Preparation method and application of artificial core with adaptive mechanical properties

Abstract

The present invention relates to a preparation method and application of an artificial core with adapted mechanical properties. Aiming at the loose, high porosity and low stress characteristics of deepwater high-temperature and high-pressure reservoir rocks and the problems of preparing artificial cores, the present invention configures the amount of artificial core rock mineral binder components and particle size, optimizes the binder, and conducts orthogonal design experimental tests to explore the preparation conditions, forming a preparation method for artificial cores for deepwater high-temperature and high-pressure reservoirs based on the principle of "same components, consistent particle size, similar porosity and permeability, and mechanical equivalence", and analyzes its mechanical characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a preparation method and application of an artificial core with adaptive mechanical properties. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Underground cores are the only original specimens of strata and are the first-hand data for understanding and studying stratum conditions and fluid properties. They are the key to calculating oilfield reserves, selecting drilling and production techniques, and rationally formulating development plans. It is particularly important to prepare artificial cores that can accurately simulate reservoir lithology and physical properties, which is of great significance to the efficient development of deepwater oil and gas resources.

[0004] At present, artificial cores are mostly prepared by simulating formation porosity and permeability and conducting displacement experiments. The methods and ideas are mainly concentrated in two aspects: one is to adjust the particle size composition to adapt to the formation permeability; the other is to optimize the amount of binder and pressing conditions to control the porosity. However, how to prepare artificial cores that adapt to the mechanical properties of the formation is still a blank area. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for preparing artificial cores for deepwater high-temperature and high-pressure reservoirs with adapted mechanical properties and its application. Aiming at the loose, high-porosity and low-stress characteristics of deepwater high-temperature and high-pressure reservoir rocks and the problems of preparing artificial cores, the present invention configures the amount and particle size of the artificial core rock and mineral binder components, optimizes the binder, and conducts orthogonal design experimental tests to explore the preparation conditions, forming a method for preparing artificial cores for deepwater high-temperature and high-pressure reservoirs based on the principle of "same components, consistent particle size, similar porosity and permeability, and mechanical equivalence", and analyzes its mechanical characteristics.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing an artificial core with adapted mechanical properties comprises the following steps:

[0008] ① According to the content of rock minerals and clay minerals in natural core fragments, artificial core rock minerals and clay minerals are configured;

[0009] ② Based on the same natural core particle size parameters d10, d40, d50, d90, and d95, the proportion of quartz sand with different particle sizes is adjusted according to the core particle size composition of the target formation;

[0010] ③Select appropriate cementing agent for artificial core;

[0011] ④ Orthogonal design of three factors and three levels to prepare artificial cores; the three factors are the amount of cementing agent, pressing pressure and pressing time; the three levels are to set three representative levels for each factor on the basis of the trial production conditions of porosity and permeability and wave velocity close to the reservoir rock performance;

[0012] ⑤ Test the pore permeability and acoustic wave velocity of artificial cores, and use the range method to analyze the sensitivity of the three factors. The sensitivity of the three factors is used as the basis for adjusting the preparation conditions of artificial cores;

[0013] ⑥ According to the orthogonal experimental results in ④ and the sensitivity of the three factors in ⑤, select and adjust a certain compression condition close to the actual rock properties of the reservoir and actually prepare artificial cores to test the porosity and sonic wave velocity;

[0014] ⑦ Compare the test results of the artificial core with the porosity and permeability of the actual reservoir rock and the acoustic wave velocity (logging or experimental characterization). If the porosity and permeability are within 85% of the probability distribution and the acoustic wave velocity error is <15%, then the preparation conditions are appropriate. Otherwise, repeat steps ⑥⑦.

[0015] Furthermore, the binder is epoxy resin and curing agent.

[0016] Further, the dosage range of the binder is:

[0017] The ratio of epoxy resin glue: curing agent: mineral raw material is 1:1:10 to 1:1:20;

[0018] Pressing pressure level: 5-15MPa;

[0019] Pressing time level: 10-30min.

[0020] Furthermore, the usage ratio of the binder, curing agent and quartz sand is 1:1:16.

[0021] Furthermore, a core mold and a jack are used to prepare the artificial core.

[0022] Furthermore, the mineral raw materials and the binder are mixed evenly, put into a core mold, pre-compacted manually with a pressure rod, and then assembled with a special hydraulic instrument for precise pressing to apply pressure.

[0023] The artificial core with suitable mechanical properties can be prepared by the above preparation method. The artificial core with suitable mechanical properties is used for the study of mechanical properties of deepwater reservoir rocks.

[0024] At present, the simulation of the target formation by artificial core mainly focuses on the matching of physical parameters. In the study of target formations with complex geological conditions, the temperature and pressure effects may change the mechanical properties of the formation rocks. The artificial core that only matches the physical parameters has limited use and is difficult to meet the test requirements of formations with complex conditions. Therefore, in addition to porosity and permeability, the present invention introduces the core acoustic wave velocity as a means of evaluating the mechanical properties of artificial cores, and takes the core acoustic wave longitudinal wave velocity as an indicator of the mechanical properties of artificial cores.

[0025] Since the acoustic properties of rocks are affected and controlled by many factors, when conditions change, the acoustic time difference obtained from the same lithology may be different, so there is a difference between the acoustic velocity value obtained from the core surface indoor test and the underground acoustic velocity obtained by logging. Therefore, it is necessary to use an empirical model to convert the underground acoustic velocity of well logging into the surface acoustic velocity. The regression model for converting the formation logging acoustic longitudinal wave velocity to the surface acoustic longitudinal wave velocity is as follows:

[0026] V p =0.004AC 1.6378

[0027] Where Vp is the surface acoustic wave longitudinal wave velocity, m / s; AC is the logging acoustic wave longitudinal wave velocity, m / s.

[0028] In the process of making artificial cores, the pressing conditions mainly include three factors: the amount of binder, pressure, and time. In order to control the matching indexes of artificial cores and simulate the actual formation properties, a three-factor three-level artificial core trial orthogonal test was conducted to test the influence of each factor on each matching index.

[0029] The present invention found that the order of influence on permeability is pressure>time>binder dosage; for acoustic wave velocity, the order of influence of various factors on acoustic wave velocity is binder dosage>pressure>time. According to the influence of various factors of pressing conditions on the matching index of artificial core, the pressing conditions can be adjusted in a targeted manner to effectively control the matching of artificial core.

[0030] At present, the commonly used artificial core binders are aluminum phosphate binders and epoxy resin binders. The binders are optimized from three aspects: binder preparation, core production characteristics, and experimental repeatability.

[0031] (1) Preparation of binder

[0032] The preparation conditions of aluminum phosphate binder are relatively complicated and need to be prepared immediately under high temperature conditions before making the core. Epoxy resin binder only needs to mix epoxy resin glue and curing agent and stir them, and then mix them with mineral raw materials to make artificial core.

[0033] (2) Core production characteristics

[0034] Aluminum phosphate binder has good bonding strength and stability, which is beneficial to improving the success rate of making large cores. The sintering temperature of aluminum phosphate binder can be as high as 1300℃, and it has the characteristics of high temperature resistance. The use of epoxy resin binder is convenient for controlling the physical properties of artificial cores, which is beneficial to matching the physical properties of artificial cores.

[0035] (3) Experimental repeatability

[0036] The artificial core samples made with epoxy resin binder have uniform density and size, good experimental repeatability, and are suitable for situations where a large number of artificial cores need to be made.

[0037] Beneficial effects of the present invention:

[0038] The artificial core preparation method provided by the present invention introduces the core acoustic wave velocity as a means of evaluating the mechanical properties of the artificial core, and takes the core acoustic wave longitudinal wave velocity as an index of the mechanical properties of the artificial core, so as to obtain an artificial core with adapted mechanical properties. Through orthogonal experiments, the effects of the three factors of the pressing conditions, namely, the amount of binder, pressure, and time, on the permeability and acoustic wave velocity and the sensitivity of each factor to the permeability and acoustic wave velocity are studied, so that each factor can be effectively adjusted to obtain an artificial core with matching physical parameters and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0040] Figure 1 This is the particle size distribution diagram of the N layer section of Well X in Example 1.

[0041] Figure 2 A pressing device for preparing artificial cores.

[0042] Figure 3 It is the trend of core permeability, porosity and acoustic velocity with the factor level.

[0043] Figure 4 is the stress-strain curve of the artificial core. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0045] The present invention will be further described below in conjunction with the embodiments and drawings, but the scope of the present invention is not limited in any way.

[0046] Example 1: Preparation of artificial core for a deepwater high-temperature and high-pressure gas field reservoir

[0047] The basic data of a deepwater high-temperature and high-pressure gas field reservoir are obtained. The specific data are as follows.

[0048] 1.1 Skeleton sand particle size

[0049] The formation grain size distribution of Well X is shown in Table 1:

[0050] Table 1 Formation particle size distribution of Well X

[0051]

[0052] The particle size distribution of the well is plotted using the particle size mean, such as Figure 1 As shown. In the particle size distribution diagram, points are taken to determine the mesh ratio of quartz sand as shown in Table 2:

[0053] Table 2 Artificial core quartz sand particle size ratio

[0054]

[0055] 1.2 Mineral components

[0056] The mineral composition of Group N in Well X is shown in Table 3:

[0057] Table 3 Mineral composition of group N in well X

[0058]

[0059] Based on the formation mineral content data, the mineral content of each layer section per 50g of artificial core is calculated as shown in Table 4 below.

[0060] Table 4 Mineral content of artificial core

[0061]

[0062] 1.3 Target formation physical properties and acoustic wave velocity parameters

[0063] The porosity, permeability range and surface acoustic wave velocity parameters of the Nshan Formation in Well X are shown in Table 5:

[0064] Table 5 Porosity and acoustic velocity parameters of group N

[0065]

[0066] 1.4 Optimal binder selection

[0067] The highest temperature of the target formation of Group N of Well X is 131.30℃, and the formation pressure coefficient is 1.74. The geological conditions of high temperature, high pressure and low stress promote the enhancement of the plasticity of the formation rock. In order to study the rock mechanical properties of the target formation, it is necessary to make an artificial core for rock triaxial compression test. The optimal bonding temperature range of epoxy resin is 0-180℃, which is suitable for the target formation temperature, and the margin between its upper limit of bonding temperature and the target formation temperature is large, which can meet the setting of higher temperature level of subsequent triaxial test. Due to the large number of core matching indicators, epoxy resin that can better simulate the porosity and permeability characteristics is preferred, which is conducive to the adjustment of compression conditions during the trial production process. Considering that the triaxial test needs to consider the three factors of temperature, confining pressure and pore pressure at the same time, the demand for the number of artificial cores is large, and epoxy resin also has certain advantages in experimental repeatability. Combining the characteristics of the target formation and the characteristics of the binder, the present invention preferably uses epoxy resin as the binder of the artificial core of Group N of Well X.

[0068] 1.5 Artificial core preparation tools

[0069] Artificial core pressing tools such as Figure 2 As shown, it is mainly composed of a core mold and a jack. The mineral raw materials are mixed evenly with quartz sand and epoxy resin binder in a good ratio, put into the core mold, manually compacted with a pressure rod in advance, and then assembled with a special hydraulic instrument for precise pressing for pressurization.

[0070] 2.1 Sensitivity analysis of core compression conditions

[0071] In the process of making artificial cores, the pressing conditions mainly include three factors: the amount of binder, pressure, and time. In order to control the matching indexes of artificial cores and simulate the actual formation properties, a three-factor three-level artificial core trial orthogonal test was conducted to test the influence of each factor on each matching index. The test results are shown in Table 6.

[0072] Table 6 Sensitivity analysis of core compression conditions

[0073]

[0074] In Table 6, A is the amount of binder, B is the pressure, and C is the time; k i is the average value of the test results of the corresponding factor i level; R = max{k i}-min{k i As shown in Table 6, for porosity, the range values ​​R of the three factors are R B >R A >R C , that is, the order of influence of each factor on porosity is pressure > binder dosage > time; for permeability, the magnitude of the range value R of the three factors is R B >R C >RA , that is, the order of influence on permeability is pressure>time>binder dosage; for the acoustic wave velocity, the magnitude of the range value R of the three factors is R A >R B >R C That is, the order of influence of various factors on the acoustic wave velocity is binder dosage>pressure>time.

[0075] The influence trend of the three factors on the matching index is as follows Figure 3 According to the influence of various factors of pressing conditions on the matching index of artificial core, the pressing conditions can be adjusted in a targeted manner to effectively control the matching of artificial core.

[0076] 3.1 Pressing conditions

[0077] (1) Pressing conditions ①

[0078] Amount of binder: epoxy resin: curing agent: mineral raw material = 1:1:15;

[0079] Pressing pressure: 10MPa;

[0080] Pressing time: 15mins;

[0081] Drying conditions: 70℃, 6h.

[0082] The artificial core was trial-produced using the pressing condition ①. The acoustic wave test results of samples 1-1 and 1-2 are shown in Table 7:

[0083] Table 7 Sonic wave test results of artificial core samples 1-1 and 1-2

[0084]

[0085] (2) Suppression conditions ②

[0086] According to the acoustic wave test results of samples 1-1 and 1-2, the longitudinal wave velocity is too large, and the amount of binder or the pressing pressure can be appropriately reduced. This pressing condition attempts to appropriately reduce the pressing pressure by 2MPa.

[0087] Amount of binder: epoxy resin: curing agent: mineral raw material = 1:1:15;

[0088] Pressing pressure: 8MPa;

[0089] Pressing time: 15mins;

[0090] Drying conditions: 70℃, 6h.

[0091] The results of the sonic test of artificial core samples 3-1 and 3-2 are shown in Table 8:

[0092] Table 8 Sonic wave test results of artificial core samples 2-1 and 2-2

[0093]

[0094] (3) Suppression conditions ③

[0095] According to the acoustic test results of samples 2-1 and 2-2, the longitudinal wave velocity is closer to the surface acoustic wave velocity converted from well logging, but it is still too large. Since the effect of adjusting the suppression pressure is not obvious and the suppression pressure is already too small, this suppression chooses to reduce the amount of binder appropriately to observe the production effect.

[0096] Amount of binder: epoxy resin: curing agent: mineral raw material = 1:1:16;

[0097] Pressing pressure: 8MPa;

[0098] Pressing time: 15mins;

[0099] Drying conditions: 70℃, 6h.

[0100] The results of the sonic test of artificial core samples 3-1 and 3-2 are shown in Table 9:

[0101] Table 9 Acoustic wave test results of artificial core samples 3-1 and 3-2

[0102]

[0103] The error of the acoustic wave velocity test results of the artificial core samples made by this scheme is within 10%, so epoxy resin: curing agent: mineral raw material = 1:1:16 and pressing pressure 8MPa are selected as the amount of binder and pressing pressure. The porosity and permeability matching test results of artificial core samples 3-1 and 3-2 are shown in Tables 10 and 11.

[0104] Table 10 Porosity test results of artificial core samples 3-1 and 3-2

[0105]

[0106] Table 11 Permeability test results of artificial core samples 3-1 and 3-2

[0107]

[0108] The permeability of artificial core samples 3-1 and 3-2 is low, and the permeability of one of them is not within the range of formation permeability. Since the porosity of samples 3-1 and 3-2 has met the requirements, according to the influence of the above-mentioned pressing conditions on porosity and permeability, the pressing time has a greater impact on permeability and a smaller impact on porosity. Consider shortening the pressing time by 5 minutes to improve the permeability of the artificial core.

[0109] Artificial core samples 4-1 and 4-2 were produced using pressing condition ④.

[0110] Amount of binder: epoxy resin: curing agent: mineral raw material = 1:1:16;

[0111] Pressing pressure: 8MPa;

[0112] Pressing time: 10mins;

[0113] Drying conditions: 70℃, 6h.

[0114] The artificial core samples 4-1 and 4-2 were subjected to acoustic wave, porosity and permeability matching tests, and the results are shown in Tables 12, 13 and 14.

[0115] Table 12 Test results of acoustic wave velocity of artificial core samples 4-1 and 4-2

[0116]

[0117] Table 13 Porosity test results of artificial core samples 4-1 and 4-2

[0118]

[0119] Table 14 Permeability test results of artificial core samples 4-1 and 4-2

[0120]

[0121] The acoustic wave velocity, porosity and permeability parameters of artificial core samples 4-1 and 4-2 all match the formation parameters. Therefore, the pressing condition ④ is a feasible condition for making artificial cores in high-temperature and high-pressure formations.

[0122] 4.1 Artificial core matching test

[0123] Six artificial cores were made, and all cores were tested for porosity, permeability and sonic wave to verify matching.

[0124] (1) Porosity test

[0125] The porosity test results of the six artificial cores are shown in Table 15. The core porosities are all within the range of formation parameters and match well.

[0126] Table 15 Artificial core porosity test results and formation porosity data

[0127]

[0128] (2) Permeability test

[0129] The permeability test results of the six artificial cores are shown in Table 16. The core permeabilities are all within the range of formation parameters and are well matched.

[0130] Table 16 Artificial core permeability test results and formation permeability data

[0131]

[0132]

[0133] (3) Test of acoustic wave mechanical properties of artificial core

[0134] The test results of the acoustic wave velocity of 6 artificial cores are shown in Table 17. The error between the acoustic wave velocity of the artificial core and the acoustic wave velocity of the ground is basically within 10%, and the acoustic wave mechanical properties match well.

[0135] Table 17 Acoustic mechanical test results

[0136]

[0137] 4.2 Uniaxial compression experiment of artificial rock core in deep water at high temperature and high pressure

[0138] A piece of artificial core with matching performance that meets the requirements was selected for uniaxial compression test to verify the matching effect of the core mechanical properties. The stress-strain curve is shown in Figure 4 The uniaxial compressive strength of the artificial core is 35.54MPa, which is close to the compressive strength of the actual rock in the formation, 38.86MPa. The results show that the artificial core of the deepwater, high-temperature and high-pressure formation made by this method has a good match with the mechanical properties of the actual formation rock.

[0139] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an artificial core with adapted mechanical properties, characterized in that: The steps include: ① According to the content of rock minerals and clay minerals in drilling cuttings or natural core fragments, configure the mineral composition of artificial core; ② According to the core particle size composition of the target formation, the proportion of quartz sand with different particle sizes is adjusted; ③Select appropriate cementing agent for artificial core; ④ Orthogonal design of three factors and three levels to prepare artificial cores; the three factors are the amount of cementing agent, pressing pressure and pressing time; the three levels are to set three representative levels for each factor on the basis of the trial production conditions of porosity and permeability and wave velocity close to the reservoir rock performance; ⑤ Test the pore permeability and acoustic wave velocity of artificial cores, and use the range method to analyze the sensitivity of the three factors. The sensitivity of the three factors is used as the basis for adjusting the preparation conditions of artificial cores; ⑥ According to the orthogonal experimental results in ④ and the sensitivity of the three factors in ⑤, a certain pressing condition is selected and adjusted, and an artificial core is actually prepared to test the pore permeability and acoustic wave velocity; ⑦ Compare the test results of the artificial core with the porosity and permeability of the actual reservoir rock and the acoustic wave velocity. If the porosity and permeability are within 85% of the probability distribution and the acoustic wave velocity error is <15%, then the preparation conditions are appropriate. Otherwise, repeat steps ⑥⑦.

2. The preparation method according to claim 1, characterized in that: The binder is epoxy resin and curing agent.

3. The preparation method according to claim 2, characterized in that: The usage ratio of epoxy resin, curing agent and mineral raw material is 1:1:10 to 1:1:

20.

4. The preparation method according to claim 1, characterized in that: Pressing pressure level: 5-15MPa; Pressing time level: 10-30min.

5. The preparation method according to claim 1, characterized in that: The dosage ratio of the binder, curing agent and quartz sand is 1:1:

16.

6. The preparation method according to claim 1, characterized in that: When preparing artificial cores, core molds and jacks are used.

7. The preparation method according to claim 6, characterized in that: The mineral raw materials and binder are mixed evenly, placed in a core mold, pre-compacted manually with a pressure rod, and then pressurized with a special hydraulic instrument for precise pressing.

8. The preparation method according to claim 1, characterized in that: Based on the same particle sizes of d10, d40, d50, d90 and d95, the proportions of quartz sands of different particle sizes are adjusted according to the particle size composition of the target formation core.

9. An artificial core with adapted mechanical properties is prepared by the preparation method according to any one of the above claims.

10. Application of the artificial core with adapted mechanical properties according to claim 9 in the study of mechanical properties of deepwater reservoir rocks.

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