A method for making loose sand artificial core by using drill cuttings

Abstract

The application provides a method for manufacturing loose sandstone artificial core by using drill cuttings, and steps include: obtaining oil reservoir geological data, analyzing mineral components and content of target reservoir; obtaining particle size composition of target reservoir core according to the oil reservoir geological data; obtaining target reservoir drill cuttings, first drying the drill cuttings, then adding 3wt% KCl solution and toluene / methanol solution with a volume ratio of 1:1 to stir and clean, and pouring out the upper suspension after standing; after drying the drill cuttings to constant weight, screening and mixing the drill cuttings, and analyzing the mineral components and content of the mixed drill cuttings; adding simulated formation water to wet the drill cuttings and the inner wall of the steel sleeve, and finally loading and pressing the artificial core. The artificial loose sandstone core prepared by the method has stable properties, can retain the original components of the natural core and the occurrence state of the natural clay minerals, and has a permeability and porosity closer to the natural core of the target reservoir, so that the indoor physical experiment related to the loose sandstone reservoir can be better carried out.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas field development, and particularly relates to a method for manufacturing loose sandstone artificial core by using drill cuttings. BACKGROUND

[0002] In the research of oil exploration and production process, the core is a common reservoir porous medium model in the indoor physical simulation experiment, and the analysis result of the core flow experiment is an effective reference basis for solving many actual problems of oilfields. Generally, the indoor physical simulation experiment is used to study the oil recovery mechanism, reservoir damage mechanism, remaining oil distribution and evaluate the development effect in the displacement or imbibition process. However, for the special loose sandstone reservoir, the loose sandstone has low cementation degree, loose structure and small strength, the coring cost is high and difficult to form on site, and most natural cores cannot meet the experimental requirements, so the artificial core needs to be used in most indoor physical simulation experiments.

[0003] At present, the commonly used artificial core manufacturing methods include quartz filling, aluminum phosphate quartz sand cementation and epoxy resin river sand cementation. However, the temperature in the core sintering process is high, which usually damages the original components of the core, and there are problems such as clay mineral denaturation. Moreover, the adhesive easily wraps the surface of the clay mineral, so that the displacement medium cannot contact the clay mineral in the laboratory permeation simulation experiment using the artificial core, the clay mineral does not hydrate, swell, disperse, migrate and other physical and chemical reactions, which leads to the experimental result not meeting the actual situation of the reservoir rock. In addition, the artificial core manufactured by the general combination of quartz sand and clay minerals cannot simulate the real reservoir mineral environment, so it cannot accurately study the problems such as yield increase or reservoir damage caused by the interaction between the injected medium and various rock minerals in the actual production process.

[0004] Therefore, it is urgent to provide a loose sandstone artificial core manufacturing method which can overcome the defects of the prior art, can simulate the space and material conditions of the reservoir porous medium to the greatest extent, and meet the needs of the indoor reservoir permeation simulation experiment. SUMMARY

[0005] The present application aims to solve the defects of the prior art, and provides a method for manufacturing loose sandstone artificial core by using drill cuttings, which solves the problems such as the small number of natural cores of loose sandstone reservoir in the indoor physical simulation experiment, the inability of the existing artificial core manufacturing method to simulate the real reservoir porous medium space and material conditions, and the like. Moreover, the artificial loose sandstone core prepared by the method has stable properties, and the permeability and porosity and other physical properties are more close to the natural core of the target reservoir, which can better carry out the indoor physical experiment related to the loose sandstone reservoir.

[0006] The present application adopts the following technical solutions:

[0007] A method for making loose sandstone artificial core by using drill cuttings, comprising the following steps:

[0008] (1) Obtain oil reservoir geological data, analyze the mineral composition and mass percentage of the target reservoir;

[0009] (2) According to the oil reservoir geological data in (1), analyze the particle size composition of the target reservoir core;

[0010] (3) Obtain the target reservoir drill cuttings from the drilling site, place the reservoir drill cuttings in a constant temperature oven for 1h, dry the excess water, and the oven temperature should be set to the reservoir temperature; mix 3wt% KCl solution with drill cuttings at a mass ratio of 2:1, mechanically stir for 30-60min at a stirring speed of 100-500rpm, stand for 3min after stirring, then slowly pour out the upper suspension to remove the drilling mud (mainly including bentonite, dispersing agent and other components) mixed in the drill cuttings, repeat the above cleaning step three times, then filter out the drill cuttings and dry them in an oven;

[0011] (4) Mix the toluene / methanol solution with a volume ratio of 1:1 with the drill cuttings cleaned in step (3) at a mass ratio of 2:1, mechanically stir for 10-30min at a stirring speed of 100-500rpm, stand for 3min after stirring, then slowly pour out the upper suspension to remove the residual oil and inorganic salts in the drill cuttings, repeat the above cleaning step twice; then add methanol solution to cover the upper part of the drill cuttings, seal and soak for 24h until the color is colorless, then screen out the drill cuttings;

[0012] (5) After the drill cuttings separated in step (4) are dried to a constant weight in a constant temperature and humidity oven, the oven temperature should be set to the actual reservoir temperature, and the oven humidity should be set to 40%-50%;

[0013] (6) According to the particle size composition analysis results of the reservoir core, screen drill cuttings of different particle size ranges for standby; according to the particle size composition of the target reservoir core, mix the drill cuttings of different particle size ranges uniformly at a certain proportion;

[0014] (7) Analyze the types and contents of minerals contained in the mixed drill cuttings, and compare them with the types and mass percentages of minerals contained in the reservoir core, to determine whether they meet the conditions for making artificial core;

[0015] (8) Add an appropriate amount of simulated formation water of the target reservoir to wet the mixed drill cuttings and the steel sleeve inner wall, which not only improves the cementation degree of the core, but also has a good pore throat preservation effect;

[0016] (9) Assemble the mold and tighten the bolts to fix the mold; place the mold vertically below the artificial core making device, first place the bottom solid pad on the bottom of the mold, the bottom solid pad is cylindrical and completely fits the bottom of the steel sleeve; the diameter of the bottom solid pad is the same as the outer diameter of the steel sleeve;

[0017] (10) Place the steel sleeve on the bottom solid pad in the mold, the outer diameter of the steel sleeve is the same as the inner diameter of the mold; weigh an appropriate amount of drill cuttings and pour into the steel sleeve, gently shake the side of the steel sleeve during pouring to make the drill cuttings overflow the upper end surface of the steel sleeve;

[0018] (11) Place the upper solid pad above the drill cuttings, the upper solid pad is cylindrical and the diameter of the protruding part is the same as the inner diameter of the steel sleeve;

[0019] (12) Close the pressure relief valve of the artificial core making device, open the switch of the artificial core making device, place the mold on the artificial core making device, and pressurize to make the artificial core; set a certain pressure, and the hydraulic machine extrudes the upper solid pad downward, and after the pressure is stable, continue to press for a certain time;

[0020] (13) Open the pressure relief valve of the artificial core making device, remove the mold bolts, open the mold, and take out the steel sleeve;

[0021] (14) Block the two ends of the steel sleeve with a screen and then fix it with a compression ring;

[0022] (15) Place the artificial core in a constant temperature oven and bake for 6 hours, then take out the artificial core after the oven cools to room temperature, and the temperature of the oven should be adjusted to the actual reservoir temperature;

[0023] (16) The artificial core making is completed.

[0024] Preferably, the drill cuttings are water-based drilling fluid drill cuttings returned during drilling.

[0025] Preferably, the steel sleeve is a hollow cylindrical sleeve, the outer diameter of the steel sleeve is 3.8 cm, the inner diameter is 2.5 cm, the wall thickness is 0.6 cm, and the length of the steel sleeve is 5 cm (generally, the core length required for physical experiments is at least about 1.5 times the diameter to reduce errors caused during experiments); the diameter of the screen is 3.8 cm.

[0026] Preferably, the mesh number of the drill cuttings is less than the mesh number of the screen.

[0027] Preferably, the mesh number of the drill cuttings is 30-200 mesh, and the mesh number of the screen is 220 mesh.

[0028] Preferably, the compression ring is an aluminum compression ring.

[0029] Preferably, the drill cuttings for making the artificial core are screened according to the particle size composition of the reservoir core to ensure that the artificial core simulates the pore throat space of the real reservoir, and the porosity and permeability and other properties are closer to the natural core of the reservoir.

[0030] Preferably, in step (10), the appropriate amount of drill cuttings is 42-52 g.

[0031] Preferably, in step (12), the pressing pressure for making the artificial core is 8-12 MPa, and the pressing time is 5-7 min.

[0032] Preferably, the inner wall of the steel sleeve is inertly treated so as not to react with any one or several of the simulated formation water, crude oil or injection medium under the formation temperature and pressure, which affects the seepage experiment results. The inert treatment includes plating or coating treatment on the inner wall of the steel sleeve, so that the steel sleeve does not have acid etching or other reactions with any one or several of the simulated formation water, crude oil or injection medium under the formation temperature and pressure, which affects the seepage experiment results.

[0033] Advantages of the present application:

[0034] (1) The method for making the loose sandstone artificial core provided by the present application considers the influence of the particle size of the drill cuttings in addition to the mineral composition, and after the drill cuttings are wetted by the formation water, not only the pore throat is well maintained, but also the cementation degree of the artificial core is improved, and the artificial core manufactured by the present application has low price, good repeatability and high success rate.

[0035] (2) The artificial core manufactured by the present application fully considers the composition and particle size distribution of the minerals, and the artificial core does not use a cementing agent and is pressed at room temperature, so that the original components and the occurrence state of the natural clay minerals of the natural core are retained, the clay minerals are not wrapped by the cementing agent, and the accuracy of the experimental results is affected. Therefore, the artificial core provided by the present application not only can simulate the mineral composition of the reservoir rock, but also can simulate the mineral particle size distribution of the reservoir rock, greatly simulates the space and mineral conditions of the porous medium of the reservoir, truly realizes the simulation of the reservoir conditions, and meets the basic needs of the reservoir seepage simulation experiment. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is the particle size distribution curve of the core minerals in the oil reservoir target reservoir provided by the embodiment;

[0037] Figure 2 is a structural schematic view of the artificial core of the present application;

[0038] Figure 3 is a schematic view of the artificial core mold and the manufacturing process of the present application;

[0039] Figure 4 This is a flowchart illustrating the preparation process of the present invention.

[0040] In the diagram: 1-Pressure ring, 2-Screen, 3-Drill cuttings, 4-Steel sleeve, 5-Hydraulic press, 6-Mold bolt, 7-Upper solid pad, 8-Mold, 9-Bottom solid pad, 10-Artificial core. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Example:

[0043] like Figure 4 As shown, a method for preparing artificial cores of loose sandstone using drill cuttings includes the following steps:

[0044] (1) Obtaining geological data of the reservoir: Based on the analysis of core samples, cuttings logging, well logging, and rock and mineral data from a certain oilfield in the Bohai Sea, the target reservoir encountered a thickness of 200m-370m. The thickness of a single sandstone layer is generally 0.5m-11.9m. The main lithology of the reservoir is fine sandstone, medium-fine sandstone, and gravelly medium-coarse sandstone. The cement is mainly argillaceous and carbonate. The reservoir rocks are loosely cemented with good physical properties. The porosity is 22.2%-34.0%, with a weighted average of 28.0%, and the permeability is 2-2400mD, with a weighted average of 437mD, exhibiting the characteristics of medium porosity and medium permeability for oil storage. First, X-ray diffraction whole-rock analysis and laser grain size analysis were performed on the core samples of the target strata to analyze the mineral composition and mineral grain size of the target reservoir. The analysis results are shown in Table 1 and Figure 1 As shown in Table 1, the mineral types and their mass percentages in the reservoir are statistically significant. Table 1 shows that the minerals in the reservoir include quartz, potassium feldspar, plagioclase, and clay minerals. Quartz accounts for 55.7% of the total mass, making it the main constituent mineral of the reservoir.

[0045] Table 1:

[0046] Mineral name Quartz Potassium feldspar Plagioclase Clay minerals Mass fraction / % 55.7 16.0 17.9 10.4

[0047] (2) Based on the geological data of the reservoir, analyze Figure 1 Grain size distribution curves of minerals in intermediate reservoir cores, from Figure 1 It can be seen that the grain size of the minerals in this reservoir is mainly distributed between 0.4 and 1124.7 μm.Figure 1 The particle size distribution curve reading determines the median particle size of the reservoir minerals and the mass content of different particle size ranges, wherein the mineral content of 30-60 mesh (600-250 μm) is 40% of the total mass of the reservoir minerals, the mineral content of 60-120 mesh (250-125 μm) is 50% of the total mass of the reservoir minerals, and the mineral content of 120-200 mesh (125-75 μm) is 10% of the total mass of the reservoir minerals.

[0048] (3) The reservoir drill cuttings are placed in a constant temperature oven at 65°C for 1 h; then 500 g of the drill cuttings are weighed and mixed with 1000 g of a 3wt% KCl solution, mechanical stirring is performed for 30 min at a stirring speed of 200 rpm, after the stirring is completed, the mixture is allowed to stand for 3 min, then the upper suspension is slowly poured out to remove the drilling mud (mainly including bentonite, dispersing agent and other components) doped in the drill cuttings, and the above cleaning step is repeated three times; then the drill cuttings are filtered and dried.

[0049] (4) 480 g of the drill cuttings cleaned in step (3) are weighed and mixed with 960 g of a toluene / methanol solution, then mechanical stirring is performed for 20 min at a stirring speed of 200 rpm, after the stirring is completed, the mixture is allowed to stand for 3 min, then the upper suspension is slowly poured out to remove the residual oil and inorganic salt doped in the drill cuttings, and the above cleaning step is repeated twice; then methanol solution is added to cover the upper part of the drill cuttings, and the mixture is sealed for immersion, after 24 h of colorless immersion, the drill cuttings are screened out;

[0050] (5) The drill cuttings separated in step (4) are dried in a constant temperature and humidity oven at a constant temperature of 65°C and a constant humidity of 45% until the weight is constant, and then the drill cuttings are taken out;

[0051] (6) According to the particle size composition analysis result of the reservoir core in step (2), drill cuttings of 30-60 mesh (600-250 μm), 60-120 mesh (250-125 μm) and 120-200 mesh (125-75 μm) are screened for standby use; according to the mass fraction under each particle size condition, the drill cuttings of the three particle size ranges are mixed uniformly at a mass ratio of 4:5:1;

[0052] (7) The types and mass percentages of the minerals contained in the mixed and uniform drill cuttings are analyzed, as shown in Table 2, the types and mass percentages of the minerals contained in the drill cuttings are very similar to those contained in the reservoir core, which meets the conditions for making artificial cores, then the inner wall of the steel sleeve is plated and polished to prevent various reactions with the simulated formation water, crude oil or injection medium under the temperature and pressure of the formation, and to prevent the accuracy of the percolation experiment results from being affected.

[0053] Table 2

[0054] Mineral name Quartz Potassium feldspar Plagioclase Clay minerals Mass fraction / % 56 10.7 24.2 9.1

[0055] (8) Add a suitable amount of simulated formation water of the target reservoir to wet the mixed uniform drilling cuttings particles and the inner wall of the steel sleeve, improve the cementation degree of the prepared core, and obtain a better pore throat retention effect;

[0056] (9) Assemble the mold 8, buckle the two half-cylindrical molds, align the clamping eyes, and tighten the mold bolts 6 to fix the mold; the mold 8 is an existing device;

[0057] As shown in Figure 3 (10) Place the mold 8 vertically below the artificial core preparation device, first place the bottom solid pad 9 at the bottom of the mold 8, the bottom solid pad 9 is cylindrical and completely fits the bottom of the steel sleeve 4; the diameter of the bottom solid pad 9 is the same as the outer diameter of the steel sleeve 4;

[0058] (11) Place the steel sleeve 4 on the bottom solid pad 9 in the mold 8, the outer diameter of the steel sleeve 4 is the same as the inner diameter of the mold 8; weigh an appropriate amount of drilling cuttings 3 and pour it into the steel sleeve 4, gently shake and compact during pouring, so that the drilling cuttings 3 are above the upper end surface of the steel sleeve 4;

[0059] (12) Place the upper solid pad 7 above the drilling cuttings 3, the upper solid pad 7 is cylindrical, the diameter of the protruding part is the same as the inner diameter of the steel sleeve 4, and the length of the protruding part is slightly longer than the length of the steel sleeve 4;

[0060] (13) Turn on the artificial core preparation device switch and close the artificial core preparation device pressure relief valve, place the mold 8 on the artificial core preparation device, and pressurize to prepare the artificial core; set a certain pressure, and the hydraulic machine 5 extrudes the upper solid pad 7 downward to compact the drilling cuttings 3; after the pressure stabilizes, continue to press for a certain period of time, as shown in Figure 2 ;

[0061] (14) Open the pressure relief valve of the artificial core preparation device, remove the mold bolts 6, open the mold 8, and take out the steel sleeve 4;

[0062] (15) Place the screen 2 at both ends of the steel sleeve 4, and then put on the pressing ring 1 to fix it to prevent the screen 2 from falling off;

[0063] (16) Place the artificial core 10 in a 65°C constant temperature oven and bake for 6h, then cool the oven to room temperature and take out the artificial core;

[0064] (17) The artificial core preparation is completed.

[0065] Preferably, the drilling cuttings are water-based drilling fluid cuttings returned during drilling.

[0066] Preferably, the steel sleeve 4 is a hollow cylindrical sleeve, the outer diameter of the steel sleeve 4 is 3.8 cm, the inner diameter is 2.5 cm, the wall thickness is 0.6 cm, and the length of the steel sleeve 4 is 5 cm (generally, the core length required by the core physical experiment is at least about 1.5 times the diameter, so as to reduce the error caused in the experiment process); the screen 2 has a diameter of 3.8 cm, and the mesh number of the screen 2 is 220 meshes. The pressing ring 1 is an aluminum pressing ring.

[0067] Preferably, the drill cuttings used to make the artificial core are screened according to the particle size composition of the reservoir core, so as to ensure that the artificial core simulates the pore throat space of the real reservoir, and the porosity and permeability and other properties are closer to the natural core of the reservoir.

[0068] Preferably, in step (11), the appropriate amount of drill cuttings is 42-50 g.

[0069] Preferably, in step (13), the pressing pressure for making the artificial core is 8-12 MPa, and the pressing time is 5-7 min.

[0070] The artificial core made by the method has consistent mineral composition and particle size composition with the reservoir rock, similar porosity, permeability and other properties, small fluctuation, and good reproducibility.

[0071] Table 3 is a table of artificial core making test data

[0072]

[0073] As can be seen from Table 3, the drill cuttings used are taken from the target reservoir L50 layer, and the flow zone index (FZI) of the four artificial cores is calculated as 3.63, 3.60, 3.27 and 3.29 respectively, the permeability differential is 1.2, the fluctuation is very small, the dynamic physical properties of the four artificial cores are similar, the seepage experiment process has similar fluid flow behavior, and the method is feasible and has high reproducibility.

[0074] Table 4 is a table of basic physical property data of natural cores, and the flow zone index (FZI) of the three natural cores is calculated as 3.70, 3.73 and 3.71 respectively. By comparing the porosity, permeability and flow zone index (FZI) data in Table 3 and Table 4, it can be found that the basic physical properties and dynamic physical parameters of the artificial core and the natural core are relatively small, and the similarity between the two is good, which shows that the artificial core made according to the specification can simulate the natural core to a large extent, and can meet the needs of indoor physical experiments.

[0075] Table 4 is a table of basic physical property data of natural cores

[0076]

[0077] This research was jointly supported by the National Natural Science Foundation of China for Young Scientists (Grant No. 52104040) and the Science and Technology Program of Sichuan Province (Grant No. 2022YFSY0007).

[0078] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art will understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing artificial rock cores from loose sandstone using drill cuttings, characterized in that, Includes the following steps: Step (1). Obtain reservoir geological data and analyze the mineral composition and mass percentage of the target reservoir; Step (2). Based on the reservoir geological data from step (1), analyze and obtain the grain size composition of the target reservoir core. Step (3). Obtain the target reservoir cuttings from the drilling site, place the reservoir cuttings in a constant temperature oven and bake for 1 hour to dry excess moisture. The temperature of the oven is set to the reservoir temperature. Mix 3wt% KCl solution with the cuttings at a mass ratio of 2:1 and mechanically stir for 30-60 minutes at a stirring speed of 100-500 rpm. After stirring, let stand for 3 minutes, and then slowly pour out the upper suspension to remove drilling mud mixed in the cuttings. Repeat the washing 3 times, then filter out the cuttings and place them in an oven to dry. Step (4). Mix the toluene / methanol solution with the drill cuttings cleaned in step (3) at a mass ratio of 2:1 and mechanically stir for 10-30 minutes at a stirring speed of 100-500 rpm. After stirring, let it stand for 3 minutes, then slowly pour out the upper suspension to remove residual oil and inorganic salts from the drill cuttings. Repeat the washing process twice. Then add methanol solution to cover the upper part of the drill cuttings and seal and soak them. After soaking for 24 hours until the solution is colorless, sieve out the drill cuttings. Step (5). The drill cuttings separated in step (4) are dried to constant weight in a constant temperature and humidity oven and then removed. The temperature of the oven is set to the actual reservoir temperature, and the humidity of the oven is set to 40%-50%. Step (6). Based on the grain size composition analysis results of the reservoir core, select drill cuttings of different grain size ranges for use. According to the grain size composition of the target reservoir core, mix the drill cuttings of different grain size ranges evenly in a certain proportion. Step (7). Analyze the types and contents of minerals contained in the mixed drill cuttings, and compare them with the types and mass percentages of minerals contained in the reservoir core to determine whether they meet the conditions for making artificial cores. Step (8). Add an appropriate amount of simulated formation water from the target reservoir to wet the uniformly mixed drill cuttings and the inner wall of the steel casing. Step (9). Assemble the mold and tighten the bolts to fix the mold; place the mold vertically under the artificial core making device, first place a solid bottom pad at the bottom of the mold, the solid bottom pad is cylindrical and fits completely with the bottom of the steel sleeve; the diameter of the solid bottom pad is the same as the outer diameter of the steel sleeve; Step (10). Place a steel sleeve on the solid pad at the bottom of the mold. The outer diameter of the steel sleeve is the same as the inner diameter of the mold. Weigh an appropriate amount of drill chips and pour them into the steel sleeve. During the pouring process, gently tap the side of the steel sleeve so that the drill chips cover the upper end of the steel sleeve. Step (11). Place an upper solid pad above the drill cuttings. The upper solid pad is cylindrical, and the diameter of the lower part of the upper solid pad is the same as the inner diameter of the steel sleeve. Step (12). Close the pressure relief valve of the artificial rock core making device, open the switch of the artificial rock core making device, place the mold on the artificial rock core making device, and pressurize to make the artificial rock core; set a certain pressure, and use the hydraulic press to squeeze the upper solid pad block downward. After the pressure stabilizes, continue to press for a certain period of time. The pressing pressure for making the artificial rock core is 8MPa-12MPa, and the pressing time is 5min-7min. Step (13). Open the pressure relief valve of the artificial core making device, remove the mold bolts, open the mold, and take out the steel sleeve; Step (14). Plug both ends of the steel sleeve with a screen, and then put on the pressure ring to fix it; Step (15). Place the artificial core in a constant temperature oven and bake for 6 hours. After the oven cools to room temperature, take out the artificial core. The temperature of the oven should be adjusted to the actual reservoir temperature. Step (16). The artificial rock core is now complete.

2. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, The drill cuttings are water-based drilling fluid cuttings that are returned during the drilling process.

3. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, In step (14), the steel sleeve is a hollow cylindrical sleeve with an outer diameter of 3.8cm, an inner diameter of 2.5cm, a wall thickness of 0.6cm, a length of 5cm, and a screen diameter of 3.8cm.

4. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, The mesh size of the drill cuttings is smaller than that of the sieve.

5. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, The drill cuttings have a mesh size of 30-200; in step (14), the screen mesh size is 220.

6. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, In step (14), the pressure ring is an aluminum pressure ring.

7. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, In step (10), the appropriate amount of drill cuttings weighs 42-50g.

8. The method for preparing artificial cores of loose sandstone using drill cuttings according to claim 1, characterized in that, The inner wall of the steel sleeve is inertized, and the inertization treatment includes plating or coating the inner wall of the steel sleeve.

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