Quantitative description method of beach bar sand body based on paleotopography

Abstract

The present application provides a kind of based on paleotopography beach bar sand body quantitative description method, the based on paleotopography beach bar sand body quantitative description method includes: step 1, the paleotopography of a certain sedimentary period is restored by integrating seismic, geological and well logging data;Step 2, select multiple representative well point samples;Step 3, obtain the restored stratigraphic depth value and the thickness data of drilled sand body of the position where single sample well point is located;Step 4, establish sand body thickness prediction formula based on restored stratigraphic depth;Step 5, according to the sand body thickness prediction formula based on restored stratigraphic depth established, the thickness of beach bar sand body in unoperated area is quantitatively predicted.The based on paleotopography beach bar sand body quantitative description method has high prediction accuracy, effectively overcomes the limitation that conventional beach bar sand prediction method cannot quantitatively describe, is simple and easy to operate, and can realize the characterization of beach bar sand body thickness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of unconventional oil development, and particularly relates to a quantitative description method of beach-bar sand bodies based on paleotopography. BACKGROUND

[0002] Beach-bar sand is one of the most important oil and gas reservoirs in faulted basins, and the quantitative description of beach-bar sand bodies has always been the focus of geologists at home and abroad. With the continuous advancement of exploration, deep beach-bar sand reservoirs have gradually become an important field of oil and gas exploration in eastern continental faulted basins in China. For example, in the western oil region of Shengli Oilfield, nearly 200 million tons of beach-bar sandstone proven reserves have been reported, and the development potential is huge. At present, most domestic and foreign researchers believe that the deposition of beach-bar sand in faulted lake basins is mainly controlled by the "three ancient" factors, including paleotopography, paleohydrodynamic force and paleobase level. Among them, paleotopography can provide evidence for the spatial relationship between the sedimentary area and the sedimentary center, and reflect the transport channel of sediments, which is of great significance for predicting sedimentary systems. Through the retrieval of domestic and foreign literatures, domestic scholars mostly make qualitative prediction in the description of beach-bar sand reservoirs, and lack of applicable technical research in the quantitative prediction of sand body thickness, and there is no effective method to quantitatively describe the sand body boundary and thickness.

[0003] In the Chinese patent application with the application number CN201910348690.2, a method and device for predicting thin reservoirs in lacustrine beach-bar sand bodies are involved. The method includes: dividing the sequence levels of different single wells according to historical data and logging data in the target area; comparing the sand bodies of different single wells with the same sequence level to obtain a sand body comparison result; preprocessing and standardizing the logging curve of the single well, and selecting an inversion sample curve from the logging curve according to the lithology data of the logging curve; performing band-pass filtering on the seismic data according to the sand body comparison result to obtain thin reservoir seismic reflection data; performing waveform phase-controlled stochastic inversion on the inversion sample curve, the acoustic curve and the density curve in the seismic data, and the thin reservoir seismic reflection data to obtain a thin reservoir inversion result; and determining the position of the thin reservoir according to the thin reservoir inversion result. The application can improve the prediction accuracy of thin reservoirs in lacustrine beach-bar sand bodies.

[0004] In the Chinese patent application No. CN201710711093.2, a reservoir sand prediction method and device based on wind field, source, and basin system are involved. The method includes: obtaining geological data of a region to be predicted; the geological data at least includes multiple types of core data, paleontology data, well logging data, and seismic data; inputting the geological data into a preset wind field, source, and basin system model to generate beach bar sand formation process data of the region to be predicted; the wind field, source, and basin system model at least includes multiple types of paleo-source recovery tool, paleo-wind recovery tool, paleo-wind direction recovery tool, paleo-landform recovery tool, and paleo-water depth recovery tool; and predicting the specific distribution position of the beach bar sand in the region to be predicted by using geological method and geophysical method according to the beach bar sand formation process data. The invention can effectively identify and predict the distribution position and range of the beach bar sand in shallow water, and improve the feasibility and accuracy of the reservoir sand prediction method.

[0005] In the Chinese patent application No. CN202010691793.1, a beach bar sand reservoir prediction method and device are involved. The method includes: dividing a reservoir corresponding to well logging data of a target well located in a beach bar sand research area into multiple sand body development periods of beach bar sand according to the well logging data; selecting a development period with the largest oil and gas content as a target interval based on oil and gas exploration results corresponding to each development period, and determining seismic horizon data of the target interval; determining a beach bar sand development area in the beach bar sand research area according to the seismic horizon data of the target interval, and determining a beach bar sand reservoir distribution result of the beach bar sand research area based on the beach bar sand development area. The application can effectively improve the identification accuracy of the beach bar sand reservoir, and effectively improve the efficiency, reliability, and accuracy of predicting the beach bar sand reservoir, thereby providing effective and accurate data basis for beach bar sand exploration and oil and gas exploitation.

[0006] In the Chinese patent application No. CN201210212603.9, a method for establishing a beach bar sandstone microfacies identification mode is involved. The method applies a method for identifying sedimentary microfacies by combining well logging curves with geological logging data. First, the lithology is accurately identified according to the well logging curves, then the small layers are divided in the geological microfacies layer by combining the well logging curves and the lithology, the curve values and shape values of the small layers are extracted, and finally the beach bar sandstone sedimentary microfacies is accurately divided according to the curve values, shape values, and lithology, and a beach bar sandstone sedimentary microfacies mode identification standard library and a beach bar sandstone microfacies identification mode are established. Based on the beach bar sandstone sedimentary microfacies mode identification standard library, the beach bar sandstone sedimentary microfacies can be accurately identified by combining the well logging curve values and shape values using the beach bar sandstone microfacies identification mode. The method can be applied to the division of all beach bar sandstone sedimentary microfacies, and can provide a basis for judging the reservoir properties and oil and gas content.

[0007] The above prior art is quite different from the present application, and cannot solve the technical problems we want to solve, and therefore we have invented a new quantitative description method of beach bar sand body based on paleotopography. SUMMARY

[0008] The purpose of the present application is to provide a quantitative description method of beach bar sand body based on paleotopography, which can improve prediction accuracy and is simple and easy to operate.

[0009] The purpose of the present application can be achieved by the following technical measures: a quantitative description method of beach bar sand body based on paleotopography, comprising:

[0010] Step 1, restoring paleotopography of a certain sedimentary period based on seismic, geological and logging data;

[0011] Step 2, selecting a plurality of representative well point samples;

[0012] Step 3, obtaining the restored stratigraphic depth value and the drilled sand body thickness data of the position of the single sample well point;

[0013] Step 4, establishing a sand body thickness prediction formula based on the restored stratigraphic depth;

[0014] Step 5, quantitatively predicting the thickness of the beach bar sand body in the non-moving area according to the established sand body thickness prediction formula based on the restored stratigraphic depth.

[0015] The purpose of the present application can also be achieved by the following technical measures:

[0016] In step 1, the top and bottom interfaces of the stratum are determined to accurately represent a certain geological period, and the paleotopography of the geological period is restored by comprehensive use of residual thickness calculation, stratum filling and completion, and sediment compaction correction methods.

[0017] In step 2, based on paleotopographic data analysis, a plurality of representative well point samples are selected in underwater highlands, underwater uplift gentle slope zones and underwater low-lying areas.

[0018] In step 2, the paleotopography of a certain geological period is restored, and is classified according to different paleotopographic features, which can be divided into underwater highlands, underwater uplift gentle slope zones and underwater low-lying areas, and then a plurality of representative wells are selected at different paleotopographic positions to ensure the diversity of sample quantity and improve the reliability of analysis results.

[0019] In step 3, based on the paleotopography restoration results of a certain geological period, the restored stratigraphic depth value of the position of the single sample well point is counted; based on the fine stratigraphic correlation results, the sand body thickness value drilled by the single sample well point in the geological period is counted.

[0020] In step 4, on the basis of classification of different paleotopographic positions, the correlation coefficient of the thickness of the sand body drilled by a single sample well point and the reduced stratigraphic depth is calculated, a sand body thickness prediction formula based on the reduced stratigraphic depth is obtained, and a fitting trend graph of the sand body thickness changing with the reduced stratigraphic depth is drawn.

[0021] In step 4, through petrophysical simulation experiments, the stratigraphic depth value of a single well point at different paleotopographic positions and the thickness of the sand body drilled in the previous step are fitted to obtain the sand body thickness-reduced stratigraphic depth fitting trend equation of the underwater high, the underwater uplift gentle slope zone and the underwater low, and draw a fitting trend graph of the sand body thickness changing with the reduced stratigraphic depth.

[0022] The sand body thickness-reduced stratigraphic depth fitting trend equation of the underwater high and the underwater uplift gentle slope zone is:

[0023] Y1=a1e -b1x1

[0024] In the formula, Y1 is the actual drilled sand body thickness of the well point, the unit is m; x1 is the reduced stratigraphic depth of the position where the well point is located, the unit is m. a1 is the fitting coefficient between the actual drilled sand body thickness and the reduced stratigraphic depth of the well point, a constant; b1 is a constant.

[0025] In step 4, it can be seen from the sand body thickness-reduced stratigraphic depth fitting trend equation of the underwater high and the underwater uplift gentle slope zone that the sand thickness and the reduced stratigraphic depth in the underwater high and the gentle slope zone are exponentially negatively correlated, and the higher the paleotopography, the smaller the thickness of the deposited sand body.

[0026] In step 4, the sand body thickness-reduced stratigraphic depth fitting trend equation of the underwater low is:

[0027] Y2=a2e b2x2

[0028] In the formula, Y2 is the actual drilled sand body thickness of the well point in the underwater low, the unit is m; x2 is the reduced stratigraphic depth of the well point in the underwater low, the unit is m. a2 is the fitting coefficient between the actual drilled sand body thickness and the reduced stratigraphic depth, a constant; b2 is a constant.

[0029] In step 4, it can be seen from the sand body thickness-reduced stratigraphic depth fitting trend equation of the underwater low that the sand thickness and the reduced stratigraphic depth in the underwater low are exponentially positively correlated, and the higher the paleotopography, the greater the thickness of the deposited sand body.

[0030] The quantitative description method for beach-bar sand bodies based on paleotopography in this invention utilizes seismic, geological, and well logging data, corrected for sedimentary compaction. This comprehensive approach reconstructs the paleotopography of the Sha-4 depositional period. Based on the classification of different paleotopic locations, it extracts the reconstructed stratigraphic depth and encountered sand body thickness data for each individual sample well location. Using the reconstructed stratigraphic depth as the independent variable and the encountered sand body thickness as the dependent variable, regression fitting establishes a sand body thickness prediction formula based on the reconstructed stratigraphic depth, thereby quantitatively predicting the thickness of beach-bar sand bodies in undisturbed areas. Compared with existing technologies, this invention has the following advantages: Addressing the challenge of describing beach-bar sand bodies, and guided by previous "three ancient" sand-controlling sedimentary models, this invention deepens methodological research. Based on paleotopographic reconstruction results, it utilizes the nonlinear exponential relationship between the reconstructed strata thickness at the location of well points in a dense well network area and the thickness of the sand bodies encountered by the well points to guide the quantitative description of sand bodies in the undisturbed beach-bar area. This effectively improves the accuracy and reliability of beach-bar sand body description. Furthermore, none of the existing methods for fine description of beach-bar sand bodies involve using paleotopographic reconstruction results to guide the quantitative prediction of beach-bar sand body thickness, demonstrating strong innovation. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a specific embodiment of the quantitative description method for beach-bar sand bodies based on paleotopography of the present invention;

[0032] Figure 2 for Figure 1 A plan view of paleotopographic reconstruction from a certain geological period is shown in the example.

[0033] Figure 3 for Figure 1 A fitting diagram of the thickness of sand bodies encountered at a well point and the reduced strata in a certain geological period, as shown in the example;

[0034] Figure 4 for Figure 1 A plane prediction diagram of the thickness of the beach-bar sand body during a certain geological period is shown in the example. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0037] This invention presents a quantitative description method for beach-bar sand bodies based on paleotopography. Utilizing seismic, geological, and well logging data, it reconstructs the paleotopography of a specific depositional period through a comprehensive approach involving residual thickness calculation, stratigraphic leveling and completion, and sedimentary compaction correction. Based on paleotopographic data analysis, multiple representative wellpoint samples are selected from underwater highlands, underwater uplifted gentle slopes, and underwater depressions to obtain the reconstructed stratigraphic depth and encountered sand body thickness at each wellpoint location. By classifying different paleotopographic locations, and based on the correlation coefficient between the encountered sand body thickness and the reconstructed stratigraphic depth obtained from experimental calculations, a fitting trend equation for sand body thickness versus reconstructed stratigraphic depth is established. This fitting trend equation is then used to quantitatively predict the thickness of beach-bar sand bodies in undisturbed areas. This invention offers high prediction accuracy, effectively overcoming the limitations of conventional beach-bar sand prediction methods in quantitative description. It is simple to operate and can characterize the thickness of beach-bar sand bodies.

[0038] The following are several specific embodiments of the application of the present invention.

[0039] Example 1

[0040] In a specific embodiment 1 of the present invention, such as Figure 1 As shown, Figure 1 This is a flowchart of the quantitative description method for beach-bar sand bodies based on paleotopography according to the present invention. The method includes the following steps:

[0041] Step 101: Reconstruct paleotopography of a specific sedimentary period by integrating seismic, geological, and well logging data;

[0042] Step 102: Based on the analysis of paleotopographic data, select multiple representative well point samples in underwater highlands, underwater uplifted gentle slopes, and underwater depressions.

[0043] Step 103: Obtain the reduced formation depth and sand body thickness data at the location of a single sample well point;

[0044] Step 104: Based on the classification of different paleotopic locations, the restored stratum depth is used as the independent variable and the sand body thickness encountered by the well point is used as the dependent variable. Regression fitting is used to establish a sand body thickness prediction formula based on the restored stratum depth, and a fitting trend diagram of the sand body thickness changing with the restored stratum depth is drawn.

[0045] Step 105: Quantitatively predict the thickness of the beach-bar sand body in the undisturbed area based on the established sand body thickness prediction formula based on the depth of the reduced strata.

[0046] The ancient topography of a sedimentary period is restored by comprehensively analyzing seismic, geological and logging data, specifically including: determining the top and bottom interfaces of a stratum in a geological period, and restoring the ancient topography of the geological period by using the residual thickness, filling and patching, and sedimentary compaction correction methods.

[0047] Based on the analysis of the ancient topography data, multiple representative well point samples are selected in underwater highlands, underwater uplift gentle slope zones and underwater low-lying areas, specifically including: restoring the ancient topography of a geological period by using professional software, classifying according to different ancient topography characteristics, and dividing into underwater highlands, underwater uplift gentle slope zones and underwater low-lying areas, and then selecting multiple representative wells in different ancient topography positions to ensure the diversity of sample quantity and improve the reliability of the analysis result.

[0048] The restored stratum depth value and the drilled sand body thickness data of the position of the single sample well point are obtained, specifically including: based on the restoration results of the ancient topography of a geological period, the restored stratum depth value of the position of the single sample well point is counted by using professional software; based on the fine stratum correlation results, the sand body thickness value drilled by the single sample well point in the geological period is counted.

[0049] Based on the classification of different ancient topography positions, the correlation coefficient of the drilled sand body thickness and the restored stratum depth of the single sample well point is calculated, the sand body thickness prediction formula based on the restored stratum depth is obtained, and the fitting trend graph of the sand body thickness changing with the restored stratum depth is drawn, specifically including: through the rock physical simulation experiment, the stratum depth value and the drilled sand body thickness of the single well point at different ancient topography positions counted in the last step are fitted, the sand body thickness- restored stratum depth fitting trend equation of the underwater highland, the underwater uplift gentle slope zone and the underwater low-lying area is obtained respectively, and the fitting trend graph of the sand body thickness changing with the restored stratum depth is drawn. The sand body thickness- restored stratum depth fitting trend equation of the underwater highland / underwater uplift gentle slope zone is:

[0050] Y1=a1e -b1x1

[0051] In the formula, Y1 is the actual drilled sand body thickness of the well point, and the unit is m; x1 is the restored stratum depth of the position of the well point, and the unit is m.

[0052] It can be seen from the sand body thickness- restored stratum depth fitting trend equation of the underwater highland / underwater uplift gentle slope zone that the sand thickness and the restored stratum depth in the underwater highland and the gentle slope zone are exponentially negatively correlated, the higher the ancient topography, the smaller the sedimentary sand body thickness.

[0053] The sand body thickness- restored stratum depth fitting trend equation of the underwater low-lying area is:

[0054] Y2=a2e b2x2

[0055] In the formula, Y3 is the actual drilled sand thickness at the underwater low-lying place, in meters; and x3 is the reduced stratigraphic depth at the underwater low-lying place, in meters.

[0056] It can be seen from the fitting trend equation of the sand thickness-reduced stratigraphic depth at the underwater low-lying place that the sand thickness at the underwater low-lying place is exponentially positively correlated with the reduced stratigraphic depth. The higher the paleotopography, the greater the thickness of the deposited sand body.

[0057] Embodiment 2

[0058] The paleotopography-based beach bar sand body quantitative description method of this embodiment comprises the following steps:

[0059] 1. The paleotopography during the deposition of the fourth member of the Shahejie Formation in a certain block is restored by comprehensive utilization of residual thickness calculation, stratigraphic filling and correction methods based on comprehensive seismic, geological and logging data. As shown in FIG. 1, the favorable paleotopography such as the underwater uplift gentle slope zone, the underwater high land and the structural turning zone can be accurately depicted, and the provenance is distributed from the southwest to the northeast. Figure 2

[0060] 2. The reduced stratigraphic depth is taken as the independent variable, and the drilled sand thickness of the well point is taken as the dependent variable to regress and fit to establish a sand thickness prediction formula based on the reduced stratigraphic depth.

[0061] Based on the paleotopographic data analysis, a plurality of representative well point samples are selected in the underwater high land, the underwater uplift gentle slope zone and the underwater low-lying place to obtain the reduced stratigraphic depth value and the drilled sand thickness data of the well point at the position of the single sample;

[0062] Based on the classification of different paleotopographic positions, the reduced stratigraphic depth is taken as the independent variable, and the drilled sand thickness of the well point is taken as the dependent variable to regress and fit to establish a sand thickness prediction formula based on the reduced stratigraphic depth, and a fitting trend graph of the sand thickness changing with the reduced stratigraphic depth is drawn, as shown in FIG. 2. The fitting trend equation of the sand thickness-reduced stratigraphic depth in the underwater uplift gentle slope zone is: Figure 3

[0063] Y1 = 2.638e -0.005x1

[0064] R 2 = 0.9568

[0065] In the formula, Y1 is the actual drilled sand thickness of the well point at the underwater uplift gentle slope zone, in meters; x1 is the reduced stratigraphic depth of the well point at the underwater uplift gentle slope zone, in meters; and R 2 is the correlation between the actual drilled sand thickness and the reduced stratigraphic depth of the well point at the underwater uplift gentle slope zone, a constant.

[0066] ​​The fitting trend equation of sand body thickness-reduced stratum depth at the underwater high place is:

[0067] Y2 = 1.996e -0.005x2

[0068] R 2 = 0.9266

[0069] In the formula, Y2 is the actual drilled sand body thickness of the well point at the underwater high place, and the unit is m; x2 is the reduced stratum depth of the well point at the underwater high place, and the unit is m; R 2 is the correlation between the actual drilled sand body thickness and the reduced stratum depth of the well point at the underwater high place, and is a constant.

[0070] The fitting trend equation of sand body thickness-reduced stratum depth at the underwater low place is:

[0071] Y3 = 1529.5e 0.009x3

[0072] R 2 = 0.9699

[0073] In the formula, Y3 is the actual drilled sand body thickness of the well point at the underwater low place, and the unit is m; x3 is the reduced stratum depth of the well point at the underwater low place, and the unit is m; R 2 is the correlation between the actual drilled sand body thickness and the reduced stratum depth of the well point at the underwater low place, and is a constant.

[0074] 3. Drawing a sand body thickness plane distribution prediction map

[0075] According to the sand body thickness prediction formula, a sand body thickness plane distribution prediction map is drawn, as shown in Figure 4 From the fitting trend graph of the sand body thickness changing with the reduced stratum depth, it can be seen that the sand body thicknesses at different positions of the ancient landform are obviously different, and the sand thicknesses from large to small are: the underwater uplift gentle slope zone > the underwater high place > the underwater low place. In the research example, the sand thickness of the underwater low place is exponentially positively correlated with the reduced stratum depth, the higher the ancient landform, the greater the sedimentary sand body thickness; the sand thickness of the underwater high place and the gentle slope zone is exponentially negatively correlated with the reduced stratum depth, the higher the ancient landform, the smaller the sedimentary sand body thickness.

[0076] Embodiment 3

[0077] In the specific embodiment 3 of the application, the following steps are included:

[0078] 1. The ancient landform of a block in a Sha 4 sedimentary period is restored by the comprehensive use of residual thickness calculation, stratum filling and complementing, and sediment compaction correction methods through the comprehensive use of seismic, geological and logging data, and the ancient landform includes the underwater uplift gentle slope zone, the underwater high place and other favorable ancient landforms.

[0079] 2. Establishing the reduced stratigraphic depth as the independent variable, the well point drilled sand thickness as the dependent variable, regression fitting to establish the sand thickness prediction formula based on the reduced stratigraphic depth.

[0080] Based on the analysis of paleotopographic data, a plurality of representative well point samples are selected in underwater highlands, underwater uplift gentle slope zone and underwater low-lying areas, and the reduced stratigraphic depth value and the drilled sand thickness data of the position of the single sample well point are obtained;

[0081] On the basis of classification of different paleotopographic positions, the reduced stratigraphic depth is taken as the independent variable, and the well point drilled sand thickness is taken as the dependent variable, and the sand thickness prediction formula based on the reduced stratigraphic depth is established by regression fitting, and the fitting trend graph of the sand thickness changing with the reduced stratigraphic depth is drawn, wherein the sand thickness-reduced stratigraphic depth fitting trend equation of the underwater uplift gentle slope zone is:

[0082] Y1=3.726e -0.005x1

[0083] R 2 =0.9007

[0084] In the formula, Y1 is the actual drilled sand thickness of the well point in the underwater uplift gentle slope zone, the unit is m; x1 is the reduced stratigraphic depth of the well point in the underwater uplift gentle slope zone, the unit is m; R 2 is the correlation between the actual drilled sand thickness and the reduced stratigraphic depth of the well point in the underwater uplift gentle slope zone, and the constant.

[0085] The sand thickness-reduced stratigraphic depth fitting trend equation of the underwater highlands is:

[0086] Y2=2.132e -0.005x2

[0087] R 2 =0.9308

[0088] In the formula, Y2 is the actual drilled sand thickness of the well point in the underwater highlands, the unit is m; x2 is the reduced stratigraphic depth of the well point in the underwater highlands, the unit is m; R 2 is the correlation between the actual drilled sand thickness and the reduced stratigraphic depth of the well point in the underwater highlands, and the constant.

[0089] The sand thickness-reduced stratigraphic depth fitting trend equation of the underwater low-lying area is:

[0090] Y3=1426.3e 0.009x3

[0091] R 2 =0.9661

[0092] In the formula, Y3 is the actual drilled thickness of the sand body at the low-lying underwater point, in meters; x3 is the reduced stratigraphic depth of the well point at the low-lying underwater point, in meters; R 2 is the correlation between the actual drilled thickness of the sand body and the reduced stratigraphic depth of the well point at the low-lying underwater point, and C is a constant.

[0093] 3. Drawing a sand body thickness plane distribution prediction map

[0094] According to the sand body thickness prediction formula, a sand body thickness plane distribution prediction map is drawn. As can be seen from the fitting trend graph of the sand body thickness with the reduced stratigraphic depth, the sand body thickness at different positions of the ancient landform is obviously different, and the thickness of the deposited sandstone is in descending order as follows: the underwater uplift gentle slope zone > the underwater highland > the underwater low-lying zone. In the research example, the sand thickness of the underwater low-lying zone is exponentially positively correlated with the reduced stratigraphic depth, the higher the ancient landform, the greater the thickness of the deposited sand body; the sand thickness of the underwater highland and the gentle slope zone is exponentially negatively correlated with the reduced stratigraphic depth, the higher the ancient landform, the smaller the thickness of the deposited sand body.

[0095] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0096] In addition to the technical features described in the specification, they are known to those skilled in the art.

Claims

1. A method for quantitative description of beach-bar sand bodies based on palaeotopography, characterized in that, The ancient topography-based beach bar sand body quantitative description method comprises: Step 1, restoring the ancient topography of a certain sedimentary period based on the comprehensive analysis of seismic, geological and logging data; Step 2, selecting a plurality of representative well point samples; Step 3, obtaining the restored stratigraphic depth value and the drilled sand body thickness data of the position of the single sample well point; Step 4, establishing a sand body thickness prediction formula based on the restored stratigraphic depth; Step 5, quantitatively predicting the thickness of the beach bar sand body in the non-moving area according to the established sand body thickness prediction formula based on the restored stratigraphic depth; In step 4, on the basis of classification of different ancient topographic positions, the correlation coefficient of the drilled sand body thickness and the restored stratigraphic depth of the single sample well point is calculated to obtain the sand body thickness prediction formula based on the restored stratigraphic depth, and a fitting trend graph of the sand body thickness changing with the restored stratigraphic depth is drawn; In step 4, through the rock physical simulation experiment, the stratigraphic depth value and the drilled sand body thickness of the single well point at different ancient topographic positions in the last step are fitted to obtain the sand body thickness-restore stratigraphic depth fitting trend equation of the underwater highland, the underwater uplift gentle slope zone and the underwater low-lying place respectively, and a fitting trend graph of the sand body thickness changing with the restored stratigraphic depth is drawn.

2. The paleotopographic-based beach berm sand body quantitative description method of claim 1, wherein, In step 1, the accurate stratigraphic top and bottom interfaces of a certain geological period are determined, and the ancient topography of the geological period is restored by the comprehensive use of residual thickness calculation, stratigraphic filling and completion, and sedimentary compaction correction methods.

3. The paleotopographic-based beach berm sand body quantitative description method of claim 1, wherein, In step 2, based on the ancient topographic data analysis, a plurality of representative well point samples are selected in the underwater highland, the underwater uplift gentle slope zone and the underwater low-lying place.

4. The paleotopographic-based beach berm sand body quantitative description method of claim 3, wherein, In step 2, the ancient topography of a certain geological period is restored, and according to different ancient topographic features, it is classified into underwater highland, underwater uplift gentle slope zone and underwater low-lying place, and then a plurality of representative wells are selected at different ancient topographic positions to ensure the diversity of sample quantity and improve the reliability of the analysis result.

5. The paleotopographic-based beach berm sand body quantitative description method of claim 1, wherein, In step 3, based on the ancient topography restoration results of a certain geological period, the restored stratigraphic depth value of the position of the single sample well point is calculated; Based on the fine stratigraphic correlation results, the drilled sand body thickness value of the single sample well point in the geological period is calculated.

6. The paleotopographic-based beach berm sand body quantitative description method of claim 5, wherein, In step 4, the sand body thickness-restore stratigraphic depth fitting trend equation of the underwater highland and the underwater uplift gentle slope zone is: ； In the formula, Y1 is the actual drilled sand body thickness of the well point, the unit is m; x1 is the restored stratigraphic depth of the position of the well point, the unit is m; a1 is the fitting coefficient between the actual drilled sand body thickness and the restored stratigraphic depth of the well point, which is a constant; b1 is a constant.

7. The paleotopographic-based beach berm sand body quantitative description method of claim 6, wherein, In step 4, it can be seen from the sand body thickness-restore stratigraphic depth fitting trend equation of the underwater highland and the underwater uplift gentle slope zone that the sand thickness and the restored stratigraphic depth in the underwater highland and the gentle slope zone are exponentially negatively correlated, the higher the ancient topography, the less the sedimentary sand body thickness.

8. The paleotopographic-based beach berm sand body quantitative description method of claim 5, wherein, In step 4, the sand body thickness-restore stratigraphic depth fitting trend equation of the underwater low-lying place is: ： In the formula, Y2 is the actual drilled sand body thickness of the well point in the underwater low-lying place, the unit is m; x2 is the restored stratigraphic depth of the well point in the underwater low-lying place, the unit is m; a2 is the fitting coefficient between the actual drilled sand body thickness and the restored stratigraphic depth of the well point, which is a constant; b2 is a constant.

9. The paleotopographic-based beach berm sand body quantitative description method of claim 8, wherein, In step 4, from the underwater low-lying sand body thickness-reducing stratigraphic depth fitting trend equation can be seen that the underwater low-lying sand thickness is positively correlated with the reducing stratigraphic depth, the higher the paleotopography, the greater the thickness of the deposited sand body.

Images