A quantitative evaluation method for CO2 volume fracturing efficiency in shale oil horizontal wells

Abstract

The present invention provides a quantitative evaluation method for the CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells, comprising obtaining the amount of fluid injected into the ground from a CO2 test well and a comparison well; determining the optimal CO2 injection rate for a single well of the CO2 test well based on a geological model of the reservoir where the shale oil horizontal well is located; pre-constructing the geological model of the reservoir where the shale oil horizontal well is located using basic reservoir parameters of the CO2 test well and dynamic production parameters of the horizontal well; and calculating the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of fluid injected into the ground from the CO2 test well, the amount of fluid injected into the ground from the comparison well, and the CO2 injection rate for a single well of the CO2 test well. This method forms a mine-scale calculation method for CO2 volume fracturing energy enhancement efficiency, solves the problem of quantitatively evaluating mine-scale CO2 energy enhancement efficiency, is simple, feasible, and highly operational, and is also applicable to the calculation of imbibition volume of fracturing fluid in other unconventional reservoirs, providing reliable support for the improvement and optimization of volume fracturing technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of petroleum and natural gas engineering, and relates to a method for quantitatively evaluating the efficiency of CO2 volume fracturing energy enhancement in shale oil horizontal wells. Background Art

[0002] The key to the efficient development of shale oil and gas is the injection of large-scale, high-displacement water-based fracturing fluids into the formation to form a complex fracture network. Under the current volume fracturing technology model, the average fluid volume per well is large, and the oil-seeking and fluid-discharging cycles are long, which seriously affects the oil production rate. In addition, the energy replenishment method is single, and stable production is difficult. The reservoir cannot be effectively and fully utilized. In order to further improve the recovery rate, it is urgent to explore new injection media for production enhancement research. Among them, carbon dioxide (CO2) has unique advantages such as low viscosity and easy injection, high diffusion coefficient, strong solubility, obvious energy enhancement effect, and water resource conservation. It is an important direction for shale oil production enhancement. Continental shale oil is usually characterized by low pressure and strong heterogeneity. Supplementing formation energy is an important means to increase single well production. Among them, energy enhancement efficiency is the core indicator for evaluating the CO2 energy enhancement effect. However, the seepage law of CO2 entering the formation is extremely complex, and the quantitative evaluation of the energy enhancement efficiency of CO2 injected into the formation is extremely difficult. Compared with the main fracturing fluid, what is the energy enhancement efficiency of CO2? How much fracturing fluid can CO2 replace to achieve the same energy enhancement effect, thereby saving water resources. At present, there is an urgent need for quantitative characterization on site to further optimize fracturing construction parameters and guide on-site construction. At present, domestic and foreign scholars have conducted some research on the energy enhancement effect of CO2, mainly in the following categories:

[0003] (1) Zhang Kuangsheng (Zhang Kuangsheng, Bai Xiaohu, Liu Shun, et al. Effect of CO2 injection on tight oil reservoirs and parameter optimization [J]. Science and Technology Engineering, 2020, 20(26): 10752-10758). In order to study the effect of CO2 injection on tight oil reservoirs, the article analyzes the influence of CO2 on the pore structure of the reservoir, and analyzes the changes in the volume coefficient and saturation pressure of crude oil after CO2 injection through phase calculation. Using the finite difference method and the three-dimensional finite element method, a three-dimensional dynamic geostress and reservoir bidirectional coupling model is established, the change law of reservoir permeability and the pressure distribution characteristics near the bottom of the well are analyzed, and the effect of CO2 injection on the energy enhancement is evaluated.

[0004] (2) Liu Yincang et al. (Liu Yincang, Qiu Wei, Song Yongfang et al. A composite fracturing method for continental shale oil reservoirs, patent number: CN202110332966.5) This method first uses acid to pretreat the reservoir; liquid carbon dioxide is injected into the pretreated reservoir, and then acidic gel fluid is used to create main fractures, and slick water is used to open and expand micro-fractures and branch fracture systems. The use of pre-liquid CO2 is mainly to increase the formation energy and improve the post-fracturing return rate.

[0005] (3) Shen Yiding et al. (Shen Yiding, Qiu Lewei, Yang Xiaowu et al. A CO2-enhanced acidic clean fracturing fluid and its preparation method, patent number: CN201610320618.5). This method dissolves a water-soluble polyether nonionic surfactant, a long-chain tertiary ammonium salt cationic surfactant, and potassium chloride in water to form a composite emulsion base liquid; liquid CO2 is added to the above emulsion and stirred evenly to obtain an acidic clean fracturing fluid. The CO2-enhanced fracturing fluid can not only improve the flowback capacity; but also the liquid CO2 can interact with the low-viscosity composite emulsion to form a high-viscosity gel. The acidic clean fracturing fluid and the CO2 foam fracturing fluid work together to improve the recovery efficiency.

[0006] In summary, method (1) uses numerical simulation to analyze the changes in formation pressure corresponding to different CO2 injection rates and evaluate the energy enhancement effect. This method has a large error in establishing an ideal numerical simulation. At the same time, it only stays at the change in formation pressure and cannot answer the specific energy enhancement multiple of CO2 compared to fracturing fluid at the mine scale, nor can it specify the field optimization design. Methods (2) and (3) apply the CO2 energy enhancement effect to shale oil volume fracturing. The CO2 field injection rate relies on experience, and no relevant basis has been established. Therefore, it is still impossible to effectively evaluate the energy enhancement efficiency of CO2 volume fracturing at the mine scale. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a quantitative evaluation method for the CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells, thereby solving the technical problem in the prior art that it is impossible to quantitatively and effectively evaluate the CO2 volume fracturing energy enhancement efficiency at the mine scale.

[0008] The present invention is achieved through the following technical solutions:

[0009] A quantitative evaluation method for CO2 volume fracturing efficiency in shale oil horizontal wells comprises the following steps:

[0010] Obtain the amount of fluid injected into the ground from the CO2 test well and the comparison well;

[0011] Determine the optimal CO2 injection rate for a single well of the CO2 test well based on the reservoir geological model of the shale oil horizontal well;

[0012] Calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the single-well CO2 injection rate of the CO2 test well;

[0013] The reservoir geological model where the shale oil horizontal well is located is pre-constructed based on the basic parameters of the reservoir section of the CO2 test well and the production dynamic parameters of the horizontal well.

[0014] Preferably, the construction of the reservoir geological model where the shale oil horizontal well is located includes the following process:

[0015] S21: Obtain the basic parameters of the reservoir section of the CO2 test well and the production performance parameters of the horizontal well;

[0016] S22: constructing an initial geological model based on the basic parameters of the reservoir section of the CO2 test well;

[0017] S23: using the initial geological model to obtain the distribution of the reservoir permeability field, porosity field, oil saturation field, and formation pressure field where the horizontal well is located;

[0018] S24: The initial geological model is simulated and corrected based on the reservoir permeability field, porosity field, oil saturation field, formation pressure field distribution, and horizontal well production dynamic parameters to complete the establishment of the reservoir geological model where the shale oil horizontal well is located.

[0019] Preferably, the basic parameters of the reservoir section of the CO2 test well include target reservoir burial depth, target reservoir thickness, permeability, porosity, oil saturation, reservoir temperature, reservoir pressure and crude oil viscosity;

[0020] The horizontal well production dynamic parameters include the daily liquid production, daily oil production and daily water production of a single horizontal well in the first year.

[0021] Preferably, the process of simulating and correcting the initial geological model is as follows:

[0022] Importing the hydraulic fracture parameters of the horizontal well into the initial geological model, fitting the daily liquid production, daily oil production, and daily water production in the first year according to the actual production working system of the horizontal well, if the relative errors of the fitted daily liquid production, daily oil production, and daily water production in the first year compared with the obtained daily liquid production, daily oil production, and daily water production of the horizontal well in the first year are no more than 5%, then the established initial geological model meets the use requirements;

[0023] On the contrary, the initial geological model is corrected by adjusting the basic parameters of the reservoir section until the relative errors of the fitted first-year daily liquid production, daily oil production, and daily water production are no more than 5% when compared with the obtained first-year daily liquid production, daily oil production, and daily water production of a single horizontal well, thereby completing the establishment of the geological model.

[0024] Preferably, the process of determining the single-well CO2 injection rate of the CO2 test well based on the reservoir geological model of the shale oil horizontal well is specifically as follows: according to the reservoir geological model of the shale oil horizontal well, the correlation between different CO2 injection rates and the area of ​​the oil-water two-phase miscible region is obtained; when the area of ​​the miscible region no longer changes with the CO2 injection rate, the single-segment CO2 optimal injection rate is obtained; based on the single-segment CO2 optimal injection rate and combined with the actual number of injection sections in the mine, the single-well CO2 optimal injection rate of the CO2 test well is determined.

[0025] Preferably, the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is calculated based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the single-well CO2 injection rate of the CO2 test well, specifically by obtaining the horizontal well geological parameters and horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well, and when the relative errors of the horizontal well geological parameters and horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well are no more than 5%, the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is calculated based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the single-well CO2 injection rate of the CO2 test well; specifically,

[0026]

[0027] Where: Ep is the energy efficiency, times; V T is the amount of liquid entering the ground in the comparison well, m 3 ; V O is the amount of liquid entering the ground in the CO2 test well, m 3 ; V C is the CO2 injection rate of the CO2 test well, m 3 .

[0028] Preferably, the horizontal well geological parameters include the horizontal section length of the horizontal well and the oil layer drilling rate parameter;

[0029] The horizontal well volume fracturing transformation parameters include the number of fracturing stages, the number of fracturing clusters, the amount of liquid injected into the ground, the amount of sand added, the construction displacement, and the wellbore pressure in the first thirty days.

[0030] A quantitative evaluation system for CO2 volume fracturing efficiency in shale oil horizontal wells, comprising:

[0031] Parameter acquisition unit: The parameter acquisition unit is used to obtain the amount of liquid injected into the ground in the CO2 test well and the comparison well;

[0032] First data processing unit: The first data processing unit is used to determine the optimal CO2 injection rate for a single CO2 test well based on the reservoir geological model of the shale oil horizontal well; the reservoir geological model of the shale oil horizontal well is pre-constructed based on the basic parameters of the reservoir section of the CO2 test well and the production performance parameters of the horizontal well;

[0033] Second data processing unit: The second data processing unit is used to calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid entering the ground of the CO2 test well, the amount of liquid entering the ground of the comparison well, and the single-well CO2 injection volume of the CO2 test well.

[0034] A terminal device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0035] A computer-readable storage medium stores a computer program, which implements the steps of the above method when executed by a processor.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] The present invention discloses a quantitative evaluation method for the CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells. The method determines the optimal CO2 injection rate of a single CO2 test well based on the reservoir geological model of the shale oil horizontal well. Combined with the amount of liquid injected into the ground from the CO2 test well and the comparison well, the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is quantitatively obtained, forming a mine-scale calculation method for the CO2 volume fracturing energy enhancement efficiency, thereby solving the problem of quantitatively evaluating the CO2 energy enhancement efficiency at the mine scale. The method is simple, feasible, and highly operational, and is also applicable to the calculation of the imbibition volume of fracturing fluid in other unconventional reservoirs, providing reliable support for the improvement and optimization of volume fracturing technology.

[0038] Furthermore, the reservoir geological model of the established shale oil horizontal wells was simulated and corrected using the horizontal well hydraulic fracture parameters and horizontal well production dynamic parameters, which effectively improved the accuracy of the model and the accuracy of the quantitative evaluation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 Schematic diagram of a quantitative evaluation method for CO2 volume fracturing efficiency of shale oil horizontal wells in the present invention;

[0041] Figure 2 This is a schematic diagram of the structure of a quantitative evaluation system for CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells in the present invention;

[0042] Figure 3 This is a flow chart for calculating the CO2 volume fracturing efficiency of shale oil horizontal wells in Example 3 of the present invention;

[0043] Figure 4This is a diagram showing the actual daily liquid production, daily oil production, and daily water production of a shale oil horizontal well in Example 3 of the present invention;

[0044] Figure 5 This is a fitting diagram of the actual daily liquid production of a shale oil horizontal well in Example 3 of the present invention;

[0045] Figure 6 This is a fitting diagram of the actual daily oil production of a shale oil horizontal well in Example 3 of the present invention;

[0046] Figure 7 This is a fitting diagram of the actual daily water production of a shale oil horizontal well in Example 3 of the present invention;

[0047] Figure 8 This is a correlation diagram between the single-stage CO2 injection rate and the miscible area in Example 3 of the present invention;

[0048] Figure 9 A comparison chart of geological and fracturing parameters of a shale oil test well and a comparison well in Example 3 of the present invention;

[0049] Figure 10 This is a comparison chart of the pressure of the shale oil test well and the reference well in Example 3 of the present invention. DETAILED DESCRIPTION

[0050] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0051] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0052] Herein, all features such as values, amounts, amounts, and concentrations defined in numerical ranges or percentage ranges are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0053] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0054] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0055] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0056] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0057] Example 1

[0058] like Figure 1 As shown, the present invention provides a method for quantitatively evaluating the efficiency of CO2 volume fracturing energy enhancement in shale oil horizontal wells, comprising the following steps:

[0059] S1: Obtain the amount of liquid injected into the ground from the CO2 test well and the comparison well;

[0060] S2: Determine the optimal CO2 injection rate for a single CO2 test well based on a reservoir geological model of the shale oil horizontal well. The reservoir geological model of the shale oil horizontal well is pre-constructed based on basic reservoir parameters of the CO2 test well and production performance parameters of the horizontal well.

[0061] The construction of the reservoir geological model of the shale oil horizontal well includes the following processes:

[0062] S21: Obtain the basic parameters of the reservoir section of the CO2 test well and the production performance parameters of the horizontal well;

[0063] The basic parameters of the reservoir section of the CO2 test well include target reservoir burial depth, target reservoir thickness, permeability, porosity, oil saturation, reservoir temperature, reservoir pressure and crude oil viscosity;

[0064] The horizontal well production dynamic parameters include the daily liquid production, daily oil production and daily water production of a single horizontal well in the first year.

[0065] S22: constructing an initial geological model based on the basic parameters of the reservoir section of the CO2 test well;

[0066] S23: using the initial geological model to obtain the distribution of the reservoir permeability field, porosity field, oil saturation field, and formation pressure field where the horizontal well is located;

[0067] S24: The initial geological model is simulated and corrected based on the reservoir permeability field, porosity field, oil saturation field, formation pressure field distribution, and horizontal well production dynamic parameters to complete the establishment of the reservoir geological model where the shale oil horizontal well is located.

[0068] The specific process of simulating and correcting the initial geological model is as follows:

[0069] Importing the hydraulic fracture parameters of the horizontal well into the initial geological model, fitting the daily liquid production, daily oil production, and daily water production in the first year according to the actual production working system of the horizontal well, if the relative errors of the fitted daily liquid production, daily oil production, and daily water production in the first year compared with the obtained daily liquid production, daily oil production, and daily water production of the horizontal well in the first year are no more than 5%, then the established initial geological model meets the use requirements;

[0070] On the contrary, the initial geological model is corrected by adjusting the basic parameters of the reservoir section until the relative errors of the fitted first-year daily liquid production, daily oil production, and daily water production are no more than 5% when compared with the obtained first-year daily liquid production, daily oil production, and daily water production of a single horizontal well, thereby completing the establishment of the geological model.

[0071] Here, the relative error is calculated as

[0072]

[0073] Where ω1 is the relative error between the daily liquid production, daily oil production, and daily water production in the first year and the daily liquid production, daily oil production, and daily water production of a single horizontal well in the first year.

[0074] In the relative error judgment process, the relative errors of daily liquid production, daily oil production, and daily water production in the first year must be no more than 5% to improve the model accuracy.

[0075] In addition, the process of determining the single-well CO2 injection rate of the CO2 test well based on the reservoir geological model of the shale oil horizontal well is specifically as follows: according to the reservoir geological model of the shale oil horizontal well, the correlation between different CO2 injection rates and the area of ​​the oil-water two-phase miscible region is obtained; when the area of ​​the miscible region no longer changes with the CO2 injection rate, the optimal single-stage CO2 injection rate is obtained; based on the said single-stage CO2 optimal injection rate and combined with the actual number of injection sections in the mine, the optimal CO2 injection rate of the single-well CO2 test well is determined.

[0076] S3: Calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the single-well CO2 injection rate of the CO2 test well.

[0077] Specifically, the horizontal well geological parameters and horizontal well volume fracturing parameters of the CO2 test well and the comparison well are obtained. When the relative error between the horizontal well geological parameters and horizontal well volume fracturing parameters of the CO2 test well and the comparison well is no more than 5%, the CO2 volume fracturing efficiency of the shale oil horizontal well is calculated based on the amount of liquid injected into the ground in the CO2 test well, the amount of liquid injected into the ground in the comparison well, and the single-well CO2 injection volume of the CO2 test well. Specifically,

[0078]

[0079] Where: Ep is the energy efficiency, times; V T is the amount of liquid entering the ground in the comparison well, m 3 ; V O is the amount of liquid entering the ground in the CO2 test well, m 3 ; V C is the CO2 injection rate of the CO2 test well, m 3 .

[0080] Here, the larger the value of CO2 volume fracturing energy enhancement efficiency is, the better the energy enhancement effect is.

[0081] When the relative errors of the horizontal well geological parameters and the horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well are greater than 5%, the comparison well is reselected so that the relative errors of the horizontal well geological parameters and the horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well are no more than 5%.

[0082] Here, the relative error is calculated as

[0083]

[0084] Where ω2 is the relative error between the horizontal well geological parameters and the horizontal well volume fracturing stimulation parameters of the CO2 test well and the comparison well.

[0085] The horizontal well geological parameters include the horizontal section length of the horizontal well and the oil layer drilling rate parameter;

[0086] The horizontal well volume fracturing transformation parameters include the number of fracturing stages, the number of fracturing clusters, the amount of liquid injected into the ground, the amount of sand added, the construction displacement, and the wellbore pressure in the first thirty days.

[0087] Among them, in the relative error judgment process, the horizontal section length of the horizontal well, oil layer drilling rate parameters, number of fracturing stages, number of fracturing clusters, amount of liquid injected into the ground, amount of sand added, construction displacement and wellbore pressure in the first 30 days must not exceed 5% to ensure the similarity of the reservoir geology of the two horizontal wells.

[0088] The purpose of the present invention is to provide a quantitative characterization method for the CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells. For different types of reservoirs, first, the downhole rock samples of the shale oil reservoir section are processed into standard rock samples, and the physical properties of the rock samples, such as porosity, permeability, and oil saturation, are tested. At the same time, basic parameters such as the target reservoir and horizontal well production dynamics are obtained. Secondly, a shale oil geological model is established based on the basic parameters of the target reservoir, and numerical simulation of the pre-CO2 energy enhancement effect is carried out to optimize the single-stage CO2 injection volume. Finally, the geological parameters, volume fracturing transformation parameters, and pressure change data of the horizontal wells on the same platform of the target reservoir shale oil are collected, and the energy enhancement efficiency is quantitatively calculated. The larger the value, the higher the energy enhancement effect, thereby achieving the purpose of characterizing the CO2 volume fracturing energy enhancement efficiency of shale horizontal wells. The present invention proposes a quantitative characterization method for the CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells, forming a mine-scale calculation method for the CO2 volume fracturing energy enhancement efficiency. The core of this invention addresses the question of CO2 augmentation efficiency at the mine site scale, specifically how much fracturing fluid must be replaced with CO2 to achieve the same augmentation effect. This allows mines to further optimize CO2 injection rates and conserve water resources. Compared to previous methods that rely solely on experimental or numerical simulations to characterize fracturing fluid imbibition volume, this method significantly improves both calculation methodology and accuracy. This simple, feasible, and highly operational method is also applicable to calculating fracturing fluid imbibition volume in other unconventional reservoirs, providing reliable support for the advancement and optimization of volumetric fracturing technology.

[0089] Example 2

[0090] In addition, if Figure 2 As shown, the present invention also provides a quantitative evaluation system for CO2 volume fracturing energy enhancement efficiency of shale oil horizontal wells, comprising:

[0091] Parameter acquisition unit: The parameter acquisition unit is used to obtain the amount of liquid injected into the ground in the CO2 test well and the comparison well;

[0092] The first data processing unit is used to determine the optimal CO2 injection rate for a single well of the CO2 test well based on the reservoir geological model of the shale oil horizontal well;

[0093] Second data processing unit: The second data processing unit is used to calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid entering the ground of the CO2 test well, the amount of liquid entering the ground of the comparison well, and the single-well CO2 injection volume of the CO2 test well.

[0094] Example 3

[0095] like Figure 3 In order to further illustrate the technical solution of the present invention, the following examples are provided for explanation:

[0096] A certain test well H1 was treated with volume fracturing. The horizontal section was 1920m long, the oil layer drilling rate was 85.0%, a total of 24 fracturing sections were performed, and the total fracturing fluid volume was 32740m 3 , describing the specific implementation process of the present invention.

[0097] This example provides a quantitative characterization method for the efficiency of CO2 volumetric fracturing in shale oil horizontal wells, as follows:

[0098] S1: Process downhole rock samples from the shale oil reservoir section into standard rock samples to obtain basic reservoir parameters and horizontal well production dynamic parameters of the shale oil reservoir section; specifically, the following:

[0099] S11: rock sample processing, specifically obtaining downhole cores from the reservoir where the CO2 test well H1 is located or from a horizontal well in the same layer of the same block, and making standard rock samples with a diameter of 2.5 cm and a length of 5 cm from the reservoir section. The standard rock samples are placed in a 100°C oven and dried to constant weight;

[0100] S12: Testing the physical properties of the rock sample, specifically using a porosity meter with helium as the working medium to test the porosity of the rock sample after drying in step S11; using a helium porosity automatic meter and an ultra-low permeability meter to test the rock sample after drying in step S11, the porosity is 6.5% and the permeability is 0.15 mD, respectively, providing a basis for collecting basic reservoir parameters;

[0101] In addition, the basic reservoir parameters include target reservoir burial depth, reservoir thickness, permeability, porosity, oil saturation, reservoir temperature, reservoir pressure, crude oil viscosity and other basic parameters, see Table 1.

[0102] Table 1 Basic parameters of the reservoir where the CO2 test well H1 is located

[0103]

[0104]

[0105] The horizontal well production dynamic parameters include basic parameters such as the actual daily liquid production, actual daily oil production, and actual daily water production of a single horizontal well in the first year.

[0106] S2: Establish a shale oil geological model based on basic reservoir parameters and horizontal well production dynamic parameters, conduct numerical simulation of CO2 energy enhancement effects, and optimize the single-stage CO2 injection rate; specifically, it includes the following:

[0107] S21: Establishment of geological model, specifically, based on the basic reservoir parameters, using the reservoir numerical simulation software Eclipse to establish the reservoir geological model where the horizontal well is located, and obtain the distribution of permeability field, porosity field, oil saturation field, formation pressure field, etc. of the reservoir where the horizontal well is located.

[0108] S22: geological model correction, specifically, importing the horizontal well hydraulic fracture parameters into the geological model of step S21, combining the actual production data of the horizontal well, and fitting the first year's daily liquid production, daily oil production, daily water production and other indicators according to the actual production working system of the horizontal well, see Figures 4 to 7 The relative errors are all less than 5%, which verifies the correctness of the model, effectively improves the model accuracy, and further carries out numerical simulation of the pre-CO2 energy enhancement effect.

[0109] S23: Single-stage CO2 injection rate optimization, specifically based on the correction of the reservoir geological model where the horizontal well is located, carry out numerical simulation of the energy enhancement effect of different CO2 injection rates, and obtain the correlation between different CO2 injection rates and the area of ​​oil-water miscible phase according to the geological model. Figure 8 When the area of ​​the miscible region does not change with the CO2 injection rate, the energy enhancement effect is the best, and the optimal CO2 injection rate for a single stage is determined.

[0110] S3: Collect geological parameters of horizontal wells in the shale oil reservoir section, volume fracturing stimulation parameters, and pressure change data during the well blocking stage, and quantitatively calculate the energy enhancement efficiency, specifically including the following:

[0111] The horizontal well geological parameters include the horizontal section length and oil layer drilling rate parameters of the CO2 test well and the comparison well on the same platform. The relative error of the geological parameters of the CO2 test well and the comparison well is required to be less than 5% to ensure the geological similarity of the reservoirs where the two horizontal wells are located. Figure 9 .

[0112] The parameters of horizontal well volume fracturing transformation include the number of fracturing stages, number of fracturing clusters, amount of fluid injected into the ground, amount of sand added, and operation displacement (such as Figure 9 ) and other parameters, and collect the well pressure data for the first thirty days (as shown in Figure 10 As shown in the figure, the relative error between the CO2 test well and the comparison well parameters is required to be less than 5% to ensure the similarity of the horizontal well reservoir stimulation parameters of the two wells;

[0113] Energy enhancement efficiency calculation is specifically to calculate the CO2 injection rate of the test well according to step S2 under the condition that the horizontal well geological parameters and reservoir transformation parameters are similar. The test well is selected to inject CO2 before the ten-stage development. The total amount of CO2 per well is V C 3000m 3 , in step S3, the amount of liquid entering the test well V O 24300m 3 Compared with the same platform, the amount of liquid entering the well V T 35682m 3 , the energy enhancement efficiency of the test well is calculated to be 3.8 times using the following formula.

[0114]

[0115] Where: Ep is the energy efficiency, times; V T is the amount of liquid entering the ground in the comparison well, m 3 ; V O is the amount of liquid entering the ground in the CO2 test well, m 3 ; V C is the CO2 injection rate of the CO2 test well, m 3 .

[0116] A schematic diagram of a terminal device provided in one embodiment of the present invention. The terminal device in this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of each of the aforementioned method embodiments are implemented. Alternatively, when the processor executes the computer program, the functions of each module / unit in each of the aforementioned device embodiments are implemented.

[0117] The computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to accomplish the present invention.

[0118] The terminal device may be a computing device such as a desktop computer, a notebook computer, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0119] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0120] The memory may be used to store the computer programs and / or modules, and the processor implements various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory.

[0121] If the module / unit integrated in the terminal device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of each of the above-mentioned method embodiments. The computer program includes computer program code, which can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0122] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A quantitative evaluation method for CO2 volume fracturing efficiency in shale oil horizontal wells, characterized in that: The following steps are involved: Obtain the amount of fluid injected into the ground from the CO2 test well and the comparison well; Determine the optimal CO2 injection rate for a single well of the CO2 test well based on the reservoir geological model of the shale oil horizontal well; Calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the optimal CO2 injection rate for a single well of the CO2 test well; The reservoir geological model where the shale oil horizontal well is located is pre-constructed based on the basic parameters of the reservoir section of the CO2 test well and the production dynamic parameters of the horizontal well; The construction of the reservoir geological model of the shale oil horizontal well includes the following processes: S21: Obtain the basic parameters of the reservoir section of the CO2 test well and the production performance parameters of the horizontal well; S22: constructing an initial geological model based on the basic parameters of the reservoir section of the CO2 test well; S23: using the initial geological model to obtain the distribution of the reservoir permeability field, porosity field, oil saturation field, and formation pressure field where the horizontal well is located; S24: Simulating and correcting the initial geological model based on the reservoir permeability field, porosity field, oil saturation field, formation pressure field distribution, and horizontal well production dynamic parameters to complete the establishment of the reservoir geological model where the shale oil horizontal well is located; The basic parameters of the reservoir section of the CO2 test well include target reservoir burial depth, target reservoir thickness, permeability, porosity, oil saturation, reservoir temperature, reservoir pressure and crude oil viscosity; The horizontal well production dynamic parameters include the daily liquid production, daily oil production and daily water production of a single horizontal well in the first year.

2. The method for quantitatively evaluating the efficiency of CO2 volume fracturing in shale oil horizontal wells according to claim 1, characterized in that: The specific process of simulating and correcting the initial geological model is as follows: Importing the hydraulic fracture parameters of the horizontal well into the initial geological model, fitting the daily liquid production, daily oil production, and daily water production in the first year according to the actual production working system of the horizontal well, if the relative errors of the fitted daily liquid production, daily oil production, and daily water production in the first year compared with the obtained daily liquid production, daily oil production, and daily water production of the horizontal well in the first year are no more than 5%, then the established initial geological model meets the use requirements; On the contrary, the initial geological model is corrected by adjusting the basic parameters of the reservoir section until the relative errors of the fitted daily liquid production, daily oil production and daily water production in the first year are no more than 5% when compared with the obtained daily liquid production, daily oil production and daily water production of a single horizontal well in the first year, thereby completing the establishment of the initial geological model.

3. The method for quantitatively evaluating the efficiency of CO2 volume fracturing for shale oil horizontal wells according to claim 1, characterized in that: The process of determining the single-well CO2 injection rate of the CO2 test well based on the reservoir geological model of the shale oil horizontal well is specifically as follows: according to the reservoir geological model of the shale oil horizontal well, the correlation between different CO2 injection rates and the area of ​​the oil-water two-phase miscible region is obtained; when the area of ​​the miscible region no longer changes with the CO2 injection rate, the optimal single-stage CO2 injection rate is obtained; based on the said single-stage CO2 optimal injection rate and combined with the actual number of injection sections in the mine, the optimal CO2 injection rate of the single-well CO2 test well is determined.

4. The method for quantitatively evaluating the efficiency of CO2 volume fracturing in shale oil horizontal wells according to claim 1, wherein: The CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is calculated based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the optimal CO2 injection rate for a single well of the CO2 test well. Specifically, the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is calculated by obtaining the horizontal well geological parameters and horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well. When the relative errors of the horizontal well geological parameters and horizontal well volume fracturing transformation parameters of the CO2 test well and the comparison well are no more than 5%, the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well is calculated based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the CO2 injection rate for a single well of the CO2 test well. Specifically, Where: E p is the energy enhancement efficiency, times; V T is the amount of liquid entering the ground in the comparison well, m 3 ; V O is the amount of liquid entering the ground in the CO2 test well, m 3 ; V C is the CO2 injection rate of the CO2 test well, m 3 .

5. A quantitative evaluation method for CO2 volume fracturing efficiency of shale oil horizontal wells according to claim 4, characterized in that: The horizontal well geological parameters include the horizontal section length of the horizontal well and the oil layer drilling rate parameter; The horizontal well volume fracturing transformation parameters include the number of fracturing stages, the number of fracturing clusters, the amount of liquid injected into the ground, the amount of sand added, the construction displacement, and the wellbore pressure in the first thirty days.

6. A quantitative evaluation system for CO2 volume fracturing efficiency of shale oil horizontal wells, characterized by: A method for quantitatively evaluating the efficiency of CO2 volume fracturing in a shale oil horizontal well as claimed in any one of claims 1 to 5, comprising: Parameter acquisition unit: The parameter acquisition unit is used to obtain the amount of liquid injected into the ground in the CO2 test well and the comparison well; First data processing unit: The first data processing unit is used to determine the optimal CO2 injection rate for a single CO2 test well based on the reservoir geological model of the shale oil horizontal well; the reservoir geological model of the shale oil horizontal well is pre-constructed based on the basic parameters of the reservoir section of the CO2 test well and the production performance parameters of the horizontal well; Second data processing unit: The second data processing unit is used to calculate the CO2 volume fracturing energy enhancement efficiency of the shale oil horizontal well based on the amount of liquid injected into the CO2 test well, the amount of liquid injected into the comparison well, and the optimal CO2 injection rate of a single well of the CO2 test well.

7. A terminal device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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