A method for predicting seismic formation pressure based on the Y-PPM pore physics model

Abstract

The present invention discloses a seismic formation pressure prediction method based on the Y-PPM pore physics model, which is applicable to the field of petroleum geophysical exploration. The method comprises: first, inverting seismic data from the target area to obtain velocity and density data, and then accurately determining the overburden pressure based on the density data. The Eaton formula and the Fillippone formula are then combined to establish a normal compaction trend formation velocity substitution model. A first correlation model between formation velocity and effective pressure is then established based on the Y-PPM pore physics model, and a second correlation model between effective pressure and formation pressure is established based on effective stress theory. Finally, a high-precision model between formation velocity and formation pressure is established based on the substitution model, the first correlation model, and the second correlation model.

Description

Technical Field

[0001] The present invention belongs to the field of petroleum geophysical exploration, and in particular relates to a formation pressure prediction technology. Background Art

[0002] Formation pressure prediction is crucial for drilling engineers to prevent drilling disasters. Formation pressure prediction typically relies on traditional estimation methods, including the Eaton method and the Fillippone method. However, studies of these traditional methods have revealed the following common shortcomings:

[0003] (1) Generally speaking, a normal compaction trend formation velocity curve must be established before predicting pressure. However, the accuracy of this curve depends on the richness of the acoustic time difference data. Since there is a lack of relevant data in the new area, it is difficult to obtain an accurate normal compaction trend formation velocity curve in the new area. In addition, the establishment of this curve is also affected by the subjectivity of the engineer. It requires the engineer to have sufficient understanding of the target work area in order to fit an accurate normal compaction trend formation velocity curve and obtain a reasonable formation pressure prediction result.

[0004] (2) The applicability of these formation pressure prediction methods is poor. For example: 1. The Fillippone method based on basin modeling is widely used in China. It has the advantages of not needing to establish normal compaction trend formation velocity and being able to quickly calculate pore pressure. However, it has a fatal flaw: since the Fillippone equation is a difference quotient combination relationship, it will no longer be applicable when the formation velocity is reversed. Summary of the Invention

[0005] The present invention proposes a seismic formation pressure prediction method based on the Y-PPM pore physical model, which solves the problems of poor applicability and strict application conditions of existing formation pressure prediction methods.

[0006] The technical solution adopted by the present invention is: a method for predicting seismic formation pressure based on the Y-PPM pore physical model, comprising:

[0007] S1. Based on the inversion of seismic data in the target area, the velocity and density are obtained, and the overburden pressure P is further calculated. overburden and hydrostatic pressure P water , the Eaton formula and Fillippone formula are combined to establish a normal compaction trend formation velocity substitution model;

[0008] S2. Establishing a first correlation model between formation velocity and effective pressure based on the Y-PPM pore physics model, and determining a second correlation model between effective pressure and formation pressure based on the effective stress theory;

[0009] S3. Determine the formation pressure of the target area based on the normal compaction trend formation velocity model of S1, the first correlation model and the second correlation model of S2.

[0010] Furthermore, step S1 specifically includes the following steps:

[0011] S11. Invert the seismic reflection coefficient using seismic data. The objective function is as follows:

[0012]

[0013] Where I represents seismic wave impedance, G is the wavelet matrix, d is the seismic data, and ||·|| represents the two-norm;

[0014] S12, based on the well logging data constraints, using the wave impedance data in step S11 to invert the velocity V and density ρ;

[0015] S13. Based on the relationship between hydrostatic pressure and seawater density, the following relationship is obtained:

[0016] P water =ρ water gh water

[0017] Where: P water is the hydrostatic pressure; ρ water is the density of seawater; g is the acceleration due to gravity; h is the acceleration due to gravity water is the water injection height;

[0018] S14. Using the inverted formation density ρ and the overburden pressure calculation formula, the accurate overburden pressure is obtained:

[0019]

[0020] Where: P overburden is the overburden pressure; h water is the depth of seawater, h is the depth of overlying rock layers;

[0021] S15. Combine the Eaton formula and the Fillippone formula to establish a normal compaction trend formation velocity substitution model.

[0022] Furthermore, step S15 of establishing a normal compaction trend formation velocity substitution model specifically includes the following steps:

[0023] A1. According to Eaton's method, the expression is as follows:

[0024]

[0025] Where: P Eaton is the Eaton formation pressure, V normalis the formation velocity in normal compaction trend, n is the Eaton index;

[0026] A2. According to Fillippone's method, the expression is as follows:

[0027]

[0028] Where: P Fillippone is the Fillippone formation pressure, V max 、V min is the extreme value of formation velocity;

[0029] A3. When the stratum is in normal compaction condition:

[0030] V=V normal , P Eaton =P Fillippone =P water

[0031] A4. Based on the expressions in steps A1, A2, and A3, solve for the formation velocity in the normal compaction trend. The expression is as follows:

[0032]

[0033] Where: V normal It is the formation velocity with normal compaction trend.

[0034] Furthermore, step S2 includes the following sub-steps:

[0035] S21. Establishing a first correlation model between formation velocity and effective pressure based on the Y-PPM pore physics model;

[0036] S22. Based on the effective stress theory, a second correlation model between effective pressure and formation pressure is established.

[0037] Furthermore, step S21 of establishing the first association model includes the following sub-steps:

[0038] B1. According to the Y-PPM pore physical model, the expression is as follows:

[0039] V=V normal +c(e -1 -e -k )

[0040] Where: k = P d / P dn , P d is the effective pressure, P dn is the effective pressure under normal compaction conditions, c is the regression coefficient;

[0041] B2. Using the Y-PPM pore physical model from step B1, establish a first correlation model between formation velocity and effective pressure:

[0042]

[0043] Furthermore, step S22 of establishing the second association model includes the following sub-steps:

[0044] C1. According to the effective stress theory, the following expression is obtained:

[0045] P d =P overburden -P P

[0046] Where: P P Refers to the vertical effective pressure of mudstone particles;

[0047] C2. Further determine the effective pressure under normal compaction conditions based on the effective stress theory. The expression is:

[0048] P dn =P overburden -P water

[0049] Where: k = P d / P dn ;

[0050] C3. Further establish a second correlation model between effective pressure and formation pressure according to steps C1 and C2:

[0051]

[0052] Furthermore, step S3 of calculating the formation pressure includes the following sub-steps:

[0053] S31. Based on the first correlation model of step B2 and the second correlation model of step C3, a high-precision model of formation pressure and formation velocity is obtained, which is expressed as:

[0054]

[0055] S32. Combined with the normal compaction trend formation velocity substitution model of step S15, the inverted formation velocity data, overburden pressure, and hydrostatic pressure are imported into the formation pressure model of step S31 to calculate the formation pressure.

[0056] Beneficial effects of the present invention:

[0057] This invention proposes a replacement model for normal compaction trend formation velocities, replacing manual fitting of normal compaction trend formation velocities. This avoids the inability to establish an accurate pressure prediction model due to a lack of acoustic transit time data during formation pressure prediction. Based on this, the invention utilizes the Y-PPM pore physics model to develop a formation pressure prediction technology. This technology reduces the parameter requirements during drilling operations and improves the efficiency of oil and gas exploration and drilling operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a flow chart of the solution of the present invention;

[0059] Figure 2 Provides an inverted formation velocity and density profile 1 for an embodiment of the present invention;

[0060] Figure 3 A first alternative model for the normal compaction trend formation velocity provided by an embodiment of the present invention;

[0061] Figure 4 The first formation pressure prediction profile provided by the embodiment of the present invention;

[0062] Figure 5 Provides a second inverted formation velocity and density profile for the embodiment of the present invention;

[0063] Figure 6 The second normal compaction trend formation velocity substitution model provided by the embodiment of the present invention;

[0064] Figure 7 The second formation pressure prediction profile provided by the embodiment of the present invention; DETAILED DESCRIPTION

[0065] To facilitate those skilled in the art to understand the content of the present invention, the following technical aspects are now explained:

[0066] Y-PPM pore physical model

[0067] The Y-PPM pore physics model, proposed by Yan, is a novel pore physics model based on laboratory core stress effect measurements. This model utilizes differential pressure and effective pressure to improve the accuracy of pore pressure prediction. While studying Han's data, Yan discovered that when the differential pressure is not too high (e.g., less than 60 MPa), the following velocity model is sufficient to describe the effect of stress on velocity:

[0068]

[0069] Where V is the formation velocity, V pa, c are the two fitting parameters of the model, and the exponential relationship and power relationship are used to fit the laboratory measurement data. In order to make formula (1) clearer, the symbols in formula (1) are rearranged to construct the following equation:

[0070]

[0071] The V pa Set as:

[0072] V pa =V normal +C·e -1 (3)

[0073] Therefore, formula (2) has a more intuitive form:

[0074] V=V normal +c(e -1 -e -k ) (4)

[0075] Where k = P d / P dn , V normal is the normal compaction trend formation velocity; Formula (4) is the specific functional form of the Y-PPM pore physics model. Compared with the single power relationship used in the Eaton method, the Y-PPM pore physics model uses an exponential velocity-stress relationship to better describe the effect of stress on velocity. However, the Y-PPM pore physics model also relies on artificially synthesized normal compaction trend formation velocity. When some acoustic time difference curves are missing, it cannot accurately predict the formation pressure. Moreover, the model indirectly predicts the pore pressure through the relationship between the formation velocity and the effective pressure. It cannot be used to directly calculate the formation pressure, making it difficult to apply in actual work areas.

[0076] Therefore, the present invention establishes a seismic formation pressure prediction method based on the Y-PPM pore physics model by constructing a normal compaction trend formation velocity substitution model and two correlation models, which can be widely used in the field of oil exploration and development. Figure 2 and Figure 5 These are two sets of velocity and density profiles obtained by inversion in a certain sea basin area in China. Figure 3 and Figure 6 The velocity substitution model for the normal compaction trend is: Figure 4 and Figure 7 The image shows that the pressure profile predicted by the present invention increases with increasing depth in the vertical direction. The predicted formation pressure change trend is consistent with the change trend of velocity and density, showing good vertical continuity and horizontal layer consistency. The geological profile reflected is clear and the layers are distinct, with good visualization effect, which can be used to guide exploration and development work.

[0077] Those skilled in the art will appreciate that the embodiments described herein are intended to aid the reader in understanding the principles of the present invention, and it should be understood that the scope of the present invention is not limited to such specific descriptions and embodiments. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A method for predicting seismic formation pressure based on the Y-PPM pore physics model, characterized in that: include: S1. Based on the inversion of seismic data in the target area, the velocity and density are obtained, and the overburden pressure P is further calculated. overburden and hydrostatic pressure P water , the Eaton formula and Fillippone formula are combined to establish a normal compaction trend formation velocity substitution model; S2. Establishing a first correlation model between formation velocity and effective pressure based on the Y-PPM pore physics model, and determining a second correlation model between effective pressure and formation pressure based on the effective stress theory; S3. Determine the formation pressure of the target area based on the normal compaction trend formation velocity model of S1, the first correlation model and the second correlation model of S2.

2. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 1, characterized in that: Step S1 specifically includes the following sub-steps: S11. Invert the seismic reflection coefficient using seismic data. The objective function is as follows: Where I represents seismic wave impedance, G is the wavelet matrix, d is the seismic data, and ||·|| represents the two-norm; S12, based on the well logging data constraints, using the wave impedance data in step S11 to invert the velocity V and density ρ; S13. Based on the relationship between hydrostatic pressure and seawater density, the following relationship is obtained: P water =ρ water gh water Where: P water is the hydrostatic pressure; ρ water is the density of seawater; g is the acceleration due to gravity; h is the acceleration due to gravity water is the water injection height; S14. Using the inverted formation density ρ and the overburden pressure calculation formula, the accurate overburden pressure is obtained: Where: P overburden is the overburden pressure; h water is the depth of seawater, h is the depth of overlying rock layers; S15. Combine the Eaton formula and the Fillippone formula to establish a normal compaction trend formation velocity substitution model.

3. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 2, characterized in that: Step S15 specifically includes the following sub-steps: A1. According to Eaton's method, the expression is as follows: Where: P Eaton is the Eaton formation pressure, V normal is the formation velocity in normal compaction trend, n is the Eaton index; A2. According to Fillippone's method, the expression is as follows: Where: P Fillippone is the Fillippone formation pressure, V max 、V min is the extreme value of formation velocity; A3. When the stratum is in normal compaction condition: V=V normal ,P Eaton =P Fillippone =P water A4. Based on the expressions in steps A1, A2, and A3, solve for the formation velocity in the normal compaction trend. The expression is as follows: Where: V normal It is the formation velocity with normal compaction trend.

4. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 3, characterized in that: Step S2 includes the following sub-steps: S21. Establishing a first correlation model between formation velocity and effective pressure based on the Y-PPM pore physics model; S22. Based on the effective stress theory, a second correlation model between effective pressure and formation pressure is established.

5. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 4, characterized in that: Step S21 includes the following sub-steps: B1. According to the Y-PPM pore physical model, the expression is as follows: V=V normal +c(e -1 -e -k ) Where: k = P d / P dn , P d is the effective pressure, P dn is the effective pressure under normal compaction conditions, c is the regression coefficient; B2. Using the Y-PPM pore physics model from step B1, establish a first correlation model between formation velocity and effective pressure:

6. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 5, characterized in that: Step S22 includes the following sub-steps: C1. According to the effective stress theory, the following expression is obtained: P d =P overburden -P P Where: P P Refers to the vertical effective pressure of mudstone particles; C2. Further determine the effective pressure under normal compaction conditions based on the effective stress theory. The expression is: P dn =P overburden -P water Where: k = P d / P dn ; C3. Further establish a second correlation model between effective pressure and formation pressure according to steps C1 and C2:

7. The method for predicting seismic formation pressure based on the Y-PPM pore physical model according to claim 6, characterized in that: Step S3 includes the following sub-steps: S31. Based on the first correlation model of step B2 and the second correlation model of step C3, a high-precision model of formation pressure and formation velocity is obtained, which is expressed as: S32. Combined with the normal compaction trend formation velocity substitution model of step S15, the inverted formation velocity data, overburden pressure, and hydrostatic pressure are imported into the formation pressure model of step S31 to calculate the formation pressure.

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