Evaluation method for estimating the size of karst cave body in fractured-vuggy carbonate reservoirs using the width of fracture zone

Abstract

The application discloses an evaluation method for estimating the size of a karst fracture-cave carbonate reservoir cave body by using a broken zone width, and relates to the technical field of oil and gas field exploration and development. The application uses outcrop data of a research area as the core of fine characterization of fracture-cave body size research, dissects the internal structure and formation mechanism of the fracture-cave body, establishes the correlation between the broken zone and the cave body, calculates the height of the cave body, thereby determining the height of the fracture-cave body, establishes the correlation between the seismic fracture-cave sculpture body and the height of the fracture-cave body, determines the correction coefficient or correction formula of the seismic fracture-cave sculpture body, corrects the seismic fracture-cave sculpture body, and finally accurately depicts the position, scale and spatial distribution of the fracture-cave body, thereby providing a geological basis for efficient exploration and development of the fracture-cave type carbonate rock oil and gas reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field exploration and development technology, and more specifically to an evaluation method for estimating the main body size of karst caves in karst fractured carbonate reservoirs using the width of fractured zones. Background Technology

[0002] Carbonate rock oil and gas reservoirs occupy an important position in the world, accounting for about 50% of the world's total oil and gas reserves and more than 60% of the world's total oil and gas production. They are one of the most important exploration and development areas in my country's energy strategic layout.

[0003] Fracture-vuggy carbonate oil and gas reservoirs are the main type of carbonate oil and gas reservoirs. They are characterized by large differences in pore-fracture-vuggy scale, complex structure, and diverse reservoir types (porosity type, cave type, fracture type, fracture-pore type, fracture-vuggy type, and fracture-vuggy type). Different types of reservoirs vary greatly in development location, scale, and distribution characteristics, have poor reservoir continuity, change rapidly, are extremely heterogeneous, and have complex seismic response characteristics.

[0004] Among them, caves formed by buried mountain karst or interlayer karst are affected by the long-term erosion of open and hidden river bodies, resulting in caves of enormous scale, reaching heights of over 600 meters, forming sinkholes that can stretch for several kilometers or even tens of kilometers in length. When drilling encounters such karst fissures, severe leakage or depletion occurs, making drilling difficult to continue, prematurely ending the drilling operation, and preventing logging. Therefore, it is very difficult to completely drill through large buried mountain karst fissures or interlayer karst fissures to determine their scale.

[0005] Research shows that buried karst fissure caves or interlayer karst fissure caves are subjected to overlying pressure, and the strata above and around the caves will form fracture zones under stress. Therefore, we divide buried karst fissure caves or interlayer karst fissure caves into three zones: the cave body, the fracture zone, and the surrounding rock. The surrounding rock is relatively dense with few fractures, mainly consisting of bioclastic limestone and dolomitic limestone. It is formed by the dissolution and expansion of bioclastic and dolomitic crystal pores, mostly elliptical or irregularly circular, with a pore diameter of 2-10 mm, and a maximum of 10 cm. It is distributed in clumps, layers or bands in the plane. Drilling generally does not result in leakage or only a small amount of leakage, which has little impact on drilling. The fracture zone is affected by multiple phases of tectonic operation, resulting in multiple phases of cave roof collapse fracture zone. Under the action of groundwater, the fracture zone dissolves along the fractures to form small-scale dissolution pores. Drilling is prone to leakage, but it can generally be drilled smoothly. The main body of the cave is mainly partially filled or unfilled. The height of the main body of the cave exceeds 3 m and the width exceeds 6 m. When drilling encounters the main body of the cave, serious leakage or emptying is likely to occur, and drilling cannot continue and will be completed prematurely. Comprehensive analysis shows that when drilling encounters buried hill karst fissures or interlayer karst fissures, it is generally possible to completely drill through the surrounding rock and fractured zones of these karst fissures or interlayer karst fissures. However, it is difficult to completely drill through the main body of the karst cave. The size of the main body of the karst cave determines the scale of the contained space, which is crucial for oil and gas reservoir exploration and development. Technical research has not yet yielded a method for estimating the size of the main body of the karst cave.

[0006] Fractured-vuggy carbonate reservoirs are prone to leakage or depletion, and premature drilling without logging data makes it impossible to directly determine the size of the fractured-vuggy bodies. Accurately determining the size of fractured-vuggy bodies presents several challenges:

[0007] (1) The karst fissures and caves in the buried hills or the karst fissures and caves between layers are well-developed and have complex internal structures;

[0008] (2) Drilling is prone to leakage or venting, premature completion of drilling, lack of logging data, limited data on fracture and cavity characterization, and low accuracy;

[0009] (3) The size of the fracture cavity is mainly determined by the seismic fracture cavity carving technology. However, due to the influence of the quality and accuracy of seismic data, the results of the fracture cavity carving are difficult to meet the needs of exploration and development.

[0010] Currently, there is no precise method for determining the size of fractured caves, especially the size of the main body of the cave. There is an urgent need for an evaluation method for the size of the main body of caves in karst fractured carbonate reservoirs to improve the accuracy of fractured cave characterization. Summary of the Invention

[0011] To overcome the defects and shortcomings of the existing technology, this invention provides an evaluation method for estimating the size of the main body of karst fracture-vuggy carbonate reservoirs using the width of the fracture zone. The purpose of this invention is to provide an evaluation method for the size of the main body of karst fracture-vuggy carbonate reservoirs, thereby improving the accuracy of fracture-vuggy body characterization. Studies have shown that karst caves formed by buried hill karst or interlayer karst are subjected to overlying strata pressure. Under stress, the strata above and around the caves form fracture zones, and the width of the fracture zone has a certain positive correlation with the size of the main body of the cave. This invention utilizes outcrop data from the study area to draw a cross-plot of the fracture zone width and the main body height of the cave, establishes a formula for the relationship between the fracture zone width and the main body height of the cave, and uses well logging data for detailed interpretation to accurately determine the width of the fracture zone. Finally, using a fitting formula, the height of the main body of the cave is calculated, thus determining the size of the main body of the cave.

[0012] Fractured-vuggy carbonate reservoirs are the most prevalent type of carbonate reservoir. Quantitative characterization of fractured-vuggy carbonate reservoirs is crucial for the efficient exploration and development of such reservoirs. Determining the size of fractures and cavities, especially the size of the main cavern, is an important parameter for estimating the reserves of fractured-vuggy carbonate reservoirs and for formulating oil and gas development strategies. Therefore, accurately determining the size of fractures and cavities using this method is one of the key technologies for the efficient exploration and development of fractured-vuggy carbonate reservoirs, and it has significant market demand and broad application prospects.

[0013] To address the problems existing in the prior art, the present invention is achieved through the following technical solution.

[0014] This invention provides an evaluation method for estimating the main body size of karst caves in karst fracture-vuggy carbonate reservoirs using the width of fractured zones. The method includes the following steps:

[0015] S1. Steps for describing fissures and caves in the field: Locate outcrops of fissures and caves formed under the same conditions as those in the study area and conduct field reconnaissance; Measure the size of the main body of the fissure and cave and the width of the fracture zone of the fissure and cave.

[0016] S2. Fitting the calculation formula for the main body of the karst cave: Using the size of the main body of the karst cave and the width of the fracture zone of the karst cave obtained from step S1, establish the intersection diagram of the size of the main body of the karst cave and the width of the fracture zone, and fit the calculation formula for the height of the main body of the karst cave and the width of the fracture zone.

[0017] S3. Steps for determining the width of the fracture zone in the study area: Using the logging data of the study area, the top and bottom depths of drilling anomalies in the fracture zone during drilling are statistically analyzed; then, the top and bottom depths of the fracture zone are precisely interpreted using the measurement data of the study area to determine the location and width of the fracture zone in a single fracture zone.

[0018] S4. Estimate the height of the main body of the karst cave in the study area. Use the calculation formula for the height of the main body of the karst cave and the width of the fracture zone obtained by fitting the formula obtained by step S2, and the width of the fracture zone in a single karst cave obtained by step S3, to calculate the height of the main body of the karst cave in a single karst cave.

[0019] S5. The steps for extracting the height of a single crevice in a karst cave from an earthquake are as follows: using earthquake crevice cave quantitative carving technology, the spatial distribution of the crevice cave is carved, and the height of a single crevice cave is extracted.

[0020] S6. Fitting the correction coefficient of the earthquake fissure cavity: Using the height of a single fissure cavity extracted in step S5 and the height of the main body of a single fissure cavity calculated in step S4, establish a cross-plot and fit to determine the correction coefficient of the earthquake fissure cavity sculpture.

[0021] S7. Step 7: Determining the size of the seismic fissure cave body. Using the correction coefficient of the seismic fissure cave sculpture obtained in step S6, the seismic fissure cave sculpture is corrected to obtain the accurate size of the fissure cave body, thereby finely depicting the scale of the fissure cave body.

[0022] A further preferred option includes establishing a database of the main body size of karst caves of various types, which involves classifying the main body size and fracture zone width of karst caves measured in the field according to different karst types, and establishing a database of the main body size of karst caves of each type.

[0023] In a further preferred embodiment, in step S2, based on the database of the main body size of the karst caves of various karst types, the main body size of the karst caves of various karst types and the corresponding fracture zone width are used to establish an intersection diagram of the main body size of the karst caves of various karst types and the fracture zone width, and fit the diagram to determine the calculation formula of the main body height of the karst caves of various karst types and the fracture zone width.

[0024] In a further preferred embodiment, in step S5, the spatial distribution of the seismic fissure cave is carved using quantitative carving technology to form a seismic fissure cave sculpture. The height of the main body of each individual fissure cave is extracted from the seismic fissure cave sculpture to establish a database of the main body height of the main body of the seismic fissure cave.

[0025] In a further preferred embodiment, in step S6, the heights of the main bodies of individual karst caves in the database of karst cave body heights, as well as the corresponding heights of the main bodies of individual karst caves calculated in step S4, are used to establish a cross-plot and fit the correction coefficients of the karst cave carving.

[0026] In a further preferred embodiment, step S4 also includes a step of correcting the estimated height of the main body of the karst cave in a single fractured cave. Specifically, using well test data, the radii of the inner and outer zones of the fractured cave are interpreted, the outer zone radius is compared and analyzed with the fracture zone, and the inner zone radius is compared and analyzed with the estimated size of the main body of the karst cave in a single fractured cave, thereby correcting the estimated height of the main body of the karst cave.

[0027] More preferably, the types of fissures include buried mountain karst fissures and interlayer karst fissures.

[0028] More preferably, the size of the main body of the cave includes the length, width and height of the main body of the cave.

[0029] More preferably, in step S3, the drilling anomaly includes any one of leakage, gas intrusion, gas surge, and overflow.

[0030] In a further preferred embodiment, in step S2, the formula for determining the height of the main body of the karst cave and the width of the fractured zone is expressed as y=a*x+b, where y represents the estimated height of the main body of a single karst cave, x represents the proportion of the fractured zone, and a and b represent coefficients.

[0031] In a further preferred embodiment, in step S6, the correction coefficient of the earthquake fissure carving is determined by fitting, denoted as z=c*y, where c represents the correction coefficient, z represents the height of the main body of the earthquake fissure carving, and y represents the estimated height of the main body of a single fissure carving.

[0032] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0033] 1. This invention provides an evaluation method for estimating the size of the main body of karst caverns in karst fractured-vuggy carbonate reservoirs using the width of fracture zones. This method guides the evaluation of the size of fractured-vuggy carbonate reservoirs in the Sichuan Basin, Tarim Basin, Ordos Basin, and right bank of the Amu Darya River. Analysis of the application results shows that the accuracy of the size estimation of fractured-vuggy carbonate reservoirs using this technology is more than 70% higher than that of the original seismic fracture-vuggy volume estimation, with an accuracy of over 85% for the size of the fractured-vuggy bodies. This method plays a crucial role in the exploration and development of fractured-vuggy carbonate oil and gas reservoirs.

[0034] 2. This method is applicable to the characterization of fractured-vuggy carbonate reservoirs. Based on the formation mechanism and internal structure of karst fractured-vuggy bodies, this method identifies the correlation between the formation of fracture zones and the main body of the karst cave, fits the relevant formulas, estimates the size of the main body of the karst cave, and thus evaluates the size of the fractured-vuggy body. The fractured-vuggy body size calculated by this method is an important parameter for estimating the reserves of fractured-vuggy carbonate reservoirs and a crucial parameter for formulating oil and gas reservoir development strategies. It has significant market demand and broad application prospects in the exploration and development of fractured-vuggy carbonate reservoirs.

[0035] 3. This invention focuses on the precise characterization of fracture-cavity size, dissecting the internal structure and formation mechanism of fracture-cavities, establishing the correlation between the fracture zone and the main body of the karst cave, calculating the height of the main body of the karst cave, thereby determining the height of the fracture-cavity, establishing the correlation between the seismic fracture-cavity sculpted body and the height of the fracture-cavity, determining the correction coefficient or correction formula for the seismic fracture-cavity sculpted body, correcting the seismic fracture-cavity sculpted body, and finally accurately depicting the location, scale and spatial distribution of fracture-cavities, providing geological basis for the efficient exploration and development of fracture-cavity carbonate oil and gas reservoirs. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method of the present invention;

[0037] Figure 2 Diagram showing the internal structure of a karst fissure cave.

[0038] Figure 3 This is a diagram showing the intersection of the width ratio of the fractured area of ​​a karst fissure cave and the height of the main cave body.

[0039] Figure 4 A diagram showing the intersection of the height of the seismic fracture cavity carved with the height of the fracture cavity calculated from the logging well. Detailed Implementation

[0040] The following are exemplary embodiments of the invention as defined by the claims and their equivalents, taken in conjunction with the accompanying drawings, to aid in a comprehensive understanding. The specific details described herein are to be considered exemplary only and not to limit the scope of the invention. Therefore, those skilled in the art can make various changes and modifications to the embodiments without departing from the scope and spirit of the invention.

[0041] Example 1

[0042] Currently, the Dengying Formation fracture-vuggy carbonate gas reservoir in the Sedanian system of the Sichuan Basin has a reservoir size exceeding 2 trillion cubic meters, making it the main gas reservoir for exploration and development in Southwest China. The Ordovician fracture-vuggy carbonate oil and gas reservoir in the Tarim Basin is the main oil and gas reservoir being developed by the Northwest Bureau of China Petroleum & Chemical Corporation (Sinopec) and the Tarim Oilfield. The Cambrian fracture-vuggy carbonate gas reservoir in the Ordos Basin is the main replacement gas reservoir for the next stage. Domestic fracture-vuggy carbonate oil and gas reservoirs are large in scale and have enormous exploration and development potential. However, due to strong heterogeneity, there is a lack of precise methods for calculating the size of fractures and cavities. Therefore, the developed evaluation method for estimating the main size of karst cavities in fracture-vuggy carbonate reservoirs using the width of fracture zones is of great significance for the efficient exploration and development of fracture-vuggy carbonate oil and gas reservoirs, and has significant market demand and broad application prospects.

[0043] Fractured-vuggy carbonate reservoirs are geologically complex and present diverse technical challenges. Competitors seeking efficient exploration and development of these reservoirs face similar technical difficulties, making it challenging to circumvent this method and circumvent its limitations. This method involves estimating the size of fractures and cavities in fractured-vuggy carbonate reservoirs, thereby improving the accuracy of predicted fracture and cavity sizes.

[0044] As a preferred embodiment of the present invention, please refer to the appendix to the specification. Figure 1 As shown in the figure, this embodiment discloses an evaluation method for estimating the main body size of karst caves in karst fracture-vuggy carbonate reservoirs using the width of fractured zones. The method includes the following steps:

[0045] S1. Steps for describing fissures and caves in the field: Locate outcrops of fissures and caves formed under the same conditions as those in the study area and conduct field reconnaissance; Measure the size of the main body of the fissure and cave and the width of the fracture zone of the fissure and cave.

[0046] S2. Fitting the calculation formula for the main body of the karst cave: Using the size of the main body of the karst cave and the width of the fracture zone of the karst cave obtained from step S1, establish the intersection diagram of the size of the main body of the karst cave and the width of the fracture zone, and fit the calculation formula for the height of the main body of the karst cave and the width of the fracture zone.

[0047] S3. Steps for determining the width of the fracture zone in the study area: Using the logging data of the study area, the top and bottom depths of drilling anomalies in the fracture zone during drilling are statistically analyzed; then, the top and bottom depths of the fracture zone are precisely interpreted using the measurement data of the study area to determine the location and width of the fracture zone in a single fracture zone.

[0048] S4. Estimate the height of the main body of the karst cave in the study area. Use the calculation formula for the height of the main body of the karst cave and the width of the fracture zone obtained by fitting the formula obtained by step S2, and the width of the fracture zone in a single karst cave obtained by step S3, to calculate the height of the main body of the karst cave in a single karst cave.

[0049] S5. The steps for extracting the height of a single crevice in a karst cave from an earthquake are as follows: using earthquake crevice cave quantitative carving technology, the spatial distribution of the crevice cave is carved, and the height of a single crevice cave is extracted.

[0050] S6. Fitting the correction coefficient of the earthquake fissure cavity: Using the height of a single fissure cavity extracted in step S5 and the height of the main body of a single fissure cavity calculated in step S4, establish a cross-plot and fit to determine the correction coefficient of the earthquake fissure cavity sculpture.

[0051] S7. Step 7: Determining the size of the seismic fissure cave body. Using the correction coefficient of the seismic fissure cave sculpture obtained in step S6, the seismic fissure cave sculpture is corrected to obtain the accurate size of the fissure cave body, thereby finely depicting the scale of the fissure cave body.

[0052] Example 2

[0053] As another preferred embodiment of the present invention, this embodiment further elaborates and supplements the technical solution of the present invention based on the above-described embodiment 1. In this embodiment, the evaluation method for estimating the main body size of karst fracture-vuggy carbonate reservoir karst caves using the width of the fractured zone specifically includes the following 9 steps:

[0054] S1. Field description of the crevice / cavity;

[0055] S2. Establish a database of the sizes of various types of sutures and openings;

[0056] S3. Fitting the calculation formula for the main body of the karst cave;

[0057] S4. Determine the width of the crushing zone;

[0058] S5. Estimate the height of the main body of the cave;

[0059] S6. Estimate the height of the main karst cave and correct it; interpret the radius of the inner and outer zones by well testing.

[0060] S7. Seismic extraction of the height of a single fissure cavity;

[0061] S8. Fit the correction coefficient or correction formula for the seismic joint cavity;

[0062] S9. Determine the size of the slit.

[0063] The specific steps are detailed below:

[0064] S1. Field description of karst fissures and caves: Locate the outcrops of buried karst fissures and caves or interlayer karst fissures and caves formed under the same conditions in the study area, conduct field reconnaissance, and accurately measure the length, width, and height of the buried karst fissures and caves or interlayer karst fissures and caves, as well as the fracture zone and the length, width, and height of the main body of the cave.

[0065] S2. Establish a database of the size of various types of karst caves; classify the length, width, and height of the karst caves or interlayer karst caves in the buried hills, which are accurately measured by field surveys, according to different karst types, and establish a database of the size of karst caves for each type.

[0066] S3. Fitting the calculation formula for the main body of the karst cave; using the fracture zone of the buried mountain karst fissure cave or the interlayer karst fissure cave measured by field outcrops, and the length, width and height of the main body of the karst cave, establish the intersection diagram of the height of the main body of the karst cave and the width of the fracture zone for various types of karst fissure caves, and fit the calculation formula for the height of the main body of the karst cave and the width of the fracture zone (abbreviated as: Formula 1, each study area needs to refit this calculation formula based on the measured data).

[0067] S4. Determine the width of the fracture zone; use logging data to count the top and bottom depths of drilling anomalies (loss, gas intrusion, gas surge, overflow, etc.) within the fracture zone during drilling, use logging data to interpret the top and bottom depths of the fracture zone in detail, and accurately determine the location and width of the fracture zone within a single fracture cavity.

[0068] S5. Estimate the height of the main body of the cave; use Formula 1 to calculate the height of the main body of a single crevice cave.

[0069] S6. Correct the estimated height of the main body of the karst cave; using well test data, interpret the radii of the inner and outer zones of the fractured cave, compare and analyze the outer zone radius with the fracture zone, compare and analyze the inner zone radius with the estimated size of the main body of the karst cave, and correct the estimated size of the main body of the karst cave and the fractured cave.

[0070] S7. Extract the height of individual seismic fracture cavities; using quantitative seismic fracture cavity carving technology, carve the spatial distribution of the fracture cavities (referred to as: seismic fracture cavity carving), extract the height of each individual fracture cavity, and establish a seismic fracture cavity height database.

[0071] S8. Fit the correction coefficient or correction formula for the seismic fracture cavity; use the height of each individual fracture cavity extracted from the quantitative seismic fracture cavity carving to establish a cross-plot with the height of the same individual fracture cavity calculated previously, and fit and determine the correction coefficient or correction formula for the seismic fracture cavity carving (abbreviated as: Formula 2, each study area needs to refit this calculation formula based on the measured data).

[0072] S9. Determining the size of the seismic crack / cavity: Using the correction coefficient or correction formula of the seismic crack / cavity sculpture, the seismic crack / cavity sculpture is corrected to obtain the accurate size of the crack / cavity, thereby finely depicting the scale of the crack / cavity.

[0073] Example 3

[0074] As another preferred embodiment of the present invention, this method embodiment selects a gas field in Xinjiang. When drilling encounters buried hill karst fissures or interlayer karst fissures, serious leakage or venting will occur, making it difficult to maintain the drilling, prematurely completing the drilling, and making logging impossible. Therefore, it is difficult to completely drill through large buried hill karst fissures or interlayer karst fissures and determine the scale of such fissures.

[0075] Research indicates that buried hill karst fissure caves or inter-layer karst fissure caves, under the influence of overlying pressure, will form fracture zones in the upper part of the cave and the surrounding strata under stress. We divide buried hill karst fissure caves or inter-layer karst fissure caves into three zones: the cave body, the fracture zone, and the surrounding rock (such as...). Figure 2 (As shown).

[0076] Through field surveys in the area, the length, width, and height of buried karst fissures and caves, or interlayer karst fissures and caves, were precisely measured. The fracture zones and the main body of the caves within these fissures and caves were also precisely measured. These measurements were then categorized according to different karst types, and a database of the sizes of fissures and caves for each karst type was established.

[0077] Using field outcrops to measure the fracture zone, length, width, and height of the main body of buried karst fissure caves or interlayer karst fissure caves, a cross-sectional diagram of the height of the main body of the cave and the width of the fracture zone for various types of karst fissure caves is established (e.g., Figure 3 As shown in the figure, the formula for calculating the height of the main body of the cave and the width of the fractured zone is: Cave height = -0.6629 * fractured zone ratio + 79.01 (Formula 1)

[0078] Then, using the well logging data of the gas field, the top and bottom depths of drilling anomalies (loss of gas, gas intrusion, gas surge, overflow, etc.) within the fracture zone during the drilling process are statistically analyzed. The top and bottom depths of the fracture zone are then precisely interpreted using the well logging data to accurately determine the location and width of the fracture zone within a single fractured cavity. Using Formula 1, the height of the main body of the karst cave within a single fractured cavity is calculated (Table 1).

[0079] Table 1. Estimated height of fractured cavity encountered in a single well in an oil and gas field.

[0080]

[0081] Using quantitative carving technology for seismic fracture cavities, the spatial distribution of the fracture cavities (referred to as: seismic fracture cavity carvings) is carved, the height of each individual fracture cavity is extracted, and a database of seismic fracture cavity heights is established.

[0082] By using the heights of individual seismic cracks extracted from the quantitative sculpted seismic crack body and the previously calculated heights of the same individual seismic crack body, a cross-plot is created. The correction coefficient or correction formula (referred to as Formula 2, see reference) for the seismic crack body sculpted seismic crack body is then fitted and determined. Figure 4 ).

[0083] The height of the seismic fracture cavity is calculated as 0.4962 * the height of the seismic cavity calculated from the logging well (Formula 2).

[0084] Using the earthquake crack carving correction formula, the earthquake crack carving was corrected to obtain the accurate size of the crack (Table 2). The volume of the corrected crack is more consistent with the actual size, thus accurately depicting the scale of the crack.

[0085] Table 2. Estimated height of fractured cavities encountered in a single well in an oil and gas field.

[0086]

[0087] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An evaluation method for estimating the size of a cave body in a karst fracture-cave type carbonate reservoir using a breakdown bandwidth, characterized in that: The method comprises the following steps, S1, field fracture-cave body description step, searching for outcrops of fracture-cave bodies formed under the same conditions as the research area, and conducting field reconnaissance; the size of the cave body of the fracture-cave body is measured, and the width of the fracture zone of the fracture-cave body is measured; S2, fitting cave body calculation formula step, using the size of the cave body of the fracture-cave body and the width of the fracture zone of the fracture-cave body measured in S1 step, establishing the crossplot of the size of the cave body and the width of the fracture zone, and fitting to determine the calculation formula of the height of the cave body and the width of the fracture zone; S3, fracture zone width determination step of fracture-cave bodies in the research area, using the logging data of the research area, and statistically analyzing the top and bottom depths of the drilling anomalies in the fracture zone during drilling; then, using the measurement data of the research area, the top and bottom depths of the fracture zone are finely interpreted to determine the position and width of the fracture zone in a single fracture-cave body; S4, step of estimating the height of the cave body of the fracture-cave body in the research area, using the calculation formula of the height of the cave body and the width of the fracture zone fitted in S2 step, and the width of the fracture zone in a single fracture-cave body determined in S3 step, calculating the height of the cave body of a single fracture-cave body; S5, step of extracting the height of the cave body of a single fracture-cave body by seismic, using the quantitative carving technology of seismic fracture-cave bodies to carve the spatial distribution of the fracture-cave bodies, and extracting the height of a single fracture-cave body; S6, fitting seismic fracture-cave body correction coefficient step, using the height of a single fracture-cave body extracted in S5 step, and the height of the cave body of a single fracture-cave body calculated in S4 step, establishing a crossplot, and fitting to determine the correction coefficient of the seismic fracture-cave carving body; S7, step of determining the size of the cave body of the fracture-cave body, using the correction coefficient of the seismic fracture-cave carving body obtained in S6 step to correct the seismic fracture-cave carving body, and obtaining the accurate size of the fracture-cave body, so as to finely depict the scale of the fracture-cave body.

2. The evaluation method for estimating the size of a cave body in a karst fracture-cave type carbonate reservoir using a breakdown bandwidth according to claim 1, characterized in that: It also includes the step of establishing a database of the size of the cave body of various fracture-cave bodies, classifying and processing the size of the cave body of the fracture-cave body measured by field reconnaissance and the width of the fracture zone according to different karst types, and establishing a database of the size of the cave body of the fracture-cave body of each karst type.

3. The evaluation method for estimating the size of the cave body of the karst fracture-cave type carbonate reservoir according to claim 2, characterized in that: In S2 step, according to the size of the cave body of the fracture-cave body of each karst type and the corresponding width of the fracture zone in the database of the size of the cave body of the fracture-cave body of each karst type, a crossplot of the size of the cave body of the fracture-cave body of each karst type and the width of the fracture zone is established, and the calculation formula of the height of the cave body of the fracture-cave body of each karst type and the width of the fracture zone is fitted and determined.

4. The evaluation method for estimating the size of the main body of a karst fracture-cave type carbonate reservoir cave using a breakdown bandwidth according to any one of claims 1 to 3, characterized in that: In S5 step, the quantitative carving technology of seismic fracture-cave bodies is used to carve the spatial distribution of the fracture-cave bodies, form the seismic fracture-cave carving body, and extract the height of the cave body of each single fracture-cave body from the seismic fracture-cave carving body, and a database of the height of the cave body of the seismic fracture-cave body is established.

5. The evaluation method for estimating the size of the cave body of the karst fracture-cave type carbonate reservoir according to claim 4, characterized in that: In S6 step, using the height of the cave body of each single fracture-cave body in the database of the height of the cave body of the seismic fracture-cave body, and the height of the cave body of the corresponding single fracture-cave body calculated in S4 step, a crossplot is established, and the correction coefficient of the seismic fracture-cave carving body is fitted.

6. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: In the step S4, a step of correcting the estimated height of the cave body of the single fracture-cave body is further included, specifically, the well test data is used to interpret the inner and outer zone radii of the fracture-cave body, the outer zone radius is compared and analyzed with the fracture zone, the inner zone radius is compared and analyzed with the estimated size of the cave body of the single fracture-cave body, and the estimated height of the cave body is corrected.

7. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: The fracture-cave body type includes buried hill karst fracture-cave body and interlayer karst fracture-cave body.

8. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: The size of the cave body includes length, width and height of the cave body.

9. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: In the step S3, the drilling anomaly includes any one of loss, gas invasion, gas surge and overflow.

10. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: In the step S2, the calculation formula of fitting and determining the height of the cave body and the width of the fracture zone is expressed as y=a*x+b, wherein y represents the estimated height of the cave body of the single fracture-cave body, x represents the proportion of the fracture zone, and a and b represent coefficients.

11. The method for evaluating the size of the main body of the karst fracture-cave type carbonate reservoir cave by using the crushing zone width according to any one of claims 1-3, characterized in that: In the step S6, the correction coefficient of the seismic fracture-cave sculpture body is determined by fitting and is expressed as z=c*y, wherein c represents the correction coefficient, z represents the height of the cave body of the seismic fracture-cave sculpture body, and y represents the estimated height of the cave body of the single fracture-cave body.

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