A petrophysical forward method and device for time-lapse seismic monitoring

Abstract

This specification discloses a forward modeling method and apparatus for rock physics in time-lapse seismic monitoring. This involves determining an initial value S of the target fluid's saturation. G and change value ΔS G According to the initial value S G and change value ΔS G Determine the longitudinal wave velocity V in the target fluid; calculate the compressibility modulus M of the rock saturated with the pure target fluid based on the initial and varying values. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Based on the compressibility modulus M of the rock saturated with the pure target fluid G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Calculate the compressibility modulus M of saturated rock after the target fluid saturation changes under high frequency conditions. ∞ Based on the compressibility modulus M of the saturated rock after the change in target fluid saturation under the aforementioned high-frequency conditions. ∞ The saturated rock compressibility modulus M after the target fluid saturation changes under the low-frequency conditions. F Calculate the attenuation model.

Description

Technical Field

[0001] This specification relates to the field of oil and gas geophysical engineering technology, and in particular to a forward modeling method and equipment for rock physics for time-shifted seismic monitoring. Background Technology

[0002] Time-lapse seismic monitoring is a seismic exploration technique used to dynamically monitor changes in underground reservoirs or fluids. Using rock physics theory, velocity and elastic modulus data obtained from time-lapse seismic monitoring are converted into fluid distribution data. However, before applying rock physics inversion methods for fluid identification, it is essential to fully understand the impact of fluid saturation on seismic wave velocity and elastic modulus; that is, to establish a quantitative relationship between velocity, elastic modulus, and saturation through rock physics forward modeling methods. Currently, the field lacks rock physics forward modeling methods specifically for time-lapse seismic monitoring, especially those that simultaneously consider P-wave velocity and attenuation.

[0003] Therefore, a simpler scheme for forward modeling in rock physics is needed. Summary of the Invention

[0004] This specification provides a forward modeling method and apparatus for rock physics in time-shifted seismic monitoring to address the following technical problem: the need for a simpler scheme for forward modeling in rock physics.

[0005] To solve the above-mentioned technical problems, one or more embodiments of this specification are implemented as follows:

[0006] In a first aspect, embodiments of this specification provide a forward modeling method for rock physics in time-lapse seismic monitoring, comprising:

[0007] Determine the initial value S of the saturation of the target fluid. G and change value ΔS G According to the initial value S G and change value ΔS G The longitudinal wave velocity V in the target fluid is determined as follows:

[0008]

[0009] Where V0 is the initial P-wave velocity obtained from baseline exploration, ρ0 is the saturated rock density before the target fluid saturation changes, M0 is the saturated rock compressibility modulus before the target fluid saturation changes, K0 is the mixed fluid bulk modulus before the target fluid saturation changes, and K... i Let S be the bulk modulus of the i-th fluid component in the pore fluid, excluding the target fluid. i K represents the saturation level of the corresponding i-th fluid component. G K represents the bulk modulus of the target fluid.F M is the bulk modulus of the mixed fluid after the target fluid saturation changes. F M represents the compressibility modulus of saturated rock after changes in the saturation of the target fluid under low-frequency conditions. S ρ is the compressive modulus of the rock matrix, φ is the porosity, and ρ is the density of the rock matrix. F ρ0 is the saturated rock density after the change in target fluid saturation, and ρ0 is the saturated rock density before the change in target fluid saturation. fl ρ is the density of the mixed fluid before the target fluid saturation changes. G The density of the target fluid;

[0010] Calculate the compressibility modulus M of the rock saturated with pure target pore fluid based on the initial and changing values. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W ;

[0011] Based on the compressibility modulus M of the rock saturated with the pure target fluid G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Calculate the compressibility modulus M of saturated rock after the target fluid saturation changes under high frequency conditions. ∞ ;

[0012] Based on the compressibility modulus M of the saturated rock after the change in target fluid saturation under the aforementioned high-frequency conditions. ∞ The saturated rock compressibility modulus M after the target fluid saturation changes under the low-frequency conditions. F Calculate the attenuation model.

[0013] In a second aspect, one or more embodiments of this specification provide an electronic device, comprising:

[0014] At least one processor; and,

[0015] A memory communicatively connected to the at least one processor; wherein,

[0016] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method as described in the first aspect.

[0017] The above-described at least one technical solution adopted in one or more embodiments of this specification can achieve the following beneficial effects: by determining the initial value S of the saturation of the target fluid... G and change value ΔS G According to the initial value S G and change value ΔS GDetermine the longitudinal wave velocity V in the target fluid; calculate the compressibility modulus M of the rock saturated with the pure target fluid based on the initial and varying values. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Based on the compressibility modulus M of the rock saturated with the pure target fluid G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Calculate the compressibility modulus M of saturated rock after the target fluid saturation changes under high frequency conditions. ∞ Based on the compressibility modulus M of the saturated rock after the change in target fluid saturation under the aforementioned high-frequency conditions. ∞ The saturated rock compressibility modulus M after the target fluid saturation changes under the low-frequency conditions. F The attenuation model is calculated, thus enabling the calculation of the longitudinal wave velocity and attenuation model in the target fluid based on observation data without estimating the elastic modulus of the rock skeleton, which is more convenient. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a process framework provided for an embodiment of this specification.

[0020] Figure 2 A schematic flowchart illustrating a rock physics forward modeling method for time-lapse seismic monitoring, provided as an embodiment of this specification;

[0021] Figure 3 A schematic diagram of the established initial velocity model;

[0022] Figure 4 A schematic diagram of the compressibility modulus of the rock matrix;

[0023] Figure 5 This is a schematic diagram of porosity φ;

[0024] Figure 6 This is a schematic diagram of density ρ;

[0025] Figure 7 A schematic diagram of supercritical carbon dioxide saturation;

[0026] Figure 8 A schematic diagram of the velocity model after carbon dioxide injection;

[0027] Figure 9 A schematic diagram of the decay model after carbon dioxide injection;

[0028] Figure 10 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this specification. Detailed Implementation

[0029] This specification provides a rock physics forward modeling method, apparatus, device, and storage medium for time-shifted seismic monitoring.

[0030] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0031] The theoretical basis of this application is as follows:

[0032] In time-lapse seismic monitoring, the compressibility modulus of saturated rock before the change of target fluid saturation is calculated using the velocity obtained from baseline exploration. The following equation is used to calculate the compressibility modulus of saturated rock before the change of target fluid saturation:

[0033]

[0034] Where V0 is the P-wave velocity obtained from baseline exploration, ρ0 is the density, and M0 is the compressibility modulus of saturated rock before the target fluid saturation changes.

[0035] The bulk modulus of the mixture before the change in the target fluid saturation is then calculated using the following equation:

[0036]

[0037] Where K0 is the bulk modulus of the mixed fluid before the change in the target fluid saturation, K i It is the bulk modulus of the fluid component. S i It is the saturation of the fluid component.

[0038] Calculate the bulk modulus of the mixed fluid by inputting the change in the saturation of the target fluid. The following equation is used to calculate the bulk modulus of the mixed fluid after the change in the saturation of the target fluid:

[0039]

[0040] K G It is the bulk modulus of the target fluid, SG It is the change in the target fluid saturation.

[0041] Given the bulk modulus of the mixed fluid after a change in target fluid saturation, calculate the compressive modulus of the saturated rock after the change in target fluid saturation. The compressive modulus of the saturated rock after the change in target fluid saturation is calculated using the following equation:

[0042]

[0043] Among them, M S These are the rock matrix compressibility moduli, M0 and M F These are the compressibility moduli of saturated rock before and after the change in target fluid saturation, K0 and K, respectively. F These are the bulk modulus of the mixed fluid before and after the change in target fluid saturation, respectively. φ is porosity.

[0044] Input the changing saturation of the target fluid and calculate the saturated rock density. The following equation is used to calculate the saturated rock density after the change in target fluid saturation:

[0045] ρ F =ρ0-φS G ρ fl +φS G ρ G

[0046] Where ρ0 and ρ F These are the saturated rock densities before and after the change in target fluid saturation, ρ. fl ρ is the density of the mixed fluid before the target fluid saturation changes. G It is the density of the target fluid.

[0047] The P-wave velocity after the target fluid saturation changes is calculated using the following equation:

[0048]

[0049] Where V is the longitudinal wave velocity after the target fluid saturation changes, and ρ F M is the density after the target fluid saturation changes. F It is the compressibility modulus of saturated rock after the target fluid saturation changes.

[0050] In summary, the bulk modulus of the mixed fluid can be calculated by inputting the change in the target fluid saturation, and the compressive modulus of the saturated rock before the change in target fluid saturation can be calculated based on the P-wave velocity obtained from baseline exploration. Then, by inputting the bulk modulus of the mixed fluid and the compressive modulus of the saturated rock, the compressive modulus of the saturated rock after the change in target fluid saturation is calculated. Finally, by inputting the compressive modulus of the saturated rock, the P-wave velocity of the saturated rock after the change in target fluid saturation is calculated. Figure 1 As shown, Figure 1 This is a schematic diagram of a process framework provided for an embodiment of this specification.

[0051] Figure 2 This is a flowchart illustrating a rock physics forward modeling method for time-shifted seismic monitoring, provided as an embodiment of this specification.

[0052] Figure 2 The process may include the following steps:

[0053] S201: Determine the initial value S of the target fluid's saturation. G and change value ΔS G .

[0054] S202, according to the initial value S G and change value ΔS G The longitudinal wave velocity in the target fluid is determined as follows:

[0055]

[0056] Where V0 is the initial P-wave velocity obtained from baseline exploration, ρ0 is the saturated rock density before the target fluid saturation changes, M0 is the saturated rock compressibility modulus before the target fluid saturation changes, K0 is the mixed fluid bulk modulus before the target fluid saturation changes, and K... i Let S be the bulk modulus of the i-th fluid component in the pore fluid, excluding the target fluid. i K represents the saturation level of the corresponding i-th fluid component. G K represents the bulk modulus of the target fluid. F M is the bulk modulus of the mixed fluid after the target fluid saturation changes. F M represents the compressibility modulus of saturated rock after changes in the saturation of the target fluid under low-frequency conditions. S ρ is the compressive modulus of the rock matrix, φ is the porosity, and ρ is the density of the rock matrix. F ρ0 is the saturated rock density after the change in target fluid saturation, and ρ0 is the saturated rock density before the change in target fluid saturation. fl ρ is the density of the mixed fluid before the target fluid saturation changes. G The density of the target fluid;

[0057] S203, calculate the compressibility modulus M of the rock saturated with pure target fluid based on the initial and changed values. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W .

[0058] Specifically, M can be calculated in the following way. G and M W :

[0059]

[0060] S204, based on the compressibility modulus M of the rock saturated with the pure target fluid. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Calculate the compressibility modulus M of saturated rock after the target fluid saturation changes under high frequency conditions. ∞ .

[0061] M is calculated in the following way ∞ :

[0062] S205, based on the compressibility modulus M of the saturated rock after the change in the saturation of the target fluid under the high-frequency condition. ∞ The saturated rock compressibility modulus M after the target fluid saturation changes under the low-frequency conditions. F Calculate the attenuation model

[0063] In other words, the longitudinal wave velocity V can be calculated directly as follows:

[0064]

[0065] The attenuation model can be calculated using the following set of equations:

[0066]

[0067] By determining the initial value S of the saturation of the target fluid. G and change value ΔS G According to the initial value S G and change value ΔS G Determine the longitudinal wave velocity V in the target fluid; calculate the compressibility modulus M of the rock saturated with the pure target fluid based on the initial and varying values. G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Based on the compressibility modulus M of the rock saturated with the pure target fluid G The saturated rock compressibility modulus M when the pore fluid does not contain the target fluid W Calculate the compressibility modulus M of saturated rock after the target fluid saturation changes under high frequency conditions. ∞ Based on the compressibility modulus M of the saturated rock after the change in target fluid saturation under the aforementioned high-frequency conditions. ∞ The saturated rock compressibility modulus M after the target fluid saturation changes under the low-frequency conditions. FThe attenuation model is calculated, thus enabling the calculation of the longitudinal wave velocity and attenuation model in the target fluid based on observation data without estimating the elastic modulus of the rock skeleton, which is more convenient.

[0068] Compared with existing technologies, this invention provides a rock physics forward modeling method for time-lapse seismic exploration technology. It calculates the in-situ saturated rock compressive modulus using velocity data obtained from baseline exploration, and finally derives the attenuation using an attenuation formula. This invention can directly establish the relationship between velocity, attenuation, and saturation, bypassing the estimation of the rock skeleton compressive modulus, and more easily obtains forward simulation results with higher determinism.

[0069] To illustrate the method of the present invention in more detail, the application effect of the present invention in fluid simulation results is given.

[0070] The formation is set as a saline aquifer, the initial pore fluid is saline water, the target fluid is supercritical carbon dioxide, and the initial saturation of supercritical carbon dioxide is 0. Figure 3 To establish the initial velocity model, set the corresponding rock matrix compression modulus (e.g., ...). Figure 4 As shown), porosity φ (as shown) Figure 5 (as shown) and density ρ (as shown) Figure 6 (As shown) and other stratigraphic parameters.

[0071] Based on the aforementioned parameters, a fluid simulation of supercritical carbon dioxide injection was performed, and the supercritical carbon dioxide saturation (e.g.) was obtained. Figure 7 As shown). Through forward modeling using rock physics, the velocity model after carbon dioxide injection is obtained by inputting saturation, rock physics parameters, and an initial velocity model. Figure 8 (as shown) and attenuation model (as shown) Figure 9 (As shown). The velocity and decay models, which are the results of the forward modeling, reflect the distribution range of carbon dioxide.

[0072] In summary, the rock physics forward modeling method proposed in this invention for time-lapse seismic monitoring technology establishes the relationship between fluid saturation, P-wave velocity, and attenuation. This method fully utilizes the advantages of time-lapse seismic monitoring, avoids estimating the rock skeleton's compressibility modulus, thereby reducing the difficulty and uncertainty of forward modeling and laying a theoretical foundation for subsequent fluid identification using P-wave velocity and attenuation.

[0073] In the second aspect, such as Figure 10 As shown, Figure 10 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this specification. The device includes:

[0074] At least one processor; and,

[0075] A memory communicatively connected to the at least one processor; wherein,

[0076] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method as described in the first aspect.

[0077] Based on the same idea, embodiments of this specification also provide a non-volatile computer storage medium corresponding to the above method, which stores computer-executable instructions. When a computer reads the computer-executable instructions from the storage medium, the instructions cause one or more processors to execute the method as described in the first aspect.

[0078] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the embodiments of apparatus, devices, and non-volatile computer storage media are basically similar to the method embodiments, so the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0079] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0080] The above description is merely one or more embodiments of this specification and is not intended to limit this specification. Various modifications and variations can be made to the one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of this specification.

Claims

1. A petrophysical forward method for time-lapse seismic monitoring, comprising: determining an initial value S of the saturation of the target fluid G and a change value AS G ; According to the initial value S G and the change value ΔS G The longitudinal wave velocity V in the target fluid is determined in the following manner: wherein V0 is the initial P-wave velocity obtained from baseline survey, p0 is the saturated rock density before the change of target fluid saturation, M0 is the saturated rock compressive modulus before the change of target fluid saturation, K0 is the bulk modulus of mixed fluid before the change of target fluid saturation, K i is the bulk modulus of the i-th fluid component in the pore fluid except the target fluid, S i is the saturation of the corresponding i-th fluid component, K G is the bulk modulus of the target fluid, K F is the bulk modulus of mixed fluid after the change of target fluid saturation, M F is the saturated rock compressive modulus after the change of target fluid saturation under low frequency condition, M S is the rock matrix compressive modulus, φ is the porosity, p F is the saturated rock density after the change of target fluid saturation, p0 is the saturated rock density before the change of target fluid saturation, p fl is the density of mixed fluid before the change of target fluid saturation, p G is the density of the target fluid; calculating a compressibility modulus M of the rock saturated with the pure target fluid of the pore fluid from the initial value and the change value G and the compressibility modulus M of the rock saturated when the pore fluid is free of the target fluid W ; the compressive modulus M of the rock saturated with the pure target fluid G and the compressive modulus M of the rock saturated with the pure target fluid W the compressive modulus M of the rock saturated with the pure target fluid ∞ ; a compressive modulus M of the saturated rock after a change in saturation of the target fluid under the high frequency condition ∞ a compressive modulus M of the saturated rock after a change in saturation of the target fluid under the low frequency condition F calculating an attenuation model 2. The method of claim 1, wherein, calculating a compressibility modulus M of the rock saturated with the pure target fluid of the pore fluid based on the initial value and the change value G and a compressibility modulus M of the rock saturated with the pore fluid not containing the target fluid W comprising: M is calculated in the following way G and M W :

3. The method of claim 1, wherein, the compressive modulus M of the rock saturated with the pure target fluid G and the compressive modulus M of the rock saturated with the pure target fluid W the compressive modulus M of the rock saturated with the pure target fluid ∞ , comprising: M is calculated in the following way ∞ :

4. An electronic device, comprising: at least one processor; and, a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method of any one of claims 1 to 3.

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