A method for dividing a favorable area of a dune body

Abstract

The application discloses a method for dividing favorable zones of a dune beach body, comprising the following steps: S1, determining the data range of a target layer based on post-stack seismic data, and picking up the horizon of the target layer; S2, determining the response characteristics of high-quality reservoirs; S3, calculating the stratum thickness of the target layer and the number of extreme points in the target layer, and determining the range C of a beach edge; S4, screening the seismic attribute response characteristics of high-quality reservoirs from the response characteristics of high-quality reservoirs, and determining the favorable range of each seismic attribute; S5, obtaining the intersection of the favorable range of each seismic attribute and the range C of the beach edge, and obtaining the most favorable zone range X of the target layer; S6, obtaining the intersection of the union of the range C of the beach edge and the favorable range of each seismic attribute, and obtaining the range A' of the set of the favorable range of the seismic attribute on the beach edge; and the range Q of the secondary favorable zone range is obtained by removing the range of the most favorable zone range X from the range A'. The application has the advantages of high division precision, and simultaneously divides the favorable zone and the secondary favorable zone in the dune beach body.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, and specifically to a method for delineating favorable areas of hilly and shoal bodies. Background Technology

[0002] Among various types of gas reservoirs in oil and gas exploration, carbonate gas reservoirs are a type of conventional oil and gas reservoir. Hill shoals are a type of carbonate reservoir, widely developed in medium- to high-energy environments such as open platforms and platform margins. For example, the Dengying Formation of the Sinian System in the Sichuan Basin has multiple sets of carbonate karst weathering crust reservoirs, most of which are high-quality hill shoal sedimentary facies, with platform margin hill shoals being the most favorable reservoirs. These strata were initially located in shallow seas at the platform margins during deposition. Later, they were subjected to freshwater dissolution, weathering, and tectonic movements, forming numerous intergranular and intercrystalline solution pores, caves, dissolution fractures, and tectonic fractures, significantly improving reservoir performance. However, even within the same platform margin sedimentary environment, different regions have different diagenetic conditions, and the degree of subsequent dissolution and weathering, as well as tectonic alteration, varies. Consequently, the physical properties of the reservoirs differ, and the development of pores, dissolution cavities, and fractures also varies significantly in space. The location of relatively developed fractures and cavities is the favorable area to be found, and relatively favorable areas should be given priority when deploying well locations.

[0003] Existing techniques for horizontally delineating favorable areas of hill-shoal bodies generally integrate core, thin section, well logging, and geochemical data. They perform gridded interpolation on the plane to obtain a reservoir thickness contour map, and determine the extent of the hill-shoal body based on the thickness. Alternatively, they can use seismic data attributes, inversion, and other methods to delineate the extent of the hill-shoal body based on the relative value range of the reservoir.

[0004] Existing interpolation methods suffer from low accuracy, and the resulting favorable areas are too smooth, easily missing detailed information between interpolation points. Methods using seismic attributes or inversion are relatively accurate, but they cannot distinguish between favorable and less favorable areas. Summary of the Invention

[0005] The purpose of this invention is to provide a method for delineating the favorable areas of a hilly or shoal body, which has the advantage of high delineation accuracy and can simultaneously delineate the favorable and secondary favorable areas in the hilly or shoal body.

[0006] This invention is achieved through the following technical solution:

[0007] A method for delineating favorable areas of hilly areas includes the following steps:

[0008] S1. Determine the data range of the target layer based on post-stack seismic data, and pick the layer position of the target layer, including the top boundary seismic layer and the bottom boundary seismic layer;

[0009] S2. Compare and analyze reservoir interpretation data from well logging geology with seismic interpretation data to determine the response characteristics of high-quality reservoirs;

[0010] S3. Calculate the formation thickness of the target layer and the number of extreme points within the target layer as described in step S1; based on the critical values ​​of the thickness and the number of extreme points of the platform margin beach, determine the favorable range of thickness T and the favorable range of extreme points P of the platform margin beach, and obtain the range C of the platform margin beach by finding the intersection of the favorable range of thickness T and the favorable range of extreme points P.

[0011] S4. Select the seismic attribute response features of high-quality reservoirs from the high-quality reservoir response features obtained in step S2, extract the corresponding seismic attributes, and obtain the favorable range of each seismic attribute based on the critical value of the seismic attribute.

[0012] S5. Find the intersection of the favorable range of each seismic attribute obtained in step S4 and the range C of the platform edge beach obtained in step S3, and obtain the most favorable range X of the target layer.

[0013] S6. Find the intersection of the union of the range C of the platform edge and the ranges favorable for each seismic attribute, and obtain the range A' of the set of ranges favorable for seismic attributes on the platform edge. The range Q of the range A' excluding the most favorable range X is the second most favorable range.

[0014] The post-stack seismic data described in this invention is the basic data and can be directly obtained. Reservoir interpretation data and seismic interpretation data are also directly obtainable.

[0015] Since the thickness of the shoal body is an indicator that distinguishes it from other shoals, stratigraphic thickness is a relatively important characteristic. Furthermore, the seismic waveforms of shoals on seismic profiles are generally more chaotic, with a greater number of extreme points. This characteristic can be used to distinguish shoals from other shoals with more stable reflection waveforms. Therefore, this invention extracts the characteristics (stratigraphic thickness and number of extreme points) of the shoal body's shoal body, effectively distinguishing the relatively favorable sedimentary facies zones within the shoal body. Simultaneously, this invention utilizes multiple seismic data features of the most prominent favorable areas of the shoal body. Based on these multiple seismic data features and the shoal body itself, the most favorable area is comprehensively determined, resulting in a more accurate and reliable method than well interpolation.

[0016] Furthermore, the present invention uses the method of finding intersection and union, which can simultaneously divide the most advantageous region and the second most advantageous region.

[0017] Furthermore, in step S1, the stratigraphic level also includes the intermediate stratigraphic level of the target layer, which can also be called the internal stratigraphic level, so as to extract local features in subsequent steps, depending on the specific stratigraphic conditions.

[0018] Furthermore, the specific process of step S2 is as follows:

[0019] By comparing and analyzing reservoir interpretation data from well logging geology with seismic interpretation data, we can identify the significant differences between high-quality and low-quality reservoirs, and determine the response characteristics of high-quality reservoirs based on these significant differences.

[0020] Specifically, the reservoir interpretation data from well logging geology is analyzed in correspondence with seismic interpretation data. Beaches with well-developed pores, vaults, and fractures (high-quality reservoirs) and those without (low-quality reservoirs) are compared from multiple perspectives to identify significant differences. These differences include, but are not limited to: 1. Formation thickness; 2. Waveform, intensity, vertical combination, and lateral continuity of seismic phase axes; 3. Amplitude, frequency, and phase information of seismic waves; 4. Geometric characteristics of the formation, such as curvature, faulting, and dip angle; 5. Inverted geophysical parameters, etc.

[0021] Furthermore, the methods for obtaining the response characteristics of high-quality reservoirs include seismic waveform profiles, seismic attributes, and inversion results.

[0022] Furthermore, in step S3, the method for determining the stratigraphic thickness of the target layer is as follows: for each seismic trace, the time (or depth) of the top boundary seismic horizon of the tracked target layer is subtracted from the time (or depth) of the bottom boundary seismic horizon.

[0023] Furthermore, in step S3, the number of extreme points is calculated as follows:

[0024] For each seismic trace, calculate the number of locations where the first derivative of the seismic signal x(t) between the top and bottom seismic horizons of the target layer is 0. In the case of actual discrete signals, the number of positive and negative differences in the signal x(t) can be determined.

[0025] Furthermore, in step S3, the critical values ​​for the thickness of the steppe shoal and the critical values ​​for the number of extreme points are statistically obtained from the seismic profile by random sampling.

[0026] Furthermore, in step S4, the number of seismic attribute response characteristics of high-quality reservoirs is greater than or equal to two. These include, but are not limited to, curvature attributes, coherence attributes, instantaneous frequency, and wave impedance inversion.

[0027] Furthermore, color is used to distinguish the most advantageous area X and the second most advantageous area Q.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. The classification method of the present invention is a combination of well and seismic analysis, which determines the platform margins and shoals in the hill and shoal body based on the formation thickness and the number of extreme points. It makes full use of the advantage of the lateral prediction accuracy of seismic data, and uses the characteristic seismic attributes of various high-quality reservoirs for comprehensive classification, which has the advantages of high accuracy and good effectiveness.

[0030] 2. This invention uses the methods of finding intersection and union to simultaneously divide the most advantageous area and the second most advantageous area, and the result has a high degree of consistency with the actual situation. Attached Figure Description

[0031] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is a flowchart of the present invention;

[0033] Figure 2 This is a diagram showing the result after partitioning in Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0035] Example 1:

[0036] like Figure 1 As shown, a method for delineating favorable areas of hilly areas includes the following steps:

[0037] S1. Determine the data range of the target layer based on post-stack seismic data and pick the horizons of the target layer. The horizons include the top boundary seismic horizon and the bottom boundary seismic horizon. Picking the seismic horizons is a conventional method of seismic data interpretation and there are no method restrictions. You can pick only the top and bottom boundaries, or you can supplement by picking internal horizons to extract local features in subsequent steps, depending on the specific stratigraphic conditions.

[0038] S2. Compare and analyze the reservoir interpretation data from well logging geology with the seismic interpretation data to determine the significant differences between high-quality reservoirs and non-high-quality reservoirs. Based on these significant differences, determine the response characteristics of high-quality reservoirs.

[0039] Specifically, the reservoir interpretation data from well logging geology is analyzed in correspondence with seismic interpretation data. Beaches with well-developed pores, vaults, and fractures (high-quality reservoirs) and those without (low-quality reservoirs) are compared from multiple perspectives to identify significant differences. These differences include, but are not limited to: 1. Formation thickness; 2. Waveform, intensity, vertical combination, and lateral continuity of seismic phase axes; 3. Amplitude, frequency, and phase information of seismic waves; 4. Geometric characteristics of the formation, such as curvature, faulting, and dip angle; 5. Inverted geophysical parameters, etc.

[0040] S3. Calculate the formation thickness of the target layer and the number of extreme points within the target layer as described in step S1, and form a thickness plan map and an extreme point count plan map; based on the critical thickness value and the critical value of the number of extreme points of the platform margin beach, and according to the critical thickness value and the critical value of the number of extreme points of the platform margin beach, delineate the favorable range T of the platform margin beach thickness and the favorable range P of the number of extreme points of the platform margin beach on the plan map, and find the intersection to obtain the platform margin beach range C = T ∩ P;

[0041] In this step, since the thickness of the shoal body is an indicator that distinguishes the platform margin shoal from other shoals, stratigraphic thickness is a relatively important characteristic. The method for determining the stratigraphic thickness of the target layer is as follows: for each seismic trace, subtract the time (or depth) of the top boundary seismic horizon from the time (or depth) of the bottom boundary seismic horizon of the target layer. Because the seismic waveforms of platform margin shoals are generally more chaotic and have more extreme points when observed on seismic profiles, this characteristic can be used to distinguish platform margin shoals from other shoals with more stable reflection waveforms. The method for determining the number of extreme points within the target layer is as follows: for each seismic trace, calculate the number of locations where the first derivative of the seismic signal x(t) between the top and bottom boundaries of the target layer is 0. In the case of actual discrete signals, the number of positive and negative changes in the difference of the signal x(t) is calculated. This calculation method is a commonly used mathematical algorithm.

[0042] The critical values ​​for the thickness and number of extreme points of the platform margin shoal can be obtained statistically from geological, well logging data or seismic profiles through random sampling. These values ​​should be able to basically distinguish the platform margin shoal from other types of shoal bodies.

[0043] S4. Select high-quality reservoir seismic attribute response features from the high-quality reservoir response features obtained in step S2; extract the corresponding seismic attributes (A1~Ak), and extract attribute values ​​along the target layer by opening a time window to form the corresponding k planar maps; based on the seismic attribute critical value, obtain the favorable range of each seismic attribute, the favorable range of each seismic attribute is divided into S1~Sk, and obtain the set S'=S1∪S2∪…∪Sk of the favorable range of all feature attributes;

[0044] In this step, the selected high-quality reservoir seismic attribute response characteristics are generally two or more types, including but not limited to curvature attributes, coherence attributes, instantaneous frequency, and wave impedance inversion; the high-quality reservoir response characteristics are obtained by seismic waveform profiles, seismic attributes, and inversion results.

[0045] In this step, the critical values ​​of the seismic attribute response characteristics of various high-quality reservoirs are qualitatively given based on the value range distribution of various attributes and comparative analysis with well logging and geological data. These values ​​should be able to roughly distinguish the regions of high-quality reservoirs and should not be too large or too small.

[0046] S5. Find the intersection of the favorable range of each seismic attribute obtained in step S4 and the range C of the platform edge beach obtained in step S3, and obtain the most favorable range X of the target layer, X=C∩S1∩S2∩…∩Sk.

[0047] S6. Find the intersection of the union of the range C of the platform edge and the range S' of each seismic attribute to obtain the range A' of the set of seismic attribute favorable ranges on the platform edge, A' = C ∩ S'. The range of favorable range A' excluding the most favorable range X is the second most favorable range Q, Q = A' - X.

[0048] In this embodiment, the delineation of the advantageous area can be achieved by obtaining the critical value contour lines, or by adjusting the color scales on the planar map and then manually outlining the area along the critical value color boundaries; there are no specific method restrictions. The methods for calculating intersections, unions, and other regions are general mathematical set operations.

[0049] After completing steps S1-S6, the planar ranges of the most favorable area X and the second most favorable area Q of the platform edge beach are obtained.

[0050] The application of this embodiment in the Dengying Formation gas reservoir in a research area of ​​Sichuan is as follows:

[0051] The target stratum is the Dengying Formation of the Sinian System, located in the eastern part of the Caledonian Uplift in the Sichuan Basin. During the Tongwan-Caledonian period, it underwent multiple tectonic movements, resulting in multiple unconformities. This facilitated the development of multiple sets of high-quality karst weathering crust reservoirs in the Dengying Formation to Lower Paleozoic strata, characterized by numerous pores and vulnerabilities, and locally, fractures. The purpose of this application is to delineate favorable reservoir areas within the platform margin shoal of the target stratum.

[0052] The implementation process is as follows:

[0053] 1) Prepare post-stack seismic data and determine the data range of the target layer.

[0054] 2) Pick the top and bottom seismic horizons of the target layer, as well as the internal horizons of the target layer, in order to determine its internal characteristics:

[0055] The top boundary seismic horizon E1q of the fourth segment of the Dengying Formation, the bottom boundary seismic horizon Z2Dn3 of the third segment of the Dengying Formation, and the upper bottom boundary Z2Dn4s of the fourth segment of the Dengying Formation were collected.

[0056] 3) Analyze the response characteristics of the reservoir, including seismic waveform profiles, seismic attributes, and inversion results:

[0057] Analysis of the seismic waveform profile, seismic attributes, and inversion results of the reservoir reveals the following characteristics that distinguish the high-quality reservoirs in the platform margin shoals or platform margin shoals from other types of shoal strata: 1. The E1q~Z2Dn4s strata are thicker; 2. The lateral continuity of seismic phase axis reflections is poor, and the overall structure is relatively chaotic, resulting in numerous extreme points between E1q~Z2Dn3; 3. The E1q~Z2Dn4s strata exhibit significant local twisting and bending characteristics in areas with fracture-vuggy development; 4. The inversion values ​​of the E1q~Z2Dn4s wave impedance are relatively lower in areas with fracture-vuggy development and high gas production compared to other locations.

[0058] 4) Determine the stratigraphic thickness of the target layer and the number of extreme points within the target layer based on the seismic horizons at the top and bottom boundaries of the target layer, and generate a thickness planar map and an extreme point count planar map:

[0059] The method for determining the target layer thickness is as follows: for each seismic trace, subtract the time of the top boundary seismic layer E1q from the time of the target layer Z2Dn4s to obtain the target layer thickness plan.

[0060] The method to determine the number of extreme points within E1q~Z2Dn3 is as follows: for each seismic trace, calculate the positive and negative changes in the difference between the seismic layers E1q~Z2Dn3 to obtain a plane map of the number of extreme points in the target layer.

[0061] 5) Analyze the characteristics of high-quality reservoirs, select the seismic attribute response characteristics of high-quality reservoirs, extract the corresponding seismic attributes, and extract attribute values ​​along the target layer by opening a time window to form the corresponding planar map:

[0062] The selected high-quality reservoir seismic attributes include: curvature attribute (A1), symmetry attribute (A2) - reflecting the local torsion and bending characteristics of the formation; and relative acoustic impedance attribute (A3) - reflecting the characteristics of fractured and vulcanized reservoirs. These three attributes are then calculated to obtain the corresponding attribute volumes.

[0063] 6) The critical values ​​of the thickness of the platform margin and the critical values ​​of the number of extreme points are obtained from the seismic profile by random sampling. Based on these values, the favorable range of platform margin thickness T and the favorable range of the number of extreme points P are delineated on the plan view. The intersection is then used to obtain the platform margin range C = T∩P.

[0064] 7) By statistically analyzing the value range distribution of the selected attributes A1, A2, and A3 in the high-quality reservoir area, the critical value of each high-quality reservoir is obtained. Based on this value, the favorable range S1 to S3 of each characteristic attribute is delineated on the plane, and the set of favorable ranges of all characteristic attributes S' = S1∪S2∪S3 is obtained.

[0065] 8) Find the intersection of all regions to obtain the most favorable region range X = C∩S1∩S2∩S3;

[0066] 9) Find the range A' = C∩S' of the set S' of all the advantageous areas of the characteristic attributes on the platform edge beach, and then subtract the advantageous area range X to obtain the secondary advantageous area range Q = A'-X.

[0067] After completing steps (1) to (9), the planar extents of the most favorable area X and the second most favorable area Q of the platform margin beach in this study area are obtained, as follows: Figure 2 As shown, the preferred attribute curvature and symmetry attribute plane diagrams are overlaid, and the most favorable area (dark gray area) and the second most favorable area (light gray area) are drawn. Later, high-yield wells (black) and medium-low-yield wells (white) will be marked. It can be seen that most high-yield wells are located in the most favorable area, while some medium-low-yield wells are located in the most favorable area and some in the second most favorable area, thus demonstrating the effectiveness of the hill-shoal body favorable area division method of the present invention.

[0068] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for delineating favorable areas of hilly and shoal formations, characterized in that, Includes the following steps: S1. Determine the data range of the target layer based on post-stack seismic data, and pick the layer position of the target layer, including the top boundary seismic layer and the bottom boundary seismic layer; S2. Compare and analyze reservoir interpretation data from well logging geology with seismic interpretation data to determine the response characteristics of high-quality reservoirs; S3. Calculate the formation thickness of the target layer and the number of extreme points inside the target layer as described in step S1; Based on the critical values ​​of thickness and number of extreme points of the platform edge beach, the favorable range of thickness T and the favorable range of number of extreme points P of the platform edge beach are determined. The range C of the platform edge beach is obtained by finding the intersection of the favorable range of thickness T and the favorable range of number of extreme points P. The number of extreme points is calculated as follows: Calculate the number of locations where the first derivative of the seismic signal x(t) is 0 between the top and bottom boundaries of the target layer; S4. Select high-quality reservoir seismic attribute response features from the high-quality reservoir response features obtained in step S2, extract the corresponding seismic attributes, and obtain the favorable range of each seismic attribute based on the seismic attribute critical value; the number of high-quality reservoir seismic attribute response features is greater than or equal to two. S5. Find the intersection of the favorable range of each seismic attribute obtained in step S4 and the range C of the platform edge beach obtained in step S3, and obtain the most favorable range X of the target layer. S6. Find the intersection of the union of the range C of the platform edge and the ranges favorable for each seismic attribute, and obtain the range A' of the set of ranges favorable for seismic attributes on the platform edge. The range Q of the range A' excluding the most favorable range X is the second most favorable range.

2. The method for delineating favorable areas of hilly areas according to claim 1, characterized in that, In step S1, the layer also includes the intermediate layer of the target layer.

3. The method for delineating favorable areas of hilly areas according to claim 1, characterized in that, The specific process of step S2 is as follows: By comparing and analyzing reservoir interpretation data from well logging geology with seismic interpretation data, we can identify the significant differences between high-quality and low-quality reservoirs, and determine the response characteristics of high-quality reservoirs based on these significant differences.

4. The method for delineating favorable areas of hilly terrain according to claim 1, characterized in that, In step S2, the high-quality reservoir response characteristics include formation thickness; waveform, intensity, vertical combination form and lateral continuity of seismic phase axes; amplitude, frequency and phase information of seismic waves; geometric characteristics of the formation; and inverted geophysical parameters.

5. The method for delineating favorable areas of hilly terrain according to claim 4, characterized in that, The methods for obtaining the response characteristics of high-quality reservoirs include seismic waveform profiles, seismic attributes, and inversion results.

6. The method for delineating favorable areas of hilly terrain according to claim 1, characterized in that, In step S3, the stratum thickness is the bottom boundary seismic horizon time / depth minus the top boundary seismic horizon time / depth of the target layer.

7. The method for delineating favorable areas of hilly terrain according to claim 1, characterized in that, In step S3, the critical values ​​for the thickness of the steppe shoal and the critical values ​​for the number of extreme points are statistically obtained from the seismic profile by random sampling.

8. A method for delineating favorable areas of hilly terrain according to any one of claims 1-7, characterized in that, The most advantageous area X and the second most advantageous area Q are distinguished by color.

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