An experimental method for determining energy storage fracturing mode

Abstract

This article provides an experimental method for determining the energy storage fracturing mode, including: extracting multiple cores of the same lithology from the target reservoir; pre-saturating the multiple cores with oil; combining energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids to obtain multiple energy storage fracturing conditions; using multiple energy storage fracturing conditions to respectively fracture multiple cores treated with pre-saturated oil to obtain the fracture states of multiple fractured cores; soaking the multiple fractured cores by pressurized imbibition and spontaneous imbibition; after the soaking is completed, obtaining the recovery rate and soaking time corresponding to the multiple fractured cores; determining the energy storage fracturing effect of the multiple cores based on the fracture state and recovery rate; selecting the preferred cores from the multiple cores according to the energy storage fracturing effect of the multiple cores; determining the energy storage fracturing condition and soaking time corresponding to the preferred core as the energy storage fracturing condition and soaking time suitable for the lithology, and this article can select the energy storage fracturing condition and soaking time suitable for the lithology.

Description

Technical Field

[0001] The invention relates to the field of oil and gas development, and in particular to an experimental method for determining an energy storage fracturing mode. Background Art

[0002] The leap from the early conventional field to the later unconventional oil and gas field in oil and gas exploration and development is an inevitable trend in the development of the petroleum industry. The main way to develop tight oil is to use the exhaustion of formation energy, and the single well production is low and decreases rapidly. Nowadays, the supplement of formation energy is the key to improving the production and recovery rate of tight reservoirs. Volume fracturing not only has the function of creating fractures, but also can effectively supplement the formation energy through well soaking after the fracturing fluid enters the formation. After the well soaking is completed, the reservoir is depressurized and exploited, and the high-energy fracturing fluid drives the oil and gas production, which plays a role in energy storage and production increase.

[0003] At present, most of the existing technologies are based on indoor experiments of energy storage fracturing to study the impact of energy storage fracturing on crack expansion or the impact on recovery rate. There is a lack of overall quantitative evaluation of the effect of energy storage fracturing, which leads to the inability to select energy storage fracturing fluids, energy storage methods, and their corresponding displacement and well soaking time suitable for different lithological reservoirs. Therefore, there is an urgent need for an experimental method to determine the energy storage fracturing mode, which can accurately analyze the effect of energy storage fracturing through energy storage fracturing experiments, and then select energy storage fracturing fluids, energy storage methods, and their corresponding displacement and well soaking time suitable for lithological reservoirs. Summary of the invention

[0004] The purpose of the embodiments of this article is to provide an experimental method for determining the energy storage fracturing mode, so as to accurately analyze the energy storage fracturing effect, and then select the energy storage fracturing fluid, energy storage method and its corresponding displacement and well soaking time suitable for the lithological reservoir.

[0005] To achieve the above objectives, on the one hand, the embodiments of this invention provide an experimental method for determining the energy storage fracturing mode, including:

[0006] Extract multiple cores corresponding to the same lithology from the target reservoir;

[0007] pre-saturating the plurality of cores with oil;

[0008] Combining energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids to obtain a variety of energy storage fracturing conditions;

[0009] Using a variety of energy storage fracturing conditions, multiple cores treated with pre-saturated oil are fractured to obtain the fracture states of multiple fracturing cores;

[0010] Well soaking was performed on multiple fractured cores through pressure imbibition and spontaneous imbibition;

[0011] When the well soaking is completed, the recovery factors and soaking times corresponding to multiple fracturing cores are obtained;

[0012] Determine the energy storage fracturing effect of multiple cores based on the fracture state and the recovery rate;

[0013] According to the energy storage fracturing effects of multiple cores, the preferred cores are selected from the multiple cores;

[0014] The energy storage fracturing conditions and well soaking time corresponding to the preferred core are determined as energy storage fracturing conditions and well soaking time suitable for the lithology.

[0015] Preferably, before the pre-saturation oil treatment of the plurality of cores, the method further comprises:

[0016] Processing multiple cores into cylindrical shapes of equal size, and drilling non-penetrating wellbores with pre-installed wellbores at the centers of end faces of one end of the multiple cylindrical cores; wherein the diameters of the multiple cylindrical cores are all smaller than the set diameter;

[0017] The core is washed for oil and impurities and then dried.

[0018] Preferably, after the pre-saturation oil treatment of the plurality of cores, the method further comprises:

[0019] A sealant or a rubber tube with pressure bearing capacity is used to respectively wrap and seal a plurality of cores treated with pre-saturated oil except for the wellbore section;

[0020] The open hole section is reserved, and the non-metallic wellbore is prepared with pressure-bearing materials for cementing.

[0021] Preferably, the energy storage fracturing methods with different displacements include:

[0022] An energy storage fracturing method of fracturing with a set displacement after energy storage in a small displacement and an energy storage fracturing method of directly fracturing with a large displacement, wherein the small displacement is smaller than the set displacement and the large displacement is larger than the set displacement.

[0023] Preferably, the soaking of the plurality of fractured cores by pressurized imbibition and spontaneous imbibition further comprises:

[0024] A plurality of fractured cores are subjected to nuclear magnetic resonance scanning while being soaked by pressure imbibition and spontaneous imbibition to obtain nuclear magnetic resonance scanning curves during pressure imbibition and spontaneous imbibition; wherein the nuclear magnetic resonance scanning curves are used to characterize the relationship between the change of nuclear magnetic resonance signal and relaxation time;

[0025] According to the nuclear magnetic resonance scanning curve, a curve of nuclear magnetic resonance recovery rate changing with time is obtained.

[0026] Preferably, obtaining a curve of change of nuclear magnetic recovery rate over time according to the nuclear magnetic scanning curve further comprises:

[0027] The nuclear magnetic recovery rate corresponding to any time can be calculated by the following formula:

[0028]

[0029] Among them, η' is the nuclear magnetic recovery factor, A2 is the integral of the nuclear magnetic signal intensity over the relaxation time at any time, and A1 is the integral of the nuclear magnetic signal intensity over the relaxation time when the well is started to be soaked.

[0030] Preferably, after the well soaking is completed, obtaining the recovery factors and soaking times corresponding to the multiple fracturing cores further comprises:

[0031] The time from the start time of soaking to the end time of soaking is determined as the soaking time corresponding to the fracturing core;

[0032] The nuclear magnetic recovery rate corresponding to the end of the well soaking in the curve of the change of nuclear magnetic recovery rate over time is determined as the recovery rate corresponding to the fracturing core.

[0033] Preferably, after the well soaking is completed, obtaining the recovery factors and soaking times corresponding to the multiple fracturing cores further comprises:

[0034] The time from the start time of soaking to the end time of soaking is determined as the soaking time corresponding to the fracturing core;

[0035] The fractured cores after soaking were weighed and the corresponding recovery factor of the fractured cores was calculated.

[0036] Preferably, weighing the fractured core after soaking to calculate the recovery factor corresponding to the fractured core further comprises:

[0037] The recovery rate corresponding to the fractured core is calculated by the following formula:

[0038]

[0039] Where η is the recovery factor, m1 is the mass of the core before pre-saturated oil treatment, m2 is the mass of the fracturing core before the start of soaking, m3 is the mass of the fracturing core after the end of soaking, v is the volume of the energy storage fracturing fluid injected before the start of soaking, ρ is the density of the energy storage fracturing fluid, and f w It is the water content of the fluid discharged after the well is soaked.

[0040] Preferably, the step of comprehensively considering the fracture state and the recovery rate to determine the energy storage fracturing effects of multiple cores further comprises:

[0041] Performing weighted summation on the fracture state and the fracture state weight, and the recovery rate and the recovery rate weight to obtain energy storage fracturing effect scores of multiple cores;

[0042] Accordingly, selecting the preferred cores from the multiple cores according to the energy storage fracturing effects of the multiple cores further includes:

[0043] The multiple cores are sorted according to the energy storage fracturing effect scores, and the preferred cores are screened out according to the sorting.

[0044] It can be seen from the technical solutions provided in the above embodiments of this article that, through the method of this article, after fracturing multiple cores respectively under a variety of energy-storage fracturing conditions, the energy-storage fracturing effects of multiple cores can be determined by the fracture states and recovery rates of the multiple fractured cores. Further, the preferred cores can be screened out according to the energy-storage fracturing effects of the multiple cores, and the energy-storage fracturing conditions and soaking time corresponding to the preferred cores can be determined as the energy-storage fracturing conditions and soaking time suitable for the rock type.

[0045] In order to make the above and other purposes, features and advantages of this article more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of this article or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of this article. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 A schematic flow chart of an experimental method for determining an energy storage fracturing mode provided in an embodiment of this invention is shown;

[0048] Figure 2 A schematic diagram of a process flow before pre-saturation oil treatment of multiple cores provided in an embodiment of the present invention is shown;

[0049] Figure 3 A schematic diagram of a process after pre-saturation oil treatment of multiple cores provided in the embodiments of this invention is shown;

[0050] Figure 4 A schematic diagram showing the morphology of the core after cementing provided in the embodiments of this invention is shown;

[0051] Figure 5 A cross-sectional view of a plastic-sealed fracturing core provided in an embodiment of the present invention is shown in a core holder with a coil;

[0052] Figure 6 A schematic diagram of a process for soaking multiple fractured cores by pressure imbibition and spontaneous imbibition is shown in the embodiments of this document;

[0053] Figure 7A schematic diagram of a process for obtaining the recovery factors and well soaking times corresponding to a plurality of fracturing cores after well soaking is completed provided in the embodiment of this invention is shown;

[0054] Figure 8 Another schematic diagram of a process for obtaining the recovery factors and well soaking times corresponding to a plurality of fracturing cores after well soaking is completed provided in the embodiment of this invention is shown;

[0055] Fig. 9 A schematic diagram of the module structure of an experimental device for determining an energy storage fracturing mode provided in an embodiment of this invention is shown;

[0056] Fig.10 A schematic diagram of the structure of a computer device provided in an embodiment of this invention is shown.

[0057] Description of the accompanying symbols:

[0058] 1. Core;

[0059] 2. Non-metallic shaft;

[0060] 3. Naked hole section;

[0061] 4. Glass fiber core holder;

[0062] 5. Coil;

[0063] 6. Fracturing core;

[0064] 7. Plug;

[0065] 100. Extraction module;

[0066] 200, preprocessing module;

[0067] 300, combined module;

[0068] 400, fracturing module;

[0069] 500, stewing well module;

[0070] 600. Recovery factor and well soaking time determination module;

[0071] 700. Energy storage effect determination module;

[0072] 800, screening module;

[0073] 900. Determine module;

[0074] 1002. Computer equipment;

[0075] 1004. Processor;

[0076] 1006. Memory;

[0077] 1008. Driving mechanism;

[0078] 1010, input / output module;

[0079] 1012. Input device;

[0080] 1014. Output device;

[0081] 1016. Presentation equipment;

[0082] 1018. Graphical user interface;

[0083] 1020. Network interface;

[0084] 1022. Communication link;

[0085] 1024. Communication bus. DETAILED DESCRIPTION

[0086] The following will be combined with the drawings in the embodiments of this article to clearly and completely describe the technical solutions in the embodiments of this article. Obviously, the described embodiments are only part of the embodiments of this article, not all of the embodiments. Based on the embodiments of this article, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this article.

[0087] The leap from the early conventional field to the later unconventional oil and gas field in oil and gas exploration and development is an inevitable trend in the development of the petroleum industry. The main way to develop tight oil is to use the exhaustion of formation energy, and the single well production is low and decreases rapidly. Nowadays, the supplement of formation energy is the key to improving the production and recovery rate of tight reservoirs. Volume fracturing not only has the function of creating fractures, but also the fracturing fluid can effectively supplement the formation energy by entering the formation and shutting the well. After the well is shut, the reservoir is depressurized and exploited, and the high-energy fracturing fluid drives the oil and gas production, which plays a role in energy storage and production increase.

[0088] Currently, most of the existing technologies use indoor experiments on energy storage fracturing to study the impact of energy storage fracturing on crack expansion or on the recovery rate. There is a lack of overall quantitative evaluation of the effect of energy storage fracturing, which makes it impossible to optimize the energy storage fracturing fluid, energy storage method, and corresponding displacement and well soaking time suitable for different lithology reservoirs.

[0089] In order to solve the above problems, the embodiments of this article provide an experimental method for determining the energy storage fracturing mode. Figure 1This is a flow chart of an experimental method for determining an energy storage fracturing mode provided in the embodiments of this article. This specification provides method operation steps as described in the embodiments or flow charts, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiments is only one way of executing the order of many steps and does not represent the only execution order. When the system or device product is executed in practice, it can be executed in the order of the method shown in the embodiments or the drawings or in parallel.

[0090] It should be noted that the terms "first", "second", etc. in the specification and claims of this article and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of this article described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0091] Reference Figure 1 , an experimental method for determining energy storage fracturing mode, comprising:

[0092] S101: extracting multiple cores corresponding to the same lithology from the target reservoir;

[0093] S102: performing oil pre-saturation treatment on the plurality of cores;

[0094] S103: combining energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids to obtain a variety of energy storage fracturing conditions;

[0095] S104: fracturing a plurality of cores treated with pre-saturated oil using a plurality of energy storage fracturing conditions to obtain fracture states of the plurality of fracturing cores;

[0096] S105: soaking multiple fractured cores by pressure imbibition and spontaneous imbibition;

[0097] S106: After the well soaking is completed, the recovery factors and well soaking times corresponding to the multiple fracturing cores are obtained;

[0098] S107: Determine the energy storage fracturing effects of multiple cores by combining the fracture state and the recovery rate;

[0099] S108: selecting a preferred core from the multiple cores according to energy storage fracturing effects of the multiple cores;

[0100] S109: Determine the energy storage fracturing conditions and well soaking time corresponding to the preferred core as energy storage fracturing conditions and well soaking time suitable for the lithology.

[0101] The target reservoir can be any type of reservoir such as sandstone reservoir, shale reservoir, etc. For any type of reservoir, the lithology of the multiple cores extracted is the same. In addition to the same lithology, the multiple cores should also have similar physical properties. In order to accurately determine the energy storage fracturing mode, it is necessary to test the core fracturing conditions under various energy storage fracturing conditions, so it is necessary to extract multiple cores for experiments.

[0102] When conducting the experiment, multiple cores need to be pre-saturated with oil through S102. For any of the cores, the specific steps of the pre-saturated with oil treatment may be:

[0103] Step 1.1: Vacuum the core and saturate it with water;

[0104] Step 1.2: The core is passed through a high-speed centrifuge to generate bound water, and then weighed to obtain a first weight;

[0105] Step 1.3: Saturate the core with oil through a vacuum pressure saturation device or a displacement device, and weigh it to obtain a second weight;

[0106] Step 1.4: Calculate the saturated oil volume according to the first weight and the second weight;

[0107] Step 1.5: If the saturated oil volume is equal to the effective pore volume of the core, a core treated with pre-saturated oil is obtained.

[0108] Wherein, saturated oil weight=second weight-first weight, saturated oil volume=saturated oil weight / oil density.

[0109] After obtaining the core treated with pre-saturated oil, the core treated with pre-saturated oil can be placed in a nuclear magnetic resonance scanning device for scanning to obtain an initial nuclear magnetic resonance curve. The pore size distribution in the core can be determined based on the peak position and size of the initial nuclear magnetic resonance curve, which can be used to compare the imbibition effect and the soaking time.

[0110] Because the multiple cores in the experiment are for comparative experiments, in order to ensure the accuracy and persuasiveness of the comparative experiments, refer to Figure 2 , before the pre-saturation oil treatment is performed on the plurality of cores, the method further comprises:

[0111] S201: processing a plurality of cores into cylindrical shapes of equal size, and drilling a non-penetrating wellbore with a pre-installed wellbore at the center of one end surface of the plurality of cylindrical cores; wherein the diameters of the plurality of cylindrical cores are all smaller than a set diameter;

[0112] S202: Wash the core for oil and impurities and then dry it.

[0113] In order to meet the environmental requirements of the laboratory, the set diameter can be selected to be less than 25cm.

[0114] When executing S202, the core needs to be repeatedly placed in a vacuum drying oven during the drying process. The core is taken out after 24 hours and weighed once to obtain the core mass at that time. The above steps are repeated until the core mass obtained by continuous weighing does not decrease. At this time, the core is in a state of drying completion.

[0115] Reference Figure 3 In order to completely simulate the state of fracturing through the wellbore in the actual formation under laboratory conditions, the pre-saturation oil treatment of the plurality of cores further includes:

[0116] S301: using sealant or a rubber tube with pressure bearing capacity to respectively wrap and seal a plurality of cores treated with pre-saturated oil except for the wellbore section;

[0117] S302: Reserve an open hole section, use pressure-bearing materials to prepare a non-metallic wellbore, and perform cementing.

[0118] The morphology of core 1 after cementing is as follows Figure 4 As shown, in Figure 4 A non-through wellbore is arranged at the center of one end face of the cylindrical core 1, and a non-metallic wellbore 2 is fixed to the wellbore section. The non-metallic wellbore 2 does not completely cement the wellbore section, but leaves an open hole section 3. Before cementing, the core 1, except for the wellbore section, is completely sealed with sealant or provided with a rubber tube. The purpose is to prevent the volatilization of the crude oil in the core after the pre-saturation of oil. Therefore, the core is first wrapped and then cemented. The sealant can be a silicone sealant, and of course it can also be other suitable sealants. The pressure-bearing material can be a PEEK material, and of course it can also be other suitable materials. This article does not limit this. Cementing can be carried out by gluing, or by any other method that can be implemented by a person skilled in the art, which will not be repeated in this article.

[0119] In S103, energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids can be combined to obtain a variety of energy storage fracturing conditions. Multiple cores are fractured using the multiple energy storage fracturing conditions, and the fracturing effects of the multiple energy storage fracturing conditions are reflected based on the performance of the multiple cores after fracturing.

[0120] The energy storage fracturing methods with different displacements include:

[0121] An energy storage fracturing method of fracturing with a set displacement after energy storage in a small displacement and an energy storage fracturing method of directly fracturing with a large displacement, wherein the small displacement is smaller than the set displacement and the large displacement is larger than the set displacement.

[0122] It should be noted that the set displacement is different according to different lithologies. The set displacement is the displacement when conventional fracturing is performed on the corresponding lithology under laboratory conditions. For example, shale and sandstone are two different lithologies, so the set displacements of shale and sandstone are different.

[0123] The energy storage fracturing method of small-volume energy storage followed by set-volume fracturing is as follows: first inject energy storage fluid into the core at a small displacement to store energy, and then inject fracturing fluid into the core at a set displacement after the pore pressure of the core reaches the expected value. During the small-volume energy storage period, no obvious cracks will occur in the core, and injecting fracturing fluid at a set displacement will cause cracks in the core. The energy storage fracturing method of large-volume direct fracturing is as follows: directly inject energy storage fracturing fluid into the core at a large displacement, and injecting energy storage fracturing fluid at a large displacement will cause cracks in the core.

[0124] Furthermore, the two energy storage fracturing methods can correspond to multiple displacements. For example, the energy storage fracturing method of small-displacement energy storage followed by set-displacement fracturing may include: A-displacement energy storage followed by set-displacement fracturing, B-displacement energy storage followed by set-displacement fracturing...where A and B both belong to small displacements; the energy storage fracturing method of large-displacement direct fracturing may include: M-displacement direct fracturing, N-displacement direct fracturing...where M and N both belong to large displacements.

[0125] Furthermore, the energy storage fluid, the fracturing fluid and the energy storage fracturing fluid may include multiple types, which may be liquids or gases, such as produced water, carbon dioxide, and the like.

[0126] In this way, when different displacement energy storage fracturing methods and different types of energy storage fracturing fluids are combined, multiple combinations will be generated, and multiple energy storage fracturing conditions will be obtained. For example, the energy storage fracturing conditions are: fracturing with a set displacement after energy storage by produced water at a displacement of A, fracturing with a set displacement after energy storage by carbon dioxide at a displacement of A, fracturing with a set displacement after energy storage by produced water at a displacement of B…

[0127] For the fracturing process shown in S104, the fracturing process of any core may specifically include:

[0128] Step 2.1: Set up an acoustic emission monitoring probe on the core;

[0129] Step 2.2: placing the core provided with the acoustic emission monitoring probe in the pseudo-triaxial fracturing device;

[0130] Step 2.3: Using a temperature control system to heat the pseudo-triaxial fracturing device to a simulated formation temperature;

[0131] Step 2.4: Using a hydraulic pump to pressurize the pseudo-triaxial fracturing device to simulate triaxial ground stress;

[0132] Step 2.5: Use the pore pressure loading system to add pressure to the core pores to the pore pressure under formation conditions;

[0133] Step 2.6: After the pressure in the core pores is stable, close the pore pressure loading system;

[0134] Step 2.7: Perform energy storage fracturing on the core using energy storage fracturing conditions, monitor the pressure during the fracturing process, and stop fracturing until the pressure drops suddenly or the acoustic emission monitoring probe detects a high-intensity signal, confirming the initiation and extension of the crack;

[0135] Step 2.8: After stopping the pump, the pseudo-triaxial fracturing device is depressurized and the fracturing core is taken out;

[0136] Step 2.9: Determine the fracture status of the fractured core by CT scanning.

[0137] Among them, in order to simulate the actual working conditions as much as possible in the laboratory, the simulated formation temperature and the simulated three-dimensional geostress are set according to the formation temperature and the three-dimensional geostress under the actual working conditions. Of course, the simulated formation temperature may be different from the actual formation temperature, and the simulated three-dimensional geostress may be different from the actual three-dimensional geostress. The fracture state may include the distribution of the fracture and / or the fracture volume. The distribution of the fracture is the display and distribution form of the fracture, for example, the fracture is a main trunk fracture, or the fracture is a plurality of branched tree fractures.

[0138] Before soaking the multiple fractured cores by pressure imbibition and spontaneous imbibition in S105, the following steps may also be performed:

[0139] Step 3.1: using glass fiber to prepare a glass fiber core holder of a preset diameter, and preparing a coil matching the glass fiber core holder;

[0140] Step 3.2: The fracturing core is plastic-sealed and placed in a core holder with a coil;

[0141] Step 3.3: The front end of the glass fiber core holder is connected to the injection pipeline, and the rear end of the glass fiber core holder is connected to the oil outlet pipeline;

[0142] Step 3.4: Heat the fiberglass core holder to simulate the formation temperature and apply back pressure;

[0143] Step 3.5: Open the injection pipeline and inject the energy storage fracturing fluid into the fracturing core using the pressure when the pump is stopped during the fracturing process;

[0144] Step 3.6: After the pressure in the fracture of the fracturing core reaches the preset pressure and stabilizes, the injection pipeline and the oil flow pipeline are closed.

[0145] The moment when the injection pipeline is closed in step 3.6 is the start time of soaking.

[0146] The cross-sectional view of the plastic-sealed fracturing core in the core holder with coil is shown in Figure 5 As shown, when the fracturing core is installed and placed, the fracturing core 6 can be plastic-sealed first, and the plastic-sealed fracturing core 6 can be placed in the glass fiber core holder 4, plugs 7 are inserted into both ends of the glass fiber core holder 4, and then the outer part of the glass fiber core holder 4 is covered with a matching coil 5, wherein the plugs 7 at both ends are provided with channels, and the two channels are respectively used to connect the injection pipeline and the oil outlet pipeline.

[0147] Reference Figure 6 In the embodiments of this invention, the soaking of multiple fractured cores by pressure imbibition and spontaneous imbibition further comprises:

[0148] S401: performing nuclear magnetic resonance scanning on multiple fractured cores while soaking them through pressure imbibition and spontaneous imbibition to obtain nuclear magnetic resonance scanning curves during pressure imbibition and spontaneous imbibition; wherein the nuclear magnetic resonance scanning curves are used to characterize the relationship between nuclear magnetic resonance signals and relaxation time;

[0149] S402: Obtain a curve of change of nuclear magnetic recovery rate over time according to the nuclear magnetic scanning curve.

[0150] In order to achieve nuclear magnetic resonance scanning while the fracturing core is soaked by pressurized imbibition and spontaneous imbibition, after the fracturing core is plastic-sealed and placed in a core holder with a coil in the above step 3.2, the glass fiber core holder with the coil can be placed in a nuclear magnetic resonance scanning device, and the nuclear magnetic resonance scanning can be started by the nuclear magnetic resonance scanning device when the injection pipeline is closed in step 3.6.

[0151] During the soaking process, the fracturing fluid is imbibed from the fractures into the matrix under pressure in the fractured core. After the pressure of the fractures and the matrix is ​​balanced, the fractured core begins to imbibe spontaneously, and the fracturing fluid is imbibed to displace the crude oil.

[0152] Since the NMR recovery rate curve varying with time can be obtained based on the NMR scanning curve, the moment when the NMR recovery rate begins to stop changing with time is the end of the soaking, at which time the oil flow line can be opened to release pressure and discharge oil.

[0153] In the embodiment of this article, obtaining the curve of change of nuclear magnetic recovery rate over time according to the nuclear magnetic scanning curve further includes:

[0154] The nuclear magnetic recovery rate corresponding to any time can be calculated by the following formula:

[0155]

[0156] Among them, η' is the nuclear magnetic recovery factor, A2 is the integral of the nuclear magnetic signal intensity over the relaxation time at any time, and A1 is the integral of the nuclear magnetic signal intensity over the relaxation time when the well is started to be soaked.

[0157] Reference Figure 7 Further, after the well soaking is completed, the recovery factors and well soaking times corresponding to the multiple fracturing cores are obtained, which further includes:

[0158] S501: Determine the time from the start time of soaking to the end time of soaking as the soaking time corresponding to the fracturing core;

[0159] S502: Determine the nuclear magnetic recovery rate corresponding to the end of the soaking in the curve of the change of nuclear magnetic recovery rate over time as the recovery rate corresponding to the fractured core.

[0160] As explained above, for each core, the moment when the injection pipeline is closed is the start time of the soaking, and the moment when the nuclear magnetic recovery rate begins to stop changing with the increase of time is the end time of the soaking. The soaking time can be obtained based on the difference between the start time and the end time of the soaking.

[0161] In addition to the method for determining the recovery factor corresponding to the fracturing core described in S502, the recovery factor corresponding to the fracturing core may also be determined by other steps, specifically:

[0162] Reference Figure 8 , when the well soaking is completed, obtaining the recovery factor and well soaking time corresponding to the multiple fracturing cores further includes:

[0163] S601: Determine the time from the start time of soaking to the end time of soaking as the soaking time corresponding to the fracturing core;

[0164] S602: Weigh the fractured core after soaking, and calculate the recovery factor corresponding to the fractured core.

[0165] S602 is another method for determining the recovery factor corresponding to the fracturing core. However, it should be noted that when weighing the fracturing core after the soaking, the fracturing core can be taken out of the glass fiber core holder for weighing only when there is no crude oil flowing out of the oil pipeline.

[0166] In S602, in addition to weighing the fracturing core after the soaking, a scale can be connected to the end of the oil flow line to directly weigh the mass of crude oil in the fluid discharged after the soaking, thereby obtaining the weight of the fracturing core. However, since there may be residual oil in the oil flow line, such a method may affect the accuracy of the result. In the embodiment of this article, the weighing of the fracturing core after the soaking and the calculation of the recovery factor corresponding to the fracturing core further include:

[0167] The recovery rate corresponding to the fractured core is calculated by the following formula:

[0168]

[0169] Where η is the recovery factor, m1 is the mass of the core before pre-saturated oil treatment, m2 is the mass of the fracturing core before the start of soaking, m3 is the mass of the fracturing core after the end of soaking, v is the volume of the energy storage fracturing fluid injected before the start of soaking, ρ is the density of the energy storage fracturing fluid, and f w It is the water content of the fluid discharged after the well is soaked.

[0170] Furthermore, after obtaining the recovery factor corresponding to the fracturing core, the oil production can be further calculated, and the oil change efficiency can be calculated based on this. Specifically,

[0171] Oil production = saturated oil volume × recovery factor corresponding to the fractured core;

[0172]

[0173] Among them, the saturated oil volume refers to the saturated oil volume in the pre-saturated oil treatment process, and the energy storage fracturing fluid injection amount refers to the amount of energy storage fracturing fluid injected during the energy storage fracturing of the core in step 2.7 or the amount of energy storage fracturing fluid injected in step 3.5.

[0174] The oil exchange efficiency, like the recovery factor, can also be used to evaluate the energy storage fracturing effect of the fracturing core.

[0175] In this way, the fracture status, recovery rate, oil change efficiency and soaking time corresponding to multiple fracturing cores can be obtained. Each fracturing core represents a kind of energy storage fracturing condition, thereby demonstrating the energy storage fracturing effect under various energy storage fracturing conditions, namely the fracture status and recovery rate / oil change efficiency. However, for multiple cores under the same lithology, it is necessary to determine the core with better energy storage fracturing effect.

[0176] Therefore, it is necessary to comprehensively evaluate the various energy storage fracturing conditions by combining the fracture state and the recovery rate / oil change efficiency. Specifically, comprehensively evaluating the fracture state and the recovery rate to determine the energy storage fracturing effects of multiple cores further includes:

[0177] The fracture state and the fracture state weight, the recovery rate and the recovery rate weight are weighted and summed to obtain the energy storage fracturing effect scores of the multiple cores.

[0178] As explained above, the fracture state may include the fracture distribution and / or the fracture volume. If the fracture state is characterized by the fracture volume, the fracture volume needs to be calculated. If the fracture state is characterized by the fracture distribution, the fracture distribution can be quantified by the theory of fractal dimension.

[0179] The fracture state weight and the recovery rate weight can be set according to the actual working conditions. Considering that the recovery rate is more representative of the energy storage fracturing effect than the fracture state, the recovery rate weight can be set greater than the fracture state weight. After weighted summation, the energy storage fracturing effect scores of multiple cores can be obtained.

[0180] Of course, the recovery factor in the above can be adaptively replaced by the oil change efficiency, and the fracture state and the fracture state weight, the oil change efficiency and the oil change efficiency weight are weighted and summed to obtain the energy storage fracturing effect scores of multiple cores.

[0181] Accordingly, selecting the preferred cores from the multiple cores according to the energy storage fracturing effects of the multiple cores further includes:

[0182] The multiple cores are sorted according to the energy storage fracturing effect scores, and the preferred cores are screened out according to the sorting.

[0183] It should be noted that the preferred core referred to in this article is the core with better energy storage fracturing effect, rather than the core with better other physical or chemical characteristics.

[0184] The sorting can be in ascending or descending order, and the cores ranked later in ascending order or earlier in descending order are selected as preferred cores. Of course, the preferred cores can be one or more. The energy storage fracturing conditions corresponding to the preferred cores are the preferred energy storage fracturing conditions corresponding to the current lithology, and the soaking time corresponding to the preferred cores is the preferred soaking time corresponding to the current lithology. According to the preferred energy storage fracturing conditions, the energy storage fracturing fluid, energy storage method and its corresponding displacement and soaking time suitable for the lithology reservoir can be obtained, that is, the energy storage fracturing mode suitable for the lithology reservoir.

[0185] Through the method of this article, the energy storage fracturing effects of multiple cores can be determined by the fracture states and recovery rates of multiple fractured cores after fracturing multiple cores respectively under a variety of energy storage fracturing conditions. Further, preferred cores can be screened out according to the energy storage fracturing effects of the multiple cores, and the energy storage fracturing conditions and soaking time corresponding to the preferred cores can be determined as the energy storage fracturing conditions and soaking time suitable for the lithology, that is, the energy storage fracturing mode suitable for the lithology can be obtained.

[0186] Based on the above-mentioned experimental method for determining the energy storage fracturing mode, the embodiments of this article also provide an experimental device for determining the energy storage fracturing mode. The device may include a system (including a distributed system), software (application), module, component, server, client, etc. using the method described in the embodiments of this article and a device combined with necessary implementation hardware. Based on the same innovative concept, the device in one or more embodiments provided in the embodiments of this article is as described in the following embodiments. Since the implementation scheme and method of the device to solve the problem are similar, the implementation of the specific device in the embodiments of this article can refer to the implementation of the aforementioned method, and the repetitions will not be repeated. As used below, the term "unit" or "module" can implement a combination of software and / or hardware with predetermined functions. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0187] Specifically, Fig. 9 This is a schematic diagram of the module structure of an embodiment of an experimental device for determining an energy storage fracturing mode provided in the embodiments of this article, referring to Fig. 9 As shown, an experimental device for determining an energy storage fracturing mode provided in an embodiment of this invention includes:

[0188] An extraction module 100 is used to extract multiple cores corresponding to the same lithology from a target reservoir;

[0189] A pre-processing module 200, for pre-saturating the plurality of cores with oil;

[0190] A combination module 300 is used to combine energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids to obtain a variety of energy storage fracturing conditions;

[0191] A fracturing module 400 is used to perform fracturing on a plurality of cores treated with pre-saturated oil using a plurality of energy storage fracturing conditions to obtain the fracture states of the plurality of fracturing cores;

[0192] Well soaking module 500, used for soaking multiple fractured cores by pressure imbibition and spontaneous imbibition;

[0193] The recovery factor and well shut-in time determination module 600 is used to obtain the recovery factors and well shut-in times corresponding to a plurality of fracturing cores after the well shut-in is completed;

[0194] The energy storage effect determination module 700 is used to determine the energy storage fracturing effect of multiple cores by combining the fracture state and the recovery rate;

[0195] A screening module 800 is used to screen out preferred cores from a plurality of cores according to the energy storage fracturing effects of the plurality of cores;

[0196] The determination module 900 is used to determine the energy storage fracturing conditions and well soaking time corresponding to the preferred core as energy storage fracturing conditions and well soaking time suitable for the lithology.

[0197] Reference Fig.10 As shown, based on the experimental method for determining the energy storage fracturing mode described above, a computer device 1002 is also provided in one embodiment of the present invention, wherein the above method is run on the computer device 1002. The computer device 1002 may include one or more processors 1004, such as one or more central processing units (CPUs) or graphics processing units (GPUs), and each processing unit may implement one or more hardware threads. The computer device 1002 may also include any memory 1006, which is used to store any kind of information such as code, settings, data, etc. In a specific embodiment, the computer program on the memory 1006 and can be run on the processor 1004, when the computer program is run by the processor 1004, the instructions according to the above method can be executed. Non-limitingly, for example, the memory 1006 may include any one or more combinations of the following: any type of RAM, any type of ROM, flash memory device, hard disk, optical disk, etc. More generally, any memory can use any technology to store information. Further, any memory can provide volatile or non-volatile retention of information. Further, any memory can represent a fixed or removable component of the computer device 1002. In one embodiment, when the processor 1004 executes the associated instructions stored in any memory or combination of memories, the computer device 1002 can perform any operation of the associated instructions. The computer device 1002 also includes one or more drive mechanisms 1008 for interacting with any memory, such as a hard disk drive mechanism, an optical disk drive mechanism, etc.

[0198] The computer device 1002 may also include an input / output module 1010 (I / O) for receiving various inputs (via input device 1012) and for providing various outputs (via output device 1014). A specific output mechanism may include a presentation device 1016 and an associated graphical user interface 1018 (GUI). In other embodiments, the input / output module 1010 (I / O), input device 1012, and output device 1014 may not be included, and the computer device 1002 may be used as a computer device in a network. The computer device 1002 may also include one or more network interfaces 1020 for exchanging data with other devices via one or more communication links 1022. One or more communication buses 1024 couple the components described above together.

[0199] The communication link 1022 may be implemented in any manner, for example, through a local area network, a wide area network (e.g., the Internet), a point-to-point connection, etc., or any combination thereof. The communication link 1022 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc. governed by any protocol or combination of protocols.

[0200] Corresponds to Figure 1-Figure 3 as well as Figure 6-Figure 8 The method in this article also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are executed.

[0201] The embodiment of the present invention also provides a computer readable instruction, wherein when the processor executes the instruction, the program therein causes the processor to execute the following Figure 1-Figure 3 as well as Figure 6-Figure 8 The method shown.

[0202] It should be understood that in the various embodiments of this document, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this document.

[0203] It should also be understood that in the embodiments of this article, the term "and / or" is only a description of the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0204] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this article.

[0205] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0206] In the several embodiments provided herein, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or can be electrical, mechanical or other forms of connection.

[0207] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this article.

[0208] In addition, each functional unit in each embodiment of this invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional unit.

[0209] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this article is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of this article. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0210] Specific embodiments are used in this article to illustrate the principles and implementation methods of this article. The description of the above embodiments is only used to help understand the methods and core ideas of this article. At the same time, for general technicians in this field, according to the ideas of this article, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on this article.

Claims

1. An experimental method for determining energy storage fracturing mode, characterized in that: include: Extract multiple cores corresponding to the same lithology from the target reservoir; pre-saturating the plurality of cores with oil; Combining energy storage fracturing methods with different displacements and different types of energy storage fracturing fluids to obtain a variety of energy storage fracturing conditions, wherein the energy storage fracturing methods with different displacements include: an energy storage fracturing method of fracturing with a set displacement after energy storage with a small displacement and an energy storage fracturing method of directly fracturing with a large displacement, wherein the small displacement is smaller than the set displacement and the large displacement is larger than the set displacement; Using a variety of energy storage fracturing conditions, multiple cores treated with pre-saturated oil are fractured to obtain the fracture states of multiple fracturing cores; Well soaking was performed on multiple fractured cores through pressure imbibition and spontaneous imbibition; When the well soaking is completed, the recovery factors and soaking times corresponding to multiple fracturing cores are obtained; Determine the energy storage fracturing effect of multiple cores based on the fracture state and the recovery rate; According to the energy storage fracturing effects of multiple cores, the preferred cores are selected from the multiple cores; Determine the energy storage fracturing conditions and well soaking time corresponding to the preferred core as energy storage fracturing conditions and well soaking time suitable for the lithology; The step of comprehensively considering the fracture state and the recovery rate to determine the energy storage fracturing effects of multiple cores further includes: Performing weighted summation on the fracture state and the fracture state weight, and the recovery rate and the recovery rate weight to obtain energy storage fracturing effect scores of multiple cores; Accordingly, selecting the preferred cores from the multiple cores according to the energy storage fracturing effects of the multiple cores further includes: The multiple cores are sorted according to the energy storage fracturing effect scores, and the preferred cores are screened out according to the sorting.

2. The experimental method for determining the energy storage fracturing mode according to claim 1, characterized in that: Before the pre-saturated oil treatment is performed on the plurality of cores, the method further comprises: Processing multiple cores into cylindrical shapes of equal size, and drilling non-penetrating wellbores with pre-installed wellbores at the centers of end faces of one end of the multiple cylindrical cores; wherein the diameters of the multiple cylindrical cores are all smaller than the set diameter; The core is washed for oil and impurities and then dried.

3. The experimental method for determining the energy storage fracturing mode according to claim 2, characterized in that: After the pre-saturated oil treatment is performed on the plurality of cores, the method further comprises: A sealant or a rubber tube with pressure bearing capacity is used to respectively wrap and seal a plurality of cores treated with pre-saturated oil except for the wellbore section; The open hole section is reserved, and the non-metallic wellbore is prepared with pressure-bearing materials for cementing.

4. The experimental method for determining the energy storage fracturing mode according to claim 1, characterized in that: The soaking of the multiple fractured cores by pressure imbibition and spontaneous imbibition further comprises: A plurality of fractured cores are subjected to nuclear magnetic resonance scanning while being soaked by pressure imbibition and spontaneous imbibition to obtain nuclear magnetic resonance scanning curves during pressure imbibition and spontaneous imbibition; wherein the nuclear magnetic resonance scanning curves are used to characterize the relationship between the change of nuclear magnetic resonance signals and relaxation time; According to the nuclear magnetic resonance scanning curve, a curve of nuclear magnetic resonance recovery rate changing with time is obtained.

5. The experimental method for determining the energy storage fracturing mode according to claim 4, characterized in that: The obtaining of a curve of change of nuclear magnetic recovery rate over time according to the nuclear magnetic scanning curve further comprises: The nuclear magnetic recovery rate corresponding to any time can be calculated by the following formula: Among them, η' is the nuclear magnetic recovery factor, A2 is the integral of the nuclear magnetic signal intensity over the relaxation time at any time, and A1 is the integral of the nuclear magnetic signal intensity over the relaxation time when the well is started to be soaked.

6. The experimental method for determining the energy storage fracturing mode according to claim 5, characterized in that: When the well soaking is completed, obtaining the recovery factors and well soaking times corresponding to the multiple fracturing cores further includes: The time from the start time of soaking to the end time of soaking is determined as the soaking time corresponding to the fracturing core; The nuclear magnetic recovery rate corresponding to the end of the well soaking in the curve of the change of nuclear magnetic recovery rate over time is determined as the recovery rate corresponding to the fracturing core.

7. The experimental method for determining the energy storage fracturing mode according to claim 1, characterized in that: When the well soaking is completed, obtaining the recovery factors and well soaking times corresponding to the multiple fracturing cores further includes: The time from the start time of soaking to the end time of soaking is determined as the soaking time corresponding to the fracturing core; The fractured cores after soaking were weighed and the corresponding recovery factor of the fractured cores was calculated.

8. The experimental method for determining the energy storage fracturing mode according to claim 7, characterized in that: The weighing of the fractured core after the soaking is completed and the calculation of the recovery factor corresponding to the fractured core further include: The recovery rate corresponding to the fractured core is calculated by the following formula: Where η is the recovery factor, m1 is the mass of the core before pre-saturated oil treatment, m2 is the mass of the fracturing core before the start of soaking, m3 is the mass of the fracturing core after the end of soaking, v is the volume of the energy storage fracturing fluid injected before the start of soaking, ρ is the density of the energy storage fracturing fluid, and f w It is the water content of the fluid discharged after the well is soaked.

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