layers, namely: Mi4-1, Mi4-2, Mi4-3, Mi4-4, and Mi4-5. It is laterally continuous and has a stable thickness, and is a typical pore-type bioclastic limestone reservoir. The reservoir type is a layered edge water reservoir with complex pore-throat structures and diverse pore types, showing strong vertical and weak planar heterogeneity. 14 wells in the Mi4 reservoir in the AD-1 well area were tested, and no obvious water layers were found. How to obtain an accurate free water interface and then an accurate saturation field in the absence of well testing data? This method is applied to the determination of the free water interface of this reservoir in this paper.

[0132] In the embodiment of the present invention, the above method is specifically used to determine the free water interface depth, and the specific steps are as follows:

[0133] 1. First, determine 1 characteristic point in Mi4-2 and Mi4-3 respectively, namely S1 and S2. These two characteristic points are the points with the best physical properties in this layer section and are both extreme points in this section (as Figure 8 shown), and then perform logging curve comparison slicing, mainly picking up 4 data: elevation depth, resistivity, acoustic travel time, and porosity.

[0134] 2. After comparing all the logs, perform quality control. The acoustic travel time reflects the change of rock physical properties and can roughly represent the size of porosity. In the embodiment of the present invention, by making a plan view of the acoustic travel time, abnormal points are found. These abnormal points may be caused by comparison errors or local heterogeneity. These points do not conform to the assumption that the parameters are constants in formula (7), resulting in the model parameters in formula (8) becoming variables and causing the model to be inaccurate. Therefore, abnormal points need to be removed. Taking the characteristic point S2 as an example for specific illustration, as Figure 9As shown, it can be seen from the acoustic travel time plan view that there are obvious anomalies in the data of some well logs, including high values (AD-15 and ADM-3-2) and low values (AD-16, AD-2, and AD-8). By checking the original stratification slice data, after verifying that it is caused by heterogeneity, the above abnormal values are removed to obtain the processed acoustic travel time plan distribution map ( Figure 10 ).

[0135] 3. The processed acoustic travel time distribution map is smoother and has no abnormal points. In this case, further data analysis is carried out on the extracted data. Figure 11 It is the porosity frequency distribution map of feature point S2. The distribution frequency in the data interval [0.21 - 0.22] reaches 77.6%, and the data distribution range is relatively concentrated with a small bandwidth. Therefore, the data points in this interval are taken as the object.

[0136] 4. Check the magnitude of d×lnR t , its value is less than 1, and when the resistivity becomes lower, d×lnR t →0. At this time, the relationship between SSTVD and RT can be regressed according to Equation (19), as Figure 12 shown. The relationship between the elevation of S2 and the resistivity is obtained as follows:

[0137] SSTVD = 25.58×lnR t - 2805, R 2 = 0.757

[0138] 5. Both the AD-2 area and the AD-4 area are water layers. Analyze several wells located in the AD-2 area and the AD-4 area and their resistivity values at feature point S2. Among them, the resistivity values of AD-4 and AD-15 wells are the lowest, being 0.7 ohm·m. Substitute this data into the above formula SSTVD = 25.58×lnR t - 2805 to obtain the corresponding depth value of -2815.6 m at this time. Using the same method, the regression relationship of feature point S1 is obtained, and the lowest resistivity of the corresponding water layer is 1.8 ohm·m. At this time, the obtained depth value is 2814.1 m. The specific data is shown in Table 1.

[0139] Table 1

[0140]

[0141] 6. Feature points S1 and S2 respectively represent the points with the best physical properties within the Mi4-2 and Mi4-3 intervals. The free water interface values obtained from these two characteristic values are not very different. Assuming that the free water interface is horizontal, the average value of the two is taken as the free water interface of the oil reservoir: -2814.9 m.

[0142] Based on the same inventive concept, an embodiment of the present invention further provides a free water interface determination device. Referring to Figure 13 as shown in Figure 13 , the device may include: a feature point determination module 131, a data set determination module 132, an extraction module 133, a judgment module 134, and a free water interface determination module 135. The working principle is as follows:

[0143] The feature point determination module 131 is configured to determine feature points in the logging curve based on the logging curve and rock physical properties.

[0144] The data set determination module 132 is configured to track the feature points in the inter-well formation based on the feature points, and determine a data set of a series of the feature points.

[0145] The extraction module 133 is configured to perform logging curve slicing on the feature points in the data set to extract rock physical property characteristic values in the logging curve of the feature points; the rock physical property characteristic values include: elevation vertical depth, resistivity, acoustic travel time, and porosity.

[0146] The judgment module 134 is configured to judge whether the feature points are located in the pure water layer to judge whether the resistivity can be approximately processed.

[0147] If the judgment module 134 judges yes, the free water interface determination module 135 is configured to regress the linear relationship between the resistivity and the elevation vertical depth to determine the free water interface depth; otherwise, the free water interface determination module 135 is configured to regress the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the elevation vertical depth and the free water interface depth to determine the free water interface depth.

[0148] In an optional embodiment, the free water interface determination module 135 determines the free water interface depth by regressing the linear relationship between the resistivity and the elevation vertical depth, including:

[0149]

[0150] d×lnR t →0, then the linear relationship formula between the resistivity and the elevation vertical depth is:

[0151] SSTVD = c×d×lnR t +FWL+c

[0152] Wherein, Rt is the resistivity; d and c are intermediate parameters; SSTVD is the elevation vertical depth;

[0153] Determine the free water interface depth according to the above formula.

[0154] In another alternative embodiment, the free water interface determination module 135 regresses the linear relationship between the logarithm of the resistivity and the logarithm of the difference between the elevation vertical depth and the free water interface depth, determines the fitting curve equation of different characteristic points and the relationship between the fitting true value and the scatter value, so as to determine the free water interface depth.

[0155] In another alternative embodiment, if the relationship value between the fitting true value and the scatter value of the fitting curve of different characteristic points is less than or equal to a preset threshold, the free water interface determination module 135 determines the average value of the free water interface depths determined according to the fitting curves of different characteristic points as the free water interface depth; if the relationship value between the fitting true value and the scatter value of the fitting curve of different characteristic points is greater than the preset threshold, the free water interface determination module 135 determines the free water interface depth according to the maximum value of the relationship value between the fitting true value and the scatter value.

[0156] In another alternative embodiment, referring to Figure 13 As shown, the device may further include an elimination module 136, and the judgment module 134 is further configured to judge whether the characteristic point is an abnormal point according to the acoustic travel time, and the elimination module 136 eliminates the abnormal point in the data set.

[0157] In another alternative embodiment, the judgment module 134 judges whether the characteristic points in the data set need to be grouped according to the distribution range of the porosity; if the judgment module 134 judges yes, the free water interface determination module 135 divides the characteristic points into at least two groups according to the distribution range of the porosity and respectively determines the free water interface depth corresponding to the characteristic points in each group; if the judgment module 134 judges no, the free water interface determination module 135 determines the characteristic point concentration area according to the distribution range of the porosity, so as to determine the free water interface depth corresponding to the characteristic points in the concentration area.

[0158] Based on the same inventive concept, the embodiments of the present invention also provide an application of the free water interface obtained by the above method for determining the free water interface. The above application in this embodiment may be reservoir reserve evaluation, exploitation evaluation, economic benefit evaluation, etc., and the embodiments of the present invention do not make specific limitations thereto.

[0159] Based on the same inventive concept, the embodiments of the present invention also provide a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the above method for determining the free water interface is implemented.

[0160] Based on the same inventive concept, an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the method for determining the free water interface as described above is implemented.

[0161] The principles of the problems solved by the above-mentioned device, medium, and computer device in the embodiments of the present invention are similar to those of the foregoing method for determining the free water interface. Therefore, the implementation of the device, medium, and computer device can refer to the implementation of the foregoing method, and the repeated parts will not be described again.

[0162] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0163] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0164] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0165] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Therefore, the instructions executed on the computer or other programmable device provide means for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1Steps of the functions specified in one or more boxes.

[0166] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for determining a free water interface, It is characterized in that include: Based on the well logging curve and the rock physical properties, determining the characteristic points in the well logging curve; wherein the characteristic points are the points with the best rock physical properties, the dense points and / or the points with the worst rock physical properties; Based on the characteristic points, the characteristic points are tracked in the inter-well formation to determine a series of data sets of the characteristic points; Slicing the logging curve of the characteristic point in the data set to extract the rock property characteristic value in the logging curve of the characteristic point; the rock property characteristic value includes: vertical depth above sea level and resistivity; Pre-construct the equation relationship between the resistivity and the vertical depth of the elevation and the depth of the free water interface, where the Taylor expansion of the equation relationship is as follows: Judge d×ln R t →0; If so, determine that the feature point is located in the pure water layer and calculate SSTVD = c × d × lnR t +FWL + c to regress the linear relationship between the resistivity and the vertical depth of elevation to determine the resistivity of the feature point located in the pure water layer and the free water interface depth; If not, then using log R t = α×log H + β as the object, assume that the free water interface is a certain initial value, and in the double logarithmic coordinate system, obtain the linear relationship between the logarithm of the resistivity regression based on the comparison slices and the logarithm of the difference between the elevation vertical depth and the free water interface depth. Take the correlation coefficient of the regression equation as the optimization target, and on the basis of the free water interface, take a certain iteration step to iteratively regress to determine the correlation coefficients corresponding to different characteristic points, and determine the free water interface depth with the regression equation corresponding to the maximum correlation coefficient; Among them, H = SSTVD-FWL; where Rt is the resistivity; SSTVD is the vertical depth above sea level; FWL is the depth of the free water interface; α, β, c, and d have the same values ​​under the same characteristic value of the same reservoir.

2. The method according to claim 1, It is characterized in that The linear relationship between the logarithm of the regression resistivity and the logarithm of the difference between the vertical depth above sea level and the depth of the free water interface includes: The linear relationship between the logarithm of the resistivity and the logarithm of the difference between the vertical depth above sea level and the free water interface depth is regressed to determine the fitting curve equations of different feature points and the relationship between the fitting true value and the scattered point value.

3. The method according to claim 2, It is characterized in that Determining the fitting curve equation of different characteristic points and the relationship between the fitting true value and the scattered point value to determine the free water interface depth includes: If the relationship between the true value of the fitting curve of different feature points and the scatter value is less than or equal to a preset threshold, the average value of the free water interface depth determined by the fitting curve fitted by different feature points is determined as the free water interface depth; If the relationship values ​​between the fitting true value and the scatter value of the fitting curve at different feature points are greater than a preset threshold, the free water interface depth is determined according to the maximum value of the relationship values ​​between the fitting true value and the scatter value.

4. The method according to claim 1, It is characterized in that The rock property characteristic value also includes the acoustic time difference; after extracting the rock property characteristic value of the logging curve of the characteristic point in the data set, it also includes: Whether the feature point is an abnormal point is determined according to the acoustic wave time difference, and the abnormal point in the data set is eliminated.

5. The method according to claim 4, It is characterized in that The rock physical property characteristic value also includes porosity; the method further includes: judging whether the characteristic points in the data set need to be grouped according to the distribution range of the porosity; If yes, dividing the characteristic points into at least two groups according to the distribution range of the porosity and determining the free water interface depth corresponding to the characteristic points corresponding to each group; Otherwise, the characteristic point concentration area is determined according to the distribution range of the porosity to determine the free water interface depth corresponding to the characteristic points in the concentration area.

6. Application of a free water interface obtained according to the method for determining a free water interface according to any one of claims 1 to 5.

7. A device for determining a free water interface, It is characterized in that include: A feature point determination module, configured to determine feature points in the logging curve based on the logging curve and rock physical properties; wherein the feature points are the points with the best rock physical properties, tight points, and / or the points with the worst rock physical properties; A data set determination module, configured to track the feature points in the inter-well formation based on the feature points, and determine a data set of a series of the feature points; An extraction module, configured to perform logging curve slicing on the feature points in the data set to extract rock physical property characteristic values in the logging curve of the feature points; the rock physical property characteristic values include: elevation vertical depth and resistivity; A pre-construction module, configured to pre-construct an equation relationship between the resistivity and the elevation vertical depth and the free water interface depth, wherein the Taylor expansion of the equation relationship is: A judgment module, used to judge d×lnR t →0; Free water interface determination module, if the judgment module determines it to be yes, the free water interface determination module is used to determine that the feature point is located in the pure water layer and determine the resistivity of the feature point located in the pure water layer and the free water interface depth according to the linear relationship between the SSTVD = c × d × lnR t + FWL + c regression resistivity and the linear relationship of the altitude vertical depth to determine the resistivity of the feature point located in the pure water layer and the free water interface depth; if the judgment module determines it to be no, the free water interface determination module is used to take log R t = α × log H + β as the object, assume that the free water interface is a certain initial value, obtain the linear relationship between the logarithm of the regression resistivity and the logarithm of the difference between the altitude vertical depth and the free water interface depth according to the comparison slice in the double logarithmic coordinate system, and use the correlation coefficient of the regression equation as the optimization target. Take a certain iteration step on the basis of the free water interface to iteratively regress to determine the correlation coefficients corresponding to different feature points, and determine the free water interface depth with the regression equation corresponding to the maximum correlation coefficient; wherein, H = SSTVD - FWL; in the formula, Rt is the resistivity; SSTVD is the elevation vertical depth; FWL is the free water interface depth; α, β, c, d have the same values under the same eigenvalue in the same oil reservoir.

8. A computer-readable storage medium, on which a computer program is stored, characterized in that, when the program is executed by a processor, it implements the method for determining the free water interface according to any one of claims 1 to 5.

9. A computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, when the processor executes the program, it implements the method for determining the free water interface according to any one of claims 1 to 5.

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