CN111550236B - Simulation experiment method for shale oil and gas reservoir fracture closure coefficient - Google Patents
Simulation experiment method for shale oil and gas reservoir fracture closure coefficient Download PDFInfo
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- 239000003079 shale oil Substances 0.000 title claims abstract description 32
- 238000004088 simulation Methods 0.000 title claims abstract description 21
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
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- 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
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling 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
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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Abstract
The embodiment of the invention provides a simulation experiment method for a shale oil-gas reservoir fracture closure coefficient, which comprises the following steps: placing the two guide plates into a guide chamber, weighing a proppant with preset mass, uniformly and flatly paving the proppant between the two guide plates, and obtaining a corresponding relation between the closing pressure of the proppant and the pore volume change of the proppant through a crack conductivity test experiment; adopting linear function fitting to obtain a fitting straight line for the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitting straight line as the pore compression coefficient of the proppant; and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber. The closure coefficient of the embodiment of the invention can be directly applied to numerical simulation of shale oil and gas reservoirs.
Description
Technical Field
The embodiment of the invention relates to the technical field of exploration and development of oil and gas reservoirs, in particular to a simulation experiment method for a shale oil and gas reservoir fracture closure coefficient.
Background
The shale oil and gas reservoir has the physical characteristics of low porosity and low permeability, and if fracturing transformation is not carried out, a fracture network zone is formed, so that a sufficient flow channel is provided for the shale oil and gas, and industrial yield and recovery ratio cannot be obtained. The shale oil and gas exploitation technology at the present stage mainly comprises a horizontal well multi-section multi-cluster fracturing technology, a slickwater ultra-large size fracturing technology and a synchronous fracturing technology, and the effective transformation technologies can greatly improve the yield of the shale oil and gas well.
The rock oil-gas reservoir is different from the traditional low-permeability oil-gas reservoir, and the traditional compact reservoir forms a single main crack through hydraulic fracturing, so that the length of the main crack and the flow conductivity of the crack are mainly improved, the contact area between the crack and the reservoir is increased, and the yield of an oil-gas well is improved. The matrix fracture of the shale oil and gas reservoir is extremely low, reaches the Nadarcy grade, and basically has no permeability, so that the yield increasing effect of only forming a single main fracture is limited. However, the shale oil and gas reservoir generally develops in bedding, natural fractures develop and cores are large in brittleness, a net-shaped fracture zone can be formed through large-scale hydraulic fracturing, the bedding and the natural fractures are communicated, the contact area of the fractures and a reservoir is effectively increased, oil and gas flow can reach the bottom of a well through a matrix to the fractures, and therefore the yield of the oil and gas reservoir is effectively improved. The reservoir where the shale oil and gas reservoir fracturing network zone is located is called a shale oil and gas reservoir transformation volume, shale oil and gas in the transformation volume can effectively exploit the development degree and brittleness degree of shale gas reservoir bedding and microcracks, and the fracturing scale and fracturing technology jointly determine the size of the fracturing transformation volume and the complexity degree of the fractures, the larger the transformation volume is, the more complex the fractures are, and the better the fracturing yield-increasing effect is. After the fracture is formed under the action of high-pressure fluid, the well is closed for a period of time to wait for the pressure of the stratum to be redistributed, and then the well is opened for blowout. In the blowout stage, as the fluid continuously flows back to the bottom of the well from the fracture, the pressure in the fracture is gradually reduced, the width, the length and the height of the fracture are also reduced along with the reduction of the pressure, and the fracture with certain width, length and height is formed under the propping action of the propping agent.
In the numerical simulation process of the shale oil and gas reservoir fracture, the fracture length, the fracture width and the fracture height are required to be input in the water conservancy fracture design, the conventional fracture compression coefficient is limited to the change of the fracture volume along with the pressure, so that the volume compression coefficient cannot be directly applied to the numerical simulation of the shale oil and gas reservoir fracture, and therefore an experimental method is urgently needed to be designed to determine the fracture closure degree so as to guide the numerical simulation of the shale oil and gas reservoir fracture.
Disclosure of Invention
The embodiment of the invention provides a simulation experiment method for a shale oil and gas reservoir fracture closure coefficient, which can be directly applied to numerical simulation of shale oil and gas reservoir fractures.
The embodiment of the invention provides a simulation experiment method for a shale oil-gas reservoir fracture closure coefficient, which comprises the following steps:
placing the two guide plates into a guide chamber, weighing a proppant with preset mass, uniformly and flatly paving the proppant between the two guide plates, and obtaining a corresponding relation between the closing pressure of the proppant and the pore volume change of the proppant through a crack conductivity test experiment;
adopting linear function fitting to obtain a fitting straight line for the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitting straight line as the pore compression coefficient of the proppant;
and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber.
In one embodiment of the present invention, the first and second electrodes are,
through fracture conductivity test experiment, obtain the closing pressure of proppant and the corresponding relation of proppant pore volume change volume, include:
connecting the flow guide chamber into a pipeline of the crack flow guide capacity testing device, placing a sealed measuring cylinder at the liquid outlet, and placing the measuring cylinder on a balance;
opening a gas tank switch of the crack flow conductivity testing device, so that the liquid finally reaches the measuring cylinder through the pipeline in the flow conductivity chamber;
closing the gas tank when the liquid stably flows into the measuring cylinder, and resetting the balance;
setting a closing pressure increase value, recording closing pressure and the mass of water in a balance measuring cylinder per second, and closing the crack flow conductivity testing device when the closing pressure reaches a preset limit value, wherein the mass of the water is the volume of the water, and the volume of the water represents the pore volume variation of the proppant;
and recording to obtain the corresponding relation between the closing pressure and the pore volume change of the proppant.
In one embodiment of the present invention, the fracture closure coefficient of the proppant is obtained according to the pore compression coefficient, the initial distance between the two baffles, the length of the diversion chamber and the height of the diversion chamber, and the formula is as follows:
wherein,
in the formula, CfThe closure factor of the crack, Mpa-1；
Bf-a pore compressibility;
ΔVw-as proppant pore volume change, cm3Δ p — is the closing pressure variation, MPa;
a, representing the length of the simulated crack, which is the length of the diversion chamber, cm;
b, representing the height of the simulated crack, wherein the height is the width of the diversion chamber in cm;
c, representing the initial simulated crack width, which is the initial distance, cm, between the two guide plates of the guide chamber.
In one embodiment of the present invention, the length of the diversion chamber is 17.7cm, and the width of the diversion chamber is 3.8 cm.
In one embodiment of the invention, the predetermined limit is 70 Mpa.
In one embodiment of the invention, the closing pressure boost value is 5 MPa.
In one embodiment of the present invention, the support is one of:
quartz sand, metal aluminum balls, walnut shells, glass beads, plastic balls, steel balls, ceramsite and resin coated sand.
The simulation experiment method for the fracture closure coefficient of the shale oil and gas reservoir provided by the embodiment of the invention comprises the steps of placing two guide plates into a guide chamber, weighing a proppant with preset mass, uniformly and flatly paving the proppant between the two guide plates, and obtaining the corresponding relation between the closure pressure of the proppant and the pore volume change of the proppant through a fracture conductivity test experiment; adopting linear function fitting to obtain a fitting straight line for the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitting straight line as the pore compression coefficient of the proppant; and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber. The initial simulated fracture width, the simulated fracture length and the simulated fracture height are respectively represented by utilizing the distance between the two guide plates, the length of the guide chamber and the height of the guide chamber, and the obtained closure coefficient can be used for numerical simulation of the shale oil and gas reservoir.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the 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 some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic flow chart of a simulation experiment method for fracture closure coefficients of a shale hydrocarbon reservoir provided by an embodiment of the invention;
FIG. 2 is a schematic pre-experiment view of proppant provided by embodiments of the present invention in a diversion chamber;
FIG. 3 is a post-experimental schematic illustration of proppant provided by embodiments of the present invention in a diversion chamber;
FIG. 4 is a graph of the closing pressure versus proppant pore volume change provided by an embodiment of the present invention;
fig. 5 is a graph fitted with closing pressure versus proppant pore volume change provided by an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings that is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "plurality" or "a plurality" means two or more unless specifically defined otherwise.
At present, the existing shale oil and gas reservoir has physical properties of low porosity and low permeability, and if fracturing transformation is not implemented, a fracture network zone is formed, so that a sufficient flow channel is provided for shale oil and gas, and industrial yield and recovery ratio cannot be obtained. The shale oil and gas exploitation technology at the present stage mainly comprises a horizontal well multi-section multi-cluster fracturing technology, a slickwater ultra-large size fracturing technology and a synchronous fracturing technology, and the effective transformation technologies can greatly improve the yield of the shale oil and gas well. The rock oil-gas reservoir is different from the traditional low-permeability oil-gas reservoir, and the traditional compact reservoir forms a single main crack through hydraulic fracturing, so that the length of the main crack and the flow conductivity of the crack are mainly improved, the contact area between the crack and the reservoir is increased, and the yield of an oil-gas well is improved. The matrix fracture of the shale oil and gas reservoir is extremely low, reaches the Nadarcy grade, and basically has no permeability, so that the yield increasing effect of only forming a single main fracture is limited. However, the shale oil and gas reservoir generally develops in bedding, natural fractures develop and cores are large in brittleness, a net-shaped fracture zone can be formed through large-scale hydraulic fracturing, the bedding and the natural fractures are communicated, the contact area of the fractures and a reservoir is effectively increased, oil and gas flow can reach the bottom of a well through a matrix to the fractures, and therefore the yield of the oil and gas reservoir is effectively improved. The reservoir where the shale oil and gas reservoir fracturing network zone is located is called a shale oil and gas reservoir transformation volume, shale oil and gas in the transformation volume can effectively exploit the development degree and brittleness degree of shale gas reservoir bedding and microcracks, and the fracturing scale and fracturing technology jointly determine the size of the fracturing transformation volume and the complexity degree of the fractures, the larger the transformation volume is, the more complex the fractures are, and the better the fracturing yield-increasing effect is. After the fracture is formed under the action of high-pressure fluid, the well is closed for a period of time to wait for the pressure of the stratum to be redistributed, and then the well is opened for blowout. In the blowout stage, as the fluid continuously flows back to the bottom of the well from the fracture, the pressure in the fracture is gradually reduced, the width, the length and the height of the fracture are also reduced along with the reduction of the pressure, and the fracture with certain width, length and height is formed under the propping action of the propping agent. In numerical simulation software, the fracture length, the fracture width and the fracture height need to be input in water conservancy fracture design, the conventional fracture compression coefficient is limited only in the change of the fracture volume along with the pressure and cannot be directly applied to numerical simulation, and therefore an experimental method is urgently needed to be designed to determine the fracture closure degree so as to guide the numerical simulation.
To show the shrinkage of the fracture volume as a function of formation pressure drop, the concept of fracture closure factor was introduced. In order to be suitable for numerical simulation calculation, the fracture closure degree after pressure reduction is convenient to evaluate. The fracture closure coefficient is a value of a reduction in fracture width per unit reduction in pressure, that is:
the fracture closure coefficient formula is as follows:
in the formula, CfThe closure factor of the crack, Mpa-1
WfWidth of initial crack, m
Δ p-change in fracture pressure, Mpa
ΔpeEffective intra-suture pressure change, Mpa
ΔWp-the reduction of the fracture width, m, when the fracture pressure is reduced.
The embodiment of the invention provides a simulation experiment method for a shale oil and gas reservoir fracture closure coefficient.
Referring to fig. 1, fig. 1 is a schematic flow chart of a simulation experiment method for fracture closure coefficient of a shale hydrocarbon reservoir provided by an embodiment of the present invention, and details steps are as follows:
step 101: placing the two guide plates into a guide chamber, weighing a proppant with preset mass, uniformly and flatly paving the proppant between the two guide plates, and obtaining the corresponding relation between the closing pressure of the proppant and the pore volume change of the proppant through a crack conductivity test experiment.
Specifically, the steps include:
connecting the flow guide chamber into a pipeline of the crack flow guide capacity testing device, placing a sealed measuring cylinder at the liquid outlet, and placing the measuring cylinder on a balance;
opening a gas tank switch of the crack flow conductivity testing device, so that the liquid finally reaches the measuring cylinder through the pipeline in the flow conductivity chamber;
closing the gas tank when the liquid stably flows into the measuring cylinder, and resetting the balance;
setting a closing pressure increase value, recording closing pressure and the mass of water in a balance measuring cylinder per second, and closing the crack flow conductivity testing device when the closing pressure reaches a preset limit value, wherein the mass of the water is the volume of the water, and the volume of the water represents the pore volume variation of the proppant;
and recording to obtain the corresponding relation between the closing pressure and the pore volume change of the proppant.
In this embodiment, the fracture conductivity testing apparatus includes: 1. a linear flow channeling chamber (radial flow channeling chamber) that conforms to the API standard; test area 67.3cm2The upper and lower ends of the propping agent can be provided with rock molds and disassembly tools. 2. The core holder, the circulation holder 3, the hydraulic press and the pressure compensation system; 4. a linear displacement sensor; 5. the test liquid displacement system comprises a displacement pump, a liquid storage container and the like; 6. differential pressure gauge, pressure sensor; 7. a back pressure regulation system; 8. a balance; 9. a heating and temperature control system; 10. a vacuum system; 11. an automatic control system; 12. a data acquisition and processing system. The liquid in the storage tank is pressed into the diversion chamber through the high-pressure nitrogen in the nitrogen bottle, and the liquid flows through the intermediate pipeline and the diversion chamber to reach the measuring cylinder on the balance.
In this embodiment, the length of the diversion chamber is 17.7cm, and the width of the diversion chamber is 3.8 cm. The guide plate of the guide chamber is an iron plate.
In one embodiment of the invention, the predetermined limit is 70 Mpa.
In one embodiment of the invention, the closing pressure boost value is 5 MPa.
Specifically, placing an iron plate into a flow guide chamber for testing the flow guide capacity of the crack, weighing the same mass of propping agent, and uniformly spreading the propping agent between the iron plates. As shown in fig. 2.
The diversion chamber is placed in a crack diversion capability testing device, the diversion chamber is connected into a pipeline, the diversion chamber is placed in a measuring cylinder with good sealing at a liquid outlet, and the measuring cylinder is placed on a balance. And opening a gas tank switch to enable the liquid to flow through the pipeline into the diversion chamber and finally reach the measuring cylinder. And (5) closing the gas tank when the liquid stably flows into the measuring cylinder, and resetting the balance.
Setting the closing pressure increasing value (the closing pressure boosting value can be 5MPA), recording the closing pressure and the balance mass per second, setting the closing pressure to reach 70Mpa, closing the instrument, and distributing the proppant in the diversion room after the experiment is finished as shown in figure 3.
Step 102: and fitting a linear function to obtain a fitted straight line according to the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitted straight line as the pore compression coefficient of the proppant.
In this example, the slope of the fitted line is the ratio of the proppant pore volume change to the closure pressure.
Can be expressed by the following formula:
in the formula,. DELTA.Vw-as proppant pore volume change, cm3Δ p-is the closure pressure, MPa.
Specifically, data of a corresponding relation between the closing pressure and the pore volume change amount of the proppant is derived, a curve of the closing pressure and the volume is obtained through conversion and is shown in fig. 4, a linear slope is obtained by fitting a straight line with a linear function and is shown in fig. 5, and the slope is the pore compression coefficient of the proppant.
Step 103: and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber.
Specifically, the fracture closure coefficient of the proppant is obtained according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber, and the formula is as follows:
wherein,
in the formula, CfThe closure factor of the crack, Mpa-1；
Bf-a pore compressibility;
ΔVw-as volume change of proppant pore cm3Δ p-is the closure pressure MPa;
a, representing the length of the simulated crack, which is the length of the diversion chamber, cm;
b, representing the height of the simulated crack, wherein the height is the width of the diversion chamber in cm;
c, representing the initial simulated crack width, which is the initial distance, cm, between the two guide plates of the guide chamber.
Substituting equation (3) into equation (2) yields the following equation:
in the formula (4), c is equivalent to W in the formula (1)fAnd Δ P is a closing pressure variation amount corresponding to a fracture pressure variation in the formula (1),
corresponding to Δ W in equation (1)p。
It should be noted that the proppant in the embodiment of the present invention may be one of the following:
quartz sand, metal aluminum balls, walnut shells, glass beads, plastic balls, steel balls, ceramsite and resin coated sand.
From the above description, the two diversion plates are placed in the diversion chamber, the proppant with the preset mass is weighed, the proppant is evenly and flatly paved between the two diversion plates, and the corresponding relation between the closing pressure of the proppant and the pore volume change of the proppant is obtained through a fracture diversion capability test experiment; adopting linear function fitting to obtain a fitting straight line for the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitting straight line as the pore compression coefficient of the proppant; and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber. The closure coefficient of the embodiment of the invention can be directly applied to numerical simulation of shale oil and gas reservoirs.
The embodiments or implementation modes in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.
In the description of the present specification, reference to the description of the terms "one embodiment", "some embodiments", "an illustrative embodiment", "an example", "a specific example", or "some examples", etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A simulation experiment method for shale oil and gas reservoir fracture closure coefficient is characterized by comprising the following steps:
placing the two guide plates into a guide chamber, weighing a proppant with preset mass, uniformly and flatly paving the proppant between the two guide plates, and obtaining a corresponding relation between the closing pressure of the proppant and the pore volume change of the proppant through a crack conductivity test experiment;
adopting linear function fitting to obtain a fitting straight line for the corresponding relation between the closing pressure and the pore volume variation of the proppant, and determining the slope of the fitting straight line as the pore compression coefficient of the proppant;
and obtaining the fracture closure coefficient of the proppant according to the pore compression coefficient, the initial distance between the two guide plates, the length of the guide chamber and the height of the guide chamber.
2. The method of claim 1, wherein the obtaining the corresponding relationship between the closing pressure of the proppant and the pore volume change of the proppant through a fracture conductivity test experiment comprises:
connecting the flow guide chamber into a pipeline of the crack flow guide capacity testing device, placing a sealed measuring cylinder at the liquid outlet, and placing the measuring cylinder on a balance;
opening a gas tank switch of the crack flow conductivity testing device, so that the liquid finally reaches the measuring cylinder through the pipeline in the flow conductivity chamber;
closing the gas tank when the liquid stably flows into the measuring cylinder, and resetting the balance;
setting a closing pressure increase value, recording closing pressure and the mass of water in a balance measuring cylinder per second, and closing the crack flow conductivity testing device when the closing pressure reaches a preset limit value, wherein the mass of the water is the volume of the water, and the volume of the water represents the pore volume variation of the proppant;
and recording the corresponding relation between the obtained closing pressure and the pore volume change of the proppant.
3. The method of claim 1, wherein the fracture closure coefficient of the proppant is obtained from the pore compressibility, the initial distance between two baffles, and the length and height of the baffle compartment by the formula:
wherein,
in the formula, CfThe closure factor of the crack, Mpa-1；
Bf-a pore compressibility;
ΔVw-as proppant pore volume change, cm3Δ p — is the closing pressure variation, MPa;
a, representing the length of the simulated crack, which is the length of the diversion chamber, cm;
b, representing the height of the simulated crack, wherein the height is the width of the diversion chamber in cm;
c, representing the initial simulated crack width, which is the initial distance, cm, between the two guide plates of the guide chamber.
4. A method according to any of claims 1-3, characterized in that the length of the diversion chamber is 17.7cm and the width of the diversion chamber is 3.8 cm.
5. Method according to claim 2, characterized in that said preset limit is 70 MPa.
6. A method according to any of claims 2-3, characterized in that the closing pressure boost value is 5 MPa.
7. The method of any one of claims 1-3, wherein the proppant is one of:
quartz sand, metal aluminum balls, walnut shells, glass beads, plastic balls, steel balls, ceramsite and resin coated sand.
Priority Applications (1)
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