Longitudinal zoning logging identification method for metamorphic rock buried hill reservoir

Abstract

The invention discloses a metamorphic rock buried hill reservoir longitudinal zoning logging identification method, which comprises the following steps: acquiring element logging, imaging logging and conventional logging information of sample wells at different construction positions in a research area, and making a single-well comprehensive histogram; dividing a metamorphic rock reservoir longitudinal structure unit of the sample well by utilizing fracture development characteristics and chemical alteration index longitudinal change characteristics; preferably selecting a well logging curve with an obvious distinguishing effect on each longitudinal structure unit, and constructing a fracture solution index calculation formula reflecting the fracture corrosion degree; the fracture-soluble index limit range of each longitudinal structure unit of the sample well is calibrated, and a metamorphic rock buried hill reservoir fracture-soluble index zoning model is established; and calculating a fracture-soluble index curve of the well section to be zoned by using a fracture-soluble index calculation formula, and carrying out buried hill longitudinal structure unit division according to the metamorphic rock buried hill reservoir fracture-soluble index zoning model. The method can accurately and quickly identify the longitudinal structure unit of the metamorphic rock buried hill reservoir, is simple to operate and high in precision, and is less influenced by human factors.

Description

Technical Field

[0001] The invention belongs to the technical field of well logging geology in the petroleum exploration industry, and in particular relates to a vertical zoning well logging identification method for metamorphic rock buried hill reservoirs. Background Art

[0002] Metamorphic buried-hill oil and gas reservoirs are less affected by burial depth, have a large distribution area, and have high production capacity. In recent years, the Bohai Bay Basin has made significant oil and gas exploration discoveries in the Archean metamorphic rock field, showing broad exploration prospects. Weathering and leaching are important control factors for the development of metamorphic buried-hill reservoirs, and are also an important factor in the vertical zoning of buried-hill reservoirs. Therefore, the study of the vertical zoning of metamorphic buried-hill reservoirs has important practical significance for reservoir formation mechanism and reservoir prediction.

[0003] There are currently two commonly used methods for dividing the vertical zoning of metamorphic rock buried hills. One is a qualitative division based on petrological data such as cores, wall cores, and thin sections. The other is a qualitative division method based on the morphological characteristics of deep lateral resistivity baselines and acoustic time difference curves.

[0004] The division based on petrological data means that due to the influence of weathering and leaching, the rocks near the top of the metamorphic buried hill are partially dissolved along the cracks, and the buried hill is divided into different structural units vertically according to the degree of weathering and transformation. However, due to the fact that the core and wall core data are recorded as discrete and discontinuous, and the division is based on the degree of dissolution and diagenetic phenomena of the core and wall core, it is mainly based on subjective judgment. This method often produces large errors and is difficult to compare between wells, which seriously restricts the application effect of this method.

[0005] The resistivity baseline method is to select several extreme points where the resistivity curve in the metamorphic buried hill reaches or approaches the highest value, and make a vertical line based on these resistivity extreme points. The position where the resistivity value first approaches or reaches the internal resistivity baseline is considered to be the location of the boundary between the weathering crust and the internal buried hill. The acoustic time difference curve morphology method refers to the position where the "straight low-amplitude micro-tooth" curve morphology first appears, and determines it as the location of the boundary between the weathering crust and the internal. The selection of the "resistivity baseline value" and the judgment of the "straight low-amplitude micro-tooth" acoustic time difference curve morphology in these two methods are highly subjective, which restricts the accuracy of the zoning results and is not suitable for fine zoning.

[0006] Patent CN112302623A discloses a method for dividing the weathering crust structure of granite buried hills based on logging data. This method constructs a structural division curve FJG parameter and intersects it with the deep lateral resistivity RD, establishes a quantitative discrimination standard for the weathering crust structure of granite, and divides the weathering crust of granite buried hills into weathered clay zone, weathered gravel zone, weathered fracture zone and bedrock fracture zone. This method avoids some subjective judgments and makes the results more objective. However, since the heterogeneity of metamorphic buried hill reservoirs is stronger than that of granite, the vertical zoning in the exploration practice of metamorphic buried hills needs to be more refined. The rock electrical characteristics of the two are quite different. The weathering crust structure judgment chart established by this method is not applicable to the vertical zoning of metamorphic buried hills.

[0007] Imaging logging has important applications in metamorphic buried-hill reservoir identification. It can identify the occurrence, density and aperture of fractures, distinguish various geological features such as caves, pores and fractures, and determine the fracture type and its effectiveness. It has the advantages of being intuitive and vertically continuous. Zoning buried-hills according to the vertical distribution characteristics of fractures is a feasible solution. However, due to the high cost of imaging operations, it is currently only carried out in newly drilled key exploratory wells.

[0008] The degree of weathering and leaching is an important reference indicator for buried hill zoning. Rocks undergo weathering and leaching, and minerals with poor weathering resistance are altered, which increases the degree of rock fragmentation and the opening of cracks. The chemical alteration index CIA is an important indicator that calculates the degree of weathering of feldspar minerals into clay minerals and reflects the degree of chemical weathering of rocks. Therefore, using elemental data to calculate the chemical alteration index CIA to evaluate the degree of rock weathering and leaching is an effective means of zoning buried hills.

[0009] Conventional logging is an essential item for buried-hill drilling. Imaging logging and element logging both have the advantage of vertical continuity. Therefore, combining conventional logging with element logging and imaging logging makes it possible to achieve accurate and efficient vertical zoning of metamorphic buried-hill reservoirs. Summary of the invention

[0010] The present invention is proposed to solve the problem of difficulty in vertical zoning of metamorphic buried hill in the prior art, and its purpose is to provide a vertical zoning logging identification method for metamorphic buried hill reservoir.

[0011] The present invention is achieved through the following technical solutions:

[0012] A method for vertical zoning logging identification of metamorphic buried hill reservoirs comprises the following steps:

[0013] (I) Collect element logging, imaging logging and conventional logging data from sample wells at different structural locations in the study area and produce a comprehensive histogram of a single well;

[0014] (II) Using the fracture development characteristics and the vertical variation characteristics of chemical alteration index to divide the metamorphic reservoir vertical zoning structural units of the sample wells;

[0015] (III) Selecting the logging curves with obvious effect of distinguishing each vertical structural unit and constructing the fracture dissolution index calculation formula reflecting the degree of fracture dissolution;

[0016] (IV) The fracture dissolution index boundaries of each vertical structural unit of the sample wells were calibrated using the box plot method to establish a fracture dissolution index zoning model for metamorphic buried hill reservoirs;

[0017] (V) Calculating the fracture dissolution index curve of the well section to be zoned using the fracture dissolution index calculation formula obtained in step (III), and dividing the buried hill vertical structural units based on the fracture dissolution index zoning model of the metamorphic rock buried hill reservoir established in step (IV).

[0018] In the above technical solution, the different structural positions in step (I) include structural high points, slope parts and low parts; the imaging logging data include but are not limited to the density P10 and opening FVA of the fracture; the conventional logging data include logging curves, and the logging curves include but are not limited to deep lateral resistivity curves, neutron curves, density curves and acoustic time difference curves.

[0019] In the above technical scheme, the fracture development characteristics in step (II) refer to taking the end position of the continuous fracture development section interpreted by the imaging logging in the vertical direction of the single well as the boundary position between the weakly weathered fracture zone and the bedrock fracture zone; the longitudinal change characteristics of the chemical alteration index refer to taking the end position of the downward decreasing trend of the chemical alteration index calculated using element data or the top interface of the relatively straight section as the boundary position between the strongly weathered fracture zone and the weakly weathered fracture zone; the longitudinal structural units of the metamorphic rock reservoir include the sandy gravel zone, the strongly weathered fracture zone, the weakly weathered fracture zone and the bedrock fracture zone.

[0020] In the above technical solution, the logging curves that have an obvious effect on distinguishing each vertical structural unit in step (III) include deep lateral resistivity curves, density curves and acoustic time difference curves.

[0021] In the above technical solution, the calculation formula of the slit dissolution index in step (III) is:

[0022] F r =DT / (SQRT(RD)*ZDEN),

[0023] In the formula, F r It represents the fracture dissolution index, which is dimensionless; DT represents the acoustic time difference, which is in μs / ft; RD represents the deep lateral resistivity, which is in Ω·m; ZDEN represents the density, which is in g / cm 3 .

[0024] In the above technical scheme, the fracture dissolution index zoning model of the metamorphic rock buried hill reservoir in step (IV) is specifically divided into: the well section with a fracture dissolution index Fr value below 1 is a bedrock fracture zone, the well section with a fracture dissolution index Fr value between 1 and 2.5 is a weakly weathered fracture zone, and the well section with a fracture dissolution index Fr value above 2.5 is a strongly weathered fracture zone and a sandy gravel zone.

[0025] The beneficial effects of the present invention are:

[0026] The invention provides a method for logging and identifying the vertical zoning of metamorphic buried-hill reservoirs, which can accurately and quickly identify the vertical structural units of Archean buried-hill reservoirs. Compared with the traditional method, a fracture dissolution index reflecting the degree of fracture dissolution is constructed. The parameter has a good correlation with the fracture aperture, and has an important characterization significance for the vertical weathering degree of the buried-hill reservoir. The method realizes the semi-quantitative division of the vertical zoning of the metamorphic buried-hill reservoir, has the advantages of simple operation, high precision, and less influence of human factors. The division of each vertical structural unit is more accurate and reliable, and the comparison between different well areas is more convenient and efficient, which provides a reliable basis for clarifying the formation mechanism of the weathering crust of the metamorphic buried-hill and reservoir prediction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the vertical zoning logging identification method of metamorphic rock buried hill reservoir of the present invention;

[0028] Figure 2 It is a diagram of the vertical zoning structural unit and its combination pattern of the metamorphic buried hill reservoir in the present invention;

[0029] Figure 3 It is a diagram showing the effect of conventional well logging curves in the present invention on distinguishing vertical structural units of metamorphic rock buried hills;

[0030] Figure 4 is a regression relationship diagram between the fracture dissolution index parameter and the fracture aperture constructed in the present invention;

[0031] Figure 5 It is a model diagram of the fracture dissolution index division of the vertical structural unit of the metamorphic rock buried hill reservoir in the present invention;

[0032] Figure 6 It is an implementation status diagram of an application example of the present invention.

[0033] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0035] Example 1

[0036] like Figure 1 As shown, a method for vertical zoning logging identification of metamorphic buried hill reservoirs includes the following steps:

[0037] (I) Collect element logging, imaging logging and conventional logging data from sample wells at different structural locations in the study area and produce a comprehensive histogram of a single well;

[0038] The different structural locations include structural high points, slope locations, and low locations;

[0039] The imaging logging data include but are not limited to the density P10 and the opening FVA of the fracture;

[0040] The logging curves include but are not limited to the deep lateral resistivity curve RD, the neutron curve CNCF, the density curve ZDEN and the acoustic time difference curve DT;

[0041] (II) Using the fracture development characteristics and the vertical variation characteristics of chemical alteration index to divide the metamorphic reservoir vertical zoning structural units of the sample wells;

[0042] The fracture development feature refers to taking the position where the continuous fracture development section interpreted by imaging logging in the vertical direction of a single well ends as the boundary position between the weakly weathered fracture zone and the bedrock fracture zone;

[0043] The vertical variation characteristics of the chemical alteration index refer to taking the end position of the downward decreasing trend of the chemical alteration index CIA calculated using element data or the top interface of the relatively straight section as the boundary position of the strong weathering fracture zone and the weak weathering fracture zone;

[0044] The longitudinal zoning structural units include a sandy gravel zone, a strongly weathered fracture zone, a weakly weathered fracture zone, and a bedrock fracture zone;

[0045] The continuous development section of the cracks includes a strong weathering crack zone and a weak weathering crack zone. The strong weathering crack zone has serious rock alteration and developed dissolution pores and cracks, and is mainly characterized by large crack density and crack opening. The weak weathering crack zone has weak rock alteration and local dissolution along the cracks, and is mainly characterized by reduced crack opening. The bedrock crack zone has relatively fresh rocks and poorly developed cracks, which are distributed in clusters and non-continuously.

[0046] The chemical alteration index CIA is calculated as follows: CIA = n(AL2O3) × 100 / [n(AL2O3) + n(CaO * )+n(Na2O)+n(K2O)], where n(AL2O3), n(CaO * ), n(Na2O) and n(K2O) represent AL2O3, CaO * , the molar fractions of Na2O and K2O, CaO *is the CaO in silicate, that is, the CaO in the whole rock minus the chemically deposited CaO; n(CaO * ) is calculated and corrected as follows: n(CaO * )=n(CaO)-(10 / 3×n(P2O5)), and if the corrected n(CaO * ) is less than n(Na2O), then the corrected n(CaO * ) as CaO * Otherwise, n(Na2O) is used as the mole fraction of CaO * The mole fraction of (cited from the literature: Liu Bing, Xu Bei, Meng Xiangying, Kou Xiaowei, He Jinyou, Wei Wei, Mi He. Study on the chemical alteration index of the Neoproterozoic strata of the Tarim Plate and its significance [J]. Acta Petrologica Sinica, 2007, 23(7): 1664-1670.). The calculation formulas for n(AL2O3), n(CaO), n(Na2O), n(K2O) and n(P2O5) are: n(AL2O3)=ω(AL) / (2×M(AL)), n(CaO)=ω(Ca) / M(Ca), n(Na2O)=ω(Na) / (2×M(Na)), n(K2O)=ω(K) / (2×M(K)), n(P2O5)=ω(P) / (2×M(P)), where ω(AL), ω(Ca), ω(Na), ω(K), ω(P) are the mass fractions of aluminum, calcium, sodium and potassium, respectively, in %; M(AL), M(Ca), M(Na), M(K), M(P) are the relative atomic masses of aluminum, calcium, sodium and potassium, respectively.

[0047] like Figure 2 As shown in the figure, the vertical zoning structural units of metamorphic buried-hill reservoirs include sandy gravel belt, strongly weathered fracture belt, weakly weathered fracture belt and bedrock fracture belt. There are five combination modes of vertical zoning of metamorphic buried-hill: type I, type II, type III, type IV and type V. The vertical structure of type I is sandy gravel belt + strongly weathered fracture belt + weakly weathered fracture belt + bedrock fracture belt; the vertical structure of type II is sandy gravel belt + weakly weathered fracture belt + bedrock fracture belt; the vertical structure of type III is strongly weathered fracture belt + weakly weathered fracture belt + bedrock fracture belt; the vertical structure of type IV is weakly weathered fracture belt + bedrock fracture belt; the vertical structure of type V is bedrock fracture belt;

[0048] (III) Selecting the logging curves with obvious effect of distinguishing each vertical structural unit and constructing the fracture dissolution index calculation formula reflecting the degree of fracture dissolution;

[0049] The effect of conventional logging curves on distinguishing the vertical structural units of metamorphic buried hills is shown in the figure below. Figure 3 As shown, from Figure 3It can be seen that the logging curves with obvious effect in distinguishing the vertical structural units of each metamorphic buried hill reservoir are the deep lateral resistivity curve RD, density curve ZDEN and acoustic time difference curve DT;

[0050] The fracture lysis index F r The calculation method is to divide the acoustic time difference DT by the product of the square root of the deep lateral resistivity RD and the density ZDEN, that is, the fracture dissolution index calculation formula is: r =DT / (SQRT(RD)*ZDEN), where F r It represents the fracture dissolution index, which is dimensionless; DT represents the acoustic time difference, which is in μs / ft; RD represents the deep lateral resistivity, which is in Ω·m; ZDEN represents the density, which is in g / cm 3 ;

[0051] from Figure 4 It can be seen from the regression relationship diagram between the fracture dissolution index parameter and the fracture aperture that the fracture dissolution index F r It has a good linear regression relationship with the crack opening FVA: F r =72.996*FVA+0.5, where FVA is the crack opening in mm, R 2 To evaluate F r The parameter related to FVA is a measure of the degree of fit of the regression equation in statistics, and is calculated using R 2 Indicates that R 2 =0.7272.

[0052] (IV) Calibrate the fracture dissolution index boundary range of each vertical structural unit of the sample well and establish a fracture dissolution index zoning model for metamorphic buried hill reservoirs;

[0053] like Figure 5 As shown in the figure, the semi-quantitative vertical zoning model of metamorphic rock buried hill reservoir based on the fracture dissolution index is specifically divided into: the fracture dissolution index of bedrock fracture zone is less than 1, 1≤; the fracture dissolution index of weakly weathered fracture zone is less than 2.5; and the fracture dissolution index of strongly weathered fracture zone is ≥2.5.

[0054] The complete metamorphic buried hill reservoir structure unit vertically includes: sandy gravel zone, strong weathering fracture zone, weak weathering fracture zone, bedrock fracture zone; the sandy gravel zone is the topmost unit of the metamorphic buried hill vertical zoning, and its rock structure is gravel-like, which is obviously different from the blocky structure of the buried hill bedrock, and can be easily identified through thin section logging, well wall coring and other data;

[0055] The well section with fracture dissolution index ≥ 2.5 includes a strongly weathered fracture zone and a sandy gravel zone. The box plot analysis of the present application method reveals that these two structural units cannot be distinguished ( Figure 5). However, the distinction between these two and the weakly weathered fracture zone can be achieved through the technical solution of this application; for the well section with fracture dissolution index ≥ 2.5, it is easy to distinguish the strongly weathered fracture zone from the sandy gravel zone through petrological data;

[0056] (V) Calculate the fracture dissolution index curve of the well section to be divided into zones using the fracture dissolution index formula obtained in step III, and divide the vertical structural units of the buried hill according to the fracture dissolution index zoning model of the metamorphic rock buried hill reservoir established in step IV.

[0057] The present invention is applied in well sections such as B19-6-B (3875-4466m), B19-6-D (4400-4766m), B19-6-J (4574-5500m), B19-6-M (4508-5079m), BZ26-6-A (3124-3291m), BZ26-6-D (3747-4053m), BZ26-6-B (3820-4479m), and BZ26-6-E (3755-4420m). The division results of the proposed semi-quantitative longitudinal zoning method for metamorphic buried-hill reservoirs are consistent with the division results of the buried-hill zoning based on comprehensive analysis methods such as imaging logging, element logging, and thin sections, with a 91% coincidence rate. The error is generally between 3 and 20m, thereby achieving good application effect and being worthy of popularization and application.

[0058] Application Examples

[0059] Taking the Archean strata at 3820-4479 m in Well BZ26-6-B as an example, Figure 6 As shown in the figure, it is difficult for the traditional method of vertical zoning of metamorphic buried hill reservoirs to accurately identify the buried hill structural units:

[0060] (1) According to the method that the resistivity value first approaches or reaches the inner resistivity baseline as the boundary between the weathering crust and the bedrock zone, it is judged that the top interface of the bedrock fracture zone is around 4250m ( Figure 6 as shown in lane 6);

[0061] (2) Based on the first appearance of the "straight low-amplitude micro-tooth-like" curve of the acoustic time difference as the boundary between the weathering crust and the bedrock zone, it is judged that the top interface of the bedrock fracture zone is around 4050 m ( Figure 6 as shown in lane 7);

[0062] (3) Application structure partition curve F JG The division is based on the weathering conglomerate zone above 4050m and the weathering fracture zone between 4050 and 4479m, which is inconsistent with the actual situation and fails to show a clear response to the boundary near 4250m. Figure 6 (shown in lane 13).

[0063] The method of the present application is used to construct a fracture dissolution index indicator curve that has important indicative significance for the degree of dissolution of metamorphic rock fractures, and semi-quantitative identification is performed based on a semi-quantitative vertical zoning model of metamorphic rock buried hill reservoirs based on the fracture dissolution index.

[0064] Figure 6 The 8th and 9th tracks from the left in the middle are the imaging logging fracture density and fracture aperture data, respectively. The unit of fracture density is bars / m, and the unit of fracture aperture is mm. According to the characteristics of imaging logging fracture density and aperture data, the continuous fracture development section is judged to be terminated at 4250m, which is the interface between the weakly weathered fracture zone and the bedrock fracture zone. It should be noted that the imaging logging data of the 4016-4049m well section is missing, the wellbore collapse is serious, and the acoustic time difference curve and deep lateral resistivity are in the same direction to the left, indicating that the rock in this section is broken and it is a continuous fracture development section.

[0065] Figure 6 The 10th track from the left in the middle is the chemical alteration index CIA calculated using element logging data. First, the element logging data is used to calculate,

[0066] n(AL2O3), n(CaO), n(Na2O), n(K2O) and n(P2O5), the calculation formula is:

[0067] n(AL2O3)=ω(AL) / (2×M(Al)),n(CaO)=ω(Ca) / M(Ca),n(Na2O)

[0068] =ω(Na) / (2×M(Na)),n(K2O)=ω(K) / (2×M(K)),n(P2O5)=ω(P) / (2×M(P)), where ω(Al), ω(Ca), ω(Na), ω(K), ω(P) are the mass fractions of aluminum, calcium, sodium, and potassium, respectively, in %; M(AL), M(Ca), M(Na), M(K), and M(P) are the relative atomic masses of aluminum, calcium, sodium, and potassium, respectively.

[0069] Then substitute the calculated result into the formula: CIA = n(AL2O3) × 100 / [n(AL2O3) + n(CaO * )+n(Na2O)+n(K2O)], where:

[0070] n(AL2O3), n(CaO * ), n(Na2O) and n(K2O) represent AL2O3, CaO * , Na2O and K2O molar fractions, in %, of which CaO * is the CaO in silicate, that is, the CaO in the whole rock minus the chemically deposited CaO; n(CaO * ) is calculated and corrected as follows: n(CaO* )=n(CaO)-(10 / 3×n(P2O5)), and if the corrected n(CaO * ) is less than n(Na2O), then the corrected n(CaO * ) as CaO * Otherwise, n(Na2O) is used as the mole fraction of CaO * The mole fraction of (Liu Bing et al., 2007).

[0071] Calculate the CIA at the corresponding depth using element logging data. Figure 5 There is an obvious interface around 4065m in the 10th CIA discrete curve. According to the end position of the downward decreasing trend of the chemical alteration index CIA, the boundary between the strong weathering fracture zone and the weak weathering fracture zone is taken as the boundary position, that is, 3820-4065m is designated as the strong weathering fracture zone.

[0072] In summary, using the characteristics of fracture development and the vertical variation of chemical alteration index, the vertical zoning of the Archean buried hill at 3820-4479m in Well BZ26-6-B is revealed as follows: 3820-4065m is divided into a strongly weathered fracture zone; 4065-4250m is divided into a weakly weathered fracture zone; and 4250-4479m is divided into a bedrock fracture zone.

[0073] Figure 6 The 12th track from the left is the calculated fracture dissolution index curve, and the 11th track is the result of the vertical zoning of the buried hill. First, the conventional logging curve is used to calculate the fracture dissolution index formula that reflects the degree of fracture dissolution. The fracture dissolution index calculation formula is the product of the acoustic time difference DT divided by the square root of the deep lateral resistivity RD and the density ZDEN, that is: F r =DT / (SQRT(RD)*ZDEN). Then, according to the semi-quantitative vertical zoning model of metamorphic buried-hill reservoirs based on fracture dissolution index, the fracture dissolution index of bedrock fracture zone is less than 1, 1≤fracture dissolution index of weakly weathered fracture zone is less than 2.5, and fracture dissolution index of strongly weathered fracture zone is greater than or equal to 2.5. The vertical zoning of Archaean in Well BZ26-6-B from 3820 to 4479 m is carried out, and the division results are as follows: 3820-4068 m is the strongly weathered fracture zone, 4068-4243 m is the weakly weathered fracture zone, and 4243-4479 m is the bedrock fracture zone. The above semi-quantitative vertical zoning method of metamorphic buried-hill reservoirs based on fracture dissolution index calculated by conventional logging curves is very consistent with the division results of buried-hill zoning based on imaging logging and element logging.

[0074] Design principle of the present invention:

[0075] The design principle of the present invention is to divide the interface based on the rock structure and dissolution differences of each vertical structural unit of the metamorphic rock buried hill by using the fracture development characteristics and the vertical change characteristics of the chemical alteration index; the well logging curve that is sensitive to the weathering karst response of the metamorphic rock is selected to construct a fracture dissolution index with important indicative significance for the fracture dissolution degree, so as to achieve quantitative characterization of the fracture dissolution degree of the metamorphic rock in the continuous well section; on this basis, the fracture dissolution index boundary range of each vertical structural unit is calibrated by the box plot method, and a fracture dissolution index zoning model of the metamorphic rock buried hill reservoir is established, so as to achieve semi-quantitative division of the vertical zoning of the metamorphic rock buried hill reservoir.

[0076] The present invention overcomes the problem that the vertical zoning of metamorphic rock buried hills lacks effective parameters and is difficult to quantitatively characterize. It innovatively constructs a derived parameter, the fracture dissolution index, which has important indicative significance for the degree of fracture dissolution. This parameter continuously and quantitatively reflects the difference in fracture dissolution of metamorphic rocks, greatly avoiding the interference of subjective factors in the zoning process, and can achieve the fine division of strong weathering fracture zones and weak weathering fracture zones, so that the objectivity and accuracy of the zoning results are greatly improved, and the problem that the weathering fracture zones are difficult to quantitatively and finely divide in the practice of metamorphic rock buried hill exploration is solved, and the vertical zoning of Bohai metamorphic rock buried hills is transformed from a single structure to a multi-component composite structure, and from qualitative to semi-quantitative. It has the advantages of simple operation, high precision, and less influence of human factors. The comparison between different well areas is more convenient and efficient, and has broad prospects for promotion and application.

[0077] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for vertical zoning logging identification of metamorphic buried hill reservoirs, characterized in that: The following steps are involved: (I) Collect element logging, imaging logging and conventional logging data from sample wells at different structural locations in the study area and produce a comprehensive histogram of a single well; (II) Using the fracture development characteristics and the vertical variation characteristics of chemical alteration index to divide the metamorphic reservoir vertical zoning structural units of the sample wells; (III) Select the logging curves that distinguish each vertical structural unit and construct a calculation formula for the fracture dissolution index that reflects the degree of fracture dissolution; (IV) Calibrate the fracture dissolution index boundary range of each vertical structural unit of the sample well and establish a fracture dissolution index zoning model for metamorphic buried hill reservoirs; (V) Calculating the fracture dissolution index curve of the well section to be zoned using the fracture dissolution index calculation formula obtained in step (III), and dividing the buried hill vertical structural units based on the fracture dissolution index zoning model of the metamorphic rock buried hill reservoir established in step (IV).

2. The method for vertical zoning logging and identification of metamorphic buried hill reservoirs according to claim 1 is characterized by: The different structural positions in step (I) include structural high points, slope parts and low parts; the imaging logging data include density and aperture of fractures.

3. The method for vertical zoning logging and identification of metamorphic buried hill reservoirs according to claim 1 is characterized by: The fracture development characteristics in step (II) refer to taking the end position of the continuous fracture development section interpreted by imaging logging in the vertical direction of a single well as the boundary position of the weakly weathered fracture zone and the bedrock fracture zone; the longitudinal change characteristics of the chemical alteration index refer to taking the end position of the downward decreasing trend of the chemical alteration index calculated using element data or the top interface of the relatively straight section as the boundary position of the strongly weathered fracture zone and the weakly weathered fracture zone; the longitudinal structural units of the metamorphic rock reservoir include a sandy gravel zone, a strongly weathered fracture zone, a weakly weathered fracture zone and a bedrock fracture zone.

4. The method for vertical zoning logging identification of metamorphic buried hill reservoir according to claim 1 is characterized by: The logging curves used to distinguish each vertical structural unit in step (III) include deep lateral resistivity curve, density curve and acoustic time difference curve.

5. The method for vertical zoning logging identification of metamorphic buried hill reservoir according to claim 1, characterized in that: The calculation formula of the slit dissolution index in step (III) is: F r =DT / (SQRT(RD)*ZDEN), In the formula, F r It represents the fracture dissolution index, which is dimensionless; DT represents the acoustic time difference, which is in μs / ft; RD represents the deep lateral resistivity, which is in Ω·m; ZDEN represents the density, which is in g / cm 3 .

6. The method for vertical zoning logging and identification of metamorphic buried hill reservoirs according to claim 1 is characterized by: The method for calibrating the limit range of the fracture dissolution index of each longitudinal structural unit of the sample well in step (IV) is the box plot method.

7. The method for vertical zoning logging and identification of metamorphic buried hill reservoirs according to claim 1 is characterized by: The metamorphic rock buried hill reservoir fracture dissolution index zoning model in step (IV) is specifically divided into: the fracture dissolution index Fr value below 1 is the bedrock fracture zone, the fracture dissolution index Fr value between 1 and 2.5 is the weakly weathered fracture zone, and the fracture dissolution index Fr value above 2.5 is the strongly weathered fracture zone and the sandy gravel zone.

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