Fractured-vuggy carbonate rock composition and application thereof

Abstract

The invention provides a fractured-vuggy carbonate rock composition and application thereof. The fractured-vuggy carbonate rock composition comprises sulphoaluminate cement; the sulphoaluminate cement is prepared from anhydrous calcium sulphoaluminate, dicalcium silicate, tetra calcium aluminoferrite and gypsum. The fractured-vuggy carbonate rock composition provided by the invention can be used for preparing fractured-vuggy carbonate rocks, and the fractured-vuggy carbonate rocks prepared by adjusting the component proportion can realize setting of different mechanical parameters, so that the fractured-vuggy carbonate rocks are approximately equivalent to the mechanical properties of real stratum rocks.

Description

Technical Field

[0001] The present invention relates to the field of rock sample preparation, and particularly to a fracture-vug type carbonate rock composition and its application. Background Art

[0002] Carbonate rock formations generally have the characteristics of a wide distribution range and a stable sedimentary thickness, and are very important sedimentary rock oil and gas reservoirs. Carbonate reservoirs usually have well-developed fractures and pores. The minerals filled inside the fractures and pores are mostly calcite and quartz. The pore permeability is strong. Generally, acidification, acid fracturing and other transformation measures need to be carried out to establish an oil and gas channel with the reservoir body to obtain industrial oil and gas flow. The main principle of acid fracturing technology is to pump acid fracturing fluid with a high H + concentration into the formation through surface equipment, so that H + reacts with calcite and dolomite in the formation. After dissolution, the insoluble mineral particles and special etching structures (grooves, tunnels) are left in the fractures. On this basis, the fracture surface will form self-support, providing a more favorable flow channel for oil and gas.

[0003] In previous studies, natural outcrops were mostly used as the carbonate rock matrix for hydraulic fracturing to analyze the initiation and propagation laws of artificial fractures. However, carbonate reservoirs are often accompanied by the co-development of fractures and pores, and the oil and gas resources in such fracture-vug bodies are relatively rich. Therefore, it is more important to study the interaction between artificial fractures and natural fractures and pores. It is extremely difficult to obtain natural outcrops or downhole cores with natural fractures and pores, mainly for two reasons. One is that brittle failure or fracture often occurs during the collection process, and an integral research sample cannot be formed. The second is that the development of natural fractures and pores is random, and quantitative and standardized repeated research cannot be carried out to obtain accurate research data.

[0004] To solve the above problems, artificial carbonate rock is proposed as a low-cost and effective analysis method. In the existing methods for artificial carbonate rock, rock powder is mainly cemented with a cementing agent (epoxy resin) to achieve diagenesis. The cemented rock powder has a certain mechanical strength. However, as a non-reactive material, epoxy resin does not participate in the acid fracturing experiment process, and its preparation process is relatively cumbersome. The mechanical properties of the prepared artificial rock samples are quite different from those of natural rocks themselves. Summary of the Invention

[0005] The present invention provides a fracture-vug type carbonate rock composition, which can be used to prepare fracture-vug type artificial carbonate rock, and the fracture-vug type carbonate rock prepared by adjusting the component ratio can achieve different mechanical parameter settings, making it approximately equivalent to the mechanical properties of real formation carbonate rock.

[0006] The present invention also provides a method for preparing a simulated sample of a fractured-vuggy carbonate reservoir. The simulated sample of the fractured-vuggy carbonate reservoir prepared by this preparation method can be applied to the analysis of the stimulation of carbonate reservoirs, providing a feasible indoor simulation means for the reservoir stimulation technology in oil and gas engineering.

[0007] The present invention also provides a physical simulation sample of a fractured-vuggy carbonate reservoir composed of the above-mentioned fractured-vuggy carbonate composition or prepared by the above-mentioned preparation method for studying the propagation pattern, extension, and acidification law of acid fracturing of fractures in a fractured-vuggy carbonate reservoir.

[0008] In a first aspect, the present invention provides a fractured-vuggy carbonate composition, comprising sulfoaluminate cement; the sulfoaluminate cement comprises anhydrous calcium sulfoaluminate, dicalcium silicate, tetracalcium aluminoferrite, and gypsum.

[0009] In an optional embodiment, it further comprises carbonate rock powder.

[0010] In an optional embodiment, the carbonate rock powder comprises a first particle with a mesh number of 30-50 and a second particle with a mesh number of 700-800.

[0011] In an optional embodiment, the carbonate rock powder comprises calcite and / or dolomite.

[0012] In an optional embodiment, based on a total mass of 100 parts, the sulfoaluminate cement comprises 75-82 parts of anhydrous calcium sulfoaluminate, 6-10 parts of dicalcium silicate, 7-10 parts of tetracalcium aluminoferrite, and 4-5 parts of gypsum;

[0013] And / or, the gypsum comprises calcium sulfate dihydrate.

[0014] In an optional embodiment, in the fractured-vuggy carbonate composition, the mass ratio of the sulfoaluminate cement is not less than 40%.

[0015] In an optional embodiment, in the carbonate rock powder, the mass ratio of the first particle is not less than 50%.

[0016] In a second aspect, the present invention provides a method for preparing a simulated sample of a fractured-vuggy carbonate reservoir, comprising the following steps:

[0017] Step 1: Select a target area and obtain a test sample of a natural outcrop or formation core;

[0018] Step 2: Select the base material ratio for preparing the simulated sample of the fractured-vuggy carbonate reservoir according to the density of the test sample, wherein the base material comprises the fractured-vuggy carbonate composition described in the first aspect;

[0019] Step 3: Prepare a model according to the spatial shape of the preset fracture-vug

[0020] Step 4: Make the substrate into a slurry, place the model in a mold, then pour the slurry, and perform static setting, demolding, and curing treatments to obtain the fracture-vug type carbonate rock reservoir simulation specimen.

[0021] In an optional embodiment, the preparation of the model includes the following process: filling the preset fracture-vug with a fluid, and freezing the fluid to form the model; wherein, the fluid is crude oil, vegetable oil or silicone oil.

[0022] In an optional embodiment, the time of the curing treatment is 7, and the curing temperature is 20-40°C;

[0023] And / or, the curing treatment includes: sprinkling water into the mold every 12 hours during the curing process.

[0024] In a third aspect, the present invention provides a physical simulation specimen of a fracture-vug type carbonate rock reservoir prepared by using the fracture-vug type carbonate rock composition described in the first aspect or the preparation method described in the second aspect, which is used to study the propagation pattern, extension, and acidification law of acid fracturing of fractures in the fracture-vug type carbonate rock reservoir.

[0025] The fracture-vug type carbonate rock composition provided by the present invention can be used to prepare a fracture-vug type carbonate rock simulation specimen, and by adjusting the composition components, the fracture-vug type carbonate rock simulation specimen prepared can achieve different mechanical parameter settings, making it approximately equivalent to the mechanical properties of real formation rocks, and is suitable for studying the propagation pattern, extension, and acidification law of acid fracturing of fractures in the fracture-vug type carbonate rock reservoir. Description of the Drawings

[0026] Figure 1 It is a physical diagram of natural outcrops and artificial fracture-vug type carbonate rock simulation specimens prepared with different compositions;

[0027] Figure 2 It is a schematic diagram of the artificial fracture-vug type carbonate rock simulation specimen prepared in Experimental Example 1;

[0028] Figure 3 It is a diagram of fluids with different viscosities formed after low-temperature treatment;

[0029] Figure 4 It is a columnar comparison diagram of the mechanical strengths of natural outcrops and artificial fracture-vug type carbonate rock simulation specimens prepared with different compositions;

[0030] Figure 5 It is a scanning electron microscope diagram of different artificial fracture-vug type carbonate rock simulation specimens.

[0031] In the figure:

[0032] 1. Artificial simulated specimens of fractured-vuggy carbonate rocks prepared from the composition of Comparative Example 1,

[0033] 2. Artificial simulated specimens of fractured-vuggy carbonate rocks prepared from the composition of Comparative Example 2,

[0034] 3. Artificial simulated specimens of fractured-vuggy carbonate rocks prepared from the composition of Example 1,

[0035] 4. Natural outcrop,

[0036] 5. Slurry,

[0037] 6. Fractured-vug body model,

[0038] 7. Freezing fluid with a viscosity of 50 mPa·s,

[0039] 8. Freezing fluid with a viscosity of 500 mPa·s,

[0040] 9. Freezing fluid with a viscosity of 1000 mPa·s. Detailed Description of the Invention

[0041] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below. The specific embodiments listed below only describe the principles and features of the present invention, and the examples are only used to explain the present invention, not to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0042] For the purpose of enhancing the production of carbonate rock reservoirs, relevant laboratory experiments are required as effective technical means for quantitative analysis. The present invention has found through research that the mechanical properties of rocks affect the initiation and propagation of artificial fractures, and the propagation pattern of artificial fractures also affects the scale of reservoir stimulation. Mechanical parameters are the numerical manifestation of the mechanical properties of rocks. Affected by factors such as mineral composition, cementation degree, and fracture development degree, the mechanical parameters of rocks in different blocks often fluctuate greatly. By optimizing the formula of artificial carbonate rocks, different mechanical parameters can be set to approximately equivalent to the mechanical properties of real formation rocks. Specifically, the present invention provides the following solutions:

[0043] In a first aspect, the present invention provides a fractured-vuggy carbonate rock composition, comprising sulfoaluminate cement; the sulfoaluminate cement comprises anhydrous calcium sulfoaluminate, dicalcium silicate, tetracalcium ferroaluminate, and gypsum.

[0044] In the present invention, the sulphoaluminate cement used in the present invention can roughly correspond to the proportion of the acid-etched components of natural rock by adjusting its component ratio, can approximately correspond to the proportion of the acid-etched components of natural rock, and its acid-etchable components are approximately 100%. It can be used to simulate the acidification experiment of real carbonate rock. Specifically, the hydration products of calcium sulphoaluminate, dicalcium silicate, and tetracalcium aluminoferrite in the sulphoaluminate cement can all undergo acidification reactions with hydrochloric acid. Its main products are ettringite, aluminium hydroxide gel, calcium silicate hydrate, and calcium sulphoaluminate. The reaction rate is aluminium hydroxide gel > ettringite > calcium sulphoaluminate > calcium silicate hydrate. This characteristic can simulate the non-uniform dissolution characteristics in carbonate rock reservoirs to study the effect of acidification in acid fracturing. Different from the traditional silicate cement, the main hydration product of which is calcium silicate hydrate, but it is difficult to react with hydrochloric acid and does not have suitable acidification characteristics to simulate the acidification experiment of real carbonate rock.

[0045] In an alternative embodiment, it further includes: carbonate rock powder.

[0046] When the sulphoaluminate cement (acid-etchable components are approximately 100%) used in the present invention is combined with carbonate rock powder, the sulphoaluminate cement acts as a cementing material to consolidate the carbonate rock powder (aggregate). The hydration products of this type of cement obtained by consolidation can all react with acidic fluids such as hydrochloric acid, ensuring that the artificial carbonate rock can undergo acidification experiments. And after the combination of sulphoaluminate cement and carbonate rock powder, it can further correspond to the proportion of the acid-etched components of natural rock, and can highly approximately correspond to the proportion of the acid-etched components of natural rock. This characteristic provides a more reliable basis for the acidification experiment of artificial carbonate rock and the exploration of acid-etching mechanism.

[0047] Among them, the size of the mesh number of the carbonate rock powder has an important influence on the mechanical strength of the carbonate rock. The larger the mesh number, the finer the particles, and the greater the mechanical strength of the artificial rock. However, the carbonate rock powder acts as an aggregate in the cement, and a larger particle size also helps to increase the stability of the artificial rock. In addition, the mixing ratio of carbonate rock powder with different mesh numbers is also a key factor affecting the heterogeneity of the artificial rock. By mixing carbonate rock powder particles with different mesh numbers, the heterogeneity of the rock matrix can be further regulated to form an artificial carbonate rock with heterogeneity. Therefore, in order to obtain an artificial carbonate rock with excellent stability and heterogeneity, in a specific embodiment, the carbonate rock powder includes a first particle with a mesh number of 30 - 50 and a second particle with a mesh number of 700 - 800.

[0048] Exemplarily, the mesh number of the first particles is any value among 30 mesh, 32 mesh, 35 mesh, 36 mesh, 37 mesh, 38 mesh, 39 mesh, 40 mesh, 42 mesh, 45 mesh, 47 mesh, 50 mesh, etc. or the range composed of any two of them; the mesh number of the second particles is any value among 700 mesh, 710 mesh, 720 mesh, 730 mesh, 750 mesh, 760 mesh, 770 mesh, 780 mesh, 790 mesh, 800 mesh, etc. or the range composed of any two of them.

[0049] In a specific embodiment, the carbonate rock powder includes calcite and / or dolomite.

[0050] In a specific embodiment, based on the total mass of 100 parts, the sulphoaluminate cement includes 75 - 82 parts of anhydrous calcium sulphoaluminate, 6 - 10 parts of dicalcium silicate, 7 - 10 parts of tetracalcium aluminoferrite, and 4 - 5 parts of gypsum;

[0051] And / or, the gypsum includes calcium sulfate dihydrate.

[0052] The sulphoaluminate cement of the above - mentioned embodiment can better chemically react with acidic liquids to form a solution, and this characteristic fits the acid - corrosion characteristics of real carbonate rocks, and is more suitable for carrying out acid - fracturing laboratory experiment analysis in oil and gas engineering.

[0053] Among them, the proportion relationship between the sulphoaluminate cement and the carbonate rock powder in the composition plays a regulating role in the mechanical properties of the artificial carbonate rock. When the proportion of the sulphoaluminate cement increases, the mechanical strength of the artificial rock shows an upward trend. Therefore, in order to improve the mechanical strength of the artificial rock, in an optional embodiment, in the fracture - vuggy carbonate rock composition, the mass proportion of the sulphoaluminate cement is not less than 40%.

[0054] Exemplarily, in the fracture - vuggy carbonate rock composition, the mass proportion of the sulphoaluminate cement is any value among 40%, 50%, 60%, 70%, 80%, 90%, etc. or the range composed of any two of them.

[0055] Among them, the more the proportion of the first particles in the carbonate rock powder, the greater the mechanical strength of the artificial carbonate rock. Therefore, in order to further ensure the mechanical strength of the artificial carbonate rock, in a specific embodiment, in the carbonate rock powder, the mass proportion of the first particles is not less than 50%.

[0056] Exemplarily, in the carbonate rock powder, the mass proportion of the first particles is any value among 50%, 60%, 70%, 80%, 90%, 100%, etc. or the range composed of any two of them.

[0057] In a second aspect, the present invention provides a method for preparing a fracture - vuggy carbonate rock reservoir simulation specimen, including the following steps:

[0058] Step 1: Select a target area and obtain test samples of natural outcrops or formation cores.

[0059] Step 2: Select the base material ratio for preparing the fractured-vuggy carbonate reservoir simulation specimen according to the density of the test sample, where the base material includes the fractured-vuggy carbonate composition described in the first aspect.

[0060] Step 3: Prepare a model according to the spatial shape of the preset fractures and vugs.

[0061] Step 4: Make the base material into a slurry, place the model in a mold, then pour the slurry, and perform static settlement, demolding, and curing treatments to obtain the fractured-vuggy carbonate reservoir simulation specimen.

[0062] In some embodiments, after obtaining the test samples of natural outcrops or formation cores, the mechanical properties and mineral components are evaluated by using X-ray diffraction (XRD) and triaxial compression tests. The main evaluation criteria include: rock tensile strength, compressive strength, elastic modulus, Poisson's ratio, and rock mineral composition, etc. These standard results represent the physical properties and mechanical properties of the formation rocks, and not only set the engineering goals of the target area for the subsequent comparison of the characteristics of artificial carbonate reservoir rocks, but also provide indispensable real data support for accurately simulating various parameters of carbonate reservoir rocks.

[0063] In some embodiments, the selection of the base material ratio for preparing the fractured-vuggy carbonate reservoir simulation specimen according to the density of the test sample includes the following process:

[0064] 1) Measuring the density of the test sample by the hydrostatic weighing method: First, weigh the mass m1 of the test sample in air with a balance. Then, prepare a container filled with a liquid of known density (usually water), suspend the core with a thin wire and immerse it completely in the liquid, and weigh the mass m2 of the test sample in the liquid. The density ρ of the test sample is calculated by the following formula,

[0065] where ρ 液 is the density of the known density liquid;

[0066] 2) Mass calculation: Using the density ρ of the test sample, calculate the mass of the natural rock with the required experimental dimensions. The mass of the natural rock is m 天然岩石 , and the mass m 人造岩石 of the simulation specimen designed in the experiment 天然岩石 = m

[0067] 3) Material ratio: According to the proportion of sulfoaluminate cement and carbonate rock powder designed in the experiment, obtain the total amount of materials used, that is, m 人造岩石 = m碳酸盐岩岩粉 +m 硫铝酸盐水泥 。

[0068] In some embodiments, the process of making the substrate into a slurry includes the following steps: Pour the pre-prepared sulfoaluminate cement and carbonate rock powder into a cement mixer, add an appropriate amount of water and stir evenly. The water addition process needs to be slow, and observe the fluidity of the mixed slurry of cement and rock powder (if too much water is added, it will affect the mechanical strength after the mixed slurry is formed), to form a uniformly textured and stable mixed slurry.

[0069] In some embodiments, during the process of pouring the slurry into the mold, place the pre-prepared model to ensure the integrity and accuracy of the fracture-vug structure. Through the experimental design scheme, the size, quantity, shape, density, type and position of the fracture-vug body can be quantitatively considered.

[0070] In some embodiments, after the slurry is poured into the mold, carefully wipe and clean the excess slurry on the surface of the mold, and place the mold in a cool and ventilated place indoors to create suitable environmental conditions for the subsequent curing reaction. After the mixed slurry stands for 24 hours and reaches the initial curing state, perform the demolding operation.

[0071] In a specific embodiment, the process of preparing the model includes the following steps: Fill the preset fracture-vugs with a fluid, and freeze the fluid to form the model; wherein, the fluid is crude oil, vegetable oil or silicone oil.

[0072] The above preparation method highly simulates the complex characteristics of oil in the fracture-vug body in natural rock. For the designed shape of the preset fracture-vugs, a suitable fluid is selected, and the fluid can fill various spaces in the fracture-vugs in the rock, such as circular, oval or irregular shapes, etc.

[0073] In some embodiments, when selecting fluids such as crude oil, vegetable oil or silicone oil, corresponding low-temperature-resistant molds with the shape of the model need to be equipped, and the fluid is subjected to low-temperature freezing treatment in the mold to ensure that the preset fracture-vug structure can be stably formed in the subsequent process.

[0074] In a specific embodiment, the time of the curing treatment is 7 days, and the curing temperature is 20 - 40 °C

[0075] And / or, the curing treatment includes: Sprinkling water into the mold every 12 hours during the curing process.

[0076] The preparation method provided by the present invention has a slurry curing time of only 7 days. Compared with the long curing cycles of traditional silicate cements and other cementitious materials, it exhibits significant early strength advantages and does not require high-temperature baking and pressure molding. This feature not only greatly shortens the experimental cycle and improves research efficiency but also provides a more rapid and efficient solution for related engineering applications.

[0077] In some embodiments, water is sprinkled into the mold every 12 hours during the curing process, which can ensure that the slurry is fully hydrated, forming a stable microstructure and excellent physical properties.

[0078] Furthermore, after the curing is completed, check whether there is powder shedding on the surface of the cement. If there is powder shedding, it indicates that the experimental scheme of this group fails to achieve the expected effect, and the formulation needs to be adjusted and optimized again; if there is no powder shedding, it indicates that the scheme of this group is successful, and the prepared artificial carbonate rock meets the basic design requirements. Subsequently, mechanical property tests need to be carried out on the artificial rock samples to further determine whether the artificial carbonate rock fully meets the design requirements.

[0079] In a third aspect, the present invention provides a physical simulation specimen of a fractured-vuggy carbonate rock reservoir prepared by using the fractured-vuggy carbonate rock composition described in the first aspect or the preparation method described in the second aspect for studying the propagation pattern, extension, and acidification law of acid fracturing of fractures in a fractured-vuggy carbonate rock reservoir.

[0080] The present invention is further described below in conjunction with specific embodiments:

[0081] Example 1

[0082] This example provides a fractured-vuggy carbonate rock composition, including sulfoaluminate cement and calcite with a mass ratio of 4:6; calculated based on a total mass of 100 parts, the sulfoaluminate cement includes 80 parts of anhydrous calcium sulfoaluminate, 7 parts of dicalcium silicate, 8 parts of tetracalcium aluminoferrite, and 5 parts of gypsum (gypsum is calcium sulfate dihydrate); the calcite has a mesh number of 40.

[0083] Example 2

[0084] The difference from Example 1 is only that: the calcite includes a first particle with a mesh number of 40 and a second particle with a mesh number of 800, and the mass ratio of the first particle to the second particle is 1:1.

[0085] Example 3

[0086] The difference from Example 1 is only that: the calcite includes a first particle with a mesh number of 400 and a second particle with a mesh number of 800, and the mass ratio of the first particle to the second particle is 1:1.

[0087] Example 4

[0088] The difference from Example 1 is only that: the calcite includes first particles and second particles with a mass ratio of 1:1, the mesh number of the first particles is 40, and the second particles include mixed particles with a mesh number ratio of 200:400:600:800 = 1:1:1:1.

[0089] Example 5

[0090] The difference from Example 1 is only that: the fractured-vuggy carbonate rock composition includes sulfoaluminate cement and calcite with a mass ratio of 7:3.

[0091] Example 6

[0092] The difference from Example 1 is only that: the fractured-vuggy carbonate rock composition includes sulfoaluminate cement and calcite with a mass ratio of 5:5.

[0093] Example 7

[0094] The difference from Example 1 is only that: the fractured-vuggy carbonate rock composition does not include calcite and is only composed of sulfoaluminate cement.

[0095] Comparative Example 1

[0096] This example provides a fractured-vuggy carbonate rock composition, which is composed of epoxy resin (model E44) and calcite with a mass ratio of 4:6; the mesh number of the calcite is 800.

[0097] Comparative Example 2

[0098] This example provides a fractured-vuggy carbonate rock composition, whose material is calcium silicate hydrate, and is composed of portland cement and calcite with a mass ratio of 4:6; the mesh number of the calcite is 800.

[0099] Test Example

[0100] The preparation method of using the compositions of the above examples and comparative examples to prepare fractured-vuggy carbonate rock reservoir simulation specimens respectively includes the following steps:

[0101] Step 1: Select the target target area and obtain test samples of natural outcrops (see Figure 1 ); conduct a detailed analysis of the mechanical properties and mineral components of the obtained natural outcrops, and record the relevant data in Table 1;

[0102] Step 2: Weigh the composition according to the ratio; according to the selected ratio, prepare the substrate ratio of the fractured-vuggy carbonate rock reservoir simulation specimen, wherein the substrate includes the fractured-vuggy carbonate rock composition described in the first aspect;

[0103] Step 3: Fill the space of the preset fracture-vug with crude oil, prepare a corresponding low-temperature resistant mold, inject the crude oil into the low-temperature mold, and perform low-temperature freezing on the crude oil injected into the low-temperature mold at -18°C to form a fracture-vug body model 6 of a predetermined shape (see Figure 2 ).

[0104] Step 4: Pour the composition into a cement mixer, add an appropriate amount of water to the mixer, start the mixer, and stir continuously for more than 30 minutes until a uniformly textured mixed slurry 5 is formed (see Figure 2 ). Place the fracture-vug body model in the mold, then pour the slurry, carefully wipe and clean the excess mixed slurry at the upper opening of the mold with tools. Place the cleaned mold in a cool place indoors to avoid direct sunlight and strong wind interference. After standing for 24 hours, perform demolding operation, and cure the demolded artificial carbonate rock for 7 days. During the curing process, evenly spray distilled water without impurities on the cement surface every 12 hours to ensure that the artificial carbonate rock maintains appropriate humidity. After the curing is completed, carefully check whether there is powdering on the cement surface. If there is no powdering, a fracture-vug type carbonate rock reservoir simulation sample is successfully prepared.

[0105] Performance testing and result analysis

[0106] 1. Observe the morphologies of the fracture-vug type carbonate rock reservoir simulation samples prepared from the compositions of Comparative Examples 1-2 and Example 1, and the physical pictures are shown in Figure 1 ; in the figure, the epoxy resin type represents Comparative Example 1, the silicate type represents Comparative Example 2, and the composite sulfate type represents Example 1;

[0107] 2. Test the adaptability of the composition of Example 1 above to different formation depths: Pour the composition into a cement mixer, add water in different proportions to the mixer, start the mixer, and stir continuously for more than 30 minutes until a number of uniformly textured mixed slurry pastes are formed. Pour them into molds respectively and perform low-temperature freezing at -18°C to obtain frozen fluids with viscosities of 50 mPa·s, 500 mPa·s, and 1000 mPa·s (see Figure 3 ). It can be seen from the results that the composition of the present invention can be used to simulate crude oils with different viscosities in the formation and has good adaptability to different formation depths.

[0108] 3. Test the following mechanical properties of the fracture-vug type carbonate rock reservoir simulation samples prepared from the compositions of Comparative Examples 1-2 and Examples 1-7:

[0109] Tensile strength (inspection method for cement mortar strength: GB / T 17671—1999), compressive strength (inspection method for cement mortar strength: GB / T 17671—1999), elastic modulus (standard for test methods of physical and mechanical properties of concrete: GB / T 50081—2019), Poisson's ratio (standard for test methods of physical and mechanical properties of concrete: GB / T 50081—2019). The test results are shown in Table 1 or Figure 4 ; In the figure, epoxy resin represents Comparative Example 1, Portland cement represents Comparative Example 2, and composite sulfate cement represents Example 1;

[0110] 4. Use a scanning electron microscope to observe the morphology of the fractured-vuggy carbonate reservoir simulation specimens prepared from the compositions of Comparative Example 2 and Example 1, as well as the natural outcrop. The results are shown in Figure 5 .

[0111] Table 1:

[0112]

[0113] Conclusion: From the data in Table 1 above, it can be seen that compared with the comparative examples, the fractured-vuggy carbonate rock composition of the examples can be used to prepare artificial fractured-vuggy carbonate rock reservoir simulation specimens with different mechanical parameters by adjusting the component ratios; furthermore, the fractured-vuggy carbonate rock reservoir simulation specimen prepared from the fractured-vuggy carbonate rock composition of Example 1 is approximately equivalent to the mechanical properties of the carbonate rock in the real formation.

[0114] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fractured-vuggy carbonate rock composition, characterized in that, It includes sulfoaluminate cement; the sulfoaluminate cement includes calcium anhydrous sulfoaluminate, dicalcium silicate, tetracalcium aluminoferrite and gypsum.

2. The fracture-vuggy carbonate rock composition according to claim 1, wherein It also includes carbonate rock powder.

3. The fractured-vuggy carbonate rock composition according to claim 2, wherein The carbonate rock powder includes first particles with a mesh number of 30 - 50 and second particles with a mesh number of 700 - 800; and / or, the carbonate rock powder includes calcite and / or dolomite.

4. The fracture-vuggy carbonate rock composition according to any one of claims 1-3, characterized in that Calculated by a total mass of 100 parts, the sulfoaluminate cement includes 75 - 82 parts of calcium anhydrous sulfoaluminate, 6 - 10 parts of dicalcium silicate, 7 - 10 parts of tetracalcium aluminoferrite and 4 - 5 parts of gypsum; and / or, the gypsum includes calcium sulfate dihydrate.

5. The fracture-vuggy carbonate rock composition according to any one of claims 1-4, characterized in that, In the fracture - vuggy carbonate rock composition, the mass proportion of the sulfoaluminate cement is not less than 40%.

6. The fractured-vuggy carbonate rock composition according to any one of claims 3-4, characterized in that, In the carbonate rock powder, the mass proportion of the first particles is not less than 50%.

7. A method for preparing a simulation sample of a fracture-vuggy carbonate reservoir, characterized in that, It includes the following steps: Step 1: Select a target area and obtain test samples of natural outcrops or formation cores; Step 2: Select the substrate ratio for preparing the fracture - vuggy carbonate rock reservoir simulation specimen according to the density of the test sample, wherein the substrate includes the fracture - vuggy carbonate rock composition according to any one of claims 1 - 6; Step 3: Prepare a model according to the spatial shape of the preset fractures and vugs; Step 4: Make the substrate into a slurry, place the model in a mold, then pour the slurry, and carry out static setting, demolding and curing treatments to obtain the fracture - vuggy carbonate rock reservoir simulation specimen.

8. The preparation method according to claim 7, wherein the preparation of the model comprises the following process: filling the preset fracture-vug with a fluid, and freezing the fluid to form the model; wherein, The fluid is crude oil, vegetable oil or silicone oil.

9. According to the preparation method of claim 8, the time of the curing treatment is 7 days, and the curing temperature is 20 - 40 °C; And / or, the curing treatment includes: During the curing process, sprinkle water into the mold every 12 hours.

10. A fracture - vuggy carbonate rock reservoir simulation specimen prepared by using the fracture - vuggy carbonate rock composition according to any one of claims 1 - 6 or the preparation method according to any one of claims 7 - 9 is used to study the propagation pattern, extension and acidification law of acid fracturing of fractures in the fracture - vuggy carbonate rock reservoir.

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