Monitoring method and device for detonation fracturing based on tracer monitoring and distributed optical fiber sensing monitoring

Abstract

The present application belongs to the field of oil and gas development and energy utilization, and particularly relates to a detonation fracturing monitoring method and device based on tracer monitoring and distributed optical fiber sensing monitoring, aiming at solving the problem of insufficient monitoring of rapid dynamic changes of detonation fracturing in the prior art, which restricts the play of environmental protection and resource saving advantages. The present application comprises: calculating the hydraulic fracture volume according to the volume of the returned tracer; calculating the volume of the liquid explosive required by the hydraulic fracture volume; pumping the liquid explosive with adjusted viscosity into the hydraulic fracture in the horizontal well; based on the distributed optical fiber monitoring equipment, obtaining monitoring data after detonating the liquid explosive, evaluating the reservoir reconstruction effect of detonation fracturing by inversion calculation on the monitoring data, and detecting the stress-strain state of the reservoir after detonation fracturing. The present application realizes real-time and accurate monitoring of temperature, pressure and strain changes during detonation fracturing, and realizes resource saving.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of oil and gas development and energy utilization, and particularly relates to a detonation fracturing monitoring method and device based on tracer monitoring and distributed optical fiber sensing monitoring. BACKGROUND

[0002] In the field of shale oil and gas development, hydraulic fracturing technology is a technology that is widely used at present. Since the 1950s, this technology has played a key role in the development of shale gas, tight gas and other difficult-to-exploit resources. The core principle of hydraulic fracturing technology is to create and expand fractures by injecting high-pressure liquid into underground rock formations, thereby increasing the permeability of the rock and allowing oil and gas to flow more easily to the wellbore and be extracted. The liquid is usually composed of water, sand and various chemical additives, which are injected into the underground rock formation under high pressure to form fractures and keep these fractures open, thereby improving the flowability of oil and gas. The advantage of this technology is that it increases the production of the well during the production process, is suitable for reservoirs with large burial depth, and the technology has been relatively mature after decades of development. However, hydraulic fracturing technology has several significant disadvantages: first, its reformation effect on the reservoir is limited, which is particularly evident in the reformation of low-permeability and ultra-low-permeability reservoirs; second, and this is the core constraint faced by China's main shale oil production areas such as Xinjiang and Ordos—the technology requires a large amount of water resources. These areas are already severely water-deficient regions, and large-scale hydraulic fracturing operations (single well water consumption can reach tens of thousands of tons) not only exacerbate the local water shortage, but also bring about environmental impact problems such as fracturing fluid flowback, wastewater treatment and potential groundwater pollution, greatly limiting the sustainable application and economy of the technology.

[0003] In recent years, a new technology—detonation fracturing technology with significant resource conservation and environmental protection advantages—has developed. The principle of this technology is to use the shock wave and stress wave generated by the explosion of explosives inside the reservoir fractures to destroy the rock around the wellbore, forming a fracture network composed of many densely distributed fine fractures, which can greatly improve the permeability of the reservoir and thus improve the production during the shale oil and gas exploitation process. Its most core advantage is to completely overturn the dependence of traditional fracturing on water resources, especially zero water consumption, and the detonation fracturing technology does not need to use water as a fracturing fluid medium, which fundamentally eliminates the need for a large amount of fresh water resources by hydraulic fracturing. This has revolutionary significance for the development of shale oil in severely water-deficient areas such as Xinjiang and Ordos in China, directly solving the water resource bottleneck and greatly reducing the environmental pressure and cost of development. At the same time, this technology also avoids the use of proppants and a large amount of chemical additives, further embodying its conservation in material consumption.

[0004] Because the detonation fracturing is a dynamic fracturing process in which energy is released in a very short time, in the process of reservoir reconstruction by the detonation fracturing, the formation time of part of the fracture network is shorter, and the microseismic monitoring technology which is widely used in the hydraulic fracturing to evaluate the reservoir reconstruction effect and the fracture propagation effect is no longer applicable in this case. The principle of the microseismic monitoring technology is that the damage of human engineering activities (geological exploration, oil and gas resource exploitation) to the surrounding rock structure can cause local stress concentration in the surrounding rock. Due to the insufficient strength of the surrounding rock, the local large amount of energy aggregation can cause micro damage or plastic deformation of the surrounding rock. The micro damage gradually accumulates to form a macro crack. In the formation and expansion process of the crack, energy is released in the form of elastic waves. The rock acoustic emission with a low frequency band (generally below 1 kHz) formed in this process is called microseismic, also known as a small earthquake event. The microseismic monitoring technology is to monitor the microseismic caused by the reservoir fracturing reconstruction in the oil well production to evaluate the formation and expansion of the fracture system, and then evaluate the reservoir reconstruction effect.

[0005] Because the detonation fracturing is a process in which a very high energy is released in a very short time, the traditional microseismic monitoring technology used in the hydraulic fracturing cannot capture the change of the rapidly formed fracture network, and the microseismic monitoring needs to arrange a large number of sensors on the ground. Even so, it is difficult to capture the high-frequency detonation fracturing cracking event, so it is difficult to accurately evaluate the reservoir reconstruction effect.

[0006] The existing monitoring technology is mainly designed based on static or slow changes. For the instantaneous dynamic event of the detonation fracturing, the existing monitoring means is insufficient, which seriously affects the great potential of the detonation fracturing in time, materials (water, proppant, chemical agent) and cost saving. It is urgent to develop a new type of real-time monitoring method which is matched, efficient and dynamic, so as to fully play the advantages of the detonation fracturing in high efficiency, saving and environmental protection, and avoid the waste of resources and the loss of efficiency caused by the failure of monitoring.

[0007] Based on this, the present application provides a detonation fracturing monitoring method and device based on tracer monitoring and distributed optical fiber sensing monitoring. SUMMARY

[0008] In order to solve the above problems in the prior art, that is, the defects of the existing monitoring technology that the response is lagging and cannot adapt to the instantaneous dynamic process, which leads to the problem that the detonation fracturing effect cannot be effectively evaluated, and seriously restricts the play of the key environmental protection and resource saving advantages of the technology in water saving, material saving and efficiency improvement, the present application provides a detonation fracturing monitoring method and device based on tracer monitoring and distributed optical fiber sensing monitoring.

[0009] In the first aspect of the present application, a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring is provided, which comprises the following steps:

[0010] Step S1, after drilling, tracer is injected into the horizontal well, and the volume of the hydraulic fracture is calculated according to the volume of the returned tracer;

[0011] Step S2, the volume of the liquid explosive required for calculating the volume of the hydraulic fracture is calculated, and the viscosity of the liquid explosive is adjusted;

[0012] Step S3, the liquid explosive with adjusted viscosity is pumped into the hydraulic fracture in the horizontal well;

[0013] Step S4, based on the distributed optical fiber monitoring device, monitoring data after the liquid explosive is detonated is obtained, the reservoir reconstruction effect of the detonation fracturing is evaluated by inverting the monitoring data, and the stress-strain state of the reservoir after the detonation fracturing is detected;

[0014] The distributed optical fiber monitoring device is installed on the detonation fracturing monitoring device based on the tracer monitoring and the distributed optical fiber sensing monitoring.

[0015] Further, the volume of the liquid explosive is calculated by the following method:

[0016] Step S21, the height of the main fracture is calculated according to the volume of the fracturing fluid injected by the hydraulic fracturing;

[0017] Step S22, the maximum fracture width of the main fracture is calculated according to the fluid pressure in the construction stage, the elastic modulus of the formation, the Poisson's ratio and the height of the main fracture;

[0018] Step S23, the length at the critical detonation diameter of the liquid explosive is calculated according to the maximum fracture width, the critical detonation diameter of the liquid explosive and the half fracture length designed by the hydraulic fracturing;

[0019] Step S24, the volume of the liquid explosive is calculated based on the length at the critical detonation diameter of the liquid explosive, the maximum fracture width and the critical detonation diameter of the liquid explosive.

[0020] Further, the maximum fracture width is calculated by the following method:

[0021] ;

[0022] wherein, v is the Poisson's ratio, E is the elastic modulus of the formation, H is the height of the main fracture, P 0 is the fluid pressure in the construction stage.

[0023] Further, the length at the critical detonation diameter of the liquid explosive L d is calculated by the following method:

[0024] ;

[0025] wherein, is the critical initiation diameter of the liquid explosive, L is the half fracture length of the hydraulic fracture design.

[0026] Further, the volume of the liquid explosive is The calculation method is as follows:

[0027] .

[0028] Further, the distributed optical fiber monitoring device comprises one or more of a distributed temperature optical fiber sensor, a distributed acoustic optical fiber sensor, and a distributed strain optical fiber sensor.

[0029] Further, the distributed optical fiber monitoring device is installed on the outer circumferential surface of the casing near one side of each perforation.

[0030] Further, the distributed optical fiber monitoring device is installed in the optical fiber hub column, and the optical fiber hub column is installed on the outer circumferential surface of the casing near the edge of each perforation.

[0031] Further, the axial direction of the optical fiber hub column is perpendicular to the axial direction of the casing.

[0032] Another aspect of the present application provides a detonation fracturing monitoring device based on tracer monitoring and distributed optical fiber sensing monitoring, and a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring, the device comprising a bridge plug, an initiator, a safety gun, a centralizer, a packer, an optical fiber hub column, a perforation, and a casing.

[0033] The casing is placed horizontally in the horizontal well, and a plurality of perforations are uniformly arranged on both sides of the surface of the casing along the length direction, wherein the perforations on one side are staggered with the perforations on the other side, and an optical fiber hub column is arranged at the edge of each perforation, and the optical fiber hub column is fixed on the outer surface of the casing.

[0034] A plurality of centralizers are coaxially installed on the outer surface of the casing, and the centralizers are used to centralize the casing.

[0035] The casing is sequentially provided with a packer, an initiator, and a safety gun from the end near the vertical well to the other end, the initiator is used to detonate the liquid explosive, and the safety gun is used to transmit the detonation signal to the initiator.

[0036] A bridge plug is arranged on the well wall of the side of the horizontal well close to the vertical well, and the bridge plug is used to prevent the backflow of liquid explosives and fluid in the hydraulic fracturing process.

[0037] Advantages of the present application:

[0038] By combining tracer monitoring and distributed optical fiber sensing technology, the present application can obtain key dynamic data (temperature, pressure, strain) in the process of detonation fracturing in real time, and realize accurate evaluation of the reservoir reconstruction effect. This not only provides a scientific basis for optimizing production, but more importantly, accurate evaluation avoids repeated fracturing or ineffective intervention due to unknown effects, thereby fundamentally eliminating unnecessary explosives, labor and energy consumption, and embodying the core value of resource conservation.

[0039] The fracture volume is accurately calculated using the flowback tracer, and the amount and viscosity of the liquid explosive are optimized accordingly to ensure efficient use of explosives. This precise regulation minimizes explosive waste, significantly reduces construction costs and potential environmental risks (such as unexploded explosive residues), and is a direct embodiment of resource conservation and environmental friendliness.

[0040] The overall operation time of the method (detonation fracturing + supporting monitoring) is extremely short, from injection to detonation, to effect evaluation, which is a complete process. Compared with the long construction and flowback waiting period of traditional hydraulic fracturing, the production cycle is greatly shortened. This not only significantly improves the operation efficiency, but also directly saves a large amount of time cost, equipment occupation cost and labor cost, and is a model of efficiency conservation.

[0041] The self-supporting fracture network formed by detonation fracturing completely eliminates the large amount of proppant (such as sand) required by traditional hydraulic fracturing and the large amount of fracturing fluid (water) required to carry the proppant. This directly realizes zero consumption of water resources, avoids the environmental footprint of proppant mining, transportation and injection, and the chemical pollution risk caused by the preparation and use of fracturing fluid, and is a revolutionary breakthrough in environmental protection and material conservation.

[0042] The use of distributed optical fiber sensing technology instead of traditional microseismic monitoring perfectly solves the failure problem of the latter in the face of high-speed detonation process. Optical fiber sensing does not require a large number of sensors to be deployed on the ground, the equipment investment is more simplified, and the data acquisition is more efficient and real-time. This efficient and low-cost monitoring method itself is a resource conservation, and its accurate evaluation capability ensures that the overall operation of the saving benefit is realized.

[0043] The design of integrating distributed optical fiber monitoring equipment on a special perforating gun not only ensures the stability and reliability of monitoring and construction safety, but also avoids the manpower, material resources and time investment required by traditional monitoring methods (such as a large number of buried detectors), further embodying efficiency and conservation from the equipment deployment level. BRIEF DESCRIPTION OF DRAWINGS

[0044] Other features, objects, and advantages of the application will become more apparent from the following detailed description when read in connection with the following drawings:

[0045] Figure 1 is a flowchart of a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring provided by a first embodiment of the application;

[0046] Figure 2 is a structural schematic diagram of a detonation fracturing monitoring device based on tracer monitoring and distributed optical fiber sensing monitoring provided by a second embodiment of the application. DETAILED DESCRIPTION

[0047] The application will be further described below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related application, and not to limit the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for ease of description.

[0048] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0049] The application provides a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring, which comprises the following steps:

[0050] Step S1, after drilling is completed, a tracer is put into a horizontal well, and the volume of a hydraulic fracture is calculated according to the volume of the returned tracer;

[0051] Step S2, the volume of liquid explosive required by the hydraulic fracture is calculated, and the viscosity of the liquid explosive is adjusted;

[0052] Step S3, the liquid explosive with adjusted viscosity is pumped into the hydraulic fracture in the horizontal well;

[0053] Step S4, based on a distributed optical fiber monitoring device, monitoring data after the liquid explosive is detonated are obtained, the reservoir reconstruction effect of the detonation fracturing is evaluated by inverse calculation on the monitoring data, and the stress-strain state of the reservoir after the detonation fracturing is detected;

[0054] The distributed optical fiber monitoring device is installed on a detonation fracturing monitoring device based on tracer monitoring and distributed optical fiber sensing monitoring.

[0055] In order to more clearly describe the detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring, the following will be combined with Figure 1The steps in the embodiments of the present application are described in detail.

[0056] The first embodiment of the present application is a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring, which comprises steps S1-S4, and each step is described in detail as follows:

[0057] Step S1, after drilling is completed, a tracer is injected into the horizontal well, and the hydraulic fracture volume is calculated according to the volume of the returned tracer;

[0058] In the present application, the length of the horizontal well is generally 2000-2500 m, the length of a single fracturing section is 40-50 m, the number of single sections is 6-8 clusters, and the cluster spacing is 5-8 m; the perforation uses equal-aperture perforating bullets (effective aperture ≥10 mm) and 89 type perforating guns, 0.5-2 m per cluster, and 3-16 holes per cluster. The width of the main hydraulic fracture is generally 2 mm.

[0059] In this embodiment, according to the reservoir characteristics (such as permeability, temperature, pressure, etc.) and the target monitoring requirements, a suitable tracer is selected. After the drilling operation is completed, the selected tracer is injected into the horizontal well section through a special pump. The injection position should cover the area where the detonation fracturing is planned to be carried out. The injection pressure and flow rate need to be monitored during the injection process to ensure that the tracer can be uniformly distributed in the entire target interval. After the injection is completed, the injection pump is closed, and the liquid in the formation is allowed to return naturally. This process may take some time, depending on the pressure and permeability of the formation. During the return, the flow rate and composition of the return fluid are continuously monitored, especially the appearance time and concentration change of the tracer.

[0060] The tracer information in the return fluid is collected using surface or downhole sensors. These sensors can detect the presence of the tracer and its concentration. The collected data is transmitted to the ground control system for processing. Based on the concentration curve of the tracer in the return fluid, combined with known formation parameters (such as porosity, permeability, filtration coefficient, etc.), the volume of the fracture network formed after hydraulic fracturing is estimated based on the law of conservation of mass.

[0061] The tracer is insoluble in water and has a certain volume (such as 100 microns) to prevent the tracer from entering the internal pores of the rock.

[0062] The method for calculating the fracture network volume according to the return tracer information is as follows:

[0063] The return flow rate of the monitoring tracer changes with the return time Q ( t ) and the concentration C ( t ) of the return tracer, the average concentration of the return fluid is calculated according to the following formula:

[0064] ;

[0065] wherein t t is time, T T is the total time of fracturing fluid flowback.

[0066] The total volume of the fracture network is then V f which can be estimated according to the following formula:

[0067] ;

[0068] wherein C initial C is the average concentration of tracer when injecting the tracer-containing fracturing fluid; V inj V is the total volume of the injected fracturing fluid; η s R is the retention coefficient of the tracer (0 η s ≤ 1).

[0069] Step S2, calculating the volume of liquid explosive required for the volume of the hydraulic fracturing fracture, and adjusting the viscosity of the liquid explosive;

[0070] wherein, the viscosity of the liquid explosive is adjusted to be close to the viscosity of the commonly used proppant slickwater of 1-270 mPa·s, preparing to pump the explosive, through the accurate calculation and adjustment of the viscosity, the liquid explosive can be more uniformly distributed in the fracture, thereby significantly enhancing the expansion effect of the fracture and improving the production of the oil and gas well.

[0071] The volume of the liquid explosive is calculated according to the following formula:

[0072] Step S21, calculating the height of the main fracture according to the volume of the fracturing fluid injected by hydraulic fracturing;

[0073] Step S22, calculating the maximum fracture width of the main fracture according to the fluid pressure during construction, the elastic modulus of the formation, the Poisson's ratio, and the height of the main fracture :

[0074] ;

[0075] wherein, v is the Poisson's ratio, E is the elastic modulus of the formation, H is the height of the main fracture, P 0 is the fluid pressure during construction;

[0076] Step S23, calculating the length at the critical detonation diameter of the liquid explosive according to the maximum fracture width, the critical detonation diameter of the liquid explosive, and the half-fracture length of the hydraulic fracturing design Ld :

[0077] ;

[0078] wherein, is the critical initiation diameter of the liquid explosive, L is the half fracture length of the hydraulic fracture design;

[0079] Step S24, based on the length at the critical initiation diameter of the liquid explosive, the maximum fracture width and the critical initiation diameter of the liquid explosive, the volume of the liquid explosive is calculated :

[0080] .

[0081] Step S3, pumping the liquid explosive with adjusted viscosity into the hydraulic fracturing fracture in the horizontal well;

[0082] This embodiment uses a fracturing pump (minimum displacement 0.5m 3 / min) to send into the horizontal well, and under the powerful pumping pressure, the liquid explosive enters the hydraulic fracturing fracture.

[0083] Step S4, based on the distributed optical fiber monitoring equipment, obtaining monitoring data after detonating the liquid explosive, evaluating the reservoir reconstruction effect of the detonation fracturing by inverse calculation on the monitoring data, and detecting the stress-strain state of the reservoir after the detonation fracturing;

[0084] Among them, the distributed optical fiber monitoring equipment is installed on the detonation fracturing monitoring device based on tracer monitoring and distributed optical fiber sensing monitoring, and according to the monitoring requirements, appropriate types of distributed optical fiber sensors are selected and installed. These sensors can include but are not limited to:

[0085] Distributed temperature optical fiber sensor (DTS): detecting the reservoir temperature rise caused by a large amount of heat during the detonation fracturing process, and monitoring the temperature change data in the wellbore.

[0086] Distributed acoustic optical fiber sensor (DAS): monitoring the crack dynamic expansion acoustic signal during the detonation fracturing process to obtain vibration data, and capturing stress waves and microseismic activities generated by detonation.

[0087] Distributed strain optical fiber sensor (DFS): monitoring the reservoir deformation after detonation fracturing to obtain strain data, and measuring the strain change of the rock formation to evaluate the crack expansion.

[0088] Based on the comprehensive processing and analysis of the above three signals (vibration, temperature and strain), the signal intensity along the optical fiber distribution is obtained, and then the position, direction and density of the crack expansion are determined.

[0089] The distributed optical fiber monitoring device is installed on the outer circumferential surface of the casing near one side of each perforation. The distributed optical fiber monitoring device is installed in the optical fiber hub, which is installed on the outer circumferential surface of the casing near the edge of each perforation. The axial direction of the optical fiber hub is perpendicular to the axial direction of the casing, ensuring that the sensor can accurately monitor the dynamic changes near each perforation.

[0090] Among them, the present application puts forward the concept of tracer monitoring and distributed optical fiber reconstruction, and evaluates the hydraulic fracture volume and detonation fracture stress-strain of the reservoir section needing reconstruction.

[0091] According to the monitoring data of the distributed optical fiber sensor, combined with the application of gradient method, random method and other various inversion methods, the production profile and crack characteristics are inverted and calculated, and the reservoir reconstruction effect of detonation fracturing is evaluated, which provides data support for the reconstruction of other reservoir sections in the same horizontal well next time.

[0092] In the embodiment, the step S4 includes the following steps:

[0093] Step S41, synchronously collecting multi-modal sensing data in the detonation process by the distributed optical fiber sensing system, including strain field fluctuation, acoustic vibration spectrum and temperature field migration parameters, and constructing a time-space aligned fusion data set:

[0094] At the moment of detonation, the multi-modal synchronous acquisition module of the distributed optical fiber sensing system is started to synchronously capture the following fusion data with millisecond time resolution:

[0095] The dynamic strain propagation characteristics of the detonation shock wave at the wellbore-crack-rock interface are analyzed by the distributed strain optical fiber sensor, and the coupling effect of longitudinal wave, transverse wave and surface wave is distinguished;

[0096] The rock fracture acoustic emission events caused by detonation energy release in the crack network are recorded by the distributed acoustic wave optical fiber sensor, and the mapping relationship between acoustic fingerprint characteristics and crack propagation rate is established;

[0097] The local temperature gradient changes caused by detonation heat release and crack fluid seepage are monitored by the distributed temperature optical fiber sensor, and the fluid migration path of the new crack is located;

[0098] A time-space synchronous coordinate system is constructed, and the three-dimensional parameters of optical fiber axial distance, detonation time sequence and formation depth are dynamically bound to generate a time-space aligned fusion data set.

[0099] Step S42, based on the fusion data set, the signal demixing algorithm is used to separate the crack dynamic expansion event characteristics, and the detonation energy propagation path and crack network topology structure are inverted combined with the physical driving model:

[0100] Based on the fusion data set in step S41, a deep learning driven signal demixing algorithm is used to separate the low frequency vibration signal of the original crack re-opening, the high frequency microseismic event cluster of the new crack propagation and the nonlinear pressure oscillation of the secondary explosion of liquid explosive residues;

[0101] According to the strain wave front arrival time difference, the anisotropic propagation path of the detonation energy in the heterogeneous stratum is inverted, and the energy attenuation coefficient matrix is established to quantify the dissipation effect of crack roughness on shock wave energy;

[0102] The separated multi-source data is input into the crack propagation simulation model to simulate the crack fractal propagation process in real time, analyze the fluid-structure coupling behavior of the main crack intersection area and the stress shadow zone, and generate the crack network topology structure.

[0103] Step S43, fuse the crack network topology and energy propagation path, and through multi-parameter coupling analysis, invert the reservoir reconstruction volume, crack permeability and in-situ stress field distribution, and generate a three-dimensional reconstruction sweet spot index distribution map:

[0104] Fuse the acoustic emission event density, strain disturbance range and temperature anomaly area to construct the time-varying probability cloud map of the reconstruction volume, and correct the boundary judgment error through cross-scale data correlation;

[0105] Based on the harmonic resonance effect of acoustic wave signal and the fluid convection velocity inverted from temperature field, a machine learning model of crack opening and permeability tensor is established;

[0106] Through the strain reconstruction algorithm, the maximum horizontal principal stress direction deflection characteristics of the near wellbore zone are extracted, and a dynamic geomechanical model is constructed combining the crack network topology to predict the interference effect of the detonation-induced stress field on the crack propagation of adjacent wells, and generate a three-dimensional reconstruction sweet spot index distribution map quantifying the contribution weight of production capacity.

[0107] Step S44, according to the inversion result, establish the detonation parameter optimization strategy, and realize the model parameter self-correction through cross-physical field data verification:

[0108] Establish the association knowledge graph of detonation parameters and fiber response characteristics, and generate a dynamic fracturing strategy through reinforcement learning algorithm;

[0109] Cross-physical field coupling verification is performed on the real-time inversion results and tracer monitoring data to correct the energy attenuation coefficient matrix and geomechanical model parameters, forming a self-correcting and optimizing closed loop.

[0110] Wherein, a unified millisecond time stamp is added to the distributed strain fiber (DFS), acoustic fiber (DAS) and temperature fiber (DTS) data, and the time synchronization error is less than 0.1 ms;

[0111] According to the stratum depth-fiber distance mapping table (calibrated by cable magnetic markers), the DFS strain data, DAS acoustic wave data, and DTS temperature data are segmented and spatially interpolated per meter to align.

[0112] Wavelet threshold denoising is adopted for the DFS original strain data (sym8 wavelet basis is selected, and soft threshold processing is adopted);

[0113] Acoustic spectrum extraction: short-time Fourier transform (STFT) is performed on the DAS acoustic wave signal, the window length is 10 ms, the step length is 1 ms, and a time-frequency spectrum matrix is generated;

[0114] Temperature gradient calculation: the temperature gradient field is calculated from the DTS temperature data according to the spatial derivative method.

[0115] In this embodiment, the GAN network architecture includes: constructing an adversarial generation network composed of a generator (U-Net structure) and a discriminator (5-layer CNN), the input is a DAS time-frequency spectrum matrix, and the output is a separated low-frequency crack re-zhang crack signal (10-100 Hz) and a high-frequency new crack signal (1-10 kHz);

[0116] Training data: 200 groups of historical fracturing data (including artificially labeled crack type labels) are used for supervised training,

[0117] Hilbert-Huang transform (HHT) is performed on the DFS strain waveform to extract the instantaneous frequency of the nonlinear oscillation component, and when the frequency suddenly changes to 200-500 Hz, it is determined as a secondary explosion event.

[0118] In this embodiment, the time delay of the DFS strain wave front arriving at different fiber segments is calculated by the cross-correlation algorithm, and the wave velocity field is inverted.

[0119] In this embodiment, the attenuation coefficient matrix is constructed as follows:

[0120] Based on the DAS signal attenuation rate , the frequency-dependent attenuation coefficient is fitted α ( f )=0.02 f +0.1( f is the frequency, unit: kHz; d is the propagation distance, unit: m).

[0121] In this embodiment, the crack propagation simulation specifically includes:

[0122] LatticeBoltzmann model parameters: set the grid resolution to 0.1 m x 0.1 m, the fluid viscosity to 5 mPa·s, the rock Young's modulus to 20 GPa, and the Poisson's ratio to 0.25;

[0123] Adaptive mesh refinement: when local stress gradient exceeds 10 MPa / m, mesh is refined to 0.05 m x 0.05 m to capture shear slip effect at main fracture intersection.

[0124] In this embodiment, reservoir parameter inversion and sweet spot index calculation are performed, and the specific method is as follows:

[0125] Stimulated reservoir volume (SRV) quantification:

[0126] Probability fusion rule: define SRV probability as:

[0127] ; wherein, is the acoustic emission event density (number of events / m3), normalized to [0, 1]; is the strain disturbance amplitude (με), normalized to [0, 1]; is the temperature anomaly value (℃), normalized to [0, 1].

[0128] Boundary correction: align the fiber SRV probability cloud map with the previous microseismic monitoring point cloud data through transfer learning, and use Chamfer distance to optimize the boundary contour :

[0129]

[0130] wherein, is a set of three-dimensional point clouds generated by the distributed optical fiber monitoring data, representing the space-time position of strain, temperature or acoustic events in the reservoir. p is a point in the set of three-dimensional point clouds generated by the distributed optical fiber monitoring data.

[0131] is a set of three-dimensional point clouds of microseismic monitoring data, representing the position of fracture propagation events, q is a point in the set of three-dimensional point clouds of microseismic monitoring data.

[0132] Fracture permeability inversion:

[0133] Harmonic resonance frequency shift model: establish the relationship between fracture opening w ( mm ) and resonance frequency shift Δf ( Hz ):

[0134] ;

[0135] wherein, L is the fracture length (unit: m), representing the extension distance of the fracture in the horizontal direction; E is the elastic modulus of the rock, and h is the thickness of the rock layer.

[0136] Permeability tensor calculation: based on the fluid velocity field inverted by DTSv x z Inversion of permeability by Darcy's law.

[0137] In this embodiment, the strain-stress conversion is calculated by the generalized Hooke's law.

[0138] In this embodiment, the dessert index is calculated, and the method is as follows:

[0139] The dessert index is defined as:

[0140] wherein, is the stress shadow zone suppression coefficient (0-1).

[0141] In this embodiment, the detonation parameter optimization engine comprises:

[0142] Reinforcement learning framework: DDPG algorithm is adopted, and the following is defined:

[0143] State space: including SRV distribution, dessert index, and well interference intensity;

[0144] Action space: charge weight (50-200kg), detonation velocity (3000-6000m / s), and pumping timing (0-60s);

[0145] Reward function: ; wherein, is the quantitative stress interference degree of detonation fracturing on adjacent production wells (such as the capacity reduction caused by the extension of the fracture to the vicinity of the adjacent well).

[0146] Policy iteration: update the policy network weight after each fracturing until the reward function converges (change rate <1%).

[0147] The present application solves the problem that the traditional microseismic monitoring technology cannot capture high-frequency and rapid crack network formation due to low-frequency response and surface layout limitations by using the millisecond-level high-time resolution data acquisition capability of the distributed optical fiber sensing system (DTS, DAS, DFS) to capture the transient events such as shock wave propagation, crack dynamic expansion and fluid seepage in the detonation fracturing process in real time, and provides full-time and space scale monitoring support for the dynamic fracturing process.

[0148] The present application is based on the deep fusion of multi-modal optical fiber data (strain field, acoustic spectrum, temperature field), combined with physical driving model and machine learning algorithm, which accurately decouples the complex event characteristics such as primary crack re-opening, new crack expansion and energy dissipation, breaks through the limitation of traditional single parameter inversion, and significantly improves the accuracy of crack network morphology, permeability distribution and ground stress field reconstruction.

[0149] ​​The present application directly converts the optical fiber monitoring data into quantifiable engineering parameters (such as fracture conductivity, potential production area) by constructing the time-varying probability cloud map of the modified volume (SRV), the fracture permeability grading model and the three-dimensional distribution map of the "sweet spot index", provides visual decision basis for the optimization of detonation parameters, and avoids relying on empirical adjustment.

[0150] The present application dynamically corrects the energy attenuation coefficient, the permeability model and the ground stress field parameter based on the reinforcement learning algorithm and the cross-physical field verification (such as tracer-fiber data matching), so that the detonation fracturing scheme can adapt to the reservoir heterogeneity and the interference effect of adjacent wells, and significantly improves the modification efficiency and the long-term stable production capacity.

[0151] The present application reduces the dependence of traditional hydraulic fracturing on chemical additives and proppants through the self-supporting effect verification and real-time monitoring feedback of the proppant-free fracture network, reduces the environmental risk, and at the same time, the combination of the characteristics of rapid modification and immediate production and the precise evaluation means provides technical support for the efficient development of low-permeability and ultra-low-permeability reservoirs.

[0152] Although each step is described in the above-mentioned order in the above-mentioned embodiment, it can be understood by those skilled in the art that, in order to achieve the effect of the present embodiment, different steps do not have to be executed in such an order, they can be executed simultaneously (in parallel) or in a reversed order, and these simple changes are within the protection scope of the present application.

[0153] As shown in FIG. Figure 2 The present application provides a detonation fracturing monitoring device based on tracer monitoring and distributed optical fiber sensing monitoring, and a detonation fracturing monitoring method based on tracer monitoring and distributed optical fiber sensing monitoring.

[0154] The horizontal well is lowered into the horizontal casing 8, a plurality of perforation openings 7 are uniformly arranged on both sides of the surface of the casing 8 along the length direction, the perforation openings 7 on one side are staggered with the perforation openings 7 on the other side, an optical fiber concentrator 6 is arranged at the edge of each perforation opening 7, and the optical fiber concentrator 6 is fixed on the outer surface of the casing 8.

[0155] A plurality of centralizers 4 are coaxially installed on the outer surface of the casing 8, and the centralizers 4 are used to centralize the casing 8.

[0156] The casing 8 is sequentially provided with a packer 5, an initiator 2 and a safety gun 3 from the end close to the vertical well to the other end, the initiator 2 is used to detonate the liquid explosive, and the safety gun 3 is used to transmit the detonation signal to the initiator 2.

[0157] A bridge plug 1 is installed on the well wall near the side of the horizontal well close to the vertical well, which is used to prevent the backflow of liquid explosives and fluids during the hydraulic fracturing process.

[0158] Before hydraulic fracturing, the target interval is first isolated from other intervals by the bridge plug 1, preventing fracturing fluid from channeling into other intervals.

[0159] Then, the selected fracturing section is further closed using the packer 5, preparing for subsequent high-pressure injection.

[0160] Mix an appropriate amount of chemical tracers in the fracturing fluid, which will not affect the performance of the fracturing fluid, but can help track the crack propagation path and range in subsequent monitoring.

[0161] The selection of tracers should be based on their unique physical or chemical properties, such as fluorescence, radioactivity, etc., so that they can be clearly distinguished during subsequent detection.

[0162] The fracturing fluid containing tracers is injected into the target interval through the pumping system, opening natural fractures or forming new fractures in the formation under high pressure.

[0163] At the same time, real-time monitoring of temperature, pressure and strain changes is carried out using distributed optical fiber sensors, recording dynamic parameters during crack formation and development.

[0164] The data from the distributed optical fiber sensors is received by ground equipment and analyzed to assess the distribution of the crack network.

[0165] According to the migration trajectory of the tracers, the actual orientation and connectivity of the cracks are determined, thereby optimizing subsequent production strategies.

[0166] Before starting any operation, ensure that all workers have evacuated to a safe area and that all equipment is in good condition.

[0167] Confirm the functionality of the detonator 2, safety gun 3 and bridge plug 1, especially the bridge plug 1, which is used to prevent the backflow of liquid explosives and fluids generated during subsequent hydraulic fracturing.

[0168] Use the packer 5 to further close the selected fracturing section, preparing for subsequent high-pressure injection. This step is to ensure that the liquid explosives only act on the intended target interval, avoiding unnecessary impact on other formations.

[0169] Use the fracturing pump to transport the liquid explosives from the ground to the designated location underground. The delivery pipeline must have high-pressure resistance, corrosion resistance, etc. to ensure the safety and efficiency of transportation.

[0170] The delivery pressure of the liquid explosive should be adjusted according to the well depth and geological conditions to ensure that it reaches the desired depth smoothly without leakage or premature detonation.

[0171] Before pumping, set the key parameters such as pressure and flow rate of the pump to ensure that the liquid explosive can be evenly distributed throughout the target interval.

[0172] Adjust the speed of the pump so that the liquid explosive can completely fill the rock fissures around the perforation 7 within a suitable time to form an effective blasting environment.

[0173] Start the fracturing pump and pump the liquid explosive into the well through the channel in the casing 8. Then, pump the displacement fluid to completely displace the liquid explosive from the wellbore to the reservoir inside. Due to the viscosity of the liquid explosive, a stable pumping speed needs to be maintained to avoid blockage or other problems.

[0174] Monitor the pressure changes during pumping and take immediate action to address any abnormalities, such as slowing down the pump or stopping pumping for inspection.

[0175] Monitor various parameters in real time during pumping, including but not limited to pump pressure, flow rate, and changes in temperature and pressure in the well.

[0176] Use distributed optical fiber sensors (such as DTS, DAS, DFS) to monitor the dynamic changes in the well in real time, ensuring that the liquid explosive correctly fills the hydraulic fractures and achieves the best results, and ensuring that there is no liquid explosive or the concentration of liquid explosive in the wellbore is far below the explosion threshold.

[0177] After completing the pumping of the liquid explosive, use distributed optical fiber sensors to further confirm whether the liquid explosive has been evenly distributed in place, with particular attention to the filling conditions near the perforation 7.

[0178] If some areas are found to be underfilled, consider increasing the pumping volume or adjusting the pumping strategy.

[0179] When all preparations are complete, issue the detonation command and send a signal to the detonator 2 through the safety gun 3 to trigger the liquid explosive to explode.

[0180] The detonation instantaneously generates a powerful shock wave and high temperature, rapidly penetrating the rock formation and forming a large number of micro cracks, increasing the permeability of the reservoir.

[0181] At the moment of detonation, the fracturing pump uses distributed optical fiber sensors such as DTS, DAS, and DFS to record the temperature, acoustic waves, and strain changes in the well simultaneously, capturing the detonation event and the stress wave propagation path it triggers.

[0182] The ground platform rapidly processes and inverts the collected data to reconstruct the spatial distribution and temporal evolution of the fracture propagation during the detonation fracturing and to evaluate the effect of the detonation fracturing.

[0183] The temperature, acoustic and strain data are combined to comprehensively evaluate the effect of the detonation fracturing on the reservoir reconstruction, in particular whether the newly created fracture network significantly improves the reservoir connectivity and the oil and gas flowability.

[0184] The terms "first", "second", and the like, are used to distinguish similar objects, not to describe or indicate a particular order or sequence.

[0185] The term "comprising" or any other similar term is intended to encompass the inclusion of non-exclusive inclusion, so that the process, method, article or equipment / device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes the elements inherent to the process, method, article or equipment / device.

[0186] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A method of monitoring a detonation fracturing based on a tracer monitoring and a distributed optical fiber sensing monitoring, characterized in that, The method comprises the following steps: Step S1, after the drilling is completed, a tracer is injected into the horizontal well, and the volume of the hydraulic fracture is calculated according to the volume of the returned tracer; Step S2, the volume of the liquid explosive required by the hydraulic fracture is calculated, and the viscosity of the liquid explosive is adjusted; The volume of the liquid explosive is calculated by the following method: Step S21, the height of the main fracture is calculated according to the volume of the fracturing fluid injected in the hydraulic fracturing; Step S22, calculating the maximum crack width of the main crack according to the fluid pressure in the construction stage, the elastic modulus of the stratum, the Poisson's ratio and the height of the main crack : ； Wherein, v is the Poisson's ratio, E is the elastic modulus of the formation, H is the height of the main fracture, P0 is the fluid pressure in the construction stage; Step S23, according to the maximum crack width, liquid explosive critical initiation diameter and hydraulic fracturing design half crack length, the length L at the liquid explosive critical initiation diameter is calculated d : ； where L is the half fracture length of the hydraulic fracture design, is the critical initiation diameter of the liquid explosive, is the maximum fracture width; Step S24, based on the length at the critical initiation diameter of the liquid explosive, the maximum crack width, and the critical initiation diameter of the liquid explosive, the volume of the liquid explosive is calculated : ； Step S3, the liquid explosive with adjusted viscosity is pumped into the hydraulic fracture in the horizontal well; Step S4, based on the distributed optical fiber monitoring device, monitoring data after the liquid explosive is detonated is obtained, the reservoir reconstruction effect of the detonation fracturing is evaluated by inverting the monitoring data, and the stress-strain state of the reservoir after the detonation fracturing is detected. The distributed optical fiber monitoring device is installed on the detonation fracturing monitoring device based on the tracer monitoring and the distributed optical fiber sensing monitoring.

2. A method of monitoring a detonation fracturing based on a tracer and a distributed optical fiber sensing according to claim 1, characterized in that, The distributed optical fiber monitoring device comprises one or more of a distributed temperature optical fiber sensor, a distributed acoustic optical fiber sensor and a distributed strain optical fiber sensor.

3. A method of monitoring a detonation fracturing based on a tracer and a distributed optical fiber sensing according to claim 1, characterized in that, The distributed optical fiber monitoring device is installed on the outer circumferential surface of the casing near one side of each perforating port.

4. A method of monitoring a detonation fracturing based on a tracer and a distributed optical fiber sensing according to claim 3, characterized in that, The distributed optical fiber monitoring device is installed in the optical fiber hub column, and the optical fiber hub column is installed on the outer circumferential surface of the casing near the edge of each perforating port.

5. A tracer-based monitoring and distributed optical fiber sensing monitoring method for monitoring of the detonation fracturing according to claim 4, characterized in that, The axial direction of the optical fiber hub column is perpendicular to the axial direction of the casing.

6. A tracer monitoring and distributed optical fiber sensing monitoring apparatus for monitoring of a detonation fracturing based on any one of claims 1-5, wherein, The device comprises a bridge plug (1), an initiator (2), a safety gun (3), a centralizer (4), a packer (5), an optical fiber hub column (6), a perforating port (7) and a casing (8); The casing (8) is arranged in the horizontal well in a horizontal manner, a plurality of perforating ports (7) are uniformly arranged on both sides of the surface of the casing (8) along the length direction, the perforating ports (7) on one side are staggered with the perforating ports (7) on the other side, and an optical fiber hub column (6) is arranged at the edge of each perforating port (7), and the optical fiber hub column (6) is fixed on the outer surface of the casing (8); A plurality of centralizers (4) are coaxially arranged on the outer surface of the casing (8), and the centralizers (4) are used for centralizing the casing (8); From the end near the vertical well to the other end, the packer (5), the initiator (2) and the safety gun (3) are arranged in sequence in the casing (8); the initiator (2) is used for detonating the liquid explosive, and the safety gun (3) is used for transmitting the detonation signal to the initiator (2); The bridge plug (1) is arranged on the well wall near the vertical well of the horizontal well, and the bridge plug (1) is used for preventing the backflow of the liquid explosive and the fluid in the hydraulic fracturing process.

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