A method and system for determining true thickness of a formation
By integrating core angle statistical models and geophysical data, and combining apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle, the error problem in calculating the true thickness of strata was solved, and accurate stratum thickness measurement was achieved in complex environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHWEST PETROLEUM UNIV
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies rely on field outcrop measurements to obtain the true thickness of strata, which are subject to large human errors. Furthermore, ground-penetrating radar methods are affected by the heterogeneity of underground media, leading to multiple interpretations and systematic biases, making it difficult to accurately calculate strata thickness.
By integrating core measurement data and geophysical data, a core angle statistical model was established. Combined with apparent thickness, total dip angle, unconformity dip angle and uplift dip angle, a true thickness calculation model was constructed. The core data obtained by drilling is not limited by surface cover and topography, and the true thickness was calculated by combining the principles of solid geometry.
It breaks through the dependence on the conditions of the outcrop in the field, eliminates the error of manual measurement, and establishes a true thickness calculation model with multi-parameter constraints. The calculation results are more geologically significant, highly accurate and highly applicable, and suitable for covered areas, densely vegetated areas and areas with complex terrain.
Smart Images
Figure CN122172300A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of geological surveying technology, and in particular to a method and system for determining the true thickness of strata. Background Technology
[0002] The true thickness of strata is a very important data point. It can be used to calculate mineral resource reserves, evaluate the potential of source rocks, calculate the effective thickness of reservoirs, and accurately reflect the paleogeography and subsidence of sedimentary basins.
[0003] Currently, the true thickness of strata is primarily obtained by accurately measuring the dip, dip angle, and strike of the strata using a geological compass in the field. The exposed width of the strata, i.e., the apparent thickness, is measured along a measurement profile line. The true thickness is then calculated using formulas. More complex cases also have corresponding formulas, but the calculations are more complex. The industry is constantly exploring new solutions, such as patents for rapidly solving the true thickness of rock strata based on three-dimensional geometric models. However, these methods rely on compass measurements, which require repeated adjustments by surveyors at multiple locations, resulting in poor accuracy due to human operation. Furthermore, they require outcrops with clear, continuous, and easily measurable stratigraphic interfaces; if the outcrops do not meet these conditions, the measurement results will have significant errors.
[0004] To determine the true thickness of strata, ground-penetrating radar (GPR) is used to emit high-frequency electromagnetic waves into the ground. When these waves encounter interfaces between strata with different electrical properties, some energy is reflected back. By receiving and analyzing the travel time and waveform characteristics of these reflected waves, the interfaces between different strata can be identified. However, underground media are often heterogeneous, resulting in spatial variations in radar velocity. This leads to systematic deviations in depth and thickness calculations. Furthermore, different geological bodies may produce similar reflection signals, requiring extensive experience for interpretation, and different personnel may arrive at different conclusions. Summary of the Invention
[0005] To address the above problems, the present invention aims to provide a method and system for determining the true thickness of a formation.
[0006] The technical solution of the present invention is as follows: On the one hand, a method for determining the true thickness of a formation is provided, including the following steps: S1: Obtain the apparent thickness of the target formation based on the well logging and well logging data of the target formation; S2: Obtain the total dip angle and unconformity dip angle of the target stratum based on the rock core of the target stratum; S3: Obtain the uplift dip angle of the target stratum based on the seismic data of the target stratum; S4: Establish a true thickness calculation model for the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle; S5: Calculate the true thickness of the target stratum based on the true thickness calculation model of the stratum.
[0007] Preferably, step S1 specifically includes the following sub-steps: S11: Select a horizontal well in the target formation and obtain logging data and well logging data of the horizontal well; S12: Based on the well logging data and the well logging data, obtain the depth and location of the horizontal well; S13: Select a marker layer from the core sample of the horizontal well and obtain the corresponding depth of the marker layer; S14: Collect all marker layers and their corresponding depths, and divide the original formation corresponding to the horizontal well according to the marker layers; S15: Select two adjacent marker layers and calculate the apparent thickness of the target formation based on the well depth of the two adjacent marker layers.
[0008] Preferably, in step S13, the selection criteria for the marker layer are: significant lithological characteristics that can be identified by the naked eye on the rock core; and stable distribution that can be used to continuously trace stratigraphic units on the rock core.
[0009] Preferably, step S2 specifically includes the following sub-steps: S21: Establish an angle statistical model for the rock core; S22: Based on the aforementioned angle statistical model, obtain the interfaces at different depths within the same lithology; S23: Based on the interface, the average dip angle is obtained by averaging the angles of the same stratum. The average dip angle is the total dip angle. S24: Based on the angle statistical model, obtain the interface angles between different depths and different lithologies; S25: Calculate the average value of the interface angle to obtain the tilt angle of the unconformity surface.
[0010] Preferably, in step S21, the angle statistical model is obtained by establishing the following sub-steps: based on the core of the target stratum, identify the interface of lithological change in the core and the bedding in the same lithology, measure and statistically analyze the angles under different conditions, thereby obtaining the angle statistical model.
[0011] Preferably, step S3 specifically includes the following sub-steps: S31: Obtain seismic data of the target strata, and determine the overall dip interface of the strata in the later stage of deposition based on the differences in reflection morphology and fault characteristics interpreted from the seismic data. S32: Calculate the angle between the overall tilt interface of the strata in the later stage of deposition and the horizontal reference surface to obtain the uplift dip angle.
[0012] Preferably, in step S4, the model for calculating the true thickness of the formation is as follows: (1) In the formula: L is the true thickness of the formation; θ is the total dip angle; α is the dip angle of the unconformity surface; γ is the uplift dip angle; H is the apparent thickness.
[0013] On the other hand, a system for determining the true thickness of a formation is also provided, comprising: The apparent thickness acquisition module is used to acquire the apparent thickness of the target formation based on well logging and well logging data. The total dip angle acquisition module is used to obtain the total dip angle of the target formation based on the core sample of the target formation. The unconformity dip angle acquisition module is used to obtain the unconformity dip angle of the target formation based on the core sample of the target formation. The uplift dip angle module is used to obtain the uplift dip angle of the target strata based on the seismic data of the target strata. The true thickness calculation model module is used to establish a true thickness calculation model of the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle, and to calculate the true thickness of the target formation based on the true thickness calculation model of the formation.
[0014] The beneficial effects of this invention are: This invention integrates core measurement data with geophysical data to construct a method for calculating the true thickness of formations based on a statistical model of core angles. This method overcomes the technical bottlenecks of traditional measurement methods in multiple dimensions, specifically in the following ways: 1) It breaks through the dependence of traditional measurement on field outcrop conditions. Traditional geological compass measurement methods require clear, continuous, and easily accessible natural outcrops with stratigraphic interfaces, while this invention is based entirely on core data obtained through drilling, and is not limited by natural conditions such as surface cover, vegetation development, or steep terrain. It can accurately obtain stratigraphic thickness in covered areas, densely vegetated areas, and areas with complex terrain, significantly expanding the application scope of this method.
[0015] 2) It eliminates subjective errors caused by manual measurement. This invention establishes a statistical model of core angles to systematically measure and statistically analyze the angles of multiple lithological interfaces and bedding planes in the core. The statistical average value is used as a characterization parameter of the sedimentary dip angle of the strata, avoiding the subjective errors caused by human variation and inconsistent readings in traditional compass measurements, and ensuring the objectivity and repeatability of the measurement results.
[0016] 3) A multi-parameter constrained true thickness calculation model was established. This invention creatively incorporates both the unconformity dip angle measured from core samples and the uplift dip angle interpreted from seismic data into the calculation model, constructing a geometric conversion formula for "apparent thickness - true thickness." This model comprehensively considers both the original dip during strata deposition and subsequent tectonic deformation, more closely reflecting the actual occurrence state of geological bodies, and the calculation results are more geologically significant. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a flowchart illustrating the method and system for determining the true thickness of a formation according to the present invention. Figure 2 This is a schematic diagram of the landmark interface between two different lithologies in a rock core; Figure 3 This is a schematic diagram of the bedding planes within the same lithology in the core sample. Figure 4 This is a schematic diagram representing the landmark interface where lithology undergoes erosion. Figure 5 A schematic diagram illustrating the changes in tectonic movements of the strata; Figure 6 This is a schematic diagram of a three-dimensional geometric model for measuring the thickness of strata in accordance with the present invention. Detailed Implementation
[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.
[0020] like Figure 1 As shown, the present invention provides a method for determining the true thickness of a formation, comprising the following steps: S1: Obtain the apparent thickness of the target formation based on the well logging and well logging data of the target formation.
[0021] In a specific embodiment, step S1 specifically includes the following sub-steps: S11: Select a horizontal well in the target formation and obtain logging data and well logging data of the horizontal well; S12: Based on the well logging data and the well logging data, obtain the depth and location of the horizontal well; S13: Select a marker layer from the core sample of the horizontal well and obtain the corresponding depth of the marker layer; S14: Collect all marker layers and their corresponding depths, and divide the original formation corresponding to the horizontal well according to the marker layers; S15: Select two adjacent marker layers and calculate the apparent thickness of the target formation based on the well depth of the two adjacent marker layers.
[0022] In one specific embodiment, in step S13, as follows: Figure 2 As shown, the selection criteria for the marker layer are: significant lithological characteristics that can be identified by the naked eye on the rock core; and stable distribution that allows for continuous tracing of stratigraphic units on the rock core.
[0023] S2: Obtain the total dip angle and unconformity dip angle of the target stratum based on the rock core of the target stratum.
[0024] In a specific embodiment, step S2 specifically includes the following sub-steps: S21: Establish an angle statistical model for the rock core; S22: Based on the aforementioned angle statistical model, obtain the interfaces at different depths within the same lithology (e.g., ...). Figure 3 (as shown) S23: Based on the interface, the average dip angle is obtained by averaging the angles of the same stratum. The average dip angle is the total dip angle. S24: Based on the angle statistical model, obtain the interface angles between different depths and different lithologies; S25: Calculate the average value of the interface angle to obtain the tilt angle of the unconformity surface.
[0025] In a specific embodiment, in step S21, the angle statistical model is obtained by establishing the following sub-steps: based on the core of the target stratum, identify the interface of lithological change in the core and the bedding in the same lithology, measure and count the angles under different states, thereby obtaining the angle statistical model.
[0026] S3: Obtain the uplift dip angle of the target stratum based on the seismic data of the target stratum.
[0027] In a specific embodiment, step S3 specifically includes the following sub-steps: S31: Obtain seismic data of the target strata, and determine the overall dip interface of the strata in the later stage of deposition based on the differences in reflection morphology and fault characteristics interpreted from the seismic data. S32: Calculate the angle between the overall tilt interface of the strata in the later stage of deposition and the horizontal reference surface to obtain the uplift dip angle.
[0028] It should be noted that the order of steps S1-S3 can be changed, and the order of steps in the above embodiment is only the preferred order of steps in this invention.
[0029] S4: Establish a true thickness calculation model for the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle.
[0030] In one specific embodiment, the formation true thickness calculation model is as follows: (1) In the formula: L is the true thickness of the formation; θ is the total dip angle; α is the dip angle of the unconformity surface; γ is the uplift dip angle; H is the apparent thickness.
[0031] In the above embodiments, such as Figure 4-6 As shown, this invention uses the total dip angle θ, the unconformity dip angle α, and the uplift dip angle γ to calculate the formation dip angle β, which can reflect the actual dip angle of the formation under the combined action of sedimentation and tectonic movement, thus improving the accuracy of the formation true thickness calculation results.
[0032] S5: Calculate the true thickness of the target stratum based on the true thickness calculation model of the stratum.
[0033] In this invention, by using rock cores to identify and delineate marker layers and measure sedimentary unconformities, combined with the principles of solid geometry, the apparent thickness (oblique thickness) obtained from well logging data is converted into the true thickness of the formation. This effectively overcomes the problems of field compass measurements being limited by outcrop conditions and large human errors, as well as the problems of multiple interpretations and systematic biases caused by the heterogeneity of the medium in ground penetrating radar methods.
[0034] On the other hand, the present invention also provides a system for determining the true thickness of a formation, comprising: The apparent thickness acquisition module is used to acquire the apparent thickness of the target formation based on well logging and well logging data. The total dip angle acquisition module is used to obtain the total dip angle of the target formation based on the core sample of the target formation. The unconformity dip angle acquisition module is used to obtain the unconformity dip angle of the target formation based on the core sample of the target formation. The uplift dip angle module is used to obtain the uplift dip angle of the target strata based on the seismic data of the target strata. The true thickness calculation model module is used to establish a true thickness calculation model of the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle, and to calculate the true thickness of the target formation based on the true thickness calculation model of the formation.
[0035] In a specific embodiment, taking a well in the Tarim Basin oilfield as an example, the method for determining the true thickness of the formation described in this invention is used to determine its true thickness, specifically including the following steps: (1) Obtaining apparent thickness Obtain complete core samples from the target well section. Through geological logging, conduct detailed observation of the core samples, and divide them into different stratigraphic units or lithological layers based on characteristics such as lithology, color, grain size, and fossil content. For the target study section, directly measure the length between the top and bottom interfaces of the stratum on the core using depth measurement tools, or directly read it from the drilling core data. This length is the apparent thickness of the stratum along the borehole trajectory (denoted as H).
[0036] (2) Obtain the lifting angle Seismic logging data from the target well was acquired. Using specialized seismic data processing software, seismic waveforms were extracted, identifying abrupt waveform changes and morphological discontinuities. Differences in travel time and waveform of reflected waves at different stratigraphic interfaces were located, and the angle between the stratigraphic interface and the horizontal reference plane was initially extracted as the dip angle data for the seismic logging layer. Subsequently, existing geological data for the target well area were reviewed, including regional geological survey reports, measured dip angle data from drilling of adjacent wells, and regional tectonic evolution reports. The dip angle data obtained from the seismic logging was compared one by one with the measured dip angle data in the regional geological data to analyze the reasons for discrepancies (such as the influence of heterogeneous seismic wave propagation medium and waveform interpretation errors). Based on the measured data from the regional geological data, the initial dip angle data from the seismic logging was corrected, ultimately determining the overall uplift dip angle of the strata in the area (denoted as γ).
[0037] (3) Obtain the total tilt angle For each stratigraphic segment, three representative measurement points at different depths were selected in the core. At each measurement point, the bedding interface angle within the same lithology in the core was directly measured using a geological compass. The measurement was repeated three times at each location, and the three measurement values were recorded. The average angle of each measurement point was calculated, and the average of the three measurement points was taken as the total dip angle of the stratigraphic segment (denoted as θ).
[0038] (4) Obtain the dip angle of the unconformity surface In the core sample of the target well, interfaces where lithology changes abruptly are identified segment by segment (such as the interface between sandstone and mudstone, or the boundary between sedimentary structures of different lithologies). For each unconformity, three measurement points at different locations are selected. At each measurement point, the dip angle of the lithological change interface is directly measured using a geological compass. The measurement is repeated three times at each location, and the three measurement values are recorded. The average dip angle of each measurement point is calculated, and the average value of the three measurement points is taken as the dip angle of the stratigraphic unconformity of that stratigraphic segment (denoted as α).
[0039] (5) Establish the formation true thickness calculation model shown in equation (1), and calculate the formation true thickness by combining the data obtained in steps (1)-(4).
[0040] In this embodiment, the true thickness L obtained from solving each formation segment is superimposed to obtain the true thickness ∑L of the entire well. The measurement and calculation sources of each data are clearly marked to ensure that the calculation process is traceable and verifiable.
[0041] (6) Result verification and correction To ensure the accuracy of the calculated true thickness of the formation, the converted true thickness values were verified and corrected.
[0042] Repeat the measurement of the core samples in step (1), select three new core samples from the same stratum, obtain the dip angle of the unconformity surface of the stratum according to the same compass orientation measurement method, and recalculate the average dip angle of the unconformity surface of the stratum in combination with the original valid measurement data; at the same time, redefine the core thickness of the target stratum and repeatedly obtain the apparent thickness data.
[0043] The true thickness data calculated in step (5) is compared and analyzed with the measured lithological thickness description of the target well core and the intuitive thickness record of the formation interface during the logging process to verify whether the true thickness data matches the intuitive information measured in the core. If the deviation of the true thickness of a single formation exceeds 5%, the entire process of measuring the apparent thickness of the formation segment and collecting data at various angles (compass measurement / seismic logging / data calibration) in step (1) is re-examined to identify measurement errors, data entry errors and other problems, and targeted corrections are made.
[0044] In this embodiment, the true thickness of the formation is determined through the above steps. Compared with the prior art, this invention does not rely on field outcrop measurements, avoiding human error and environmental limitations associated with field compass measurements. Verification has shown that the deviation between the calculated true thickness of the formation and the actual thickness of the formation is controlled within a reasonable range, and the accuracy meets the practical engineering needs of oilfield geological exploration and reserve calculation. It has the advantages of simple operation, reliable data, high accuracy, and strong applicability.
[0045] It should be noted that although this invention no longer relies on surface outcrops but instead utilizes core data obtained through drilling, the cores may be damaged, weathered, or fractured during drilling and preservation. Therefore, when using this invention, it is necessary to screen and exclude measurement points from damaged cores.
[0046] In addition, although the present invention takes an average of multiple measurements at a location, the operation of the compass depends on the accuracy of the measurement personnel's readings, which can lead to problems such as reading deviations and non-standard compass placement angles. Therefore, a high-precision electronic angle measuring instrument can be used to measure with two tools in combination, thereby reducing human reading errors.
[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations 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 alterations 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 method for determining the true thickness of a formation, characterized in that, Includes the following steps: S1: Obtain the apparent thickness of the target formation based on the well logging and well logging data of the target formation; S2: Obtain the total dip angle and unconformity dip angle of the target stratum based on the rock core of the target stratum; S3: Obtain the uplift dip angle of the target stratum based on the seismic data of the target stratum; S4: Establish a true thickness calculation model for the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle; S5: Calculate the true thickness of the target stratum based on the true thickness calculation model of the stratum.
2. The method for determining the true thickness of a formation according to claim 1, characterized in that, Step S1 specifically includes the following sub-steps: S11: Select a horizontal well in the target formation and obtain logging data and well logging data of the horizontal well; S12: Based on the well logging data and the well logging data, obtain the depth and location of the horizontal well; S13: Select a marker layer from the core sample of the horizontal well and obtain the corresponding depth of the marker layer; S14: Collect all marker layers and their corresponding depths, and divide the original formation corresponding to the horizontal well according to the marker layers; S15: Select two adjacent marker layers and calculate the apparent thickness of the target formation based on the well depth of the two adjacent marker layers.
3. The method for determining the true thickness of a formation according to claim 2, characterized in that, In step S13, the selection criteria for the marker layer are: significant lithological characteristics that can be identified by the naked eye on the rock core; and stable distribution that can be continuously traced on the rock core to identify stratigraphic units.
4. The method for determining the true thickness of a formation according to claim 1, characterized in that, Step S2 specifically includes the following sub-steps: S21: Establish an angle statistical model for the rock core; S22: Based on the aforementioned angle statistical model, obtain the interfaces at different depths within the same lithology; S23: Based on the interface, the average dip angle is obtained by averaging the angles of the same stratum. The average dip angle is the total dip angle. S24: Based on the angle statistical model, obtain the interface angles between different depths and different lithologies; S25: Calculate the average value of the interface angle to obtain the tilt angle of the unconformity surface.
5. The method for determining the true thickness of a formation according to claim 4, characterized in that, In step S21, the angle statistical model is established through the following sub-steps: based on the core of the target stratum, the interfaces of lithological changes and the bedding in the same lithology are identified in the core, and the angles under different conditions are measured and statistically analyzed to obtain the angle statistical model.
6. The method for determining the true thickness of a formation according to claim 1, characterized in that, Step S3 specifically includes the following sub-steps: S31: Obtain seismic data of the target strata, and determine the overall dip interface of the strata in the later stage of deposition based on the differences in reflection morphology and fault characteristics interpreted from the seismic data. S32: Calculate the angle between the overall tilt interface of the strata in the later stage of deposition and the horizontal reference surface to obtain the uplift dip angle.
7. The method for determining the true thickness of a formation according to any one of claims 1-6, characterized in that, In step S4, the model for calculating the true thickness of the formation is as follows: （1） In the formula: L is the true thickness of the formation; θ is the total dip angle; α is the dip angle of the unconformity surface; γ is the uplift dip angle; H is the apparent thickness.
8. A system for determining the true thickness of a formation, characterized in that, include: The apparent thickness acquisition module is used to acquire the apparent thickness of the target formation based on well logging and well logging data. The total dip angle acquisition module is used to obtain the total dip angle of the target formation based on the core sample of the target formation. The unconformity dip angle acquisition module is used to obtain the unconformity dip angle of the target formation based on the core sample of the target formation. The uplift dip angle module is used to obtain the uplift dip angle of the target strata based on the seismic data of the target strata. The true thickness calculation model module is used to establish a true thickness calculation model of the formation based on the apparent thickness, total dip angle, unconformity dip angle, and uplift dip angle, and to calculate the true thickness of the target formation based on the true thickness calculation model of the formation.