A method and apparatus for predicting in-situ fracture opening under overpressure fluid.

Abstract

A method and apparatus for predicting in-situ fracture opening under overpressure fluid conditions, the method comprising: calculating the formation pore pressure at the depth to be predicted based on the overlying formation pressure and the normal compacted pore pressure; calculating the current horizontal maximum principal stress at the depth to be predicted using the maximum principal stress formula based on the overlying formation pressure; determining a fracture opening factor at the depth to be predicted based on the formation pore pressure and the current horizontal maximum principal stress; and determining the in-situ fracture opening at the depth to be predicted based on the fracture opening factor.

Description

Technical Field

[0001] This article relates to the field of oil and gas geological reservoir property prediction technology, and in particular to a method and apparatus for predicting in-situ fracture opening under overpressure fluid. Background Technology

[0002] Regarding the opening and closing of structural fractures in oil and gas reservoirs, the definition is that a fracture is closed when its two sides come into contact, and open when they do not. When a fracture is open, the (effective) stress in the rock is greater than 0; when it is closed, it is not 0 and may be under pressure. For interlocking fractures, the two sides do not come into contact when open, so there is no interaction; when open, the fracture has strong conductivity, and when closed, it has no conductivity. For infilled fractures, the definition is the same: contact indicates closure, and no contact indicates opening; however, in this case, opening and closing are accomplished by filling particles. The stress is greater than 0 when open, and the effective stress is not 0 when closed. Although closed, the fracture's conductivity is not zero.

[0003] The actual situation underground is more complex. The fracture surface may not be straight or interlocking, but rather uneven, and some fractures may have been partially eroded into cavities. Due to the shape of the fracture, the two side walls cannot be in complete contact, only partial contact, just as the perimeter of a pore cannot be completely in contact. The phenomenon of drill bit falling during drilling indicates that the drill bit has entered a partially opened section of a fracture or a karst cave. Natural fractures are widely developed and complexly distributed in carbonate rock formations, and the opening and expansion of closed fractures is a major cause of fracture leakage in this type of formation, directly affecting safe and efficient drilling, and even impacting the exploration and development process.

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

[0005] The inventors of this application discovered that:

[0006] Formation fluid pressure and current maximum principal stress are the main factors affecting the opening of reservoir fractures. In some technologies, the opening of fractures is determined indirectly or directly by methods such as the prediction method of the angle between the current maximum principal stress and the fracture direction, the fracture cementation and filling factor method, the drilling fluid permeation rate method, and the logging data interpretation and characterization method.

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

[0008] To address the aforementioned problems, the inventors proposed a method and device for predicting fracture opening under the combined action of formation overpressure fluid pressure and current horizontal principal stress. This method is designed to quantitatively predict in-situ reservoir fracture opening based on well logging data, especially in situations with high exploration levels, limited drilling core data, and limited seismic data resolution. This will effectively guide the exploration and development of deep and ultra-deep oil and gas reservoirs.

[0009] This application provides a method and apparatus for predicting in-situ fracture opening under overpressure fluid conditions. The method determines the current maximum principal stress and formation pore pressure based on well logging data, and then quantitatively predicts the in-situ reservoir fracture opening.

[0010] In a first aspect, this application provides a method for predicting the in-situ fracture opening potential under overpressure fluid conditions, the method comprising:

[0011] Calculate the formation pore pressure at the depth to be predicted based on the overlying formation pressure and the normal compacted pore pressure.

[0012] The current maximum principal stress at the predicted depth point is calculated using the maximum principal stress formula based on the overlying formation pressure at the predicted depth point.

[0013] The fracture opening factor at the predicted depth is determined based on the formation pore pressure and the current maximum principal stress.

[0014] The in-situ crack opening capability at the depth to be predicted is determined based on the crack opening capability factor.

[0015] Secondly, embodiments of the present invention also provide an apparatus for predicting the in-situ fracture opening under overpressure fluid, the apparatus comprising: a memory and a processor; the memory is used to store a program for predicting the in-situ fracture opening under overpressure fluid, and the processor is used to read and execute the program for predicting the in-situ fracture opening under overpressure fluid, and execute the method described in any of the above embodiments.

[0016] Thirdly, embodiments of the present invention also provide a computer-readable storage medium storing a data processing program, wherein the data processing program is executed by a processor using any one of the above embodiments as a method for predicting in-situ fracture opening under overpressure fluid.

[0017] Compared with related technologies, this application provides a method and apparatus for predicting in-situ fracture opening under overpressure fluid conditions. The method includes: calculating the formation pore pressure at the depth to be predicted based on the overlying formation pressure and the normal compacted pore pressure; calculating the current horizontal maximum principal stress at the depth to be predicted using the maximum principal stress formula based on the overlying formation pressure; determining the fracture opening factor at the depth to be predicted based on the formation pore pressure and the current horizontal maximum principal stress; and determining the in-situ fracture opening at the depth to be predicted based on the fracture opening factor. This application predicts fracture opening under the combined action of formation overpressure fluid pressure and current horizontal principal stress, enabling quantitative prediction of in-situ reservoir fracture opening based on well logging data even with high exploration levels, limited drilling core data, and limited seismic data resolution, thus effectively guiding the exploration and development of deep and ultra-deep oil and gas.

[0018] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0020] Figure 1 This is a flowchart illustrating a method for predicting in-situ fracture opening under overpressure fluid, as described in an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of a device for predicting in-situ crack opening under overpressure fluid, according to an embodiment of this application.

[0022] Figure 3 This is a schematic diagram illustrating the principle of enabling factors in some exemplary embodiments;

[0023] Figure 4 This is a schematic diagram illustrating the opening and closing properties of cracks in some exemplary embodiments;

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

[0025] Figure 6 A bar chart for evaluating and predicting fracture opening in the Jurassic Ahe Formation of the Dixi 1 well in the Kuqa Depression, in some exemplary embodiments.

[0026] Figure 7 A columnar section for evaluating and predicting fracture opening in the Jurassic Ahe Formation of the Dibei 102 well in the Kuqa Depression, as shown in some exemplary embodiments. Detailed Implementation

[0027] This application describes several embodiments, but these descriptions are exemplary and not restrictive, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, 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, or may replace, any feature or element of any other embodiment.

[0028] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application may also be combined with any conventional features or elements to form a unique inventive scheme as defined by the claims. Any feature or element of any embodiment may also be combined with features or elements from other inventive schemes to form another unique inventive scheme as defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application may be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes may be made within the scope of the appended claims.

[0029] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0030] This invention provides a method for predicting in-situ fracture opening under overpressure fluid conditions, such as... 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 using the maximum principal stress formula based on the overlying stratum pressure at the depth to be measured. 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 to be predicted;

[0034] S130: Determine the in-situ fracture opening capability under overpressure fluid based on the fracture opening capability factor.

[0035] In this embodiment, based on the theory of the resultant force of effective stress inside and outside the fracture, an opening factor F is established to reflect the combined effect of the overpressure fluid pressure inside the fracture and the current maximum horizontal principal stress outside the fracture, targeting the opening property of structural fractures in ultra-deep reservoirs. open ,like Figure 3 As shown, the crack initiation factor is:

[0036] F open =P p -σ H

[0037] In the above formula, F open P is the crack initiation factor. p For formation pore pressure, σ H This represents the maximum principal stress currently in operation.

[0038] In one exemplary embodiment, if the fracture opening factor is greater than 0, then the in-situ fracture under overpressure fluid is determined to be open.

[0039] If the crack opening factor is less than or equal to 0, then the in-situ crack under overpressure fluid is determined to be closed.

[0040] like Figure 4 The diagram shown illustrates the opening and closing properties of the crack. Figure 4 In the diagram, the left side represents an open structure, and the right side represents a closed structure.

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

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

[0043]

[0044] In the above formula, P p P is the formation pore pressure. pnFor normal compaction pore pressure, α is the Eaton coefficient, typically taken as 1; n is the Eaton exponent, typically taken as 9; Δt n Δt0 represents the sonic transit time of the normal trend line of mudstone, and Δt0 represents the sonic transit time of mudstone logging.

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

[0046] P pn =ρ f gh;

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

[0048] In one exemplary embodiment, such as Figure 5 As shown, the acoustic transit time Δt of the normal trend line of mudstone n for:

[0049] Δt n =Δt0×e -ch

[0050] In the above formula, Δt n The sonic transit time is the normal trend line of mudstone, where c is the normal trend line, such as... Figure 5 The slope of the dashed line is shown, and h is the vertical burial depth of the stratum at the depth point to be predicted.

[0051] In one exemplary embodiment, the overlying 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 one exemplary embodiment, the maximum principal stress formula is used to calculate the current horizontal maximum principal stress σ at the depth point to be predicted. H ;

[0055]

[0056] In the above formula, σ H σ represents the current maximum principal stress at the depth point to be predicted. v The maximum vertical principal stress is P0, which is the current overlying stratum pressure. v is the dynamic Poisson's ratio, and ε is the current maximum vertical principal stress. H ε is the correction factor for the maximum principal stress at horizontal levels, typically taken as 0.001;h is the horizontal minimum principal stress correction factor, which is generally taken as 0.001; E is the dynamic Young's modulus.

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

[0058]

[0059]

[0060]

[0061]

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

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

[0064] This invention also provides a device for predicting the in-situ fracture opening potential under overpressure fluid conditions, such as... 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 in-situ fracture opening under overpressure fluid, and the processor is used to read and execute the program for predicting the in-situ fracture opening under overpressure fluid, and to execute the method described in any of the above embodiments.

[0065] This invention also provides a computer-readable storage medium storing a data processing program, which is executed by a processor as described in any of the above embodiments, using the method for predicting in-situ fracture opening under overpressure fluid.

[0066] Example 1

[0067] This example uses a well in the Kelasu structural belt of the Kuqa Depression as an example. Given the drilling formation and logging data, it employs a method for predicting in-situ fracture opening under overpressure fluid conditions to predict reservoir fracture opening. The specific process is as follows:

[0068] Step 1. Using geological interpretation data from deep seismic profiles, combined with regional geological data, well logging density, and sonic data, select key target layers and determine their depth locations.

[0069] In the oil and gas basins of western my country, drilling and conventional logging data are relatively abundant; stratigraphic sequence data can be obtained from seismic profile data in addition to drilling data; and stratigraphic rock density and sonic transit time can be obtained from logging data.

[0070] Step 2. Calculate the overlying formation pressure

[0071]

[0072] In the above formula, P0 is the overlying formation pressure in MPa; z is the vertical depth in meters; and ρb is the density of the overlying strata in tons (kb). 3 kg / m 3 g is the acceleration due to gravity, 9.8 m / s; TVD is the maximum vertical burial depth, obtained from well logging data.

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

[0074]

[0075] P p P is the formation pore pressure. pn For normal compaction pore pressure, α is the Eaton coefficient, typically taken as 1; n is the Eaton exponent, typically taken as 9; Δt n Δt0 represents the sonic transit time of the normal trend line of mudstone, and Δt0 represents the sonic transit time 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 The density of formation water is generally taken as 1.0 g / cm³. 3 h is the vertical burial depth of the strata at the depth point to be predicted, and g is the gravitational acceleration.

[0079] Sonic transit time Δt of 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 dashed line), and h is the vertical burial depth of the stratum 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 to be predicted.

[0085] Step 7. Based on the fracture opening factor, comprehensively judge the opening status of the in-situ reservoir fractures.

[0086] The prediction results for the Jurassic Ahe Formation in Well Dixi 1 and Well Dibei 102 in the Kuqa Depression are as follows: Figure 6 and 7 As shown, the prediction results Figure 6 and 7 It can be seen that the overall fracture opening factor of the in-situ reservoir is >0. Combined with test and production data and imaging logging data, the fractures are mainly openable, indicating that the fracture opening of the in-situ reservoir is significantly coupled with the fluid overpressure stress-maximum horizontal principal stress.

[0087] The present application's embodiments enable accurate prediction of in-situ fracture opening under overpressure fluid conditions, given known drilling formations and logging data.

[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 is well 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 technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

Claims

1. A method for predicting in-situ fracture opening under overpressure fluid, characterized in that, The method includes: Calculate the formation pore pressure at the depth to be predicted based on the overlying formation pressure and the normal compacted pore pressure. The current maximum principal stress at the predicted depth point is calculated using the maximum principal stress formula based on the overlying formation pressure at the predicted depth point. The fracture opening factor at the predicted depth is determined based on the formation pore pressure and the current maximum principal stress. The in-situ crack opening capability at the depth to be predicted is determined based on the crack opening capability factor. The crack initiation factor is: F open =P p -σ H In the above formula, F open P is the crack initiation factor. p For formation pore pressure, σ H This represents the maximum principal stress at present. The formation pore pressure is: In the above formula, P p P is the formation pore pressure. pn The normal compaction pore pressure, α is the Eaton coefficient, n is the Eaton exponent, Δt n Δt0 represents the sonic transit time of the normal trend line of mudstone, and Δt0 represents the sonic transit time of mudstone logging. The formula for the maximum principal stress is: In the above formula, σ H The maximum principal stress at present level, σ v The maximum vertical principal stress is currently known, v is the dynamic Poisson's ratio, and ε is the maximum vertical principal stress. H ε is the correction factor for the maximum principal stress in the horizontal direction. h α is the horizontal minimum principal stress correction factor, E is the dynamic Young's modulus, and α is the Eaton coefficient.

2. The method for predicting in-situ fracture opening under overpressure fluid conditions according to claim 1, characterized in that, The normal compaction pore pressure P pn for: P pn =ρ f gh; In the above formula, P pn For normal compaction pore pressure, ρ f ρ is the density of the formation water, h is the vertical burial depth of the formation at the depth point to be predicted, and g is the gravitational acceleration.

3. The method for predicting in-situ fracture opening under overpressure fluid conditions according to claim 1, characterized in that, The acoustic transit time of the normal trend line of the mudstone is: Δt n =Δt0×e -ch In the above formula, Δt n denoted as , where is the sonic transit time of the normal trend line of the mudstone, is the normal trend line, and is the vertical burial depth of the strata at the depth point to be predicted.

4. The method for predicting in-situ fracture opening under overpressure fluid according to claim 1, characterized in that, The pressure of the overlying strata is: P0=g∫0 TVD ρ b (from) 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.

5. The method for predicting in-situ fracture opening under overpressure fluid conditions according to claim 1, characterized in that, The step of determining the in-situ crack opening potential at the predicted depth point based on the crack opening potential factor includes: If the crack opening factor is greater than 0, then the in-situ crack at the depth to be predicted is determined to be open. If the crack opening factor is less than or equal to 0, then the in-situ crack at the depth to be predicted is determined to be closed.

6. A device for predicting the opening potential of in-situ fractures under overpressure fluid, characterized in that, The device includes a memory and a processor; the memory is used to store a program for predicting in-situ fracture opening under overpressure fluid, and the processor is used to read and execute the program for predicting in-situ fracture opening under overpressure fluid, and to execute the method according to any one of claims 1-5.

7. A computer-readable storage medium storing a data processing program, the data processing program being executed by a processor as described in any one of claims 1-5, the method for predicting in-situ fracture opening under overpressure fluid.

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