Method and system for identifying low-order-level sequence interface of carbonate rock stratum system

Abstract

The invention discloses a method and system for identifying a low-order sequence interface of a carbonate rock stratum system, and the method comprises the steps: collecting rock samples from different positions in the carbonate rock stratum system to be researched, then obtaining the types of non-carbonate minerals contained in different rock samples, and obtaining the content of each type of non-carbonate minerals in the corresponding rock sample; according to the depths of stratums where different rock samples are located, first change characteristics of the types of non-carbonate minerals along with the depths of the stratums and second change characteristics of the content of each type of non-carbonate minerals along with the depths of the stratums are analyzed, and according to the analysis result, the geologic characteristic change condition of the to-be-researched carbonate rock stratum system is further obtained. And determining a low-sequence-level sequence interface in the current carbonate rock stratum system to be researched. According to the method, effective identification of the carbonate rock stratum system low-order-level sequence interface is realized, and technical support is provided for reservoir prediction and oil-gas exploration potential evaluation of a carbonate rock development area.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil exploration, and in particular relates to a method and system for identifying low-order sequence boundaries in carbonate rock series. Background Art

[0002] The formation of carbonate sequences is mainly controlled by the intensity of tectonic movements and the relative rise and fall of sea level. There are a large number of sequence boundaries with different orders and genetic types in the strata, and various geological processes related to these sequence boundaries control the development of carbonate reservoirs. According to the intensity of tectonic movements, the relative amplitude and duration of sea-level rise and fall, sequence boundaries can be divided into six orders. Among them, high-order sequence boundaries (orders I-III) correspond to various unconformities, and low-order sequence boundaries (orders IV-VI) mainly correspond to flooding surfaces or local sedimentary events.

[0003] Order-I and order-II sequence boundaries mainly control the formation of large-scale karst reservoirs. The overall karstification of order-III sequence boundaries is relatively weak, and the reservoir distribution is relatively limited. However, it is most closely related to the development and distribution of platform-edge and intra-platform reef-flat facies reservoirs. The sequence boundary has a dual control on sedimentary facies and diagenesis. If the strata below the order-IV to order-VI sequence boundaries were deposited at the platform margin, intra-platform shoal, intertidal zone, or supratidal zone, due to subaerial dissolution during the penecontemporaneous exposure, the reservoir properties below the interface were improved; if fractures developed and formation fluids were active during burial, it could form the basis for the formation of high-quality reservoirs such as large-scale fracture-hydrothermal type or fault dissolution bodies.

[0004] After carbonate sediments are deposited, even a very small sea-level fall will cause exposure and transformation by meteoric freshwater diagenesis, thus forming more low-order sequence boundaries reflecting the transition of sediments from seawater to freshwater. Generally, a dissolution zone or reservoir body with a certain thickness range will develop below these low-order sequence boundaries. Therefore, correctly identifying sequence boundaries, especially low-order sequence boundaries, is of great significance for reservoir prediction.

[0005] Currently, due to the differences in the order and genetic types of sequence boundaries, the methods for identifying carbonate sequence boundaries also vary. The main methods for identifying sequence boundaries are seismic profile reflection characteristics method, sedimentation rate method, vitrinite reflectance method, acoustic time difference method, trace elements, biostratigraphy and sequence stratigraphy, element geochemistry, and carbon isotope methods. Using the aforementioned methods, even high-order sequence boundaries can be effectively traced on seismic profiles, but it is difficult to accurately identify low-order sequence boundaries. Summary of the Invention

[0006] To solve the above problems, an embodiment of the present invention provides a method for identifying low-order sequence boundaries in carbonate rock formations, including: collecting rock samples from different positions within the carbonate rock formation to be studied, then obtaining the types of non-carbonate minerals contained in different rock samples, and obtaining the content of each type of non-carbonate mineral in the corresponding rock sample; according to the formation depths where different rock samples are located, analyzing the first variation characteristics of the non-carbonate mineral types with respect to the formation depth, and the second variation characteristics of the content of each type of non-carbonate mineral with respect to the formation depth, and based on the analysis results, further obtaining the variation of the geological characteristics of the carbonate rock formation to be studied, and based on this, determining the low-order sequence boundaries within the current carbonate rock formation to be studied.

[0007] Preferably, in the step of obtaining the types of non-carbonate minerals contained in different rock samples, it includes: according to the physical parameters of the rock samples, dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals; dividing the heavy minerals into a strongly magnetic part and a weakly magnetic part, and further dividing the weakly magnetic part into an electromagnetic part and a non-magnetic part; performing fine washing treatment on the non-magnetic part, and dividing the non-magnetic part into a transparent part and an opaque part.

[0008] Preferably, in the process of dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, it includes: crushing each rock sample and obtaining the relative density of each crushed rock sample, so as to use the relative density as the physical parameter of the rock sample to divide the non-carbonate minerals, wherein the non-carbonate minerals contained in the crushed rock samples with a relative density greater than or equal to / less than a preset density threshold are used as the heavy minerals / light minerals.

[0009] Preferably, in the process of dividing the heavy minerals into a strongly magnetic part and a weakly magnetic part, and further dividing the weakly magnetic part into an electromagnetic part and a non-magnetic part, it includes: using a strong magnetic separation method to divide the heavy minerals into a strongly magnetic part and a weakly magnetic part; and using an electromagnetic separation method to divide the weakly magnetic part into an electromagnetic part and a non-magnetic part.

[0010] Preferably, after dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, the method further includes: performing age determination, fission track, cathodoluminescence and provenance analysis on the heavy minerals, and obtaining the acid-insoluble substances in the light minerals and performing diffraction analysis on them, so as to correct the variation of the geological characteristics according to the analysis results.

[0011] Preferably, the geological characteristics of the carbonate rock formation to be studied include but are not limited to: sedimentary environment, paleo-water depth, paleo-climate, redox conditions, exposure and erosion status, provenance area and hydrodynamic conditions, unconformity and weathering crust karst, tectonic uplift and erosion and karstification.

[0012] Preferably, the rock samples include, but are not limited to, cuttings, cores or surface outcrops from different tectonic lithofacies zones, cuttings, cores or surface outcrops from different stratigraphic groups, and cuttings, cores or surface outcrops from different intervals.

[0013] Preferably, before obtaining the types of non-carbonate minerals contained in different rock samples, the method further includes: removing impurities from the cuttings in the different rock samples; and dividing the cores in the different rock samples into matrix and fracture-vug fillings, so as to match the geological characteristics of the carbonate rock formation system to be studied with the actual geological state.

[0014] Preferably, the strongly magnetic part includes, but is not limited to, magnetite, pyrrhotite, chalcopyrite, iron platinum ore and native iron; the electromagnetic part includes, but is not limited to, ilmenite, pseud-ilmenite, columbite and monazite.

[0015] On the other hand, the present invention also provides a system for identifying low-order sequence boundaries of a carbonate rock formation system. The system includes the following modules: a mineral information acquisition module, which is used to acquire the types of non-carbonate minerals contained in different rock samples collected from different positions within the carbonate rock formation system to be studied, and obtain the content of each type of non-carbonate mineral in the corresponding rock sample; a characteristic analysis module, which is used to analyze the first variation characteristics of the non-carbonate mineral types with the formation depth, and the second variation characteristics of the content of each type of non-carbonate mineral with the formation depth according to the formation depths of different rock samples, and further obtain the geological characteristic variation of the carbonate rock formation system to be studied based on the analysis results, and based on this, determine the low-order sequence boundaries within the current carbonate rock formation system to be studied.

[0016] Compared with the prior art, one or more embodiments of the above solution may have the following advantages or beneficial effects:

[0017] The present invention provides a method and a system for identifying low-order sequence boundaries of a carbonate rock formation system. The method acquires the types of non-carbonate minerals and the content of each type of non-carbonate mineral at different positions within the carbonate rock formation system to be studied, and analyzes the variation characteristics of the non-carbonate mineral types and the content of each type of non-carbonate mineral with the formation depth accordingly, and further obtains the geological characteristic variation of the carbonate rock formation system to be studied, and determines the low-order sequence boundaries within the current carbonate rock formation system to be studied based on this. The present invention realizes the effective identification of low-order sequence boundaries that are conventionally unidentifiable in carbonate rock formation systems, provides technical support for reservoir prediction and oil and gas exploration potential evaluation in carbonate rock development areas. At the same time, the present invention also provides a data basis for stratigraphic correlation between strata lacking fossils, having a single lithology and showing diachronous phenomena.

[0018] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the structure particularly pointed out in the specification, claims and drawings. Description of the Drawings

[0019] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0020] Figure 1 is a flowchart of the method for identifying low-order sequence boundaries in carbonate rock series according to an embodiment of the present application.

[0021] Figure 2 is an exemplary diagram of a variable profile of the method for identifying low-order sequence boundaries in carbonate rock series according to an embodiment of the present application.

[0022] Figure 3 is a block diagram of modules of the system for identifying low-order sequence boundaries in carbonate rock series according to an embodiment of the present application. Detailed Embodiments

[0023] The following will describe in detail the embodiments of the present invention in conjunction with the drawings and embodiments, so as to fully understand how the present invention uses technical means to solve technical problems and the implementation process of achieving technical effects and implement accordingly. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0024] In addition, the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0025] Currently, due to the differences in the levels and genetic types of sequence boundaries, there are also differences in the methods for identifying carbonate sequence boundaries. The main methods for identifying sequence boundaries are seismic profile reflection feature method, sedimentation rate method, vitrinite reflectance method, acoustic time difference method, trace elements, biostratigraphy and sequence stratigraphy, element geochemistry and carbon isotope, etc. Using the aforementioned methods, even high-level sequence boundaries can be effectively traced on seismic profiles, but it is difficult to accurately identify low-level sequence boundaries.

[0026] Therefore, to solve the above problems, the present invention proposes a method and system for identifying low-order sequence boundaries in carbonate rock formations. The method obtains the types of non-carbonate minerals and the content of each type of non-carbonate mineral at different positions within the carbonate rock formation to be studied, and analyzes the variation characteristics of the types of non-carbonate minerals and the content of each type of non-carbonate mineral with the change of stratigraphic depth, further obtaining the change of geological characteristics of the carbonate rock formation to be studied, and determining the low-order sequence boundaries within the current carbonate rock formation to be studied. The present invention realizes the effective identification of low-order sequence boundaries that are conventionally unidentifiable in carbonate rock formations, provides technical support for reservoir prediction and evaluation of oil and gas exploration potential in carbonate rock development areas. At the same time, the present invention also provides a data basis for stratigraphic correlation between strata lacking fossils, having a single lithology and showing diachronous phenomena.

[0027] Example 1

[0028] Figure 1 It is a step diagram of the method for identifying low-order sequence boundaries in carbonate rock formations according to an embodiment of the present application. The following will refer to Figure 1 to illustrate each step of this method.

[0029] As Figure 1 shown, in step S110, rock samples are collected from different positions within the carbonate rock formation to be studied. Then, the types of non-carbonate minerals contained in the different rock samples are obtained, and the content of each type of non-carbonate mineral in the corresponding rock sample is obtained. In practical applications, the content of non-carbonate minerals in carbonate rock strata is extremely low, and there are certain difficulties in quantitatively identifying non-carbonate minerals and measuring their content. Therefore, in this embodiment, rock samples are collected from different positions within the carbonate rock formation to be studied, and by analyzing the types and content of non-carbonate minerals in each rock sample, the types and content of non-carbonate minerals in the entire carbonate rock formation are obtained based on the data of scattered points, so as to identify the low-order sequence boundaries within the carbonate rock formation accordingly.

[0030] Carbonate rocks are composed of carbonate minerals (such as calcite, dolomite, aragonite, siderite, magnesite, rhodochrosite, etc.) and non-carbonate components. Among them, the non-carbonate components include: terrigenous detrital minerals (such as terrigenous detrital quartz, feldspar, allochthonous clay minerals, heavy minerals, etc.) derived from wind transportation, river transportation (during flood events in dried-up river channels), or erosion of underlying rock formations; and authigenic non-carbonate minerals (such as silica, gypsum, anhydrite, glauconite, pyrite, hematite, collophane, fluorite, barite, celestite, dickite, authigenic clay minerals, etc.). Therefore, in the embodiments of the present application, the rock samples taken from the carbonate rock formation system to be studied include, but are not limited to: cuttings, cores or surface outcrops in different tectonic lithofacies zones, cuttings, cores or surface outcrops in different stratigraphic groups, and cuttings, cores or surface outcrops in different segments. Thus, it can be seen that the present invention is based on rock samples that comprehensively cover different geological structures of the carbonate rock formation system, realizes the identification of low-order sequence boundaries within the current carbonate rock formation system, and effectively ensures the comprehensiveness and reliability of the identification results.

[0031] Before obtaining the types of non-carbonate minerals contained in different rock samples, the present invention also performs impurity removal treatment on the cuttings in different rock samples; and divides the cores in different rock samples into matrix and fracture-vug filling materials, so that the geological characteristics of the carbonate rock formation system to be studied match the actual geological state. In the embodiments of the present application, the different rock samples collected are divided into cuttings and cores for separate processing. Among them, impurity removal treatment is performed on the cuttings, and at the same time, the cores are divided into matrix and fracture-vug filling materials to determine the more specific position of the cores within the carbonate rock formation system, thereby making the obtained geological characteristics of the carbonate rock formation system to be studied match the actual geological state. In addition, the cores in this embodiment are also used to calibrate the position of the cuttings in the carbonate rock formation system to be studied, thereby determining the more specific position of the cuttings within the carbonate rock formation system. In this way, the present invention identifies the low-order sequence boundary based on the more specific positions of the cuttings and cores within the carbonate rock formation system to be studied, ensuring the consistency of the finally obtained identification result with the actual sequence boundary.

[0032] The prior art usually first separates non-carbonate minerals from carbonate rocks, then classifies the separated non-carbonate minerals, and then conducts different analysis items for each type of non-carbonate mineral. Among them, in the process of classifying non-carbonate minerals, the acid-insoluble residues in carbonate rocks are divided into two particle size components of greater than or equal to 2 μm and less than 2 μm, and the residues (mainly composed of quartz, feldspar and various heavy minerals) of the component greater than or equal to 2 μm are classified into one category, and the residues (mainly composed of various clay minerals) of the component less than 2 μm are classified into another category. Thus, it can be seen that the classification of non-carbonate minerals in the prior art is a rough classification, and the identified low-order sequence boundary is bound to deviate from the actual situation to a certain extent.

[0033] Therefore, in the step of obtaining the types of non-carbonate minerals contained in different rock samples, the present invention first divides the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples. Then, the heavy minerals are divided into a strongly magnetic part and a weakly magnetic part, and the weakly magnetic part is further divided into an electromagnetic part and a non-magnetic part. Finally, the non-magnetic part is subjected to fine elutriation treatment to divide the non-magnetic part into a transparent part and an opaque part. The present invention accurately identifies the low-order sequence boundaries based on the refined classification of the types of non-carbonate minerals contained in different rock samples. Therefore, in the embodiments of the present application, a preliminary classification is first performed according to the physical parameters of the rock samples, and the non-carbonate minerals contained in the corresponding rock samples are divided into heavy minerals and light minerals. Among them, the proportion of heavy minerals in the rock sample is less than 1%, and the proportion of light minerals in the rock sample is greater than 98%. Then, the divided heavy minerals are divided into a strongly magnetic part and a weakly magnetic part, and the weakly magnetic part is further divided into an electromagnetic part and a non-magnetic part. Finally, after weighing, the non-magnetic part is subjected to fine elutriation treatment (for example: elutriating with alcohol in a small elutriation dish), and the non-magnetic part is divided into a transparent part (obtained by using the thin section-polarizing microscope identification method) and an opaque part (obtained by using the polished section-reflecting microscope identification method). Then, the transparent part and the opaque part are weighed respectively to obtain the total weight and compared with the weighing result of the non-magnetic part to ensure the integrity of the non-magnetic part participating in the identification of the low-order sequence boundary.

[0034] In the process of dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, each rock sample is broken, and the relative density of each broken rock sample is obtained. Thus, the relative density is used as the physical parameter of the rock sample to divide the non-carbonate minerals. Among them, the non-carbonate minerals contained in the broken rock samples with a relative density greater than or equal to / less than the preset density threshold are used as heavy minerals / light minerals. In the embodiments of the present application, the collected different rock samples are first weighed respectively. After obtaining the weighing results, the corresponding rock samples are broken to a particle size of 40-140 mesh. Then, the broken rock samples are weighed again and compared with the previous weighing results to ensure the integrity of the rock samples participating in the identification of the low-order sequence boundary. After obtaining the broken rock samples, the relative density of each broken rock sample is calculated. Based on this, the relative density is used as the physical parameter of the rock sample. The non-carbonate minerals contained in the broken rock samples with a relative density greater than or equal to the preset density threshold are used as heavy minerals, and the non-carbonate minerals contained in the broken rock samples with a relative density less than the preset density threshold are used as light minerals to divide the non-carbonate minerals contained in the corresponding rock samples. In a specific embodiment of the present application, the preset density threshold is 2.86.

[0035] In the process of dividing heavy minerals into a strong magnetic part and a weak magnetic part, and further dividing the weak magnetic part into an electromagnetic part and a non-magnetic part, a strong magnetic separation method is used to divide heavy minerals into a strong magnetic part and a weak magnetic part; and an electromagnetic separation method is used to divide the weak magnetic part into an electromagnetic part and a non-magnetic part. In a specific embodiment of the present application, the strong magnetic separation method is implemented based on a permanent magnet, and the electromagnetic separation method is implemented based on an electromagnetic instrument.

[0036] In a specific embodiment of the present application, the strong magnetic part includes but is not limited to: magnetite, pyrrhotite, chalcopyrite, iron platinum ore, and native iron; the electromagnetic part includes but is not limited to: ilmenite, pseud-ilmenite, columbite, and monazite.

[0037] Furthermore, in step S120, according to the formation depths of different rock samples, analyze the first variation characteristics of non-carbonate mineral types with respect to formation depth, and the second variation characteristics of the content of each type of non-carbonate mineral with respect to formation depth. And based on the analysis results, further obtain the geological characteristic changes of the carbonate rock series to be studied. Based on this, determine the low-order sequence boundaries within the current carbonate rock series to be studied. The low-order sequence boundaries do not have large unconformities or sedimentary breaks. However, with the sea level fluctuating up and down, sequence boundaries with large unconformities or sedimentary breaks may experience short-term exposure to form low-order sequence boundaries. This change will cause changes in the types and contents of heavy minerals and light minerals. For example: at the exposed period interface, the content of hematite is relatively high in the oxidizing environment, and at the same time, the content of detrital minerals such as quartz in clastic rocks is relatively high. During the unexposed period, the reduction is stronger, the content of pyrite is relatively high, and the content of detrital minerals such as quartz is relatively low. In this embodiment, different rock samples are placed in the corresponding positions within the carbonate rock series to be studied according to their formation depths. Accordingly, based on the non-carbonate mineral types and contents at different positions, obtain the change trends of non-carbonate mineral types and contents between adjacent rock sample positions along the formation depth, so as to obtain the first variation characteristics and the second variation characteristics. After obtaining each variation characteristic, use each variation characteristic, combined with the physical property parameters of each type of non-carbonate mineral, etc., to analyze the geological characteristic changes of the carbonate rock series to be studied. Thus, identify a part of the low-order boundaries based on the geological characteristic changes, and identify another part of the low-order boundaries based on the first variation characteristics and the second variation characteristics, thereby achieving a comprehensive identification of the low-order sequence boundaries.

[0038] In a specific embodiment of the present application, according to each variation characteristic, combined with the geological characteristic changes, establish a qualitative - semi-quantitative variation stratigraphic profile of the carbonate rock series to be studied as shown in Figure 2 By reading the profile information, obtain the low-order sequence boundaries within the current carbonate rock series to be studied ( Figure 2 is an example diagram of the variation profile of the method for identifying low-order sequence boundaries of carbonate rock series in the embodiment of the present application). Refer toFigure 2 In a specific embodiment of the present application, the content of transparent heavy minerals is the total content of one or more of minerals such as zircon, rutile, tourmaline, leucoxene, apatite, garnet, epidote, pyroxene, amphibole, sphene, galena, and sphalerite; the content of stable heavy minerals is the total content of one or more of minerals such as zircon, rutile, tourmaline, ilmenite, leucoxene, anatase, and chromite; the content of relatively stable heavy minerals is the total content of one or more of minerals such as apatite and garnet; the ZTR index is obtained by calculating the ratio of the total content of zircon, rutile, and tourmaline to the content of transparent heavy minerals.

[0039] After classifying the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, the present invention also corrects the changes in geological characteristics according to the analysis results by performing age determination, fission track, cathodoluminescence, and provenance analysis on the heavy minerals, and obtaining and performing diffraction analysis on the acid-insoluble substances in the light minerals. Specifically, in this embodiment, on the basis of classifying the non-carbonate minerals, age determination and fission track are performed on zircon, apatite, etc. in the separated heavy minerals, and cathodoluminescence and provenance analysis are performed on zircon, sphene, apatite, monazite, epidote, etc.; for the separated light minerals, acid-insoluble substances (mainly clay minerals) are obtained through acid-insoluble substance treatment, and then X-ray diffraction analysis is performed on the acid-insoluble substances to determine their composition types and structural characteristics. After obtaining the above-mentioned heavy mineral analysis results and light mineral analysis results respectively, the changes in geological characteristics obtained according to each change characteristic are corrected according to the analysis results, and accordingly, the accuracy of the recognition result of the low-order sequence interface is further ensured by improving the accuracy of the changes in geological characteristics.

[0040] Sequence boundaries are controlled by tectonic movements, sea-level fluctuations, paleoclimate, and sediment supply. During the formation of sequence boundaries, due to differences in paleoclimate, sedimentary environment, temperature and pressure of diagenetic environment, and the closure and openness of the system as well as other physical and chemical conditions, differences in non-carbonate mineral composition and fabric above and below the sequence boundary are generally also caused. There are significant differences in non-carbonate minerals above and below the sequence boundary of carbonate rock strata. For example, due to different influences of the external source environment on sediments (non-mixed deposition), there are differences in the combination and content of heavy and light minerals above and below the sequence boundary. In addition, changes in the types and contents of clay minerals can also reflect the overall differences caused by the sedimentary environment at the sequence boundary (especially the changes in the paleoenvironment in which sediments are formed, resulting in differences in sediment composition and content). The changing trends of the types and contents of clay minerals are controlled by factors such as paleosalinity, acidity and alkalinity of the water medium, paleoclimate, and rainfall in the sedimentary environment. That is to say, if the strata are continuously deposited and the external source conditions change little, the types and contents of non-carbonate rock minerals in the strata change little. Thus, based on the differences in non-carbonate mineral types and contents, the identification of low-order sequence boundaries can be achieved.

[0041] Therefore, in a specific embodiment of the present application, the geological characteristics of the carbonate rock strata to be studied include but are not limited to: sedimentary environment, paleo-water depth, paleoclimate, redox conditions, exposure and erosion conditions, provenance area and hydrodynamic conditions, unconformity and weathered crust karst, tectonic uplift and erosion, and karstification. In practical applications, glauconite, rhodochrosite or siderite, rhodochrosite, ooids or nodules, magnetite, pyrite, etc. have the ability to characterize the sedimentary environment, paleo-water depth, and paleoclimate; limonite or hematite, kaolinite, chlorite, montmorillonite, illite and their crystallinity have the ability to characterize the paleoclimate, distinguish redox conditions, and exposure and erosion conditions; the types, contents, and combinations of heavy minerals in terrigenous clastics can be used for provenance area and hydrodynamic condition analysis; dark river sedimentary clastic rocks and fracture-cavity clastic fillings can be used to analyze the epigenetic karst development stages, so as to judge whether there is unconformity and weathered crust karst in the overlying strata; bauxite, red soil, hematite, quartz, etc. can be used to identify key unconformity surfaces and analyze tectonic uplift, erosion, and karstification, etc. Accordingly, in this embodiment, according to the first change characteristics of non-carbonate mineral types with the depth of the strata and the second change characteristics of the content of each type of non-carbonate mineral with the depth of the strata, the geological characteristic change situations of the carbonate rock strata to be studied corresponding to different types of geological characteristics are obtained. Furthermore, the obtained geological characteristic change situations and each change characteristic are respectively used to identify low-order sequence boundaries. Thus, by comparing the identification results with different data bases, the low-order sequence boundaries within the current carbonate rock strata to be studied are determined, thereby effectively improving the accuracy of the identification results.

[0042] Example 2

[0043] Based on the method for identifying low-order sequence boundaries in carbonate rock formations described in the above-mentioned Embodiment 1, an embodiment of the present invention also provides a system for identifying low-order sequence boundaries in carbonate rock formations. Figure 3 It is a block diagram of the modules of the system for identifying low-order sequence boundaries in carbonate rock formations according to an embodiment of the present application.

[0044] As Figure 3 shown, the system for identifying low-order sequence boundaries in carbonate rock formations in an embodiment of the present invention includes: a mineral information acquisition module 31 and a feature analysis module 32. Specifically, the mineral information acquisition module 31 is implemented according to the method described in the above step S110, and is configured to acquire the types of non-carbonate minerals contained in different rock samples collected from different positions in the carbonate rock formation to be studied, and obtain the content of each type of non-carbonate mineral in the corresponding rock sample; the feature analysis module 32 is implemented according to the method described in the above step S120, and is configured to analyze the first variation feature of the non-carbonate mineral types with the formation depth, and the second variation feature of the content of each type of non-carbonate mineral with the formation depth according to the formation depth of different rock samples, and further obtain the change situation of the geological features of the carbonate rock formation to be studied based on the analysis results, and thereby determine the low-order sequence boundary in the current carbonate rock formation to be studied.

[0045] The present invention discloses a method and a system for identifying low-order sequence boundaries in carbonate rock formations. The method acquires the types of non-carbonate minerals and the content of each type of non-carbonate mineral at different positions in the carbonate rock formation to be studied, and analyzes the variation features of the non-carbonate mineral types and the content of each type of non-carbonate mineral with the formation depth based on this, and further obtains the change situation of the geological features of the carbonate rock formation to be studied, and thereby determines the low-order sequence boundary in the current carbonate rock formation to be studied. The present invention realizes the effective identification of low-order sequence boundaries that are conventionally unidentifiable in carbonate rock formations, provides technical support for reservoir prediction and evaluation of oil and gas exploration potential in carbonate rock development areas. At the same time, the present invention also provides a data basis for stratigraphic correlation between strata lacking fossils, having a single lithology and showing diachronous phenomena.

[0046] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. 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 should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

[0047] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

[0048] Those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general-purpose computing device. They can be concentrated on a single computing device or distributed on a network composed of multiple computing devices. Optionally, they can be implemented by program codes executable by the computing device. Thus, they can be stored in a storage device for execution by the computing device, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated into a single integrated circuit module for implementation. In this way, the present invention is not limited to any specific combination of hardware and software.

[0049] Although the disclosed embodiments of the present invention are as above, the above content is only an embodiment adopted for the convenience of understanding the present invention and is not intended to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains can make any modifications and changes in the form of implementation and details without departing from the spirit and scope disclosed by the present invention. However, the patent protection scope of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for identifying low-order sequence boundaries in carbonate rock series, characterized in that, Including: Collect rock samples from different positions within the carbonate rock formation to be studied. Then, obtain the types of non-carbonate minerals contained in different rock samples, and obtain the content of each type of non-carbonate mineral in the corresponding rock sample. According to the formation depths of different rock samples, analyze the first variation characteristics of the non-carbonate mineral types with respect to the formation depth, and the second variation characteristics of the content of each type of non-carbonate mineral with respect to the formation depth. Based on the analysis results, further obtain the geological characteristic changes of the carbonate rock formation to be studied. Based on this, determine the low-order sequence boundaries within the current carbonate rock formation to be studied.

2. The method according to claim 1, wherein In the step of obtaining the types of non-carbonate minerals contained in different rock samples, it includes: According to the physical parameters of the rock samples, divide the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals. Divide the heavy minerals into a strongly magnetic part and a weakly magnetic part, and further divide the weakly magnetic part into an electromagnetic part and a non-magnetic part. Perform fine washing on the non-magnetic part, and divide the non-magnetic part into a transparent part and an opaque part.

3. The method according to claim 2, wherein In the process of dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, it includes: Crush each rock sample, and obtain the relative density of each crushed rock sample. Thus, use the relative density as the physical parameter of the rock sample to divide the non-carbonate minerals. Among them, the non-carbonate minerals contained in the crushed rock samples with a relative density greater than or equal to / less than a preset density threshold are used as the heavy minerals / light minerals.

4. The method according to claim 2 or 3, characterized in that, In the process of dividing the heavy minerals into a strongly magnetic part and a weakly magnetic part, and further dividing the weakly magnetic part into an electromagnetic part and a non-magnetic part, it includes: Use a strong magnetic separation method to divide the heavy minerals into a strongly magnetic part and a weakly magnetic part; and Use an electromagnetic separation method to divide the weakly magnetic part into an electromagnetic part and a non-magnetic part.

5. The method according to any one of claims 1 to 4, characterized in that After dividing the non-carbonate minerals contained in the corresponding rock samples into heavy minerals and light minerals according to the physical parameters of the rock samples, the method further includes: Perform age determination, fission track, cathodoluminescence, and provenance analysis on the heavy minerals, and obtain the acid-insoluble substances in the light minerals and perform diffraction analysis on them, so as to correct the geological characteristic changes according to the analysis results.

6. The method according to any one of claims 1 to 5, characterized in that, The geological characteristics of the carbonate rock formation to be studied include but are not limited to: sedimentary environment, paleo-water depth, paleo-climate, redox conditions, exposure and erosion status, provenance area and hydrodynamic conditions, unconformity and weathered crust karst, tectonic uplift and erosion, and karstification.

7. The method according to any one of claims 1 to 6, characterized in that The rock samples include but are not limited to: cuttings, cores, or surface outcrops in different tectonic lithofacies belts, cuttings, cores, or surface outcrops in different stratigraphic groups, and cuttings, cores, or surface outcrops in different segments.

8. The method according to claim 7, wherein Before obtaining the types of non-carbonate minerals contained in different rock samples, the method further includes: Perform impurity removal treatment on the cuttings in the different rock samples; and Divide the cores in the different rock samples into matrix and fracture-vug fillings, so that the geological characteristics of the carbonate rock formation to be studied match the actual geological state.

9. The method according to any one of claims 2 to 4, characterized in that the ferromagnetic part includes, but is not limited to: magnetite, pyrrhotite, chalcopyrite, iron platinum ore and native iron; the electromagnetic part includes, but is not limited to: ilmenite, pseud-ilmenite, columbite and monazite.

10. A system for identifying low - order sequence boundaries in carbonate rock formations, characterized in that, The system includes the following modules: a mineral information acquisition module, which is used to acquire the types of non-carbonate minerals contained in different rock samples collected from different positions in the carbonate rock series to be studied, and obtain the content of each type of non-carbonate mineral in the corresponding rock sample; a feature analysis module, which is used to analyze the first change feature of the non-carbonate mineral types with the formation depth and the second change feature of the content of each type of non-carbonate mineral with the formation depth according to the formation depth of different rock samples, and further obtain the geological feature change of the carbonate rock series to be studied based on the analysis results, and based on this, determine the low-order sequence interface in the current carbonate rock series to be studied.

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