Method for identifying sedimentary facies of carbonate rocks and application

Abstract

The invention provides a carbonate rock sedimentary facies identification method and application, and relates to the field of oil exploration and development, and the method comprises the following steps: collecting to-be-analyzed key well target interval sedimentary facies research basic data, seismic profile data and rock debris samples; the method comprises the following steps: grinding a rock debris sample to obtain rock debris flakes, observing and determining carbonate lithofacies characteristics, comparing the carbonate lithofacies characteristics with a standard carbonate rock sedimentary microfacies chart, determining the microfacies type of the rock debris flakes, compiling a sedimentary facies comprehensive histogram in combination with collected sedimentary facies research basic data, and establishing a relative sea level change curve; the collected data are further combined to complete identification of the carbonate rock sedimentary facies; the invention further provides application of the method in carbonate rock geological exploration. The carbonatite sedimentary facies research method is further supplemented and perfected, the problem that carbonatite sedimentary facies analysis data is single in source and difficult to be put into actual production application is solved, and theoretical guidance and technical support are provided for carbonatite oil-gas exploration.

Description

Technical Field

[0001] The present invention belongs to the field of oil exploration and development, and particularly relates to a method for identifying carbonate sedimentary facies and its application. Background Art

[0002] Carbonate sedimentary facies refer to sedimentary systems formed mainly on tropical shelves or beaches due to the action of seawater fluids. The distribution area of marine carbonate strata has gradually become an important oil and gas exploration site. The carbonate model is an important auxiliary tool for understanding the distribution of carbonate facies and, to a certain extent, the distribution of primary porosity and its preservation related to diagenetic history. With the continuous deepening of oil and gas exploration, the distribution area of marine carbonate strata has gradually been regarded as an important oil and gas exploration site.

[0003] However, due to the characteristics of complex and variable petrological and geochemical characteristics, diverse sedimentary environments, relatively complex sedimentation processes and diagenetic effects, susceptibility to the limitations of methods such as geological exploration and geochemical analysis itself, and susceptibility to the subjective factors of researchers when observing and describing sedimentary rocks, it is difficult to accurately identify and divide the carbonate sedimentary facies of the study area using conventional drilling data and seismic data.

[0004] In view of the above problems, a method for identifying carbonate microfacies is provided in the prior art. Patent application CN110275210A provides a method for identifying the sedimentary microfacies pattern of a carbonate high-frequency sequence framework. The method includes: determining a lithology-sensitive logging curve using a core sample of the carbonate target layer and a conventional logging curve; determining a triple porosity logging curve combination based on the resistivity logging curve combination; identifying low-frequency sequence boundaries according to the lithology-sensitive logging curve, the triple porosity logging curve combination, and the resistivity logging curve combination; identifying high-frequency sequence boundaries based on the low-frequency sequence boundaries; analyzing the division of single-well sedimentary subfacies and microfacies; and completing the comparison and division of sedimentary microfacies in the entire well section. This method has strong operability, conforms to the principles of sequence stratigraphy and sedimentology, can accurately establish a static and dynamic combined sedimentary microfacies pattern with high-frequency sequences as the constraint and division unit, and conduct sedimentary evolution analysis; however, it is limited to the identification of the facies pattern of sedimentary microfacies, and the data sources used are relatively single, resulting in its difficulty in being used for overall analysis of carbonate sedimentary facies.

[0005] Patent application CN114442192A provides a method and system for fine restoration of carbonate lithofacies paleogeography based on sequence stratigraphy, specifically including: (1) comprehensively collecting outcrop and drilling data in the study area and differentiating the data quality. (2) Sorting out the regional geological background of the study area; (3) Fine calibration of sequence boundaries, that is, fully utilizing data such as conventional logging, imaging logging, core, cuttings or seismic synthetic records, and dividing sequence boundaries according to evidence of cyclic stratigraphy, lithology and lithofacies, unconformity surfaces and corresponding conformity surfaces; (4) Establishing a sequence stratigraphic framework; (5) Making a crossplot of grain-to-ground ratio and formation thickness; (6) Restoring sedimentary paleogeomorphology; (7) Studying sedimentary facies and symbiotic associations; (8) Studying the spatio-temporal distribution law of sedimentary facies; (9) Reconstructing the sequence-lithofacies paleogeography of key time sections at each stratigraphic horizon. The present invention overcomes the defects existing in the current lithofacies paleogeography restoration method and improves the accuracy of lithofacies paleogeography restoration; although it adopts multi-source data and a hierarchical analysis method, the present invention is mainly used for fine restoration of paleogeography and is difficult to be directly used in existing resource exploration and development. At the same time, the present invention does not give any technical solutions available in actual oil exploration and development.

[0006] Therefore, how to supplement the carbonate sedimentary microfacies identification method and provide a method for identifying carbonate sedimentary facies that can be applied to actual production is one of the important issues studied by those skilled in the art. Summary of the Invention

[0007] Aiming at the problems existing in the prior art that the data sources for carbonate sedimentary facies analysis are single or difficult to be applied to actual production, the present invention provides a method for identifying carbonate sedimentary microfacies, which further supplements the carbonate sedimentary facies identification method.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for identifying carbonate sedimentary facies includes the following steps:

[0010] S1. Collect basic data on sedimentary facies research and seismic profile data of the target interval of the key well to be analyzed;

[0011] S2. Collect cuttings samples of the target interval of the key well to be analyzed;

[0012] S3. Grind the cuttings samples obtained in step S2 to obtain cutting thin sections;

[0013] S4. Observe the cutting thin sections obtained in step S3 to clarify the petrographic characteristics of carbonate rocks;

[0014] S5. Compare the petrographic features identified in step S4 with the standard carbonate sedimentary microfacies plates to determine the microfacies types of the cuttings thin sections ground in step S3;

[0015] S6. Combine the microfacies types determined in step S5 with the basic sedimentary facies research data collected in step S1 to compile a comprehensive sedimentary facies columnar diagram for the entire well section and the cored well section of the key well;

[0016] S7. Establish a relative sea level change curve based on the vertical stacking relationship of sedimentary facies in the comprehensive sedimentary facies columnar diagram of the entire well section and the cored well section of the key well compiled in S6;

[0017] S8. Based on the relative sea level change curve established in step S7, further combine the basic sedimentary facies research data and seismic profile data collected in step S1 to complete the identification of carbonate sedimentary facies.

[0018] Preferably, the basic sedimentary facies research data in step S1 includes element logging data, comprehensive logging data, core data, and cuttings data.

[0019] More preferably, the element logging data includes logging element data and reservoir fluid element content data.

[0020] Even more preferably, the comprehensive logging data includes lithology parameters, reservoir fluid parameters, formation pressure parameters, and geological origin parameters;

[0021] The lithology parameters include density, acoustic velocity, neutron porosity, and natural gamma radiation;

[0022] The reservoir fluid parameters include resistivity and natural gamma radiation;

[0023] The formation pressure parameters include pore pressure and bottom hole pressure;

[0024] The geological origin parameters include natural gamma radiation and gamma detection.

[0025] Most preferably, the cuttings data are the rock fragments (2 - 5 mm) brought to the surface with the mud circulation after the drill bit breaks the formation during drilling;

[0026] Observing the cuttings thin sections includes observing the types and contents of cuttings, the characteristics of cuttings particles, the composition of cuttings, and the arrangement and structure of cuttings;

[0027] The characteristics of cuttings particles include the shape, size, and grain size distribution of cuttings particles;

[0028] The composition of cuttings includes the mineral composition and chemical characteristics of cuttings;

[0029] The arrangement and structure of the cuttings include the arrangement of the cutting particles, the porosity of the cuttings, and the degree of cementation.

[0030] Preferably, the method for collecting the cutting samples in step S2 is: selecting at a longitudinal spacing of 2 m.

[0031] More preferably, the selection is to remove the fragile mud impurities and retain the hard and large carbonate cutting samples.

[0032] Preferably, the tool for observation in step S4 is a microscope.

[0033] More preferably, the observation of the cutting thin section includes observing the types and contents of the cuttings, the characteristics of the cutting particles, the composition of the cuttings, and the arrangement and structure of the cuttings.

[0034] Preferably, the petrographic characteristics in step S4 include the rock particle components and their proportions and the content of bioclasts.

[0035] The standard carbonate sedimentary microfacies chart in step S5 refers to a reference chart or standard version used to describe and classify rock microfacies, usually formulated and compiled jointly by geologists and petrographers. Microfacies refers to the characteristics of rock components, structures, and sedimentary systems at the microscopic scale in rocks, used to study the origin of rocks, lithological characteristics, and sedimentary history.

[0036] The standard microfacies chart usually contains a series of optical microscope images, showing the typical microfacies characteristics under different rock types and sedimentary environments. These images can be used for reference and identification of microfacies characteristics in rock samples, such as the size and shape of mineral particles, the arrangement of particles, the degree of cementation, fractures, and pores. The standard microfacies chart can also provide some descriptive text information, such as the interpretation and definition of rock types, sedimentary environments, and petrological characteristics.

[0037] The establishment of the relative sea-level change curve according to the vertical superposition relationship in step S7 means that by analyzing the stacking sequence and superposition relationship between different sedimentary facies, inferring the change trend of the relative sea level in different periods, and drawing a curve of the relative sea-level change.

[0038] In a geological section or well, the superposition relationship of different sedimentary facies can provide the relative order of stratigraphic superposition, thereby inferring the rise and fall changes of the relative sea level in each period. By analyzing the relative sea-level change curve, the change trend of the sea level in geological history can be understood, and then the changes in the sediment source area, the development of paleogeomorphology, and the changes in sedimentary environment can be speculated.

[0039] By establishing a relative sea - level change curve, it can help understand the sea - level change process in geological history, thereby interpreting and predicting sedimentary sequences, sedimentary facies evolution, lithofacies paleogeography, geological resource distribution, etc. During the process of oil and gas exploration and development, the relative sea - level change curve can also be used as a reference for the distribution of regional oil and gas reservoirs, helping to determine the preferred exploration target areas and formulate development strategies.

[0040] Preferably, the identification method described in step S8 includes the following steps:

[0041] Based on the seismic profile data described in step S1, calibrate the stratigraphic framework of the layer to be analyzed by combining well and seismic data;

[0042] Further, by combining comprehensive logging and element logging data, establish sedimentary facies correlation analysis between single wells in the target layer section, and reconstruct the sedimentary pattern of the study area.

[0043] The present invention also provides an application of the above - mentioned method for identifying carbonate sedimentary facies in carbonate geological exploration.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention realizes the supplement of the conventional method for identifying carbonate sedimentary facies, establishes a method for identifying and dividing carbonate sedimentary microfacies in the study area using cuttings data, and realizes the accurate identification and division of carbonate sedimentary facies in the study area under similar geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for identifying carbonate sedimentary facies according to an embodiment of the present invention;

[0047] Figure 2 It is a comprehensive columnar diagram of sedimentary facies in the coring section of the key well. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] Embodiment A method for identifying carbonate sedimentary facies

[0049] The embodiments of the present disclosure provide a method for identifying and dividing carbonate sedimentary facies, including:

[0050] Step S1: Collect basic data on sedimentary facies research for the target layer section of the key well to be analyzed;

[0051] Specifically, conduct data analysis and research on the area to be analyzed, select key wells, and collect basic data on sedimentary facies research. The basic data on sedimentary facies research includes element logging data, comprehensive logging data, core data, and cuttings data;

[0052] Element logging mainly includes the following measurements and analyses:

[0053] 1. Rock element content analysis: By measuring the content of specific elements in rocks, the rock composition and chemical properties can be understood. The specific elements include major elements (such as aluminum, calcium, silicon), trace elements (such as manganese, chromium, strontium), and rare earth elements.

[0054] 2. Reservoir fluid element content analysis: By measuring the element content in reservoir fluids, the composition, source, and properties of the fluids can be determined. The elements measured include chlorine, sodium, potassium in water, and sulfur, nickel, cobalt in oil.

[0055] 3. Correlation analysis between elements: By analyzing the correlation and ratio between different elements, information on the geological history, genetic pattern, and fluid migration pattern of rocks and fluids can be revealed.

[0056] The measurement parameters of comprehensive logging data include the following aspects:

[0057] 1. Lithology parameters: Include density, acoustic velocity, neutron porosity, natural gamma radiation. By measuring these parameters, the physical properties, porosity, and saturation information of rocks can be inferred.

[0058] 2. Reservoir fluid parameters: Include resistivity, natural gamma radiation. By measuring these parameters, the oil, water, gas content, and fluid saturation in the reservoir can be inferred.

[0059] 3. Formation pressure parameters: Include pore pressure, bottom hole pressure, etc. By measuring and analyzing formation pressure parameters, the reservoir pressure state and fluid migration characteristics can be inferred.

[0060] 4. Geological genetic parameters: Include natural gamma radiation, gamma detection, etc. By measuring these parameters, the rock genesis, sedimentary environment, and tectonic characteristics can be inferred.

[0061] The content of cuttings data analysis includes the following aspects:

[0062] 1. Types and contents of cuttings: Classify and count different types of cuttings in rock samples to obtain the percentage content of different cuttings. Common types of cuttings include quartz, feldspar, cuttings gravel, carbonate cuttings, cuttings gravel, volcanic debris.

[0063] 2. Characteristics of cuttings particles: Describe the characteristics of cuttings particles such as shape, size, grain size distribution, etc. These characteristics can provide information on the genesis, mechanical properties, particle movement, and sedimentary environment of rocks.

[0064] 3. Composition of cuttings: Determine the mineral composition and chemical characteristics of cuttings particles through cuttings identification and chemical composition analysis. This can help understand the composition of rocks, petrological characteristics, and diagenetic environment information.

[0065] 4. Arrangement and structure of cuttings: Describe the arrangement pattern of cutting particles (such as layered, homogeneous) and structural characteristics (such as porosity, cementation degree) to infer sedimentary environment and fluid permeability information.

[0066] The analysis of cutting data needs to be carried out by observing and analyzing under a microscope of rock samples.

[0067] Step S2: Collect cutting samples in the area to be analyzed in the key wells

[0068] In the target interval to be analyzed in the key wells of the study area, select cutting samples at an interval of 2m; further, sieve out large particles and fragile mud impurities, and retain hard and relatively large carbonate rock cutting samples.

[0069] Step S3: Grind the cutting samples obtained in Step S2 to obtain cutting thin sections;

[0070] Step S4: Observe the cutting thin sections obtained in Step S3 to clarify petrographic characteristics;

[0071] Step S5: Based on the petrographic characteristics clarified in Step S4, compare with the standard carbonate sedimentary microfacies chart (Flügel, 2004) to determine the microfacies type of the cutting thin sections.

[0072] Step S6: According to the sedimentary microfacies type combination of the cutting thin sections determined in Step S5, combined with comprehensive logging data and element logging data, identify the sedimentary facies type of the target interval to be analyzed in the key wells, and compile a comprehensive sedimentary facies columnar chart for the entire well section and the cored interval of a single well, as Figure 2 shown.

[0073] Step S7: According to the vertical superposition relationship of sedimentary facies in the comprehensive sedimentary facies columnar chart of the entire well section and the target interval to be analyzed compiled in Step S6, establish a relative sea level change curve, as Figure 2 shown.

[0074] Step S8: According to the relative sea level change curve established in Step S7, further combined with the basic data of sedimentary facies research and seismic profile data collected in Step S1, complete the identification of carbonate sedimentary facies.

[0075] The implementation and data source of this embodiment are Well Shunnan 4-1 in the Shuntuogole area of Tazhong, realizing the effective identification of carbonate sedimentary facies.

[0076] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Any simple modification or equivalent replacement made by those of ordinary skill in the art to the technical solution of the present invention does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for identifying carbonate sedimentary facies, characterized in that It includes the following steps: S1. Collect the basic data of sedimentary facies study and seismic profile data of the target interval of the key wells to be analyzed; S2. Collect the cuttings samples of the target interval of the key wells to be analyzed; S3. Grind the cuttings samples obtained in step S2 to obtain thin sections of cuttings; S4. Observe the thin sections of cuttings obtained in step S3 to clarify the petrographic characteristics of carbonate rocks; S5. Compare the petrographic characteristics clarified in step S4 with the standard carbonate sedimentary microfacies plate to determine the microfacies type of the thin sections of cuttings ground in step S3; S6. Combine the microfacies type determined in step S5 with the basic data of sedimentary facies study collected in step S1 to compile a comprehensive sedimentary facies columnar diagram of the whole well section and the cored well section of the key wells; S7. Establish a relative sea level change curve according to the vertical superimposition relationship of sedimentary facies in the comprehensive sedimentary facies columnar diagram of the whole well section and the cored well section of the key wells compiled in S6; S8. According to the relative sea level change curve established in step S7, further combine the basic data of sedimentary facies study and seismic profile data collected in step S1 to complete the identification of carbonate sedimentary facies.

2. The method according to claim 1, wherein The basic data of sedimentary facies study described in step S1 includes element logging data, comprehensive logging data, core data and cuttings data.

3. The method according to claim 2, characterized in that, The element logging data includes logging element data and reservoir fluid element content data.

4. The method according to claim 2, wherein The comprehensive logging data includes lithology parameters, reservoir fluid parameters, formation pressure parameters and geological origin parameters.

5. The method according to claim 4, wherein The lithology parameters include density, acoustic velocity, neutron porosity and natural gamma radiation.

6. The method according to claim 4, wherein The reservoir fluid parameters include resistivity and natural gamma radiation.

7. The method according to claim 4, characterized in that, The formation pressure parameters include pore pressure and bottom hole pressure.

8. The method according to claim 4, wherein The geological origin parameters include natural gamma radiation and gamma detection.

9. The method according to claim 2, wherein The cuttings data are rock fragments brought to the surface with the mud circulation after the drill bit breaks the formation during drilling, with a size of 2-5 mm.

10. The method according to claim 1, wherein The method for collecting the cuttings samples described in step S2 is: select at a longitudinal interval of 2 m.

11. The method according to claim 10, characterized in that The selection is to remove the fragile mud impurities and retain the hard and large carbonate cuttings samples.

12. The method according to claim 1, wherein The observation of the thin sections of cuttings described in step S4 includes observing the types and contents of cuttings, the characteristics of cuttings particles, the composition of cuttings and the arrangement and structure of cuttings.

13. The method according to claim 1, characterized in that The petrographic characteristics described in step S4 include the rock particle components and their proportions and the content of bioclasts.

14. The method according to claim 1, wherein The identification method described in step S8 includes the following steps: Based on the seismic profile data described in step S1, calibrate the stratigraphic framework of the interval to be analyzed by combining well and seismic data; Further combine the comprehensive logging and element logging data to establish a sedimentary facies contrast analysis between single wells in the target interval and reconstruct the sedimentary pattern of the study area.

15. Application of the method according to any one of claims 1-14 in carbonate geological exploration.

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