A method and apparatus for hydraulic fracturing of rocks under resonant excitation

Abstract

This invention discloses a method and apparatus for hydraulic fracturing of rocks under resonant excitation. The method includes: acquiring time-series data of the excitation frequency and strain time-series data of the target rock sample (excluding the perforation face) based on the simulated orifice diameter of the target rock sample; determining the resonant frequency of the target rock sample under the influence of the simulated orifice diameter from the time-series data of the excitation frequency based on the strain time-series data; determining the fracturing initiation pressure and fracturing azimuth of the target rock sample under the resonant frequency and a preset resonant excitation time; and formulating a fracture induction scheme under resonant excitation based on the fracturing initiation pressure and fracturing azimuth, so as to perform hydraulic fracturing based on the fracturing induction scheme. This invention can accurately measure the resonant frequency of the target rock sample under the influence of the orifice diameter, and achieve precise measurement of the fracturing initiation pressure and fracturing azimuth of the target rock sample under the action of resonant frequency and resonant excitation time, thereby enabling accurate formulation of a fracture induction scheme under resonant excitation and improving the hydraulic fracturing effect of unconventional oil and gas reservoirs.

Description

Technical Field

[0001] This invention relates to the field of unconventional oil and gas reservoir stimulation technology, and in particular to a method and apparatus for hydraulic fracturing of rocks under resonant excitation. Background Technology

[0002] When reservoir rocks are subjected to external excitation (resonance excitation) at a frequency comparable to their natural frequency, resonance occurs. At this point, the rock amplitude reaches its peak, and microfractures within the rock easily develop, expand, and connect, resulting in a significant decrease in rock strength (fracture initiation pressure). In other words, resonance excitation has a weakening effect on rock strength. Therefore, resonance excitation is a potential means to improve the hydraulic fracturing effect in unconventional oil and gas reservoirs. Accurately determining the rock resonance frequency under the influence of orifice diameter, as well as the hydraulic fracture initiation pressure and initiation orientation at the resonance excitation time, can provide a data foundation for studying the fracture induction mechanism under resonance excitation, thereby potentially increasing the production of unconventional oil and gas.

[0003] However, the inherent frequency of rocks and its evolution mechanism are still unclear. Existing technologies cannot achieve precise measurement of rock resonance frequency, hydraulic fracturing fracture initiation pressure and fracture initiation location under the influence of resonance frequency, resonance excitation time, etc. This results in a lack of reliable data basis for the fracture induction mechanism under resonance excitation, which leads to poor hydraulic fracturing effect in unconventional oil and gas reservoirs and low development efficiency and production of unconventional oil and gas.

[0004] There is currently no effective solution to the above problems. Summary of the Invention

[0005] This specification provides a method and apparatus for hydraulic fracturing of rocks under resonance excitation, in order to solve the problem that the existing technology cannot achieve accurate measurement of rock resonance frequency, hydraulic fracturing fracture initiation pressure and fracture initiation direction under the action of resonance frequency, etc., which leads to a lack of reliable data basis for the fracture induction mechanism under resonance excitation, resulting in poor hydraulic fracturing effect in unconventional oil and gas reservoirs.

[0006] In a first aspect, embodiments of this specification provide a method for hydraulic fracturing of rock under resonant excitation, the method comprising:

[0007] Based on the simulated borehole diameter of the target rock sample, obtain the excitation frequency time series data after applying the excitation frequency to the perforation end face of the target rock sample, and the strain time series data of the other end faces except the perforation end face;

[0008] Based on the strain time series data, the resonance frequency of the target rock sample under the influence of the simulated borehole diameter is determined from the excitation frequency time series data;

[0009] Determine the fracture initiation pressure and fracture initiation orientation of the target rock sample under the resonant frequency and preset resonant excitation time;

[0010] Based on the fracture initiation pressure and fracture initiation location, a fracture induction scheme under resonance excitation is formulated, and hydraulic fracturing is carried out based on the fracture induction scheme.

[0011] In some embodiments, the target rock sample is a cuboid rock sample dried to constant weight, and one perforation end face of the cuboid rock sample is drilled with a simulated hole, and the remaining end faces, excluding the perforation end face, include five non-perforation end faces.

[0012] Accordingly, the method further includes:

[0013] A miniature ultrasonic vibrating rod was placed on one perforation end face of the target rock sample, and corresponding micro-resistance strain sensors were placed on the five non-perforation end faces of the target rock sample.

[0014] After heating the target rock sample to the rock sample temperature, fracturing fluid is injected into the simulated borehole at constant pressure.

[0015] Accordingly, the step of acquiring excitation frequency time-series data after applying the excitation frequency to the perforation end face of the target rock sample, and strain time-series data of the other end faces besides the perforation end face, based on the simulated perforation diameter of the target rock sample, includes:

[0016] When the simulated orifice diameter of the target rock sample is the preset orifice diameter, determine whether the fracturing fluid injection stop condition has been met;

[0017] If so, turn on the miniature ultrasonic vibrator and gradually increase the excitation frequency of the miniature ultrasonic vibrator to obtain excitation frequency timing data, and use the micro-resistance strain sensor to obtain strain timing data of the five non-perforated end faces.

[0018] In some embodiments, determining whether the fracturing fluid injection stop condition has been met includes:

[0019] The transverse relaxation time time series data of the target rock sample is obtained, and the transverse relaxation time time series data is used to determine the water saturation of the target rock sample.

[0020] Determine whether the water saturation of the target rock sample has reached the preset target water saturation.

[0021] If so, stop injecting fracturing fluid at constant pressure.

[0022] In some embodiments, determining the resonant frequency of the target rock sample under the influence of the simulated borehole diameter from the excitation frequency time series data based on the strain time series data includes:

[0023] Determine the average value of the strain time series data for the five perforated end faces;

[0024] The average value of the target strain time series data is selected from the average values ​​of the strain time series data, wherein the average value of the target strain time series data is greater than a preset average value threshold.

[0025] The time corresponding to the average value of the target strain time series data is determined as the resonance excitation time;

[0026] The excitation frequency corresponding to the resonance excitation time is determined from the excitation frequency time series data and used as the resonance frequency of the target rock sample.

[0027] In some embodiments, the resonant frequencies of the target rock sample include:

[0028] When the simulated aperture diameter of the target rock sample is a preset aperture diameter, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at a preset target water saturation level.

[0029] When the simulated aperture diameter of the target rock sample is the inherent aperture diameter, the target water saturation of the target rock sample corresponding to the resonance excitation time is determined. Accordingly, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at the target water saturation.

[0030] In some embodiments, determining the fracture initiation pressure of the target rock sample at the resonance frequency and the preset resonance excitation time includes:

[0031] Fracturing fluid is injected into the simulated hole at the perforation end face of the target rock sample under constant pressure. When the injection time reaches the preset resonance excitation time, the micro ultrasonic vibrator is turned on and the excitation frequency of the micro ultrasonic vibrator is adjusted to the resonance frequency of the target rock sample, thus converting the constant pressure mode to the constant flow mode.

[0032] Fracturing fluid was injected into a simulated hole at the perforation end face of the target rock sample in a constant flow manner until the target rock sample fractured, and pumping pressure timing data was obtained.

[0033] The target pumping pressure time series data in the pumping pressure time series data is determined as the fracture initiation pressure of the target rock sample. The pressure value of the target pumping pressure time series data is greater than a preset pressure threshold.

[0034] In some embodiments, determining the fracture initiation orientation of the target rock sample at the resonance frequency and the preset resonance excitation time includes:

[0035] After the target rock sample fractures, a CT scan is performed on the fractured target rock sample to obtain a three-dimensional image of the target rock sample.

[0036] The three-dimensional image is reconstructed in three dimensions to obtain the fracture initiation orientation of the target rock sample based on the result of the three-dimensional reconstruction.

[0037] Secondly, embodiments of this specification also provide a rock hydraulic fracturing device under resonant excitation, the device comprising:

[0038] The acquisition module is used to acquire the excitation frequency time series data after applying the excitation frequency to the perforation end face of the target rock sample, and the strain time series data of the other end faces except the perforation end face, based on the simulated hole diameter of the target rock sample.

[0039] The resonance frequency determination module is used to determine the resonance frequency of the target rock sample under the influence of the simulated borehole diameter from the excitation frequency time series data based on the strain time series data.

[0040] The crack initiation pressure and crack initiation orientation determination module is used to determine the crack initiation pressure and crack initiation orientation of the target rock sample under the resonance frequency and preset resonance excitation time.

[0041] The hydraulic fracturing module is used to formulate a fracture induction scheme under resonance excitation based on the fracture initiation pressure and fracture initiation location, so as to carry out hydraulic fracturing based on the fracture induction scheme.

[0042] Thirdly, embodiments of this specification also provide a computer device, including a memory, a processor, and a computer program / instructions stored in the memory, wherein the processor executes the computing program / instructions to implement the steps of the above-described rock hydraulic fracturing method under resonant excitation.

[0043] Fourthly, embodiments of this specification also provide a computer-readable storage medium storing a computer program / instructions thereon, which, when executed by a processor, implement the steps of the above-described rock hydraulic fracturing method under resonant excitation.

[0044] Fifthly, embodiments of this specification also provide a computer program product, wherein when the computer program / instructions are executed by a processor, the steps of the rock hydraulic fracturing method under resonant excitation described above are implemented.

[0045] This specification provides a method and apparatus for hydraulic fracturing rocks under resonant excitation. First, based on the simulated orifice diameter of the target rock sample, excitation frequency time-series data and strain time-series data for the remaining facets (excluding the perforation face) are obtained after applying an excitation frequency to the perforation face of the target rock sample. Then, based on the strain time-series data, the resonant frequency of the target rock sample under the influence of the simulated orifice diameter is determined from the excitation frequency time-series data. Next, the fracturing initiation pressure and fracturing azimuth of the target rock sample under the resonant frequency and a preset resonant excitation time are determined. Finally, based on the fracturing initiation pressure and fracturing azimuth, a fracture induction scheme under resonant excitation is formulated, and hydraulic fracturing is performed based on this scheme. This scheme allows for accurate measurement of the resonant frequency of the target rock sample under the influence of the orifice diameter, achieving precise measurement of the fracturing initiation pressure and fracturing azimuth of the target rock sample under the influence of the resonant frequency and resonant excitation time. This enables the accurate formulation of a fracture induction scheme under resonant excitation, improving the hydraulic fracturing effect in unconventional oil and gas reservoirs. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0047] Figure 1 This is a schematic flowchart of a rock hydraulic fracturing method under resonant excitation provided in one embodiment of this specification;

[0048] Figure 2 This is a schematic diagram of an embodiment of a rock hydraulic fracturing method under resonant excitation provided in the embodiments of this specification, in a scenario example;

[0049] Figure 3 This is a schematic diagram of an embodiment of a rock hydraulic fracturing method under resonant excitation provided in the embodiments of this specification, in a scenario example;

[0050] Figure 4 This is a schematic diagram of the structural composition of a rock hydraulic fracturing device under resonant excitation, provided in one embodiment of this specification;

[0051] Figure 5 This is a schematic diagram of the structural composition of an electronic device provided in one embodiment of this specification. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0053] Reservoir rocks are complexes composed of rock matrix, pores, and microfractures, and their strength is affected by factors such as geostress, temperature, and seepage. Under the influence of external forces or environmental changes, microfractures within the rock initiate and expand into large cracks, ultimately weakening the rock's strength. When a rock is subjected to external excitation (resonance excitation) at its natural frequency (resonance frequency), resonance occurs. At this point, the rock amplitude reaches its peak, and microfractures within the rock easily develop, expand, and connect, causing a significant decrease in rock strength. Therefore, resonance excitation has a certain weakening effect on rock strength. The main principle is that when a rock is subjected to excitation at its natural frequency, resonance occurs. This causes relatively severe damage to the rock's interior within a short period, and the rock strength decreases rapidly as the damage intensifies. Therefore, resonance excitation is a potential means to improve the hydraulic fracturing effect in unconventional oil and gas reservoirs. Accurately determining the resonance frequency of the rock under the influence of orifice diameter, as well as the hydraulic fracture initiation pressure and initiation orientation at the resonance excitation time, can provide a data foundation for studying the fracture induction mechanism under resonance excitation, thereby potentially increasing the production of unconventional oil and gas.

[0054] However, the inherent frequency of rocks and its evolution mechanism are still unclear. Existing technologies cannot achieve precise measurement of rock resonance frequency, hydraulic fracturing fracture initiation pressure and fracture initiation location under the influence of resonance frequency, resonance excitation time, etc. This results in a lack of reliable data basis for the fracture induction mechanism under resonance excitation, which leads to poor hydraulic fracturing effect in unconventional oil and gas reservoirs and low development efficiency and production of unconventional oil and gas.

[0055] In view of the above-mentioned problems of existing methods and the specific reasons for these problems, this application proposes to introduce a rock hydraulic fracturing method and apparatus under resonance excitation. This method can accurately measure the fracturing pressure and fracturing orientation of the target rock sample under the action of resonance frequency and resonance excitation time. This allows for the accurate formulation of a fracture induction scheme under resonance excitation, thereby improving the hydraulic fracturing effect of unconventional oil and gas reservoirs.

[0056] Based on the above approach, this specification proposes a method for hydraulic fracturing of rocks under resonant excitation. First, based on the simulated borehole diameter of the target rock sample, excitation frequency time-series data and strain time-series data for the remaining facets (excluding the perforation face) are obtained after applying the excitation frequency to the perforation face of the target rock sample. Then, based on the strain time-series data, the resonant frequency of the target rock sample under the influence of the simulated borehole diameter is determined from the excitation frequency time-series data. Next, the fracturing initiation pressure and fracturing inclination of the target rock sample at the resonant frequency and a preset resonant excitation time are determined. Finally, based on the fracturing initiation pressure and fracturing inclination, a fracture induction scheme under resonant excitation is formulated for hydraulic fracturing.

[0057] Figure 1 This is a schematic flowchart of a rock hydraulic fracturing method under resonant excitation provided in the embodiments of this specification. Although this specification provides method operation steps or apparatus structures as shown in the following embodiments or figures, based on conventional or non-inventive effort, the method or apparatus may include more or fewer operation steps or module units after partial combination. In steps or structures where there is no logically necessary causal relationship, the execution order of these steps or the module structure of the apparatus is not limited to the execution order or module structure shown in the embodiments or figures of this specification. When the method or module structure is applied in actual devices, servers, or terminal products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or figures (e.g., in a parallel processor or multi-threaded processing environment, or even in a distributed processing or server cluster implementation environment). For specific implementation, please refer to... Figure 1 As shown, the method may include the following:

[0058] S101: Based on the simulated borehole diameter of the target rock sample, obtain the excitation frequency timing data after applying the excitation frequency to the perforation end face of the target rock sample, and the strain timing data of the other end faces except the perforation end face.

[0059] In some embodiments, the target rock sample in S101 above can be a cuboid rock sample dried to constant weight, and one perforation end face of the cuboid rock sample is drilled with a simulated hole, and the other end faces besides the perforation end face can include 5 non-perforation end faces.

[0060] Accordingly, prior to S101 above, in specific implementation, it may also include:

[0061] S11: A miniature ultrasonic vibrating rod is arranged on one perforation end face of the target rock sample, and corresponding micro-resistance strain sensors are arranged on the five non-perforation end faces of the target rock sample.

[0062] S12: After heating the target rock sample to the rock sample temperature, inject fracturing fluid into the simulated borehole at constant pressure;

[0063] Accordingly, in S101 above, obtaining the excitation frequency timing data after applying the excitation frequency to the perforation end face of the target rock sample, and the strain timing data of the other end faces besides the perforation end face, based on the simulated perforation diameter of the target rock sample, may, in specific implementation, include:

[0064] S13: When the simulated orifice diameter of the target rock sample is the preset orifice diameter, determine whether the fracturing fluid injection stop condition has been met;

[0065] S14: If so, turn on the micro ultrasonic vibrator and gradually increase the excitation frequency of the micro ultrasonic vibrator to obtain excitation frequency timing data, and use the micro resistance strain sensor to obtain strain timing data of the five non-perforated end faces.

[0066] In some embodiments, the determination of whether the fracturing fluid injection stop condition has been met in S13 above may, in specific implementation, include:

[0067] S131: Obtain the transverse relaxation time time series data of the target rock sample, the transverse relaxation time series data being used to determine the water saturation of the target rock sample;

[0068] S132: Determine whether the water saturation of the target rock sample has reached the preset target water saturation;

[0069] S133: If so, stop injecting fracturing fluid at constant pressure.

[0070] In some embodiments, the target rock sample mentioned above can be a rock sample corresponding to near-perforated rock (near-perforated dense rock). Near-perforated rock refers to the rock whose pore structure and permeability change due to the action of explosion pressure and impact force during the perforation operation. Large pores are destroyed and microcracks may be filled with particle fragments. After the perforation operation, the physical properties and structural characteristics of this rock have changed compared with the original state, and it is called near-perforated rock.

[0071] The target rock sample can be a cuboid rock sample dried to constant weight at a certain temperature (e.g., 60℃). The length and width of the cuboid rock sample can be 8cm and the height can be 10cm. The target rock sample has a total of 6 end faces, one of which can be a perforated end face (a square end face with a length and width of 8cm, such as the upper end face of the cuboid rock sample). The remaining end faces can be 5 non-perforated end faces. A simulated hole can be drilled in the center of the perforated end face.

[0072] When the diameter of the simulated orifice is a preset diameter (e.g., d mm, the preset diameter can be set according to actual needs, this manual does not make a specific limitation, the length of the simulated orifice can be 4 cm), a simulated wellbore with a length of 3 cm and an outer diameter of d mm can be prepared using steel with the same wall thickness and steel grade as the cementing casing. After the simulated wellbore is fixed to the simulated orifice, the rock sample is dried at 60°C to constant weight, and the target rock sample is obtained as described above.

[0073] When the diameter of the simulated wellbore is the inherent diameter (e.g., 10 mm, the length of the simulated wellbore can be 4 cm), a simulated wellbore with a length of 3 cm and an outer diameter of 10 mm can be prepared using steel with the same wall thickness and steel grade as the cementing casing. After the simulated wellbore is cemented into the simulated wellbore, the rock sample is dried at 60°C to constant weight, thus obtaining the target rock sample mentioned above.

[0074] In some embodiments, a miniature ultrasonic vibrator can be arranged on one perforation end face of the target rock sample to apply triaxial stress to the six end faces of the target rock sample. Corresponding micro-resistance strain sensors can be arranged on each of the five non-perforation end faces of the target rock sample (i.e., one micro-resistance strain sensor is arranged on each non-perforation end face). The target rock sample can be heated to the rock sample temperature required for fracturing, and then fracturing fluid can be injected into the simulated perforation at constant pressure to ensure that the temperature of the injected fracturing fluid, the rock sample temperature, and the fracturing fluid temperature and reservoir rock temperature at the corresponding reservoir depth are consistent. By heating the target rock sample to its rock sample temperature before injecting fracturing fluid for fracturing, the fracturing process under geothermal conditions can be simulated, allowing for a more accurate study of fracturing effects and fracture propagation mechanisms.

[0075] When the simulated perforation diameter of the target rock sample is the preset perforation diameter, it can be determined whether the fracturing fluid injection cessation condition has been met. If the fracturing fluid injection cessation condition has been met (if so), the micro ultrasonic vibrator is turned on and the excitation frequency f of the micro ultrasonic vibrator is gradually increased. The time series data f(t) of the excitation frequency is recorded or acquired. The strain time series data ε of the five non-perforated end faces is measured or acquired using a micro-resistance strain sensor. i (t)(i=1,2,3,4,5). If the fracturing fluid injection cessation condition is not met (if not), continue injecting fracturing fluid at constant pressure until the fracturing fluid injection cessation condition is met.

[0076] In some embodiments, whether the fracturing fluid injection cessation condition is met is determined by: whether the water saturation Sw(t) of the target rock sample reaches the preset target water saturation Sw. target If the preset target water saturation level Sw is reached target This means that the fracturing fluid injection is stopped when the pre-set target water saturation level Sw is not reached. targetThis means the fracturing fluid injection stop condition has not been met. Specifically, a target water saturation level Sw can be set first. target (That is, the preset target water saturation, which can be set according to actual needs; this instruction manual does not specify a particular limit on it.) Then, the transverse relaxation time series data T2(t) of the target rock sample is measured using a nuclear magnetic resonance (NMR) device. The water saturation Sw(t) of the target rock sample is calculated based on the transverse relaxation time series data T2(t). Finally, it is determined whether the water saturation Sw(t) of the target rock sample reaches or is equal to the preset target water saturation Sw. target If (Sw(t) = Sw) target Stop injecting fracturing fluid at constant pressure.

[0077] The transverse relaxation time (T2(t)) reflects the relaxation characteristics of fluids (such as water, oil, or gas) in rock pores and is closely related to the rock's pore structure, fluid type, and saturation. By measuring and analyzing the T2(t) distribution, the water saturation of a rock sample can be indirectly inferred. The T2(t) distribution of rocks is usually obtained through nuclear magnetic resonance (NMR) logging or laboratory NMR measurements. Different fluid types and pore sizes lead to different T2(t) values. For example, water typically has a shorter T2(t) time, while oil and gas may have longer T2(t) times, but this also depends on the geometry and connectivity of the pores.

[0078] In some embodiments, the step S101 above, which involves obtaining the excitation frequency time series data after applying the excitation frequency to the perforation end face of the target rock sample based on the simulated perforation diameter of the target rock sample, and the strain time series data of the other end faces besides the perforation end face, may further include:

[0079] When the simulated aperture diameter of the target rock sample is the inherent aperture diameter (e.g., 10 mm), the micro ultrasonic vibrator is turned on and the excitation frequency f is gradually increased to obtain the excitation frequency time series data f(t). The strain time series data ε of the five perforated end faces is obtained using the micro-resistance strain sensor. i (t)(i=1,2,3,4,5).

[0080] By obtaining the excitation frequency timing data after applying the excitation frequency to the perforation end face of the target rock sample based on the simulated perforation diameter, as well as the strain timing data of the other end faces besides the perforation end face, we can lay the foundation for accurately determining or measuring the resonance frequency of the target rock sample under the influence of the perforation (simulated perforation) diameter.

[0081] S102: Based on the strain time series data, determine the resonance frequency of the target rock sample under the influence of the simulated aperture diameter from the excitation frequency time series data.

[0082] In some embodiments, determining the resonance frequency of the target rock sample under the influence of the simulated aperture diameter from the excitation frequency time series data based on the strain time series data in S102 above may, in specific implementation, include:

[0083] S21: Determine the average value of the strain time series data for the five perforated end faces;

[0084] S22: Select the average value of the target strain time series data from the average value of the strain time series data, wherein the average value of the target strain time series data is greater than a preset average value threshold;

[0085] S23: Determine the time corresponding to the average value of the target strain time series data as the resonance excitation time;

[0086] S24: Determine the excitation frequency corresponding to the resonance excitation time from the excitation frequency time series data, and use it as the resonance frequency of the target rock sample.

[0087] In some embodiments, the resonance frequency of the target rock sample in S24 above may include:

[0088] When the simulated aperture diameter of the target rock sample is a preset aperture diameter, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at a preset target water saturation level.

[0089] When the simulated aperture diameter of the target rock sample is the inherent aperture diameter, the target water saturation of the target rock sample corresponding to the resonance excitation time is determined. Accordingly, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at the target water saturation.

[0090] In some embodiments, strain time series data ε of the five perforation-free end faces can be calculated or determined. i The average value ε(t) of strain time series data (i = 1, 2, 3, 4, 5) is then used to select the average value of the target strain time series data from the average values ​​ε(t) of the strain time series data (the average value ε(t) of the strain time series data can be compared with a preset average value threshold to select the average value of the target strain time series data based on the comparison result). The average value of the target strain time series data is greater than the preset average value threshold (the preset average value threshold can be set according to actual needs, and this manual does not specify a specific limit for it), that is, the maximum value ε of the average value of the strain time series data is selected. max (t sym Then determine the average value ε of the target strain time series data. max (t sym The corresponding time t sym The resonant excitation time t is taken as the resonant excitation time. Finally, the resonant excitation time t can be determined from the excitation frequency timing data f(t). symThe corresponding excitation frequency f(t) sym The resonant frequency f(t) of the target rock sample is determined by the pre-set aperture diameter (dmm) of the simulated aperture in the target rock sample. sym This refers to the target rock sample at the preset target water saturation level Sw. target The resonant frequency (or fixed frequency) is determined. When the simulated pore diameter of the target rock sample is the inherent pore diameter (e.g., 10 mm), the resonant excitation time t is determined. sym The target water saturation Sw(t) of the corresponding target rock sample sym The resonance frequency f(t) of the target rock sample sym This refers to the target rock sample at the target water saturation level Sw(t). sym The resonant frequency (or fixed frequency) under ).

[0091] By determining whether the simulated pore diameter of the target rock sample is a preset pore diameter or an inherent pore diameter, and then defining the resonance frequency of the target rock sample, the resonance frequency of the target rock sample under the influence of different water saturation (liquid phase saturation) / pore diameter can be accurately determined. This lays the foundation for the subsequent accurate measurement of key data such as resonance frequency, hydraulic fracture initiation pressure, and fracture initiation orientation under the action of resonance excitation time.

[0092] In some embodiments, when the diameter of the simulated borehole drilled on the perforation end face of the target rock sample is 10 mm and the length is 4 cm, the target rock sample can be heated to its temperature, and fracturing fluid can be injected into the simulated borehole at constant pressure. Then, a micro-ultrasonic vibrator is turned on and the excitation frequency f is gradually increased. The time series data f(t) of the excitation frequency is recorded or acquired. Simultaneously, the transverse relaxation time time series data T2(t) of the target rock sample is measured using nuclear magnetic resonance (NMR) or a nuclear magnetic resonance (NMR) device. The water saturation Sw(t) of the target rock sample is calculated based on the transverse relaxation time series data T2(t). The strain time series data ε of five non-perforation end faces is measured or acquired using a micro-resistance strain sensor. i (t)(i=1,2,3,4,5). Calculate or determine the strain time series data ε for the five perforated end faces. i The average value ε(t) of the strain time series data (i = 1, 2, 3, 4, 5) is selected, and the maximum value ε of the average value of the strain time series data is chosen. max (t sym Then determine t. sym The target water saturation Sw(t) of the corresponding target rock sample sym ) and t sym The corresponding excitation frequency f(t) sym At this point, f(t) can be used. sym ) as the target rock sample at the target water saturation Sw(t) symThe resonant frequency (or fixed frequency) under ).

[0093] In some embodiments, the resonance frequency of the target rock sample in S24 above can be specifically determined by the following formula:

[0094]

[0095] f sym =f(t) sym (2)

[0096] Among them, t sym For resonance excitation time; To achieve resonance, the strain (i.e., the average value of the target strain time series data mentioned above); max is the maximum value operator; The sum of strain time series data for the five perforation-free end faces; ∈ i (t) represents the strain time series data (i.e., strain variation with time t) for i non-perforated end faces; f sym f(t) represents the resonance frequency of the target rock sample. sym To achieve resonance excitation time t sym The corresponding excitation frequency.

[0097] In some embodiments, the resonance frequency of the target rock sample at the target water saturation can be determined by the following formula:

[0098]

[0099] f res (s w )=f(t sym (4)

[0100] Among them, Sw(t) sym ) represents the resonance excitation time t sym The target water saturation of the corresponding target rock sample; T2 is the transverse relaxation time; max is the maximum value operator; A sw (t sym ) represents the resonance excitation time t sym The nuclear magnetic resonance signal intensity below; A swsat f represents the nuclear magnetic resonance signal intensity of a water-saturated rock sample; res (s w ) represents the target water saturation level Sw(t) sym The resonant frequency under ); f(t) sym To achieve resonance excitation time t sym The corresponding excitation frequency.

[0101] In some embodiments, the water saturation Sw(t) of the target rock sample calculated based on the transverse relaxation time time series data T2(t) can also be obtained using the above formula (3). In this case, Sw(t) in formula (3) is... sym Replace ) with Sw(t), and replace T2 in formula (3) with T2(t).

[0102] S103: Determine the fracture initiation pressure and fracture initiation orientation of the target rock sample under the resonance frequency, preset resonance excitation time, and the time of the resonance.

[0103] In some embodiments, determining the resonance frequency and the crack initiation pressure of the target rock sample under the preset resonance excitation time in S103 above may, in specific implementation, include:

[0104] S31: Inject fracturing fluid into the simulated hole at the perforation end face of the target rock sample in a constant pressure manner. When the injection time reaches the preset resonance excitation time, turn on the micro ultrasonic vibrator and adjust the excitation frequency of the micro ultrasonic vibrator to the resonance frequency of the target rock sample, and switch the constant pressure mode to the constant flow mode.

[0105] S32: Inject fracturing fluid into the simulated hole at the perforation end face of the target rock sample in a constant flow manner until the target rock sample fractures, and obtain pumping pressure timing data;

[0106] S33: Determine the target pumping pressure time series data in the pumping pressure time series data as the crack initiation pressure of the target rock sample, wherein the pressure value of the target pumping pressure time series data is greater than a preset pressure threshold.

[0107] In some embodiments, a preset rock sample temperature T can be set first. target Preset resonance excitation time t sym-target Then, the preset rock sample temperature, preset resonance excitation time (when the preset resonance excitation time is reached, i.e., the target rock sample reaches the preset target water saturation), and the initiation pressure and initiation direction under the aforementioned resonance frequency are measured. The initiation direction will be explained separately later and will not be repeated here. Among these, the preset rock sample temperature T... target Preset resonance excitation time t sym-target It can be set according to actual needs; this manual does not impose specific limitations on it.

[0108] Specifically, the target rock sample can be heated to a preset rock sample temperature T. target At that time, fracturing fluid is injected into the simulated hole at the perforation end face of the target rock sample under constant pressure, until the injection time reaches the preset resonance excitation time t. sym-target At this time, turn on the miniature ultrasonic vibrator and adjust the excitation frequency of the miniature ultrasonic vibrator to the resonance frequency f(t) of the target rock sample. symThe constant pressure mode is converted to a constant flow mode (i.e., the constant pressure injection mode or method is converted to a constant flow injection mode). Then, fracturing fluid is injected into the simulated orifice at the perforation end face of the target rock sample in a constant flow mode until the target rock sample fractures. Pump pressure time series data P(t) is recorded or acquired. The target pump pressure time series data is then determined (the pump pressure time series data can be compared with a preset pressure threshold to determine the target pump pressure time series data based on the comparison result). If the pressure value of the target pump pressure time series data is greater than the preset pressure threshold (the preset pressure threshold can be set according to actual needs; this specification does not specify a particular threshold), then the maximum value P in the pump pressure time series data is determined. max (t), P max (t) represents the initiation pressure of the target rock sample fracture (hydraulic fracture).

[0109] By switching from a constant-pressure injection mode to a constant-flow injection mode for fracturing fluid, the fracturing process can be controlled more effectively, ensuring a stable flow rate of the fracturing fluid and thus better controlling fracture development and propagation. In fracturing operations, the injection method of the fracturing fluid has a significant impact on fracture formation and propagation. While the traditional constant-pressure injection mode is simple and easy to implement, it cannot precisely control the morphology and orientation of fractures. In contrast, the constant-flow injection mode, by maintaining a constant flow rate, can better manage the fracture propagation process and avoid irregular fracture development caused by pressure fluctuations. Under constant-flow injection mode, the formation and propagation of fractures can be monitored in real time by recording the pump pressure time-series data P(t).

[0110] In some embodiments, determining the fracture initiation orientation of the target rock sample under the preset resonance excitation time in S103 above may, in specific implementation, include:

[0111] S34: After the target rock sample is fractured, a CT scan is performed on the fractured target rock sample to obtain a three-dimensional image of the target rock sample;

[0112] S35: Perform three-dimensional reconstruction on the three-dimensional image to obtain the fracture initiation orientation of the target rock sample based on the result of the three-dimensional reconstruction.

[0113] In some embodiments, after the target rock sample fractures, a CT scan can be performed on the fractured target rock sample (CT scanning technology can acquire information about the internal structure of the rock sample) to obtain a high-resolution three-dimensional image (the three-dimensional image can show the distribution, morphology, and relationship of the fractures in the target rock sample to the wellbore end face). The three-dimensional image is then reconstructed in three dimensions. Based on the results of the three-dimensional reconstruction, the geometric characteristics of the fractures can be further analyzed, including the angle α between the fracture and the vertical wellbore end face and the angle β between the fracture and the wellbore end face, which serves as the initiation orientation of the fractures (hydraulic fractures) in the target rock sample.

[0114] By setting preset rock sample temperature and preset resonance excitation time, the hydraulic fracture initiation pressure and fracture initiation direction under the preset rock sample temperature, preset resonance excitation time and target rock sample resonance frequency can be accurately and comprehensively obtained, which can provide a good experimental basis or data basis for subsequent research on fracture induction mechanism under resonance excitation.

[0115] S104: Based on the fracture initiation pressure and fracture initiation location, formulate a fracture induction scheme under resonance excitation, so as to carry out hydraulic fracturing based on the fracture induction scheme.

[0116] In some embodiments, the above-mentioned resonant excitation can be an external excitation on the target rock sample that is equivalent to its natural frequency (resonant frequency), referred to as resonant excitation.

[0117] In some embodiments, after determining the resonance frequency of the target rock sample under the influence of the pore diameter, resonance excitation can be applied to the target rock sample. Resonance excitation can reduce the fracture initiation pressure and control the fracture initiation orientation to make the fracture more complex, thereby increasing the production of unconventional oil and gas.

[0118] In some embodiments, a fracture induction scheme under resonance excitation can be formulated based on the fracture initiation pressure and fracture initiation orientation, and then hydraulic fracturing can be carried out based on the fracture induction scheme to improve the hydraulic fracturing effect of unconventional oil and gas reservoirs, thereby achieving increased production and efficiency of unconventional oil and gas.

[0119] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. For details, please refer to the foregoing descriptions of the relevant processing embodiments; they will not be repeated here.

[0120] The foregoing description of this method is for illustrative purposes only and describes specific embodiments. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than those shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0121] The above method will be described below with reference to a specific embodiment. However, it is worth noting that this specific embodiment is only for better illustration of this application and does not constitute an improper limitation of this application.

[0122] Before implementation, prepare a cuboid rock sample with sides of 8cm, width, and height of 10cm. Drill a simulated borehole with a fixed diameter of 10mm or a preset borehole diameter of dmm and a length of 4cm at the center of the 8cm×8cm end face. When the simulated borehole diameter is the preset diameter, the length of the simulated borehole can be 4cm. A simulated wellbore with a length of 3cm and an outer diameter of dmm can be prepared using steel with the same wall thickness and steel grade as the cementing casing. After fixing this simulated wellbore to the simulated borehole, the rock sample is dried at 60℃ to constant weight to obtain the target rock sample. When the simulated borehole diameter is the fixed diameter, a simulated wellbore with a length of 3cm and an outer diameter of 10mm can be prepared using steel with the same wall thickness and steel grade as the cementing casing. After fixing this simulated wellbore to the simulated borehole, the rock sample is dried at 60℃ to constant weight to obtain the target rock sample. The target rock sample has six end faces: one perforated end face and five non-perforated end faces. A miniature ultrasonic vibrator can be placed on the one perforated end face of the target rock sample, and a micro-resistance strain sensor can be placed on each of the five non-perforated end faces of the target rock sample.

[0123] In practice, after heating the target rock sample to its target temperature, fracturing fluid is injected into the simulated orifice at constant pressure. When the diameter of the simulated orifice in the target rock sample is the preset orifice diameter, it is determined whether the fracturing fluid injection stop condition has been met. If the fracturing fluid injection stop condition has been met, the micro-ultrasonic vibrator is activated and its excitation frequency is gradually increased to acquire excitation frequency timing data. The strain timing data of the five perforation-free end faces is acquired using the micro-resistance strain sensor. When the diameter of the simulated orifice is the inherent diameter, the micro-ultrasonic vibrator is activated and its excitation frequency is gradually increased to acquire excitation frequency timing data. The strain timing data of the five perforation-free end faces is acquired using the micro-resistance strain sensor. Then, the average value of the strain timing data of the five perforation-free end faces is calculated or determined. The maximum value of the average strain timing data is then selected from the average values, and the time corresponding to the maximum value of the average strain timing data is determined as the resonance excitation time. Finally, the excitation frequency corresponding to the resonance excitation time is determined as the resonance frequency of the target rock sample. When the simulated aperture diameter of the target rock sample is the preset aperture diameter, the resonance frequency of the target rock sample is the resonance frequency (or fixed frequency) of the target rock sample at the preset target water saturation. When the simulated aperture diameter of the target rock sample is the inherent aperture diameter, the target water saturation of the target rock sample corresponding to the resonance excitation time is determined, and the resonance frequency of the target rock sample is the resonance frequency (or fixed frequency) of the target rock sample at the target water saturation. Then, the fracture initiation pressure and fracture initiation orientation of the target rock sample at the resonance frequency and preset resonance excitation time are determined. Based on the fracture initiation pressure and fracture initiation orientation, a fracture induction scheme under resonance excitation is formulated, and hydraulic fracturing is performed based on the fracture induction scheme.

[0124] The above method can accurately measure key data such as the natural frequency of rock samples, hydraulic fracture initiation pressure and fracture initiation orientation under the action of resonance excitation time. It can provide an experimental basis for studying the fracture induction mechanism under resonance excitation, and thus improve the hydraulic fracturing effect of unconventional oil and gas reservoirs.

[0125] In a specific implementation scenario, the steps for determining the resonant frequency of a rock sample under the influence of liquid phase saturation / pore diameter are as follows (in this case, the simulated pore size is directly 10 mm):

[0126] (1) See Figure 2 As shown, a rectangular rock sample with a length and width of 8cm and a height of 10cm was prepared, and a simulated hole with a diameter of 10mm and a length of 4cm was drilled in the center of the square end face with a side length of 8cm.

[0127] (2) A simulated wellbore (simulated casing steel sheet) with a length of 3cm and an outer diameter of 10mm was prepared using steel with the same wall thickness and steel grade as the cementing casing. After the simulated wellbore was solidified into the simulated hole, the rock sample was dried at 60℃ to constant weight.

[0128] (3) See Figure 2 As shown, micro-resistance strain sensors were arranged on the remaining five perforation-free end faces of the rock sample, and micro-ultrasonic vibrators were arranged on the plane of the perforation end faces. Triaxial stress was applied to the six end faces of the rock sample. After heating to the rock sample temperature at the time of fracturing, fracturing fluid was injected into the perforation in a constant pressure manner to ensure that the temperature of the injected fracturing fluid and the rock sample were consistent with the temperature of the fracturing fluid and the temperature of the reservoir rock at the corresponding reservoir depth.

[0129] (4) Turn on the miniature ultrasonic vibrator, gradually increase the excitation frequency f, and record the time series data of the excitation frequency f(t). At the same time, use a nuclear magnetic resonance (NMR) device to measure the transverse relaxation time T2(t) of the rock sample, and use a miniature resistance strain gauge to measure the strain time series data ε of the five non-perforated end faces of the rock sample. i (t)(i=1,2,3,4,5);

[0130] (5) Calculate the water saturation Sw(t) of the target rock sample based on the transverse relaxation time time series data T2(t), and calculate the strain time series data ε of the five perforation-free end faces. i (t)(i=1,2,3,4,5) Calculate the time series data ε of rock sample strain. i Given the average value ε(t) of the set of t (i = 1, 2, 3, 4), find the maximum value ε(t). max (t sym Then determine t. sym The target water saturation Sw(t) of the corresponding rock sample sym ) and t symThe corresponding excitation frequency f(t) sym Then f(t) can be used as a delimiter for f(t). sym ) as the target rock sample at the target water saturation Sw(t) sym The resonant frequency (or fixed frequency) under ).

[0131] The steps for determining the resonant frequency of a rock sample under the influence of liquid phase saturation / pore diameter are as follows (at this time, the simulated pore diameter is d mm, and the preset target water saturation Sw is set). target It can be set according to actual needs, that is, it can measure the resonance frequency of rock samples under different water saturation and pore diameter conditions:

[0132] (1) See Figure 2 As shown, a rectangular rock sample with a length and width of 8cm and a height of 10cm was prepared, and a simulated hole with a diameter of dmm and a length of 4cm was drilled in the center of the square end face with a side length of 8cm.

[0133] (2) A simulated wellbore (simulated casing steel sheet) with a length of 3cm and an outer diameter of dmm was prepared using steel with the same wall thickness and steel grade as the cementing casing. After the simulated wellbore was solidified into the simulated hole, the rock sample was dried at 60℃ to constant weight.

[0134] (3) See Figure 2 As shown, micro-resistance strain sensors were arranged on the remaining five perforation-free end faces of the rock sample, and micro-ultrasonic vibrators were arranged on the plane of the perforation end faces. Triaxial stress was applied to the six end faces of the rock sample. After heating to the rock sample temperature at the time of fracturing, fracturing fluid was injected into the perforation in a constant pressure manner to ensure that the temperature of the injected fracturing fluid and the rock sample were consistent with the temperature of the fracturing fluid and the temperature of the reservoir rock at the corresponding reservoir depth.

[0135] (4) Set the preset target water saturation level Sw target The transverse relaxation time time series data T2(t) of the rock sample was measured using a nuclear magnetic resonance (NMR) device. The water saturation Sw(t) of the target rock sample was calculated based on the transverse relaxation time series data T2(t). When Sw(t) = Sw target When this occurs, stop injecting fracturing fluid at constant pressure;

[0136] (5) Turn on the miniature ultrasonic vibrator, gradually increase the excitation frequency f, and record the time series data of the excitation frequency f(t). At the same time, use a nuclear magnetic resonance (NMR) device to measure the transverse relaxation time T2(t) of the rock sample, and use a miniature resistance strain gauge to measure the strain time series data ε of the five non-perforated end faces of the rock sample. i (t)(i=1,2,3,4,5);

[0137] (6) Based on the strain time series data ε of the five perforated end faces i(t)(i=1,2,3,4,5) Calculate the time series data ε of rock sample strain. i Find the average value ε(t) of the set (i = 1, 2, 3, 4, 5), and find the maximum value ε(t). max (t sym Then determine t. sym The corresponding excitation frequency f(t) sym Then f(t) can be used as a delimiter for f(t). sym As a rock sample (pore diameter d mm), at the target water saturation Sw target The resonant frequency (or fixed frequency) below.

[0138] The steps for setting the fracturing fluid presaturation time, rock sample temperature, resonance excitation time, and resonance frequency, and determining the fracturing initiation pressure and initiation direction are as follows:

[0139] (1) See Figure 3 As shown, a rectangular rock sample with a length and width of 8cm and a height of 10cm was prepared, and a hole with a diameter of 10mm and a length of 6cm was drilled in the center of the 8cm×8cm end face to simulate a well.

[0140] (2) A simulated wellbore with a length of 6 cm and an outer diameter of d mm was prepared using steel with the same wall thickness and steel grade as the cementing casing. After the simulated wellbore was solidified into the simulated borehole, the rock sample was dried at 60°C to constant weight.

[0141] (3) Drill perforation holes in the simulated wellbore at a phase angle of 120 degrees to simulate spiral perforation, such as... Figure 3 As shown.

[0142] (4) See Figure 3 As shown, three miniature ultrasonic vibrating rods were evenly placed on the inner wall of the simulated well barrel, and triaxial stress was applied to the six end faces of the rock sample.

[0143] (5) Set the preset rock sample temperature T target and preset resonance excitation time t sym-target The rock sample was heated to T target Then, fracturing fluid is injected into the borehole at a constant pressure. When the injection time reaches t... sym-target At this time, turn on the miniature ultrasonic vibrator and adjust the excitation frequency to the rock sample resonance frequency f(t). sym The constant pressure injection mode of the fracturing fluid was switched to a constant flow injection mode.

[0144] (6) Switch the fracturing fluid constant pressure injection mode to constant flow injection mode, record the pumping pressure time data P(t) until the rock sample fractures, and calculate the maximum value P(t). max (t), P max (t) represents the crack initiation pressure;

[0145] (7) After the experiment, the rock sample was CT scanned and three-dimensional reconstruction was carried out to obtain the angle α between the crack and the vertical wellbore end face and the angle β between the crack and the wellbore end face, thus determining the crack initiation direction.

[0146] Although this specification provides the following examples or appendices Figure 4 The method or apparatus structure shown may include more or fewer combined operational steps or module units based on conventional or non-inventive methods. In steps or structures where there is no logically necessary causal relationship, the execution order of these steps or the module structure of the apparatus is not limited to the execution order or module structure shown in the embodiments or drawings of this specification. When the method or module structure is applied in actual devices, servers, or terminal products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or drawings (e.g., in a parallel processor or multi-threaded processing environment, or even a distributed processing or server cluster implementation environment). Based on the above-described rock hydraulic fracturing method under resonant excitation, this specification also proposes an embodiment of a rock hydraulic fracturing apparatus under resonant excitation. Figure 4 As shown, the device may specifically include the following modules:

[0147] The acquisition module 401 can be used to acquire the excitation frequency time series data after applying the excitation frequency to the perforation end face of the target rock sample, and the strain time series data of the other end faces except the perforation end face, based on the simulated hole diameter of the target rock sample.

[0148] The resonance frequency determination module 402 can be used to determine the resonance frequency of the target rock sample under the influence of the simulated aperture diameter from the excitation frequency time series data based on the strain time series data.

[0149] The crack initiation pressure and crack initiation orientation determination module 403 can be used to determine the crack initiation pressure and crack initiation orientation of the target rock sample under the resonance frequency and preset resonance excitation time.

[0150] The hydraulic fracturing module 404 can be used to formulate a fracture induction scheme under resonance excitation based on the fracture initiation pressure and fracture initiation orientation, so as to carry out hydraulic fracturing based on the fracture induction scheme.

[0151] In some embodiments, the target rock sample in the acquisition module 401 is a cuboid rock sample dried to constant weight. One perforation end face of the cuboid rock sample is drilled with a simulated hole, and the remaining end faces, excluding the perforation end face, include five non-perforated end faces. Accordingly, the acquisition module 401 can also be used to arrange a micro-ultrasonic vibrator on one perforation end face of the target rock sample and corresponding micro-resistance strain sensors on the five non-perforated end faces of the target rock sample. After heating the target rock sample to the rock sample temperature, fracturing fluid is injected into the simulated hole at constant pressure. Specifically, the acquisition module 401 can be used to determine whether the fracturing fluid injection stop condition has been met when the diameter of the simulated hole in the target rock sample is a preset hole diameter. If so, the micro-ultrasonic vibrator is turned on and its excitation frequency is gradually increased to acquire excitation frequency timing data. The strain timing data of the five non-perforated end faces is acquired using the micro-resistance strain sensors.

[0152] In some embodiments, the acquisition module 401 may also be used to acquire the transverse relaxation time time series data of the target rock sample, the transverse relaxation time series data being used to determine the water saturation of the target rock sample; determine whether the water saturation of the target rock sample has reached a preset target water saturation; if so, stop injecting fracturing fluid in a constant pressure manner.

[0153] In some embodiments, the resonance frequency determination module 402 can be specifically used to determine the average value of strain time series data of five perforation-free end faces; select the average value of target strain time series data from the average value of the strain time series data, wherein the average value of the target strain time series data is greater than a preset average value threshold; determine the time corresponding to the average value of the target strain time series data as the resonance excitation time; and determine the excitation frequency corresponding to the resonance excitation time from the excitation frequency time series data as the resonance frequency of the target rock sample.

[0154] In some embodiments, the resonance frequency determination module 402 may also be used to determine the resonance frequency of the target rock sample at a preset target water saturation when the simulated aperture diameter of the target rock sample is a preset aperture diameter; and to determine the target water saturation of the target rock sample corresponding to the resonance excitation time when the simulated aperture diameter of the target rock sample is an inherent aperture diameter, and accordingly, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at the target water saturation.

[0155] In some embodiments, the fracturing pressure and fracturing orientation determination module 403 can be specifically used to inject fracturing fluid into a simulated orifice on the perforation end face of the target rock sample in a constant pressure manner. When the injection time reaches a preset resonance excitation time, the micro ultrasonic vibrator is turned on, and the excitation frequency of the micro ultrasonic vibrator is adjusted to the resonance frequency of the target rock sample, converting the constant pressure mode to a constant flow mode. Fracturing fluid is injected into the simulated orifice on the perforation end face of the target rock sample in a constant flow mode until the target rock sample fractures, and pumping pressure time series data is obtained. The target pumping pressure time series data is determined as the fracturing pressure of the target rock sample, and the pressure value of the target pumping pressure time series data is greater than a preset pressure threshold.

[0156] In some embodiments, the aforementioned crack initiation pressure and crack initiation orientation determination module 403 can also be used to perform a CT scan on the fractured target rock sample after the target rock sample fractures, to obtain a three-dimensional image of the target rock sample; and to perform three-dimensional reconstruction on the three-dimensional image to obtain the crack initiation orientation of the target rock sample based on the result of the three-dimensional reconstruction.

[0157] As can be seen from the above, the rock hydraulic fracturing device under resonance excitation provided in the embodiments of this specification can achieve precise measurement of rock sample resonance frequency, fracturing initiation pressure under resonance excitation time, and fracturing initiation orientation, providing an experimental basis for studying the fracture induction mechanism under resonance excitation, thereby improving the hydraulic fracturing effect of unconventional oil and gas reservoirs and achieving increased production and efficiency of unconventional oil and gas.

[0158] This specification also provides an electronic device based on the above-described resonant excitation method for hydraulic fracturing of rocks, including a processor and a memory for storing processor-executable programs / instructions. Specifically, the processor can execute the following steps according to the program / instructions: acquiring excitation frequency timing data after applying an excitation frequency to the perforation end face of the target rock sample, and strain timing data for the other end faces besides the perforation end face, based on the simulated perforation diameter of the target rock sample; determining the resonant frequency of the target rock sample under the influence of the simulated perforation diameter from the excitation frequency timing data based on the strain timing data; determining the fracturing initiation pressure and fracturing initiation orientation of the target rock sample at the resonant frequency and a preset resonant excitation time; and formulating a fracture induction scheme under resonant excitation based on the fracturing initiation pressure and fracturing initiation orientation, and performing hydraulic fracturing based on the fracture induction scheme.

[0159] To execute the above instructions more accurately, please refer to... Figure 5 As shown in the embodiments of this specification, another specific electronic device is also provided, wherein the electronic device includes a network communication port 501, a processor 502 and a memory 503, and the above structures are connected by internal cables so that the various structures can perform specific data interaction.

[0160] Specifically, the network communication port 501 can be used to acquire excitation frequency timing data after applying excitation frequency to the perforation end face of the target rock sample, and strain timing data of the other end faces except the perforation end face, based on the simulated hole diameter of the target rock sample.

[0161] The processor 502 can be specifically used to determine the resonance frequency of the target rock sample under the influence of the simulated orifice diameter from the excitation frequency time series data based on the strain time series data; determine the initiation pressure and initiation orientation of the target rock sample under the resonance frequency and preset resonance excitation time; formulate a fracture induction scheme under resonance excitation based on the initiation pressure and initiation orientation, and perform hydraulic fracturing based on the fracture induction scheme.

[0162] The memory 503 can be used to store the corresponding instruction program.

[0163] In this embodiment, the network communication port 501 can be a virtual port bound to different communication protocols, thereby enabling the sending or receiving of different data. For example, the network communication port can be a port responsible for web data communication, a port responsible for FTP data communication, or a port responsible for email data communication. Furthermore, the network communication port can also be a physical communication interface or communication chip. For example, it can be a wireless mobile network communication chip, such as GSM or CDMA; it can also be a Wi-Fi chip; or it can be a Bluetooth chip.

[0164] In this embodiment, the processor 502 can be implemented in any suitable manner. For example, the processor can take the form of a microprocessor or processor and a computer-readable medium storing computer-readable program code (e.g., software or firmware) executable by the (micro)processor, logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers, etc. This specification is not limiting.

[0165] In this embodiment, the memory 503 may include multiple layers. In a digital system, anything that can store binary data can be a memory. In an integrated circuit, a circuit with storage function but no physical form is also called a memory, such as RAM, FIFO, etc. In a system, a storage device with a physical form is also called a memory, such as a memory stick, TF card, etc.

[0166] This specification also provides a computer storage medium for a rock hydraulic fracturing method based on the above-described resonance excitation. The computer storage medium stores a computer program / instruction that, when executed, performs the following: based on the simulated borehole diameter of the target rock sample, acquires excitation frequency timing data after applying an excitation frequency to the perforation end face of the target rock sample, and strain timing data for the other end faces besides the perforation end face; based on the strain timing data, determines the resonance frequency of the target rock sample under the influence of the simulated borehole diameter from the excitation frequency timing data; determines the fracture initiation pressure and fracture initiation orientation of the target rock sample at the resonance frequency and a preset resonance excitation time; and formulates a fracture induction scheme under resonance excitation based on the fracture initiation pressure and fracture initiation orientation, and performs hydraulic fracturing based on the fracture induction scheme.

[0167] In this embodiment, the storage medium includes, but is not limited to, Random Access Memory (RAM), Read-Only Memory (ROM), cache, hard disk drive (HDD), or memory card. The memory can be used to store computer program instructions. The network communication unit can be an interface configured according to standards specified in the communication protocol for network connection communication.

[0168] In this embodiment, the specific functions and effects implemented by the program instructions stored in the computer storage medium can be explained in comparison with other implementation methods, and will not be repeated here.

[0169] This specification also provides a computer program product based on the above-described resonant excitation-based hydraulic fracturing method for rocks, including a non-transient computer-readable storage medium storing computer programs / instructions. The computer programs / instructions are operable to cause a computer to perform the following steps: acquiring, based on the simulated borehole diameter of the target rock sample, excitation frequency time-series data after applying an excitation frequency to the perforation end face of the target rock sample, and strain time-series data for the other end faces besides the perforation end face; determining, based on the strain time-series data, the resonant frequency of the target rock sample under the influence of the simulated borehole diameter from the excitation frequency time-series data; determining, based on the resonant frequency, the fracturing initiation pressure and fracturing initiation orientation of the target rock sample at a preset resonant excitation time; and formulating a fracture induction scheme under resonant excitation based on the fracturing initiation pressure and fracturing initiation orientation, to perform hydraulic fracturing based on the fracture induction scheme.

[0170] While this specification provides the steps of operation for the methods described in the embodiments or flowcharts, more or fewer steps may be included based on conventional or non-inventive means. The order of steps listed in the embodiments is merely one possible order of execution among many steps and does not represent the only possible order. In actual device or client product execution, the methods shown in the embodiments or drawings may be executed sequentially or in parallel (e.g., in a parallel processor or multi-threaded processing environment, or even a distributed data processing environment). The terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, product, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, product, or apparatus. Without further limitations, the presence of other identical or equivalent elements in a process, method, product, or apparatus that includes said elements is not excluded. The terms "first," "second," etc., are used to denote names and do not indicate any particular order.

[0171] Those skilled in the art will also know that, besides implementing the controller using purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the controller function as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers (PLCs), and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the devices within it used to implement various functions can also be considered structures within that hardware component. Alternatively, the devices used to implement various functions can be considered as both software modules implementing the method and structures within a hardware component.

[0172] This specification can be described in the general context of computer-executable instructions that are executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, classes, etc., that perform a specific task or implement a specific abstract data type. This specification can also be practiced in distributed computing environments, where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0173] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this specification can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions of this specification can essentially be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, mobile terminal, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments of this specification.

[0174] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. This specification can be used in numerous general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable electronic devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.

[0175] Although this specification has been described by way of examples, those skilled in the art will recognize that many variations of this specification are possible without departing from its spirit, and it is intended that the appended claims cover such variations without departing from the spirit of this specification.

Claims

1. A method of hydraulic fracturing of rock under resonance excitation, characterized in that, The method comprises the following steps: According to the simulated hole diameter of the target rock sample, the excitation frequency time series data after the excitation frequency is applied to the perforated end face of the target rock sample and the strain time series data of the remaining end faces except the perforated end face are obtained; the remaining end faces except the perforated end face include five non-perforated end faces; According to the strain time series data, the resonance frequency of the target rock sample under the influence of the simulated hole diameter is determined from the excitation frequency time series data; The crack initiation pressure and the crack initiation orientation of the target rock sample under the preset resonance excitation time are determined according to the resonance frequency; According to the crack initiation pressure and the crack initiation orientation, a crack induction scheme under resonance excitation is formulated, and hydraulic fracturing is carried out based on the crack induction scheme; According to the strain time series data, the resonance frequency of the target rock sample under the influence of the simulated hole diameter is determined from the excitation frequency time series data, which comprises the following steps: Determine the average value of the strain time series data of the five non-perforated end faces; Select the average value of the target strain time series data from the average value of the strain time series data, which is greater than the preset average value threshold; Determine the time corresponding to the average value of the target strain time series data as the resonance excitation time; Determine the excitation frequency corresponding to the resonance excitation time from the excitation frequency time series data as the resonance frequency of the target rock sample; The resonance frequency of the target rock sample comprises: When the simulated hole diameter of the target rock sample is the preset hole diameter, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at the preset target water saturation; When the simulated hole diameter of the target rock sample is the inherent hole diameter, the target water saturation of the target rock sample corresponding to the resonance excitation time is determined, and accordingly, the resonance frequency of the target rock sample is the resonance frequency of the target rock sample at the target water saturation.

2. The method of claim 1, wherein, The target rock sample is a cuboid rock sample dried to a constant weight, and a simulated hole is drilled in one perforated end face of the cuboid rock sample; Accordingly, the method further comprises: Arranging a micro ultrasonic vibration rod on one perforated end face of the target rock sample and arranging corresponding micro resistance strain sensors on the five non-perforated end faces of the target rock sample; After the target rock sample is heated to the rock sample temperature, the fracturing fluid is injected into the simulated hole at a constant pressure; Accordingly, the method of obtaining the excitation frequency time series data after the excitation frequency is applied to the perforated end face of the target rock sample and the strain time series data of the remaining end faces except the perforated end face according to the simulated hole diameter of the target rock sample comprises: When the simulated hole diameter of the target rock sample is the preset hole diameter, it is judged whether the stop injection condition of the fracturing fluid is reached; If yes, the micro ultrasonic vibration rod is started and the excitation frequency of the micro ultrasonic vibration rod is gradually increased to obtain the excitation frequency time series data, and the strain time series data of the five non-perforated end faces are obtained by using the micro resistance strain sensors.

3. The method of claim 2, wherein, The judgment of whether the stop injection condition of the fracturing fluid is reached comprises: Obtaining the transverse relaxation time time series data of the target rock sample, which is used to determine the water saturation of the target rock sample; Judging whether the water saturation of the target rock sample reaches the preset target water saturation; If yes, stop injecting fracturing fluid in a constant pressure mode.

4. The method of claim 1, wherein, The determination of the cracking pressure of the target rock sample under the resonance frequency and the preset resonance excitation time comprises: injecting fracturing fluid into the simulated hole of the perforated end face of the target rock sample in a constant pressure mode, when the injection time reaches the preset resonance excitation time, turning on the micro ultrasonic vibration rod, adjusting the excitation frequency of the micro ultrasonic vibration rod to the resonance frequency of the target rock sample, and converting the constant pressure mode to a constant current mode; injecting fracturing fluid into the simulated hole of the perforated end face of the target rock sample in a constant current mode until the target rock sample breaks, and acquiring pump injection pressure time series data; determining target pump injection pressure time series data in the pump injection pressure time series data as the cracking pressure of the target rock sample, the pressure value of the target pump injection pressure time series data being greater than a preset pressure threshold.

5. The method of claim 1, wherein, The determination of the cracking orientation of the target rock sample under the resonance frequency and the preset resonance excitation time comprises: after the target rock sample breaks, performing CT scanning on the broken target rock sample to obtain a three-dimensional image of the target rock sample; performing three-dimensional reconstruction on the three-dimensional image to obtain the cracking orientation of the target rock sample according to the result of the three-dimensional reconstruction.

6. A device for hydraulic fracturing of rock under resonance excitation, characterized in that, It comprises: an acquisition module configured to acquire excitation frequency time series data after an excitation frequency is applied to a perforated end face of a target rock sample and strain time series data of remaining end faces except the perforated end face according to a simulated hole diameter of the target rock sample; the remaining end faces except the perforated end face include five non-perforated end faces; a resonance frequency determination module configured to determine a resonance frequency of the target rock sample under the influence of the simulated hole diameter from the excitation frequency time series data according to the strain time series data; a cracking pressure and cracking orientation determination module configured to determine a cracking pressure and a cracking orientation of the target rock sample under the resonance frequency and a preset resonance excitation time; a hydraulic fracturing module configured to formulate a crack induction scheme under resonance excitation according to the cracking pressure and the cracking orientation, and perform hydraulic fracturing based on the crack induction scheme; wherein the determination of the resonance frequency of the target rock sample under the influence of the simulated hole diameter from the excitation frequency time series data according to the strain time series data comprises: determining an average value of the strain time series data of the five non-perforated end faces; selecting an average value of target strain time series data from the average value of the strain time series data, the average value of the target strain time series data being greater than a preset average value threshold; determining a time corresponding to the average value of the target strain time series data as a resonance excitation time; determining an excitation frequency corresponding to the resonance excitation time from the excitation frequency time series data as the resonance frequency of the target rock sample; the resonance frequency of the target rock sample comprises: when the simulated hole diameter of the target rock sample is a preset hole diameter, the resonance frequency of the target rock sample is a resonance frequency of the target rock sample under a preset target water saturation; when the simulated hole diameter of the target rock sample is an inherent hole diameter, determining a target water saturation of the target rock sample corresponding to the resonance excitation time, and accordingly, the resonance frequency of the target rock sample is a resonance frequency of the target rock sample under the target water saturation.

7. A computer device comprising a memory, a processor, and a computer program / instructions stored on the memory, wherein, The processor executes the computer program / instructions to implement the steps of the method of any one of claims 1 to 5.

8. A computer readable storage medium having stored thereon computer programs / instructions, characterized in that, The computer program / instructions, when executed by the processor, implement the steps of the method of any one of claims 1 to 5.

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