A method for evaluating the conductivity of quartz sand proppants with different particle size combinations

Abstract

The present invention discloses a method for evaluating the conductivity of quartz sand proppants with different particle size combinations, belonging to the field of unconventional oil and gas fracturing and production technology. The method comprises the following steps: providing a shale rock sample and quartz sand proppant samples with different particle size combinations; fracturing the shale rock sample to obtain a shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the shale rock sample with cracks; embedding the quartz sand proppant samples with different particle size combinations into the shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the quartz sand proppant samples embedded with different particle size combinations; establishing a sample-permeability curve based on the sample permeability results, and evaluating the conductivity of the quartz sand proppant with different particle size combinations based on the permeability in the curve. The entire evaluation method of the present invention is simple, efficient, and convenient for large-scale application.

Description

Technical Field

[0001] The invention belongs to the technical field of unconventional oil and gas fracturing and production, and particularly relates to a method for evaluating the conductivity of quartz sand proppants under different particle size combinations. Background Art

[0002] During hydraulic fracturing of oil and gas resources, proppant plays a crucial role influencing production efficiency. The higher the proppant's conductivity, the better the migration of oil and gas resources within the fractures. Proppant conductivity is influenced by factors such as particle size, fragmentation rate, acid solubility, and porosity, with particle size being the primary factor. Proppant with the appropriate particle size is not only the minimum requirement for hydraulic fracturing but also a higher standard pursued by oil companies for profitability. Unlike conventional oil and gas resources, hydraulic fracturing of shale reservoirs requires proppants of comparable particle size and higher strength.

[0003] Currently, during hydraulic fracturing of oil and gas resources, at least two proppants with different particle sizes are combined to improve extraction efficiency. The conductivity of these combined proppants is traditionally measured using the industry standard SYT6302-2019, "Test Method for Conductivity of Fracturing Proppants."

[0004] However, the testing methods in the prior art have technical problems such as complicated steps, long time consumption, large amount of sample mass required, and the lack of close integration between laboratory test results and actual production. Summary of the Invention

[0005] The present invention aims to provide a method for evaluating the conductivity of quartz sand proppants with different particle size combinations. This method addresses technical issues with existing proppant conductivity measurement methods, such as cumbersome procedures, time-consuming processes, the large amount of sample mass required, and the lack of close integration between laboratory test results and actual production.

[0006] In a first aspect, the present invention provides a method for evaluating the conductivity of quartz sand proppants with different particle size combinations, comprising the following steps: providing a shale rock sample and quartz sand proppant samples with different particle size combinations, respectively; fracturing the shale rock sample to obtain a shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the shale rock sample with cracks; embedding the quartz sand proppant samples with different particle size combinations into the shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the quartz sand proppant samples embedded with different particle size combinations; establishing a sample-permeability curve based on the permeability results of the sample, and evaluating the conductivity of the quartz sand proppants with different particle size combinations based on the permeability in the curve.

[0007] In the present invention, the inventors have discovered that the use of fracturing technology to create fractures can simulate the natural fractures of oil wells hydraulically fractured under formation pressure at a certain depth, solving the technical problem that the test results of traditional laboratory tests are not closely integrated with actual production, making the experimental results more accurate and reliable; in addition, according to Darcy's law, the present invention only needs to test the permeability of quartz sand proppant samples with different particle size combinations to obtain the size of the conductivity of quartz sand proppant samples with different particle size combinations, and the entire evaluation method is simple and efficient, and is convenient for large-scale application.

[0008] In some embodiments, the shale rock sample comprises a shale core column.

[0009] In some embodiments, the quartz sand proppant samples of different particle size combinations include quartz sand proppant samples of 30 / 50 mesh, 40 / 70 mesh, 60 / 120 mesh, 70 / 140 mesh, and 100 / 200 mesh combinations.

[0010] In the present invention, quartz sand proppant samples with other different particle size combinations can also be selected according to actual test needs. In the present invention, quartz sand proppant samples with 30 / 50 mesh, 40 / 70 mesh, 60 / 120 mesh, 70 / 140 mesh and 100 / 200 mesh combinations are preferred.

[0011] In some embodiments, the quartz sand proppant samples with different particle size combinations are obtained by scrubbing, grinding, and screening quartz sand and then combining them according to the method in the industry standard SY / T 5108-2014 "Test Method for Proppant Performance for Hydraulic Fracturing and Gravel Packing Operations".

[0012] In some embodiments, during the permeability test of a shale rock sample with cracks, before the shale rock sample is fractured, a step of drying the fractured shale rock sample is also included; wherein the drying step specifically includes: drying for 24 to 48 hours, for example, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours or other values ​​within the range, at a temperature of 60 to 80°C (for example, 60°C, 65°C, 70°C, 75°C, 80°C or other values ​​within the range).

[0013] In some embodiments, during the permeability testing of a shale rock sample having fractures, the fracturing specifically includes: using a rock triaxial system (PDP-200) for fracturing to obtain a shale rock sample having fractures; wherein the fractures are natural fractures hydraulically fractured under formation pressure simulating an oil well depth of 1800 to 2200 m (for example, 1800 m, 1900 m, 2000 m, 2100 m, 2200 m or other values ​​within this range).

[0014] In the present invention, by using a rock triaxial system for fracturing and creating fractures, it is possible to simulate the hydraulic fracturing of natural fractures in an oil well under formation pressure at a certain depth. Further, when quartz sand proppant samples with different particle size combinations are embedded in the natural fractures for testing, the conductivity of the quartz sand proppant samples with different particle size combinations in actual application can be reflected.

[0015] In some embodiments, the permeability test specifically includes: using an overburden porosity and permeability tester to perform a test at a pressure of 18-22 MPa (for example, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa or other values ​​within the range).

[0016] In the present invention, when using the overburden porosity and permeability tester for testing, it has the advantages of simple method and high accuracy.

[0017] In some embodiments, during the permeability test of quartz sand proppant samples embedded with different particle size combinations, before the quartz sand proppant samples with different particle size combinations are respectively embedded in shale rock samples with fractures, the step of drying the quartz sand proppant samples with different particle size combinations is also included; wherein the drying step specifically includes: drying for 24 to 48 hours, for example, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 ​​hours or other values ​​within the range, at a temperature of 60 to 80°C (for example, 60°C, 65°C, 70°C, 75°C, 80°C or other values ​​within the range).

[0018] In some embodiments, during the permeability testing process of quartz sand proppant samples embedded with different particle size combinations, the permeability test specifically includes: using an overburden porosity and permeability tester to perform the test at a pressure of 18 to 22 MPa (for example, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, or other values ​​within this range).

[0019] In some embodiments, in evaluating the conductivity of silica sand proppants of different particle size combinations, the conductivity is directly proportional to the permeability.

[0020] In the present invention, according to Darcy's law, the conductivity is directly proportional to the permeability. Therefore, by simply testing the permeability of quartz sand proppants with different particle size combinations, the conductivity of quartz sand proppants with different particle size combinations can be quickly, simply and efficiently obtained.

[0021] The beneficial effects of the present invention are as follows: unlike the prior art, the present invention uses fracturing technology to create fractures, which can simulate the natural fractures of oil wells hydraulically fractured under formation pressure at a certain depth, solving the technical problem that the test results of traditional laboratory tests on quartz sand proppants are not closely integrated with actual production, making the experimental results more accurate and reliable; in addition, according to Darcy's law, the present invention only needs to test the permeability of quartz sand proppant samples with different particle size combinations to obtain the size of the conductivity of quartz sand proppant samples with different particle size combinations, and the entire evaluation method is simple and efficient, and is convenient for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of the method for evaluating the conductivity of quartz sand proppants with different particle size combinations in the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a shale core column sample after fracturing in the present invention;

[0024] Figure 3 Schematic diagram of the structure of quartz sand proppant embedded in the shale core column after fracturing in the present invention;

[0025] Figure 4 The graphs are sample-permeability curves of shale rock samples with fractures and quartz sand proppant samples embedded with different particle size combinations in the present invention;

[0026] In the figure, the meanings of the reference numerals are as follows: 1: shale core column; 2: natural fracture; 3: quartz sand proppant. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 making creative efforts are within the scope of protection of the present invention.

[0028] For experimental methods in the examples where specific conditions are not specified, generally conventional conditions and conditions described in the manual or conditions recommended by the manufacturer were followed. The general equipment, materials, reagents, etc. used were all commercially available unless otherwise specified.

[0029] See also Figure 1, which is a flow chart of the method for evaluating the conductivity of quartz sand proppants with different particle size combinations in the present invention. Specifically, the method includes the following steps: providing shale rock samples and quartz sand proppant samples with different particle size combinations respectively; fracturing the shale rock samples to obtain shale rock samples with cracks, and then performing a permeability test to obtain the permeability of the shale rock samples with cracks; embedding the quartz sand proppant samples with different particle size combinations into the shale rock samples with cracks, and then performing a permeability test to obtain the permeabilities of the quartz sand proppant samples embedded with different particle size combinations; establishing a sample-permeability curve based on the permeability results of the samples, and evaluating the conductivity of the quartz sand proppants with different particle size combinations based on the permeability in the curve.

[0030] Please continue reading Figure 2 and 3 ,in, Figure 2 Schematic diagram of the structure of a shale core column 1 sample after fracturing in the present invention. After fracturing, the shale core column 1 obtains natural cracks 2. Figure 3 Schematic diagram of the structure of the quartz sand proppant 3 embedded in the shale core column 1 after fracturing in the present invention.

[0031] Example 1

[0032] A method for evaluating the conductivity of quartz sand proppants with different particle size combinations comprises the following steps:

[0033] S1. Provide shale rock samples and quartz sand proppant samples with different particle size combinations;

[0034] S2. fracturing the shale rock sample to obtain a shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the shale rock sample with cracks;

[0035] S3. Embedding quartz sand proppant samples with different particle size combinations into shale rock samples with fractures, and then performing permeability tests to obtain the permeabilities of the quartz sand proppant samples embedded with the different particle size combinations;

[0036] S4. Based on the permeability results of the samples, a sample-permeability curve is established, and the conductivity of quartz sand proppants with different particle size combinations is evaluated based on the permeability in the curve.

[0037] For example, the conductivity of silica sand proppant samples with 30 / 50 mesh, 40 / 70 mesh, 60 / 120 mesh, 70 / 140 mesh, and 100 / 200 mesh combinations was evaluated.

[0038] Specifically, the steps include:

[0039] S1. Select a shale core column 1 sample, scrub, grind, and sieve quartz sand, and then combine it according to the method in the industry standard SY / T5108-2014 "Test Method for Proppant Performance for Hydraulic Fracturing and Gravel Packing Operations" to obtain quartz sand proppant samples with 30 / 50 mesh, 40 / 70 mesh, 60 / 120 mesh, 70 / 140 mesh, and 100 / 200 mesh combinations;

[0040] S2. The shale core column 1 sample in step S1 is dried at 70° C. for 36 hours, and then fractured using a rock triaxial system to obtain a shale rock sample having natural fractures 2 simulated by hydraulic fracturing at a formation pressure of 2000 m at a depth of an oil well. Then, a permeability test is performed using an overburden porosity and permeability tester at a pressure of 20 MPa to obtain the permeability of the shale rock sample;

[0041] S3, drying the 30 / 50 mesh quartz sand proppant sample in step S1 at a temperature of 70°C for 36 hours, and then embedding it into the natural crack 2 of the shale rock sample in step S2, and using an overburden porosity and permeability tester to perform a permeability test at a pressure of 20 MPa to obtain the permeability of the embedded 30 / 50 mesh quartz sand proppant sample; taking out the 30 / 50 mesh quartz sand proppant sample from the natural crack 2 of the shale rock sample, and then at a temperature of 70°C, The shale rock sample was dried for 36 hours, and the quartz sand proppant sample with a 40 / 70 mesh combination in step S1 was continuously embedded into the natural fracture 2 of the dried shale rock sample. The permeability of the quartz sand proppant sample embedded with a 40 / 70 mesh combination was measured using the above method. Similarly, the permeability of the quartz sand proppant sample embedded with a 60 / 120 mesh combination, the permeability of the quartz sand proppant sample embedded with a 70 / 140 mesh combination, and the permeability of the quartz sand proppant sample embedded with a 100 / 200 mesh combination were obtained respectively.

[0042] The permeability results of the samples in steps S2 and S3 are shown in Table 1 below:

[0043] Table 1 Permeability results of samples (test repeated 3 times)

[0044]

[0045] S4. Based on the permeability results of the samples in steps S2 and S3, a sample-permeability curve (e.g. Figure 4 The conductivity of quartz sand proppants with different particle size combinations was evaluated based on the permeability in the curve.

[0046] from Figure 4As can be seen from the figure, compared to rock samples with only fractures, rock samples embedded with quartz sand proppants have higher permeability. As the proppant particle size increases, the permeability increases. When the proppant particle size reaches 70 / 140 mesh, the permeability changes tend to be stable. Furthermore, according to Darcy's law, the conductivity of quartz sand proppants is proportional to their permeability. Therefore, the permeability of quartz sand proppants with different particle size combinations can be used to determine their conductivity.

[0047] Further, from Figure 4 As can be seen from the figure, a 30 / 50 mesh quartz sand proppant combination has the highest permeability and the strongest conductivity. However, when using quartz sand proppant in actual shale reservoir oil and gas resource extraction, while maintaining high permeability, the particle size of the quartz sand proppant must also be considered. Generally, the smaller the particle size, the better. Therefore, the 70 / 140 mesh quartz sand proppant combination selected in the present invention has the best effect when used in actual shale reservoir oil and gas resource extraction.

[0048] In summary, the present invention only needs to test the permeability of quartz sand proppant samples with different particle size combinations to obtain the conductivity of quartz sand proppant samples with different particle size combinations. In addition, the entire evaluation method is simple, efficient, and convenient for large-scale application.

[0049] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0050] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for evaluating the conductivity of quartz sand proppants with different particle size combinations, characterized in that: The steps include: Provide shale rock samples and quartz sand proppant samples with different particle size combinations; Fracturing the shale rock sample to obtain a shale rock sample with cracks, and then performing a permeability test to obtain the permeability of the shale rock sample with cracks; The quartz sand proppant samples with different particle size combinations are respectively embedded in the shale rock sample with fractures, and then a permeability test is performed to obtain the permeabilities of the quartz sand proppant samples embedded with different particle size combinations; Based on the permeability results of the samples, a sample-permeability curve was established, and the conductivity of quartz sand proppants with different particle size combinations was evaluated based on the permeability in the curve.

2. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: The shale rock sample includes a shale core column.

3. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: The quartz sand proppant samples with different particle size combinations include quartz sand proppant samples with 30 / 50 mesh, 40 / 70 mesh, 60 / 120 mesh, 70 / 140 mesh and 100 / 200 mesh combinations.

4. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: In the process of testing the permeability of the shale rock sample with cracks, before fracturing the shale rock sample, the step of drying the shale rock sample is also included; The drying step specifically includes: drying at a temperature of 60-80° C. for 24-48 hours.

5. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: In the permeability test process of the shale rock sample with fractures, the fracturing specifically includes: fracturing the shale rock sample with fractures using a rock triaxial system; The cracks are natural cracks simulated by hydraulic fracturing under formation pressure at a depth of 1800 to 2200 meters in an oil well.

6. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, characterized in that: The permeability test specifically includes: using an overburden porosity and permeability tester to conduct the test at a pressure of 18~22MPa.

7. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: During the permeability test of the quartz sand proppant samples embedded with different particle size combinations, before the quartz sand proppant samples with different particle size combinations are respectively embedded in the shale rock samples with fractures, the method further includes drying the quartz sand proppant samples with different particle size combinations; The drying step specifically includes: drying at a temperature of 60-80° C. for 24-48 hours.

8. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: In the permeability test process of the quartz sand proppant samples embedded with different particle size combinations, the permeability test specifically includes: using an overburden porosity and permeability tester to perform the test at a pressure of 18-22 MPa.

9. The method for evaluating the conductivity of quartz sand proppants with different particle size combinations according to claim 1, wherein: In the process of evaluating the flow conductivity of quartz sand proppants with different particle size combinations, the flow conductivity is proportional to the permeability.

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