Micro-proppant permeability calculation method and system based on correction parameters

Abstract

The invention discloses a micro-proppant permeability calculation method and system based on correction parameters, belongs to the field of proppant permeability evaluation, and considers factors such as micro-proppant concentration, micro-proppant true density, proppant median radius, micro-crack roughness and micro-crack average aperture. The micro-propping agent supported micro-crack area is determined through the micro-propping agent concentration, the micro-propping agent true density, the propping agent median radius and the micro-crack average opening degree, the ratio of the micro-crack communication area to the crack total area is introduced to serve as a correction parameter, the permeability when the micro-propping agent is laid in the crack can be accurately calculated, and a foundation is laid for follow-up digital-analog research. Important parameters are provided for full-scale fracture network refined fracturing sand adding and tight reservoir productivity prediction.

Description

Technical Field

[0001] The present invention belongs to the field of proppant permeability evaluation, and particularly relates to a method and system for calculating the permeability of micro-proppants based on correction parameters. Background Art

[0002] The efficient development of unconventional oil and gas resources has become a hot issue in the energy field of our country. With the continuous exploitation of conventional oil and gas resources and the progress of exploration and development of unconventional oil and gas resources, the proportion of unconventional oil and gas resources production in the total production is also increasing continuously. The efficient development of unconventional oil and gas resources such as tight oil and gas mainly relies on fracturing technology. This technology fractures the formation through low-viscosity slickwater or other media, and the proppants are added into the fractures. After the injection of the fracturing fluid ends, the fractures close and the proppants effectively support the fractures. However, due to the too large particle size or sedimentation of conventional proppants, they cannot migrate to the far end and cannot enter the micro-fractures formed by volume fracturing at all. As a result, after fracturing, the fractures cannot support the entire fracture network. After the hydraulic pressure is removed, a large number of secondary fractures close at the far end of the fracture, greatly reducing the stimulation effect of volume fracturing on tight reservoirs. Field tests show that micro-proppants can support the fracture network and increase production.

[0003] On the other hand, at present, supercritical carbon dioxide fracturing is also a new fracturing method in the future. Supercritical carbon dioxide has great application prospects due to its advantages such as less reservoir damage, carbon sequestration, reduced construction pressure, strong fracture formation ability, methane replacement in gas reservoirs, and reduced crude oil viscosity in oil reservoirs. Its lower viscosity, higher diffusivity, weaker ability to carry proppants, smaller fracture aperture, immature supercritical carbon dioxide thickening technology, and high cost have increased the difficulty of conventional proppant placement. The characteristics of low sedimentation rate and small particle size of micro-proppants can perfectly fit the supercritical carbon dioxide fracturing technology.

[0004] Therefore, whether for the support of micro-fractures and the fracturing application of future supercritical carbon dioxide technology, exploring the seepage mechanism of micro-proppants has very important significance and broad application prospects for unconventional reservoir fracturing technology. However, due to the different placement methods of micro-proppants from conventional proppants, the use concentration is lower than that of conventional proppants, the placement morphology belongs to discrete placement, and the supported fracture width is much lower than that of conventional fractures, it is difficult for the conventional proppant conductivity formula to accurately characterize the conductivity of the fractures supported by micro-proppants. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method and system for calculating the permeability of micro-proppants based on correction parameters, so as to solve the technical problem that it is difficult for the existing technology to accurately characterize the conductivity of the fractures supported by micro-proppants by using the conventional proppant conductivity calculation method.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] A method for calculating the permeability of micro proppants based on correction parameters, comprising the following steps:

[0008] Obtain the micro proppant concentration, the true density of the micro proppant, the median radius of the proppant, and the average aperture of the microfractures, and determine the area of the microfractures supported by the micro proppants;

[0009] Determine the ratio of the connected area of the microfractures to the total area of the fractures according to the area of the microfractures supported by the micro proppants;

[0010] Establish a calculation model for the permeability of micro proppants under microfractures based on the ratio of the connected area of the microfractures to the total area of the fractures;

[0011] Obtain the roughness of the microfractures and the average aperture of the microfractures and input them into the calculation model for the permeability of micro proppants under microfractures to obtain the permeability of the micro proppants.

[0012] Preferably, the ratio of the connected area of the microfractures to the total area of the fractures is calculated by the following formula:

[0013]

[0014] where β is the ratio of the connected area of the microfractures to the total area of the fractures; A P is the area of the microfractures supported by the micro proppants; A f is the total area of the fractures.

[0015] Preferably, the calculation model for the permeability of micro proppants under microfractures is:

[0016]

[0017] where β is the ratio of the connected area of the microfractures to the total area of the fractures; w is the average aperture of the microfractures; δ is the roughness of the microfractures; a and b are model correction coefficients.

[0018] Preferably, the calculation formula for the roughness of the microfractures is:

[0019]

[0020] where δ is the roughness of the microfractures; m is the total length of the abscissa; n is the total length of the ordinate; h ij is the height of the point at the abscissa i and the ordinate j.

[0021] Preferably, the area of the microfractures supported by the micro proppants is calculated by the following formula:

[0022]

[0023] where C PC is the concentration of micro - proppant; w is the average aperture of micro - fractures; A f is the total fracture area; d P50 is the median radius of the proppant; ρ P is the true density of the micro - proppant.

[0024] Preferably, the specific calculation process of the area of micro - proppant - supported micro - fractures includes the following formula:

[0025] The mass m of the micro - proppant P The calculation formula is:

[0026] m p = 1×10 -6 C p wA f

[0027] The volume V of the micro - proppant P The calculation formula is:

[0028]

[0029] The number n of micro - proppants P The calculation formula is:

[0030]

[0031] The area A of micro - proppant - supported micro - fractures P The calculation formula is:

[0032]

[0033] Among them, C P is the concentration of micro - proppant; w is the average aperture of micro - fractures; A f is the total fracture area; d P50 is the median radius of the proppant; ρ P is the true density of the micro - proppant.

[0034] This application also discloses a micro - proppant permeability calculation system based on correction parameters, including:

[0035] An acquisition unit for acquiring the concentration of micro - proppant, the true density of micro - proppant, the median radius of the proppant, and the average aperture of micro - fractures and determining the area of micro - proppant - supported micro - fractures;

[0036] A first calculation unit for determining the ratio of the connected area of micro - fractures to the total fracture area according to the area of micro - proppant - supported micro - fractures;

[0037] A model - building unit for building a micro - proppant permeability calculation model under micro - fractures according to the ratio of the connected area of micro - fractures to the total fracture area;

[0038] A second calculation unit, configured to obtain the microfracture roughness and the average microfracture aperture and input them into a calculation model of the microproppant permeability under the microfracture to obtain the microproppant permeability.

[0039] Preferably, the calculation model of the microproppant permeability under the microfracture established by the model establishment unit is:

[0040] Wherein, β is the ratio of the connected area of the microfracture to the total area of the fracture; w is the average microfracture aperture; δ is the microfracture roughness; a and b are model correction coefficients.

[0041] The present application also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for calculating the microproppant permeability based on the correction parameter as described in any one of the above are implemented.

[0042] The present application also discloses a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the method for calculating the microproppant permeability based on the correction parameter as described in any one of the above are implemented.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention discloses a method for calculating the microproppant permeability based on correction parameters. Considering factors such as the microproppant concentration, the true density of the microproppant, the median radius of the proppant, the microfracture roughness, and the average microfracture aperture, the microproppant-supported microfracture area is determined by the microproppant concentration, the true density of the microproppant, the median radius of the proppant, and the average microfracture aperture. The ratio of the connected area of the microfracture to the total area of the fracture is introduced as a correction parameter, so that the permeability when the microproppant is placed in the fracture can be accurately calculated, providing important parameters for subsequent numerical simulation research, full-scale fracture network fine fracturing and sand addition, and productivity prediction of tight reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a conventional proppant placement morphology diagram;

[0046] Figure 2 is a schematic diagram of the microproppant placement morphology;

[0047] Figure 3 is a comparison diagram of the particle sizes of the conventional proppant and the microproppant;

[0048] Figure 4 is a schematic diagram of the steps of the calculation method of the present invention;

[0049] Figure 5 is a schematic diagram of the three-dimensional data scanning in the embodiment of the present invention. Detailed implementation manners

[0050] In order to enable those skilled in the art of the present technology to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0052] The present invention will be further described in detail below in conjunction with the accompanying drawings:

[0053] Research by domestic and foreign scholars shows that the proppant fracture conductivity is related not only to the proppant type, proppant particle size, sand placement concentration, and closure time, but also to the reservoir rock mechanical properties, fracture roughness, formation pressure, reservoir temperature and other conditions. However, the evaluation method used in the evaluation of the conductivity of conventional proppants is not applicable to the seepage characteristics in microfractures supported by microproppants. To solve the problems such as the difficulty in measuring the thickness after the fracture closure and the inability to determine the permeability of microproppants in the case of discrete placement of microproppants, which bring difficulties to research such as numerical simulation, experiments, and productivity prediction, etc. This application proposes a calculation method for the permeability of microproppants with discrete placement of microproppants.

[0054] Since the placement method of microproppants is different from that of conventional proppants, the placement method of conventional proppants is as Figure 1 shown, and the placement method of microproppants is as Figure 2 shown. Figure 3 Figure for comparing the particle sizes of conventional proppants and microproppants. Conventional proppants fully conform to porous media and Darcy's law can be used for calculation. Due to the smaller particle size, lower placement concentration, and longer migration distance of microproppants, and the fact that microproppants are columnar discrete supports, the support method is different from that of conventional proppants, and the original formula cannot be simply used for calculation and evaluation.

[0055] See Figure 4 , this application discloses a method for calculating the permeability of micro proppants based on correction parameters, including the following steps:

[0056] S1: Obtain the concentration of micro proppants, the true density of micro proppants, the median radius of proppants, and the average aperture of microfractures, and determine the area of microfractures supported by micro proppants;

[0057] S2: Determine the ratio of the connected area of microfractures to the total area of fractures according to the area of microfractures supported by micro proppants;

[0058] S3: Establish a calculation model for the permeability of micro proppants under microfractures according to the ratio of the connected area of microfractures to the total area of fractures;

[0059] S4: Obtain the roughness of microfractures and the average aperture of microfractures and input them into the calculation model for the permeability of micro proppants under microfractures to obtain the permeability of micro proppants.

[0060] Considering factors such as the concentration of micro proppants, the true density of micro proppants, the median radius of proppants, the roughness of microfractures, and the average aperture of microfractures, the area of microfractures supported by micro proppants is determined by the concentration of micro proppants, the true density of micro proppants, the median radius of proppants, and the average aperture of microfractures. The ratio of the connected area of microfractures to the total area of fractures is introduced as a correction parameter, so that the permeability when micro proppants are placed in fractures can be accurately calculated, providing important parameters for subsequent numerical simulation research, full-scale fracture network fine fracturing and sand addition, and productivity prediction of tight reservoirs.

[0061] In some embodiments, the ratio of the connected area of microfractures to the total area of fractures is calculated by the following formula:

[0062]

[0063] where β is the ratio of the connected area of microfractures to the total area of fractures; a P is the area of microfractures supported by micro proppants; a f is the total area of fractures.

[0064] In some embodiments, the calculation model for the permeability of micro proppants under microfractures is:

[0065]

[0066] where β is the ratio of the connected area of microfractures to the total area of fractures; w is the average aperture of microfractures; δ is the roughness of microfractures; a, b are model correction coefficients.

[0067] In some embodiments, the calculation formula for the roughness of microfractures is:

[0068]

[0069] where δ is the roughness of the microfracture; m is the total length of the abscissa; n is the total length of the ordinate; h ij is the height of the point at the abscissa i and ordinate j.

[0070] In some embodiments, the area of the microfracture supported by the microproppant is calculated by the following formula:

[0071]

[0072] where C P is the microproppant concentration; w is the average aperture of the microfracture; A f is the total area of the fracture; d P50 is the median radius of the proppant; ρ P is the true density of the microproppant.

[0073] In some embodiments, the specific calculation process of the area of the microfracture supported by the microproppant includes the following formula:

[0074] The mass m of the microproppant P The calculation formula is:

[0075] m p = 1×10 -6 C p wA f

[0076] The volume V of the microproppant P The calculation formula is:

[0077]

[0078] The number n of microproppants P The calculation formula is:

[0079]

[0080] The area A of the microfracture supported by the microproppant P The calculation formula is:

[0081]

[0082] where C P is the microproppant concentration; w is the average aperture of the microfracture; A f is the total area of the fracture; d P50 is the median radius of the proppant; ρ P is the true density of the microproppant.

[0083] In some embodiments, the technical solution adopted in this application is as follows:

[0084] The fracture permeability under the microfracture can be characterized by the following formula:

[0085]

[0086] Based on this basic formula, a correction coefficient β is proposed, and the final formula is as follows

[0087]

[0088] In the formula: β is the ratio of the connected area of microcracks to the total crack area; w is the average aperture of microcracks, μm;

[0089] δ is the roughness of microcracks; a and b are model correction coefficients.

[0090] Among them, β can be calculated by the following formula:

[0091]

[0092] In the formula:

[0093] C P is the concentration of micro proppants, kg / m 3 ; A is the area of the crack surface, m 2 ; ρ P is the true density of micro proppants, kg / m 3 ; d P50 is the median radius of proppants, μm.

[0094] The mass m of micro proppants P The calculation formula is:

[0095] m p = 1×10 -6 C p wA f

[0096] The volume V of micro proppants P The calculation formula is:

[0097]

[0098] The number n of micro proppants P The calculation formula is:

[0099]

[0100] The area A supported by micro proppants for microcracks P The calculation formula is:

[0101]

[0102] The ratio β of the connected area of microcracks to the total crack area is calculated as:

[0103]

[0104] The calculation formula for the average absolute roughness δ of the microcrack surface is as follows:

[0105]

[0106] In the formula: C P is the microproppant concentration, kg / m 3 ; A f is the fracture surface area, m 2 ; ρ P is the true density of the microproppant, kg / m 3 ; d P50 is the median radius of the microproppant, μm.

[0107]

Example

[0108] 1) Use 3D fracture scanning to obtain fracture parameters as Figure 5 shown;

[0109] 2) Substitute the scanning data into the roughness formula:

[0110] Calculate to obtain δ = 0.6194467231832606;

[0111] The microproppant concentration C P is 65 kg / m 3 ;

[0112] The true density ρ of the microproppant P is 2.65 kg / m 3 ;

[0113] The average aperture w of the microcrack is 91 μm;

[0114] Use a laser particle size analyzer to test that the median radius d of the 200-mesh microproppant as the proppant P50 is 74 μm.

[0115]

[0116]

[0117] Substitute into the formula

[0118]

[0119] Then, according to the verification of the literature and laboratory tests, select:

[0120] The correction parameter a is 1.1;

[0121] The correction coefficient b is -2.26;

[0122] Then the calculation is as follows:

[0123]

[0124] The present invention also discloses a micro - proppant permeability calculation system based on correction parameters, including the following units: An acquisition unit, configured to acquire the micro - proppant concentration, the true density of the micro - proppant, the median radius of the proppant, and the average aperture of the micro - fractures, and determine the area of the micro - fractures supported by the micro - proppant; A first calculation unit, configured to determine the ratio of the connected area of the micro - fractures to the total area of the fractures according to the area of the micro - fractures supported by the micro - proppant; A model establishment unit, configured to establish a micro - proppant permeability calculation model under micro - fractures according to the ratio of the connected area of the micro - fractures to the total area of the fractures; A second calculation unit, configured to acquire the roughness of the micro - fractures and the average aperture of the micro - fractures and input them into the micro - proppant permeability calculation model under micro - fractures to obtain the micro - proppant permeability.

[0129] In some embodiments, the micro - proppant permeability calculation model established by the model establishment unit is:

[0130] where β is the ratio of the connected area of the micro - fractures to the total area of the fractures; w is the average aperture of the micro - fractures; δ is the roughness of the micro - fractures; a and b are model correction coefficients.

[0131] The present invention also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the micro - proppant permeability calculation method based on correction parameters described in any one of the above are implemented.

[0132] The present invention also discloses a computer - readable storage medium. The computer - readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the micro - proppant permeability calculation method based on correction parameters described in any one of the above are implemented.

[0133] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer - usable storage media (including but not limited to disk memories, CD - ROMs, optical memories, etc.) containing computer - usable program codes.

[0134] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or in multiple blocks.

[0135] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or in multiple blocks.

[0136] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operating steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or in multiple blocks.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A method for calculating the permeability of micro proppants based on correction parameters, characterized in that, it includes the following steps: Obtain the micro proppant concentration, true density of micro proppants, median radius of proppants, and average aperture of microfractures, and determine the area of microfractures supported by micro proppants; Determine the ratio of the connected area of microfractures to the total fracture area based on the area of microfractures supported by micro proppants; Establish a calculation model for the permeability of micro proppants under microfractures based on the ratio of the connected area of microfractures to the total fracture area; Obtain the microfracture roughness and average aperture of microfractures and input them into the calculation model for the permeability of micro proppants under microfractures to obtain the permeability of micro proppants.

2. The method for calculating the permeability of micro proppants based on correction parameters according to claim 1, characterized in that, the ratio of the connected area of microfractures to the total fracture area is calculated by the following formula: Among them, β is the ratio of the connected area of microcracks to the total area of cracks; A P is the area of the microfracture supported by the microproppant; A f is the total area of the cracks.

3. The method for calculating the permeability of micro proppants based on correction parameters according to claim 1, characterized in that, the calculation model for the permeability of micro proppants under microfractures is: where β is the ratio of the connected area of microfractures to the total fracture area; w is the average aperture of microfractures; δ is the microfracture roughness; a and b are model correction coefficients.

4. The method for calculating the permeability of micro proppants based on correction parameters according to claim 3, characterized in that, the calculation formula for the microfracture roughness is: where δ is the roughness of microcracks; m is the total length of the abscissa; n is the total length of the ordinate; h ij is the height of the point at the abscissa i and ordinate j.

5. The method for calculating the permeability of micro proppants based on correction parameters according to claim 1, characterized in that, the area of microfractures supported by micro proppants is calculated by the following formula: Among them, C P is the concentration of micro proppant; w is the average aperture of microfractures; A f is the total fracture area; d P50 is the median radius of the proppant; ρ P is the true density of the micro proppant.

6. The method for calculating the permeability of micro proppants based on correction parameters according to claim 1, characterized in that, the specific calculation process of the area of microfractures supported by micro proppants includes the following formula: Micro proppant mass m P The calculation formula is as follows: m p = 1 × 10 -6 C p wA f Micro proppant volume V P The calculation formula is as follows: The number of micro proppants n P The calculation formula is as follows: Micro proppant-supported microfracture area A P The calculation formula is as follows: Among them, C P is the micro - proppant concentration; w is the average aperture of the micro - fractures; A f is the total fracture area; d P50 is the median radius of the proppant; ρ P is the true density of the micro - proppant.

7. A system for calculating the permeability of micro proppants based on correction parameters, characterized in that, it includes: An acquisition unit for obtaining the micro proppant concentration, true density of micro proppants, median radius of proppants, and average aperture of microfractures, and determining the area of microfractures supported by micro proppants; A first calculation unit for determining the ratio of the connected area of microfractures to the total fracture area based on the area of microfractures supported by micro proppants; A model establishment unit for establishing a calculation model for the permeability of micro proppants under microfractures based on the ratio of the connected area of microfractures to the total fracture area; A second calculation unit for obtaining the microfracture roughness and average aperture of microfractures and inputting them into the calculation model for the permeability of micro proppants under microfractures to obtain the permeability of micro proppants.

8. The system for calculating the permeability of micro proppants based on correction parameters according to claim 7, characterized in that, the calculation model for the permeability of micro proppants under microfractures established by the model establishment unit is: where β is the ratio of the connected area of microfractures to the total fracture area; w is the average aperture of microfractures; δ is the microfracture roughness; a and b are model correction coefficients.

9. An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method for calculating the permeability of micro proppants based on correction parameters according to any one of claims 1-6.

10. A computer-readable storage medium storing a computer program, which when executed by a processor, implements the steps of the method for calculating the permeability of microproppants based on correction parameters according to any one of claims 1-6.

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