CN114607332A - Two-dimensional multi-cluster crack geological model, construction method thereof, determination method of temporary blocking steering material adding time and application - Google Patents
Two-dimensional multi-cluster crack geological model, construction method thereof, determination method of temporary blocking steering material adding time and application Download PDFInfo
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Abstract
The invention provides a two-dimensional multi-cluster crack geological model, a construction method thereof, a determination method of adding time of a temporary plugging steering material and application. The construction method of the two-dimensional multi-cluster crack geological model comprises the steps of inserting a cohesive unit into the geological model, and describing the crack initiation and damage by adopting a separation-displacement curve to obtain the two-dimensional multi-cluster crack geological model. The invention also provides a method for determining the adding time of the temporary plugging steering material, which comprises the steps of adding the temporary plugging steering material for plugging at different times in the total fracturing time, fracturing before temporary plugging in the rest fracturing time, wherein the time for adding the temporary plugging steering material for plugging when the total length of the cracks is maximum and the lengths of all the cracks are most uniform after construction is the adding time of the temporary plugging steering material. The method for determining the adding time of the temporary plugging steering material can determine the adding time of the temporary plugging steering material according to the fracturing result and the fracturing shape after temporary plugging obtained at different adding times of the temporary plugging steering material.
Description
Technical Field
The invention relates to the technical field of oil and gas well fracturing construction, in particular to a two-dimensional multi-cluster fracture geological model and a construction method thereof, and a method for determining the adding time of a temporary plugging steering material during temporary plugging construction in the oil and gas well fracturing construction process and application thereof.
Background
In oil and gas wells of multilayer reservoirs, thicker reservoirs or long horizontal well sections, only a certain part of reservoirs can be reformed through one-time fracturing and acid fracturing general construction, so that the reformation needs to be carried out in a layering or segmenting mode to ensure that all reservoir sections are effectively reformed. The main method at present is mechanical cutting, and temporary plugging balls are used for temporarily plugging perforation holes. However, mechanical packing operations are complex and time consuming, and present a greater risk to high temperature deep well tool delamination. The temporary plugging ball temporary plugging process is only suitable for oil and gas wells of perforation completion. And the problem can be solved by temporarily blocking the crack. Although there are many materials that are used to temporarily block a fracture, the timing of its addition has been a challenge.
CN101553552A and CN104727800A provide a temporary blocking diverting material and a using method, respectively, but neither involves determination of the adding time.
CN107090282A provides a mixed temporary plugging agent and a temporary plugging agent mixture thereof, a temporary plugging method and application. The method is only explained for the adding time of the gel mixture temporary blocking steering material provided by the method. The conventional temporary blocking steering materials for oil and gas wells are temporary blocking particles and fibers, and an addition timing optimization method is not reported at present.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a two-dimensional multi-cluster fracture geological model, a construction method thereof, a determination method of adding time of temporary blocking steering materials, and an application thereof. The method for determining the adding time of the temporary plugging steering material has high accuracy and strong practicability, and can be widely applied to fracture acidizing construction of oil and gas wells.
In order to achieve the above object, the present invention provides a method for constructing a two-dimensional multi-cluster fracture geological model, which comprises:
acquiring geological parameters of a target area, and constructing a geological model;
and secondly, inserting cohesive units among matrix units of the geological model, and describing the crack initiation and damage by adopting a separation-displacement curve to obtain the two-dimensional multi-cluster crack geological model.
In a specific embodiment of the invention, in step one, the geological model is generally constructed by ABAQUS, which is in the form of a finite element model consisting of a finite element mesh. The geological parameters adopted for constructing the geological model generally comprise maximum principal stress, minimum principal stress, pore pressure, Young modulus, Poisson's ratio, triaxial compressive strength, single cluster perforation number before temporary plugging, injection liquid viscosity, rock tensile strength, rock shear strength, permeability, porosity, stratum pressure of a producing formation and injection temporary plugging ball number.
In a specific embodiment of the invention, the second step generally comprises inserting cohesive units into the matrix unit elements of the geological model (the cohesive units form a cohesive area model), and determining the damage form of the cohesive units (representing the crack initiation), the damage evolution law and the fluid flow law in the cohesive units (representing the damage evolution of the crack) to obtain the two-dimensional multi-cluster crack geological model.
In the specific embodiment of the present invention, in the second step, a maximum nominal stress criterion is generally adopted as the crack initiation judgment criterion of the cohesive unit, that is, when the maximum nominal stress ratio reaches 1, the damage starts, and the expression of the damage form is:
wherein, tn、ts、ttNominal stress in Pa in the normal direction of the cohesive unit, nominal stress in the first tangential direction and nominal stress in the second tangential direction;
is the critical nominal stress of the normal direction of the cohesive unit, the critical nominal stress of the first tangential direction and the critical nominal stress of the second tangential direction, and the unit is Pa;<>is a MacAuley operator, expressed as:
in the specific embodiment of the present invention, in the second step, the property of the damage variable that evolves between the beginning and the final failure of the damage is generally adopted as the damage evolution rule of the cohesive unit, and the damage evolution under the combined action of the stretching and shearing deformation of the cohesive unit is described. For example, the ABAQUS software (which may be ABAQUS 614.1 from Dassault Simulia) may be used as an evolutionary law using a damage variable, which may be defined according to the following expression:
wherein D is a damage variable,
to effectively displace the maximum value in the loading history,
for an effective displacement at the beginning of the lesion,
is the effective displacement at the time of ultimate failure.
In a specific embodiment of the present invention, in the second step, the effective displacement is determined according to the nominal strain at the normal direction, the nominal strain at the first tangential direction and the nominal strain at the second tangential direction of the cohesive unit. Specifically, the effective displacement may be defined by the following expression:
wherein, deltamIs effective displacement, deltanNominal strain, delta, normal to cohesive cellsNominal strain, delta, at the first tangent of the cohesive unittThe nominal strain at the second tangential direction of the cohesive unit.
In a specific embodiment of the present invention, in the second step, the flow law of the fluid in the cohesive unit generally includes the lateral flow law and the normal flow law of the fluid in the cohesive unit.
In a specific embodiment of the present invention, in step two, the lateral flow of the fluid in the cohesive unit generally satisfies the following equation:
wherein q is the flow rate and the unit is m3S; d is the gap opening, and the unit is m; k is a radical oftIs the tangential permeability in m2；
The Hamiltonian of the pore pressure of the cohesive unit, namely the spatial divergence of the pressure, and the unit is Pa; the tangential permeability ktThe expression (c) may be:
In a specific embodiment of the present invention, in step two, the fluid normal flow may be allowed by defining a fluid loss coefficient of the porous medium. The normal flow of fluid in the cohesive unit generally satisfies the normal fluid loss equation, which is expressed as:
wherein q ist、qbThe flow velocity of the upper surface and the flow velocity of the lower surface of the cohesive unit in the vertical direction are respectively m 3/s; p is a radical ofiIs the internal pressure of the cohesive unit in Pa; p is a radical oft、pbRespectively the upper pore pressure and the lower pore pressure of the cohesive unit in the vertical direction, and the unit is Pa; c. Ct、cbRespectively, the upper and lower fluid loss coefficients in the vertical direction of the cell.
In a specific embodiment of the invention, the geological model of two-dimensional multi-cluster fractures may have a number of fracture clusters ranging from 3 to 7 clusters, preferably from 3 to 5 clusters.
The invention also provides a two-dimensional multi-cluster fracture geological model which is constructed by the method.
The invention further provides a method for determining the adding time of the temporary blocking steering material, which comprises the following steps:
step 1, defining the fracturing starting time as 0, the total fracturing time as T, and designating one time from 0 to T as T (namely the total fracturing time T comprises two sections of time from 0 to T and time from T to T);
step 3, adding a temporary blocking steering material (namely the temporary blocking steering material) to block the opened crack at the time t;
step 4, injecting residual fluid in the time from T to T for fracturing after temporary plugging, and completing fracturing after temporary plugging;
step 5, exporting and analyzing the fracturing result and the fracturing form after temporary plugging;
and 6, selecting different moments within the time from 0 to T as T, repeating the steps 2 to 5, comparing fracturing results and fracturing forms obtained at different moments, and determining the moment T with the largest total length of the crack and the most uniform and corresponding length of each crack, namely the moment when the temporary blocking steering material is added.
In a specific embodiment of the present invention, in step 1, the T may be one of 0T (i.e. at the beginning of fracturing), 10% T, 20% T, 30% T, 40% T, 50% T, 60% T, 70% T, 80% T, 90% T, 100% T (i.e. at the completion of fracturing).
In a specific embodiment of the present invention, the method may include, after the time t is specified in step 1, performing a temporary plugging fracturing experiment in a flow distribution test experimental apparatus in advance according to the time t of adding the temporary plugging diverting material, wherein the flow distribution of each cluster of cracks before and after temporary plugging is recorded, and then performing steps 2-4 of the method. The number of the cracks in the step 2 is equal to that of the cracks in the flow distribution test experimental device, and the flow distribution condition of the fluid distributed to the clusters of cracks in the step 2 and the step 4 is the same as that of the clusters of cracks before and after temporary plugging in the temporary plugging pressure experiment performed in advance.
In the embodiment of the present invention, in step 5, the fracture result and fracture morphology generally refer to the length of the multiple clusters of fractures and the propagation morphology of the multiple clusters of fractures (including uniformity of the fractures, etc.).
In an embodiment of the present invention, fig. 1 is a schematic flow chart of a method for determining the timing of temporarily blocking the addition of a diverting material. As shown in fig. 1, the method may include:
1. acquiring geological parameters of a target area, and constructing a geological model;
2. inserting cohesive units (the cohesive units form a cohesive area model) into the matrix unit elements of the geological model, and determining the damage form and the damage evolution rule of the cohesive units and the flowing rule of fluid in the cohesive units to obtain the two-dimensional multi-cluster fracture geological model;
the maximum nominal stress criterion is used as the initial crack judgment criterion of the cohesive unit, and the damage form expression of the cohesive unit is as follows:
wherein, tn、ts、ttRespectively nominal stress of the normal direction of the cohesive unit, nominal stress of a first tangential direction and nominal stress of a second tangential direction, and the unit is Pa;
is the critical nominal stress of the cohesive unit normal direction, the critical nominal stress of the first tangential direction and the critical nominal stress of the second tangential direction, and the unit is Pa;<>is a MacAuley operator, expressed as:
using the property of the damage variable that evolves between the beginning and the final failure of the damage as the damage evolution law of the cohesive unit, describing the damage evolution under the combined action of the stretching and shearing deformation of the cohesive unit, using the damage variable as the evolution law using ABAQUS software (e.g. ABAQUS 614.1 from Dassault Simulia) as the evolution law, the damage variable can be defined according to the following expression:
wherein D is a damage variable,
to effectively displace the maximum value in the loading history,
for an effective displacement at the beginning of the lesion,
effective displacement at the time of final failure;
the above effective displacement may be defined by the following expression:
wherein, deltamIs effective displacement, deltanNominal strain, delta, normal to cohesive cellsNominal strain, delta, at the first tangent of the cohesive unittNominal strain at a second tangential direction of the cohesive unit;
the lateral flow of fluid in the cohesive unit generally satisfies the following equation:
wherein q is the flow rate and the unit is m3S; d is the gap opening, and the unit is m; k is a radical oftIs the tangential permeability in m2；
The Hamiltonian of the pore pressure of the cohesive unit, namely the spatial divergence of the pressure, and the unit is Pa;
wherein the tangential permeability ktThe expression (c) may be:
d is the gap opening, and the unit is m; μ is the fluid viscosity in Pa · s;
the normal flow of fluid in the cohesive unit generally satisfies the normal fluid loss equation, which is expressed as:
wherein q ist、qbThe flow velocity of the upper surface and the flow velocity of the lower surface of the cohesive unit in the vertical direction are respectively m 3/s; p is a radical ofiIs the internal pressure of the cohesive unit in Pa; p is a radical oft、pbRespectively the upper pore pressure and the lower pore pressure of the cohesive unitForce in Pa; c. Ct、cbThe filter loss coefficients above the unit and below the unit are respectively;
3. defining the fracturing starting time as 0, the fracturing total time as T, and designating one time from 0 to T as T (namely the fracturing total time T comprises two sections of time from 0 to T and time from T to T);
4. injecting fluid into the two-dimensional multi-cluster fracture geological model obtained in the step 2 within 0-t time for fracturing before temporary plugging; adding a temporary plugging steering material to plug the opened crack at the time t; injecting residual fluid within the time from T to T for fracturing after temporary plugging; deriving and analyzing the fracturing result and the fracturing morphology (including the length of the multiple clusters of fractures and the expansion morphology of the multiple clusters of fractures) after temporary plugging;
5. and (3) selecting different moments from 0 to T as T, repeating the steps from 2 to 5, comparing the fracturing results and the fracturing forms obtained at different moments, and determining the moment T with the maximum total length of the crack and the most uniform length of each crack, namely the moment when the temporary blocking steering material is added.
The invention also provides application of the optimization method in fracturing and acidizing construction of oil and gas wells. For example, the optimization method can be applied to fracture acidizing construction of a reservoir where one or a combination of more than two of carbonate rock, shale, volcanic rock, sandstone and glutenite are located; the optimization method is suitable for fracturing and acidizing construction adopting one of an oil well, a gas well and a gas-oil well; the optimization method is suitable for fracture acidizing construction of one of a vertical well, a horizontal well and a highly deviated well; meanwhile, the optimization method is suitable for temporary blocking steering materials in various forms, such as temporary blocking particles and temporary blocking fibers.
The invention has the beneficial effects that:
1. compared with other methods in the field, the method for constructing the two-dimensional multi-cluster fracture geological model provided by the invention adds the expansion simulation of temporary plugging of the steering material for plugging the dominant fracture in the multi-cluster fracture expansion, and can realize the expansion form characterization of the hydraulic fracture in the geological model.
2. The method for determining the adding time of the temporary plugging steering material can determine the adding time of the temporary plugging steering material according to the fracturing result and the fracturing shape after temporary plugging obtained at different adding times of the temporary plugging steering material. The optimization method has high accuracy and strong practicability, and can be widely applied to fracture acidizing construction of oil and gas wells.
Drawings
Fig. 1 is a schematic flow chart of a method for determining the timing of temporarily blocking the addition of a steering material.
FIG. 2 is a graph showing the results of inserting a cell into a cell in the matrix of example 1.
FIG. 3 is a schematic diagram of a two-dimensional multi-cluster fracture geological model in example 1.
Fig. 4 is a graph showing the experimental results of comparative example 1.
FIG. 5 is a graph showing the results of experiment (1).
FIG. 6 is a graph showing the results of experiment (2).
FIG. 7 is a graph showing the results of experiment (3).
FIG. 8 is a graph showing the results of experiment (4).
Fig. 9 is a schematic diagram of the structure of the flow distribution test experimental apparatus in example 2 and comparative example 1.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The embodiment provides a geological model method for constructing a two-dimensional multi-cluster fracture, which comprises the following steps:
1. the geological model of the reservoir interval of well a was created using the geological parameters in table 1 in the ABQUS14.1 software of Dassault Simulia:
TABLE 1
| Model parameters | Numerical value | Model parameters | Numerical value |
| Maximum principal stress (MPa) | 52 | Viscosity of injection solution (mPa. s) | 1 |
| Minimum principal stress (MPa) | 47 | Tensile strength of rock (MPa) | 6 |
| Pore pressure (MPa) | 35.125 | Rock shear strength (MPa) | 20 |
| Young's modulus (GPa) | 21.0 | Permeability (mD) | 1 |
| Poisson ratio | 0.2 | Porosity of | 0.1 |
| Triaxial compressive strength (MPa) | 213.9 | Producing formation pressure (MPa) | 35.125 |
| Single cluster perforation number before temporary plugging | 12 | Number of temporary plugging ball (one) for injection | 30 |
2. The matrix unit in the geological model is inserted into the cohesive unit to represent the expansion of the crack, a separation-displacement curve is adopted to describe the crack initiation and the damage, a cohesive area model simulating the crack expansion is constructed, the damage form and the damage evolution rule of the cohesive unit and the flow rule of fluid in the cohesive unit are determined, and the specific process is as follows:
the maximum nominal stress criterion was used, i.e. it was considered that damage started when the maximum nominal stress reached 1. The damage pattern is:
wherein, tn、ts、ttNominal stress in the normal direction, nominal stress in the first tangential direction and nominal stress in the second tangential direction of the cohesive unit respectively, and the unit is Pa;
is the normal critical nominal stress, the first tangential critical nominal stress and the second tangential critical nominal stress of the cohesive unit, and has the unit of Pa;<>is a MacAuley operator, expressed as:
introducing effective displacement deltamIt is defined as:
wherein, deltamIs effective displacement, deltanNominal strain, delta, normal to cohesive cellsNominal strain, delta, at the first tangent of the cohesive unittThe nominal strain at the second tangential direction of the cohesive unit.
And describing the property of the damage variable D evolving between the beginning and the final failure of the damage by using the effective displacement, and describing the damage evolution under the combined action of the stretching and shearing deformation of the cohesive unit. For linear degradation law, ABAQUS uses the impairment variable D as the evolution law, with the expression:
wherein, the first and the second end of the pipe are connected with each other,
for the maximum value of the effective displacement in the loading history,
for an effective displacement at the beginning of the lesion,
is the effective displacement at the time of ultimate failure.
The cross flow pattern of the fluid in the cohesive unit is then defined. The lateral flow of fluid in the cohesive unit satisfies the viscous fluid flow equation:
q is the flow rate in m3D is the gap opening in m, kt is the tangential permeability in m2，
The operator is a Hamiltonian of the pore pressure of the cohesive unit, and the unit is Pa;
wherein the tangential permeability ktThe calculation formula of (2) is as follows:
d is the gap opening, and the unit is m; μ is the fluid viscosity in Pa · s.
The flow of fluid in the direction perpendicular to the fracture plane is mainly the fluid loss process, and the fluid normal flow is allowed by defining the fluid loss coefficient of the porous medium.
The fluid loss equation is:
wherein q ist、qbThe flow velocity of the upper surface and the flow velocity of the lower surface of the cohesive unit in the vertical direction are respectively m 3/s; p is a radical ofiIs the internal pressure of the cohesive unit in Pa; p is a radical oft、pbRespectively the pore pressure above the cohesive unit and the pore pressure below the cohesive unit, and the unit is Pa; c. Ct、cbThe fluid loss coefficients above and below the cohesive unit are provided.
And inserting the constructed cohesive units (pore pressure cohesive units) into a finite element grid of the geological model to obtain a diagram 2. As shown in FIG. 2, the insertion process is to insert the pore pressure cohesiveness elements between the finite element meshes (100m × 200m), and the pore pressure cohesiveness elements comprise displacement nodes and pore pressure nodes, so that the expansion form of the hydraulic fracture can be effectively characterized.
FIG. 3 is a schematic diagram of a two-dimensional multi-cluster fracture geological model. The model is 100m long and 200m high, 5 clusters of cracks are distributed, the cluster spacing is 15m, and the number of cluster perforation is 12 holes.
The flow distribution of each cluster of fractures in the following examples and comparative examples was determined from a temporary plugging fracturing experiment performed in advance in a flow distribution test experimental apparatus. The apparatus for performing the flow distribution test experiment generally comprises a water tank, a power unit, a temporary blocking diverting material delivery device and an experimental pipeline. The power device adopts a 700-type fracturing pump, can adjust the discharge capacity of the carrying fluid from 0.26 square/minute to 0.53 square/minute, and can effectively simulate the working condition on site; the temporary blocking steering material delivery device can control the quantity of the temporary blocking steering materials on line; the experiment pipeline adopts visual tubular column, and the position that can better observe shutoff effect and stifled steering material temporarily stopped up is divided into 5 simultaneously and is clustered, can be used to simulate 5 cluster flow distribution. Specifically, the specific structure of the experimental apparatus for flow distribution testing is shown in fig. 9, and the apparatus mainly includes: the device comprises a water tank 1, a high-pressure power device 2, a temporary blocking steering material ball throwing device 3-6 and an experimental pipeline 7-15. When the flow distribution experiment is carried out, the carrying fluid in the water tank 1 is pumped out through the high-pressure power device 2, and then the temporary blocking steering materials are delivered into the experiment pipeline 7 through the switches controlling the four valves of the ball throwing devices 3-6. The temporary blocking steering material in the experimental pipeline 7 enters the visual pipe column 10 through the pressure gauge 8 and the pressure relief protection valve 9 (which can effectively guarantee the safety of personnel and test the pressure). The visual pipe column 10 is an organic glass pipe column, perforations 11 are arranged on the wall of the pipe column and divided into 5 clusters, the perforations 11 are spirally distributed and used for simulating the real perforation position on site, the pneumatic valve 12 is used for connecting the perforations with a PC pipe, and flowmeters 13-1 to 13-5 are arranged on the PC pipe. The outflow string 14 is a cluster of outflow strings and the valve 15 is used for pressure relief protection. The temporarily blocked diverting material in the visualization string 10 enters the PC pipe via pneumatic valve 12, exits through the outflow string 14, and the flow distribution of the multiple fractures is recorded by flow meters 13-1 to 13-5. The total flow rate distribution test time was 1200s, and when the test was carried out using a discharge capacity of 0.53 square/min, the flow rate ratio before and after temporary plugging, which was recorded by the flow meters on the lines of 5 clusters (1, 2, 3, 4, 5 clusters) without the temporary plugging diverting material and with the temporary plugging diverting material fed at 360s, 600s, 840s, 1080s, respectively, is detailed in table 2.
TABLE 2
Comparative example 1
This comparative example provides a fracturing process without the addition of a temporary plugging diverting material comprising:
the total injection displacement of injection liquid in the geological model of the two-dimensional multi-cluster fracture (figure 3) constructed by adopting the method of example 1 is 12m3The total fracturing time is 1200s, and each cluster of fractures distributes injection fluid according to each cluster of fractures before temporary plugging in the table 2The results of the experiment on the propagation of the length of each fracture are shown in FIG. 4.
As can be seen from FIG. 4, the lengths of the 5 cracks after the test after the expansion are respectively 98.6m, 76.5m, 23.5m, 76.5m and 98.6 m. The middle cracks are seriously disturbed by stress and flow distribution, and are extruded by the side cracks, and the middle cracks cannot uniformly obtain fluid, so that the cracks are in a non-uniform expansion form.
Example 2
The embodiment provides a method for determining the adding time of a temporary blocking steering material, which is simulated on a geological model of a two-dimensional multi-cluster fracture constructed in the embodiment 1 and specifically comprises the following steps:
(1) controlling the total injection displacement to be 12m3Min, total fracturing time 1200 s. The experiment was performed with 30% of the total fracturing time selected as the timing for adding the temporary plugging diverting material. The method specifically comprises the following steps: in the geological model (fig. 3) of the two-dimensional multi-cluster fracture constructed by the method of example 1, within 0-360s, the length of each cluster of fractures is expanded according to the amount of injected fluid distributed to each cluster of fractures before temporary plugging in the results of the flow distribution test experiment of table 2; then adding a temporary plugging steering material at the moment of 360s to realize plugging; the remaining length was extended over a period of 360-1200 s (840 s total) according to the amount of injected fluid distributed to each cluster of fractures after the temporary plugging in the results of the flow distribution test experiment of table 2. The results of the experiment are shown in FIG. 5.
As can be seen in fig. 5, the propagation morphologies of the 5 clusters of cracks were 95.6 meters, 78.5 meters, 30.5 meters, 78.5 meters, and 95.6 meters, respectively, although the crack morphology was shown with underdeveloped medial (HF3) and lateral (HF2 and HF4) seams and with overgrowth of lateral (HF1 and HF5) seams; however, compared with the results of comparative example 1, the inferior crack of HF3 in this experiment was 30.5 meters, and the inferior crack of HF3 in comparative example 1 was extended to 23.5 meters, which was improved; the crack lengths of HF1 and HF5 were reduced from 98.6 meters (comparative example 1) to 95.6 meters (this experiment) and were suppressed. This indicates that when the temporary plugging time is 360s, uniform reconstruction of the crack can be reconstructed to a certain extent, the propagation of the middle disadvantaged crack (HF3) is promoted, and the excessive propagation of the side seams (HF1 and HF5) and the secondary side seams (HF2 and HF4) is inhibited.
(2) Controlling total injection displacementIs 12m3And/min, the total fracturing time is 1200s, and 50% of the total fracturing time is selected as the time for adding the temporary blocking steering material for carrying out the experiment. The method specifically comprises the following steps: in the geological model (figure 3) of the two-dimensional multi-cluster fracture constructed by adopting the method of the embodiment 1, the length of each cluster of fractures is expanded within 0-600s according to the quantity of the injected fluid distributed to each cluster of fractures before temporary plugging in the results of the flow distribution test experiment shown in the table 2; then adding a temporary plugging steering material to realize plugging at the time of 600 s; the length extension was performed according to the amount of injected fluid distributed to each cluster of fractures after the temporary plugging in the results of the flow distribution test experiment of table 2 over a period of 600s-1200s (total 600 s). The results of the experiment are shown in FIG. 6. As can be seen from fig. 6, after the experiment, the crack propagation forms of 5 cracks are 93.6 meters, 82.5 meters, 53.5 meters, 82.5 meters and 93.6 meters, respectively, and the crack improvement degrees are improved and the crack lengths are more uniform than those of comparative example 1.
(3) Controlling the total injection displacement to be 12m3And/min, the total fracturing time is 1200s, and 70% of the total fracturing time is selected as the time for adding the temporary blocking steering material for carrying out the experiment. The method specifically comprises the following steps: in the geological model (figure 3) of the two-dimensional multi-cluster fracture constructed by adopting the method of the embodiment 1, the length of each cluster of fractures is expanded within 0-840s according to the quantity of the injected fluid distributed to each cluster of fractures before temporary plugging in the results of the flow distribution test experiment shown in the table 2; then adding a temporary plugging steering material to realize plugging at 840 s; the length extension was performed in 840s-1200s (360 s total) according to the amount of injected fluid distributed to each cluster of fractures after the temporary plugging in the results of the flow distribution test experiment of table 2. The results of the experiment are shown in FIG. 7. As can be seen from fig. 7, after the experiment, the crack propagation forms of 5 cracks are 97.6 meters, 80.5 meters, 25.5 meters, 80.3 meters and 98 meters, respectively, the crack improvement degrees are improved compared with the crack length of comparative example 1, and the crack lengths are more uniform.
(4) Controlling the total injection displacement to be 12m3And/min, the total fracturing time is 1200s, and 90% of the total fracturing time is selected as the time for adding the temporary blocking steering material for carrying out the experiment. The method specifically comprises the following steps: in the geological model of two-dimensional multi-cluster fractures (fig. 3) constructed by the method of example 1, the pre-plugging clusters of fractures in the results of the flow distribution test experiment according to table 2 were tested over a period of 0-1080sThe slot distributes the amount of injection fluid for length expansion; then adding a temporary plugging steering material at 1080s to realize plugging; the length extension was performed according to the amount of injected fluid distributed to each cluster of fractures after the temporary plugging in the results of the flow distribution test experiment of table 2 over a period of 1080s-1200s (120 s total). The results of the experiment are shown in FIG. 8.
As can be seen from fig. 8, in experiment 5, the crack propagation forms are respectively 98.0 meters, 80.3 meters, 24.5 meters, 80.3 meters and 98 meters, the crack improvement degree is improved compared with the crack length of comparative example 1, and the crack length is more uniform.
The fracture uniformity of comparative example 1 was found to be the worst, and the total reconstruction length was 373.7m, which is lower than the experiments (1) to (4) in this example, using the longitudinal fracture length and the uniformity of fracture propagation obtained in comparative example 1 and experiments (1) to (4) as indicators of the reconstruction effect. The experimental results of the statistical experiments (1) to (4) show that as the time for injecting the temporary plugging diversion material is within the percentage of the total fracturing time, the temporary plugging fracturing improvement effect gradually rises and peaks, wherein when the temporary plugging injection time is within 50% of the fracturing time (namely, the temporary plugging time is 600s after fracturing), the temporary plugging fracturing improvement effect is best, the total fracturing improvement length is 405.7 m, and then the temporary plugging time is reduced in percentage of the total fracturing time. Therefore, it is determined that when the temporary steering material injection time T is 50% T, the optimum timing of the temporary steering material injection.
And carrying out temporary plugging construction on a production well in a remote area to verify the optimization time effect.
The horizontal section of the A202H2-1 well is divided into 30 sections for fracturing, 400kg of temporary plugging steering material is added for temporary plugging steering when 50% of the fracturing time of each section, and the yield of the well is 55.5 ten thousand square/day after construction.
The horizontal section of the A202H2-2 well is divided into 30 sections for fracturing, 400kg of temporary blocking steering material is added for temporary blocking steering when the fracturing time of each section is 30%, and the yield of the well after construction is 38.9 ten thousand square per day.
The horizontal section of the A202H2-3 well is divided into 30 sections for fracturing, 400kg of temporary blocking steering material is added for temporary blocking steering when 70% of the fracturing time of each section is reached, and the yield of the well is 40.5 ten thousand square/day after construction.
The horizontal section of the A202H2-4 well is divided into 30 sections for fracturing, 400kg of temporary blocking steering material is added for temporary blocking steering when 90% of the fracturing time of each section is reached, and the yield of the well is 20.6 ten thousand square/day after construction.
From the construction results, when the temporary plugging injection time is 50% of the fracturing time, the temporary plugging fracturing effect is the best, the construction result is consistent with the result provided by the optimization method, and the method for determining the adding time of the temporary plugging diverting material provided by the invention is proved to be high in accuracy and strong in practicability, and can be widely applied to fracturing and acidizing construction of oil and gas wells.
Claims (15)
1. A method of constructing a two-dimensional multi-cluster fracture geological model, comprising:
acquiring geological parameters of a target area, and constructing a geological model;
and secondly, inserting cohesive units among matrix units of the geological model, and describing the crack initiation and damage by adopting a separation-displacement curve to obtain the two-dimensional multi-cluster crack geological model.
2. The method of claim 1, wherein in step one, the geological model is constructed by ABAQUS software;
preferably, the geological parameters comprise maximum principal stress, minimum principal stress, pore pressure, Young modulus, Poisson's ratio, triaxial compressive strength, number of single cluster perforations before temporary plugging, injection fluid viscosity, rock tensile strength, rock shear strength, permeability, porosity, formation pressure of a producing formation and number of injected temporary plugging balls.
3. The method according to claim 1 or 2, wherein the second step comprises inserting cohesive units into the matrix unit elements of the geological model, and determining the damage form, the damage evolution law and the fluid flowing law of the cohesive units to obtain the two-dimensional multi-cluster fracture geological model.
4. The method according to claim 1 or 3, wherein in the second step, a maximum nominal stress criterion is adopted as a crack initiation judgment criterion of the cohesive unit, namely when the maximum nominal stress ratio reaches 1, the damage is started, and the damage form is expressed as:
wherein, tn、ts、ttNominal stress in the normal direction, nominal stress in the first tangential direction and nominal stress in the second tangential direction of the cohesive unit respectively, and the unit is Pa;
is the normal critical nominal stress, the first tangential critical nominal stress and the second tangential critical nominal stress of the cohesive unit, and has the unit of Pa;<>is a MacAuley operator, expressed as:
5. the method according to any one of claims 1, 3 and 4, wherein in the second step, the property of the damage variable that evolves between the beginning and the final failure of the damage is used as the damage evolution rule of the cohesive unit to describe the damage evolution under the combined action of stretching and shearing deformation of the cohesive unit;
preferably, the expression of the damage variable is:
wherein D is a damage variable,
to effectively displace the maximum value in the loading history,
for an effective displacement at the beginning of the lesion,
is the effective displacement at the time of ultimate failure.
6. The method according to claim 5, wherein in step two, the effective displacement is determined according to a nominal strain of a normal direction, a nominal strain of a first tangential direction and a nominal strain of a second tangential direction of the cohesive unit;
preferably, the expression of the effective displacement is:
wherein, deltamIs effective displacement, deltanNominal strain, delta, normal to cohesive cellsNominal strain, delta, at the first tangent of the cohesive unittThe nominal strain at the second tangential direction of the cohesive unit.
7. The method according to claim 3, wherein in the second step, the flow law of the fluid in the cohesive unit comprises a lateral flow law and a normal flow law of the fluid in the cohesive unit.
8. The method of claim 7, wherein the lateral flow of fluid in the cohesive unit satisfies the following equation:
wherein q is the flow rate and the unit is m3D is the gap opening, and the unit is m, ktIs the tangential permeability in m2，
The operator is a Hamiltonian of the pore pressure of the cohesive unit, and the unit is Pa;
preferably, the calculation formula of the tangential permeability is as follows:
wherein k istIs the tangential permeability in m2(ii) a d is the gap opening, and the unit is m; μ is the fluid viscosity in Pa · s.
9. The method of claim 7, wherein the normal flow of fluid in the cohesive unit satisfies the normal fluid loss equation expressed as:
wherein q ist、qbThe flow velocity of the upper surface and the flow velocity of the lower surface of the cohesive unit in the vertical direction are respectively m 3/s; p is a radical ofiIs the internal pressure of the cohesive unit in Pa; p is a radical oft、pbRespectively the pore pressure above the cohesive unit and the pore pressure below the cohesive unit, and the unit is Pa; c. Ct、cbThe fluid loss coefficients above and below the cohesive unit are provided.
10. The method of claim 1, wherein the geological model of two-dimensional multi-cluster fractures has a fracture cluster number of 3-7 clusters, preferably 3-5 clusters.
11. A two-dimensional multi-cluster fracture geological model constructed by the method of any of claims 1-10.
12. A method for determining a timing of temporarily blocking addition of a steering material, comprising:
step 1, defining the fracturing starting time as 0, the total fracturing time as T, and designating one time from 0 to T as T;
step 2, injecting fluid into the two-dimensional multi-cluster fracture geological model of claim 11 within 0 to t time for fracturing before temporary plugging;
step 3, adding a temporary plugging steering material to plug the opened crack at the time t;
step 4, injecting residual fluid in the time from T to T for fracturing after temporary plugging, and completing fracturing after temporary plugging;
step 5, exporting and analyzing the fracturing result and the fracturing form after temporary plugging;
and 6, selecting T as different moments within 0-T, repeating the steps 2-5, comparing fracturing results and fracturing forms obtained at different moments, and determining the moment T with the largest total length of the crack and the most uniform length of each crack, namely the moment when the temporary blocking steering material is added.
13. The method of claim 12, wherein in step 1, T is one of 0T, 10% T, 20% T, 30% T, 40% T, 50% T, 60% T, 70% T, 80% T, 90% T, 100% T.
14. The method of claim 12, wherein the fracture results and fracture morphology refer to the length of the multiple clusters of fractures and the propagation morphology of the multiple clusters of fractures in step 5.
15. Use of the method of determining the timing of addition of a temporary plugging diversion material of any of claims 12-14 in a fracturing acidizing construction of an oil and gas well;
preferably, the lithofacies of the reservoir in which the fracture acidizing construction is performed comprises one or a combination of more than two of carbonate rock, shale, volcanic rock, sandstone and conglomerate;
preferably, the well used in the fracture acidizing construction comprises one of an oil well, a gas well and a gas and oil well;
preferably, the well for the fracture acidizing construction comprises one of a vertical well, a horizontal well and a highly deviated well;
preferably, the temporary blocking diverting material adopted by the fracture acidizing construction comprises temporary blocking particles and/or temporary blocking fibers.
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