Method for classifying weathering crust structure using well logging curves and petrological characteristics

Abstract

The present application relates to a method for dividing weathering crust structure by using well logging curve and petrology characteristics, comprising: identifying and obtaining the distribution range of weathering crust in width through seismic synthetic record; selecting multiple detection wells, and obtaining the well logging data of the multiple detection wells in vertical direction respectively; identifying and obtaining the porosity characteristics of the rock stratum of each detection well; identifying the mudstone layer and sandstone layer in the target layer section which are not affected by weathering as the reference for identifying the different structure layers of weathering crust, and determining the distribution range of weathering crust in vertical direction in each detection well; establishing the weathering crust mode in the distribution range of weathering crust in vertical direction in each detection well, and dividing the distribution range of weathering crust structure in the detection well according to the weathering crust mode; and obtaining the structure characteristics of the whole weathering crust. The method is fast, accurate and operable.

Description

Technical Field

[0001] The invention belongs to the technical field of geological exploration, and in particular relates to a method for dividing weathering crust structure by utilizing well logging curves and petrological characteristics. Background Art

[0002] Weathering crust refers to strata that were once exposed on the surface during geological history. After a period of weathering and erosion, distinct weathering and erosion zones were formed, followed by burial, compaction, and consolidation, a "shell" or "shell zone" was formed. Weathering crust is a product of the interaction between the lithosphere, biosphere, hydrosphere, and atmosphere. The study of weathering crust is of significance for mineral prospecting, research on natural environmental changes, soil formation and evolution, and land use. There are many types of weathering crust, among which clastic rock weathering crust can be divided into the vadose zone and the underflow zone from top to bottom.

[0003] The regional distribution of weathering crusts is primarily studied using seismic data. When weathering crusts develop on angular unconformities, they can be readily identified on seismic profiles based on the termination relationship of truncation reflections. When weathering crusts develop on pseudo-conformities, their identification requires a comprehensive approach. First, identification is based on the seismic reflection differences between the strata above and below the crust. Second, seismic tracking is used to extend the weathering crust identified in the angular unconformity area to the pseudo-conformity area for further identification. Once seismically identified, the regional development of the weathering crust is determined through seismic tracking closure. Identification of weathering crust structure is crucial for prospecting, studying natural environmental changes, soil development and evolution, and land use. However, the low vertical resolution of seismic tracking methods makes it challenging to identify the structure of clastic weathering crusts.

[0004] Chinese patent CN2013107386944 discloses a method for identifying the weathering crust structure of clastic rocks in areas without well coverage. The method includes: selecting a clastic rock outcrop and a coring section; obtaining outcrop samples and core samples, and calculating the weathering index of the outcrop sample and the weathering index of the core sample; comparing the weathering index of the outcrop sample with the weathering index of the core sample to determine the weathering crust structure of the core sample; establishing a clastic rock weathering crust structure identification template based on the logging curve corresponding to the coring section and the weathering crust structure of the core sample; applying the clastic rock weathering crust structure identification template to other wells to determine the planar distribution of different structural layers of the clastic rock weathering crust; drawing a seismic attribute plane map, fitting the seismic attribute plane map with the planar distribution of different structural layers of the clastic rock weathering crust, and determining the distribution of the weathering crust structure in the area without well coverage. This method solves the problem of identifying clastic rock weathering crust to a certain extent. However, it is very difficult to identify the weathering crust and its structure using conventional logging curves or logging curve identification weathering crust templates, and it has strong multi-solution characteristics. At the same time, due to the limitations of seismic resolution, it is also very difficult to use seismic attributes to fit the planar distribution of different structural layers of the weathering crust.

[0005] Therefore, based on these problems, a method for dividing weathering crust structure by using logging curves and petrology characteristics is provided, which is fast, accurate and operable, and has important practical significance. SUMMARY

[0006] The application provides a method for dividing weathering crust structure by using logging curves and petrology characteristics, which is fast, accurate and operable.

[0007] The application solves the technical problem by adopting the following technical scheme:

[0008] The method for dividing weathering crust structure by using logging curves and petrology characteristics comprises the following steps:

[0009] The distribution range of the weathering crust in the width direction is identified and obtained through a seismic synthetic record; a plurality of detection wells are selected in the obtained distribution range of the weathering crust, and logging data in the vertical direction of the plurality of detection wells is obtained respectively;

[0010] The porosity characteristics of the rock stratum of each detection well are identified and obtained by using a logging curve multi-parameter intersection identification method;

[0011] The mudstone layer and the sandstone layer which are not affected by weathering are identified in the target layer section according to the obtained porosity characteristics of the rock stratum of each detection well, and are used as a reference for identifying different structural layers of the weathering crust, so as to determine the distribution range of the weathering crust in the vertical direction in each detection well;

[0012] The weathering crust mode is established according to the porosity characteristics of the rock stratum in the distribution range of the weathering crust in the vertical direction in each detection well, and the distribution range of the weathering crust structure in the detection well is divided according to the weathering crust mode;

[0013] The structural characteristics of the entire weathering crust are obtained according to the distribution range of the weathering crust structure in the plurality of detection wells.

[0014] Further, the porosity characteristics of the rock stratum include lithology change characteristics and porosity change characteristics.

[0015] Further, the weathering crust mode is established according to the following rules: the weathering crust seepage section is defined as the section where the porosity is increased compared with the original stratum, and the core has dissolution phenomenon and weathering leaching phenomenon; and the weathering crust underflow section is defined as the section where the porosity is reduced compared with the original stratum, and the core cementation is developed.

[0016] Further, in the establishment rule of the weathering crust mode, the weathering crust seepage section is defined as the section where the porosity is increased compared with the original stratum, and the core has at least one of the following characteristics in addition to the dissolution phenomenon and the weathering leaching phenomenon observed under a microscope: clay membrane, striped birefringence fabric, overhanging calcite, and iron membrane.

[0017] Further, the weathering crust mode is established by the following rules: in comparison with the original stratum, the porosity is reduced, and in addition to the development of cementation found by core microscopic observation, at least one of the following characteristics is defined as the weathering crust vadose section: filling pore calcite, floating grain structure, euhedral calcite, and broken or edge-eroded pseudo-hexagonal sheet of detrital kaolinite.

[0018] Further, the method for obtaining the structural characteristics of the entire weathering crust according to the distribution range of the weathering crust structure in the multiple detection wells is as follows: fitting the weathering crust vadose section in the multiple detection wells into a weathering crust vadose zone by using a fitting algorithm, and fitting the weathering crust vadose section in the multiple detection wells into a weathering crust vadose zone, so that the weathering crust vadose zone and the weathering crust vadose zone together constitute the structural characteristics of the entire weathering crust.

[0019] Further, the logging data of the detection well in the vertical direction is a logging curve diagram drawn by using natural gamma logging, resistivity logging, acoustic logging, neutron logging, and density logging parameters.

[0020] In the development process of the weathering crust, the existence of dissolution and cementation will form a vadose zone with good porosity and a vadose zone with poor porosity, so that the distribution range of the vadose zone and the vadose zone can be determined by analyzing the numerical characteristics of the logging porosity near the unconformity surface. Generally, the porosity of the vadose zone sandstone reservoir is higher than that of the sandstone in the lower original stratum, while the porosity of the vadose zone sandstone reservoir is lower than that of the sandstone in the lower original stratum and the permeability. The porosity has good sensitivity to the identification of the weathering crust and its structure, so the present application identifies the weathering crust structure according to the porosity and its change characteristics obtained by the intersection calculation of the logging curve and the rock characteristics under the microscope, so that the present application has the characteristics of sufficient basis, high reliability, and easy operation. The petrological sign of the weathering crust vadose zone: in addition to the development of a large number of dissolution pores, one or more of the following leaching characteristics will appear in the slice observation: clay membrane, striped birefringence fabric, overhanging calcite, and iron membrane. The petrological sign of the weathering crust vadose zone: in addition to the strong carbonate cementation, one or more of the following leaching characteristics will appear in the slice observation: filling pore calcite, floating grain structure, euhedral calcite, and broken or edge-eroded pseudo-hexagonal sheet of detrital kaolinite.

[0021] Meanwhile, in the aspect of predicting the planar distribution of the weathering crust structure, the weathering crust structure mode is taken as the research object, and the stratum thickness corresponding to the weathering crust structure mode is larger than that corresponding to a single weathering structure, which makes the weathering crust structure mode match the seismic characteristics (seismic attributes) better than the weathering crust structure layer matches the seismic characteristics (seismic attributes), so as to improve the prediction accuracy.

[0022] Therefore, the present invention first uses the logging curves and petrological characteristics of a single well to determine the development range of the weathering crust in the well in terms of vertical thickness; secondly, multiple well-connected profiles and seismic profiles are used to determine the pinch-out boundary of the weathering crust in the area, that is, where its lateral thickness disappears; finally, the vertical and lateral development range of the weathering crust in the study area is determined.

[0023] The advantages and positive effects of the present invention are:

[0024] The method of dividing the weathering crust structure by utilizing logging curves in combination with petrological characteristics can accurately determine the distribution range of the seepage zone and the underflow zone by analyzing and comparing the change characteristics of porosity and petrology. The method is fast, accurate and highly operable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0026] Figure 1 A buried hill distribution map of the Huanghua Depression provided by an embodiment of the present invention;

[0027] Figure 2 The embodiment of the present invention provides Figure 1 Comprehensive histogram of Well Kou-24 in the Zhongkou Village buried hill;

[0028] Figure 3 The embodiment of the present invention provides Figure 1 Comprehensive histogram of Well Kou-23 in the Zhongkou Village buried hill;

[0029] Figure 4 The embodiment of the present invention provides Figure 2 、 Figure 3 The third column "lithology" uses different combinations of boxes, points, lines, and circles to represent the corresponding relationship diagrams of different lithologies;

[0030] Figure 5 A weathering crust seepage zone formed by fitting multiple seepage fitting curves provided in an embodiment of the present invention;

[0031] Figure 1 Among them, 1 represents Kou Village Buried Hill Kou 24 Well, 2 represents Kou Village Buried Hill Kou 23 Well; Figure 2 、 Figure 3 The symbols are explained as follows: Gr gamma curve, unit API; CALI wellbore curve, unit cm; SP natural potential, unit mV; RESIS resistivity, unit Ω·m; DT acoustic time difference, unit μs / m. DETAILED DESCRIPTION

[0032] First of all, it should be noted that the specific structure, characteristics and advantages of the present invention will be specifically described below in an exemplary manner. However, all descriptions are only used for illustration and should not be understood as limiting the present invention. In addition, any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature displayed or implied in the drawings, can still be combined or deleted between these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned herein. In addition, in order to simplify the drawings, the same or similar technical features may be marked in only one place in the same drawing.

[0033] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0034] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0035] The method provided in this embodiment for dividing weathering crust structure using well logging curves and petrological characteristics includes the following steps:

[0036] Through seismic synthetic records, the distribution range of the weathering crust is identified and obtained. Within the obtained weathering crust distribution range, multiple detection wells are selected and vertical logging data are obtained for each of the multiple detection wells. It should be noted that when selecting detection wells, they need to be evenly distributed within the obtained weathering crust distribution range, and the selected wells must have data such as sonic logging, lateral resistivity logging, and natural gamma logging. The selected wells must also have core thin sections or thin section data of the weathered well section and the adjacent normal well section, supplemented by scanning electron microscopy data.

[0037] The multi-parameter intersection identification method of logging curves is used to identify and obtain the porosity characteristics of the rock formation in each detection well;

[0038] Based on the porosity characteristics of the rock formations obtained in each detection well, mudstone and sandstone layers unaffected by weathering are identified in the target interval. These layers serve as a reference for identifying different structural layers of the weathering crust and determining the vertical distribution of the weathering crust in each detection well.

[0039] In each detection well, within the vertical distribution range of the weathering crust, a weathering crust model is established according to the porosity characteristics of the rock formation, and the distribution range of the weathering crust structure in the detection well is divided according to the weathering crust model;

[0040] The structural characteristics of the entire weathering crust are obtained based on the distribution amplitude of the weathering crust structure in multiple detection wells.

[0041] It should be pointed out that the porosity characteristics of the rock formation include lithology variation characteristics and porosity variation characteristics.

[0042] The weathering crust model is established according to the following rules: a weathering crust seepage section is defined as a section with increased porosity compared to the original formation and core evidence of dissolution and weathering leaching; a weathering crust underflow section is defined as a section with decreased porosity compared to the original formation and developed cementation. Furthermore, the weathering crust model establishment rules may include the following: a section with increased porosity compared to the original formation and microscopic observation of core evidence of dissolution and weathering leaching, in addition to at least one of the following characteristics: clay film, striated birefringent texture, pendulous calcite, or iron film. A section with decreased porosity compared to the original formation and microscopic observation of core evidence of developed cementation, in addition to at least one of the following characteristics, is defined as a section with at least one of the following characteristics: pore-filling spar calcite, a floating granular structure, euhedral calcite, or fragmented kaolinite or pseudohexagonal flakes with abraded edges.

[0043] The method for obtaining the structural characteristics of the entire weathering crust based on the distribution amplitude of the weathering crust structure in multiple detection wells is: using a fitting algorithm to fit the weathering crust seepage section in multiple detection wells into the weathering crust seepage zone, and to fit the weathering crust underflow section in multiple detection wells into the weathering crust underflow zone. The weathering crust seepage zone and the weathering crust underflow zone together constitute the structural characteristics of the entire weathering crust.

[0044] The vertical logging data of the detection well is a logging curve diagram drawn using natural gamma logging, resistivity logging, sonic logging, neutron logging, and density logging parameters.

[0045] As an example, in this embodiment, taking the Dagang exploration area as an example, the weathering crust structural characteristics are divided to guide the prediction of clastic rock weathering crust reservoirs in the uncored well area. The acquisition of weathering crust structural characteristics includes the following steps:

[0046] S1. Identify the distribution range of weathering crust through seismic composite records;

[0047] like Figure 1As shown, the Mesozoic-Paleozoic clastic weathering crust is widely distributed throughout the Dagang exploration area and has become a key buried-hill oil-bearing interval in the area. Industrial oil and gas flows have been obtained from the Shihezi Formation clastic weathering crust reservoirs in several wells, and high-yield oil and gas flows have been obtained from the Jurassic in several wells, all with reported reserves. However, systematic research on the structure and performance of this reservoir has not yet been conducted. To establish a cross-sectional structural model for the clastic weathering crust and confirm its petroleum geological importance, it is urgently necessary to conduct research on the weathering degree and history, cross-sectional structure and characteristics, reservoir space type and characteristics, and the main controlling factors of reservoir performance in key buried-hill reservoirs, thereby guiding the prediction of clastic weathering crust reservoirs in uncored well areas.

[0048] It should be noted that Figure 1 There are 30 buried hill structures of various types, with a trap area of ​​1000km 2 The buried hill is large in scale and has great exploration potential. The largest single buried hill area is 108km 2 ;

[0049] S2. Within the distribution range of the weathering crust obtained in step S1, multiple detection wells are selected. The selection criteria for the detection wells are wells that have drilled into the weathering crust and have logging data. The selected wells are distributed as evenly as possible in the study area, and vertical logging data of the detection wells are obtained. The logging data is a logging curve diagram drawn using natural gamma logging, resistivity logging, sonic logging, neutron logging, and density logging parameters; wherein, Figure 2 yes Figure 1 Comprehensive histogram of Zhongkou 24 well; Figure 3 yes Figure 1 Comprehensive histogram of Zhongkou 23 well; Figure 4 Yes Figure 2 、 Figure 3 The third column "lithology" uses different combinations of boxes, points, lines, and circles to represent the corresponding relationship diagrams of different lithologies;

[0050] S3. Using a multi-parameter intersection identification method for well logging curves, identify the porosity characteristics of the rock formation in each detection well. The identified porosity characteristics include lithologic variation characteristics described by a natural gamma-resistivity intersection diagram, and porosity variation characteristics described by an acoustic-neutron intersection diagram and a density-neutron intersection diagram;

[0051] Through Figure 2The porosity characteristics and lithologic variation characteristics of the well can be obtained through analysis, and the well can be divided into the following intervals: 1828-1602 m, with an average porosity of 5-8%, and a maximum porosity of 18% in local sand bodies; 1602-1577 m, with an average porosity of 7%, and only one thin layer of sandstone with good porosity, 2.5 m thick, and mainly dense sandstone with a high mud content; under the microscope, kaolinite crushing or edge erosion can be observed; 1577-1544 m, with a maximum porosity of 17% and an average porosity of 9-11%, and three sets of rock layers with good porosity are developed in the interval; under the microscope, kaolinite covering skeleton particles and clay shells can be observed in clay minerals;

[0052] Through Figure 3 The porosity characteristics and lithologic variation characteristics of the well can be obtained through analysis, and the well can be divided into the following intervals: 215.4-1960.5m, average porosity 6-10%, with the maximum porosity in the interval reaching 15% in local sand bodies; 1960.5-1940m, average porosity 6%, the interval is dominated by sandstone with a high argillaceous content, and the sandstone thickness is large, 20.5m; 1940-1891.1m, maximum porosity 15%, average porosity 9-12%; three sets of rock layers with good porosity are developed in the interval, and extremely large dissolution pores can be observed under the microscope;

[0053] S4. Based on the lithologic and porosity variation characteristics of each detection well obtained in step S3, mudstone and sandstone layers unaffected by weathering are identified in the target layer interval as a reference for identifying different structural layers of the weathering crust, and the vertical distribution range of the weathering crust in each detection well is determined;

[0054] like Figure 2 As can be seen from the comprehensive histogram of Well Kou 24, in the 1828-1602m interval, although the maximum porosity in the section can reach 18% in local sand bodies, the average porosity is lower by 5-8%; this section is the original formation section of Well Kou 24.

[0055] The unweathered strata above and below the unconformity can be broadly referred to as the original strata. The original strata we're referring to here are the unweathered strata below the weathering crust. The strata within the weathering crust are similar in origin and essentially the same age as the original strata below the weathering crust, so they can be compared. The original strata above the weathering crust, on the other hand, have no connection to the weathering crust and are outside the scope of this invention. This invention uses seismic interface identification and time-depth conversion to locate the depth of weathering crust development and identifies the weathering crust structure based on porosity variations. The strata with fine porosity within the weathering crust are called the vadose zone (fine porosity, up to 15%). The strata below it where the porosity decreases are called the underflow zone, where the porosity then increases again, entering the original strata. The thickness of the weathering crust generally does not exceed 200 m. This step comprehensively considers all of the above factors as the basis for identifying the vadose zone and underflow zone of the weathering crust.

[0056] like Figure 3 ,It can be seen from the comprehensive histogram of Kou 23 well that in the 215.4~1960.5 layer section, the maximum porosity in the section can reach 15% in the local sand body, and the average porosity is 6~10%. This layer section is the original formation section of Kou 23 well.

[0057] S5. In each detection well, a weathering crust model is established within the vertical distribution range of the weathering crust according to the variation characteristics of porosity and petrology, and the distribution range of the weathering crust structure in the detection well is divided according to the weathering crust model; the weathering crust model is established according to the following rules: compared with the original formation, the porosity increases and the core microscopic observation shows dissolution and weathering leaching phenomena, which is defined as the weathering crust seepage section; compared with the original formation, the porosity decreases and the core microscopic observation shows developed cementation, which is defined as the weathering crust underflow section.

[0058] Furthermore, as a further improvement to the present invention, in the aforementioned weathering crust model establishment rules, a weathering crust vadose zone is defined as one in which the porosity increases compared to the original formation and, in addition to dissolution and weathering leaching, core microscopic observation reveals at least one of the following characteristics: clay film, striped birefringent structures, pendulous calcite, and iron film. Clay film forms when extremely low groundwater levels or insufficient infiltration prevent clay-rich water from reaching the water table, resulting in the accumulation of mechanically percolating clay carried by the water body in the vadose zone. This forms a thin film of clay minerals surrounding particles; striped birefringent structures are commonly seen in soils that have undergone expansion, contraction, and freezing; pendulous calcite forms when seepage water, flowing vertically downward, forms droplets under the action of gravity beneath particles, precipitating when calcium carbonate is supersaturated; and the formation of iron film is associated with the weathering of silicate minerals such as biotite. Biotite weathering can form iron-rich clay minerals.

[0059] As a further improvement of the present invention, in the rules for establishing the weathering crust model, if the porosity is reduced compared to the original formation and at least one of the following characteristics is found in addition to the development of cementation under core microscope observation, it is defined as a weathering crust underflow section: pore-filling spar calcite, floating granular structure, euhedral calcite, and kaolinite fragments that are broken or pseudo-hexagonal sheets with abraded edges. During this period, pore-filling spar calcite is formed in the underflow zone; the floating granular structure is because the calcite crystals are large and encapsulate one or more clastic particles. Calcite with this structure is generally formed in the underflow zone; more euhedral rhombohedral calcite is formed in the reservoir. Underflow can serve as a boundary marker between the vadose zone and the underflow zone. The development of stalactite-like, branched, or irregular dark halos in mudstone is related to groundwater underflow and is formed near the water table.

[0060] Through Figure 2 From the analysis, we can see that Figure 2 The 1602-1577m interval has an average porosity as low as 7%, while the original formation has an average porosity of 5-8%. Compared with the original formation, the porosity is reduced. Combined with microscopic observation of the core of this interval, it is found that the core is mainly dense sandstone with a high mud content. There is only one layer of sandstone with good porosity, which is only 2.5m thick. Under the microscope, it can be observed that the kaolinite is broken or the edges are abraded. It can be determined that this interval is a weathering crust undercurrent section. Figure 2 The 1577-1544m layer has a maximum porosity of 17% and an average porosity of 9-11%, which is significantly higher than the average porosity of 5-8% in the original formation section; three sets of rock layers with good porosity are developed in this section. Under the microscope, the core of this section can be observed to contain kaolinite in the clay minerals covering the skeleton particles and clay shells, which can be judged as the weathering crust seepage section.

[0061] Through Figure 3 From the analysis, we can see that Figure 3 The 1960.5-1940m interval has an average porosity of 6%, which is lower than the 6-10% average porosity of the original formation. Microscopic observation of the core of this interval revealed that it is mainly composed of sandstone with a high mud content. The sandstone is relatively thick, reaching 20.5m. This section can be judged as a weathering crust undercurrent section. Figure 3 The 1940-1891.1m layer section has a maximum porosity of 15% and an average porosity of 9-12%, which is significantly higher than the average porosity of 6-10% in the original formation. Three sets of rock layers with good porosity are developed in this section. When the core of this layer is observed under a microscope, extremely large dissolution pores can be observed, which can be judged as a weathering crust seepage section.

[0062] By repeating this process, the original stratigraphic section, weathering crust underflow section, and weathering crust seepage section of all detection wells can be identified.

[0063] S6. Describe the structure of the weathering crust based on the distribution amplitude of the weathering crust structure in multiple detection wells within the same weathering crust distribution range. In this embodiment, a fitting algorithm is used to fit the weathering crust seepage sections in multiple detection wells into the weathering crust seepage zones, and the weathering crust underflow sections in multiple detection wells into the weathering crust underflow zones. The weathering crust seepage zones and the weathering crust underflow zones together constitute the weathering crust structural characteristics.

[0064] Specifically, you can Figure 1 Multiple longitudinal sections are set within the distribution range of the weathering crust shown in FIG. First, the weathering crust undercurrent zones in different detection wells in the same section are fitted into undercurrent fitting curves representing the profile line of the weathering crust undercurrent zone in combination with the petrological characteristics, and the weathering crust seepage section is fitted into the seepage fitting curve representing the profile line of the weathering crust seepage zone. Then, multiple undercurrent fitting curves are fitted into the weathering crust undercurrent zone, and multiple seepage fitting curves are fitted into the following figure. Figure 5 The vadose zone of the weathering crust is shown.

[0065] The above embodiments describe the present invention in detail, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for dividing weathering crust structure using well logging curves and petrological characteristics, characterized by: The steps include: Through synthetic seismic records, the distribution range of the weathering crust is identified and obtained; within the obtained distribution range of the weathering crust, multiple detection wells are selected to obtain vertical logging data for each of the multiple detection wells; The multi-parameter intersection identification method of logging curves is used to identify and obtain the porosity characteristics of the rock formation in each detection well; Based on the porosity characteristics of the rock formations obtained in each detection well, mudstone and sandstone layers unaffected by weathering are identified in the target interval. These layers serve as a reference for identifying different structural layers of the weathering crust and determining the vertical distribution of the weathering crust in each detection well. In each detection well, within the vertical distribution range of the weathering crust, a weathering crust model is established according to the porosity characteristics of the rock formation, and the distribution range of the weathering crust structure in the detection well is divided according to the weathering crust model; Obtain the structural characteristics of the entire weathering crust based on the distribution amplitude of the weathering crust structure in multiple detection wells; In the establishment rules of the weathering crust model, the weathering crust seepage section is defined as a section with increased porosity compared to the original formation and at least one of the following characteristics in addition to dissolution and weathering leaching observed under a core microscope: clay film, striped birefringence structure, pendulous calcite, and iron film; In the rules for establishing the weathering crust model, a weathering crust undercurrent section is defined as one in which the porosity is reduced compared to the original stratum and, in addition to the well-developed cementation observed under a core microscope, at least one of the following characteristics is present: pore-filling spar calcite, floating granular structure, euhedral calcite, and kaolinite fragments that are broken or pseudo-hexagonal with eroded edges.

2. The method for classifying weathering crust structure using well logging curves and petrological characteristics according to claim 1, characterized in that: The porosity characteristics of the rock formation include lithology variation characteristics and porosity variation characteristics.

3. The method for classifying weathering crust structure using well logging curves and petrological characteristics according to claim 1, characterized in that: The method for obtaining the structural characteristics of the entire weathering crust based on the distribution amplitude of the weathering crust structure in multiple detection wells is: using a fitting algorithm to fit the weathering crust seepage section in multiple detection wells into the weathering crust seepage zone, and to fit the weathering crust underflow section in multiple detection wells into the weathering crust underflow zone. The weathering crust seepage zone and the weathering crust underflow zone together constitute the structural characteristics of the entire weathering crust.

4. The method for classifying weathering crust structure using well logging curves and petrological characteristics according to claim 1, characterized in that: The vertical logging data of the detection well is a logging curve diagram drawn using natural gamma logging, resistivity logging, sonic logging, neutron logging, and density logging parameters.

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