Method for reef reservoir prediction based on seismic along-bed minimum negative curvature attribute

Abstract

The present application provides a reef reservoir prediction method based on seismic along-layer minimum negative curvature attribute, which comprises: establishing a geological model of reef reservoir and underlying strata; according to the established geological model, forward modeling is carried out, and the minimum negative curvature attribute is extracted along the underlying strata horizon according to the forward modeling result. The present application excludes the horizon interpretation problem caused by the top boundary string phase problem due to the development of reef and the inaccurate inversion problem caused by the inaccurate low-frequency model establishment, and directly predicts the reef reservoir thickness and comprehensive physical properties by using the minimum negative curvature of underlying stable strata, thereby solving the problems of multiple steps, great difficulty and low precision in the traditional reef reservoir prediction by inversion, and forming a fast and efficient reservoir prediction method, which is beneficial to the target optimization and efficient development of reef gas reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development, and specifically to a method for predicting bioherm reservoirs based on seismic attributes. Background Technology

[0002] Currently, various methods exist for reservoir prediction in bioherms both domestically and internationally. Among these, seismic prediction methods mainly include seismic attribute analysis and seismic impedance inversion. Seismic attribute analysis primarily focuses on the seismic properties of the bioherm itself, but reservoir prediction is extremely difficult when the seismic response characteristics of the bioherm are unclear. Seismic impedance inversion relies on the accuracy of multiple steps, including stratigraphic interpretation and rock physical analysis, which are numerous and challenging. For example, patent application CN104977611A discloses a bioherm reservoir sculpting method, in which the top and bottom of the bioherm are sculpted based on the seismic profile and impedance profile of the bioherm, and constrained by seismic facies and sedimentary facies. Patent application CN110568488A discloses a bioherm reservoir identification method based on a nonlinear chaotic algorithm, which mainly relies on seismic inversion. Both of these methods depend on the seismic profile and impedance inversion of the bioherm itself, and the interpretation of the top and bottom of the bioherm depends on the interpretation of geologists.

[0003] Due to the development of pores and fractures and the presence of natural gas, bioherm reservoirs exhibit velocity-density differences compared to non-reservoir and surrounding rocks. This leads to increased travel time and pull-down of the in-phase axis in the region below the bioherm reservoir development area on seismic time migration profiles.

[0004] Because bioherms are a special type of geological body, their deposition rate is higher than that of the surrounding strata and their development is random. Therefore, bioherms are characterized by complex spatial morphology and rapid lateral changes. Their reservoir development is controlled by multiple factors, making it even more complex. In known bioherm examples, stratigraphic phase crossover occurs at the top and bottom of the bioherm, which is difficult to interpret and requires highly skilled geological interpreters. Inaccurate interpretation of stratigraphic boundaries at the top and bottom of the bioherm, inaccurate modeling of the bioherm's interior, and inaccurate rock physical analysis can all easily lead to inaccurate predictions of bioherm reservoir distribution in the final seismic inversion. These multiple factors contribute to the inaccuracy of bioherm reservoir prediction and are also unfavorable factors restricting the efficient exploration and development of bioherm gas reservoirs. Summary of the Invention

[0005] To address the shortcomings of the aforementioned bioherm reservoir prediction techniques, this invention provides a method for predicting bioherm reservoirs by utilizing the minimum negative curvature attribute along the stable strata beneath the bioherm reservoir.

[0006] The present invention provides a bioherm reservoir prediction method based on the minimum negative curvature attribute along seismic layers, comprising:

[0007] Establish a geological model of the bioherm reservoir and underlying strata;

[0008] Based on the established geological model, forward modeling is performed, and the minimum negative curvature attribute is extracted along the underlying strata based on the forward modeling results.

[0009] Furthermore, the establishment of the geological model of the bioherm reservoir and underlying strata includes:

[0010] Determine the development pattern of bioherm reservoirs and the morphology of underlying strata;

[0011] Based on the development pattern of bioherm reservoirs and the morphology of underlying strata, a geological model of bioherm reservoirs and underlying stable strata is established.

[0012] Furthermore, the step of performing forward modeling based on the geological model and extracting the minimum negative curvature attribute along the underlying strata based on the forward modeling results includes:

[0013] Based on the geological model, elastic wave forward modeling was performed, and pre-stack depth migration was performed to obtain the forward modeling profile.

[0014] Stratigraphic tracking is performed on the underlying strata on the pre-stack time-migrated seismic data volume obtained by forward modeling, and the minimum negative curvature attribute is extracted along the underlying strata.

[0015] Furthermore, the method also includes:

[0016] By extracting the minimum negative curvature attribute along the underlying strata and comparing it with reservoir development in various models, a correspondence between the minimum negative curvature attribute and bioherm reservoir development was established.

[0017] Furthermore, the process of performing elastic wave forward modeling based on the geological model and performing pre-stack depth migration to obtain the forward modeled profile also includes:

[0018] Based on the undulations of the underlying strata in the reservoir development area of ​​the study area, an identification model for the undulations of the underlying strata in bioherm reservoirs was established.

[0019] Furthermore, the step of performing stratigraphic tracking on the underlying strata on the pre-stack time-migrated seismic data volume obtained through forward modeling, and extracting the minimum negative curvature attribute along the underlying strata stratigraphic horizon, also includes,

[0020] Based on forward modeling and pre-stack time migration studies, the seismic response characteristics of bioherm reservoirs with different thicknesses, widths, distances from the bottom, and physical properties, as well as the underlying strata, were obtained.

[0021] Furthermore, the correspondence includes:

[0022] When the reservoir width is stable, the greater the reservoir thickness, the smaller the minimum negative curvature of the underlying strata.

[0023] When the reservoir width is stable, better physical properties correspond to a larger minimum negative curvature of the underlying strata.

[0024] Furthermore, the correspondence also includes:

[0025] When the reservoir width, thickness and physical properties remain unchanged, except for the negative curvature anomaly caused by interference due to the reservoir being too close to the underlying strata, the other characteristics are that changes in the distance from the bottom will not cause changes in the negative curvature of the underlying strata.

[0026] With the reservoir thickness and physical properties remaining constant, as the width increases, the minimum negative curvature of the underlying strata first decreases and then increases. When the reservoir width is 130m to 170m, the minimum negative curvature of the underlying strata becomes a bimodal shape and remains stable as the width gradually increases thereafter.

[0027] Furthermore, the method also includes:

[0028] The correlation between the minimum negative curvature attribute and the development of bioherm reservoirs was verified by drilling new wells in the work area.

[0029] Furthermore, the method also includes using curvature attribute planar maps and the corresponding relationships to predict bioherm reservoirs and select optimal target sites.

[0030] Compared with existing technologies, the bioherm reservoir prediction method based on the minimum negative curvature attribute along the seismic layer of the present invention has the following advantages:

[0031] (1) The relationship between the thickness, width, physical properties of bioherm reservoirs and the minimum negative curvature of underlying strata in different geological models was established, and a theoretical model was established;

[0032] (2) The theoretical model is used to predict the comprehensive response of bioherm reservoir thickness and physical properties in the work area. The method has been verified by drilling in the area, which solves the problems of multiple steps, high difficulty and inaccuracy in bioherm reservoir prediction, and forms a simple and easy-to-operate bioherm reservoir prediction method.

[0033] The above-mentioned technical features can be combined in various technically feasible ways to produce new implementation schemes, as long as the purpose of the present invention can be achieved. Attached Figure Description

[0034] The invention will now be described in more detail based on embodiments that are merely non-limiting and with reference to the accompanying drawings. Wherein:

[0035] Figure 1 The flowchart of the present invention for predicting bioherm reservoirs using the minimum negative curvature of the underlying strata is shown.

[0036] Figure 2This invention displays bioherm reservoir models of different thicknesses, forward modeling results, and minimum negative curvature attribute maps of underlying strata in embodiments of the present invention.

[0037] Figure 3 The embodiments of the present invention are shown, including bioherm reservoir models of different widths, forward modeling results, and minimum negative curvature attribute maps of underlying strata.

[0038] Figure 4 This invention illustrates the bioherm models at different distances from the bottom, forward modeling results, and the minimum negative curvature attribute map of the underlying strata in embodiments of the present invention.

[0039] Figure 5 This invention displays different physical property models of bioherm reservoirs, forward modeling results, and minimum negative curvature attribute maps of underlying strata in embodiments of the present invention.

[0040] Figure 6 The embodiments of the present invention show the results of bioherm reservoir prediction based on conventional seismic impedance inversion and based on the minimum negative curvature of the underlying strata;

[0041] Figure 7 Verification results of well X16, a newly drilled bioherm reservoir in a certain work area in Sichuan Province, in an embodiment of the present invention.

[0042] In the figures, identical components are labeled with the same reference numerals. The figures are not drawn to scale. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, as long as there is no conflict, the various embodiments and features in each embodiment of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0044] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0045] For any parts not mentioned in this invention, existing technologies can be used or referenced.

[0046] like Figure 1 As shown, the bioherm reservoir prediction method based on the minimum negative curvature attribute along the seismic layer of the present invention includes:

[0047] Step 1: Establish a geological model of the bioherm reservoir and underlying strata;

[0048] In the early stages of implementation, based on existing geophysical data and interpretation results in the study area, the development model of bioherm reservoirs was determined.

[0049] Step 2: Based on the statistical analysis of rock physical parameters and combined with the characteristics of geophysical research, establish geological models of the thickness, width, and physical property changes of different bioherm reservoirs to provide a model basis for subsequent research.

[0050] Step 3: Using the established geological model, conduct elastic wave forward modeling studies and pre-stack depth migration processing studies to obtain forward modeling profiles. Combined with actual seismic data, clarify the undulations of the underlying strata in the reservoir development area of ​​the study area, and establish an identification model for the undulations of bioherm reservoirs and underlying strata.

[0051] Step 4: Perform stratigraphic tracking on the underlying strata on the pre-stack time-migrated seismic data volume obtained from forward modeling, and extract the minimum negative curvature attribute along the stratigraphic horizon of the underlying strata.

[0052] Step 5: Establish the relationship between stratigraphic curvature and reservoir development: By extracting the minimum negative curvature attribute of the underlying strata and comparing it with reservoir development models from multiple sources, a correspondence between the minimum negative curvature attribute and reservoir development is established. This correspondence specifically includes:

[0053] 1) When the reservoir width is stable, the greater the reservoir thickness, the smaller the minimum negative curvature of the underlying strata.

[0054] 2) When the reservoir width is stable, the better the physical properties (the greater the porosity, the smaller the velocity), the greater the minimum negative curvature of the underlying strata.

[0055] 3) When the reservoir width, thickness and physical properties remain unchanged, except for the negative curvature anomaly caused by interference due to the reservoir being too close to the underlying strata, the other characteristics are that changes in the distance from the bottom will not cause changes in the negative curvature of the underlying strata.

[0056] 4) With the reservoir thickness and physical properties remaining constant, as the width increases, the minimum negative curvature of the underlying strata first decreases and then increases. When the reservoir width is around 150m, the minimum negative curvature of the underlying strata becomes a bimodal shape and remains stable as the width gradually increases thereafter.

[0057] Therefore, the minimum negative curvature of the underlying strata represents the comprehensive embodiment of reservoir thickness and physical properties, which can directly reflect the reservoir energy storage coefficient. The smaller the minimum negative curvature of the underlying strata, the larger its energy storage coefficient.

[0058] Step 6: Verify the correspondence through new well drilling in the work area.

[0059] Step 7: Utilize the correspondence to predict the thickness and physical properties of bioherm reservoirs, and optimize the drilling design and target selection for bioherm gas reservoirs.

[0060] This invention, based on the minimum negative curvature attribute along seismic strata, eliminates the challenges of stratigraphic interpretation caused by top boundary phase issues resulting from bioherm development and the inaccuracy of inversion due to inaccurate low-frequency model establishment. It directly predicts the thickness and comprehensive physical properties (energy storage coefficient) of bioherm reservoirs using the minimum negative curvature of underlying stable strata. This solves the problems of numerous steps, high difficulty, and low accuracy in traditional bioherm reservoir prediction methods that rely on inversion, forming a fast and efficient reservoir prediction method that is beneficial for target selection and efficient development of bioherm gas reservoirs.

[0061] like Figures 2-5 As shown, Figures 2 to 5 These include geological models, forward modeling results, and minimum negative curvature maps of the underlying strata for bioherm reservoirs with different thicknesses, widths, distances from the bottom, and physical properties. Figures 2 to 5 Simulation results from Zhongzheng Modeling revealed that the development of bioherm reservoirs can cause pull-down of underlying strata. Through... Figures 2 to 5 The minimum negative curvature attribute map shows that the minimum negative curvature of the underlying stratum represents the comprehensive embodiment of reservoir thickness and physical properties, which can directly reflect the reservoir energy storage coefficient. The smaller the minimum negative curvature of the underlying stratum, the larger its energy storage coefficient.

[0062] The bioherm reservoir prediction method based on the minimum negative curvature attribute along the seismic layer provided by this invention was implemented in a field in a certain work area of ​​the Sichuan Basin.

[0063] Figure 6 The left-middle image shows a planar diagram of the bioherm storage coefficient obtained conventionally based on seismic impedance inversion and porosity inversion in a certain work area of ​​the Sichuan Basin. The right-middle image shows a planar diagram of the bioherm storage coefficient based on the minimum negative curvature of the underlying strata. From a planar perspective, the distribution of high-quality reservoir areas predicted by both methods is generally similar, but many subtle differences remain.

[0064] (1) Curvature prediction of reservoirs is more precise, and many details are reflected;

[0065] (2) The reservoirs within small-scale bioherms are shown by curvature properties, but cannot be shown by inversion methods.

[0066] Figure 7 The newly drilled X16 well in the work area encountered two bioherms in the horizontal section. The bioherm reservoir at target point A (No. 1) was thicker and had better physical properties than bioherm ② at target point B. However, the energy storage coefficient diagram obtained from the inversion results showed that bioherm ① was better than bioherm ②. The minimum negative curvature attribute showed that bioherm ① was smaller than bioherm ②, which means that the reservoir coefficient was larger. This is consistent with the actual drilling results, verifying the rationality and effectiveness of the invention. It can effectively guide the selection of the optimal target location in the work area and can be promoted and applied in other work areas to promote the efficient exploration and development of bioherm gas reservoirs.

[0067] Therefore, those skilled in the art should recognize that although the present invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0068] Furthermore, although the real-time operation of the invention is described in a specific order in the accompanying drawings, this is not intended to imply that the operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Certain steps may be omitted, multiple steps may be combined into one step, or one step may be divided into multiple steps.

[0069] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for predicting bioherm reservoirs based on the minimum negative curvature attribute along seismic layers, characterized in that, The method includes: Establish a geological model of the bioherm reservoir and underlying strata; Based on the established geological model, forward modeling is performed, and the minimum negative curvature attribute is extracted along the underlying strata based on the forward modeling results. By extracting the minimum negative curvature attribute along the underlying strata and comparing it with reservoir development in various models, a correspondence between the minimum negative curvature attribute and bioherm reservoir development was established; among them, The establishment of the geological model of the bioherm reservoir and underlying strata includes: Determine the development pattern of bioherm reservoirs and the morphology of underlying strata; Based on the development pattern of bioherm reservoirs and the morphology of underlying strata, a geological model of bioherm reservoirs and underlying stable strata is established. The process of performing forward modeling based on the established geological model, and extracting the minimum negative curvature attribute along the underlying strata based on the forward modeling results, includes: Based on the geological model, elastic wave forward modeling was performed, and pre-stack depth migration was performed to obtain the forward modeling profile. Stratigraphic tracking is performed on the underlying strata on the pre-stack time-migrated seismic data volume obtained by forward modeling, and the minimum negative curvature attribute is extracted along the underlying strata. The correspondence includes: When the reservoir width is stable, the greater the reservoir thickness, the smaller the minimum negative curvature of the underlying strata. When the reservoir width is stable, better physical properties correspond to a larger minimum negative curvature of the underlying strata.

2. The bioherm reservoir prediction method based on seismic minimum negative curvature attribute according to claim 1, characterized in that, The process of performing elastic wave forward modeling based on the geological model and performing pre-stack depth migration to obtain the forward modeled profile also includes: Based on the undulations of the underlying strata in the reservoir development area of ​​the study area, an identification model for the undulations of the underlying strata in bioherm reservoirs was established.

3. The bioherm reservoir prediction method based on the minimum negative curvature attribute along the seismic layer as described in claim 1, characterized in that, The method of performing stratigraphic tracking of the underlying strata on the pre-stack time-migrated seismic data volume obtained by forward modeling, and extracting the minimum negative curvature attribute along the underlying strata stratigraphic horizon, also includes... Based on forward modeling and pre-stack time migration studies, the seismic response characteristics of bioherm reservoirs with different thicknesses, widths, distances from the bottom, and physical properties, as well as the underlying strata, were obtained.

4. The bioherm reservoir prediction method based on seismic minimum negative curvature attribute according to claim 1, characterized in that, The correspondence also includes: With the reservoir width, thickness, and physical properties remaining constant, except for the negative curvature anomaly caused by interference due to the reservoir being too close to the underlying strata, the rest are characterized by changes in distance from the bottom and will not cause changes in the negative curvature of the underlying strata. With the reservoir thickness and physical properties remaining constant, as the reservoir width increases, the minimum negative curvature of the underlying strata first decreases and then increases. When the reservoir width is 130m~170m, the minimum negative curvature of the underlying strata becomes bimodal and remains stable as the reservoir width gradually increases.

5. The bioherm reservoir prediction method based on seismic minimum negative curvature attribute according to claim 1, characterized in that, The method further includes: The correlation between the minimum negative curvature attribute and the development of bioherm reservoirs was verified by drilling new wells in the work area.

6. The bioherm reservoir prediction method based on seismic minimum negative curvature attribute according to claim 5, characterized in that, The method also includes using curvature attribute planar maps and the corresponding relationships to predict bioherm reservoirs and select optimal target sites.

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