Unconventional reservoir brittleness indication curve calculation method, system and equipment

Abstract

The invention provides an unconventional reservoir brittleness indication curve calculation method, system and device. The method comprises the steps that the shale content is determined according to a logging data curve and reservoir rock physical parameter information; and determining a brittleness indication curve according to the shale content and the logging porosity. According to the unconventional reservoir brittleness indication curve calculation method, system and equipment, on the basis of conventional longitudinal wave logging, density logging and porosity logging information, rock physical analysis is integrated, a brittleness indication curve calculation formula is constructed, calculation and evaluation of brittleness indication parameters under the conventional logging condition are achieved, the method does not depend on transverse wave logging information, and the method has the advantages of being simple in structure and convenient to operate. The shale gas reservoir brittleness index extraction method is high in applicability and accuracy, shale gas reservoir brittleness evaluation based on the shale gas reservoir brittleness index extraction method can effectively improve shale gas reservoir fracturing evaluation precision, and exploration and development risks are reduced.

Description

Technical Field

[0001] The invention belongs to the field of petroleum geophysical exploration, and in particular relates to a method, system and equipment for calculating an unconventional reservoir brittleness indicator curve. Background Art

[0002] With the continuous deepening of exploration, conventional reservoir exploration has gradually entered the development stage. In order to find new reserve growth points, unconventional exploration has received more and more attention, especially shale gas exploration. The reserves of shale gas resources are huge worldwide, and shale gas resources are also abundant in my country, especially in the Sichuan Basin, Tarim Basin and other regions. The main task of shale gas exploration is to find the target "sweet spot" area. The evaluation of shale gas reservoirs is mainly carried out from three aspects, namely the source rock quality of shale (TOC content), reservoir properties (porosity and saturation) and rock fracturing (brittleness index). TOC content determines the hydrocarbon generation capacity of shale, while the brittleness index determines the fracturing and fracture-forming capacity of shale. Since the porosity and permeability of shale itself are relatively low, it is necessary to perform fracturing transformation on shale reservoirs during the production process to obtain better oil and gas migration channels and increase the shale gas constant. Under the condition of given source rock quality, the brittleness index of shale determines the feasibility and production efficiency of exploration and development. Therefore, it is of great significance to carry out brittleness evaluation based on the characteristics of shale gas reservoirs in my country. By delineating favorable areas for shale fracturing, targeted exploration wells can be deployed to increase shale gas production. At present, conventional brittleness evaluation methods mainly include two methods: brittleness index calculation based on P- and S-wave information and brittleness index calculation based on mineral components. Among them, the first prediction method based on P- and S-wave information mainly uses P- and S-wave parameters to calculate elastic parameters such as Young's modulus or Poisson's ratio, and then establishes the relationship between elastic parameters and brittleness index. The problem of this method is that it has high data requirements. P- and S-wave logging information is required in well logging, and prestack seismic gathers are required in seismic. The brittleness index calculation method based on mineral components characterizes the brittleness by calculating the proportion of brittle mineral content, but the applicability of this method in different regions is relatively poor. It is necessary to carry out mineral type and content measurement for different regions or even different formations. In the application process, human factors have a serious impact, and there is a lack of rock physics theoretical basis.

[0003] In view of the problems existing in the conventional brittleness index evaluation method for shale gas exploration, the present invention proposes a brittleness index calculation method and device, which combines the advantages of the current brittleness index evaluation method, while overcoming the problems of high data requirements and serious human influence of the conventional method, and realizes the brittleness index evaluation based on conventional logging data, thereby improving the accuracy of shale gas exploration. This method is based on conventional longitudinal wave logging, density logging and porosity logging information, and integrates rock physics analysis to construct a brittleness indicator curve calculation formula to realize the calculation and evaluation of brittleness indicator parameters under conventional logging conditions. This method does not rely on shear wave logging information and is not affected by human factors. It is a brittleness index extraction method with strong applicability and high accuracy. The brittleness evaluation of shale gas reservoirs based on this method will effectively improve the accuracy of shale gas reservoir fracturing evaluation and reduce the risk of exploration and development. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for calculating the brittleness indicator curve of unconventional reservoirs, the method comprising:

[0005] Determine the shale content based on the well logging data curve and reservoir rock physical parameter information;

[0006] The brittleness indication curve is determined based on the mud content and logging porosity.

[0007] Further, the logging data curve includes compressional wave velocity, density and porosity;

[0008] The reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of the clay and the density of the clay.

[0009] Further, the mud content is expressed as:

[0010]

[0011] Where Vsh represents the mud content, ρ ma represents the density of the rock matrix, Vp represents the P-wave velocity, ρ represents the density, Vpma represents the P-wave velocity of the rock matrix, φ represents the porosity, Vpfl represents the P-wave velocity of the saturated fluid in the pores, ρ fl represents the density of the saturated fluid in the pores, ρ sh represents the density of clay, and Vpsh represents the longitudinal wave velocity of clay.

[0012] Furthermore, a brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

[0013] Further, the brittleness index is expressed as:

[0014]

[0015] Where BI represents the brittleness index and φ represents the porosity.

[0016] The present invention also provides a calculation system for an unconventional reservoir brittleness indication curve, the system comprising: a first determination unit and a curve determination unit,

[0017] The first determination unit is used to determine the shale content according to the well logging data curve and the reservoir rock physical parameter information;

[0018] The curve determination unit is in communication connection with the first determination unit and is used to determine the brittleness indication curve according to the mud content and the logging porosity.

[0019] Further, the logging data curve includes compressional wave velocity, density and porosity;

[0020] The reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of the clay and the density of the clay.

[0021] Further, the mud content is expressed as:

[0022]

[0023] Where Vsh represents the mud content, ρ ma represents the density of the rock matrix, Vp represents the P-wave velocity, ρ represents the density, Vpma represents the P-wave velocity of the rock matrix, φ represents the porosity, Vpfl represents the P-wave velocity of the saturated fluid in the pores, ρ fl represents the density of the saturated fluid in the pores, ρ sh represents the density of clay, and Vpsh represents the longitudinal wave velocity of clay.

[0024] Furthermore, the curve determination unit is used to determine the brittleness indication curve according to the shale content and the logging porosity, including:

[0025] The brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and the reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

[0026] Further, the brittleness index is expressed as:

[0027]

[0028] Where BI represents the brittleness index and φ represents the porosity.

[0029] The present invention also provides a device for calculating an unconventional reservoir brittleness indication curve, the device comprising at least one processor and at least one memory, the memory being electrically connected to the processor, wherein:

[0030] The memory stores instructions that can be executed by the at least one processor. The instructions are executed by the at least one processor so that the at least one processor can perform the above-mentioned method for calculating the unconventional reservoir brittleness indicator curve.

[0031] The unconventional reservoir brittleness indicator curve calculation method, system and equipment of the present invention are based on conventional longitudinal wave logging, density logging and porosity logging information, and comprehensive rock physical analysis to construct a brittleness indicator curve calculation formula to achieve brittleness indicator parameter calculation and evaluation under conventional logging conditions. This method does not rely on shear wave logging information and is not affected by human factors. It is a brittleness index extraction method with strong applicability and high accuracy. Conducting shale gas reservoir brittleness evaluation based on this method will effectively improve the accuracy of shale gas reservoir fracturing evaluation and reduce the risk of exploration and development.

[0032] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of a flow chart of a method for calculating an unconventional reservoir brittleness indication curve in an embodiment of the present invention is shown;

[0035] Figure 2 A schematic diagram of the structure of the unconventional reservoir brittleness indication curve calculation system in an embodiment of the present invention is shown;

[0036] Figure 3 A comparison diagram of the brittleness indication curve calculated in the embodiment of the present invention and the oil test conclusion is shown;

[0037] Figure 4 The diagram shows a distribution diagram of favorable shale gas reservoirs predicted based on the brittleness indication curve in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The present invention provides a method for calculating the brittleness indicator curve of an unconventional reservoir. Figure 1 The following is a schematic diagram of the process flow of the unconventional reservoir brittleness indicator curve calculation method in an embodiment of the present invention. Figure 1 The method includes determining the shale content according to the well logging data curve and the reservoir rock physical parameter information; and determining the brittleness indication curve according to the shale content and the well logging porosity.

[0040] Specifically, the logging data curve includes P-wave velocity, density and porosity; the reservoir rock physical parameters include P-wave velocity of rock matrix, density of rock matrix; P-wave velocity of saturated fluid in pores, density of saturated fluid in pores; P-wave velocity of clay and density of clay.

[0041] Specifically, the mud content is expressed as:

[0042]

[0043] Where Vsh represents the mud content, ρ ma represents the density of the rock matrix, Vp represents the P-wave velocity, ρ represents the density, Vpma represents the P-wave velocity of the rock matrix, φ represents the porosity, Vpfl represents the P-wave velocity of the saturated fluid in the pores, ρ fl represents the density of the saturated fluid in the pores, ρ sh represents the density of clay, and Vpsh represents the longitudinal wave velocity of clay.

[0044] Specifically, in an embodiment of the present invention, a brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

[0045] Specifically, the brittleness index is expressed as:

[0046]

[0047] Where BI represents the brittleness index and φ represents the porosity.

[0048] In the embodiment of the present invention, the calculation method of the unconventional reservoir brittleness indication curve is specifically described in conjunction with the accompanying drawings:

[0049] Step 101, obtaining the P-wave velocity, density and porosity logging curve data:

[0050] Specifically, the P-wave velocity, density and porosity logging curve data of the wells drilled in the research area are obtained. In the embodiment of the present invention, the logging curve data is within the scope of conventional logging data acquisition, and the method for obtaining the logging data is not limited;

[0051] Step 102: Input reservoir rock physical parameter information:

[0052] In the embodiment of the present invention, the input reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of clay and the density of clay; in the embodiment of the present invention, the rock matrix is ​​selected as quartz, and the saturated fluid in the pores is selected as natural gas, that is, the input rock physical parameters are the longitudinal wave velocity of quartz and the density of quartz, and the longitudinal wave velocity of natural gas and the density of natural gas; in the embodiment of the present invention, the selection of the rock matrix and the saturated fluid in the pores is an adaptive choice. Without departing from the technical concept of the present invention, only the change of the type of the rock matrix and the saturated fluid in the pores is also within the protection scope of the present invention;

[0053] Step 103: Determine the shale content according to the logging data curve and the reservoir rock physical parameter information, and determine the brittleness indication curve according to the shale content and the logging porosity:

[0054] In the embodiment of the present invention, according to rock physics theory, the calculation formula of the longitudinal wave velocity of the logging data curve is:

[0055]

[0056] Wherein, Vp represents the P-wave velocity in m / s, φ represents the porosity, dimensionless, Vsh represents the shale content, dimensionless, Vpma represents the P-wave velocity of the rock matrix, in m / s, Vpsh represents the P-wave velocity of the clay, in m / s, and Vpfl represents the P-wave velocity of the saturated fluid in the pores, in m / s;

[0057] The density calculation formula of the logging data curve is:

[0058] ρ=(1-φ-Vsh)ρ ma +Vshρ sh +φρ fl (2)

[0059] Where ρ represents the density of the shale reservoir, in g / cm 3 , ρ ma Indicates the density of the rock matrix (quartz) in g / cm3 , ρ sh Indicates the density of clay in g / cm 3 , ρ fl Indicates the density of natural gas saturated in the pores, in g / cm 3 ;

[0060] According to formula (1) and formula (2), the calculation formula of the mud content Vsh can be derived as follows:

[0061]

[0062] According to the brittleness index calculation formula:

[0063]

[0064] Among them, BI represents the brittleness index, φ represents the porosity, and Vsh represents the shale content;

[0065] Substituting the calculation formula of mud content into the brittleness index formula, the final brittleness index calculation formula can be obtained as shown below:

[0066]

[0067] According to the calculation formula of brittleness index, the acquired P-wave velocity, density, porosity logging curve and reservoir rock physical parameter information are substituted into it to calculate the brittleness indication curve;

[0068] Figure 3 The figure shows the comparison between the brittleness indication curve calculated in the embodiment of the present invention and the oil test conclusion. Figure 3 The left curve in the middle is the calculated brittleness indicator curve, and the right side is the interpretation conclusion of the oil test. The asterisk area in the figure is the actual drilling oil test area. The actual drilling results confirm that the area is a high-yield gas layer, and the corresponding shale rock is good in fracturing. After fracturing treatment, the connected pores in the area are greatly increased, and the oil and gas migration is smooth. The oil test results show that the gas production is high. The core sampling analysis confirms that the shale brittleness index in this area is large (greater than 30), which is significantly different from the overlying and underlying strata. Comparing the calculated brittleness indicator curve with the interpretation conclusion of the oil test, it can be seen that when the value of the brittleness indicator curve is greater than 30, it corresponds to the distribution range of the effective gas layer (dark area), and when the value of the brittleness indicator curve is less than or equal to 30, it corresponds to the distribution range of the invalid reservoir (light area). The analysis results show that the brittleness indicator curve calculated based on the method proposed in this application can accurately identify the distribution range of the effective shale gas reservoir, effectively reducing the risk of shale gas exploration.

[0069] Step 104: predict the distribution range of favorable shale gas reservoirs according to the brittleness indicator curve:

[0070] During the implementation process, the brittleness indication curve data body of the work area is calculated based on the brittleness indication curve constructed in step 103, and then the conclusion that the brittleness index determined by the core analysis is greater than 30 is judged as an effective reservoir, and the prediction of shale gas effective reservoirs within the work area is carried out. Figure 4 This is a distribution map of favorable shale gas reservoirs predicted based on the brittleness indicator curve in the embodiment. The dark area in the figure corresponds to the range where the brittleness indicator curve value is greater than 30, and the light area corresponds to the range where the brittleness indicator curve value is less than or equal to 30. The well-1 in the figure that has been drilled is a high-yield gas well at the depth of the target layer, and the predicted brittleness indicator curve value at the corresponding well point reaches about 90, which confirms that the predicted brittleness indicator curve is consistent with the drilling conclusion, and according to the distribution law of the predicted brittleness indicator curve plane map, it is judged that the area belongs to river phase deposition. The prediction result is consistent with the understanding of petroleum geological deposition in the area, which further confirms the effectiveness of the method. The prediction results of the embodiment show that the brittleness indicator curve constructed by this method can effectively indicate the distribution law of the brittleness index of the shale gas reservoir, and is a reliable technical means for predicting shale gas reservoirs.

[0071] In an embodiment of the present invention, a system for calculating an unconventional reservoir brittleness indication curve is also provided. Figure 2 The schematic diagram of the structure of the unconventional reservoir brittleness indication curve calculation system in the embodiment of the present invention is shown. The system includes: a first determination unit and a curve determination unit.

[0072] The first determination unit is used to determine the shale content according to the well logging data curve and the reservoir rock physical parameter information;

[0073] The curve determination unit is in communication connection with the first determination unit and is used to determine the brittleness indication curve according to the mud content and the logging porosity.

[0074] Specifically, the logging data curve includes compressional wave velocity, density and porosity;

[0075] The reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of the clay and the density of the clay.

[0076] Specifically, the curve determination unit is used to determine the brittleness indication curve according to the shale content and the logging porosity, including:

[0077] The brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and the reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

[0078] The unconventional reservoir brittleness indicator curve calculation method, system and equipment of the present invention combine the advantages of the current brittleness index evaluation method, while overcoming the problems of high data requirements and serious human influence of conventional methods, realizing brittleness index evaluation based on conventional logging data, and improving the accuracy of shale gas exploration. This method is based on conventional longitudinal wave logging, density logging and porosity logging information, and integrates rock physics analysis to construct a brittleness indicator curve calculation formula to realize the calculation and evaluation of brittleness indicator parameters under conventional logging conditions. This method does not rely on shear wave logging information and is not affected by human factors. It is a brittleness index extraction method with strong applicability and high accuracy. The brittleness evaluation of shale gas reservoirs based on this method will effectively improve the accuracy of shale gas reservoir fracturing evaluation and reduce the risk of exploration and development.

[0079] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the brittleness indicator curve of unconventional reservoirs, characterized in that: The method comprises: Determine the shale content based on the well logging data curve and reservoir rock physical parameter information; The brittleness indication curve is determined based on the mud content and logging porosity.

2. The method for calculating the unconventional reservoir brittleness indicator curve according to claim 1, characterized in that: The logging data curve includes compressional wave velocity, density and porosity; The reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of the clay and the density of the clay.

3. The method for calculating the unconventional reservoir brittleness indicator curve according to claim 1 or 2, characterized in that: The mud content is expressed as: Where Vsh represents the mud content, ρ ma represents the density of the rock matrix, Vp represents the P-wave velocity, ρ represents the density, Vpma represents the P-wave velocity of the rock matrix, φ represents the porosity, Vpfl represents the P-wave velocity of the saturated fluid in the pores, ρ fl represents the density of the saturated fluid in the pores, ρ sh represents the density of clay, and Vpsh represents the longitudinal wave velocity of clay.

4. The method for calculating the unconventional reservoir brittleness indicator curve according to claim 3, characterized in that: The brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and the reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

5. The method for calculating the unconventional reservoir brittleness indicator curve according to claim 4, characterized in that: The brittleness index is expressed as: Where BI represents the brittleness index and φ represents the porosity.

6. An unconventional reservoir brittleness indicator curve calculation system, characterized in that: The system comprises: a first determination unit and a curve determination unit, The first determination unit is used to determine the shale content according to the well logging data curve and the reservoir rock physical parameter information; The curve determination unit is in communication connection with the first determination unit and is used to determine the brittleness indication curve according to the mud content and the logging porosity.

7. The unconventional reservoir brittleness indication curve calculation system according to claim 6, characterized in that: The logging data curve includes compressional wave velocity, density and porosity; The reservoir rock physical parameters include the longitudinal wave velocity of the rock matrix, the density of the rock matrix; the longitudinal wave velocity of the saturated fluid in the pores, the density of the saturated fluid in the pores; the longitudinal wave velocity of the clay and the density of the clay.

8. The unconventional reservoir brittleness indication curve calculation system according to claim 6 or 7, characterized in that: The mud content is expressed as: Where Vsh represents the mud content, ρ ma represents the density of the rock matrix, Vp represents the P-wave velocity, ρ represents the density, Vpma represents the P-wave velocity of the rock matrix, φ represents the porosity, Vpfl represents the P-wave velocity of the saturated fluid in the pores, ρ fl represents the density of the saturated fluid in the pores, ρ sh represents the density of clay, and Vpsh represents the longitudinal wave velocity of clay.

9. The unconventional reservoir brittleness indication curve calculation system according to claim 8, characterized in that: The curve determination unit is used to determine the brittleness indication curve according to the shale content and the logging porosity, including: The brittleness index is determined according to the shale content and the logging porosity, and the logging data curve and the reservoir rock physical parameter information are substituted into the brittleness index to obtain a brittleness indication curve.

10. The unconventional reservoir brittleness indication curve calculation system according to claim 9, characterized in that: The brittleness index is expressed as: Where BI represents the brittleness index and φ represents the porosity.

11. An unconventional reservoir brittleness indicator curve calculation device, characterized in that: The device comprises at least one processor and at least one memory, wherein the memory is electrically connected to the processor, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 5.

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