Simulation device for monitoring stress wall effect of three-dimensional well pattern based on optical fiber

Abstract

The invention belongs to the technical field of oil and gas field development, and discloses a three-dimensional well pattern stress wall effect simulation device based on optical fiber monitoring, which comprises a monitoring system, a true triaxial confining pressure system and a pump drainage pressurization system, rock blocks are placed in the true triaxial confining pressure system, and the interiors of the rock blocks are not layered or are separated by at least one interlayer; a plurality of simulation horizontal wells are arranged in the rock block, and the simulation horizontal wells are longitudinally distributed in a staggered mode and transversely arranged at intervals to form a plurality of well groups; an optical fiber is arranged in a shaft of each simulated horizontal well and is connected with a monitoring system; a hole is formed in the well wall of each simulation horizontal well in a penetrating mode, and a pressure meter is installed at the tail end of a well shaft; the well group is connected with the pumping and discharging pressurization system through a pipeline, and the pumping and discharging pressurization system is used for injecting fracturing fluid into the well group in a pressurized mode or pumping and discharging the fracturing fluid from the well group. The device can explore the three-dimensional well pattern stress wall effect in a laboratory, and analyzes the effectiveness and multi-parameter influence mechanism of the three-dimensional well pattern stress wall partition effect under different influence factor conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and particularly relates to a simulation device for stress wall effect based on fiber optic monitoring of a three-dimensional well pattern. Background Art

[0002] Tight conglomerate reservoirs often exhibit characteristics of complex lithology, strong heterogeneity, and complex fracture networks. In the development process, the large-scale hydraulic fracturing technology of three-dimensional well patterns is widely used. Among them, the local stress increase caused by the induced stress of the first fractured well will cause the fractures of the subsequent fractured wells to extend to the locally stressed area of the first fractured well, resulting in the phenomenon that the fractures stop propagating forward and turn to form complex fracture networks or fracture arrest, which is called the stress wall effect. Making full use of the stress wall effect can control the shape of the fracture network through stress, and assist in forming a fracture network with a simple near-well zone and a complex far-well zone. During the development of horizontal wells, by using the shielding effect of the stress wall effect, it is possible to simultaneously achieve development, fracturing, and drilling, thereby improving the production and development efficiency. Therefore, the stress wall effect plays an important and positive role in the development of three-dimensional well patterns and is one of the key technical means for the development of three-dimensional well patterns.

[0003] At present, the mechanism and main controlling factors of the stress wall effect on fracture propagation are not clear, which restricts the popularization and application of this technology in the field. Therefore, studying the parameter optimization of the stress wall effect during the development of three-dimensional well patterns plays an important guiding role in subsequent engineering development.

[0004] The invention patent CN111609967A discloses a test device and method for a distributed fiber optic monitoring device, belonging to the field of oil and gas well testing instruments; the test device includes: a casing, a tubing, an optical fiber, a gas source, and a liquid source. Both ends of the casing are closed ends, the casing is sleeved on the tubing, an annulus is formed between the casing and the tubing, an inlet and outlet liquid pipe is provided on the casing, and the inlet and outlet liquid pipe is used to communicate with the liquid source. Both ends of the tubing are closed ends, at least one leakage point is provided on the tubing, and the tubing communicates with the annulus through the leakage point. The tubing is used to communicate with the gas source, and the optical fiber is inserted into the tubing. The optical fiber includes a first end for connecting with a distributed fiber optic monitoring device, and both the first end and the second end of the optical fiber are arranged outside the casing and the tubing. This invention patent can verify the feasibility of using distributed fiber optic monitoring technology to monitor the leakage of gas storage wellbores and the reliability of detection results. However, the device of this patent is only used to monitor wellbore leakage and does not involve the stress wall effect. Summary of the Invention

[0005] The present invention aims to solve the technical problems existing in the background art, and provides a simulation device for the stress wall effect of a three-dimensional well pattern based on optical fiber monitoring, which can explore the stress wall effect of the three-dimensional well pattern in the laboratory, and analyze the effectiveness of the barrier effect of the stress wall of the three-dimensional well pattern and the influencing mechanism of multiple parameters under different influencing factor conditions.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A simulation device for the stress wall effect of a three-dimensional well pattern based on optical fiber monitoring, comprising a monitoring system, a true triaxial confining pressure system, and a pumping and pressurizing system;

[0008] A rock block is placed inside the true triaxial confining pressure system. If the interaction mechanism of stress walls between different layers of the three-dimensional well pattern is to be explored, at least 1 partition layer is provided inside the rock block to separate the rock block and the simulated horizontal wells into upper and lower layers; if the stress interference between wells in the same layer is to be explored, no partition layer is provided inside the rock block;

[0009] A plurality of simulated horizontal wells are arranged inside the rock block. The simulated horizontal wells are longitudinally staggered and transversely spaced to form several well groups; an optical fiber is arranged in the wellbore of each simulated horizontal well, and the optical fiber is connected to the monitoring system; holes are penetrated through the well wall of each simulated horizontal well, and a pressure gauge is installed at the end of the wellbore;

[0010] The well groups are connected to the pumping and pressurizing system through pipelines, and the pumping and pressurizing system is used to inject fracturing fluid into the well groups under pressure or pump the fracturing fluid out of the well groups.

[0011] Further, a housing and a motor drive device are arranged outside the true triaxial confining pressure system, and the two sides of the bottom of the housing are engaged with the motor drive device to form a formation dip rotation system.

[0012] Furthermore, rotating teeth are provided on both sides of the bottom of the housing. The motor drive device includes a driving device and a gear. The driving device is drivingly connected to the gear. The gear meshes with the rotating teeth on both sides of the bottom plate of the housing, and the housing is deflected at a set angle under the drive of the driving device.

[0013] Further, the optical fiber is a DAS optical fiber or a DTS optical fiber.

[0014] Further, the holes on any two adjacent simulated horizontal wells are staggered.

[0015] Furthermore, the shape of the holes is one or a combination of round holes, vertical slots, or horizontal slots.

[0016] Further, the monitoring system includes a distributed optical fiber monitoring device and an interpretation module;

[0017] The fiber optic connection explanation module is used to transmit detection signals to the explanation module in real time;

[0018] The explanation module is connected to the distributed fiber optic monitoring device, and is used to compile and interpret signals and transmit them to the distributed fiber optic monitoring device to observe and record the expansion and change of the fracture morphology in the horizontal well under pre-pressure.

[0019] Furthermore, the pumping and pressurizing system includes a valve system, a pumping system, a pressurizing system and a liquid storage tank;

[0020] The simulated horizontal wells of several well groups are respectively connected to the valve system through pipelines. The valve system is respectively connected to the pumping system and the pressurizing system. The pumping system and the pressurizing system are both connected to the liquid storage tank through pipelines. The liquid storage tank stores fracturing fluid.

[0021] Even further, the number of well groups is N, N≥2; the simulated horizontal wells of N well groups are correspondingly connected to N valve systems through pipelines, and (N - 1) pumping systems are connected in series between the N valve systems.

[0022] Compared with the prior art, the beneficial effects produced by the present invention are:

[0023] (1) The device of the present invention separates the rock blocks up and down through an interlayer. The rock blocks are longitudinally staggered and horizontally spaced into N well groups. The simulated horizontal wellbore walls of each well group are provided with holes, and optical fibers are arranged in the wellbore. The optical fibers are connected to the monitoring system to monitor the development and change of fractures near the wellbore in real time, and transmit the information to the monitoring system for analysis, observation and recording in real time; the device of the present invention has universality and can analyze the influence of various parameters on the stress wall partition effect of the three-dimensional well pattern. By changing parameters such as the stress state of the true triaxial confining pressure system, the formation dip angle, the perforation type, the well pattern well spacing distribution, the combination of longitudinal rock interlayers, the fracturing fluid viscosity, the waiting time, the multi-well fracturing sequence, the ambient temperature, the fracturing displacement, etc., the effectiveness of the stress wall partition effect of the three-dimensional well pattern under different influencing factor conditions and the multi-parameter influence mechanism can be analyzed. Moreover, the device has a simple structure, is easy to maintain, has convenient operation, low cost, and is conducive to popularization and application;

[0024] (2) The device of the present invention is provided with a formation dip angle rotation system. By arranging a housing around the true triaxial confining pressure system and the base, and the two sides of the bottom of the housing are meshed with the motor drive device, the housing can drive the whole device to deflect at a set angle under the drive of the drive device, so as to realize the analysis and evaluation of the stress wall effect mechanism of the three-dimensional well pattern for simulation experiments under different dip angles. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the stress wall effect simulation device according to Embodiment 1 of the present invention;

[0026] Figure 2 Schematic cross-sectional view of the stress wall effect simulation device according to Embodiment 1 of the present invention;

[0027] Figure 3 Schematic diagram of the well layout position of the stress wall effect simulation device according to Embodiment 1 of the present invention;

[0028] Figure 4 Schematic cross-sectional view of the stress wall effect simulation device according to Embodiment 2 of the present invention;

[0029] Figure 5 Schematic diagram of the well layout position of the stress wall effect simulation device according to Embodiment 3 of the present invention;

[0030] Figure 6 Monitoring result graph of the acoustic wave signal response according to Embodiment 3 of the present invention. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "center", "both ends", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention.

[0033] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "set", "connected", "fixed", "swivelly connected", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements. Unless otherwise clearly limited, those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

[0034] Embodiment 1

[0035] The embodiment of the present invention provides a fiber optic monitoring three-dimensional well pattern stress wall effect simulation device, as Figures 1-3As shown, it includes a monitoring system, a true triaxial confining pressure system 1, and a pumping and pressurizing system; the monitoring system includes a distributed optical fiber monitoring device 16 and an interpretation module 15, and the pumping and pressurizing system includes a valve system 9, a pumping system 10, a pressurizing system 11, and a liquid storage tank 12.

[0036] The true triaxial confining pressure system 1 is fixedly arranged on a base 8, and the true triaxial confining pressure system 1 is used to apply true triaxial confining pressure to the rock blocks inside; the rock blocks include an upper formation rock block 2 and a lower formation rock block 6, and the two are separated by a partition layer 5 in a layered manner.

[0037] In some other embodiments, there can be multiple partition layers 5 to explore the interaction mechanism of stress walls between multi-layer formations; if exploring the stress interference between wells in the same formation, there is no need to set partition layers inside the rock blocks.

[0038] There are 15 simulated horizontal wells 4 arranged inside the rock blocks. The 15 simulated horizontal wells 4 are longitudinally staggered and transversely spaced to form 3 well groups, as Figure 3 shown, which are the first well group 301, the second well group 302, and the third well group 303 respectively; there are two simulated horizontal wells 4 at the upper part of each well group and three simulated horizontal wells 4 at the lower part.

[0039] An optical fiber pipeline 13 is also arranged in the wellbore of each simulated horizontal well 4. An optical fiber 3 is lowered into the optical fiber pipeline 13, and the optical fiber 3 is connected to the interpretation module 15 for transmitting detection signals to the interpretation module 15 in real time; the interpretation module 15 is connected to the distributed optical fiber monitoring device 16 for compiling and interpreting signals and transmitting them into the distributed optical fiber monitoring device 16 to observe and record the expansion and change of the crack morphology in the pre-pressed horizontal well; perforations 7 are penetrated through the wellbore wall of each simulated horizontal well 4 for simulating well seam fracturing experiments; a pressure gauge 14 is installed at the end of the wellbore of each simulated horizontal well 4 for real-time monitoring of the pressure change of the fracturing fluid in the wellbore, and together with the distributed optical fiber monitoring device 16, it quantifies the stress wall effect to realize the mechanism analysis and evaluation of the stress wall effect simulation experiment of the three-dimensional well pattern.

[0040] The simulated horizontal wells 4 of the 3 well groups are respectively connected to the valve system 9 through pipelines. The valve system 9 is respectively connected to the pumping system 10 and the pressurizing system 11. The pumping system 10 and the pressurizing system 11 are both connected to the liquid storage tank 12 through pipelines. The liquid storage tank 12 stores fracturing fluid (high-temperature fracturing fluid or low-temperature fracturing fluid); the pumping system 10 is used to pump the fracturing fluid in the well group out to the liquid storage tank 12, and the pressurizing system 11 is used to pressurize and extract the fracturing fluid in the liquid storage tank 12 to the well group for carrying out the simulation experiment of the stress wall effect generated by inter-well fracturing in the three-dimensional well pattern.

[0041] In some other embodiments, the holes 7 on any two adjacent simulated horizontal wells 4 are arranged staggeredly, and the shape of the holes 7 is one or a combination of shapes such as round holes, vertical slots 701, or horizontal slots 702, etc.

[0042] In some other embodiments, the simulated horizontal wells 4 of the three well groups are correspondingly connected to three valve systems 9 through pipelines, and two pumping and drainage systems 10 are connected in series between the three valve systems 9, which can reduce the number of required pumping and drainage systems and simplify the system structure.

[0043] The simulation device for the stress wall effect of the stereoscopic well pattern based on optical fiber monitoring according to the embodiment of the present invention can be implemented based on DAS optical fiber or DTS optical fiber.

[0044] Embodiment 2

[0045] The embodiment of the present invention provides a simulation device for the stress wall effect of the stereoscopic well pattern based on optical fiber monitoring, which is provided with a formation dip angle rotation system on the basis of Embodiment 1.

[0046] In the embodiment of the present invention, as Figure 4 shown, a housing 18 and a motor drive device 17 are further provided outside the true triaxial confining pressure system 1 and the base 8, and the two sides of the bottom of the housing 18 are meshed with the motor drive device 17 to form a formation dip angle rotation system, so as to realize the analysis and evaluation of the simulation experiment mechanism of the stress wall effect of the stereoscopic well pattern under different dip angles.

[0047] Specifically, rotating teeth are provided on both sides of the bottom of the housing 18, the motor drive device 17 includes a driving device and a gear, the driving device is drivingly connected to the gear, the gear is meshed with the rotating teeth on both sides of the bottom plate of the housing 18, and the housing 18 drives the whole device to deflect at a set angle under the drive of the driving device.

[0048] Embodiment 3

[0049] The embodiment of the present invention provides a simulation method for the stress wall effect of the stereoscopic well pattern based on DAS optical fiber monitoring, which is implemented by using the device in Embodiment 1 or 2. The method includes the following steps:

[0050] Step S1: Arrange each simulated horizontal well 4 into the rock block, and ensure that each simulated horizontal well 4 is staggered in the three-dimensional space. At the same time, the holes 7 arranged on different simulated horizontal wells are also staggered in the three-dimensional space; there is one interlayer 5 inside the rock block, which divides the rock block and the simulated horizontal wells into upper and lower layers;

[0051] Step S2: Place the rock block into the true triaxial confining pressure system 1, start the true triaxial confining pressure system 1, and pressurize the rock block according to the set confining pressures.

[0052] Step S3: After the system stabilizes, fracture the three well groups ( Figure 3 the first well group 301, the second well group 302, and the third well group 303 in

[0053] ) in different fracturing sequences to generate fractures. Monitor the fracture propagation morphology of the well groups through optical fibers, and monitor the change of the well group pressure over time through pressure gauges;

[0054] Step S4: Deflect the experimental device by a set angle to achieve the stress wall effect fracturing simulation under different formation dip angles;

[0055] Step S5: According to the experimental results, analyze and evaluate the effectiveness of the stress wall effect, including the effectiveness of different fracturing pressure parameters, different fracturing sequences (including different fracturing sequences of wells in the same layer and different fracturing sequences between wells in different layers), and parameters and influencing factors such as different dip angles on the stress wall partition effect, and complete the mechanism analysis and evaluation of the stress wall effect simulation experiment of the three-dimensional well pattern.

[0056] Among them, in the said step S3, fracturing the three well groups in different fracturing sequences to generate fractures specifically includes:

[0057] A. Unidirectional fracturing sequence to explore the influence of the stress wall effect of the three-dimensional well pattern with unidirectional sequence fracturing on the propagation direction of the fracture tip of the later fractured well, specifically including:

[0058] Step S311: First, fracture the first well group 301. After the fracturing of the first well group 301 is completed, do not relieve the pressure. Keep the pore pressure of the well group unchanged through the pressurization system 11, and stand by;

[0059] Step S312: After the waiting time t1, start fracturing the second well group 302; after the fracturing of the second well group 302 is completed, do not relieve the pressure. Keep the pressure in the well unchanged through the pressurization system 11, and stand by;

[0060] Step S313: After the waiting time t1, start fracturing the third well group 303. Obtain the fracture distribution of the rock sample through the distributed optical fiber monitoring device 16, observe the change of the fracture response of the later fractured well, and simultaneously observe and record the change of the pressure gauge 14 of the first well group 301 over time; after the fracturing and recording are completed, relieve the pressure of all well groups and open the pumping system 10 to pump out the fluid in the well groups;

[0061] B. Synchronous zipper - type fracturing sequence is adopted to explore whether there is an inhibitory effect during the "across - wall" flow process of the post - well - killing fracturing fluid, specifically including:

[0062] Step S321: First, fracture the first well group 301. After the fracturing of the first well group 301 is completed, do not relieve the pressure. Keep the pore pressure of the well group unchanged through the pressurization system 11 and wait statically.

[0063] Step S322: After the waiting time t2, start fracturing the third well group 303. After the fracturing of the third well group 303 is completed, do not relieve the pressure. Keep the pore pressures of the first well group 301 and the third well group 303 unchanged through the pressurization system 11 and wait statically.

[0064] Step S323: After the waiting time t2, start fracturing the second well group 302. Meanwhile, record the change of the fracture morphology with time within the horizontal well length range monitored by the distributed optical fiber monitoring device 16 of the first well group 301 and the third well group 303, as well as the pressure change of the pressure gauge 14. After the fracturing and recording are completed, relieve the pressure of all well groups and pump out the fluid in the well groups outward.

[0065] C. Implement different fracturing schemes for the simulated horizontal wells in the upper and lower formation rock blocks of the interlayer to explore the blocking effect of stress walls at different horizons, specifically including:

[0066] Step S331: First, fracture the lower well group of the first well group 301. After the fracturing is completed, do not relieve the pressure. Keep the pore pressure of the lower well group of the first well group 301 unchanged through the pressurization system 11 and wait statically.

[0067] Step S332: After the waiting time t3, start fracturing the upper and lower well groups of the third well group 303. Meanwhile, relieve the pressure of the lower well group of the first well group 301 and open the pumping - out system 10 to pump out the fluid in the lower well group of the first well group 301 outward. After the fracturing, keep the pore pressures of the upper and lower well groups of the third well group 303 unchanged and wait statically.

[0068] Step S333: After the waiting time t3, fracture the lower well group of the second well group 302. After the fracturing, keep the pore pressure of the lower well group of the second well group 302 unchanged and wait statically.

[0069] Step S334: After the waiting time t3, record the change of the fracture response with time of the upper and lower well groups of the first well group 301 and the third well group 303, as well as the pressure change of the pressure gauge 14. After the recording is completed, relieve the pressure of all well groups and open the pumping - out system 10 to pump out the fluid in the well groups outward.

[0070] In the said step S5, analyze and evaluate the effectiveness of the stress - wall effect, specifically including:

[0071] Step S501: Standardize the DAS acoustic wave signal to obtain the standardized acoustic wave signal data x. The formula for standardized data processing is as follows:

[0072]

[0073] In the above formula (1), x is the standardized acoustic wave signal data, and x * is the original acoustic wave signal data, μ is the mean of the original acoustic wave signal data, and σ is the variance of the original acoustic wave signal data;

[0074] Use the same method to standardize the pressure data to obtain the standardized pressure data p.

[0075] Step S502: The acoustic wave signal response data at a certain moment is continuous data. Take the difference between the standardized acoustic wave signal data at time t + 1 and time t to remove signal noise. Then, according to the denoised standardized acoustic wave signal data x, divide the acoustic wave signal response μ V (x) into grades as follows:

[0076]

[0077] In the above formula (2), μ V (x) is the acoustic wave signal response corresponding to the denoised standardized acoustic wave signal data x, and its values 0, 1, and 2 represent low, medium, and high acoustic wave signal responses respectively.

[0078] At the same time, the pressure data at a certain moment is discontinuous data and can be directly segmented. According to the standardized pressure data p, divide the pressure response μ S (p) into grades as follows:

[0079]

[0080] In the above formula (3), μ S (p) is the pressure response corresponding to the standardized pressure signal data p, and its values 0, 1, and 2 represent small, medium, and large pressure responses respectively.

[0081] Step S503: According to expert experience, determine the relationship between pressure response, acoustic wave signal response, and stress wall effect as follows:

[0082] If the pressure response is small and the acoustic wave signal response is low, the stress wall effect is strong;

[0083] If the pressure response is medium and the acoustic wave signal response is low, or the pressure response is small and the acoustic wave signal response is medium, the stress wall effect is relatively strong;

[0084] If the pressure response is small and the acoustic wave signal response is high, or if the pressure response is medium and the acoustic wave signal response is medium, then the stress wall effect is medium;

[0085] If the pressure response is large and the acoustic wave signal response is medium, or if the pressure response is medium and the acoustic wave signal response is large, then the stress wall effect is weak;

[0086] If the pressure response is large and the acoustic wave signal response is high, then the stress wall effect is weak;

[0087] If the pressure response is large and the acoustic wave signal response is low, then the data is abnormal.

[0088] According to the above corresponding relationships, applying the acoustic wave grading data and the pressure grading data, construct the stress wall effect function μ W (x, p) as follows:

[0089]

[0090] In the above formula (4), ε(x, p) is a step function, which is a value range function related to the acoustic wave signal response μ V (x) and the pressure response μ S (p), and the expression is as follows:

[0091]

[0092]

[0093] Among them, μ W (x1) is the stress wall effect function corresponding to the standardized acoustic wave detection signal data x1. Its value -2 indicates abnormal data, and its values 0, 1, 2, 3, and 4 respectively correspond to the five levels of the stress wall effect: weak, relatively weak, medium, relatively strong, and strong.

[0094] The corresponding relationships between the acoustic wave grading data, the pressure grading data, and the pressure wall effect are shown in Table 1-1 as follows:

[0095] Table 1-1 Corresponding Relationship Table of Acoustic Wave Grading Data, Pressure Grading Data, and Pressure Wall Effect

[0096]

[0097] According to the above corresponding relationships between the acoustic wave grading data, the pressure grading data, and the pressure wall effect, the quantitative evaluation of the stress wall effect for the three fracturing sequences in step S3 can be realized, specifically as follows:

[0098] For A. Unidirectional fracturing sequence:

[0099] If the DAS distributed fiber optic acoustic monitoring device of the first well group 301 detects a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a large pressure response of the pipeline pressure gauge, then the cracks in the second well group 302 penetrate the first well group 301, and the stress wall effect is weak;

[0100] If the DAS distributed fiber optic acoustic monitoring device of the first well group 301 detects a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a medium pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a large pressure response, then the stress wall effect is relatively weak;

[0101] If the DAS distributed fiber optic acoustic monitoring device of the first well group 301 detects a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a small pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a medium pressure response, then the stress wall effect is medium;

[0102] If the DAS distributed fiber optic acoustic monitoring device of the first well group 301 does not detect a low response of the acoustic signal of the fracturing cracks in the second well group 302 and a small pressure response of the pipeline pressure gauge, then the stress wall effect is strong.

[0103] For B. Synchronous zipper - type fracturing sequence:

[0104] If the DAS distributed fiber optic acoustic monitoring devices of the first well group 301 and the third well group 303 detect a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a large pressure response of the pipeline pressure gauge, then the cracks in the second well group 302 penetrate the first well group 301 and the third well group 303, and the stress wall effect is weak;

[0105] If the DAS distributed fiber optic acoustic monitoring devices of the first well group 301 and the third well group 303 detect a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a medium pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a large pressure response, then the stress wall effect is relatively weak;

[0106] If the DAS distributed fiber optic acoustic monitoring devices of the first well group 301 and the third well group 303 detect a high response of the acoustic signal of the fracturing cracks in the second well group 302 and a small pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a medium pressure response, then the stress wall effect is medium;

[0107] If the DAS distributed fiber optic acoustic monitoring devices of the first well group 301 and the third well group 303 do not detect a low response of the acoustic signal of the fracturing cracks in the second well group 302 and a small pressure response of the pipeline pressure gauge, then the stress wall effect is strong.

[0108] For C. Implementing different fracturing schemes for the simulated horizontal wells in the upper and lower rock blocks of the interlayer:

[0109] If the DAS distributed fiber optic acoustic monitoring device in the lower well groups of the first well group 301 and the third well group 303 detects a high response of the acoustic signal of the fracturing fracture in the lower well group of the second well group 302 and a large pressure response of the pipeline pressure gauge, then the fracture in the lower well group of the second well group 302 penetrates the lower well groups of the first well group 301 and the third well group 303, and the stress wall effect is weak;

[0110] If the DAS distributed fiber optic acoustic monitoring device in the lower well groups of the first well group 301 and the third well group 303 detects a high response of the acoustic signal of the fracturing fracture in the lower well group of the second well group 302 and a medium pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a large pressure response, then the stress wall effect is relatively weak;

[0111] If the DAS distributed fiber optic acoustic monitoring device in the lower well groups of the first well group 301 and the third well group 303 detects a high response of the fracturing acoustic signal in the lower well group of the second well group 302 and a small pressure response of the pipeline pressure gauge, or, a medium response of the acoustic signal and a medium pressure response, then the stress wall effect is medium.

[0112] If the DAS distributed fiber optic acoustic monitoring device in the lower well groups of the first well group 301 and the third well group 303 detects a low response of the acoustic signal of the fracturing fracture in the lower well group of the second well group 302 and a small pressure response of the pipeline pressure gauge, then the stress wall effect is strong.

[0113] Embodiment 4

[0114] The embodiment of the present invention uses the device in Embodiment 1 or 2 and the method in Embodiment 3 to conduct a simulation experiment on the stress wall effect of a three-dimensional well pattern based on DAS fiber optic monitoring for a certain conglomerate in a certain block.

[0115] As Figure 5 shown in the schematic diagram of the model of the rock block to be experimented, the rock block is processed from the conglomerate slab of the target block, and the size of the rock block is 1.2 m in length × 1.2 m in width × 1.2 m in height. Three groups of well patterns are horizontally drilled and deployed on the rock block, numbered as Well Pattern A, Well Pattern B, and Well Pattern C respectively. One well is deployed in each group of well patterns, arranged at equal intervals, and the well spacing is 0.4 m.

[0116] It should be additionally noted that in the embodiment of the present invention, the well pattern is deployed as a single-layer well. For the device of the present invention, it is possible to deploy the well pattern as a single-layer well or upper and lower multi-layer wells. Among them, the single-layer well is a simplified special case of the multi-layer well.

[0117] The simulated horizontal well and the DAS fiber are placed parallel into the rock block and sealed with cement, and then each device and pipeline are assembled and connected for the experiment. The experimental process is as follows:

[0118] (1) Turn on the true triaxial confining pressure system, apply a maximum horizontal stress of 35 Mpa, a minimum horizontal stress of 25 MPa, and an overlying rock pressure of 10 MPa, and conduct a fracturing simulation on the sample;

[0119] (2) During the fracturing process, open 2 clusters per well (fracture at two positions, one main fracture is one cluster), and each well pattern is fractured unidirectionally in the order of C - B - A to explore the stress wall effect under unidirectional sequential fracturing conditions. Monitor and record the acoustic signal responses of well pattern C (right) and well pattern A (left) at the end of the fracturing of well pattern B in the middle during fracturing. The results are as Figure 6 shown.

[0120] As can be seen from the figure, at the end of the fracturing of well pattern B, the acoustic signal responses of the 2 simulated perforation sections of well pattern B were monitored on well pattern A (the general trend is two wave peaks, and the remaining small wave peaks are signal noise), but there was no obvious acoustic signal response on well pattern C. This shows that the fracture network of well pattern B has a monitoring signal on well pattern A but no monitoring signal on well pattern C. Therefore, the stress field generated by fracturing well pattern C first blocked the rightward extension of the fractures in well pattern B.

[0121] Therefore, through the device and method of the embodiments of the present invention, it is possible to monitor the stress wall effect through DAS optical fibers, and by changing the analysis parameters (true triaxial confining pressure system stress state, formation dip angle, perforation type, well pattern well spacing distribution, combination of longitudinal rock layers, fracturing fluid viscosity, waiting time, multi - well fracturing sequence, environmental temperature, fracturing displacement, etc.), it is possible to analyze the effectiveness of the stress wall blocking effect and the multi - parameter influence mechanism under different influencing factor conditions.

[0122] The above are only the embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the scope of the application of the present invention shall be included within the protection scope of the present invention.

Claims

1. A simulation device for stress wall effect of a three-dimensional well pattern based on optical fiber monitoring, characterized in that It includes a monitoring system, a true triaxial confining pressure system, and a pumping and pressurizing system; A rock block is placed inside the true triaxial confining pressure system. If exploring the interaction mechanism of stress walls between different layers of a three-dimensional well pattern, at least one interlayer is provided inside the rock block to separate the rock block and the simulated horizontal wells into upper and lower layers; If exploring the stress interference between wells in the same layer system, no interlayer is provided inside the rock block; A plurality of simulated horizontal wells are arranged inside the rock block. The simulated horizontal wells are longitudinally staggered and transversely spaced to form several well groups; an optical fiber is arranged in the wellbore of each simulated horizontal well, and the optical fiber is connected to the monitoring system; holes are penetrated through the wellbore wall of each simulated horizontal well, and a pressure gauge is installed at the end of the wellbore; The well groups are connected to the pumping and pressurizing system through pipelines. The pumping and pressurizing system is used to inject fracturing fluid into the well groups under pressure or pump the fracturing fluid out of the well groups.

2. The device according to claim 1, characterized in that A housing and a motor drive device are arranged outside the true triaxial confining pressure system. The two sides at the bottom of the housing are meshed with the motor drive device to form a formation dip rotation system.

3. The device according to claim 2, characterized in that, Rotating teeth are arranged on both sides at the bottom of the housing. The motor drive device includes a driving device and a gear. The driving device is drivingly connected to the gear. The gear is meshed with the rotating teeth on both sides of the bottom plate of the housing and deflects the housing at a set angle under the drive of the driving device.

4. The device according to claim 1, characterized in that, The optical fiber is a DAS optical fiber or a DTS optical fiber.

5. The device according to claim 1, wherein, The holes on any two adjacent simulated horizontal wells are staggered.

6. The device according to claim 5, characterized in that, The shape of the holes is one or a combination of round holes, vertical slots, or horizontal slots.

7. The device according to any one of claims 1-6, characterized in that, The monitoring system includes a distributed optical fiber monitoring device and an interpretation module; The optical fiber is connected to the interpretation module and is used to transmit detection signals to the interpretation module in real time; The interpretation module is connected to the distributed optical fiber monitoring device and is used to compile and interpret signals and transmit them to the distributed optical fiber monitoring device to observe and record the expansion and change of the crack shape in the pre-pressed horizontal well.

8. The device according to any one of claims 1-6, characterized in that, The pumping and pressurizing system includes a valve system, a pumping system, a pressurizing system, and a liquid storage tank; The simulated horizontal wells of several well groups are respectively connected to the valve system through pipelines. The valve system is respectively connected to the pumping system and the pressurizing system. The pumping system and the pressurizing system are both connected to the liquid storage tank through pipelines. The liquid storage tank stores fracturing fluid.

9. The device according to claim 8, characterized in that The number of well groups is N, N≥2; the simulated horizontal wells of N well groups are correspondingly connected to N valve systems through pipelines, and (N - 1) pumping systems are connected in series between the N valve systems.

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