Method and device for predicting opening property of in-situ fracture under overpressure fluid

Abstract

The invention discloses a method and device for predicting opening performance of an in-situ fracture under overpressure fluid, and the method comprises the steps: calculating the formation pore pressure of a to-be-predicted depth point according to the overlying formation pressure and the normal compaction pore pressure of the to-be-predicted depth point; calculating the current horizontal maximum principal stress of the to-be-predicted depth point by using a maximum principal stress formula according to the overlying formation pressure of the to-be-predicted depth point; determining a crack opening factor of a to-be-predicted depth point according to the formation pore pressure and the current horizontal maximum principal stress; and determining the in-situ crack openability of the to-be-predicted depth point according to the crack openability factor.

Description

Technical Field

[0001] The present invention relates to the technical field of prediction of petroleum and natural gas geological reservoir properties, and in particular to a method and device for predicting the openability of in-situ fractures under overpressure fluid. Background Art

[0002] Regarding the opening and closing of structural cracks in oil and gas reservoirs, it is defined as closed when the two sides of the crack are in contact, and open when there is no contact. When the crack is open, the (effective) stress of the rock is greater than 0, and it is not 0 when it is closed, and it may be (under pressure). For meshing fractures, the two sides are not in contact when open, and there can be no interaction; there is strong conductivity when open, and no conductivity when closed. For filled fractures, the definition is the same, contact is closed, and no contact is open; however, at this time, the opening and closing are completed by filling particles, the stress when opening is greater than 0, and the effective stress when closing is not 0. Although closed, the conductivity of the fracture is not 0.

[0003] The actual situation underground is more complicated. The fracture surface may not be straight or meshed, but uneven. Some fractures are partially dissolved into holes. Due to the fracture shape, the two walls cannot be fully in contact, but only partially in contact, just like the four sides of the pore cannot be fully in contact. The phenomenon of drill drop during drilling indicates that the drill is drilled into the local open part of the fracture or in a cave. Natural fractures in carbonate formations are widely developed and complexly distributed, and the opening and expansion of closed fractures is an important reason for the leakage of fractures in such formations, which is directly related to safe and efficient drilling, and even affects the exploration and development process.

[0004] Therefore, effective prediction of in-situ fracture openness under overpressure fluid is crucial for exploration and development. Summary of the invention

[0005] The inventors of the present application discovered that:

[0006] Formation fluid pressure and the current maximum principal stress are the main factors affecting the openness of reservoir fractures. Some technologies use methods such as the prediction of the angle between the current maximum principal stress and the fracture trend, the fracture cementation filling factor method, the drilling fluid percolation rate method, and the logging data interpretation characterization method to indirectly or directly determine the openness of fractures.

[0007] The physical simulation and mathematical prediction of reservoir fractures mentioned above are to simulate and predict the parameter characteristics (density, occurrence and aperture, etc.) of reservoir fractures under normal overburden pressure compaction conditions. However, the above methods cannot be used to simulate and predict abnormally high-pressure foreland basins.

[0008] In response to the above problems, the inventors proposed a method and device for predicting the fracture openness under the combined action of formation overpressure fluid pressure and current horizontal principal stress. The method and device are aimed at quantitatively predicting the openness of in-situ reservoir fractures based on logging data when the exploration degree is high, drilling core data is lacking and the resolution of seismic data is limited, so as to effectively guide the exploration and development of deep and ultra-deep oil and gas.

[0009] The present application provides a method and device for predicting the openness of in-situ fractures under overpressure fluid. The method determines the current horizontal maximum principal stress and formation pore pressure based on logging data, and then quantitatively predicts the openness of in-situ reservoir fractures.

[0010] In a first aspect, the present application provides a method for predicting the openability of an in-situ fracture under an overpressure fluid, the method comprising:

[0011] Calculate the formation pore pressure at the depth point to be predicted based on the overlying formation pressure and normal compaction pore pressure at the depth point to be predicted;

[0012] Calculate the current horizontal maximum principal stress at the depth point to be predicted using the maximum principal stress formula according to the overlying formation pressure at the depth point to be predicted;

[0013] Determine the fracture opening factor at the depth point to be predicted according to the formation pore pressure and the current horizontal maximum principal stress;

[0014] The in-situ fracture openness at the depth point to be predicted is determined according to the fracture openness factor.

[0015] In a second aspect, an embodiment of the present invention further provides a device for predicting the openness of in-situ cracks under overpressure fluid, the device comprising: a memory and a processor; the memory is used to store a program for predicting the openness of in-situ cracks under overpressure fluid, and the processor is used to read and execute the program for predicting the openness of in-situ cracks under overpressure fluid, and execute any one of the methods described in the above embodiments.

[0016] In a third aspect, an embodiment of the present invention further provides a computer-readable storage medium having a data processing program stored thereon, and the data processing program is executed by a processor to perform the method for predicting the openability of in-situ fractures under overpressure fluids described in any one of the above embodiments.

[0017] Compared with the related art, the present application provides a method and device for predicting the openness of in-situ fractures under overpressure fluid, the method comprising: calculating the formation pore pressure at the depth point to be predicted according to the overlying formation pressure and the normal compaction pore pressure at the depth point to be predicted; calculating the current horizontal maximum principal stress at the depth point to be predicted using the maximum principal stress formula according to the overlying formation pressure at the depth point to be predicted; determining the fracture openness factor at the depth point to be predicted according to the formation pore pressure and the current horizontal maximum principal stress; determining the in-situ fracture openness at the depth point to be predicted according to the fracture openness factor. The present application predicts the fracture openness under the combined action of the formation overpressure fluid pressure and the current horizontal principal stress, and realizes the quantitative prediction of the in-situ reservoir fracture openness by relying on logging data under the conditions of high exploration degree, lack of drilling core data and limited resolution of seismic data, so as to effectively guide the exploration and development of deep-ultra-deep oil and gas.

[0018] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0020] Figure 1 This is a flow chart of a method for predicting the openability of in-situ fractures under overpressure fluid according to an embodiment of the present application;

[0021] Figure 2 This is a schematic diagram of a device for predicting the openability of in-situ fractures under overpressure fluid according to an embodiment of the present application;

[0022] Figure 3 A schematic diagram of the principle of the opening factor in some exemplary embodiments;

[0023] Figure 4 A schematic diagram of crack opening and closing in some exemplary embodiments;

[0024] Figure 5 A schematic diagram of acoustic wave time difference of a normal trend line of a formation in some exemplary embodiments;

[0025] Figure 6 A bar chart showing the evaluation and prediction of fracture openness of the Jurassic Ahe Formation in the Dixi 1 well in the Kuche Depression in some exemplary embodiments

[0026] Figure 7 A bar chart showing the evaluation and prediction of fracture openness of the Jurassic Ahe Formation in the Dibei 102 well in the Kuche Depression in some exemplary embodiments. DETAILED DESCRIPTION

[0027] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0028] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0029] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0030] The embodiment of the present invention provides a method for predicting the opening of in-situ fractures under overpressure fluid. Figure 1 As shown, the method includes steps S100-S130:

[0031] S100: Calculate the formation pore pressure P at the depth to be predicted based on the overlying formation pressure and normal compaction pore pressure at the depth to be measured. p ;

[0032] S110: Calculate the current horizontal maximum principal stress σ at the depth to be predicted based on the overlying formation pressure at the depth to be measured using the maximum principal stress formula H ;

[0033] S120: Based on the determined formation pore pressure P p and the current maximum principal stress σ H Determine the crack opening factor at the depth point to be predicted;

[0034] S130: Determine the in-situ fracture openness under the overpressure fluid according to the fracture openness factor.

[0035] In this embodiment, based on the theory of the combined force of effective stress inside and outside the fracture, the opening factor F is established to reflect the combined effect of the internal overpressure fluid pressure of the reservoir fracture and the external maximum horizontal principal stress at present. open ,like Figure 3 As shown in Figure 2, the crack opening factor is:

[0036] F open =P p -σ H

[0037] In the above formula, F open is the crack opening factor, P p is the formation pore pressure, σ H is the current maximum horizontal principal stress.

[0038] In an exemplary embodiment, if the fracture openness factor is greater than 0, it is determined that the in-situ fracture is open under the overpressure fluid;

[0039] If the fracture openness factor is less than or equal to 0, it is determined that the in-situ fracture is closed under the overpressure fluid.

[0040] like Figure 4 The schematic diagram of crack opening and closing is shown in Figure 4 In the figure, the left picture is open and the right picture is closed.

[0041] In an exemplary embodiment, the formation pore pressure P at the depth to be predicted is calculated based on the overlying formation pressure and the normal compaction pore pressure at the depth to be measured. p ;

[0042] Among them, the formation pore pressure P p for:

[0043]

[0044] In the above formula, P p is the formation pore pressure, P pnis the normal compaction pore pressure, α is the Eaton coefficient, which is generally 1; n is the Eaton index, which is generally 9; Δt n is the acoustic time difference of the normal trend line of mudstone, and Δt0 is the acoustic time difference of mudstone logging.

[0045] In an exemplary embodiment, the normal compaction pore pressure P pn for:

[0046] P pn =ρ f gh;

[0047] In the above formula, P pn is the normal compaction pore pressure, ρ f is the density of formation water, h is the vertical depth of the formation at the depth point to be predicted, and g is the gravitational acceleration.

[0048] In an exemplary embodiment, Figure 5 As shown, the acoustic time difference Δt of the normal trend line of mudstone n for:

[0049] Δt n =Δt0×e -ch

[0050] In the above formula, Δt n is the acoustic time difference of the normal trend line of mudstone, c is the normal trend line, such as Figure 5 Shown is the slope of the dotted line, and h is the vertical depth of the stratum at the depth point to be predicted.

[0051] In an exemplary embodiment, the overburden formation pressure p0 is:

[0052]

[0053] In the above formula, P0 is the overlying stratum pressure, z is the vertical burial depth of the stratum, ρb is the density of the overlying stratum, g is the gravitational acceleration, and TVD is the maximum vertical burial depth of the stratum.

[0054] In an exemplary embodiment, the maximum principal stress formula calculates the current horizontal maximum principal stress σ at the depth point to be predicted based on the maximum principal stress formula H ;

[0055]

[0056] In the above formula, σ H is the current maximum horizontal principal stress at the depth to be predicted, σ v is the current maximum vertical principal stress, that is, the current overlying stratum pressure P0, v is the dynamic Poisson's ratio, ε H is the correction coefficient of the maximum horizontal principal stress, which is generally taken as 0.001; εh is the horizontal minimum principal stress correction coefficient, which is generally taken as 0.001; E is the dynamic Young's modulus.

[0057] In this embodiment, the dynamic Poisson's ratio and the dynamic Young's modulus can be calculated and determined according to the following formula:

[0058]

[0059]

[0060]

[0061]

[0062] In the above formula, G dyn is the dynamic shear modulus, K dyn is the dynamic bulk modulus, ν dyn is the dynamic Poisson's ratio, E dyn is the dynamic Young's modulus; DTSM is the shear wave time difference, which can be obtained according to well logging; DTCO is the longitudinal wave time difference, which can be obtained according to well logging.

[0063] The method for predicting the in-situ fracture openness under overpressure fluid implemented in this embodiment superimposes the current maximum horizontal principal stress on the basis of the overpressure fluid pressure in the formation, realizes a comprehensive analysis of the key factors of reservoir fracture openness under burial conditions, quantitatively obtains the fracture openness index, and reduces the singleness and non-universality of the research results caused by single reliance on imaging logging, the angle between the fracture direction and the current principal stress, and drilling leakage.

[0064] The embodiment of the present invention also provides a device for predicting the opening of in-situ cracks under overpressure fluid. Figure 2 As shown, the device includes: a memory 210 and a processor 220; the memory is used to store a program for predicting the opening of in-situ fractures under overpressure fluid, and the processor is used to read and execute the program for predicting the opening of in-situ fractures under overpressure fluid, and execute any one of the methods in the above embodiments.

[0065] An embodiment of the present invention further provides a computer-readable storage medium having a data processing program stored thereon. The data processing program is executed by a processor to perform the method for predicting the openability of in-situ fractures under overpressure fluid described in any one of the above embodiments.

[0066] Example 1

[0067] This example takes the relevant wells in the Kelasu structural zone of the Kuqa Depression as an example. When the drilling formation and logging data are known, the method of predicting the in-situ fracture openness under overpressure fluid is used to predict the reservoir fracture openness. The specific process is as follows:

[0068] Step 1. Use the geological interpretation data of deep seismic profiles, combined with regional geological data and logging density and acoustic wave data, to select key target layers and clarify the depth position.

[0069] In the oil and gas basins in western my country, drilling data and conventional logging data are already relatively abundant; in addition to drilling data, stratigraphic sequences can also be obtained from seismic profile data; and formation rock density and acoustic wave time difference can be obtained from logging data.

[0070] Step 2. Calculate the overburden pressure

[0071]

[0072] In the above formula, P0 is the overlying stratum pressure, in MPa; z is the vertical depth, in m; ρb is the overlying stratum density, in 10 3 kg / m 3 ; g is the acceleration due to gravity, 9.8 m / s; TVD is the maximum vertical burial depth, obtained from logging data.

[0073] Step 3. Based on the measured fluid pressure, trend line and normal compaction pore pressure, calculate the formation pore pressure p at the depth to be predicted based on Formula 2 p :

[0074]

[0075] P p is the formation pore pressure, P pn is the normal compaction pore pressure, α is the Eaton coefficient, which is generally taken as 1; n is the Eaton index, which is generally taken as 9; Δt n is the acoustic time difference of the normal trend line of mudstone, and Δt0 is the acoustic time difference of mudstone logging.

[0076] The normal compaction pore pressure P pn for:

[0077] P pn =ρ f gh;

[0078] In the above formula, ρ f is the density of formation water, generally 1.0g / cm 3 ; h is the vertical depth of the stratum to be predicted, and g is the gravitational acceleration.

[0079] The acoustic time difference Δt of the normal trend line of mudstone n for:

[0080] Δt n =Δt0×e-ch

[0081] In the above formula, c is the slope of the normal trend line, i.e. the dotted line, and h is the vertical depth of the formation at the depth point to be predicted.

[0082] Step 4. Calculate the dynamic shear modulus, dynamic bulk modulus, dynamic Poisson's ratio, and dynamic Young's modulus.

[0083] Step 5. Calculate the current maximum horizontal principal stress σ at each depth point H .

[0084] Step 6. Based on the determined formation pore pressure P p and the current maximum principal stress σ H Determine the crack opening factor at the depth point to be predicted.

[0085] Step 7. Comprehensively judge the openness of the in-situ reservoir fractures based on the fracture openness factor.

[0086] The prediction results for the Jurassic Ahe Formation in the Dixi 1 well in the Kuche Depression and the Jurassic Ahe Formation in the Dibei 102 well in the Kuche Depression are as follows: Figure 6 and 7 As shown, the prediction from the results Figure 6 and 7 It can be seen that the overall opening factor of the in-situ reservoir fractures is >0. Combined with the test and trial production data and imaging logging data, the fractures are mainly open, indicating that the coupling relationship between the openness of the in-situ reservoir fractures and the fluid overpressure stress-maximum horizontal principal stress is obvious.

[0087] The prediction of in-situ fracture openability under overpressure fluid in the embodiment of the present application can achieve accurate prediction of in-situ fracture openability when the drilling formation and logging data are known.

[0088] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for predicting the openability of in-situ fractures under overpressure fluid, characterized in that: The method comprises: Calculate the formation pore pressure at the depth point to be predicted based on the overlying formation pressure and the normal compaction pore pressure at the depth point to be predicted; Calculate the current horizontal maximum principal stress at the depth to be predicted using the maximum principal stress formula according to the overlying formation pressure at the depth to be predicted; Determine the fracture opening factor at the depth point to be predicted according to the formation pore pressure and the current horizontal maximum principal stress; The in-situ fracture openness at the depth point to be predicted is determined according to the fracture openness factor.

2. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 1, characterized in that: The crack opening factor is: F open =P p -σ H In the above formula, F open is the crack opening factor, P p is the formation pore pressure, σ H is the current maximum horizontal principal stress.

3. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 1, characterized in that: The formation pore pressure is: In the above formula, P p is the formation pore pressure, P pn is the normal compaction pore pressure, α is the Eaton coefficient, n is the Eaton index, Δt n is the acoustic time difference of the normal trend line of mudstone, and Δt0 is the acoustic time difference of mudstone logging.

4. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 3, characterized in that: The normal compaction pore pressure P pn for: P pn =ρ f gh; In the above formula, P pn is the normal compaction pore pressure, ρ f is the density of formation water, h is the vertical depth of the formation at the depth point to be predicted, and g is the gravitational acceleration.

5. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 3, characterized in that: The acoustic time difference of the normal trend line of the mudstone is: Δt n =Δt0×e -ch In the above formula, Δt n is the acoustic time difference of the normal trend line of mudstone, c is the normal trend line, and h is the vertical burial depth of the formation at the depth point to be predicted.

6. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 1, characterized in that: The overlying formation pressure is: In the above formula, P0 is the overlying stratum pressure, z is the vertical burial depth of the stratum, ρb is the overlying stratum density, g is the gravitational acceleration, and TVD is the maximum vertical burial depth.

7. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 1, characterized in that: The maximum principal stress formula is: In the above formula, σ H is the current maximum horizontal principal stress, σ v is the current maximum vertical principal stress, v is the dynamic Poisson's ratio, ε H is the horizontal maximum principal stress correction coefficient, ε h is the horizontal minimum principal stress correction coefficient, E is the dynamic Young's modulus, and α is the Eaton coefficient.

8. The method for predicting the opening of in-situ fractures under overpressure fluid according to claim 1, characterized in that: Determining the in-situ fracture openness at the depth point to be predicted according to the fracture openness factor includes: If the crack openness factor is greater than 0, it is determined that the in-situ crack at the predicted depth point is open; If the fracture openness factor is less than or equal to 0, it is determined that the in-situ fracture at the depth point to be predicted is closed.

9. A device for predicting the opening of in-situ cracks under overpressure fluid, characterized in that: The device comprises: a memory and a processor; the memory is used to store a program for predicting the openability of in-situ fractures under overpressure fluid, and the processor is used to read and execute the program for predicting the openability of in-situ fractures under overpressure fluid, and execute the method described in any one of claims 1-8.

10. A computer-readable storage medium having a data processing program stored thereon, wherein the data processing program is executed by a processor to perform the method for predicting the openability of in-situ fractures under overpressure fluid according to any one of claims 1 to 8.

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