CN115012906A - Experimental method for determining energy storage fracturing mode - Google Patents
Experimental method for determining energy storage fracturing mode Download PDFInfo
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
An experimental method of determining a stored energy fracturing pattern is provided herein, comprising: extracting a plurality of cores with the same lithology from a target reservoir; carrying out pre-saturated oil treatment on the plurality of rock cores; combining energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types to obtain multiple energy storage fracturing conditions; respectively fracturing the rock cores treated by the multiple pre-saturated oils by utilizing multiple energy storage fracturing conditions to obtain fracture states of the multiple fractured rock cores; soaking the plurality of fractured rock cores in a well by pressured imbibition and spontaneous imbibition; obtaining the recovery rate and the soaking time corresponding to the plurality of fractured cores after the soaking is finished; integrating the fracture state and the recovery rate, and determining the energy storage fracturing effect of the plurality of rock cores; screening out an optimal core from the cores according to the energy storage fracturing effect of the cores; and determining the energy storage fracturing condition and the soaking time corresponding to the optimized rock core as the energy storage fracturing condition and the soaking time suitable for the lithology, and selecting the energy storage fracturing condition and the soaking time suitable for the lithology.
Description
Technical Field
The invention relates to the field of oil and gas development, in particular to an experimental method for determining an energy storage fracturing mode.
Background
The crossing of oil and gas exploration and development from the conventional field in the early stage to the unconventional oil and gas field in the later stage is a necessary trend of the development of the petroleum industry. The primary means of tight oil development is depletion recovery using formation energy, with low and rapid single well production. At present, the supplement of stratum energy is the key for improving the yield and the recovery ratio of a compact reservoir, volume fracturing not only has a seam making function, but also can effectively supplement the stratum energy through soaking after fracturing fluid enters the stratum, after the soaking is finished, oil reservoirs are subjected to pressure reduction exploitation, and high-energy fracturing fluid drives oil gas to be produced, so that the effects of energy storage and yield increase are achieved.
At present, in the prior art, the influence of energy storage fracturing on fracture expansion or the influence of energy storage fracturing on recovery ratio is mostly researched through indoor experiments on energy storage fracturing, and the whole quantitative evaluation on the energy storage fracturing effect is lacked, so that energy storage fracturing fluid and energy storage modes suitable for different lithologic reservoirs and corresponding discharge capacity and soaking time of the energy storage fracturing fluid and the energy storage modes cannot be selected preferably. Therefore, an experimental method for determining an energy storage fracturing mode is urgently needed, and the energy storage fracturing effect can be accurately analyzed through an energy storage fracturing experiment, so that energy storage fracturing fluid and an energy storage mode suitable for a lithologic reservoir stratum, and corresponding discharge capacity and soaking time of the energy storage fracturing fluid and the energy storage mode are selected.
Disclosure of Invention
The embodiment of the invention aims to provide an experimental method for determining an energy storage fracturing mode, so that an energy storage fracturing effect is accurately analyzed, and then energy storage fracturing fluid and an energy storage mode suitable for a lithologic reservoir stratum and corresponding discharge capacity and soaking time of the energy storage fracturing fluid and the energy storage mode are selected.
To achieve the above object, in one aspect, an experimental method for determining an energy-storing fracturing mode is provided in the embodiments herein, including:
extracting a plurality of rock cores corresponding to the same lithology from a target reservoir;
carrying out pre-saturated oil treatment on the plurality of rock cores;
combining energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types to obtain multiple energy storage fracturing conditions;
respectively fracturing the rock cores treated by the plurality of pre-saturated oils by utilizing various energy storage fracturing conditions to obtain fracture states of the plurality of fractured rock cores;
carrying out soaking on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition;
obtaining the recovery rate and the soaking time corresponding to the plurality of fractured cores after the soaking is finished;
integrating the fracture state and the recovery rate, and determining the energy storage fracturing effect of the plurality of rock cores;
screening out an optimal core from the plurality of cores according to the energy storage fracturing effect of the plurality of cores;
and determining the energy storage fracturing condition and the stewing time corresponding to the optimized core as the energy storage fracturing condition and the stewing time suitable for the lithology.
Preferably, before the pre-saturated oil treatment of the plurality of cores, the method further comprises:
processing the plurality of cores into cylinders with equal size, and drilling a non-penetrating borehole with a pre-installed shaft in the center of one end face of each of the plurality of cylinders; the diameters of the plurality of cylindrical rock cores are smaller than a set diameter;
and washing oil and removing impurities from the rock core, and drying.
Preferably, after the pre-saturated oil treatment of the plurality of cores, the method further comprises:
respectively wrapping and sealing the plurality of pre-saturated oil treated cores except the wellbore section by using a sealant or a rubber cylinder with pressure bearing capacity;
and reserving an open hole section, and preparing a non-metal shaft by adopting a pressure-bearing material to perform well cementation.
Preferably, the different-displacement energy-storage fracturing modes comprise:
and setting an energy storage fracturing mode of displacement fracturing and an energy storage fracturing mode of large-displacement direct fracturing after small-displacement energy storage, wherein the small displacement is smaller than the set displacement, and the large displacement is larger than the set displacement.
Preferably, the stewing the plurality of fractured cores through the pressured imbibition and the spontaneous imbibition further comprises:
carrying out nuclear magnetic scanning while carrying out stewing on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition to obtain a nuclear magnetic scanning curve in the under-pressure imbibition and spontaneous imbibition processes; the nuclear magnetic scanning curve is used for representing the change relation of nuclear magnetic signals along with relaxation time;
and obtaining a change curve of the nuclear magnetic recovery rate along with time according to the nuclear magnetic scanning curve.
Preferably, obtaining a nuclear magnetic recovery curve over time according to the nuclear magnetic scan curve further comprises:
calculating the nuclear magnetic recovery factor corresponding to any time by the following formula:
wherein eta' is the nuclear magnetic recovery ratio, A 2 Integral of nuclear magnetic signal intensity over relaxation time at any time, A 1 The integral of the nuclear magnetic signal over the relaxation time at the start of the soak.
Preferably, obtaining the recovery factor and the soak time corresponding to the plurality of fractured cores after the completion of the soaking further comprises:
determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
and determining the nuclear magnetic recovery rate corresponding to the shut-in ending time in the variation curve of the nuclear magnetic recovery rate along with the time as the recovery rate corresponding to the fracturing core.
Preferably, obtaining the recovery factor and the soak time corresponding to the plurality of fractured cores after the completion of the soaking further comprises:
determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
and weighing the fractured core after the soaking is finished, and calculating to obtain the corresponding recovery ratio of the fractured core.
Preferably, the step of weighing the fractured core after the soaking is finished, and the step of calculating the recovery ratio corresponding to the fractured core further comprises:
and calculating the corresponding recovery ratio of the fractured core by the following formula:
where eta is recovery factor, m 1 Mass of core before pre-saturated oil treatment, m 2 Mass m of the fractured core before the start of the soaking 3 The mass of the fractured rock core after the completion of the soaking, v is the volume of the injected energy storage fracturing fluid before the start of the soaking, rho is the density of the energy storage fracturing fluid, f w The water content of the discharged fluid after the well stewing is finished.
Preferably, the integrating the fracture status and the recovery factor and determining the energy storage fracturing effect of the plurality of cores further comprises:
weighting and summing the fracture state and the fracture state weight, and the recovery ratio weight to obtain energy storage fracturing effect scores of a plurality of cores;
correspondingly, according to the energy storage fracturing effect of the plurality of rock cores, the screening of the preferable rock core from the plurality of rock cores further comprises:
and sequencing the plurality of rock cores according to the energy storage fracturing effect score, and screening out the optimal rock core according to the sequencing.
According to the technical scheme provided by the embodiment, through the method, after the multiple cores are fractured under multiple energy storage fracturing conditions, the fracture states and recovery rates of the multiple fractured cores determine the energy storage fracturing effects of the multiple cores, further, the preferred cores are screened according to the energy storage fracturing effects of the multiple cores, and the energy storage fracturing conditions and the annealing time corresponding to the preferred cores are determined to be the energy storage fracturing conditions and the annealing time suitable for the lithology.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 illustrates a schematic flow chart of an experimental method for determining a stored energy fracturing pattern provided by embodiments herein;
fig. 2 illustrates a schematic flow diagram before pre-saturating oil treatment of a plurality of cores as provided in embodiments herein;
fig. 3 illustrates a schematic flow diagram after pre-saturating oil treatment of a plurality of cores as provided in embodiments herein;
FIG. 4 illustrates a morphological schematic diagram of a post-cemented core provided by embodiments herein;
fig. 5 illustrates a cross-sectional view of a molded fractured core provided in embodiments herein in a core holder with coils;
fig. 6 shows a schematic flow diagram for smoldering multiple fractured cores with pressured imbibition and spontaneous imbibition provided in embodiments herein;
fig. 7 is a schematic flow chart illustrating recovery and soak time for multiple fractured cores after completion of the soak as provided in the embodiments herein;
fig. 8 is another schematic flow chart illustrating recovery and soak time for multiple fractured cores after completion of the soak as provided in the examples herein;
fig. 9 is a schematic block diagram illustrating an experimental apparatus for determining an energy storage fracturing mode according to an embodiment of the present disclosure;
fig. 10 shows a schematic structural diagram of a computer device provided in an embodiment herein.
Description of the symbols of the drawings:
1. a core;
2. a non-metallic wellbore;
3. a naked eye section;
4. a glass fiber core holder;
5. a coil;
6. fracturing the rock core;
7. a plug;
100. an extraction module;
200. a preprocessing module;
300. combining the modules;
400. a fracturing module;
500. a soaking module;
600. a recovery ratio and soaking time determining module;
700. an energy storage effect determination module;
800. a screening module;
900. a determination module;
1002. a computer device;
1004. a processor;
1006. a memory;
1008. a drive mechanism;
1010. an input/output module;
1012. an input device;
1014. an output device;
1016. a presentation device;
1018. a graphical user interface;
1020. a network interface;
1022. a communication link;
1024. a communication bus.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments herein without making any creative effort, shall fall within the scope of protection.
The crossing of oil and gas exploration and development from the conventional field of the early stage to the unconventional oil and gas field of the later stage is a necessary trend in the development of the petroleum industry. The primary means of tight oil development is depletion recovery using formation energy, with low and rapid single well production. At present, the supplement of stratum energy is the key for improving the yield and the recovery ratio of a compact reservoir, volume fracturing not only has a seam making function, fracturing fluid enters the stratum and can effectively supplement the stratum energy through soaking, after the soaking is finished, oil reservoirs are subjected to pressure reduction exploitation, high-energy fracturing fluid drives oil gas to be produced, and the effects of energy storage and yield increase are achieved.
At present, in the prior art, the influence of energy storage fracturing on fracture expansion or the influence of energy storage fracturing on recovery ratio is mostly researched through indoor experiments on energy storage fracturing, and the whole quantitative evaluation on the energy storage fracturing effect is lacked, so that energy storage fracturing fluid and energy storage modes suitable for different lithologic reservoirs and corresponding discharge capacity and soaking time of the energy storage fracturing fluid and the energy storage modes cannot be selected preferably.
To address the above issues, embodiments herein provide an experimental method for determining an energy-storing fracturing pattern. Fig. 1 is a schematic flow diagram of an experimental method for determining a stored energy fracturing pattern provided in the examples herein, and the present description provides the method operation steps as described in the examples or the flow diagrams, but may include more or less operation steps based on routine or non-inventive labor. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. When an actual system or apparatus product executes, it can execute sequentially or in parallel according to the method shown in the embodiment or the figures.
It should be noted that the terms "first," "second," and the like in the description and claims herein and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments herein described are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or device.
Referring to fig. 1, an experimental method of determining a stored energy fracturing pattern includes:
s101: extracting a plurality of rock cores corresponding to the same lithology from a target reservoir;
s102: carrying out pre-saturated oil treatment on the plurality of rock cores;
s103: combining energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types to obtain multiple energy storage fracturing conditions;
s104: respectively fracturing the rock cores treated by the pre-saturated oil by utilizing various energy storage fracturing conditions to obtain fracture states of the plurality of fractured rock cores;
s105: carrying out stewing on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition;
s106: obtaining the recovery rate and the soaking time corresponding to the plurality of fractured cores after the soaking is finished;
s107: integrating the fracture state and the recovery rate, and determining the energy storage fracturing effect of the plurality of rock cores;
s108: screening out an optimal core from the cores according to the energy storage fracturing effect of the cores;
s109: and determining the energy storage fracturing condition and the stewing time corresponding to the optimized core as the energy storage fracturing condition and the stewing time suitable for the lithology.
The target reservoir can be any one of sandstone reservoirs, shale reservoirs and the like, for any one of the reservoirs, the lithological properties of the extracted cores are the same, and the best physical properties of the cores are similar except that the lithological properties of the cores are the same. In order to accurately determine the energy storage fracturing mode, the core fracturing conditions under various energy storage fracturing conditions need to be tested subsequently, and therefore multiple cores need to be extracted for testing.
In the experiment, a plurality of cores need to be subjected to pre-saturated oil treatment through S102, and for any one core, the pre-saturated oil treatment may specifically include:
step 1.1: vacuumizing the rock core to saturate water;
step 1.2: the rock core is made into bound water through a high-speed centrifuge and weighed to obtain a first weight;
step 1.3: saturating the core with oil through a vacuum pressurization saturation device or a displacement device, and weighing to obtain a second weight;
step 1.4: calculating to obtain the volume of the saturated oil according to the first weight and the second weight;
step 1.5: and if the volume of the saturated oil is equal to the effective pore volume of the core, obtaining the core after pre-saturated oil treatment.
Wherein, the weight of the saturated oil is the second weight to the first weight, and the volume of the saturated oil is the weight of the saturated oil/the oil density.
After the core after the pre-saturated oil treatment is obtained, the core after the pre-saturated oil treatment can be placed into a nuclear magnetic scanning device for scanning to obtain an initial nuclear magnetic curve, and the inner pore size distribution of the core is determined according to the peak position and the size of the initial nuclear magnetic curve, so that the method can be used for comparing the imbibition effect and the soaking time.
Because the plurality of cores in the experiment are subjected to the comparative experiment, in order to ensure the accuracy and the persuasiveness of the comparative experiment, referring to fig. 2, before the pre-saturated oil treatment is performed on the plurality of cores, the method further includes:
s201: processing the plurality of cores into cylinders with equal size, and drilling a non-penetrating borehole with a pre-installed shaft in the center of one end face of each of the plurality of cylinders; the diameters of the plurality of cylindrical rock cores are smaller than a set diameter;
s202: and washing oil and removing impurities from the rock core, and drying.
To meet the environmental requirements of the laboratory, the set diameter can be chosen to be less than 25 cm.
And when S202 is executed, the core needs to be repeatedly placed into a vacuum drying oven in the drying process, the core is taken out every 24 hours after being placed into the vacuum drying oven, the core is weighed once after being taken out, the core mass at the moment is obtained, the steps are repeatedly executed until the core mass obtained by continuously weighing for multiple times is not reduced, and the core is in a drying completion state at the moment.
Referring to fig. 3, in order to fully simulate the state of fracturing through a wellbore in an actual formation under laboratory conditions, the pre-saturating oil treatment of the plurality of cores further comprises:
s301: respectively wrapping and sealing the plurality of pre-saturated oil treated cores except the wellbore section by using a sealant or a rubber cylinder with pressure bearing capacity;
s302: and reserving an open hole section, and preparing a non-metal shaft by adopting a pressure-bearing material to perform well cementation.
The form of the well-cemented rock core 1 is shown in fig. 4, a non-penetrating borehole is arranged in the center of one end face of the cylindrical rock core 1 in fig. 4, a non-metal borehole 2 is fixed in a borehole section, and the non-metal borehole 2 does not completely cement the borehole section but leaves an open hole section 3. Before well cementation is carried out, the rock core 1 is completely sealed with sealant or provided with a rubber cylinder except a well bore section, and the purpose is to prevent crude oil in the rock core from volatilizing after pre-saturated oil, so that the rock core is wrapped first and then well cementation is carried out. The sealant can be an organosilicon sealant, certainly can also be other suitable sealants, the pressure-bearing material can be a PEEK material, certainly can also be other suitable materials, the sealant is not limited in the text, the well can be fixed by gluing during well fixing, and the well can also be fixed by any other modes which can be realized by a person skilled in the art, and the description is omitted.
In S103, energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types can be combined to obtain multiple energy storage fracturing conditions, multiple rock cores are fractured respectively through the multiple energy storage fracturing conditions, and the fracturing effects of the multiple energy storage fracturing conditions are reflected according to the performance after the multiple rock cores are fractured.
The energy storage fracturing modes with different displacements comprise:
and setting an energy storage fracturing mode of displacement fracturing and an energy storage fracturing mode of large-displacement direct fracturing after small-displacement energy storage, wherein the small displacement is smaller than the set displacement, and the large displacement is larger than the set displacement.
It should be noted that the set discharge volume is set differently according to different lithologies, and the set discharge volume is the discharge volume when conventional fracturing is performed on the corresponding lithologies under laboratory conditions, for example, shale and sandstone are two different lithologies, and therefore, the set discharge volumes of shale and sandstone are different.
The energy storage fracturing mode for setting the displacement fracturing after the small displacement energy storage is as follows: the energy storage liquid is injected into the rock core at a small displacement for energy storage, the fracturing liquid is injected into the rock core at a set displacement after the pore pressure of the rock core reaches an expected value, obvious cracks cannot be generated in the rock core during the energy storage at the small displacement, and the fracturing liquid is injected into the rock core at the set displacement to enable the rock core to generate cracks. The energy storage fracturing mode of the large-displacement direct fracturing specifically comprises the following steps: and directly injecting energy storage fracturing fluid into the rock core in a large displacement manner, wherein the rock core is cracked by injecting the energy storage fracturing fluid in the large displacement manner.
Further, the two energy storage fracturing modes can correspond to multiple displacements, for example, the energy storage fracturing mode for setting displacement fracturing after small displacement energy storage can include: setting displacement fracturing after A displacement energy storage, and setting displacement fracturing … … after B displacement energy storage, wherein A and B belong to small displacement; the energy storage fracturing mode of the large-discharge direct fracturing can comprise the following steps: m displacement direct fracturing, N displacement direct fracturing … … where M and N are both large displacements.
Further, the stored energy fluid, the fracturing fluid, and the stored energy fracturing fluid may each comprise a plurality of fluids or gases, such as produced water, carbon dioxide, and the like.
When the energy storage fracturing modes with different discharge capacities and the energy storage fracturing fluids of different types are combined, various combinations can be generated, and various energy storage fracturing conditions are obtained, for example, the energy storage fracturing conditions are as follows: setting displacement fracturing after storing energy by A displacement of produced water, setting displacement fracturing after storing energy by A displacement of carbon dioxide, and setting displacement fracturing … … after storing energy by B displacement of produced water
For the fracturing process shown in S104, the fracturing process of any one of the cores may specifically include:
step 2.1: arranging an acoustic emission monitoring probe on the rock core;
step 2.2: arranging the rock core provided with the acoustic emission monitoring probe in a pseudo-triaxial fracturing device;
step 2.3: heating the pseudo-triaxial fracturing device to a simulated formation temperature by using a temperature control system;
step 2.4: pressurizing the pseudo-triaxial fracturing device by using a hydraulic pump until the pseudo-triaxial fracturing device simulates three-dimensional ground stress;
step 2.5: supplementing pressure to the pores of the rock core to the pore pressure under the formation condition by using a pore pressure loading system;
step 2.6: closing the pore pressure loading system after the pressure in the pore of the rock core is stable;
step 2.7: performing energy storage fracturing on the rock core by using an energy storage fracturing condition, monitoring the pressure in the fracturing process until the pressure drops suddenly or an acoustic emission monitoring probe monitors a high-intensity signal, determining fracture initiation extension, and stopping fracturing;
step 2.8: after the pump is stopped, the triaxial fracturing device is decompressed, and the fractured rock core is taken out;
step 2.9: and determining the fracture state of the fractured core through CT scanning.
In order to simulate the actual working condition in a laboratory as much as possible, the simulated formation temperature and the simulated three-way ground stress are set according to the formation temperature and the three-way ground stress under the actual working condition, the simulated formation temperature may be different from the actual formation temperature, and the simulated three-way ground stress may be different from the actual three-way ground stress. The fracture state may include the fracture distribution and/or fracture volume, and the fracture distribution is the fracture display and distribution, for example, the fracture is a main trunk fracture, or the fracture is a plurality of branched tree-shaped fractures.
Before the annealing of the plurality of fractured cores through the imbibition under pressure and the spontaneous imbibition in S105, the method may further include:
step 3.1: preparing a glass fiber core holder with a preset diameter by using glass fibers, and preparing a coil matched with the glass fiber core holder;
step 3.2: placing the fractured core into a core holder with a coil after plastic packaging;
step 3.3: the front end of the glass fiber core holder is connected with an injection pipeline, and the rear end of the glass fiber core holder is connected with an oil outlet pipeline;
step 3.4: heating the glass fiber core holder to the simulated formation temperature and applying back pressure;
step 3.5: starting an injection pipeline, and injecting energy storage fracturing fluid into the fracturing core by adopting the pressure when the pump is stopped in the fracturing process;
step 3.6: and closing the injection pipeline and the oil outlet pipeline after the pressure in the cracks of the fractured rock core reaches the preset pressure and is stable.
The time at which the injection line is shut off in step 3.6 is the shut-in start time.
The cross-sectional view that the fracturing rock core after the plastic envelope is located in the rock core of having the coil adds the holder is shown in fig. 5, when carrying out fracturing rock core installation specifically and placing, can carry out the plastic envelope with fracturing rock core 6 earlier, put into glass fiber rock core holder 4 with the fracturing rock core 6 that the plastic envelope is good, end cap 7 is inserted at glass fiber rock core holder 4 both ends, then establish supporting coil 5 with the outside cover of glass fiber rock core holder 4, wherein all seted up the passageway on the end cap 7 at both ends, two passageways are used for connecting injection line and oil line respectively.
Referring to fig. 6, in an embodiment herein, the smoldering the plurality of fractured cores with the pressured imbibition and the spontaneous imbibition further comprises:
s401: carrying out nuclear magnetic scanning while carrying out stewing on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition to obtain a nuclear magnetic scanning curve in the under-pressure imbibition and spontaneous imbibition processes; wherein the nuclear magnetic scanning curve is used for representing the change relation of nuclear magnetic signals along with relaxation time;
s402: and obtaining a change curve of the nuclear magnetic recovery rate along with time according to the nuclear magnetic scanning curve.
In order to realize the stewing and nuclear magnetic scanning of the fractured rock core through the pressurized imbibition and the spontaneous imbibition, after the fractured rock core is molded and placed into the rock core holder with the coil in the step 3.2, the glass fiber rock core holder with the coil can be placed into a nuclear magnetic scanning device, and the nuclear magnetic scanning is started through the nuclear magnetic scanning device when the injection pipeline is closed in the step 3.6.
During the soaking process, the fracturing fluid is seeped and sucked from the cracks to the matrix under pressure in the fractured rock core, the fractured rock core starts to seep and suck spontaneously after the pressure of the cracks and the matrix is balanced, and the crude oil is replaced by the seepage and suction of the fracturing fluid.
Because the change curve of the nuclear magnetic recovery rate along with time can be obtained according to the nuclear magnetic scanning curve, the time when the nuclear magnetic recovery rate begins not to change along with the increase of time is the soaking ending time, and at the moment, the oil outlet pipeline can be opened to release pressure and discharge oil.
In this embodiment, said deriving a nuclear magnetic recovery curve over time from said nuclear magnetic scan curve further comprises:
calculating the nuclear magnetic recovery factor corresponding to any time by the following formula:
wherein eta' is the nuclear magnetic recovery ratio, A 2 Integral of nuclear magnetic signal intensity over relaxation time at any time, A 1 For starting to soak wellIntegral of the number versus relaxation time.
Referring to fig. 7, further, obtaining recovery factors and a soak time corresponding to the plurality of fractured cores after the completion of the soaking further includes:
s501: determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
s502: and determining the nuclear magnetic recovery rate corresponding to the shut-in ending time in the variation curve of the nuclear magnetic recovery rate along with the time as the recovery rate corresponding to the fracturing core.
As described above, for each core, the time when the injection pipeline is closed is the soaking start time, the time when the nuclear magnetic recovery rate begins to be unchanged along with the increase of time is the soaking end time, and the soaking time can be obtained according to the difference between the soaking start time and the soaking end time.
Besides the method for determining the recovery factor corresponding to the fracture core described in S502, the recovery factor corresponding to the fracture core may also be determined through other steps, specifically:
referring to fig. 8, obtaining recovery and a soak time for a plurality of fractured cores after the completion of the soaking further comprises:
s601: determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
s602: and weighing the fractured core after the soaking is finished, and calculating to obtain the corresponding recovery ratio of the fractured core.
S602 is another method for determining the recovery ratio corresponding to the fractured core, but it should be noted that when the fractured core after the shut-in is weighed, the fractured core may be taken out from the glass fiber core holder and weighed until no more crude oil flows out from the oil line.
In S602, in addition to weighing the fractured core after completion of the soaking, a balance may be connected to the end of the oil production line to directly weigh the crude oil in the discharged fluid after completion of the soaking, so as to obtain the weight of the fractured core. In this embodiment, the weighing the fractured core after the soaking is finished, and calculating the recovery factor corresponding to the fractured core further includes:
and calculating the corresponding recovery ratio of the fractured core by the following formula:
where eta is recovery ratio, m 1 Mass of core before pre-saturated oil treatment, m 2 Mass m of the fractured core before the start of the soaking 3 The mass of the fractured rock core after the completion of the soaking, v is the volume of the injected energy storage fracturing fluid before the start of the soaking, rho is the density of the energy storage fracturing fluid, f w The water content of the discharged fluid after the well stewing is finished.
Furthermore, after the recovery ratio corresponding to the fractured core is obtained, the oil production amount can be further calculated, and the oil change efficiency can be calculated according to the oil production amount, specifically,
the oil recovery amount is equal to the volume of saturated oil multiplied by the recovery ratio corresponding to the fractured core;
wherein, the saturated oil volume refers to the saturated oil volume in the pre-saturated oil treatment process, and the injection amount of the energy storage fracturing fluid refers to the amount of the energy storage fracturing fluid injected in the process of performing energy storage fracturing on the rock core in the step 2.7 or the amount of the energy storage fracturing fluid injected in the step 3.5.
The oil change efficiency is the same as the recovery efficiency, and the energy storage fracturing effect of the fractured rock core can be evaluated.
Therefore, the fracture state, the recovery rate, the oil change efficiency and the soaking time corresponding to the plurality of fractured rock cores can be obtained, each fractured rock core represents one energy storage fracturing condition, the energy storage fracturing effect under the various energy storage fracturing conditions, namely the fracture state and the recovery rate/oil change efficiency, is displayed, and the rock core with the better energy storage fracturing effect needs to be determined corresponding to the plurality of rock cores under one lithology.
Therefore, it is required to evaluate a plurality of energy storage fracturing conditions by integrating the fracture state and the recovery factor/oil change efficiency, and specifically, determining the energy storage fracturing effect of a plurality of cores by integrating the fracture state and the recovery factor further includes:
and carrying out weighted summation on the fracture state and the fracture state weight, and the recovery ratio weight to obtain the energy storage fracturing effect scores of the cores.
Since it has been explained above that the fracture state may include the fracture spread and/or fracture volume, if the fracture state is characterized by fracture volume, the fracture volume needs to be calculated; if the crack state is represented by the crack spread, the crack spread can be quantified by the theory of fractal dimension.
The fracture state weight and the recovery ratio weight can be set according to actual working conditions, and the recovery ratio can represent the energy storage fracturing effect better in comparison with the fracture state, so that the recovery ratio weight can be set to be larger than the fracture state weight, and the energy storage fracturing effect scores of the cores are obtained after weighting summation.
Of course, the recovery ratio in the above may be adaptively replaced by oil change efficiency, and the fracture state weight, and the oil change efficiency weight are weighted and summed to obtain the energy storage fracturing effect score of the plurality of cores.
Correspondingly, according to the energy storage fracturing effect of the plurality of rock cores, the screening of the preferable rock core from the plurality of rock cores further comprises:
and sequencing the plurality of rock cores according to the energy storage fracturing effect score, and screening out the optimal rock core according to the sequencing.
It should be noted that the preferred core referred to herein is a core having a better energy storage fracturing effect, but not a core having a better physical or chemical characteristic.
The sorting can be performed in ascending order or descending order, and cores ranked later in ascending order or earlier in descending order are selected as preferred cores, and of course, the preferred cores can be one or more. The energy storage fracturing conditions corresponding to the optimized rock core are the optimized energy storage fracturing conditions corresponding to the current lithology, the soaking time corresponding to the optimized rock core is the optimized soaking time corresponding to the current lithology, and the energy storage fracturing fluid, the energy storage mode and the corresponding discharge capacity and the soaking time which are suitable for the lithology reservoir can be obtained according to the optimized energy storage fracturing conditions, namely the energy storage fracturing mode which is suitable for the lithology reservoir.
By the method, after the multiple cores are fractured under multiple energy storage fracturing conditions, the fracture states and recovery rates of the multiple fractured cores determine the energy storage fracturing effects of the multiple cores, further, the optimal cores are screened according to the energy storage fracturing effects of the multiple cores, the energy storage fracturing conditions and the annealing time corresponding to the optimal cores are determined to be the energy storage fracturing conditions and the annealing time suitable for the lithology, and the energy storage fracturing mode suitable for the lithology is obtained.
Based on the experimental method for determining the energy storage fracturing mode, the embodiment herein further provides an experimental device for determining the energy storage fracturing mode. The apparatus may include systems (including distributed systems), software (applications), modules, components, servers, clients, etc. that employ the methods described herein in embodiments, in conjunction with any necessary apparatus to implement the hardware. Based on the same innovative concepts, embodiments herein provide an apparatus as described in the following embodiments. Since the implementation scheme of the apparatus for solving the problem is similar to that of the method, the specific apparatus implementation in the embodiment of the present disclosure may refer to the implementation of the foregoing method, and repeated details are not repeated. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated.
Specifically, fig. 9 is a schematic block diagram of an embodiment of an experimental apparatus for determining an energy-storing fracturing mode provided in an embodiment of the present disclosure, and referring to fig. 9, the experimental apparatus for determining an energy-storing fracturing mode provided in an embodiment of the present disclosure includes:
the extraction module 100 is used for extracting a plurality of rock cores corresponding to the same lithology from a target reservoir;
the pretreatment module 200 is used for carrying out pre-saturated oil treatment on the cores;
the combination module 300 is used for combining energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types to obtain multiple energy storage fracturing conditions;
the fracturing module 400 is used for respectively fracturing the cores after the multiple pre-saturated oil treatments by utilizing multiple energy storage fracturing conditions to obtain fracture states of multiple fractured cores;
the stewing module 500 is used for stewing a plurality of fractured rock cores through pressured imbibition and spontaneous imbibition;
the recovery efficiency and soak time determining module 600 is used for obtaining the recovery efficiency and the soak time corresponding to the plurality of fractured cores after the soak is finished;
the energy storage effect determination module 700 is used for integrating the fracture state and the recovery factor and determining the energy storage fracturing effect of the plurality of rock cores;
the screening module 800 is used for screening out an optimal core from the plurality of cores according to the energy storage fracturing effect of the plurality of cores;
and a determining module 900, configured to determine the energy storage fracturing condition and the soaking time corresponding to the preferred core as the energy storage fracturing condition and the soaking time suitable for the lithology.
Referring to fig. 10, based on the experimental method for determining the energy-storing fracturing mode, a computer device 1002 is further provided in an embodiment of the present disclosure, wherein the method is executed on the computer device 1002. Computer device 1002 may include one or more processors 1004, such as one or more Central Processing Units (CPUs) or Graphics Processors (GPUs), each of which may implement one or more hardware threads. The computer device 1002 may also comprise any memory 1006 for storing any kind of information, such as code, settings, data, etc., and in a particular embodiment a computer program on the memory 1006 and executable on the processor 1004, the computer program when executed by the processor 1004 may perform instructions according to the above described method. For example, and without limitation, the memory 1006 may include any one or more of the following in combination: any type of RAM, any type of ROM, flash memory devices, hard disks, optical disks, etc. More generally, any memory may use any technology to store information. Further, any memory may provide volatile or non-volatile retention of information. Further, any memories may represent fixed or removable components of computer device 1002. In one case, when the processor 1004 executes the associated instructions, which are stored in any memory or combination of memories, the computer device 1002 can perform any of the operations of the associated instructions. The computer device 1002 also includes one or more drive mechanisms 1008, such as a hard disk drive mechanism, an optical disk drive mechanism, or the like, for interacting with any memory.
Corresponding to the methods in fig. 1-3 and fig. 6-8, the embodiments herein also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the above-mentioned method.
Embodiments herein also provide computer readable instructions, wherein a program thereof causes a processor to perform the methods as shown in fig. 1-3 and fig. 6-8 when the instructions are executed by the processor.
It should be understood that, in various embodiments herein, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments herein.
It should also be understood that, in the embodiments herein, the term "and/or" is only one kind of association relation describing an associated object, meaning that three kinds of relations may exist. For example, a and/or B, may represent: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
Those of ordinary skill in the art will appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be embodied in electronic hardware, computer software, or combinations of both, and that the components and steps of the examples have been described in a functional general in the foregoing description for the purpose of illustrating clearly the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided herein, it should be understood that the disclosed system, apparatus, and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may also be an electrical, mechanical or other form of connection.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on multiple network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments herein.
In addition, functional units in the embodiments herein may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present invention may be implemented in a form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The principles and embodiments of this document are explained herein using specific examples, which are presented only to aid in understanding the methods and their core concepts; meanwhile, for the general technical personnel in the field, according to the idea of this document, there may be changes in the concrete implementation and the application scope, in summary, this description should not be understood as the limitation of this document.
Claims (10)
1. An experimental method for determining an energy-storing fracturing mode, comprising:
extracting a plurality of rock cores corresponding to the same lithology from a target reservoir;
carrying out pre-saturated oil treatment on the plurality of rock cores;
combining energy storage fracturing modes with different discharge capacities and energy storage fracturing fluids of different types to obtain multiple energy storage fracturing conditions;
respectively fracturing the rock cores treated by the plurality of pre-saturated oils by utilizing various energy storage fracturing conditions to obtain fracture states of the plurality of fractured rock cores;
carrying out stewing on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition;
obtaining the recovery rate and the soaking time corresponding to the plurality of fractured cores after the soaking is finished;
integrating the fracture state and the recovery rate, and determining the energy storage fracturing effect of the plurality of rock cores;
screening out an optimal core from the cores according to the energy storage fracturing effect of the cores;
and determining the energy storage fracturing condition and the stewing time corresponding to the optimized core as the energy storage fracturing condition and the stewing time suitable for the lithology.
2. The experimental method for determining a stored energy fracturing pattern as claimed in claim 1, wherein said pre-saturating oil treatment of said plurality of cores further comprises:
processing the plurality of cores into cylinders with equal size, and drilling a non-penetrating borehole with a pre-installed shaft in the center of one end face of each of the plurality of cylinders; the diameters of the plurality of cylindrical rock cores are smaller than a set diameter;
and washing oil and removing impurities from the rock core, and drying.
3. The experimental method for determining a stored energy fracturing pattern of claim 2, further comprising, after the pre-saturating oil treatment of the plurality of cores:
respectively wrapping and sealing the plurality of pre-saturated oil treated cores except the wellbore section by using a sealant or a rubber cylinder with pressure bearing capacity;
and reserving an open hole section, and preparing a non-metal shaft by adopting a pressure-bearing material to perform well cementation.
4. The experimental method for determining a charged fracturing pattern of claim 1, wherein the charged fracturing modes of different displacement comprise:
and setting an energy storage fracturing mode of displacement fracturing and an energy storage fracturing mode of large-displacement direct fracturing after small-displacement energy storage, wherein the small displacement is smaller than the set displacement, and the large displacement is larger than the set displacement.
5. The experimental method for determining the energy-storing fracturing mode as claimed in claim 1, wherein the smoldering the plurality of fracture cores through the pressure imbibition and the spontaneous imbibition further comprises:
carrying out nuclear magnetic scanning while carrying out stewing on the plurality of fractured rock cores through under-pressure imbibition and spontaneous imbibition to obtain a nuclear magnetic scanning curve in the under-pressure imbibition and spontaneous imbibition processes; the nuclear magnetic scanning curve is used for representing the change relation of nuclear magnetic signals along with relaxation time;
and obtaining a change curve of the nuclear magnetic recovery rate along with time according to the nuclear magnetic scanning curve.
6. The experimental method for determining an energy storing fracturing pattern of claim 5, wherein said deriving a nuclear magnetic recovery factor versus time curve from said nuclear magnetic scan curve further comprises:
calculating the nuclear magnetic recovery factor corresponding to any time by the following formula:
wherein eta' is the nuclear magnetic recovery ratio, A 2 Integral of nuclear magnetic signal intensity over relaxation time at any time, A 1 The integral of the nuclear magnetic signal over the relaxation time at the start of the soak.
7. The experimental method for determining a stored energy fracturing pattern as claimed in claim 6, wherein obtaining recovery factors and a shut-in time corresponding to a plurality of fracture cores after shut-in is finished further comprises:
determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
and determining the nuclear magnetic recovery rate corresponding to the shut-in ending time in the variation curve of the nuclear magnetic recovery rate along with the time as the recovery rate corresponding to the fracturing core.
8. The experimental method for determining a stored energy fracturing pattern as claimed in claim 1, wherein obtaining recovery factors and a shut-in time corresponding to a plurality of fracture cores after shut-in is finished further comprises:
determining the time from the stewing starting time to the stewing ending time as the stewing time corresponding to the fracturing core;
and weighing the fractured core after the soaking is finished, and calculating to obtain the corresponding recovery ratio of the fractured core.
9. The experimental method for determining the energy-storing fracturing mode as claimed in claim 8, wherein the step of weighing the fractured core after completion of the soaking and calculating the corresponding recovery ratio of the fractured core further comprises the steps of:
and calculating the corresponding recovery ratio of the fractured core by the following formula:
where eta is recovery factor, m 1 Mass of core before pre-saturated oil treatment, m 2 Mass m of the fractured core before the start of the soaking 3 The mass of the fractured rock core after the completion of the soaking, v is the volume of the injected energy storage fracturing fluid before the start of the soaking, rho is the density of the energy storage fracturing fluid, f w The water content of the discharged fluid after the well stewing is finished.
10. The experimental method for determining a stored energy fracturing pattern of claim 1, wherein the integrating the fracture status and the recovery factor and determining the stored energy fracturing effect of the plurality of cores further comprises:
weighting and summing the fracture state and the fracture state weight, and the recovery ratio weight to obtain energy storage fracturing effect scores of a plurality of cores;
correspondingly, the screening of the preferable core from the plurality of cores according to the energy storage fracturing effect of the plurality of cores further comprises:
and sequencing the plurality of rock cores according to the energy storage fracturing effect score, and screening out the preferred rock core according to the sequencing.
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