Method for improving clustering effectiveness based on flow limiting and temporary plugging

Abstract

The application discloses a method for improving the effectiveness of clustering based on limited flow and temporary plugging, and is implemented according to the following steps: step 1, establishing a calculation model of fracture pressure in a target well section; step 2, determining the positions of n clusters of perforations in the target well section, and obtaining the fracture pressure according to the calculation model of fracture pressure established in step 1; step 3, establishing a model for calculating the number of perforations; step 4, solving the model established in step 3 to obtain the number of perforations of limited flow fracturing, judging whether there is a solution and whether the construction pressure limit requirement is met, if yes, executing step 5, and if no, removing the cluster with the highest fracture pressure, and solving the number of perforations of the remaining clusters until there is a solution and the construction pressure limit requirement is met; and step 5, confirming the number of clusters of limited flow fracturing and dynamic temporary plugging. The application combines the two methods of limited flow fracturing and dynamic temporary plugging, and is helpful to the uniform initiation and propagation of cracks in each cluster in the target well section.

Description

Technical Field

[0001] This invention belongs to the technical field of oil and gas field exploration and development methods, and relates to a method for improving clustering effectiveness based on flow restriction and temporary plugging. Background Technology

[0002] The main method used in horizontal tight gas wells is segmented multi-cluster fracturing. The segments are sealed with soluble bridge plugs, and the segments are fracturing simultaneously by limiting the flow to initiate multiple perforations. Currently, the following problems still exist in segmented multi-cluster fracturing of horizontal wells: ① The perforation clusters do not fracture, the fracturing is uneven, and the gas production contribution rate varies greatly, which greatly reduces the fracturing volume and seriously affects the post-fracturing production capacity; ② At present, both limiting the flow fracturing and dynamic temporary plugging can make the perforation cluster expand evenly, but the two technologies have not yet been combined; ③ The dividing line between limiting the flow fracturing and dynamic temporary plugging, which are two technologies to improve the effectiveness of the perforation clusters, has not yet been given.

[0003] Zhou Zaile, in his paper "Optimization of Perforation Parameters in Horizontal Well Flow-Limited Fracturing," proposed a design method for perforation clusters under different geostress conditions in flow-limited fracturing, but did not specify the applicability of this method. Zhang Yanjie, in his paper "Research on Perforation Parameter Design Methods in Flow-Limited Fracturing," considered the limitations of friction on flow-limited fracturing design, but did not provide specific solutions when flow-limited fracturing is not applicable. Wu Baocheng, in his paper "Experimental Study on the Migration and Plugging Law of Rope-Type Temporary Plugging Agent," and Xiao Yongjun, in his paper "Application Analysis of Temporary Plugging Technology in Volumetric Fracturing of Shale in Changning Block," both introduced the successful application of temporary plugging technology in improving clustering effectiveness; however, the use of temporary plugging agents increases the construction process and costs, and should be used in conjunction with other technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the effectiveness of fracturing clusters based on flow restriction and temporary plugging. This method combines flow restriction fracturing with dynamic temporary plugging, which helps to promote the uniform initiation and propagation of fracture clusters within the target well section.

[0005] The technical solution adopted in this invention is a method for improving clustering effectiveness based on current limiting and temporary blocking, which is implemented according to the following steps:

[0006] Step 1: Establish a calculation model for the fracture pressure within the target well section;

[0007] Step 2: Determine the location of n clusters of perforations within the target well section, and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1;

[0008] Step 3: Establish a model for calculating the number of perforations;

[0009] Step 4: Solve the model established in Step 3 to obtain the number of perforations for each cluster in the flow-limited fracturing. Determine if there is a solution that meets the construction pressure limit requirements. If yes, proceed to Step 5. If no, remove the cluster with the highest fracturing pressure and solve for the number of perforations for the remaining clusters until there is a solution that meets the construction pressure limit requirements.

[0010] Step 5: Confirm the number of clusters for flow-limited fracturing and dynamic temporary plugging.

[0011] The invention is further characterized in that,

[0012] The fracturing pressure calculation model in step 1 is a graph showing the relationship between the fracturing pressure during construction and the natural gamma ray in well logging. This graph is established using the fracturing pressure data from fractured wells with the same formation properties as the target well.

[0013] In step 2, the perforation location is selected at a position with high gas measurement interpretation and low natural gamma.

[0014] When selecting the perforation location in step 2, choose 2 to 5 perforation clusters within the target well section.

[0015] In step 2, the fracturing pressure is obtained as follows: after determining the perforation location, the natural gamma of each cluster is obtained based on the logging data, and the fracturing pressure of each cluster is obtained from the fracturing pressure calculation model established in step 1.

[0016] The specific model for determining the number of perforations in step 3 is as follows:

[0017]

[0018] Among them, Q i The flow rate allocated to the i-th perforation cluster, in m³ / s. 3 / min, where n represents the number of perforation clusters, p fi The perforation friction of the i-th perforation cluster is expressed in MPa and C. d ρ is the flow coefficient, dimensionless, and takes a value between 0 and 1. f Fluid density, in kg / m³ 3 ;

[0019] Q i The following model is satisfied:

[0020]

[0021] Among them, Q t It is the total displacement of the fracturing operation, in meters (m). 3 / min.

[0022] p fi and p i The following model is satisfied:

[0023] p i +p fi =p i+1 +p fi+1 +p i～i+1 i = 1, 2, 3, ..., n-1

[0024] Where, p i p represents the initiation pressure of the i-th crack, in MPa. fi p represents the perforation friction of the i-th perforation cluster, in MPa. i～i+1 p represents the frictional resistance along the path from the i-th crack to the (i+1)-th crack, in MPa. i+1 p represents the initiation pressure of the (i+1)th crack, in MPa. fi+1 Let be the perforation friction of the (i+1)th perforation cluster, in MPa, where each perforation cluster corresponds to one crack.

[0025] Step 4 is as follows: First, assume that all n clusters of perforations in the target well section can be opened by flow-limited fracturing. Then, use the perforation number calculation model in Step 3 to solve for these n clusters of perforations. If the perforation number calculation model in Step 3 has no solution, or if the wellhead pressure calculated by the solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of these n clusters of perforations can be opened by flow-limited fracturing. Then, remove the cluster with the highest fracturing pressure and solve for the remaining n-1 clusters, and so on.

[0026] Step 5 specifically involves: opening the perforation clusters calculated in Step 4 that meet the construction pressure limit through flow-limited fracturing, and opening the remaining perforation clusters through dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to add temporary plugging agent.

[0027] The beneficial effects of this invention are:

[0028] This invention combines flow-limiting fracturing and dynamic temporary plugging to improve the effectiveness of fracturing clusters. This method helps to promote the uniform initiation and propagation of fracture clusters within the target well section, increase the fracturing volume, and improve post-fracturing productivity. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method for improving clustering effectiveness based on current limiting and temporary blocking according to the present invention;

[0030] Figure 2 This is a graph showing the relationship between construction rupture pressure and logging natural gamma established in Embodiment 3 of the present invention;

[0031] Figure 3 This is a graph showing the relationship between construction rupture pressure and logging natural gamma established in Embodiment 4 of the present invention;

[0032] Figure 4This is a graph showing the relationship between construction rupture pressure and logging natural gamma established in Embodiment 5 of the present invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] This invention relates to a method for improving clustering effectiveness based on current limiting and temporary blocking, the process of which is as follows: Figure 1 As shown, the specific steps are as follows:

[0036] Step 1: Establish a fracture pressure calculation model within the target well section. The fracture pressure calculation model is a graph showing the relationship between the fracture pressure during construction and the natural gamma ray recorded in the well log. This graph is established using fracture pressure data from fractured wells with the same formation properties as the target well.

[0037] Step 2: Determine the location of n clusters of perforations within the target well section, and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1;

[0038] Step 3, establish a model for calculating the number of perforations, specifically as follows:

[0039]

[0040] Among them, Q i The flow rate allocated to the i-th perforation cluster, in m³ / s. 3 / min, where n represents the number of perforation clusters, p fi Let be the orifice friction of the i-th perforation cluster, in MPa and C. d ρ is the flow coefficient, dimensionless, and takes a value between 0 and 1. f Fluid density, in kg / m³ 3 ;

[0041] Among them, Q i Satisfying the flow allocation model:

[0042]

[0043] Q t It is the total displacement of the fracturing operation, in meters (m). 3 / min;

[0044] p fi and p i Satisfying the pressure balance model:

[0045] p i +p fi =p i+1 +pfi+1 +p i～i+1 i = 1, 2, 3, ..., n-1

[0046] Where, p i p represents the initiation pressure of the i-th crack, in MPa. fi p represents the perforation friction of the i-th perforation cluster, in MPa. i～i+1 p represents the frictional resistance along the path from the i-th crack to the (i+1)-th crack, in MPa. i+1 p represents the initiation pressure of the (i+1)th crack, in MPa. fi+1 The frictional resistance of the (i+1)th perforation cluster is expressed in MPa, and each perforation cluster corresponds to one crack.

[0047] Step 4: Solve the model established in Step 3 to determine the number of perforations for each cluster in the flow-limited fracturing process. Determine if a solution exists that meets the construction pressure limit requirements. If yes, proceed to Step 5. If not, remove the cluster with the highest fracturing pressure and solve for the number of perforations for the remaining clusters until a solution exists that meets the construction pressure limit requirements. Specifically:

[0048] First, assume that all n clusters of perforations in the target well section can be opened by flow-limited fracturing. Then, use the perforation number calculation model in step 3 to solve for these n clusters of perforations. If the perforation number calculation model in step 3 has no solution, or the wellhead pressure calculated by the solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of these n clusters of perforations can be opened by flow-limited fracturing. Then, remove the cluster with the highest fracturing pressure and solve for the remaining n-1 clusters, and so on.

[0049] Step 5: Confirm the number of perforation clusters for flow-limited fracturing and dynamic temporary plugging. Specifically, the perforation clusters calculated in Step 4 that meet the construction pressure limit will be opened by flow-limited fracturing, and the remaining perforation clusters will be opened by dynamic temporary plugging. If all perforation clusters meet the requirements, no temporary plugging agent needs to be added.

[0050] In this embodiment, since the tubing used in each well has the highest pressure resistance, the tubing of steel grade P110 has a maximum pressure resistance of 70MPa, that is, the wellhead pressure cannot exceed 70MPa. This is the construction pressure limit. Therefore, even if the perforation number calculation model has a solution in step 4, if the construction pressure derived from the solution is greater than the wellhead construction pressure limit, then the solution is not acceptable. Therefore, the construction pressure limit is set as the second constraint condition.

[0051] Example 2

[0052] Based on Example 1, the relationship between the construction rupture pressure and the logging natural gamma in step 1 is a linear relationship diagram or linear formula between the construction rupture pressure and the logging natural gamma.

[0053] Based on Example 1, in step 2, the perforation location is selected where the gas logging interpretation is high and the natural gamma is low. When selecting the perforation location, the number of perforation clusters in the target well section is selected as 2 to 5. The specific method for obtaining the fracture pressure is as follows: after determining the perforation location, the natural gamma of each cluster is obtained based on the logging data, and the fracture pressure of each cluster is obtained from the fracture pressure calculation model established in step 1.

[0054] Example 3

[0055] This embodiment takes a horizontal well in southeastern Jiangsu Province as an example. The horizontal section of the well is 751 meters long, and the gas layer section is 521 meters long. A staged fracturing process using soluble bridge plugs for cementing and completion of the horizontal well was employed, with 8 fracturing layers and a total of 7 fracturing stages. To improve the fracturing effectiveness of the perforation clusters in each stage and increase post-fracturing productivity, the fracturing stimulation design of this well was implemented using the method of improving cluster effectiveness based on flow restriction and temporary plugging, as described in this patent, as follows:

[0056] Step 1: Establish a fracture pressure calculation model within the target well section. Using fracture pressure data from fractured wells with formation properties similar to the target well, establish a relationship diagram between fracture pressure and logging natural gamma. Using fracture data from 10 adjacent wells in the southeastern Jiangsu region, establish a chart showing the relationship between fracture pressure and logging natural gamma in that area. Figure 2 As shown;

[0057] Step 2: Determine the location of n perforation clusters within the target well section and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1. Specifically, select locations with high gas logging interpretation and low natural gamma, and the number of perforation clusters within the preferred section is 2 to 5. The optimization results for this well are shown in Table 1. After determining the perforation location, obtain the natural gamma of each cluster based on the logging data, and obtain the fracture pressure of each cluster using the fracture pressure calculation model established in Step 1. The calculation results for this well are shown in Table 1.

[0058] Step 3: Establish a model for calculating the number of perforations;

[0059] Step 4: First, assume that all n clusters of perforations in the target well section can be opened by flow-limited fracturing. Then, use the perforation number calculation model from Step 3 to solve for these n clusters of perforations. If the perforation number calculation model in Step 3 has no solution, or if the wellhead pressure calculated by the solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of these n clusters of perforations can be opened by flow-limited fracturing. Then, remove the cluster with the highest fracturing pressure and solve for the remaining n-1 clusters, and so on.

[0060] Step 5: Confirm the number of perforation clusters for flow-limited fracturing and dynamic temporary plugging. Specifically, the perforation clusters calculated in Step 4 that meet the construction pressure limit are opened by flow-limited fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging. If all perforation clusters meet the requirements, no temporary plugging agent needs to be added. The calculation results for this well in this embodiment are shown in Table 1.

[0061] The well was modified according to the design parameters in Table 1, and the tested unobstructed flow rate was 853,400 cubic meters per day. The average unobstructed flow rate of similar comparison wells in the same block was 726,500 cubic meters per day. Compared with the adjacent comparison wells, this well performed better.

[0062] Table 1

[0063]

[0064]

[0065] Example 4

[0066] This embodiment takes a horizontal well in the central Jiangsu region as an example. The horizontal section of the well is 1450 meters long, and the gas layer section is 1178 meters long. A staged fracturing process using soluble bridge plugs for horizontal well cementing completion was employed, with 8 fracturing stages in total. To improve the fracturing effectiveness of the perforation clusters in each stage and increase post-fracturing productivity, the fracturing process of this invention was designed for this well, as detailed below:

[0067] Step 1: Establish a fracture pressure calculation model within the target well section. Using fracture pressure data from fractured wells with formation properties similar to the target well, establish a relationship diagram between fracture pressure and logging natural gamma. Using fracture data from 10 adjacent wells in the southeastern Jiangsu region, establish a chart showing the relationship between fracture pressure and logging natural gamma in that area. Figure 3 As shown;

[0068] Step 2: Determine the location of n perforation clusters within the target well section and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1. Specifically, select locations with high gas logging interpretation and low natural gamma, and the number of perforation clusters within the selected section should be 2 to 5. The selection results for this well are shown in Table 2. After determining the perforation location, obtain the natural gamma of each cluster based on the logging data, and obtain the fracture pressure of each cluster using the fracture pressure calculation model established in Step 1. The calculation results for this well are shown in Table 2.

[0069] Step 3: Establish a model for calculating the number of perforations;

[0070] Step 4: First, assume that all n clusters of perforations in the target well section can be opened by flow-limited fracturing. Then, use the perforation number calculation model from Step 3 to solve for these n clusters of perforations. If the perforation number calculation model in Step 3 has no solution, or if the wellhead pressure calculated by the solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of these n clusters of perforations can be opened by flow-limited fracturing. Then, remove the cluster with the highest fracturing pressure and solve for the remaining n-1 clusters, and so on.

[0071] Step 5: Confirm the number of perforation clusters for flow-limited fracturing and dynamic temporary plugging. Specifically, the perforation clusters calculated in Step 4 that meet the construction pressure limit are opened by flow-limited fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging. If all perforation clusters meet the requirements, no temporary plugging agent needs to be added. The calculation results for this well in this embodiment are shown in Table 2.

[0072] The well was modified according to the design parameters in Table 2, and the tested unobstructed flow rate was 967,700 cubic meters per day. The average unobstructed flow rate of similar comparison wells in the same block was 794,100 cubic meters per day. Compared with the adjacent comparison wells, this well performed better.

[0073] Table 2

[0074]

[0075]

[0076] Example 5

[0077] This embodiment takes a horizontal well in southeastern Jiangsu Province as an example. The horizontal section of the well is 1376 meters long, and the gas layer section is 770 meters long. A staged fracturing process with soluble bridge plugs was used for cementing and completion of the horizontal well, involving 8 fracturing layers and 6 fracturing stages. To improve the effectiveness of perforation cluster initiation in each fracturing stage and increase post-fracturing productivity, the fracturing and stimulation method of this invention was used to design the well fracturing process, as detailed below:

[0078] Step 1: Establish a fracture pressure calculation model within the target well section. Using fracture pressure data from fractured wells with formation properties similar to the target well, establish a relationship diagram between fracture pressure and logging natural gamma. Using fracture data from 10 adjacent wells in the southeastern Jiangsu region, establish a chart showing the relationship between fracture pressure and logging natural gamma in that area. Figure 4 As shown;

[0079] Step 2: Determine the location of n perforation clusters within the target well section and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1. Specifically, select locations with high gas logging interpretation and low natural gamma, and the number of perforation clusters within the preferred section is 2 to 5. The optimization results for this well are shown in Table 3. After determining the perforation location, obtain the natural gamma of each cluster based on the logging data, and obtain the fracture pressure of each cluster using the fracture pressure calculation model established in Step 1. The calculation results for this well are shown in Table 3.

[0080] Step 3: Establish a model for calculating the number of perforations;

[0081] Step 4: First, assume that all n clusters of perforations in the target well section can be opened by flow-limited fracturing. Then, use the perforation number calculation model from Step 3 to solve for these n clusters of perforations. If the perforation number calculation model in Step 3 has no solution, or if the wellhead pressure calculated by the solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of these n clusters of perforations can be opened by flow-limited fracturing. Then, remove the cluster with the highest fracturing pressure and solve for the remaining n-1 clusters, and so on.

[0082] Step 5: Confirm the number of perforation clusters for flow-limited fracturing and dynamic temporary plugging. Specifically, the perforation clusters calculated in Step 4 that meet the construction pressure limit are opened by flow-limited fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging. If all perforation clusters meet the requirements, no temporary plugging agent needs to be added. The calculation results for this well in this embodiment are shown in Table 3.

[0083] The well was modified according to the design parameters in Table 3, and the tested unobstructed flow rate was 1,013,400 cubic meters per day. The average unobstructed flow rate of similar comparison wells in the same block was 892,300 cubic meters per day. Compared with the adjacent comparison wells, this well performed better.

[0084] Table 3

[0085]

[0086]

[0087] Examples 3-5 demonstrate that the method of improving clustering effectiveness based on flow restriction and temporary blocking can be used to improve the balanced expansion of perforation clusters, thereby improving the effectiveness of perforation clusters and increasing post-pressurization capacity.

Claims

1. A method for improving the effectiveness of clustering based on flow restriction and temporary plugging, characterized in that, The specific steps are as follows: Step 1: Establish a fracture pressure calculation model within the target well section. The fracture pressure calculation model is a relationship diagram between the fracture pressure during construction and the natural gamma ray of the well logging. The relationship diagram between the fracture pressure during construction and the natural gamma ray of the well logging is established using fracture pressure data from fractured wells with the same formation properties as the target well. Step 2: Determine the location of n clusters of perforations within the target well section, and obtain their fracture pressure based on the fracture pressure calculation model established in Step 1; Step 3: Establish a perforation count calculation model. The perforation count calculation model is as follows: in, The flow rate allocated to the i-th perforation cluster, in units of: , n Indicates the number of perforation clusters, Let be the perforation friction of the i-th perforation cluster, in MPa; C d is the flow coefficient, dimensionless, and takes a value between 0 and 1; Fluid density, in units of kg / m 3 ; Step 4: Solve the model established in Step 3 to obtain the number of perforations for each cluster in the flow-limited fracturing. Determine if there is a solution that meets the construction pressure limit requirements. If yes, proceed to Step 5. If no, remove the cluster with the highest fracturing pressure and solve for the number of perforations for the remaining clusters until there is a solution that meets the construction pressure limit requirements. Step 5: Confirm the number of clusters for flow-limited fracturing and dynamic temporary plugging.

2. The method for improving the effectiveness of clustering based on limited flow and temporary blocking according to claim 1, characterized in that, In step 2, the perforation location is selected at a position with high gas interpretation and low natural gamma.

3. The method for improving clustering effectiveness based on flow limiting and temporary blocking according to claim 2, characterized in that, When selecting the perforation location in step 2, the number of perforation clusters in the target well section should be selected as 2 to 5.

4. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 3, characterized in that, The specific steps for obtaining the fracture pressure in step 2 are as follows: after determining the perforation location, obtain the natural gamma of each cluster based on the logging data, and obtain the fracture pressure of each cluster using the fracture pressure calculation model established in step 1.

5. The method for improving the effectiveness of clustering based on limited flow and temporary plugging according to claim 1, characterized in that, The satisfies the following model: wherein, is the total flow rate of the fracturing operation, in .

6. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 5, characterized in that, The; and satisfy the following model: in, This represents the initiation pressure of the i-th crack, in MPa. Let be the perforation friction of the i-th perforation cluster, in MPa; This represents the frictional resistance along the path from the i-th crack to the (i+1)-th crack, in MPa. This represents the initiation pressure of the (i+1)th crack, in MPa. Let be the perforation friction of the (i+1)th perforation cluster, in MPa, where each perforation cluster corresponds to one crack.

7. The method for improving the effectiveness of clustering based on limited flow and temporary blocking according to claim 6, characterized in that, Step 4 specifically involves: First, assuming that all n clusters of perforations within the target well section can be opened through flow-limited fracturing, then these n clusters of perforations are solved using the perforation number calculation model from Step 3. If the perforation number calculation model from Step 3 has no solution, or if the wellhead pressure calculated by the solution exceeds the construction pressure limit, then the assumption is incorrect, meaning that none of these n clusters of perforations can be opened through flow-limited fracturing. In this case, the cluster with the highest fracturing pressure is removed, and the remaining n-1 clusters are solved, and so on.

8. The method for improving the effectiveness of clustering based on limited flow and temporary plugging according to claim 7, characterized in that, Step 5 specifically involves: opening the perforation clusters calculated in step 4 that meet the construction pressure limit through flow-limited fracturing, and opening the remaining perforation clusters through dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to add temporary plugging agent.

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