A simulation method and device for hydraulic fracturing of sand-mud interlayers through interlayers

Abstract

The present invention relates to a simulation method for hydraulic fracturing of sand-mud interlayers penetrating interlayers, comprising: measuring geological parameters of different layers and different lithologies to obtain interlayer geological parameter measurement results; establishing a three-dimensional constitutive model of sand-mud interlayers according to the interlayer geological parameter measurement results; determining geometric parameters from the three-dimensional constitutive model of sand-mud interlayers according to the well section stratum conditions, performing grid division and setting calculation units, embedding zero-thickness cohesion fracture units in the calculation units to obtain unit grids; changing the displacement and viscosity of the sand-mud interlayer constitutive model under different interlayer thicknesses, establishing multiple groups of numerical models, performing finite element calculations on the multiple groups of numerical models, and obtaining the length and width of fractures that can penetrate the interlayer corresponding to the displacement and the viscosity. The fracture morphology corresponding to different combinations of penetrating interlayers can be compared, and the optimal displacement and viscosity can be selected.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum fracturing and exploitation, in particular to a method and a device for simulating the penetration of interlayers by hydraulic fracturing of sand-mud interlayers. Background Art

[0002] Sandstone is widely found in tight oil and gas reservoirs. Sandstone is mainly composed of minerals such as quartz and clay. The main components of oxides are SiO2 and Al2O3. The content of SiO2 and Al2O3 in sandstone is 60-95%. Due to its high burial depth, tight sandstone usually has the characteristics of low permeability and low porosity. Therefore, hydraulic fracturing technology is required for production increase operations, so as to form artificial fractures with high conductivity in the wellbore, enhance the ability of oil and gas to flow into the wellbore, and then improve the production capacity of oil and gas wells to achieve economic and efficient exploitation. Interlayer rocks of different thicknesses in the formation will limit the expansion effect of fractures. Interlayer refers to an impermeable rock layer that has a barrier effect on fluid movement during the development of the oil field. It is an important factor that must be considered when correctly dividing the development strata for various stratification process measures in heterogeneous multi-layer oil fields. Generally speaking, the interlayer in the clastic reservoir is mainly mudstone. In addition to the relatively pure mudstone, there are also some sand-mud transitional rocks, such as muddy siltstone and silty mudstone. Whether the sand-mud transition type of rock can be used as a barrier layer should be based on core data and their oil (fluid) content. Sand-mudstone without oil can be used as a barrier layer. In addition, changes in the flow rate and viscosity of the fracturing fluid will affect the degree of fracture in the rock, thus the final fracture penetration effect will be different. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a simulation method for hydraulic fracturing penetration of sand-mud interlayers based on finite elements in order to clarify the expansion law of hydraulic fracturing cracks in sand-mud interlayers and reveal the influence of the displacement and viscosity of the fracturing fluid on the penetration of hydraulic fractures.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A simulation method for hydraulic fracturing of sand-mud interlayers through interlayers, the steps are as follows:

[0006] Measure geological parameters of different layers and different lithologies, and obtain interlayer geological parameter measurement results;

[0007] According to the measurement results of interlayer geological parameters, a three-dimensional constitutive model of sand-mud interlayers is established;

[0008] According to the formation conditions of the well section, the geometric parameters are determined from the three-dimensional constitutive model of sand-mud interlayers, the grid is divided and the calculation unit is set, and the zero-thickness cohesion fracture unit is embedded in the calculation unit to obtain the unit grid;

[0009] By changing the displacement and viscosity of the three-dimensional constitutive model of sand-mud interlayers under different interlayer thicknesses, multiple sets of numerical models are established, and finite element calculations are performed on the multiple sets of numerical models to obtain the length and width of cracks that can penetrate the interlayer corresponding to the displacement and viscosity.

[0010] The geological parameters include at least one of the following combinations: density, elastic-plasticity, porosity, pressure parameter, Young's modulus, Poisson's ratio, permeability, porosity, pore pressure, minimum horizontal principal stress and vertical stress.

[0011] Establishing the three-dimensional constitutive model of sand-mud interlayers includes: establishing the three-dimensional constitutive model of elastic-plastic damaged sand-mud interlayers with different interlayer thicknesses according to the distribution of reservoir interlayers in the stratum.

[0012] Obtaining the unit grid includes: assigning differentiated material properties to the unit grid of the three-dimensional constitutive model of the sand-mud interlayer, setting the initial conditions, boundary conditions and stress conditions of the three-dimensional constitutive model of the sand-mud interlayer to establish a wellbore model that simulates the migration process of the fracturing fluid. After the wellbore model is established, the perforation position is determined, the wellbore friction resistance is considered, and the mechanical migration damage process of the fracturing fluid from the wellhead to the target formation is simulated.

[0013] Establishing multiple groups of numerical models includes: setting m different viscosities, n different displacements, and each interlayer thickness contains m×n numerical models.

[0014] Whether the hydraulic fracture passes through the interlayer is determined based on the crack extension results calculated by multiple sets of numerical models, and the results are grouped according to the thickness of the interlayer and plotted into a table.

[0015] According to the table, the displacement and viscosity combinations that meet the requirements of on-site fracturing construction are screened out, and the displacement and viscosity combinations that can penetrate the interlayer under the same interlayer thickness conditions are selected. The corresponding crack morphologies when different combinations penetrate the interlayer are compared, and the corresponding displacement and viscosity are selected to determine the crack morphology.

[0016] A simulation device for hydraulic fracturing of sand-mud interlayers through interlayers, comprising:

[0017] The first processing module is suitable for measuring geological parameters of different layers and different lithologies to obtain interlayer geological parameter measurement results;

[0018] The second processing module is suitable for establishing a three-dimensional constitutive model of sand-mud interlayers according to the measurement results of interlayer geological parameters;

[0019] The third processing module is adapted to determine geometric parameters from the three-dimensional constitutive model of sand-mud interlayers according to the formation conditions of the well section, perform grid division and set calculation units, and embed zero-thickness cohesion fracture units in the calculation units to obtain unit grids;

[0020] The fourth processing module is suitable for changing the displacement and viscosity of the three-dimensional constitutive model of sand-mud interlayers under different interlayer thicknesses, establishing multiple sets of numerical models, performing finite element calculations on the multiple sets of numerical models, and obtaining the length and width of cracks that can penetrate the interlayer corresponding to the displacement and viscosity.

[0021] A simulation device for hydraulic fracturing penetrating interlayers of sand and mud comprises: one or more processors, wherein the processors are configured to execute the steps of the above method.

[0022] A computer-readable storage medium stores a computer program, which executes the steps of the above method when executed by a processor.

[0023] The present invention adopts the above technical solution, which has the following advantages:

[0024] The simulation method of the present invention can accurately predict the penetration effect of hydraulic fractures in sand-mud interlayers under different displacements and viscosities, and optimize the displacement and viscosity of the fracturing fluid to achieve the best construction effect.

[0025] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used to illustrate the purpose of the preferred embodiment and are not considered to be limitations of the present invention. In the entire drawings, the same reference numerals are used to represent the same components.

[0027] In the attached picture:

[0028] Figure 1 It is a process flow chart of the simulation method of the sand-mud interlayer hydraulic fracturing penetrating interlayer of the present invention.

[0029] Figure 2 It is a three-dimensional constitutive model diagram of elastic-plastic damaged sand-mud interlayers with different interlayer thicknesses established by the present invention.

[0030] Figure 3 It is a schematic diagram of the cohesion crack unit embedded in the model of the present invention. DETAILED DESCRIPTION

[0031] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0032] According to an embodiment of the present application, a simulation method for hydraulic fracturing of sand-mud interlayers penetrating interlayers comprises the following steps:

[0033] S1. Analyze geological parameters of reservoir interlayers; S2. Establish a three-dimensional constitutive model of sand-mud interlayers, divide the grid and set up calculation units; S3. Assign attributes to the unit grid, set initial conditions, boundary conditions and stress conditions, and establish a wellbore model; S4. Change the displacement and viscosity of the sand-mud interlayer constitutive model under different interlayer thicknesses, and establish multiple sets of numerical models under different interlayer thicknesses; S5. Conduct multi-layer extended seepage-stress-damage coupling numerical discrete tests, perform finite element calculations, solve the model and output the results, and obtain the fracture extension results calculated by the model corresponding to different displacements and viscosities under different interlayer thicknesses; S6. Filter out the displacement and viscosity combinations that can penetrate the interlayer from the fracture extension results; compare the fracture morphologies corresponding to different combinations when penetrating the interlayer, and select the optimal displacement and viscosity.

[0034] According to an embodiment of the present application, a method for simulating hydraulic fracturing penetration of a sand-mud interlayer reservoir comprises the following steps:

[0035] (1) Analysis of geological parameters of reservoir barriers: Based on the experimental measurements of the sand-mud interlayer combination of different barrier thicknesses, the density, elastic-plastic parameters, porosity and permeability parameters, and pressure parameters of different layers of rock were obtained (see Tables 1 and 2).

[0036] Table 1. Geological parameter measurement results

[0037]

[0038]

[0039] Table 2. Geological parameter measurement results

[0040]

[0041] (2) According to the distribution of reservoir barriers in the formation, a three-dimensional constitutive model of elastic-plastic damaged sand-mud interlayers with different barrier thicknesses is established, such as Figure 2 According to the formation conditions of the well section, the geometric parameters of the model are determined, the appropriate size is selected for grid division, different types of module calculation units are set, and zero-thickness cohesion fracture units are embedded in the matrix units. Figure 3 .

[0042] (3) Differentiated material properties are assigned to the unit grids of the model. The initial conditions, boundary conditions, and stress conditions of the model are set according to the actual formation conditions. The wellbore model is established, the perforation positions are determined, the wellbore friction is considered, and the mechanical migration damage process of the fracturing fluid from the wellhead to the target formation is simulated.

[0043] (4) The displacement and viscosity of the sand-mud interlayer constitutive model under different interlayer thicknesses were changed respectively. The viscosity was set in four groups (150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s), and the displacement was set in four groups (2m 3 / min、4m 3 / min、6m 3 / min、8m 3 / min), and each interlayer thickness contains 4×4 numerical models.

[0044] (5) Conduct multi-layer expansion seepage-stress-damage coupling numerical discrete tests, run the crack extension simulation software ABAQUS for finite element calculations, solve the model and output the results, and obtain the crack extension results calculated by the model corresponding to different displacements and viscosities under different interlayer thickness conditions. According to the model calculation results, it is judged whether the hydraulic fracture passes through the interlayer. The results are grouped according to the interlayer thickness and plotted into a table, see Table 3-10, and the crack penetration results when the interlayer thickness is 2m, 4m, 6m, 8m, 10m, 12m, 14m, and 16m are statistically calculated. Select the displacement viscosity combination that can penetrate the interlayer under the same interlayer thickness condition, compare the corresponding crack morphology when penetrating the interlayer, and obtain the influence of displacement and viscosity on the length and width of the crack that can penetrate the interlayer.

[0045] Table 3. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of interlayer thickness of 2 m

[0046] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> able able able able <![CDATA[4m 3 / min]]> able able able able <![CDATA[6m 3 / min]]> able able able able <![CDATA[8m 3 / min]]> able able able able

[0047] Table 4. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of 4m interlayer thickness

[0048]

[0049]

[0050] Table 5. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of 6m interlayer thickness

[0051] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> able able able able <![CDATA[4m 3 / min]]> able able able able <![CDATA[6m 3 / min]]> able able able able <![CDATA[8m 3 / min]]> able able able able

[0052] Table 6. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of 8m interlayer thickness

[0053] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> able able able able <![CDATA[4m 3 / min]]> able able able able <![CDATA[6m 3 / min]]> able able able able <![CDATA[8m 3 / min]]> able able able able

[0054] Table 7. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of interlayer thickness of 10m

[0055] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> cannot cannot able able <![CDATA[4m 3 / min]]> cannot able able able <![CDATA[6m 3 / min]]> able able able able <![CDATA[8m 3 / min]]> able able able able

[0056] Table 8. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of interlayer thickness of 12m

[0057] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> cannot cannot cannot able <![CDATA[4m 3 / min]]> cannot cannot cannot able <![CDATA[6m 3 / min]]> cannot cannot able able <![CDATA[8m 3 / min]]> able able able able

[0058] Table 9. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of interlayer thickness of 14m

[0059] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> cannot cannot cannot cannot <![CDATA[4m 3 / min]]> cannot cannot cannot cannot <![CDATA[6m 3 / min]]> cannot cannot cannot cannot <![CDATA[8m 3 / min]]> cannot cannot cannot able

[0060] Table 10. Crack extension results calculated by the model corresponding to different displacement and viscosity under the condition of interlayer thickness of 16m

[0061] Can parameter combinations penetrate layers? 150mPa·s 200mPa·s 250mPa·s 300mPa·s <![CDATA[2m 3 / min]]> cannot cannot cannot cannot <![CDATA[4m 3 / min]]> cannot cannot cannot cannot <![CDATA[6m 3 / min]]> cannot cannot cannot cannot <![CDATA[8m 3 / min]]> cannot cannot cannot cannot

[0062] (6) According to the table obtained in step (5), the displacement viscosity combination that meets the requirements of the on-site fracturing construction is screened out, and the displacement viscosity combination that can penetrate the interlayer under the condition of the same interlayer thickness is selected. The corresponding crack morphologies when different combinations penetrate the interlayer are compared, and the most suitable displacement and viscosity are selected to guide the on-site fracturing design, transform the ideal crack morphology, and achieve the best fracturing penetration effect.

[0063] For example:

[0064] Example 1: The thickness of the interlayer measured during fracturing construction is 12m, but only 6m can be provided on site. 3 / min displacement, according to Table 8, only the viscosity of 250mPa·s or more can pass through the barrier, that is, the displacement of 6m 3 / min, viscosity 250mPa·s, or displacement 6m 3 / min, 300mPa·s. Due to different combinations of displacement and viscosity, the resulting crack morphology is different. Therefore, it is necessary to determine which combination meets the requirements based on the crack length and crack width. Then compare the crack morphology (crack width and crack length) corresponding to the two combinations when they penetrate the interlayer, and determine which of the two combinations is the most suitable based on the crack length and crack width, that is, select the most suitable displacement and viscosity.

[0065] Example 2: During the fracturing operation, the measured interlayer thickness is 10m. The site can only provide a viscosity of 200mPa·s. According to Table 7, only 4m can be selected. 3 / min or more can pass through the partition, that is, you can choose a displacement of 4m 3 / min, viscosity 200mPa·s, or displacement 6m 3 / min, 200mPa·s combination, displacement 8m3 / min, 200mPa·s. Then compare the crack morphology (crack width and crack length) corresponding to the three combinations when penetrating the interlayer, and determine which combination is the most suitable according to the crack length and crack width, that is, select the most suitable displacement and viscosity.

[0066] In summary, in order to clarify the crack expansion law of hydraulic fracturing in sand-mud interlayers and reveal the influence of the displacement and viscosity of the fracturing fluid on the penetration of hydraulic fractures, the present invention provides a finite element-based sand-mud interlayer hydraulic fracturing simulation method, which can accurately predict the penetration effect of hydraulic fractures in sand-mud interlayers under different displacements and viscosities, optimize the displacement and viscosity of the fracturing fluid, and achieve the best construction effect.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. 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 replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation method for hydraulic fracturing of sand-mud interlayers through interlayers, characterized in that: Here are the steps: Measure geological parameters of different layers and different lithologies, and obtain interlayer geological parameter measurement results; According to the measurement results of the interlayer geological parameters, a three-dimensional constitutive model of sand-mud interlayers is established; According to the formation conditions of the well section, geometric parameters are determined from the three-dimensional constitutive model of the sand-mud interlayer, meshing is performed and calculation units are set, and zero-thickness cohesion fracture units are embedded in the calculation units to obtain unit meshes; Changing the displacement and viscosity of the sand-mud interlayer three-dimensional constitutive model under different interlayer thicknesses, establishing multiple sets of numerical models, performing finite element calculations on the multiple sets of numerical models, and obtaining the length and width of cracks that can penetrate the interlayer corresponding to the displacement and viscosity; The geological parameters include at least one of the following parameters: density, elastic-plasticity, porosity, pressure parameter, Young's modulus, Poisson's ratio, permeability, porosity, pore pressure, minimum horizontal principal stress and vertical stress; The establishment of the three-dimensional constitutive model of sand-mud interlayers comprises: establishing a three-dimensional constitutive model of elastic-plastic damaged sand-mud interlayers with different interlayer thicknesses according to the distribution of reservoir interlayers in the formation; The obtaining of the unit grid comprises: performing differentiated material property assignment on the unit grid of the three-dimensional constitutive model of the sand-mud interlayer, setting the initial conditions, boundary conditions and stress conditions of the three-dimensional constitutive model of the sand-mud interlayer to establish a wellbore model simulating the migration process of the fracturing fluid, and after the wellbore model is established, determining the perforation position, considering the wellbore friction, and simulating the mechanical migration damage process of the fracturing fluid from the wellhead to the target formation.

2. The simulation method for hydraulic fracturing of sand-mud interlayers through interlayers according to claim 1, characterized in that: The establishing of multiple groups of numerical models includes: setting m different viscosities, n different displacements, and each interlayer thickness including m×n numerical models.

3. The simulation method for hydraulic fracturing of sand-mud interlayers through interlayers according to claim 2, characterized in that: Whether the hydraulic fracture passes through the interlayer is determined based on the crack extension results calculated by multiple sets of numerical models, and the results are grouped according to the thickness of the interlayer and plotted into a table.

4. The simulation method for hydraulic fracturing of sand-mud interlayers through interlayers according to claim 3, characterized in that: According to the table, the displacement and viscosity combination that meets the requirements of on-site fracturing construction is screened out, and the displacement and viscosity combination that can penetrate the interlayer under the condition of the same interlayer thickness is selected. The corresponding crack morphology when different combinations penetrate the interlayer is compared, and the corresponding displacement and viscosity are selected to determine the crack morphology.

5. A simulation device for hydraulic fracturing of sand-mud interlayers through interlayers, characterized in that: include: The first processing module is suitable for measuring geological parameters of different layers and different lithologies to obtain interlayer geological parameter measurement results; A second processing module is adapted to establish a three-dimensional constitutive model of sand-mud interlayers according to the measurement results of the interlayer geological parameters; A third processing module is adapted to determine geometric parameters from the sand-mud interlayer three-dimensional constitutive model according to the well section formation conditions, perform grid division and set calculation units, and embed zero-thickness cohesion fracture units in the calculation units to obtain unit grids; The fourth processing module is adapted to change the displacement and viscosity of the sand-mud interlayer three-dimensional constitutive model under different interlayer thicknesses, establish multiple sets of numerical models, perform finite element calculations on the multiple sets of numerical models, and obtain the length and width of the cracks that can penetrate the interlayer corresponding to the displacement and viscosity; The geological parameters include at least one of the following parameters: density, elastic-plasticity, porosity, pressure parameter, Young's modulus, Poisson's ratio, permeability, porosity, pore pressure, minimum horizontal principal stress and vertical stress; The establishment of the three-dimensional constitutive model of sand-mud interlayers comprises: establishing a three-dimensional constitutive model of elastic-plastic damaged sand-mud interlayers with different interlayer thicknesses according to the distribution of reservoir interlayers in the formation; The obtaining of the unit grid comprises: performing differentiated material property assignment on the unit grid of the three-dimensional constitutive model of the sand-mud interlayer, setting the initial conditions, boundary conditions and stress conditions of the three-dimensional constitutive model of the sand-mud interlayer to establish a wellbore model simulating the migration process of the fracturing fluid, and after the wellbore model is established, determining the perforation position, considering the wellbore friction, and simulating the mechanical migration damage process of the fracturing fluid from the wellhead to the target formation.

6. A simulation device for hydraulic fracturing of sand-mud interlayers through interlayers, comprising: One or more processors, wherein the processors are configured to execute the method as claimed in any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 4 is performed.

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