Intermediate target layer interpretation method for non-invasion ultrathin interbed group stratigraphic model

Abstract

The invention provides a logging information interpretation method for accurately solving true resistivity of a middle target stratum of a non-invasion ultrathin interbed group stratum model, which comprises the following steps of: firstly, designing a plurality of non-invasion ultrathin interbed group stratum models according to reservoir characteristics of a research area, and calculating an equivalent surrounding rock coefficient of the middle target stratum of each ultrathin interbed group; traditional non-invasion three-layer single homogeneous layer stratum models with different layer thicknesses are designed, and the optimal interpretation thickness of the middle target layer of each ultrathin interbed group is obtained; establishing an apparent resistivity fitting equation of the intermediate target layer of the ultrathin interbed group corresponding to each optimal interpretation thickness, preferably selecting the optimal interpretation thickness of the intermediate target layer according to the equivalent surrounding rock coefficient, and combining the optimal interpretation thickness with the apparent resistivity of a single homogeneous layer; quantitative interpretation of the stratum true resistivity of the middle target layer of the non-invasion ultrathin interbed group stratum model can be realized, and the interpretation precision of the stratum true resistivity of the ultrathin interbed group is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of open-hole well logging in oil and gas exploration and development. Specifically, it relates to a logging interpretation method for accurately solving the true resistivity of the middle target formation in a non-invading ultra-thin interbed group formation model. Background Art

[0002] After years of water injection development in most large oil fields in China, the main thick oil layers have almost all reached strong water flooding, and the comprehensive water cut of most oil fields has even reached more than 90%. Thin layers and thin interbeds are widely developed in most continental sedimentary oil fields, and their remaining reserves are quite considerable. To ensure continuous stable production and increased production, at present, most domestic oil fields have taken thin layers and thin interbeds as the main targets for internal potential tapping, and a large number of new high-resolution logging instruments have been put into production and application. Logging interpretation of thin interbed groups is imminent.

[0003] Due to the influence of heterogeneous high surrounding rocks, the apparent resistivity value measured under the condition of the same true resistivity of the formation for the middle target formation in the ultra-thin interbed group is much higher than the measurement result of a single homogeneous layer. In theory, the true resistivity of the formation can be interpreted from the high surrounding rock correction chart. However, in practical applications, there are the following two problems: Problem 1, in the ultra-thin interbed group, the surrounding rock of the middle target formation is also a heterogeneous layer composed of multiple thin layers, and the resistivity value of the equivalent surrounding rock varies within a large range and is difficult to accurately determine; Problem 2, in order to meet the correction accuracy of the influence of the thin layer thickness of the middle target formation in the ultra-thin interbed group, at least 22 groups of high surrounding rock correction charts with different thicknesses from 0.2 m to 4.8 m need to be studied for each surrounding rock.

[0004] To adapt to complex changes such as different target formation thicknesses and different surrounding rocks, it takes a lot of time to develop hundreds of high surrounding rock correction charts. When processing actual logging data, since the actual surrounding rock value of the target formation often cannot be accurately determined, the accuracy of resistivity correction of the target formation cannot be ensured finally. Similarly, affected by the initial value, multi-solution, stability, and timeliness of the formation model, it is also very difficult to quickly obtain the true resistivity of the middle target formation in the ultra-thin interbed group that meets the requirements of logging interpretation and evaluation accuracy by iterative inversion of high-resolution resistivity logging data. Therefore, there is currently no accurate quantitative interpretation method for the true resistivity of the middle target formation in the ultra-thin interbed group formation model. Summary of the Invention

[0005] The present invention proposes a non-invasive ultra-thin interbed group formation model's most middle target layer interpretation method, provides an innovative idea and interpretation method for increasing the interpretation thickness of the most middle target layer of the ultra-thin interbed group formation model, offsets the influence of heterogeneous high surrounding rock on the resistivity measurement accuracy of the most middle target layer of the ultra-thin interbed group, solves the problem that the heterogeneous surrounding rock of the ultra-thin interbed group cannot be accurately obtained and the resistivity correction of the most middle target layer cannot be performed, greatly improves the quantitative interpretation accuracy of the true resistivity of the most middle target layer of the ultra-thin interbed group, and effectively solves the problem that such reservoirs cannot be accurately interpreted so far.

[0006] The technical solution provided by the present invention is a method for interpreting the middlemost target layer of a non-invasive ultra-thin interbedded formation model, comprising the following steps:

[0007] S1: Design of non-invasive ultra-thin interbedded formation model and calculation of equivalent surrounding rock coefficient of the middle target layer:

[0008] S1.1: Design of the stratigraphic model of non-invasive ultra-thin interbedded groups: The designed stratigraphic model of ultra-thin interbedded groups consists of five non-invasive strata, which are upper thick surrounding rock, upper thin adjacent layer A, middle thin target layer B, lower thin adjacent layer C and lower thick surrounding rock from top to bottom. The thickness of the three thin layers A, B and C in the middle ultra-thin interbedded group and their true resistivity values ​​R t Designed according to the reservoir characteristics of the study area, the variation range of formation resistivity of all reservoirs in the study area should be covered as much as possible;

[0009] S1.2: Apparent resistivity of each thin layer in the ultra-thin interbed group and equivalent surrounding rock coefficient calculation of the middle target layer: The finite element method is used to perform resistivity logging on all the non-invasive ultra-thin interbed group formation models designed in S1.1. a Numerical simulation, the apparent resistivity reading rules of the three middle thin layers A, B, and C are as follows:

[0010] ① Apparent resistivity of the middle target layer When the apparent resistivity curve of the middle target layer B has a non-monotonic extreme value, the extreme value point is selected as the reading point, otherwise the midpoint of the formation is selected as the reading point;

[0011] ② Apparent resistivity of the upper and lower thin adjacent layers The midpoint of the formation is selected as the reading point.

[0012] In order to consider the influence of thin adjacent layers and thick surrounding rocks on the apparent resistivity of the middle target layer, the equivalent surrounding rock coefficient is introduced The calculation formula is:

[0013] S2: Design of traditional non-intrusive three-layer single homogeneous formation model and determination of the best interpretation thickness of the middle target layer of the ultra-thin interlayer group:

[0014] S2.1: Design of Traditional Non-invasive Three-layer Single Homogeneous Formation Model and Establishment of Result Database: To offset the influence of heterogeneous high surrounding rock on the apparent resistivity of the middle target layer, the method of increasing the interpreted thickness of the target layer is adopted. To accurately select the best interpreted thickness of the middle target layer in each non-invasive ultra-thin interbed group formation model, different thicknesses of the middle single homogeneous layer are designed on the traditional non-invasive three-layer formation model. The formation parameters of the middle single homogeneous layer are designed as follows:

[0015] ① Thickness H of the middle single homogeneous layer: To ensure the calibration accuracy of the thin layer thickness, the change range of the thickness of the middle single homogeneous layer should be large enough and the value interval should be dense enough. As the layer thickness increases from small to large, the value interval must follow the principle of becoming sparser from dense;

[0016] ② True resistivity R of the middle single homogeneous layer formation t : The true resistivity value of the middle single homogeneous layer formation must be the same as the true resistivity value of the middle target layer formation in the non-invasive ultra-thin interbed group formation model designed in S1.1.

[0017] In the traditional non-invasive three-layer single homogeneous formation model, the apparent resistivity R of the resistivity logging is also numerically simulated by the finite element method a , and the simulation result at the midpoint position of the middle single homogeneous layer is selected as the apparent resistivity of this layer and the corresponding database is established.

[0018] S2.2: Determination of the Best Interpreted Thickness of the Middle Target Layer in the Ultra-thin Interbed Group: According to the true resistivity R of the middle target layer formation in any ultra-thin interbed group formation model designed in S1.1 t and its corresponding apparent resistivity Search for the single homogeneous layer with the same true resistivity R t in the single homogeneous layer result database and the smallest absolute value of the relative error of the apparent resistivity ( ), and take its formation thickness H as the best interpreted thickness H of the middle target layer in this ultra-thin interbed group be , which can effectively offset the influence of heterogeneous high surrounding rock on the apparent resistivity of the middle target layer and minimize the interpretation error of the true resistivity R t value.

[0019] S3: Relationship between Apparent Resistivity and Equivalent Surrounding Rock Coefficient of the Middle Target Layer in the Non-invasive Ultra-thin Interbed Group Formation Model: Through S1 and S2, a result database of the non-invasive ultra-thin interbed group formation model is established. By statistically analyzing the result data of all ultra-thin interbed group formation models with the same best interpreted thickness, it is found that:

[0020] ① For each best interpreted thickness H be , the apparent resistivity of the middle target layer in all ultra-thin interbed group formation models it contains and the equivalent surrounding rock coefficient There is a good linear relationship;

[0021] ② As the optimal interpretation thickness H be increases, the apparent resistivity of the middle target layer and the equivalent surrounding rock coefficient The linear fitting coefficient (slope) between them also gradually increases, and the intercept varies within a large range;

[0022] ③ Under the condition of the same apparent resistivity of the middle target layer of the ultra-thin interbed group, the equivalent surrounding rock coefficient decreases rapidly as the optimal interpretation thickness H be increases;

[0023] ④ When the optimal interpretation thickness H be of the middle target layer of the ultra-thin interbed group is the same as the total thickness of the ultra-thin interbed group, the number of ultra-thin interbed group models it contains is the largest, and the apparent resistivity of the middle target layer and the equivalent surrounding rock coefficient have the longest linear fitting section, and there are intersection points with the linear fitting sections of some other optimal interpretation thicknesses.

[0024] According to the above four characteristics, the optimal selection criteria and determination method for the optimal interpretation thickness of the middle target layer of the non-invasive ultra-thin interbed group can be established.

[0025] S4: Determination of the interpretation method for the middle target layer of the non-invasive ultra-thin interbed group formation model:

[0026] S4.1: Optimal selection criteria for the optimal interpretation thickness of the middle target layer of the non-invasive ultra-thin interbed group:

[0027] ① Substitute the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group into all the established apparent resistivity fitting equations, and the calculation result be of the apparent resistivity fitting equation corresponding to the optimal interpretation thickness H should have the smallest absolute value of the relative error with the measured apparent resistivity of the middle target layer ( );

[0028] ② The measured apparent resistivity of the middle target layer of the non-invasive ultra-thin interbed group should be within the range of the apparent resistivity corresponding to the optimal interpretation thickness H be ;

[0029] ③ The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group should be within the range of the equivalent surrounding rock coefficient corresponding to the optimal interpretation thickness H be ;

[0030] S4.2: Method and steps for determining the best interpreted thickness of the middle target layer of the non-invasive ultra-thin interbed group:

[0031] S4.2.1: Search for the apparent resistivity variation range of the middle target layer corresponding to all interpreted thicknesses, including the apparent resistivity value of the middle target layer of the measured non-invasive ultra-thin interbed group Explanation thickness.

[0032] S4.2.2: Search for the equivalent surrounding rock coefficient in the range of all interpreted thicknesses, including the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group. Explanation thickness.

[0033] S4.2.3: The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group Substitute the apparent resistivity fitting equation of the middle target layer corresponding to all interpreted thicknesses that meet the requirements of S4.2.1 and S4.2.2, and select the calculated apparent resistivity of the middle target layer. With the measured The absolute value of relative error ( ) The minimum interpretation thickness is taken as the optimal interpretation thickness H be .

[0034] S4.3: Quantitative interpretation of true resistivity of the middle target layer of the non-invasive ultra-thin interbed group: Based on the best interpretation thickness H determined in S4.2 be , find the best interpretation thickness H of the stratigraphic thickness H and the middle target layer of the non-invasive ultra-thin interbed group in the single homogeneous layer database be Same, apparent resistivity Compared with the measured apparent resistivity of the middle target layer of the non-invasive ultra-thin interbed group The absolute value of relative error ( ) The minimum true resistivity R of two single homogeneous layers t Finally, the formation resistivity of the middle target layer of the non-invasive ultra-thin interbed group is calculated by linear interpolation method.

[0035] The present invention has at least the following beneficial effects:

[0036] ⑴ The present invention proposes an innovative idea and interpretation method for increasing the interpreted thickness of the middle target layer of the ultra-thin interbedded formation model, which offsets the influence of heterogeneous high surrounding rock on the resistivity measurement accuracy of the middle target layer of the ultra-thin interbedded formation, and solves the problem that the heterogeneous high surrounding rock of the ultra-thin interbedded formation cannot be accurately obtained and the resistivity correction of the middle target layer cannot be performed.

[0037] ⑵ The present invention proposes an interpretation method for the middle target layer of the non-invasive ultra-thin interbed formation model. When this method is applied in practice, it is not restricted by resistivity logging instruments, the total thickness of the interbed group, the thickness of a single layer, or the magnitude of the formation resistivity value. A corresponding formation model can be established according to the reservoir characteristics of the study area, and numerical simulation and apparent resistivity correction can be carried out based on the actually measured resistivity logging instrument. This method can be extended to all interbed group models for application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of the interpretation method for the middle target layer of the non-invasive ultra-thin interbed formation model of the present invention;

[0039] Figure 2 It is a schematic diagram of the non-invasive ultra-thin interbed formation model and the non-invasive three-layer single homogeneous formation model;

[0040] Figure 3 For the interbed group of the embodiment of the present invention, the total layer thickness is 0.6 m, the thickness of a single layer is 0.2 m, the first group and two non-invasive ultra-thin interbed formation models and the deep triple lateral logging apparent resistivity curve graphs;

[0041] Figure 4 It is a graph showing the relationship between the deep triple lateral apparent resistivity of the middle target layer of the non-invasive ultra-thin interbed formation model and the equivalent surrounding rock coefficient at different optimal interpretation thicknesses for the interbed group of the embodiment of the present invention, with the total layer thickness of 0.6 m and the thickness of a single layer of 0.2 m. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The following further illustrates the technical solution of the present invention in conjunction with the drawings and embodiments.

[0043] The following constructs a non-invasive ultra-thin interbed formation model and a traditional non-invasive three-layer single homogeneous formation model according to the reservoir characteristics of the tight sandstone ultra-thin interbed group in the Qingshankou Formation in the Qijia area in the northern Songliao Basin. The finite element method is used to numerically simulate the apparent resistivity of the deep triple lateral resistivity logging, and a corresponding result database is established. Here, a non-invasive ultra-thin interbed formation model composed of three 0.2 m thick equal-thickness thin layers is selected as an embodiment, and the present application is described in detail in conjunction with the drawings and tables.

[0044] An interpretation method for the middle target formation of a non-invasive ultra-thin interbed formation model includes the following steps, as Figure 1 shown:

[0045] S1: Design of the non-invasive ultra-thin interbed formation model and calculation of the equivalent surrounding rock coefficient of the middle target layer:

[0046] S1.1: Design of the formation model of non-invasive ultra-thin interbedded groups: The designed formation model of ultra-thin interbedded groups consists of five non-invasive formations, which are the upper thick surrounding rock, the upper thin adjacent layer A, the middle thin target layer B, the lower thin adjacent layer C, and the lower thick surrounding rock from top to bottom, as shown in Figure 2 Figure a; The thickness of the three thin layers A, B, and C in the middle ultra-thin interbedded group is 0.2 m each, and the total thickness is 0.6 m. The true formation resistivity R t A total of four groups are designed (the first superscript number represents the group number, and the second represents the serial number):

[0047] The first group:

[0048] The second group:

[0049] The third group:

[0050] The fourth group:

[0051] Taking the first group as an example, the true formation resistivities of the three middle thin layers A, B, and C are combined into

[0052] 22 ultra-thin interbedded groups (each group can be combined into a maximum of 4×4×4 = 64 ultra-thin interbedded groups. Considering factors such as repeatability and symmetry, only 22 are actually designed, which have covered all possible apparent resistivity change ranges and thin interbedded group combination types of this group, greatly improving the modeling efficiency). The four groups of true formation resistivities can form a total of 22×4 = 88 formation models of non-invasive ultra-thin interbedded groups.

[0053] S1.2: Calculation of the deep triple lateral logging apparent resistivity of each thin layer in the ultra-thin interbedded group and the equivalent surrounding rock coefficient of the middle target layer: The finite element method is used to numerically simulate the deep triple lateral logging apparent resistivity R a of the 88 formation models of non-invasive ultra-thin interbedded groups designed in S1.1, Figure 3 and draw the deep triple lateral logging apparent resistivity curves of and two formation models of ultra-thin interbedded groups. Table 1 gives the result table of the formation model of the first group of non-invasive ultra-thin interbedded groups.

[0054] The reading rules of the deep triple lateral apparent resistivity of the three middle thin layers A, B, and C are as follows:

[0055] ① The deep triple lateral apparent resistivity of the middle target layer When there are non-monotonic extreme values in the deep triple lateral apparent resistivity curve of the middle target layer B, select the extreme value point as the reading point ( Figure 3 Figure a, the first group The apparent resistivity of the deep laterolog of the middle target layer of the invasion-free ultra-thin interbedded formation model ), otherwise select the midpoint of the formation as the reading point( Figure 3 b, the first group The apparent resistivity of the deep laterolog of the middle target layer of the invasion-free ultra-thin interbedded formation model );

[0056] ② The apparent resistivity of the deep laterolog of the upper and lower thin adjacent layers Both select the midpoint of the formation as the reading point as Figure 3 shown in a, the first group The apparent resistivity of the deep laterolog of the upper and lower thin adjacent layers of the invasion-free ultra-thin interbedded formation model such as Figure 3 shown in b, the first group The apparent resistivity of the deep laterolog of the upper and lower thin adjacent layers of the invasion-free ultra-thin interbedded formation model

[0057] To consider the influence of thin adjacent layers and thick surrounding rocks on the apparent resistivity of the deep laterolog of the middle target layer, an equivalent surrounding rock coefficient is introduced Its calculation formula is:

[0058] Taking the first group of the invasion-free ultra-thin interbedded formation model as an example, the equivalent surrounding rock coefficient of its middle target layer

[0059] Table 1 Results table of the first group of the invasion-free ultra-thin interbedded formation model

[0060]

[0061] S2: Design of the traditional invasion-free three-layer single homogeneous formation model and determination of the best interpretation thickness of the middle target layer of the ultra-thin interbedded formation:

[0062] S2.1: Design of the traditional invasion-free three-layer single homogeneous formation model and establishment of the result database: To offset the influence of heterogeneous high surrounding rocks on the apparent resistivity of the deep laterolog of the middle target layer, the method of increasing the interpretation thickness of the target layer is adopted. To accurately select the best interpretation thickness of the middle target layer in each invasion-free ultra-thin interbedded formation model, different thicknesses of the middle single homogeneous layer are designed on the traditional invasion-free three-layer formation model (such as Figure 2 shown in b), and the formation parameters of the middle single homogeneous layer are designed as follows:

[0063] ① Thickness H of the middle single homogeneous layer: To ensure the calibration accuracy of the thin layer thickness, the thicknesses of the middle single homogeneous layers are taken as 0.2 m, 0.22 m, 0.24 m, 0.26 m, 0.28 m, 0.3 m, 0.325 m, 0.35 m, 0.375 m, 0.4 m, 0.45 m, 0.5 m, 0.55 m, 0.6 m, 0.7 m, 0.8 m, 1.0 m, 1.2 m, 1.8 m, 2.4 m, 3.6 m, and 4.8 m, a total of 22 values. The variation range of the layer thickness is large enough and the value intervals are dense enough. The layer thickness increases from small to large, and the value intervals follow the principle of being dense first and then sparse.

[0064] ② True resistivity R of the formation of the middle single homogeneous layer t : The true resistivity value of the formation of the middle single homogeneous layer must be the same as the true resistivity value of the middle target layer of the non-invaded ultra-thin interbed group formation model designed in S1.1, that is, 36 Ω·m, 32 Ω·m, 30 Ω·m, 28 Ω·m, 26 Ω·m, 24 Ω·m, 22 Ω·m, 20 Ω·m, 18 Ω·m, 15 Ω·m, 12 Ω·m, 10 Ω·m, 7 Ω·m, 5 Ω·m, 4 Ω·m, 3 Ω·m, a total of 16 values.

[0065] Finally, 22×16 = 352 middle single homogeneous layers are designed. In the traditional non-invaded three-layer single homogeneous formation model, the apparent resistivity R of the deep triple lateral logging is also numerically simulated by the finite element method a , and the simulation result at the midpoint position of the middle single homogeneous layer is selected as the apparent resistivity of the deep triple lateral of this layer And a corresponding database is established. Table 2 gives the result table of the single homogeneous layer.

[0066] S2.2: Determination of the best interpretation thickness of the middle target layer of the ultra-thin interbed group: For the true resistivity R of the formation of the middle target layer of any ultra-thin interbed group formation model designed in S1.1 t and its corresponding apparent resistivity of the deep triple lateral Search for the single homogeneous layer with the same true resistivity R of the formation in the result database of the single homogeneous layer and the smallest absolute value of the relative error of the apparent resistivity of the deep triple lateral ( t ), and take its formation thickness H as the best interpretation thickness H of the middle target layer of this ultra-thin interbed group be , which can effectively offset the influence of the heterogeneous high surrounding rock on the apparent resistivity of the middle target layer, and minimize the interpretation error of the true resistivity R value of the formation. t t

[0067] Taking the first group of non-invaded ultra-thin interbed group formation models as an example, the true resistivity R of the formation of the middle target layer t = 36 Ω·m, the apparent resistivity of the deep triple lateral In the R of Table 2t Find the deep triple lateral apparent resistivity with the smallest absolute relative error in the column of The deep triple lateral apparent resistivity ( ), and the corresponding layer thickness H = 0.6m is the best interpretation thickness H of the middle target layer of this ultra-thin interbed group be = 0.6m.

[0068]

[0069]

[0070] S3: Relationship between the deep triple lateral apparent resistivity of the middle target layer of the non-invaded ultra-thin interbed group formation model and the equivalent surrounding rock coefficient: By establishing the achievement database of the non-invaded ultra-thin interbed group formation model through S1 and S2, it is found by statistically analyzing all the achievement data of the ultra-thin interbed group formation models with the same best interpretation thickness (as Figure 4 shown):

[0071] ① For each best interpretation thickness H be (H be <= 1.2m), there is a good linear relationship between the deep triple lateral apparent resistivity of the middle target layer of all the ultra-thin interbed group formation models it contains and the equivalent surrounding rock coefficient . The value of the deep triple lateral apparent resistivity of the middle target layer calculated by the 14 deep triple lateral apparent resistivity linear fitting equations and the numerical simulation value by the finite element method have an average relative error of only 1.54%; for all the ultra-thin interbed group formation models corresponding to the best interpretation thickness H be = 4.8m, the change ranges of the deep triple lateral apparent resistivity of their middle target layer and the equivalent surrounding rock coefficient are too small to accurately establish the fitting relationship between the two;

[0072] ② As the best interpretation thickness H be increases, the linear fitting coefficient (slope) between the deep triple lateral apparent resistivity of the middle target layer and the equivalent surrounding rock coefficient also gradually increases, and the intercept change range is relatively large;

[0073] ③ Under the condition of the same deep triple lateral apparent resistivity of the middle target layer, the equivalent surrounding rock coefficient rapidly decreases as the best interpretation thickness H be increases;

[0074] ④ When the best interpretation thickness H of the middle target layer of the ultra-thin interbed group beWhen it is the same as the total thickness of the ultra-thin interbedded group (the total thickness of the ultra-thin interbedded group in this design is 0.6 m), the number of ultra-thin interbedded group models it contains is the largest, and the apparent deep lateral resistivity of the middle target layer and the equivalent surrounding rock coefficient have the longest linear fitting segment, and there are intersection points with the linear fitting segments of the best interpretation thickness of some other individual cases.

[0075] Based on the above four characteristics, the optimization criteria and determination method for the best interpretation thickness of the middle target layer of the non-invasive ultra-thin interbedded group can be established.

[0076] S4: Determination of the interpretation method for the middle target layer of the non-invasive ultra-thin interbedded group formation model:

[0077] S4.1: Optimization criteria for the best interpretation thickness of the middle target layer of the non-invasive ultra-thin interbedded group (Table 3):

[0078] ① Substitute the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbedded group into all the established deep lateral apparent resistivity fitting equations, and the calculation result be of the deep lateral apparent resistivity fitting equation corresponding to the best interpretation thickness H should have the smallest absolute value of relative error ([[]] ) with the measured deep lateral apparent resistivity of the middle target layer;

[0079] ② The measured deep lateral apparent resistivity of the middle target layer of the non-invasive ultra-thin interbedded group should be within the variation range of the deep lateral apparent resistivity corresponding to the best interpretation thickness H be ;

[0080] ③ The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbedded group should be within the variation range of the equivalent surrounding rock coefficient corresponding to the best interpretation thickness H be .

[0081] Table 3 Optimization criteria table for the best interpretation thickness of the middle target layer of the non-invasive ultra-thin interbedded group formation model

[0082]

[0083] S4.2: Determination method and steps for the best interpretation thickness of the middle target layer of the non-invasive ultra-thin interbedded group:

[0084] S4.2.1: Search in the variation range of the deep lateral apparent resistivity of the middle target layer corresponding to all interpretation thicknesses to find the interpretation thickness that includes the measured deep lateral apparent resistivity value of the middle target layer of the non-invasive ultra-thin interbedded group.

[0085] Take the first group Taking the formation model of the non-invasion ultra-thin interbedded group as an example, the apparent resistivity of the deep triple lateral logging of the middle target layer was measured. In the case of interpreting the thickness H be = 0.5m, 0.525m, 0.55m, 0.6m, 0.7m, 0.8m, within the range of the apparent resistivity of the deep triple lateral logging corresponding to the 6 interpreted thicknesses.

[0086] S4.2.2: Search within the range of the equivalent surrounding rock coefficients corresponding to all interpreted thicknesses, including the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasion ultra-thin interbedded group. The interpreted thickness.

[0087] Taking the first group Taking the formation model of the non-invasion ultra-thin interbedded group as an example, the equivalent surrounding rock coefficient of the middle target layer was measured and calculated. In the case of interpreting the thickness H be = 0.4m, 0.45m, 0.5m, 0.525m, 0.55m, 0.6m, within the range of the equivalent surrounding rock coefficients corresponding to the 6 interpreted thicknesses.

[0088] S4.2.3: Substitute the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasion ultra-thin interbedded group into the fitting equation of the apparent resistivity of the deep triple lateral logging of the middle target layer corresponding to all interpreted thicknesses (H be <= 1.2m) that meet the requirements of S4.2.1 and S4.2.2, and select the calculated apparent resistivity of the deep triple lateral logging of the middle target layer and the measured apparent resistivity of the deep triple lateral logging The absolute value of the relative error ( ) is the smallest when the interpreted thickness is used as the best interpreted thickness H be ; when the interpreted thickness that meets the requirements of S4.2.1 and S4.2.2 is 4.8m, the best interpreted thickness is 4.8m.

[0089] Taking the first group Taking the formation model of the non-invasion ultra-thin interbedded group as an example, there are 4 interpreted thicknesses that meet the requirements of S4.2.1 and S4.2.2, H be = 0.5m, 0.525m, 0.55m, 0.6m. Substitute the measured equivalent surrounding rock coefficient into the fitting equation of the apparent resistivity of the deep triple lateral logging corresponding to the 4 interpreted thicknesses, and obtain the fitting results of the apparent resistivity of the deep triple lateral logging of the middle target layer 12.37Ω.m, 13.14Ω.m, 14.60Ω.m. The absolute values of their relative errors with the measured apparent resistivity of the deep triple lateral logging are respectively: 19.75%, 14.28%, 8.94% and 1.18%. According to the optimization criteria, the first group The optimal interpreted thickness of the middle target layer of the non-invasion ultra-thin interbedded formation model is taken as H be = 0.6m.

[0090] For the first group of the non-invasion ultra-thin interbedded formation model, the apparent deep lateral resistivity of the middle target layer measured in it According to S4.2.1 and S4.2.2, determine its optimal interpreted thickness H of the middle target layer be = 4.8m.

[0091] Based on the verification one by one of a total of 88 non-invasion ultra-thin interbedded formation models, the optimal interpreted thickness of the middle target layer determined by the above standard is completely consistent with the theoretically calculated value.

[0092] S4.3: Quantitative interpretation of the true resistivity of the middle target layer of the non-invasion ultra-thin interbedded formation: According to the optimal interpreted thickness H determined by S4.2 be , find in the single homogeneous layer result table (Table 2) the formation thickness H and the optimal interpreted thickness H of the middle target layer of the non-invasion ultra-thin interbedded formation be that are the same, the apparent resistivity and the apparent resistivity of the middle target layer of the measured non-invasion ultra-thin interbedded formation with the smallest absolute value of relative error ( ), and finally calculate the formation resistivity of the middle target layer of this non-invasion ultra-thin interbedded formation by linear interpolation t .

[0093] Taking the first group of the non-invasion ultra-thin interbedded formation model as an example, determine its optimal interpreted thickness H of the middle target layer by S4.2 be = 0.6m, and find in the row of formation thickness H = 0.6m in the single homogeneous layer result table (Table 2) the two single homogeneous layer apparent resistivities with the smallest absolute value of relative error ( ) with respect to the apparent deep lateral resistivity of the middle target layer of the measured non-invasion ultra-thin interbedded formation 13.48 Ω.m, and the corresponding true resistivity R of the single homogeneous layer t = 24 Ω.m and 22 Ω.m. By linear interpolation, it can be obtained that for the first group of the non-invasion ultra-thin interbedded formation, the formation resistivity of the middle target layer is increased by 64% compared with the apparent deep lateral resistivity , and the absolute value of the relative error ( t ) with respect to the true resistivity R = 24 Ω.m is only 1.49%, compared with the absolute value of the relative error when the apparent resistivity is used ( ) ) It has decreased by 38 percentage points, greatly improving the resistivity interpretation accuracy of ultra-thin interbeds and meeting the requirements of logging interpretation and evaluation.

[0094] For the first group The formation model of the non-invaded ultra-thin interbed group, the optimal interpreted thickness H of its middle target layer be = 4.8m. In the formation thickness H = 4.8m row of the single homogeneous layer result table (Table 2), find the two single homogeneous layer apparent resistivities with the smallest absolute value of relative error ( ) of the deep triple lateral apparent resistivity of the middle target layer of the measured non-invaded ultra-thin interbed group 3.10 Ω·m, and the true formation resistivity R of the corresponding single homogeneous layer t = 5 Ω·m and 4 Ω·m. Through linear interpolation, it can be obtained that the formation resistivity of the middle target layer of the first group of the non-invaded ultra-thin interbed group is 33% higher than the deep triple lateral apparent resistivity , and the absolute value of the relative error with the true formation resistivity R t = 5 Ω·m is 7.41%, which is nearly 12 percentage points lower than the absolute value of the relative error (19%) at the time of apparent resistivity, verifying the effectiveness and accuracy of the method of this application once again.

[0095] After verification one by one of a total of 88 formation models of non-invaded ultra-thin interbed groups, the average absolute value of the interpreted relative error of the true formation resistivity of the middle target layer of the ultra-thin interbed group determined by the optimal interpreted thickness method is only 3.12%, achieving a very ideal effect. From theory to practice, it fully shows that the interpretation method proposed in this application can effectively correct the influence of inhomogeneous high surrounding rock on the measurement of the middle layer of the thin interbed group, and greatly improve the quantitative interpretation accuracy of the true formation resistivity.

Claims

1. A method for interpreting the middle target layer of a non-invasive ultra-thin interbedded formation model, comprising the following steps: S1: Construction of stratigraphic model of non-invasive ultra-thin interbedded group and calculation of equivalent surrounding rock coefficient of the middle target layer: S1.1: Constructing the stratigraphic model of non-invasive ultra-thin interbedded groups: The stratigraphic model of ultra-thin interbedded groups consists of five non-invasive strata, which are, from top to bottom, upper thick surrounding rock, upper thin adjacent layer A, middle thin target layer B, lower thin adjacent layer C, and lower thick surrounding rock; the thickness of the three thin layers A, B, and C in the middle ultra-thin interbedded group and their true resistivity values ​​R t Designed according to the reservoir characteristics of the study area, the variation range of formation resistivity of all reservoirs in the study area should be covered as much as possible; S1.2: Apparent resistivity of each thin layer in the ultra-thin interbed group and calculation of equivalent surrounding rock coefficient of the middle target layer: The finite element method is used to perform resistivity logging on all the non-invasive ultra-thin interbed group formation models designed in S1.

1. a Numerical simulation; S2: Design of the traditional non-intrusive three-layer single homogeneous stratigraphic model and determination of the best interpreted thickness of the middle target layer of the ultra-thin interbedded group; S2.1: Design of traditional non-invasive three-layer single homogeneous formation model and establishment of results database: In order to offset the influence of heterogeneous high surrounding rock on the apparent resistivity of the middle target layer, the method of increasing the interpreted thickness of the target layer is adopted; in order to accurately select the best interpreted thickness of the middle target layer in each non-invasive ultra-thin interbedded formation model, the middle single homogeneous layer with different thicknesses is designed on the traditional non-invasive three-layer formation model; S2.2: Determination of the best interpreted thickness of the middle target layer of the ultra-thin interbed group: According to the true resistivity R of the middle target layer of any ultra-thin interbed group formation model designed in S1.1 t And its corresponding apparent resistivity Finding the true resistivity R of formation in the database of single homogeneous layer results t Same, absolute value of relative error of apparent resistivity The smallest single homogeneous layer, whose stratigraphic thickness H is taken as the best interpretation thickness H of the middle target layer of the ultra-thin interbed group be , which can effectively offset the influence of heterogeneous high surrounding rock on the apparent resistivity of the middle target layer, making the true resistivity of the formation R t The value interpretation error is minimal; S3: Relationship between apparent resistivity and equivalent surrounding rock coefficient of the middle target layer in the non-invasive ultra-thin interbedded formation model: A non-invasive ultra-thin interbedded formation model database was established through S1 and S2, and all ultra-thin interbedded formation model data with the same best interpretation thickness were counted; S4: Determination of the interpretation method of the middle target layer in the stratigraphic model of the non-invasive ultra-thin interbedded group: S4.1: Optimization criteria for the best interpretation thickness of the middle target layer of the non-invasive ultra-thin interbed group; S4.2: Method and steps for determining the best interpreted thickness of the middle target layer of the non-invasive ultra-thin interbed group: S4.2.1: Search for the apparent resistivity variation range of the middle target layer corresponding to all interpreted thicknesses, including the apparent resistivity value of the middle target layer of the measured non-invasive ultra-thin interbed group The thickness of the explanation; S4.2.2: Search for the equivalent surrounding rock coefficient in the range of all interpreted thicknesses, including the equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group. The thickness of the explanation; S4.2.3: The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group Substitute the apparent resistivity fitting equation of the middle target layer corresponding to all interpreted thicknesses that meet the requirements of S4.2.1 and S4.2.2, and select the calculated apparent resistivity of the middle target layer. With the measured Relative error absolute value The minimum interpretation thickness is taken as the optimal interpretation thickness H be ; S4.3: Quantitative interpretation of true resistivity of the middle target layer of the non-invasive ultra-thin interbed group: Based on the best interpretation thickness H determined in S4.2 be , find the best interpretation thickness H of the formation and the middle target layer of the non-invasive ultra-thin interbed group in the single homogeneous layer database be Same, apparent resistivity Compared with the measured apparent resistivity of the middle target layer of the non-invasive ultra-thin interbed group Relative error absolute value The minimum true resistivity R of two single homogeneous layers t Finally, the formation resistivity of the middle target layer of the non-invasive ultra-thin interbed group is calculated by linear interpolation method.

2. The method for interpreting the middlemost target layer of the non-invasive ultra-thin interbedded formation model according to claim 1 is characterized by: The rules for reading the apparent resistivity of the three middle thin layers A, B, and C in step S1.1 are as follows: ① Apparent resistivity of the middle target layer When the apparent resistivity curve of the middle target layer B has a non-monotonic extreme value, the extreme value point is selected as the reading point, otherwise the midpoint of the formation is selected as the reading point; ② Apparent resistivity of the upper and lower thin adjacent layers The midpoint of the formation is selected as the reading point; In order to consider the influence of thin adjacent layers and thick surrounding rocks on the apparent resistivity of the middle target layer, the equivalent surrounding rock coefficient is introduced The calculation formula is:

3. The method for interpreting the middle target layer of the non-invasive ultra-thin interbedded formation model according to claim 1 is characterized by: The formation parameters of the middle single homogeneous layer in step S2.1 are designed as follows: ①Thickness H of the middle single homogeneous layer: To ensure the accuracy of thin layer thickness correction, the thickness range of the middle single homogeneous layer should be large enough and the value interval should be dense enough. The thickness should increase from small to large, and the value interval should follow the principle of increasing from dense to sparse. ② The true resistivity of the single homogeneous layer in the middle R t : The true resistivity value of the single homogeneous layer in the middle must be the same as the true resistivity value of the middlemost target layer in the non-invasive ultra-thin interbedded formation model designed in S1.1; In the traditional non-invasive three-layer single homogeneous formation model, the apparent resistivity R of resistivity logging is also numerically simulated by the finite element method. a , the simulation result of the middle point of the single homogeneous layer is selected as the apparent resistivity of the layer And establish the corresponding database.

4. The method for interpreting the middle target layer of the non-invasive ultra-thin interbedded formation model according to claim 1 is characterized by: In step S3, the data of stratigraphic models of all ultra-thin interbedded groups with the same best interpretation thickness are counted and it is found that: ①For each optimal interpretation thickness H be , the apparent resistivity of the middle target layer of all ultra-thin interbedded formation models Equivalent surrounding rock coefficient There is a good linear relationship. ②With the best interpretation thickness H be Increase, the apparent resistivity of the middle target layer Equivalent surrounding rock coefficient The linear fitting coefficient (slope) between the two curves also gradually increases, and the intercept varies in a larger range; ③ In the same middle target layer, the apparent resistivity Under the condition, the equivalent surrounding rock coefficient With the best interpretation thickness H be Increase and decrease rapidly; ④ When the best interpretation thickness H of the middle target layer of the ultra-thin interbed group is be When the total thickness of the ultra-thin interbed group is the same as that of the ultra-thin interbed group, it contains the largest number of ultra-thin interbed group models, and the apparent resistivity of the middle target layer is Equivalent surrounding rock coefficient The linear fitting segment of is the longest and has intersections with the linear fitting segments of other best explanation thicknesses; Based on the above four characteristics, the optimization criteria and determination method for the best interpreted thickness of the middle target layer of the non-intrusive ultra-thin interbed group can be established.

5. The method for interpreting the middlemost target layer of the non-invasive ultra-thin interbedded formation model according to claim 1 is characterized by: In step S4.1, the optimal interpretation thickness selection criteria for the middle target layer of the non-invasive ultra-thin interbed group are as follows: ① The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group is Substituting into all established apparent resistivity fitting equations, the best explanation of the thickness H be The corresponding calculation results of the apparent resistivity fitting equation The apparent resistivity of the middle target layer should be Relative error absolute value Minimum; ②Measure the apparent resistivity of the middle target layer of the non-invasive ultra-thin interbed group The best interpretation thickness H be The corresponding apparent resistivity variation range; ③ The equivalent surrounding rock coefficient of the middle target layer of the measured non-invasive ultra-thin interbed group The best interpretation thickness H be The corresponding equivalent surrounding rock coefficient is within the range of variation.

6. The method for interpreting the middlemost target layer of the non-invasive ultra-thin interbedded formation model according to claim 1, characterized in that: In the non-invasive ultra-thin interbedded formation model in step S1.1, the thickness of the upper and lower thick surrounding rock layers must be more than 5 times the length of the electrode distance of the resistivity logging instrument, which is 10m when modeling; the resistivity of the upper and lower thick surrounding rock R s and the wellbore mud resistivity R m Equal, and 1Ω.m is taken in modeling.

7. The method for interpreting the middlemost target layer of the non-invasive ultra-thin interbedded formation model according to claim 6 is characterized by: When designing a traditional non-invasive three-layer single homogeneous formation model, the true resistivity value and layer thickness of the upper and lower thick surrounding rocks should be the same as those of the upper and lower thick surrounding rocks when designing a non-invasive ultra-thin interbedded formation model.

8. The method for interpreting the middlemost target layer of a non-invasive ultra-thin interbedded formation model according to claim 2, characterized in that: Design the true resistivity values ​​R of the three thin layers A, B, and C in the middle of the non-invasive ultra-thin interbedded formation model t When considering factors such as repeated values ​​and symmetry, the number of models is appropriately reduced to improve modeling efficiency while covering most of the apparent resistivity variation range in the study area.

9. The method for interpreting the middlemost target layer of the non-invasive ultra-thin interbedded formation model according to claim 8, characterized in that: For the middle target layer B in the non-intrusive ultra-thin interbedded formation model, its heterogeneous surrounding rock includes both the upper and lower thick surrounding rocks and the upper and lower thin adjacent layers A and C that are adjacent to the middle target layer B. The equivalent surrounding rock coefficient of the middle target layer of the thin interbed group can be defined as It can also be defined as Through a large number of simulation studies, it is found that the upper and lower thin layers adjacent to the middle target layer B have a much greater impact on the apparent resistivity of the middle target layer than the thick surrounding rock. The equivalent surrounding rock coefficient is also better correlated with the apparent resistivity of the middlemost target layer.

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