A Comprehensive Grading and Evaluation Method for Delta Sand-Rich Lithological Traps

Abstract

This invention relates to a comprehensive grading and evaluation method for deltaic sand-rich lithological traps, belonging to the field of petroleum exploration and development technology. The invention discloses a comprehensive grading and evaluation method for deltaic sand-rich lithological traps, including obtaining the geological background, core data, development data, well logging data, and seismic data of the target area; establishing a high-frequency sequence stratigraphic framework; characterizing sedimentary microfacies; predicting the thickness distribution of sand bodies and mudstones; determining the evaluation value of the lateral boundary of the lithological trap; determining the evaluation value of the caprock conditions of the lithological trap; determining the comprehensive trap score based on the evaluation values ​​of the lateral boundary and caprock conditions of the lithological trap, and performing a grading evaluation. This invention mainly establishes a high-frequency sequence stratigraphic framework, utilizes various geophysical techniques, establishes relevant evaluation processes and standards, and grades the lateral conditions and caprock conditions of lithological targets from geological, geophysical, and quantitative mudstone thickness perspectives, performing a semi-quantitative evaluation.

Description

Technical Field

[0001] This invention relates to a comprehensive classification and evaluation method for deltaic sand-rich lithological traps, belonging to the field of petroleum exploration and development technology. Background Technology

[0002] As offshore oil and gas exploration deepens, the main exploration focus has gradually shifted from structural traps to lithological traps. The geological conditions for the formation of lithological traps are becoming clearer, and comprehensive analysis of trap targets is becoming the core of lithological trap exploration. Traps typically consist of three parts: reservoir, caprock, and lateral shielding conditions. Early structural trap exploration focused on identifying large-scale, contiguous sand bodies and exploring at structural highs along the oil and gas migration direction, primarily focusing on the reservoir and caprock. Lateral shielding conditions were mainly defined by structural spillways. However, lithological traps are formed by changes in the lithology and physical properties of the reservoir, making lateral shielding conditions particularly important. Therefore, understanding the lateral boundaries of lithological traps is a key issue restricting current exploration progress. Summary of the Invention

[0003] The purpose of this invention is to provide a comprehensive classification and evaluation method for deltaic sand-rich lithological traps, addressing the problems existing in the prior art.

[0004] The technical solution provided by this invention to solve the above-mentioned technical problems is: a comprehensive classification and evaluation method for deltaic sand-rich lithological traps, comprising the following steps:

[0005] Step S10: Obtain the geological background, core data, development data, logging data, and seismic data of the target work area;

[0006] Step S20: Establish a high-frequency sequence stratigraphic framework;

[0007] Step S30: Characterize the sedimentary microfacies;

[0008] Step S40: Predict the thickness distribution of sandstone and mudstone bodies;

[0009] Step S50: Determine the geological evaluation value a1, the geophysical evaluation value a2, and the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap, respectively.

[0010] Step S60: Determine the lateral boundary evaluation value S1 of the lithological trap based on the geological evaluation value a1 of the lateral boundary of the lithological trap, the geophysical evaluation value a2 of the lateral boundary of the lithological trap, and the quantitative characterization evaluation value a3 of the mudstone of the lateral boundary of the lithological trap.

[0011] Step S70: Determine the geological evaluation value b1 and the geophysical evaluation value b2 of the lithological trap cover condition, respectively.

[0012] Step S80: Determine the evaluation value S2 of the lithological closure and capping strata condition based on the geological evaluation value b1 and the geophysical evaluation value b2 of the lithological closure and capping strata condition.

[0013] Step S90: Determine the comprehensive score value S of the trap based on the evaluation value S1 of the lithological trap lateral boundary and the evaluation value S2 of the lithological trap cap layer condition, and conduct a graded evaluation.

[0014] A further technical solution is that the specific steps of step S20 are as follows:

[0015] Step S21: Select relevant sequence stratigraphy theories based on the geological background of the target work area and establish a high-frequency sequence stratigraphy scheme;

[0016] Step S22: Create synthetic records for well-seismic calibration, clarify the reflection characteristics of high-frequency sequence interfaces in seismic profiles, and perform interpretation and tracing of the entire area to establish a high-frequency sequence stratigraphic framework for the entire area.

[0017] A further technical solution is that the specific process of step 30 is as follows:

[0018] Step S31: Based on the marine delta sedimentary model, identify typical sedimentary structures on the core, establish a sedimentary microfacies division scheme for the target work area, clarify the lithological and electrical characteristics of each sedimentary microfacies, and establish a rock-electrical-seismic sedimentary transformation map.

[0019] Step S32: Based on the established sedimentary transformation template, interpret the sedimentary microfacies of a single well according to the core photographs, the differences in electrical characteristics of different microfacies, and the vertical combination of lithology.

[0020] Step S33: Based on the well-seismic calibration results, select appropriate seismic attributes for extraction, and extract the corresponding RGB fusion attributes for frequency division.

[0021] Step S34: Under the guidance of the sedimentary model, the sedimentary microfacies are characterized based on the interpretation of single-well-to-well facies, single seismic attributes, and frequency-division RGB fusion attributes.

[0022] A further technical solution is that the specific process of step 40 is as follows:

[0023] Step S41: Select 17 types of seismic attributes, including amplitude, statistics, waveform, and frequency, and extract them. Then, perform correlation analysis with the surface statistical sand body thickness.

[0024] Step S42: Select the best seismic attributes and predict the plane distribution map of sand body thickness;

[0025] Step S43: Obtain the mudstone thickness plane distribution map based on the top and bottom of the target sand body and the plane distribution map of the sand body thickness.

[0026] A further technical solution is that, in step S50, when the distance from the subfacies boundary is >5km and the sea level is rising, the geological evaluation value a1 of the lateral boundary of the lithological trap is 100; when the distance from the subfacies boundary is -5 to 5km and the sea level rise and fall are relatively stable, the geological evaluation value a1 of the lateral boundary of the lithological trap is 80; when the distance from the subfacies boundary is <-5km and the sea level is falling, the geological evaluation value a1 of the lateral boundary of the lithological trap is 60.

[0027] When there is obvious dislocation of the lateral phase axis, clear changes in the strength of conventional properties, and the boundary of the frequency-division RGB attribute is gray-black, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 100; when the lateral phase axis shows weakening characteristics, the strong amplitude of conventional properties gradually transitions to weak amplitude, and the color of the frequency-division RGB attribute changes from green to gray, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 80; when there is no obvious change in the lateral phase axis, the changes in conventional properties are slight, and the color of the frequency-division RGB attribute boundary is yellowish-red, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 60.

[0028] When the lateral mudstone thickness is >15m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 100; when the lateral mudstone thickness is 8-15m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 80; when the lateral mudstone thickness is <8m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 60.

[0029] A further technical solution is that the calculation formula in step S60 is:

[0030] S1 = 0.3a1 + 0.3a2 + 0.4a3

[0031] In the formula: S1 is the evaluation value of the lateral boundary of the lithological trap; a1 is the geological evaluation value of the lateral boundary of the lithological trap; a2 is the geophysical evaluation value of the lateral boundary of the lithological trap; a3 is the quantitative characterization evaluation value of the mudstone at the lateral boundary of the lithological trap.

[0032] A further technical solution is that, in step S70, when the flooding level is a third- or fourth-order flooding level and the caprock sedimentary subfacies belongs to the pre-deltaic-shallow marine facies, the geological evaluation value b1 for the lithological trap caprock condition is 100; when the flooding level is a fifth-order flooding level and the caprock sedimentary subfacies belongs to the outer delta front, the geological evaluation value b1 for the lithological trap caprock condition is 80; when the flooding level is a higher-order flooding level and the caprock sedimentary subfacies belongs to the inner delta front, the geological evaluation value b1 for the lithological trap caprock condition is 60.

[0033] When the continuity of the same phase axis is good and the mudstone thickness is >10m, the geophysical evaluation value of the lithological trap cap condition is b2=100; when the continuity of the same phase axis is moderate and the mudstone thickness is 5-10m, the geophysical evaluation value of the lithological trap cap condition is b2=80; when the continuity of the same phase axis is poor and the mudstone thickness is <5m, the geophysical evaluation value of the lithological trap cap condition is b2=60.

[0034] A further technical solution is that the calculation formula in step S80 is:

[0035] S2 = 0.5b1 + 0.5b2

[0036] In the formula: S2 is the evaluation value of the lithological trap cover condition; b1 is the geological evaluation value of the lithological trap cover condition; b2 is the geophysical evaluation value of the lithological trap cover condition.

[0037] A further technical solution is that the calculation formula in step S90 is:

[0038] S = 0.7S1 + 0.3S2

[0039] In the formula: S2 is the evaluation value of the lithological trap cap layer condition; S1 is the evaluation value of the lithological trap lateral boundary; S is the comprehensive score value of the trap.

[0040] A further technical solution is that, in step S90, when 90 ≤ the comprehensive score value S ≤ 100, the risk level is extremely low.

[0041] When 70 < the comprehensive score S of the trap is less than 90, the risk level is low.

[0042] When 50 ≤ comprehensive score S ≤ 70, the risk level is relatively high.

[0043] When 0 < the comprehensive score S of the trap is less than 50, the risk level is extremely high.

[0044] The beneficial effects of this invention are as follows: This invention mainly establishes a high-frequency sequence stratigraphic framework, uses various geophysical techniques, establishes relevant evaluation processes and standards, and conducts a graded and semi-quantitative evaluation of the lateral conditions and caprock conditions of lithological targets from the aspects of geology, geophysics, and quantitative mudstone thickness. Attached Figure Description

[0045] Figure 1 This is a flowchart of the present invention;

[0046] Figure 2 To form a high-frequency sequence stratigraphic framework based on different levels of flooding surfaces;

[0047] Figure 3 A rock-electrodeposition phase transition diagram;

[0048] Figure 4 Microfacies depiction of deltaic sediments;

[0049] Figure 5 To predict sandstone / mudstone thickness maps;

[0050] Figure 6 Profile of well Z28, a potential lithological target;

[0051] Figure 7 Line 1 diagram shows the lateral boundary evaluation profile for potential lithological target Z28.

[0052] Figure 8 Delineate a plan view for potential lithological targets;

[0053] Figure 9 Line 2 is the evaluation profile of the potential lithological target Z28 caprock. Detailed Implementation

[0054] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] like Figure 1 As shown, the present invention provides a comprehensive classification and evaluation method for deltaic sand-rich lithological traps, comprising the following steps:

[0056] Step S10: Obtain the geological background, core data, development data, logging data, and seismic data of the target work area;

[0057] Step S20: Establish a high-frequency sequence stratigraphic framework;

[0058] Step S21: Select relevant sequence stratigraphy theories based on the geological background of the target work area and establish a high-frequency sequence stratigraphy scheme;

[0059] The target work area is located in a relatively wide and gentle mid-continental shelf region, which is a marine deltaic sedimentary system. Frequent rises and falls of sea level have caused the delta to advance and retreat in the horizontal plane, forming a large set of interbedded sandstone and mudstone in the vertical direction. The interaction between isolated sand bodies and prodeltaic mudstone in the outer edge region is conducive to the formation of lithological traps.

[0060] Different levels of sea-level rise and fall have led to the formation of multi-stage deltas and different levels of transgression surfaces. Therefore, transgression interfaces at different scales (fourth-order transgression, fifth-order transgression) are selected as boundaries to establish a high-frequency sequence stratigraphic framework. The maximum transgression and higher-order transgression interfaces control the formation and distribution of caprock and mudstone interlayers, and can provide caprock and lateral shielding conditions for lithological traps.

[0061] Meanwhile, different levels of transgression surfaces exhibit distinct drilling characteristics. The largest transgression surface corresponds to a large section of thick mudstone (thickness > 20m), serving as a regional transgression interface, encountered throughout the entire area. At the fourth-order transgression interface, a set of high-GR mudstone is developed, with a large mudstone layer above the interface (sand-to-soil ratio: 0–0.55), and relatively well-developed sand bodies below the interface (sand-to-soil ratio: 0–0.79). The encounter rate is approximately 80-100%, and it can be interpreted and compared regionally. At the fifth-order transgression interface, a set of high-GR mudstone is developed, with mudstone thickness varying across different well areas: 3-6m in well X1 near the source area, 4-10m in well X2, and 10-18m in well H1, with an encounter rate of approximately 60-80%. Some interfaces can be traced and interpreted. Based on the lithological, electrical, and cyclic characteristics of the drilling data, high-frequency sequence stratigraphy of single wells is divided, and sequence stratigraphy and comparison of interconnected wells throughout the area are also performed.

[0062] Step S22: Create synthetic records for well-seismic calibration, clarify the reflection characteristics of high-frequency sequence interfaces in seismic profiles, and perform interpretation and tracing of the entire area to establish a high-frequency sequence stratigraphic framework for the entire area.

[0063] The maximum transgression surface is characterized by strong amplitude, low frequency, and good continuity on seismic profiles. Locally, under-contact relationships are identifiable above the interface. Significant differences in seismic facies exist between the surface and the interface. Below the interface lies thick sandstone with strong amplitude, low frequency, and moderate continuity, while above it are thin interbedded sandstone and mudstone with medium to weak amplitude, high frequency, and good continuity. The seismic phase axes of the fourth-order transgression surface generally exhibit medium to strong amplitude and moderate to good continuity. Progradational reflection characteristics are visible below the interface, while under-contact relationships are locally visible above it. The fifth-order transgression interface is difficult to track and correlate over a large area on seismic profiles. The seismic phase axes generally exhibit medium amplitude and moderate continuity, and can only be tracked locally on seismic profiles, primarily relying on well-seismic correlation for calibration. The characteristics of transgression interfaces at each order should be clearly defined, tracked and interpreted throughout the region, and a high-frequency sequence stratigraphic framework should be established for the entire region.

[0064] Step S30: Characterize the sedimentary microfacies;

[0065] Step S31: Based on the marine delta sedimentary model, identify typical sedimentary structures on the core, establish a sedimentary microfacies division scheme for the target work area, clarify the lithological and electrical characteristics of each sedimentary microfacies, and establish a rock-electrical-seismic sedimentary transformation map.

[0066] In this embodiment, the development of braided river deltas is significantly affected by sea level rise and fall. During the period of sea level drop, the river effect is significant, and the tributary channels extend continuously to the sea over a long distance. During the period of sea level rise, the early-formed tributary channels and estuary bars are modified by hydrodynamics, resulting in modified sand bodies with a discontinuous southwest-trending distribution.

[0067] Therefore, the delta front can be subdivided into the inner delta front and the outer delta front. The inner delta front mainly develops continuously distributed underwater distributary channels, inter-distributary bays, and mouth bars, while the outer delta front mainly develops discontinuously developed mouth bars, distal bars, distal bar flanks, and sheet sands.

[0068] Step S32: Based on the established sedimentary transformation template, interpret the sedimentary microfacies of a single well according to the core photographs, the differences in electrical characteristics of different microfacies, and the vertical combination of lithology.

[0069] In this embodiment, with the frequent rise and fall of sea level, the delta undergoes multiple phases of migration and oscillation in the lateral direction, and the sand body stacking pattern is complex in the longitudinal direction.

[0070] Step S33: Based on the well-seismic calibration results, select appropriate seismic attributes for extraction, and extract the corresponding RGB fusion attributes for frequency division.

[0071] In this embodiment, the thin sand body has a good correspondence with the trough after the -90° phase transition, so the minimum amplitude attribute is selected for extraction. Simultaneously, based on the sand body thickness statistically obtained from the wellbore, and the response tuning thickness λ / 4, 16Hz, 35Hz, and 56Hz are selected as the low, medium, and high frequency bands, respectively.

[0072] Step S34: Under the guidance of the sedimentary model, the sedimentary microfacies are characterized based on the interpretation of single-well-to-well facies, single seismic attributes, and frequency-division RGB fusion attributes.

[0073] The single-well facies and interconnected-well facies of drilled wells serve as the most powerful evidence for judging sedimentary microfacies. By combining the distribution characteristics of single attributes and frequency-division RGB fusion attributes on the plane, a fine sedimentary microfacies characterization is carried out to clarify its planar distribution characteristics.

[0074] Among these methods, the most common and simplest is to select the seismic attributes with the highest correlation to well logging interpretation through correlation analysis. This method is often applied to blocks with well drilling, and essentially uses some mathematical method to calibrate and optimize seismic information based on well logging information. The purpose of attribute optimization is to improve the accuracy and reliability of the prediction model. By selecting seismic attributes closely related to the target reservoir, we can optimize the prediction model, reduce unnecessary attributes and data complexity, and improve the accuracy and efficiency of prediction.

[0075] Step S40: Predict the thickness distribution of sandstone and mudstone bodies;

[0076] Step S41: Select 17 types of seismic attributes, including amplitude, statistics, waveform, and frequency, and extract them. Then, perform correlation analysis with the surface statistical sand body thickness.

[0077] Step S42: Select the best seismic attributes and predict the plane distribution map of sand body thickness;

[0078] Seismic attribute fusion is a commonly used analytical method that integrates multiple seismic attributes through mathematical operations to more comprehensively and reliably reflect the characteristics of geological bodies. In deltaic sand body prediction, multi-attribute comprehensive analysis is crucial, as it can overcome the limitations of seismic attributes and reduce ambiguity. By utilizing machine learning algorithms, the correlations and weights between seismic attributes can be automatically learned, thus enabling more accurate fusion of multiple attributes. In this embodiment, six seismic attributes with good correlations are selected, and various mainstream algorithms, such as random forests, support vector machines, augmented regression trees, and artificial neural networks, are compared. Considering the correlation between each model and the planar imaging effect as constraints, the most suitable algorithm is selected for fusion prediction, ultimately yielding a predicted planar distribution map of sand body thickness.

[0079] Step S43: Obtain the mudstone thickness distribution map based on the top and bottom of the target sand body and the plane distribution map of the sand body thickness.

[0080] In deltaic sedimentary environments, the lithology is typically interbedded sandstone and mudstone. Therefore, the mudstone thickness distribution can be obtained by subtracting the sandstone thickness from the stratigraphic thickness. By tracing the top and bottom of the target sand body, the stratigraphic thickness of the target layer is obtained. Then, the predicted sand body thickness is subtracted to obtain a planar distribution map of the mudstone thickness.

[0081] Step S50: Determine the geological evaluation value a1, the geophysical evaluation value a2, and the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap, respectively.

[0082] Specifically, when the distance from the subfacies boundary is >5km and the sea level is rising, the geological evaluation value a1 of the lateral boundary of the lithological trap is 100; when the distance from the subfacies boundary is -5 to 5km and the sea level rise and fall are relatively stable, the geological evaluation value a1 of the lateral boundary of the lithological trap is 80; when the distance from the subfacies boundary is <-5km and the sea level is falling, the geological evaluation value a1 of the lateral boundary of the lithological trap is 60.

[0083] In this embodiment, taking the potential lithological target Z28 as an example, it is 1.23 km away from the subfacies boundary and the sea level is in a stable period. Therefore, the geological evaluation value a1 of the lateral boundary of the lithological trap is 80.

[0084] When there is obvious dislocation of the lateral phase axis, clear changes in the strength of conventional properties, and the boundary of the frequency-division RGB attribute is gray-black, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 100; when the lateral phase axis shows weakening characteristics, the strong amplitude of conventional properties gradually transitions to weak amplitude, and the color of the frequency-division RGB attribute changes from green to gray, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 80; when there is no obvious change in the lateral phase axis, the changes in conventional properties are slight, and the color of the frequency-division RGB attribute boundary is yellowish-red, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 60.

[0085] In this embodiment, taking the potential lithological target Z28 as an example, the lateral phase axis on the seismic profile shows obvious discontinuity and weakening, the conventional properties clearly change from strong amplitude to weak amplitude, and the color of the frequency-division RGB attribute changes from green to gray-black. Therefore, the geophysical evaluation value a2 of the lateral boundary of the lithological trap is 100.

[0086] When the lateral mudstone thickness is >15m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 100; when the lateral mudstone thickness is 8-15m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 80; when the lateral mudstone thickness is <8m, the quantitative characterization evaluation value a3 of the mudstone at the lateral boundary of the lithological trap is 60.

[0087] In this embodiment, taking the potential lithological target Z28 as an example, the lateral mudstone thickness ranges from 6 to 13 m. Therefore, the quantitative characterization evaluation value of mudstone at the lateral boundary of the lithological trap is a3 = 80.

[0088] Step S60: Determine the lateral boundary evaluation value S1 of the lithological trap based on the geological evaluation value a1 of the lateral boundary of the lithological trap, the geophysical evaluation value a2 of the lateral boundary of the lithological trap, and the quantitative characterization evaluation value a3 of the mudstone of the lateral boundary of the lithological trap.

[0089] S1 = 0.3a1 + 0.3a2 + 0.4a3

[0090] In the formula: S1 is the evaluation value of the lateral boundary of the lithological trap; a1 is the geological evaluation value of the lateral boundary of the lithological trap; a2 is the geophysical evaluation value of the lateral boundary of the lithological trap; a3 is the quantitative characterization evaluation value of the mudstone at the lateral boundary of the lithological trap.

[0091] In this embodiment, the lithological trap lateral boundary evaluation value S1 of Z28 is 86;

[0092] Step S70: Determine the geological evaluation value b1 and the geophysical evaluation value b2 of the lithological trap cover condition, respectively.

[0093] When the floodplain is at the third or fourth order and the caprock sedimentary subfacies belongs to the pre-deltaic to shallow marine facies, the geological evaluation value b1 for lithological trap caprock conditions is 100; when the floodplain is at the fifth order and the caprock sedimentary subfacies belongs to the outer delta front, the geological evaluation value b1 for lithological trap caprock conditions is 80; when the floodplain is at a higher order and the caprock sedimentary subfacies belongs to the inner delta front, the geological evaluation value b1 for lithological trap caprock conditions is 60.

[0094] In this embodiment, taking the potential lithological target Z28 as an example, the flooding level is a fourth-order flooding level, and the cap layer subfacies type is pre-deltaic. Therefore, the geological evaluation value of the lithological trap cap layer condition is b1 = 100.

[0095] When the continuity of the phase axis is good and the mudstone thickness is >10m, the geophysical evaluation value of the lithological trap cover condition b2 = 100; when the continuity of the phase axis is moderate and the mudstone thickness is 5-10m, the geophysical evaluation value of the lithological trap cover condition b2 = 80; when the continuity of the phase axis is poor and the mudstone thickness is <5m, the geophysical evaluation value of the lithological trap cover condition b2 = 60.

[0096] In this embodiment, taking the potential lithological target Z28 as an example, the caprock phase axis exhibits characteristics of strong amplitude and good continuity, and the mudstone thickness is >10m. Therefore, the geophysical evaluation value of the lithological trap caprock condition is b2 = 100.

[0097] Step S80: Determine the evaluation value S2 of the lithological closure and capping strata condition based on the geological evaluation value b1 and the geophysical evaluation value b2 of the lithological closure and capping strata condition.

[0098] S2 = 0.5b1 + 0.5b2

[0099] In the formula: S2 is the evaluation value of the lithological trap cover condition; b1 is the geological evaluation value of the lithological trap cover condition; b2 is the geophysical evaluation value of the lithological trap cover condition.

[0100] In this embodiment, the lithological trap cap condition evaluation value S2 of Z28 is 100;

[0101] Step S90: Determine the comprehensive score value S of the trap based on the evaluation value S1 of the lithological trap lateral boundary and the evaluation value S2 of the lithological trap cap layer condition, and conduct a graded evaluation.

[0102] S = 0.7S1 + 0.3S2

[0103] In the formula: S2 is the evaluation value of the lithological trap cap layer condition; S1 is the evaluation value of the lithological trap lateral boundary; S is the comprehensive score of the trap.

[0104] In this embodiment, the comprehensive trap score of Z28 is S = 90.2; level: extremely low risk, drilling of this target is recommended as a priority.

[0105] When 90 ≤ comprehensive score S ≤ 100, the risk level is extremely low;

[0106] When 70 < the comprehensive score S of the trap is less than 90, the risk level is low.

[0107] When 50 ≤ comprehensive score S ≤ 70, the risk level is relatively high.

[0108] When 0 < the comprehensive score S of the trap is less than 50, the risk level is extremely high.

[0109] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A comprehensive classification and evaluation method for deltaic sand-rich lithological traps, characterized in that, Includes the following steps: Step S10: Obtain the geological background, core data, development data, logging data, and seismic data of the target work area; Step S20: Establish a high-frequency sequence stratigraphic framework; Step S30: Characterize the sedimentary microfacies; Step S40: Predict the thickness distribution of sandstone and mudstone bodies; Step S50: Determine the geological evaluation values ​​of the lateral boundaries of the lithological traps. a 1. Geophysical evaluation value of lateral boundary of lithological trap a 2. Quantitative characterization and evaluation values ​​of mudstone at the lateral boundary of lithological traps a 3; In step S50, when the distance from the subfacies boundary is >5 km and the sea level is rising, the geological evaluation value of the lateral boundary of the lithological trap is... a 1=100; Geological evaluation value of the lateral boundary of a lithological trap when the distance from the subfacies boundary is -5 to 5 km and the sea level rise and fall are relatively stable. a 1=80; Geological evaluation value of the lateral boundary of lithological traps when the distance from the subfacies boundary is less than -5 km and the sea level drops. a 1 = 60; When there is significant dislocation of the lateral phase axis, clear variations in the strength of conventional properties, and the boundary of the frequency-division RGB property is gray-black, the geophysical evaluation value of the lateral boundary of the lithological trap is... a 2=100; the lateral phase axis shows a weakening characteristic, the strong amplitude of conventional properties gradually transitions to weak amplitude, and when the color of the frequency-division RGB attribute changes from green to gray, the geophysical evaluation value of the lateral boundary of the lithological trap is... a 2=80; Lateral phase axis shows no significant change, conventional properties show slight changes, and when the boundary color of the frequency-division RGB attribute is yellowish-red, the geophysical evaluation value of the lateral boundary of the lithological trap is... a 2 = 60; When the lateral mudstone thickness is >15 m, the quantitative characterization evaluation value of mudstone at the lateral boundary of the lithological trap is... a 3 = 100; Quantitative characterization evaluation value of mudstone at the lateral boundary of lithological trap when the lateral mudstone thickness is 8-15 m. a 3=80; Quantitative characterization evaluation value of mudstone at the lateral boundary of lithological trap when the lateral mudstone thickness is <8 m. a 3 = 60; Step S60: Based on the geological evaluation values ​​of the lateral boundary of the lithological trap. a 1. Geophysical evaluation value of lateral boundary of lithological trap a 2. Quantitative characterization and evaluation values ​​of mudstone at the lateral boundary of lithological traps a 3. Determine the evaluation value of the lateral boundary of the lithological trap. S 1; Step S70: Determine the geological evaluation values ​​of the lithological trap cap strata. b 1. Geophysical evaluation value of lithological trap cap conditions b 2; Step S80: Geological evaluation value based on lithological trap cap conditions b 1. Geophysical evaluation value of lithological trap cap conditions b 2. Determine the evaluation value of lithological trap cap conditions S 2; Step S90: Based on the evaluation value of the lateral boundary of the lithological trap S 1. Evaluation value of lithological trap cap condition S 2. Determine the comprehensive score of the trap. S And conduct graded evaluation.

2. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 1, characterized in that, The specific steps of step S20 are as follows: Step S21: Select relevant sequence stratigraphy theories based on the geological background of the target work area and establish a high-frequency sequence stratigraphy scheme; Step S22: Create synthetic records for well-seismic calibration, clarify the reflection characteristics of high-frequency sequence interfaces in seismic profiles, and perform interpretation and tracing of the entire area to establish a high-frequency sequence stratigraphic framework for the entire area.

3. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 1, characterized in that, The specific process of step S30 is as follows: Step S31: Based on the marine delta sedimentary model, identify typical sedimentary structures on the core, establish a sedimentary microfacies division scheme for the target work area, clarify the lithological and electrical characteristics of each sedimentary microfacies, and establish a rock-electrical-seismic sedimentary transformation map. Step S32: Based on the established sedimentary transformation template, interpret the sedimentary microfacies of a single well according to the core photographs, the differences in electrical characteristics of different microfacies, and the vertical combination of lithology. Step S33: Based on the well-seismic calibration results, select appropriate seismic attributes for extraction, and extract the corresponding RGB fusion attributes for frequency division. Step S34: Under the guidance of the sedimentary model, the sedimentary microfacies are characterized based on the interpretation of single-well-to-well facies, single seismic attributes, and frequency-division RGB fusion attributes.

4. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 1, characterized in that, The specific process of step S40 is as follows: Step S41: Select 17 types of seismic attributes, including amplitude, statistics, waveform, and frequency, and extract them. Then, perform correlation analysis with the surface statistical sand body thickness. Step S42: Select the best seismic attributes and predict the plane distribution map of sand body thickness; Step S43: Obtain the mudstone thickness plane distribution map based on the top and bottom of the target sand body and the plane distribution map of the sand body thickness.

5. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 1, characterized in that, The calculation formula in step S60 is: In the formula: S 1 represents the evaluation value of the lateral boundary of the lithological trap; a 1 represents the geological evaluation value of the lateral boundary of the lithological trap; a 2 represents the geophysical evaluation value of the lateral boundary of the lithological trap; a 3 represents the quantitative characterization and evaluation value of mudstone at the lateral boundary of the lithological trap.

6. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 1, characterized in that, In step S70, when the floodplain is classified as a third- or fourth-order floodplain and the caprock sedimentary subfacies belongs to the prodelta-shallow marine facies, the geological evaluation value of the lithological trap caprock condition is as follows: b 1=100; When the floodplain is a fifth-order floodplain and the caprock sedimentary subfacies belongs to the outer delta front, the geological evaluation value of the lithological trap caprock condition is... b 1=80; When the floodplain is of a higher order, the caprock sedimentary subfacies belongs to the inner delta front, and the geological evaluation value of the lithological trap caprock conditions is... b 1 = 60; When the continuity of the phase axis is good and the mudstone thickness is >10 m, the geophysical evaluation value of the lithological trap cap layer condition is as follows: b 2 = 100; When the continuity of the phase axis is moderate and the mudstone thickness is 5-10 m, the geophysical evaluation value of the lithological trap cover condition is as follows: b 2=80; When the continuity of the phase axis is poor and the mudstone thickness is <5 m, the geophysical evaluation value of the lithological trap cover condition. b 2 = 60.

7. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 6, characterized in that, The calculation formula in step S80 is: In the formula: S 2 represents the evaluation value for lithological trap caprock conditions; b 1 represents the geological evaluation value of the lithological trap cap layer conditions; b 2 represents the geophysical evaluation value of the lithological trap cover condition.

8. The comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 7, characterized in that, The calculation formula in step S90 is: In the formula: S 2 represents the evaluation value for lithological trap caprock conditions; S 1 represents the evaluation value of the lateral boundary of the lithological trap; S This is the overall score for the closed loop.

9. A comprehensive classification and evaluation method for deltaic sand-rich lithological traps according to claim 8, characterized in that, In step S90, when 90 ≤ the comprehensive score of the trap... S When the value is ≤100, the risk level is extremely low; When 70 < the comprehensive score of the closed loop S When the value is less than 90, the risk level is considered low. When 50 ≤ the comprehensive score of the closed loop S When the value is ≤70, the risk level is considered high. When 0 < the comprehensive score of the closed loop S When the value is less than 50, the risk level is extremely high.

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