Formation pore pressure prediction method and device, electronic equipment and storage medium

Abstract

The invention provides a formation pore pressure prediction method and device, electronic equipment and a storage medium. The formation pore pressure prediction method based on interval transit time curve correction comprises the steps that hydrostatic pressure and overlying formation pressure of a whole well section of a single well are obtained based on logging data; constructing a normal stratum compaction trend line based on the interval transit time and the stratum burial depth; correcting the normal compaction trend line based on the relation between the transverse wave time difference and the longitudinal wave time difference; and predicting the single well pore pressure based on the obtained hydrostatic pressure, the overlying formation pressure and the corrected normal compaction trend line. According to the method, the transverse wave time difference and longitudinal wave time difference curve of the gas-free section is selected to establish the relation, the influence of the gas-bearing property of the formation is eliminated, and the precision of predicting the formation pressure through the Eaton method is improved.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas geophysical exploration, and relates to a method for reducing the influence of gas content on pore pressure prediction results, and specifically relates to a formation pore pressure prediction method, device, electronic equipment and storage medium based on acoustic wave time difference curve correction. Background Art

[0002] Pore ​​pressure prediction is an extremely important and complex issue in the development of oil and gas fields. Pore pressure prediction plays an important role in the development of oil and gas fields. It can guide pressure control in oil and gas production and ensure the safety and stability of the production process; help determine reasonable development plans and drilling designs to efficiently develop and utilize oil and gas resources, accurately evaluate the fluid properties and reservoir parameters in the formation, and improve the efficiency and benefits of oil and gas field development. Predicting the fluid flow trend in the formation helps to optimize the oil and gas production process and improve the recovery rate.

[0003] At present, there are two main methods for predicting pore pressure at home and abroad, namely graphical method and formula method. The graphical method mainly includes equivalent depth graphical method and ratio method. The formula method can be further divided into formula method that relies on normal compaction trend line and formula method that does not rely on normal compaction trend line. The former includes equivalent depth formula calculation method and Eaton method, and the latter includes Fillippone method and Martinez method. Among them, Eaton formula is a more commonly used pore pressure prediction method, but the normal compaction velocity needs to be obtained in the calculation process. The normal compaction velocity is generally obtained by fitting the longitudinal wave velocity of the shallow normal compaction formation. It is often difficult to obtain accurately when the shallow longitudinal wave time difference curve is missing or of poor quality.

[0004] The technology for obtaining formation pore pressure has long been a hot topic in the field of oil and gas exploration and development, especially in the field of oil and gas drilling. Although a variety of methods and technologies have been studied and applied, how to improve the accuracy of obtaining formation pressure remains the main technical difficulty. Summary of the invention

[0005] The accuracy of formation pore pressure is of great significance to oil and gas drilling projects. It is the basic parameter for scientifically designing casing procedures, and is also the key to reasonably selecting drilling fluid density and achieving near-balanced or under-balanced pressure drilling. It is related to the speed, safety and low cost of drilling, and sometimes even to the success or failure of drilling.

[0006] The present invention selects the shear wave time difference and the longitudinal wave time difference curve of the gas-free layer section to establish a relationship, and then applies it to the gas-bearing layer section to eliminate the influence of gas content, thereby improving the accuracy of predicting formation pressure by the Eaton method.

[0007] To achieve the above object, the present invention provides a formation pore pressure prediction method based on acoustic wave time difference curve correction, comprising:

[0008] Calculate the hydrostatic pressure and overlying formation pressure of the entire well section of a single well based on well logging data;

[0009] Construct the normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation;

[0010] Correcting the normal compaction trend line based on the relationship between the shear wave time difference and the longitudinal wave time difference;

[0011] The single well pore pressure is predicted based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

[0012] Furthermore, the expression of the hydrostatic pressure is:

[0013] P h =ρ w gh(1)

[0014] Among them, ρ w is the density of water, g is the acceleration due to gravity, and h is the depth of the formation.

[0015] Furthermore, the integral expression of the overlying formation pressure is as follows:

[0016]

[0017] in, is the formation porosity, ρ ma is the rock skeleton density, ρ f is the density of pore fluid, g is the acceleration of gravity, and h is the formation depth.

[0018] Furthermore, the following expression is used to interpolate the density data at equal intervals to obtain the gradient of the overburden pressure in the entire well section:

[0019]

[0020] Among them, G c is the pressure gradient of the overburden, ρ 0 and h 0 is the average density and thickness of the stratum without density, ρ bi is the scattered data of density, and Δh is the depth interval.

[0021] Furthermore, the normal compaction trend line of the formation constructed based on the acoustic time difference and the burial depth of the rock formation is expressed as:

[0022] ln(Δt)=a×H TVD +b(4)

[0023] Among them, Δt is the measured formation acoustic time difference, H TVD is the vertical depth, a and b are regression fitting coefficients, where b = ln(Δt0 ), Δt 0 It is the sound wave time difference in the shallow layer of the surface.

[0024] Further, the correction of the normal compaction trend line based on the relationship between the transverse wave time difference and the longitudinal wave time difference includes:

[0025] The longitudinal wave time difference and shear wave time difference curves are fitted for the selected mudstone section to determine the relationship between the two:

[0026] Δt DTC =a×Δt DTS +b(5)

[0027] Among them, Δt DTC is the measured longitudinal wave time difference, Δt DTS is the measured shear wave time difference, a and b are regression fitting coefficients;

[0028] Substitute the shear wave time difference into equation (5) again, fit a new acoustic wave time difference curve, and further repeat the calculation of a new normal compaction trend line based on the acoustic wave time difference and the burial depth of the rock formation.

[0029] Furthermore, the single well pore pressure is predicted based on the acquired hydrostatic pressure, overlying formation pressure and the corrected normal compaction trend line, and the calculation formula based on the Eaton method is:

[0030]

[0031] Among them, Δt n is the formation acoustic wave time difference obtained on the normal compaction trend line, Δt is the measured formation acoustic wave time difference, and p p is the formation pore pressure, p 0 is the overlying formation pressure, p f is the hydrostatic pressure and c is the Eaton index.

[0032] According to another aspect of the present invention, there is provided a formation pore pressure prediction device based on acoustic wave time difference curve correction, comprising:

[0033] The calculation module calculates the hydrostatic pressure of the entire well section and the overlying formation pressure of a single well based on the logging data;

[0034] A construction module is used to construct a normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation;

[0035] A correction module, which corrects the normal compaction trend line based on the relationship between the transverse wave time difference and the longitudinal wave time difference;

[0036] The prediction module predicts the single well pore pressure based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

[0037] According to another aspect of the present invention, there is provided an electronic device, the electronic device comprising:

[0038] A memory storing executable instructions;

[0039] A processor runs the executable instructions in the memory to implement the formation pore pressure prediction method based on acoustic wave time difference curve correction.

[0040] According to another aspect of the present invention, a non-transitory computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the method for predicting formation pore pressure based on acoustic wave time difference curve correction is implemented.

[0041] The method for predicting pore pressure in mudstone formations based on the correction of the acoustic time difference curve has the following characteristics: In shale and mudstone formations, the method relying on the normal compaction trend line has been well applied. In the selection of the normal compaction trend line, there are certain differences between the results selected according to experience and standards. At the same time, the acoustic time difference data of the normal compaction trend line comes from pure mudstone formations. When the sedimentation compaction reaches a certain level, the acoustic time difference curve remains almost unchanged, which makes it difficult to select the trend line. If the formation belongs to a non-continuous sedimentary formation and contains faults caused by tectonic movement, it will also affect the selection of the normal trend line. The present invention selects the shear wave time difference of the gas-free section to establish a relationship with the longitudinal wave time difference curve, eliminates the influence of the gas content of the formation, and improves the accuracy of the Eaton method in predicting formation pressure.

[0042] The present invention establishes a relationship between shear wave time difference and longitudinal wave time difference curves in shale formations, further eliminates the influence of gas content in gas-bearing layers, establishes a normal compaction trend line that is more in line with actual conditions, and improves the accuracy of pore pressure prediction by the Eaton method. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0044] Figure 1 The present invention is a flow chart of a formation pore pressure prediction method based on acoustic wave time difference curve correction.

[0045] Figure 2 The present invention is a flowchart of a method for predicting pore pressure in a mudstone formation based on correction of an acoustic wave time difference curve according to an embodiment of the present invention.

[0046] Figure 3 Graph showing hydrostatic pressure and overburden stress prediction results according to an embodiment of the present invention.

[0047] Figure 4 This is a result diagram of the normal compaction trend line corrected according to the relationship between the transverse wave time difference and the longitudinal wave time difference according to an embodiment of the present invention.

[0048] Figure 5 Graph showing the prediction results of the pore pressure of a single well according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0050] The invention aims at predicting the formation pressure by the conventional Eaton method, which is affected by gas content, organic matter, effective stress, etc. The relationship between the shear wave time difference and the longitudinal wave time difference is established, and the influence of gas content on the acoustic wave time difference is eliminated in combination with the core experiment results, thereby improving the accuracy of the Eaton method in predicting the formation pressure.

[0051] Embodiment 1

[0052] Figure 1 FIG. 1 is a flow chart of a formation pore pressure prediction method based on acoustic wave time difference curve correction according to the present invention. Figure 1 As shown, the present invention provides a formation pore pressure prediction method based on acoustic wave time difference curve correction, comprising:

[0053] Calculate the hydrostatic pressure and overlying formation pressure of the entire well section of a single well based on well logging data;

[0054] Construct the normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation;

[0055] Correcting the normal compaction trend line based on the relationship between the shear wave time difference and the longitudinal wave time difference;

[0056] The single well pore pressure is predicted based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

[0057] Specifically, the process of obtaining the hydrostatic pressure of the entire well section and the overlying formation pressure of a single well based on logging data is as follows:

[0058] Assuming that the pores inside the rock are not closed, but connected to each other and to the ground, the pore pressure at any point at a depth of h is caused by the weight of the fluid above that point, and the pore pressure at this time is the hydrostatic pressure. As the weight of the fluid exerting downward force from above increases, the hydrostatic pressure increases proportionally with the depth measured from the surface, so the expression is:

[0059] Ph =ρ w gh(1)

[0060] Among them, ρ w is the density of water, g is the acceleration due to gravity, and h is the depth of the formation.

[0061] The in-situ stress is mainly generated by the overburden pressure, which is also called confining pressure or vertical stress. It is the pressure formed by the weight of all matrix and fluid above a given formation. Its integral expression is as follows:

[0062]

[0063] in, is the formation porosity, ρ ma is the rock skeleton density, ρ f is the pore fluid density.

[0064] Generally, the logging curve does not give the density of the entire well section, so the relationship between depth and density is fitted based on the density data, and the overburden pressure is calculated by integration. The overburden pressure increased per unit depth is defined as its gradient, which is determined by the density change. The following expression is used to interpolate the density data at equal intervals to obtain the gradient of the overburden pressure of the entire well section:

[0065]

[0066] Among them, G c is the pressure gradient of the overburden, ρ 0 and h 0 is the average density and thickness of the stratum without density, ρ bi is the scattered data of density, and Δh is the depth interval.

[0067] Specifically, the process of constructing the normal compaction trend line of the stratum based on the acoustic time difference and the burial depth of the stratum is as follows:

[0068] In shale and mudstone formations, the method that relies on the normal compaction trend line has been well applied. In the selection of the normal compaction trend line, there are certain differences between the results selected based on experience and standards. When predicting formation pressure, the acoustic time difference, density, resistivity and other logging curves will be affected by the wellbore and other factors. Usually, the acoustic time difference curve with less influence is selected to establish the normal compaction trend line:

[0069] ln(Δt)=a×H TVD +b(4)

[0070] Among them, Δt is the measured formation acoustic time difference, H TVD is the vertical depth, a and b are regression fitting coefficients, where b = ln(Δt 0 ), Δt 0It is the sound wave time difference in the shallow layer of the surface.

[0071] Specifically, the implementation process of correcting the normal compaction trend line based on the relationship between the transverse wave time difference and the longitudinal wave time difference is as follows:

[0072] The selection of compaction parameters corresponding to abnormal formation pressure is based on mudstone, so the normal compaction point should be selected in the mudstone section, especially the thick mudstone section. Because the points deviating from the normal trend line usually represent the existence of abnormal formation pressure, these points should be identified when selecting normal compaction points.

[0073] The longitudinal wave time difference and shear wave time difference curves are fitted for the selected mudstone section to determine the relationship between the two:

[0074] Δt DTC =a×Δt DTS +b(5)

[0075] Among them, Δt DTC is the measured longitudinal wave time difference, Δt DTS is the measured shear wave time difference, a and b are the regression fitting coefficients.

[0076] Since the shear wave time difference curve is almost less affected by the fluid, the relationship between the two is determined, the shear wave time difference is re-substituted into the relationship (5), the new acoustic wave time difference curve is fitted, and the normal compaction trend line of the formation is further repeatedly constructed based on the acoustic wave time difference and the burial depth of the rock formation to obtain the corrected normal compaction trend line.

[0077] Specifically, the process of predicting the pore pressure of a single well based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line is as follows:

[0078] Eaton method is the most commonly used method for predicting formation pressure. This method combines compaction theory and abnormal high pressure formation mechanism, and establishes a relationship model between measured pressure and well logging information to predict formation pressure. The calculation formula based on Eaton method is:

[0079]

[0080] Among them, Δt n is the formation acoustic wave time difference obtained on the normal compaction trend line, Δt is the measured formation acoustic wave time difference, and p p is the formation pore pressure, p 0 is the overlying formation pressure, p f is the hydrostatic pressure and c is the Eaton index.

[0081] Embodiment 2

[0082] Figure 2FIG. 1 is a flow chart of a method for predicting pore pressure in mudstone formations based on acoustic time difference curve correction according to an embodiment of the present invention. Figure 2 As shown, this embodiment takes the continental shale gas reservoir in the Sichuan Basin of China as an example to illustrate the mudstone formation pore pressure prediction method based on the correction of the acoustic wave time difference curve of the present invention.

[0083] The terrestrial shale gas reservoirs in the Sichuan Basin of China are rich in resources. Accurate prediction of pore pressure helps to evaluate the effectiveness of the caprock, reduce complex downhole accidents, achieve high-quality, efficient and safe drilling, and effectively protect the oil and gas layers. The Eaton method relies on the normal compaction trend line to predict pore pressure. This embodiment aims to establish the relationship between the longitudinal wave time difference and the transverse wave time difference in the gas-bearing section of the formation, and eliminate the influence of gas content as much as possible, thereby improving the prediction of the Eaton method. Taking the terrestrial shale gas reservoir in the Sichuan Basin of China as an example, the method provided by the present invention is used to predict pore pressure.

[0084] In order to fully demonstrate the details of using the acoustic time difference to correct the normal compaction trend line and further improve the accuracy of pore pressure prediction, the specific process of pore pressure prediction is as follows: Figure 2 shown.

[0085] First, obtain logging data, including density, well diameter, compensated acoustic wave and other data. Next, use the depth and density curves to calculate the hydrostatic pressure and overburden formation pressure, and use the three-point extrapolation method to obtain the hydrostatic pressure and overburden formation pressure of the entire well section. The prediction results are as follows: Figure 3 shown.

[0086] Next, the shear wave time difference and longitudinal wave time difference curves of the pure shale section are selected, the relationship between the two is fitted, and the points obviously affected by gas content are removed. The corrected acoustic wave time difference data is further obtained, and the normal compaction trend curve of the selected formation section is obtained by fitting, and the normal compaction trend curve of the whole well section is further obtained, such as Figure 4 shown.

[0087] Finally, using the corrected normal compaction trend curve, the parameters of the formula and the constant c are obtained from the drilling data, and the formation pore pressure is further calculated using the Eaton formula. Figure 5 As shown in Figure 2, the pore pressure of the reservoir section is mainly concentrated in the range of 1.7 to 1.9 g / cm 3 , which is consistent with the measured pore pressure results.

[0088] Embodiment 3

[0089] This embodiment provides a formation pore pressure prediction device based on acoustic wave time difference curve correction, including:

[0090] The calculation module calculates the hydrostatic pressure of the entire well section and the overlying formation pressure of a single well based on the logging data;

[0091] A construction module is used to construct a normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation;

[0092] A correction module, which corrects the normal compaction trend line based on the relationship between the transverse wave time difference and the longitudinal wave time difference;

[0093] The prediction module predicts the single well pore pressure based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

[0094] Embodiment 4

[0095] This embodiment provides an electronic device, the electronic device comprising:

[0096] A memory storing executable instructions;

[0097] A processor runs the executable instructions in the memory to implement the above-mentioned formation pore pressure prediction method based on acoustic wave time difference curve correction.

[0098] Embodiment 5

[0099] This embodiment provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for predicting formation pore pressure based on acoustic wave time difference curve correction is implemented.

[0100] The above-mentioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or mobile hard disk), media with built-in rewritable non-volatile memory (e.g., memory card) and media with built-in ROM (e.g., ROM box).

[0101] In summary, the method for predicting pore pressure in mudstone formations based on the correction of the acoustic time difference curve of the present invention has the following characteristics: In shale and mudstone formations, the method relying on the normal compaction trend line has been well applied. In the selection of the normal compaction trend line, there are certain differences between the results selected according to experience and standards. At the same time, the acoustic time difference data of the normal compaction trend line comes from a pure mudstone formation. When the sedimentation compaction reaches a certain level, the acoustic time difference curve remains almost unchanged, which makes it difficult to select the trend line. If the formation belongs to a non-continuous sedimentary formation and contains faults caused by tectonic movement, it will also affect the selection of the normal trend line. The present invention selects the shear wave time difference of the gas-free section to establish a relationship with the longitudinal wave time difference curve, eliminates the influence of the gas content of the formation, and improves the accuracy of the Eaton method in predicting formation pressure.

[0102] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for predicting formation pore pressure based on the correction of acoustic time difference curves. It is characterized in that include: Calculate the hydrostatic pressure and overlying formation pressure of the entire well section of a single well based on well logging data; Construct the normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation; Correcting the normal compaction trend line based on the relationship between the shear wave time difference and the longitudinal wave time difference; The single well pore pressure is predicted based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

2. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 1, It is characterized in that The expression of the hydrostatic pressure is: P h =ρ w gh(1) Among them, ρ w is the density of water, g is the acceleration due to gravity, and h is the depth of the formation.

3. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 1, It is characterized in that The integral expression of the overlying formation pressure is as follows: in, is the formation porosity, ρ ma is the rock skeleton density, ρ f is the density of pore fluid, g is the acceleration of gravity, and h is the formation depth.

4. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 3, It is characterized in that The following expression is used to interpolate the density data at equal intervals to obtain the gradient of the overburden pressure in the entire well section: Among them, G c is the pressure gradient of the overburden, ρ 0 and h 0 is the average density and thickness of the stratum without density, ρ bi is the scattered data of density, and Δh is the depth interval.

5. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 1, It is characterized in that The normal compaction trend line of the formation constructed based on the acoustic time difference and the burial depth of the rock formation is expressed as: ln(Δt)=a×H TVD +b(4) Among them, Δt is the measured formation acoustic time difference, H TVD is the vertical depth, a and b are regression fitting coefficients, where b = ln(Δt 0 ), Δt 0 It is the sound wave time difference in the shallow layer of the surface.

6. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 1, It is characterized in that The correction of the normal compaction trend line based on the relationship between the shear wave time difference and the longitudinal wave time difference comprises: The longitudinal wave time difference and shear wave time difference curves are fitted for the selected mudstone section to determine the relationship between the two: Δt DTC =a×Δt DTS +b(5) Among them, Δt DTC is the measured longitudinal wave time difference, Δt DTS is the measured shear wave time difference, a and b are regression fitting coefficients; Substitute the shear wave time difference into equation (5) again, fit a new acoustic wave time difference curve, and further repeat the calculation of a new normal compaction trend line based on the acoustic wave time difference and the burial depth of the rock formation.

7. The formation pore pressure prediction method based on acoustic wave time difference curve correction according to claim 1, It is characterized in that The single well pore pressure is predicted based on the obtained hydrostatic pressure, overlying formation pressure and the corrected normal compaction trend line, and the calculation formula based on the Eaton method is: Among them, Δt n is the formation acoustic wave time difference obtained on the normal compaction trend line, Δt is the measured formation acoustic wave time difference, and p p is the formation pore pressure, p 0 is the overlying formation pressure, p f is the hydrostatic pressure and c is the Eaton index.

8. A formation pore pressure prediction device based on acoustic wave time difference curve correction, It is characterized in that include: The calculation module calculates the hydrostatic pressure of the entire well section and the overlying formation pressure of a single well based on the logging data; A construction module is used to construct a normal compaction trend line of the formation based on the acoustic time difference and the burial depth of the rock formation; A correction module, which corrects the normal compaction trend line based on the relationship between the transverse wave time difference and the longitudinal wave time difference; The prediction module predicts the single well pore pressure based on the acquired hydrostatic pressure, overburden formation pressure and the corrected normal compaction trend line.

9. An electronic device, It is characterized in that The electronic device comprises: A memory storing executable instructions; A processor, wherein the processor runs the executable instructions in the memory to implement the formation pore pressure prediction method based on acoustic wave time difference curve correction as described in any one of claims 1-7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, It is characterized in that When the computer program is executed by a processor, the method for predicting formation pore pressure based on acoustic wave time difference curve correction as described in any one of claims 1 to 7 is implemented.

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