Carbon dioxide storage area safety seismic and geological combined evaluation method

Abstract

The application provides a carbon dioxide storage area safety geologic earthquake combined evaluation method, and the evaluation method comprises the following steps: S1, obtaining an isobath structure map based on three-dimensional seismic data and storage area drilling data; S2, obtaining a two-dimensional seismic profile according to the isobath structure map and interpreting the two-dimensional seismic profile as a two-dimensional geological profile; S3, obtaining overlying rock density ρ according to fault nearby well density logging data; S4, obtaining geological parameters according to the two-dimensional geological profile and calculating cross-section normal stress P; S5, obtaining fault zone argillan content S according to surrounding drilling data; S6, obtaining the formation pressure P1 of the target layer after gas injection according to the gas injection well; S7, obtaining a storage area safety index A according to the cross-section normal stress P and the formation pressure P1, and judging the safety of the storage area according to the safety index. The application provides an effective way for carbon dioxide storage area safety evaluation and provides a reference for carbon dioxide storage area oil and gas exploration and development.

Description

Technical Field

[0001] This invention relates to the fields of structural geology and petroleum geology, and in particular to a method for joint seismic and geological evaluation of the safety of carbon dioxide storage areas. Background Technology

[0002] Carbon dioxide enhanced oil recovery (CEM) and its sequestration (SOR) is an emerging technology for the utilization and management of carbon dioxide. Using carbon dioxide as an effective oil displacement agent not only improves oilfield recovery and generates economic benefits but also achieves permanent carbon dioxide sequestration, mitigating environmental pollution. However, safety risks still exist during CEM, and leaks can affect normal oilfield production and the natural environment. The safe implementation of CEM projects mainly depends on the geological conditions of the oil and gas reservoir, namely the sealing capacity of faults and caprocks. Current research on the impact of fault sealing on CEM storage remains insufficient, neglecting its control and influence on the oil and gas development process. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide a joint seismic and geological evaluation method for the safety of carbon dioxide storage areas that overcomes or at least partially solves the above problems.

[0004] According to one aspect of the present invention, a combined seismic and geological evaluation method for the safety of carbon dioxide storage areas is provided, the evaluation method comprising:

[0005] Step S1: Based on 3D seismic data and well data from the sealed area, obtain an isobath structural map;

[0006] Step S2: Obtain a two-dimensional seismic profile based on the isobath structural map and interpret it as a two-dimensional geological profile;

[0007] Step S3: Obtain the density ρ of the overlying rock based on the density logging data of wells near the fault;

[0008] Step S4: Obtain geological parameters based on the two-dimensional geological profile and calculate the cross-sectional normal compressive stress P;

[0009] Step S5: Determine the clay content S of the fracture zone based on surrounding drilling data;

[0010] Step S6: Obtain the formation pressure P1 after gas injection in the target formation based on the gas injection well;

[0011] Step S7: Calculate the safety index A of the sealing area based on the cross-sectional positive pressure stress P and the formation pressure P1, and determine the safety of the sealing area based on the safety index.

[0012] Optionally, the geological parameters include: the dip angle α of the sealing fault, the vertical fault displacement h, and the burial depth H of the target layer.

[0013] Optionally, step S1: obtaining an isobath structural map based on 3D seismic data and well data from the sealed area specifically includes:

[0014] Based on 3D seismic data and well data from the carbon dioxide storage area, seismic interpretation of the target strata in the carbon dioxide storage area was carried out to obtain isochronous maps of the storage area. Based on the velocity volume of the storage area, time-depth conversion was performed to obtain isodepth structural maps.

[0015] Optionally, the step of conducting seismic interpretation of the target strata in the carbon dioxide storage area based on 3D seismic data and well data of the storage area, obtaining isochronous maps of the storage area, and performing time-depth conversion based on the velocity volume of the storage area to obtain isodepth structural maps specifically includes:

[0016] Based on 3D seismic data and well data from the carbon dioxide storage area, we conducted seismic interpretation of the target stratigraphy in the carbon dioxide storage area and obtained the T0 map of the target stratigraphy.

[0017] Using the superimposed velocity spectrum, the velocity field of the target region is calculated according to the dix formula, and then the average velocity field of the target region is calculated.

[0018]

[0019] Among them, V int,i It is the layer velocity of the i-th layer, in m / s; V is the root mean square velocity of the i-th and i-1th layers. av T is the average velocity of the bottom surface of the nth layer, in m / s; i T i-1 It is the two-way time of the top surface of the i-th (i-1)th layer, in seconds;

[0020] The time-depth conversion of the T0 map of the target strata in the carbon dioxide storage area was performed using the mean velocity field to obtain an isobath structure map.

[0021] Optionally, step S2: obtaining a two-dimensional seismic profile based on the isobathographic map and interpreting it as a two-dimensional geological profile specifically includes:

[0022] Based on the isobathographic structural map, the distribution map of the fault system in the target layer is obtained. According to the fault strike, a two-dimensional seismic profile is obtained by selecting the direction perpendicular to the fault strike, and then interpreted as a two-dimensional geological profile.

[0023] Optionally, step S3: obtaining the overlying rock density ρ based on well density logging data near the fault specifically includes:

[0024] Using density logging data from carbon dioxide storage areas, a linear regression model was fitted to fit the overlying strata density ρ as a function of depth H: ρ = f(H), with a correlation coefficient R. 2 Greater than or equal to 0.8;

[0025] Based on the model, the density ρ of the overlying rock at the corresponding depth of the target strata in the carbon dioxide sequestration area of ​​the two-dimensional geological profile is calculated, in kg / m³. 3 .

[0026] Optionally, step S4: obtaining geological parameters based on the two-dimensional geological profile and calculating the cross-sectional normal compressive stress P specifically includes:

[0027] Based on the two-dimensional geological profile, determine the dip angle α (in degrees) of the target stratum sealing fault in the sealing area and the burial depth H (in meters), and calculate the compressive stress P of the cross-section.

[0028] P=(ρ-ρ w )gHcosα

[0029] In the formula ρ w Density of formation water, unit: kg / m³ 3 .

[0030] Optionally, step S5: determining the clay content S of the fracture zone based on surrounding drilling data specifically includes:

[0031] Determine the percentage of clay content in the target stratigraphic fault zone of the sealed area.

[0032]

[0033] Among them, the i-th layer S of the fault zone i The percentage of formation clay content is obtained from well logging data; ΔZ i is the thickness of the i-th layer of the fault zone, in meters; h is the vertical fault displacement, in meters.

[0034] Optionally, step S6: obtaining the formation pressure P1 after gas injection into the target layer from the injection well specifically includes:

[0035]

[0036] Where θ is the wellbore inclination angle of the gas injection well, in °; g is the acceleration due to gravity, in 9.8 m / s²; v is the gas injection velocity, in m / s; ρ is the gas injection density, in kg / m³; p is the gas injection pressure, in MPa; and D is the inner diameter of the gas injection pipe, in m.

[0037] Optionally, step S7: calculating the safety index A of the storage area based on the cross-sectional normal compressive stress P and the formation pressure P1, and judging the safety of the storage area based on the safety index, specifically includes:

[0038] Calculate the safety index A of the sealing area, A = ((P-P1) / P)*(h1 / h), where h1 is the vertical displacement of the target layer after steam injection from the steam injection well.

[0039] The security of the storage area is determined based on the security index. When A < 0.3, the security of the storage area is low; when 0.3 < A < 0.6, the security of the storage area is medium; and when A > 0.6, the security of the storage area is high.

[0040] This invention provides a combined seismic and geological evaluation method for the safety of carbon dioxide storage areas. The evaluation method includes: Step S1: Obtaining an isobathographic structural map based on 3D seismic data and well data of the storage area; Step S2: Obtaining a 2D seismic profile from the isobathographic structural map and interpreting it as a 2D geological profile; Step S3: Obtaining the overlying rock density ρ based on well density logging data near the fault; Step S4: Calculating geological parameters and the cross-sectional normal compressive stress P based on the 2D geological profile; Step S5: Calculating the mud content S of the fault zone based on surrounding well data; Step S6: Obtaining the formation pressure P1 after gas injection into the target layer based on the injection wells; Step S7: Calculating the storage area safety index A based on the cross-sectional normal compressive stress P and the formation pressure P1, and judging the safety of the storage area based on the safety index. This provides an effective approach for evaluating the safety of carbon dioxide storage areas and serves as a reference for oil and gas exploration and development in carbon dioxide storage areas.

[0041] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0043] Figure 1 A flowchart illustrating a joint seismic and geological evaluation method for the safety of carbon dioxide storage areas, provided in an embodiment of the present invention;

[0044] Figure 2 This is a distribution diagram of the target strata fracture system in the sealing area provided in Embodiment 1 of the present invention;

[0045] Figure 3 This is a two-dimensional seismic profile of the target strata in the sealed area according to Embodiment 1 of the present invention, showing the vertical fault strike.

[0046] Figure 4 This is a two-dimensional geological profile of the target stratigraphic region of the sealed area provided in Embodiment 1 of the present invention;

[0047] Figure 5 This is a schematic diagram of the calculation of the normal pressure of the target stratum section in the sealing area provided in Embodiment 1 of the present invention;

[0048] Figure 6 This is a scatter plot of the security index of the target stratum in the sealing area provided in Embodiment 1 of the present invention. Detailed Implementation

[0049] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0050] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0051] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0052] like Figure 1 As shown, the present invention provides a joint seismic and geological evaluation method for the safety of carbon dioxide storage areas, comprising:

[0053] Based on 3D seismic data and well data of the carbon dioxide storage area, seismic interpretation of the target strata in the carbon dioxide storage area is carried out to obtain isochronous maps of the storage area. Based on the velocity volume of the storage area, time-depth conversion is performed to obtain isodepth structural maps.

[0054] Based on the iso-depth structural map, the distribution map of the fault system of the target layer is obtained. Based on the fault strike, the direction perpendicular to the fault strike is selected to obtain the two-dimensional seismic profile, which is then interpreted as a two-dimensional geological profile.

[0055] The density ρ of the overlying rock is obtained from the density logging data of wells near the fault.

[0056] Based on the two-dimensional geological profile, the dip angle α, vertical displacement h, and burial depth H of the target layer of the sealing fault are determined, and the cross-sectional compressive stress P is also determined.

[0057] The mud content S in the fault zone was determined based on surrounding drilling data.

[0058] The formation pressure P1 after steam injection in the target formation is obtained based on the steam injection well.

[0059] Calculate the security index A of the sealed area, and judge the security of the sealed area based on the security index.

[0060] Example 1

[0061] In a specific embodiment 1 of the present invention, the method for joint seismic and geological evaluation of the safety of carbon dioxide storage areas includes:

[0062] Step 1: Based on 3D seismic data and well data of the carbon dioxide storage area, conduct seismic interpretation of the target strata in the carbon dioxide storage area, obtain isochronous maps of the storage area, and perform time-depth conversion based on the velocity volume of the storage area to obtain isodepth structural maps.

[0063] Step 2: Obtain the fracture system distribution map of the target layer based on the iso-depth structural map.

[0064] Based on the fault strike, a two-dimensional seismic profile is obtained by selecting a direction perpendicular to the fault strike, and then interpreted as a two-dimensional geological profile.

[0065] Step 3: Obtain the density ρ of the overlying rock based on the density logging data of wells near the fault.

[0066] Step 4: Based on the two-dimensional geological profile, determine the dip angle α, vertical displacement h, and burial depth H of the sealing fault, and calculate the cross-sectional normal compressive stress P.

[0067] Step 5: Determine the mud content S in the fracture zone based on surrounding drilling data.

[0068] Step 6: Obtain the formation pressure P1 after steam injection in the target formation based on the steam injection well.

[0069] Step 7: Calculate the security index A of the sealed area, A = ((P-P1) / P)*(h1 / h). Determine the security of the sealed area based on the security index. When A < 0.3, the security of the sealed area is low; when 0.3 < A < 0.6, the security of the sealed area is medium; and when A > 0.6, the security of the sealed area is high.

[0070] Example 2

[0071] In a specific embodiment 2 of the present invention, such as Figure 1 As shown, Figure 1 This is a flowchart illustrating a joint seismic and geological evaluation method for the safety of carbon dioxide storage areas according to the present invention. The joint seismic and geological evaluation method for the safety of carbon dioxide storage areas includes:

[0072] In step 1, based on 3D seismic data and well data from the carbon dioxide storage area, seismic interpretation of the target stratigraphic sequence is performed to obtain the T0 map of the target stratigraphic sequence. Using the stacked velocity spectrum, the velocity field of the target area is calculated according to the dix formula, and then the average velocity field of the target area is calculated.

[0073]

[0074]

[0075] In the formula: V int,i It is the layer velocity of the i-th layer, in m / s; V is the root mean square velocity of the i-th and i-1th layers. av T is the average velocity of the bottom surface of the nth layer, in m / s; i T i-1 It is the two-way time of the top surface of the i-th and i-1-th layers, in seconds.

[0076] The time-depth conversion of the T0 map of the target strata in the carbon dioxide storage area was performed using the mean velocity field to obtain an isobath structure map.

[0077] In step 2, the distribution map of the fracture system of the target layer is obtained based on the iso-depth structural map. Based on the fault strike, a two-dimensional seismic profile is obtained by selecting the direction perpendicular to the fault strike and interpreting it as a two-dimensional geological profile.

[0078] In step 3, using density logging data from the carbon dioxide storage area, a linear regression model is used to fit the overlying strata density ρ as a function of depth H, ρ = f(H), and the correlation coefficient R is required. 2 Not less than 0.8. Based on this model, calculate the density ρ of the overlying rock at the corresponding depth of the target strata in the carbon dioxide sequestration area of ​​the two-dimensional geological profile, in kg / m³. 3 .

[0079] In step 4, the dip angle α of the target stratum sealing fault in the sealing area is determined based on the two-dimensional geological profile (unit: °), and the burial depth H of the target stratum (unit: m). The compressive stress P of the cross section is then calculated.

[0080] P=(ρ-ρ w )gHcosα

[0081] In the formula ρ w Density of formation water, unit: kg / m³ 3 .

[0082] In step 5, the percentage of clay content in the target stratigraphic fault zone of the sealed area is determined.

[0083]

[0084] In the formula, the i-th layer of the fault zone S i The percentage of formation clay content can be obtained from well logging data; ΔZ i is the thickness of the i-th layer of the fault zone, in meters; h is the vertical fault displacement, in meters.

[0085] In step 6, the formation pressure after gas injection into the target formation is obtained based on the gas injection well.

[0086]

[0087] In the formula, θ is the inclination angle of the gas injection wellbore, in degrees; g is the acceleration due to gravity, in 9.8 m / s².2 v is the injection gas velocity in m / s, and ρ is the injection gas density in kg / m³. 3 p is the injection pressure in MPa, and D is the inner diameter of the injection pipe in meters.

[0088] In step 7, the security index A of the sealing area is calculated, A = ((P-P1) / P)*(h1 / h). The security of the sealing area is judged based on the security index. When A < 0.3, the security of the sealing area is low; when 0.3 < A < 0.6, the security of the sealing area is medium; and when A > 0.6, the security of the sealing area is high.

[0089] Figure 2 In a specific embodiment of the present invention, seismic interpretation of the target strata in the carbon dioxide storage area is carried out based on three-dimensional seismic data and well data of the storage area, and the T0 map of the target strata in the storage area is obtained. Based on the velocity volume of the target strata in the storage area, time-depth conversion is performed to obtain the isodepth structural map of the target strata in the storage area. Based on the isodepth structural map of the target strata in the storage area, the distribution map of the fault system of the target layer is obtained.

[0090] Figure 3 In a specific embodiment of the present invention, the distribution map of the fracture system of the target layer is obtained based on the iso-depth structural map of the target strata in the sealed area, and a two-dimensional seismic profile is obtained by selecting the direction perpendicular to the fault strike based on the fault strike.

[0091] Figure 4 In a specific embodiment of the present invention, a two-dimensional geological profile is obtained based on the direction of the vertical fault strike to interpret the two-dimensional seismic profile of the target strata in the sealed area.

[0092] Figure 5 This is a schematic diagram illustrating the calculation of the normal pressure on the target stratum section of the sealing area in a specific embodiment of the present invention. The dip angle α of the sealing fault and the burial depth H of the target stratum are determined based on a two-dimensional geological profile, and the normal pressure stress P on the section is calculated, where P = ρgHcosα.

[0093] Figure 6 This is a scatter plot of the security index of the sealing area in a specific embodiment of the present invention.

[0094] The mud content S of the fracture zone was determined based on surrounding drilling data, where S = h1 / h. The formation pressure P1 after steam injection in the target layer was obtained from the steam injection well. The safety index A of the sealing zone was calculated by combining the positive pressure stress, where A = ((P-P1) / P)*(h1 / h). The safety of the sealing zone was judged based on the safety index. Specifically, when A < 0.3, the safety of the sealing zone is low; when 0.3 < A < 0.6, the safety of the sealing zone is moderate; and when A > 0.6, the safety of the sealing zone is high, as shown in Table 1.

[0095] Table 1. Positive compressive stress of different sealing faults

[0096]

[0097] Beneficial effects: The combined seismic and geological evaluation method for the safety of carbon dioxide storage areas provides an effective approach for safety evaluation of carbon dioxide storage areas and serves as a reference for oil and gas exploration and development in carbon dioxide storage areas.

[0098] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are 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 joint seismic and geological evaluation of the safety of carbon dioxide storage areas, characterized in that, The evaluation methods include: Step S1: Based on 3D seismic data and well data from the sealed area, obtain an isobath structural map; Step S2: Obtain a two-dimensional seismic profile based on the isobath structural map and interpret it as a two-dimensional geological profile; Step S3: Obtain the density ρ of the overlying rock based on the density logging data of wells near the fault; Step S4: Obtain geological parameters based on the two-dimensional geological profile and calculate the cross-sectional normal compressive stress P; Step S5: Determine the clay content S of the fracture zone based on surrounding drilling data; Step S6: Obtain the formation pressure P1 after gas injection in the target formation based on the gas injection well; Step S7: Calculate the safety index A of the sealing area based on the cross-sectional positive pressure stress P and the formation pressure P1, and determine the safety of the sealing area based on the safety index.

2. The method for joint seismic and geological evaluation of the safety of carbon dioxide storage areas according to claim 1, characterized in that, The geological parameters include: the dip angle α of the sealing fault, the vertical fault displacement h, and the burial depth H of the target layer.

3. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 1, characterized in that, Step S1: Obtaining the contour map based on 3D seismic data and well data from the sealed area specifically includes: Based on 3D seismic data and well data from the carbon dioxide storage area, seismic interpretation of the target strata in the carbon dioxide storage area was carried out to obtain isochronous maps of the storage area. Based on the velocity volume of the storage area, time-depth conversion was performed to obtain isodepth structural maps.

4. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 3, characterized in that, The process of seismic interpretation of the target strata in the carbon dioxide storage area based on 3D seismic data and well data of the storage area, obtaining isochronous maps of the storage area, and performing time-depth conversion based on the velocity volume of the storage area to obtain isodepth structural maps specifically includes: Based on 3D seismic data and well data from the carbon dioxide storage area, we conducted seismic interpretation of the target stratigraphy in the carbon dioxide storage area and obtained the T0 map of the target stratigraphy. Using the superimposed velocity spectrum, the velocity field of the target region is calculated according to the dix formula, and then the average velocity field of the target region is calculated. Among them, V int,i It is the layer velocity of the i-th layer, in m / s; V is the root mean square velocity of the i-th and i-1th layers. av T is the average velocity of the bottom surface of the nth layer, in m / s; i T i-1 It is the two-way time of the top surface of the i-th (i-1)th layer, in seconds; The time-depth conversion of the T0 map of the target strata in the carbon dioxide storage area was performed using the mean velocity field to obtain an isobath structure map.

5. The method for joint seismic and geological evaluation of the safety of carbon dioxide storage areas according to claim 1, characterized in that, Step S2: Obtaining a two-dimensional seismic profile based on the isobathographic structural map and interpreting it as a two-dimensional geological profile specifically includes: Based on the isobathographic structural map, the distribution map of the fault system in the target layer is obtained. According to the fault strike, a two-dimensional seismic profile is obtained by selecting the direction perpendicular to the fault strike, and then interpreted as a two-dimensional geological profile.

6. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 1, characterized in that, Step S3, obtaining the overlying rock density ρ based on well density logging data near the fault, specifically includes: Using density logging data from carbon dioxide storage areas, a linear regression model was fitted to fit the overlying strata density ρ as a function of depth H: ρ = f(H), with a correlation coefficient R. 2 Greater than or equal to 0.8; Based on the model, the density ρ of the overlying rock at the corresponding depth of the target strata in the carbon dioxide sequestration area of ​​the two-dimensional geological profile is calculated, in kg / m³. 3 .

7. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 1, characterized in that, Step S4: Obtaining geological parameters based on the two-dimensional geological profile and calculating the cross-sectional normal compressive stress P specifically includes: Based on the two-dimensional geological profile, determine the dip angle α (in degrees) of the target stratum sealing fault in the sealing area and the burial depth H (in meters), and calculate the compressive stress P of the cross-section. P=(ρ-ρ w )gHcosα In the formula ρ w Density of formation water, unit: kg / m³ 3 .

8. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 1, characterized in that, Step S5: Determining the clay content S of the fault zone based on surrounding drilling data specifically includes: Determine the percentage of clay content in the target stratigraphic fault zone of the sealed area. Among them, the i-th layer S of the fault zone i The percentage of formation clay content is obtained from well logging data; ΔZ i is the thickness of the i-th layer of the fault zone, in meters; h is the vertical fault displacement, in meters.

9. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 1, characterized in that, Step S6, obtaining the formation pressure P1 after gas injection into the target layer from the injection well, specifically includes: Where θ is the wellbore inclination angle of the gas injection well, in °; g is the acceleration due to gravity, in 9.8 m / s²; v is the gas injection velocity, in m / s; ρ is the gas injection density, in kg / m³; p is the gas injection pressure, in MPa; and D is the inner diameter of the gas injection pipe, in m.

10. The method for joint seismic and geological evaluation of the safety of a carbon dioxide storage area according to claim 2, characterized in that, Step S7: Calculating the safety index A of the storage area based on the cross-sectional compressive stress P and the formation pressure P1, and determining the safety of the storage area based on the safety index, specifically includes: Calculate the safety index A of the sealing area, A = ((P-P1) / P)*(h1 / h), where h1 is the vertical displacement of the target layer after steam injection from the steam injection well. The security of the storage area is determined based on the security index. When A < 0.3, the security of the storage area is low; when 0.3 < A < 0.6, the security of the storage area is medium; and when A > 0.6, the security of the storage area is high.

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