Horizontal well fracturing temporary plugging agent capable of reducing usage amount of bridge plug and temporary plugging method

Abstract

The invention discloses a horizontal well fracturing temporary plugging agent capable of reducing the usage amount of a bridge plug and a temporary plugging method. The temporary plugging method comprises the steps that perforation is conducted on a target fracturing section of a horizontal well, and pump injection construction is conducted; judging the number of perforations opened in the target fracturing section; the pump injection displacement is reduced to a first threshold value, and a rope knot temporary plugging agent is added; judging the temporary plugging effectiveness; and if temporary plugging succeeds, the pump injection displacement is increased to a second threshold value, and pump injection construction continues to be conducted. According to the temporary plugging method, the problems that perforation crack initiation is not uniform and the construction efficiency of the packer is low can be effectively solved, and a new thought is provided for engineering application of staged fracturing of the horizontal well; and the temporary plugging agent can be used for continuously plugging under the condition that the bottom hole pressure is reduced, the perforation cluster opening rate is improved, the operation time is shortened by replacing a bridge plug, and the construction efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and particularly relates to a temporary plugging agent and a temporary plugging method for horizontal well fracturing which can reduce the usage of bridge plugs. Background Art

[0002] In the field of unconventional oil and gas field development technology, horizontal well volume fracturing and bridge plug segmentation are the mainstream technologies for realizing reserve utilization. Due to the heterogeneity of reservoir lithology and physical properties in the horizontal section, multiple perforation clusters in the same fracturing section have uneven fracturing and fluid inflow. Perforations that are easy to fracture form dominant channels and are over-modified, while perforations that are not easy to fracture have less fluid inflow and are insufficiently modified. Therefore, temporary plugging agents can be pumped during the fracturing construction to plug the perforations with dominant fluid inflow, so that the fracturing fluid is diverted to the perforations that have not been fractured and new fractures are opened, ensuring that all perforations can be fractured evenly and improving the degree of reservoir transformation. However, the granular temporary plugging agent is not plugged on the casing, but in the reservoir, and it is impossible to judge and control the location of the granular temporary plugging agent. Spherical temporary plugging agents can only plug regular circular holes, and will fall from the perforations after the construction pressure drops, and cannot maintain the plugging state.

[0003] A Chinese patent (publication number CN113637466A) discloses a high temperature resistant degradable knot-type temporary plugging agent and a preparation method thereof. The glass transition temperature (Tg) of the high temperature resistant degradable cured resin particles exceeds 220°C, which solves the problem of the short effective period (only 10 to 20 hours) of conventional temporary plugging balls at high temperatures of 150 to 180°C, and increases the effective time of plugging. A Chinese patent (publication number CN114774102A) discloses a degradable knot-type temporary plugging agent for fracturing and a preparation method thereof. The six-step process of synthesis-melting-spinning-weaving-cutting-drying can be used to directly produce the finished product. The preparation process is simple, easy to operate, and conducive to factory mass production. A Chinese patent (CN105441050A) discloses a functional bridge particle temporary plugging agent and a preparation method thereof. The proposed temporary plugging agent can adjust its structure or shape by itself under the action of pressure difference and temperature, quickly bridge the leakage channel, occupy the reservoir storage and seepage space to the maximum extent, and form a temporary plugging. However, the temporary plugging knot cannot determine the plugging position during the horizontal well fracturing process, and cannot achieve full opening of the perforation clusters, so the temporary plugging effect is difficult to ensure.

[0004] Therefore, it is urgent to develop a temporary plugging agent and temporary plugging method that can effectively plug perforations with different apertures. Summary of the invention

[0005] In view of the above problems, the present invention discloses a horizontal well fracturing temporary plugging method which can reduce the amount of bridge plugs used, comprising the following steps:

[0006] Perforate the target fracturing section of the horizontal well and perform pumping operations;

[0007] Determine the number of perforations opened in the target fracturing stage;

[0008] Reduce the pumping volume to the first threshold and add knot temporary plugging agent;

[0009] Determine the effectiveness of temporary blocking;

[0010] If the temporary plugging is successful, the pumping volume is increased to the second threshold and the pumping construction is continued.

[0011] Furthermore, the specific steps of perforating the target fracturing section of the horizontal well and performing pumping construction are as follows:

[0012] For the target fracturing section, the perforating gun is lowered to the preset depth for perforation, and then the perforating gun is lifted to the perforation position of the next section, and the preset volume of fracturing fluid and proppant is pumped in, followed by the displacement fluid;

[0013] Among them, the volume of the displacement fluid is 1 to 2 times the volume of the wellbore.

[0014] Furthermore, the settling velocity of the proppant is determined by the following formula:

[0015]

[0016] Among them, v s Indicates the sedimentation rate of the proppant; μ m represents the viscosity of the fracturing fluid; d represents the diameter of the proppant; ρ m Represents the density of the fracturing fluid; ρ p Indicates the density of the proppant.

[0017] Furthermore, the specific steps of determining the number of perforations opened in the target fracturing stage are as follows:

[0018] The waterfall diagram obtained by real-time interpretation of distributed fiber optic acoustic monitoring is used to determine whether the perforation cluster has been filled with liquid. The number of open perforations is calculated based on the number of holes in each cluster, and the amount of knot temporary plugging agent that needs to be added is determined.

[0019] Furthermore, the first threshold range is 4 to 6 m. 3 / min.

[0020] Furthermore, the specific steps of judging the effectiveness of temporary blocking are as follows:

[0021] Distributed fiber optic acoustic monitoring is used to interpret the fluid inflow of each perforation cluster in real time. If the perforation cluster that has been fractured after temporary plugging no longer has fluid inflow, while the perforation cluster that has not been fractured before temporary plugging begins to have fluid inflow, the temporary plugging is considered successful; otherwise, knot temporary plugging agent is added.

[0022] Furthermore, after the knot temporary plugging agent was added, the pumping construction pressure suddenly increased by more than 5MPa, indicating that the temporary plugging was successful.

[0023] Furthermore, the specific steps of increasing the pumping displacement to the second threshold and continuing the pumping construction are as follows:

[0024] Increase pumping capacity to 12-16m 3 / min, continue the fracturing operation, pump the preset volume of fracturing fluid and proppant, and pump the displacement fluid until the construction of this section is completed.

[0025] The present invention also discloses a temporary plugging agent for horizontal well fracturing that can reduce the amount of bridge plugs used. The temporary plugging agent is a knot structure, including a knot body, a rope body and a rope end;

[0026] The temporary plugging agent is a single rope knot, and the rope ends are divergent;

[0027] The diameter of the body is 18 to 35 mm.

[0028] Furthermore, the density of the temporary plugging agent is 0.9-1.1 g / cm 3 .

[0029] Compared with the prior art, the embodiments of the present invention have at least the following advantages: it can effectively solve the problems of uneven perforation initiation and low efficiency of packer construction, and provide a new idea for the engineering application of staged fracturing in horizontal wells; and the temporary plugging agent can continue to plug when the bottom hole pressure is reduced, thereby improving the opening rate of the perforation cluster, reducing the operation time and improving the construction efficiency by replacing the bridge plug.

[0030] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the structure of a knot temporary plugging agent according to an embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram showing real-time interpretation and judgment of temporary blocking effect of distributed optical fiber monitoring according to an embodiment of the present invention is shown;

[0034] Figure 3A schematic diagram of temporary blocking within a segment according to an embodiment of the present invention is shown;

[0035] Figure 4 A schematic diagram of plugging an open crack instead of a bridge plug according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] At present, there is no temporary plugging material and method to replace the bridge plug packer. In the process of multi-cluster fracturing in a segment, especially in a long segment multi-cluster fracturing, hole plugging is crucial to the balanced expansion of artificial fractures and the utilization of reserves. In order to solve the problems of poor temporary plugging effect and low efficiency of bridge plug segmented construction in the prior art, the present invention provides a knot-type temporary plugging agent and a temporary plugging method.

[0038] Figure 1 The schematic diagram of the structure of the knot temporary plugging agent according to an embodiment of the present invention is shown. Figure 1 As shown, the present invention proposes a temporary plugging agent for horizontal well fracturing that can reduce the amount of bridge plugs used. The temporary plugging agent for horizontal well fracturing is a knot structure, and the knot structure has a knot body, a rope body and a rope end connected in sequence. The temporary plugging agent is a single rope knot, and the rope end is divergent.

[0039] During the fracturing process, the perforations will become irregular holes due to the continuous erosion of the proppant. The rope has a small diameter, which is convenient for entering the perforations and driving the knots into the perforations and blocking the perforations. The knots deform under the pressure and can block the irregular holes.

[0040] In some embodiments, the diameter of the body is 18-35 mm.

[0041] The bodies can be made into different sizes, and different size combinations can block perforations of different diameters. For example, temporary plugging agents with a body diameter of 18 mm and a body diameter of 35 mm are mixed and used to block perforations with a diameter of 15 mm; temporary plugging agents with a body diameter of 26 mm and a body diameter of 28 mm are mixed and used to block perforations with a diameter of 20 mm.

[0042] Although the above description uses the temporary plugging agents with body diameters of 18 mm and 35 mm mixed to plug the perforations as an example, the present invention is not limited thereto, and temporary plugging agents with various body diameters can be mixed to plug perforations with different apertures. Those skilled in the art can comprehensively consider the plugging method of the present invention and actual application conditions, as long as the perforations can be plugged.

[0043] In some embodiments, the knot temporary plugging agent is made of high-strength, degradable material.

[0044] Temporary plugging agents used for fracturing will be subjected to high pressure at the bottom of the well, which may exceed 50MPa, and the construction process of each fracturing stage will last for 1 to 3 hours, so they need to be made of high-strength materials to ensure that the temporary plugging agents will not break under high pressure. After fracturing is completed, the temporary plugging agents are degraded and the perforations are reopened, allowing oil, gas, water and other fluids in the formation to flow into the wellbore and be mined from the ground.

[0045] In some embodiments, the density of the temporary plugging agent is 0.9-1.1 g / cm 3 .

[0046] The knot temporary plugging agent has the property of suspension, and different density combinations make the knot temporary plugging agent have different weights. For example, the density of the knot temporary plugging agent can be selected to be 0.9g / cm 3 and 1.1 g / cm 3 , each accounts for 50% when adding knot temporary plugging agent. For example, a total of 50 knot temporary plugging agents need to be added, then 0.9g / cm 3 and 1.1 g / cm 3 There are 25 knot temporary plugging agents each.

[0047] Although the density is 0.9g / cm 3 and 1.1 g / cm 3 The temporary plugging agent of 0.9 g / cm is mixed and used as an example for illustrative description, but the present invention is not limited to this. It can use a variety of temporary plugging agents of different densities to mix and use, for example, 0.9 g / cm 3 and 1.0g / cm 3 , 1.0g / cm 3 and 1.1 g / cm 3 Those skilled in the art can make comprehensive considerations based on the plugging method of the present invention and actual application conditions, as long as the perforation holes can be plugged.

[0048] In some embodiments, the temporary plugging agent has a coating on its surface, and the coating reacts with the fracturing fluid under the action of temperature and solidifies. After the knot temporary plugging agent is added, the knot temporary plugging agent flows into the bottom of the well along with the fracturing fluid, and the knot temporary plugging agent will block the perforation hole. When the temperature of the fracturing fluid and the knot temporary plugging agent exceeds 60°C, a curing reaction occurs, so that the knot temporary plugging agent is better fixed on the perforation hole.

[0049] According to another aspect of the present invention, a method for temporary plugging of horizontal well fracturing that can reduce the amount of bridge plugs used is provided, using the knot-type temporary plugging agent described above, and the temporary plugging method comprises the following steps:

[0050] Step 1: Perforate the target fracturing section of the horizontal well and perform pumping operations;

[0051] For the target fracturing section, the perforating gun is lowered to the preset bottom hole depth for perforating. Then the perforating gun is lifted to the preset perforating depth of the second section by cable. The pumping procedure designed for fracturing is started and the displacement is quickly increased to the preset 12-16m 3 / min, after pumping the preset volume of fracturing fluid and proppant, pump the displacement fluid. To prevent sand from coming out during the flowback process, the preset displacement fluid volume is equal to 1 to 2 times the wellbore volume. Preferably, the preset displacement volume is set to 14m 3 Preferably, the displacement fluid volume is preset to be equal to 1.5 times the wellbore volume.

[0052] Furthermore, in order to avoid the jamming of the perforating gun due to sand settling in the horizontal wellbore, the minimum settling rate that the proppant must meet during the entire construction process is calculated using the numerical model of formula (1), as follows:

[0053]

[0054] Among them, v s Indicates the sedimentation rate of the proppant; μ m represents the viscosity of the fracturing fluid; d represents the diameter of the proppant; ρ m Represents the density of the fracturing fluid; ρ p Indicates the density of the proppant.

[0055] Furthermore, in the horizontal section, the perforations located at the upper part require heavier temporary plugging agents to increase the success rate of plugging, otherwise they are not enough to resist the impact of the fracturing fluid. The knot temporary plugging agents have different weights, which give them different degrees of suspension ability in the fracturing fluid. The simulation software ANSYS FLUENT is used to calculate the optimal knot density combination.

[0056] Step 2: Determine the number of perforations opened in the target fracturing stage;

[0057] Figure 2FIG. 1 is a schematic diagram showing a distributed optical fiber monitoring real-time interpretation to determine the temporary blocking effect according to an embodiment of the present invention. The waterfall diagram obtained by the distributed optical fiber acoustic wave monitoring real-time interpretation is shown in FIG. Figure 2 As shown, it is determined whether the perforation cluster has been filled with liquid, and the number of open perforations is calculated according to the number of holes in each cluster, and the number of open perforations = the number of holes in each cluster × the number of open clusters, and the number of knot temporary plugging agents to be added is determined. Among them, the number of open perforations and the number of knot temporary plugging agents.

[0058] First, the position of the perforation cluster is calibrated according to its depth, that is, the vertical axis of the figure is the position of each cluster, and the horizontal axis is time. If the perforation cluster is filled with liquid, an acoustic vibration signal will be generated, and the signal will be transmitted to the ground through optical fiber. After signal processing, the color of the perforation cluster corresponding to the time point in the figure changes, indicating that the perforation cluster is filled with liquid.

[0059] like Figure 3 As shown, the number of holes in each cluster is 2, the number of open clusters is 3, then the number of open perforations is 6, and the number of knot temporary plugging agents that need to be added is 6.

[0060] Step 3: Reduce the pumping volume to the first threshold and add knot temporary plugging agent;

[0061] Reduce the pumping volume to 4-6m 3 / min, add knot temporary plugging agent according to the amount determined in step 2. Since the dominant perforation clusters have good connectivity with the formation, the pressure is low, and one end of the temporary plugging agent will enter these perforation clusters, and the knot will block the dominant perforations that have cracked. Preferably, the pumping displacement is reduced to 6m 3 / min.

[0062] Further, Figure 3 The schematic diagram of the temporary plugging in the segment according to the embodiment of the present invention is shown. The formation temperature is higher than the temperature of the pumped fracturing fluid. The rope knot temporary plugging agent enters the bottom of the well with the fracturing fluid and plugs the perforation hole. The temperature gradually rises under the influence of the formation. The rope end reacts with the fracturing fluid under the condition of rising temperature and solidifies, and can be fixed on the perforation hole. Figure 3 As shown, if the displacement is reduced, the knot will not fall out of the hole in the wellbore.

[0063] Step 4: Determine the effectiveness of temporary blocking;

[0064] Distributed fiber optic acoustic monitoring is used to interpret the fluid inflow of each perforation cluster in real time. If the perforation cluster that has been fractured after temporary plugging no longer has fluid inflow, while the perforation cluster that has not been fractured before temporary plugging begins to have fluid inflow, the temporary plugging is considered successful. Otherwise, knot temporary plugging agent is added, and the number is the number of perforations that failed temporary plugging.

[0065] Step 5: If temporary plugging is successful, increase the pumping volume to the second threshold and continue the pumping operation;

[0066] Rapidly increase pumping capacity to 12-16m 3 / min, continue the fracturing operation according to the pumping procedure of the fracturing design, pump the preset volume of fracturing fluid and proppant, and pump the displacement fluid until the construction of this section is completed. To prevent sand from being produced during the backflow process, the preset displacement fluid volume is equal to 1.5 times the wellbore volume, and then stop the pump. Preferably, the pumping displacement is set to 14m 3 / min.

[0067] Step 6: After the first stage of construction is completed and the pump is stopped, the perforating gun is used to perforate the second stage of the target fracturing stage of the horizontal well. After completion, the perforating gun is lifted to the preset perforating depth of the third stage, and the second stage of pumping construction is started according to the fracturing design. The total number of perforations in the first stage minus the number of knot temporary plugging agents already invested is equal to the number of knot temporary plugging agents required to completely plug the remaining perforations in the first stage. When the displacement is less than 6m 3 / min, add the corresponding amount of knot temporary plugging agent according to the calculation results. When the pumping pressure suddenly rises by more than 5MPa during the construction, it indicates that the temporary plugging is successful, and the displacement is quickly increased to 12-16m 3 / min, and continue the second stage of pumping construction. Figure 4 A schematic diagram of plugging open fractures instead of bridge plugs according to an embodiment of the present invention is shown. The above steps are repeated in all fracturing stages until the horizontal well is fracturing is completed. No bridge plug is required for mechanical isolation between the two stages. Figure 4 According to different actual working conditions, the sudden rise of pressure during pumping construction usually takes a few seconds or tens of seconds.

[0068] The temporary plugging agent and temporary plugging method for horizontal well fracturing proposed in the present invention can reduce the use of bridge plugs, effectively solve the problems of uneven fracturing in perforation and low efficiency of packer construction, and provide new ideas for the engineering application of staged fracturing in horizontal wells; moreover, the temporary plugging agent can continue to plug when the bottom hole pressure is reduced, thereby improving the opening rate of the perforation cluster, reducing the operation time and improving the construction efficiency by replacing the bridge plug.

[0069] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present disclosure. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present disclosure, the size of the serial number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure. The serial numbers of the embodiments of the present disclosure are for description only and do not represent the advantages and disadvantages of the embodiments.

[0070] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for temporary plugging of horizontal well fracturing that can reduce the amount of bridge plugs used, characterized in that: The following steps are involved: Perforate the target fracturing section of the horizontal well and perform pumping operations; Determine the number of perforations opened in the target fracturing stage; Reduce the pumping volume to the first threshold and add knot temporary plugging agent; Determine the effectiveness of temporary blocking; If the temporary plugging is successful, the pumping volume is increased to the second threshold and the pumping construction is continued.

2. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 1, characterized in that: The specific steps of perforating the target fracturing section of the horizontal well and performing pumping construction are as follows: For the target fracturing section, the perforating gun is lowered to the preset depth for perforation, and then the perforating gun is lifted to the perforation position of the next section, and the preset volume of fracturing fluid and proppant is pumped in, followed by the displacement fluid; Among them, the volume of the displacement fluid is 1 to 2 times the volume of the wellbore.

3. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 2, characterized in that: The settling velocity of the proppant is determined by the following formula: Among them, v s Indicates the sedimentation rate of the proppant; μ m represents the viscosity of the fracturing fluid; d represents the diameter of the proppant; ρ m Represents the density of the fracturing fluid; ρ p Indicates the density of the proppant.

4. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 1, characterized in that: The specific steps of determining the number of perforations opened in the target fracturing stage are as follows: The waterfall diagram obtained by real-time interpretation of distributed fiber optic acoustic monitoring is used to determine whether the perforation cluster has been filled with liquid. The number of open perforations is calculated based on the number of holes in each cluster, and the amount of knot temporary plugging agent that needs to be added is determined.

5. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 1, characterized in that: The first threshold range is 4 to 6 m 3 / min.

6. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 1, characterized in that: The specific steps for judging the effectiveness of temporary blocking are as follows: Distributed fiber optic acoustic monitoring is used to interpret the fluid inflow of each perforation cluster in real time. If the perforation cluster that has been fractured after temporary plugging no longer has fluid inflow, while the perforation cluster that has not been fractured before temporary plugging begins to have fluid inflow, the temporary plugging is considered successful; otherwise, knot temporary plugging agent is added.

7. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 6, characterized in that: After the knot temporary plugging agent was added, the pumping construction pressure suddenly increased by more than 5MPa, indicating that the temporary plugging was successful.

8. The method for temporary plugging of horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 1, characterized in that: The specific steps of increasing the pumping displacement to the second threshold and continuing the pumping construction are as follows: Increase pumping capacity to 12-16m 3 / min, continue the fracturing operation, pump the preset volume of fracturing fluid and proppant, and pump the displacement fluid until the construction of this section is completed.

9. A temporary plugging agent for horizontal well fracturing that can reduce the amount of bridge plugs used, characterized in that: The temporary plugging agent is a knot structure, including a knot body, a rope body and a rope end; The temporary plugging agent is a single rope knot, and the rope ends are divergent; The diameter of the body is 18 to 35 mm.

10. The temporary plugging agent for horizontal well fracturing capable of reducing the amount of bridge plugs used according to claim 9, characterized in that: The density of the temporary plugging agent is 0.9-1.1 g / cm 3 .

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