Method for improving clustering effectiveness based on current limiting and temporary blocking

Abstract

The invention discloses a method for improving clustering effectiveness based on current limiting and temporary plugging. The method is specifically implemented according to the following steps that 1, a fracture pressure calculation model in a target well section is established; 2, n cluster perforation positions in the target well section are determined, and the fracture pressure of the target well section is obtained according to the fracture pressure calculation model established in the step 1; step 3, establishing a perforation number solving model; 4, the model established in the step 3 is solved, the perforation number of each cluster of current-limiting fracturing is solved, whether a solution exists and meets the construction pressure limiting requirement or not is judged, if yes, the step 5 is executed, and if not, the cluster with the highest fracturing pressure is removed, and the perforation number of the remaining clusters is solved until the solution exists and the construction pressure limiting requirement is met; and 5, confirming the cluster number of current-limiting fracturing and dynamic temporary plugging. According to the method, the flow-limiting fracturing method and the dynamic temporary plugging method are combined, and uniform crack initiation and expansion of all clusters of cracks in the target well section are facilitated.

Description

Technical Field

[0001] The 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 limitation and temporary plugging. Background Art

[0002] The main body of tight gas horizontal wells uses segmented multi-cluster fracturing, with soluble bridge plugs used to isolate the segments, and flow-limiting fracturing within the segments to cause multiple clusters of perforations to fracture simultaneously. At present, the following problems still exist in the segmented multi-cluster fracturing of horizontal wells: ① The perforation clusters do not fracture, the fractures are uneven, and the contribution rates of gas production vary greatly, which greatly reduces the fracturing transformation volume and seriously affects the post-fracturing production capacity; ② At present, both flow-limiting fracturing and dynamic temporary plugging can make the perforation clusters expand evenly, but the two technologies have not been combined for use; ③ At present, the dividing point between flow-limiting fracturing and dynamic temporary plugging to improve the effectiveness of perforation clusters has not been given.

[0003] Zhou Zaile proposed a design method for perforation clusters under different geostress conditions in flow-limiting fracturing in "Optimization of Perforation Parameters in Horizontal Well Flow-Limiting Fracturing", but did not give the scope of application of this method. Zhang Yanjie considered the limitations of friction on the design of flow-limiting fracturing in "Research on Perforation Parameter Design Methods in Flow-Limiting Fracturing", but did not give a specific solution when flow-limiting fracturing is not applicable. Wu Baocheng introduced the successful application of temporary plugging technology in improving the effectiveness of clustering in "Experimental Study on the Migration and Sealing Law of Knot-Type Temporary Plugging Agents" and Xiao Yongjun introduced the successful application of temporary plugging technology in improving the effectiveness of clustering in "Analysis of the Application of Shale Temporary Plugging Technology in Volume Fracturing in Changning Block". However, the use of temporary plugging agents will increase the construction process and construction costs, and should be used in combination with other technologies. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the effectiveness of clustering based on flow limiting and temporary plugging, which combines the two methods of flow limiting fracturing and dynamic temporary plugging to help each cluster of cracks in the target well section to evenly initiate and expand.

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

[0006] Step 1, establishing a fracture pressure calculation model in the target well section;

[0007] Step 2, determining n cluster perforation positions in the target well section, and obtaining the fracture pressure according to the fracture pressure calculation model established in step 1;

[0008] Step 3, establishing a model for obtaining the number of perforations;

[0009] Step 4, solving the model established in step 3, calculating the number of perforations of each cluster of flow-limiting fracturing, and judging whether there is a solution and whether the construction pressure limit requirement is met. If so, executing step 5; if not, removing the cluster with the highest fracturing pressure, and solving the number of perforations of the remaining clusters until a solution is found and the construction pressure limit requirement is met;

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

[0011] The present invention is also characterized in that

[0012] The fracture pressure calculation model in step 1 is a relationship diagram between construction fracture pressure and logging natural gamma. The relationship diagram between construction fracture pressure and logging natural gamma is established through construction fracture pressure data of fractured wells with the same formation properties as the target well.

[0013] The perforation positions in step 2 are selected at locations with high gas logging interpretation and low natural gamma.

[0014] When selecting the perforation positions in step 2, the number of perforation clusters in the target well section is selected to be 2 to 5 clusters.

[0015] The specific steps of obtaining the fracturing pressure in step 2 are as follows: after determining the perforation position, obtaining the natural gamma of each cluster according to the logging data, and obtaining the fracturing pressure of each cluster by the fracturing pressure calculation model established in step 1.

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

[0017]

[0018] Among them, Q i The flow rate allocated to the i-th perforation cluster, in m 3 / min, n represents the number of perforation clusters, p fi is the hole friction resistance of the ith perforation cluster, in MPa, C d is the flow coefficient, dimensionless, ranging from 0 to 1; ρ f is the fluid density in kg / m 3 ;

[0019] Q i Satisfies the following model:

[0020]

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

[0022] p fi and p i Satisfies the following model:

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

[0024] Wherein, p i represents the fracture initiation pressure of the i-th fracture, with the unit of MPa; p fi is the perforation friction of the i-th perforation cluster, with the unit of MPa; p i～i+1 represents the frictional resistance along the way from the i-th fracture to the (i + 1)-th fracture, with the unit of MPa; p i+1 represents the fracture initiation pressure of the (i + 1)-th fracture, with the unit of MPa; p fi+1 is the perforation friction of the (i + 1)-th perforation cluster, with the unit of MPa, and each perforation cluster corresponds to a fracture.

[0025] Step 4 is specifically as follows: First, assume that all n perforation clusters in the target well section can be opened by limited-entry fracturing. Then, solve these n perforation clusters using the perforation number calculation model in Step 3. If the perforation number calculation model in Step 3 has no solution, or the calculated wellhead pressure obtained from the solution exceeds the construction pressure limit, it indicates that the assumption is incorrect, that is, all these n perforation clusters cannot be opened by limited-entry fracturing. Then, remove the cluster with the highest breakdown pressure and solve the remaining n - 1 clusters, and so on.

[0026] Step 5 is specifically as follows: Open the perforation clusters that are calculated in Step 4 and meet the construction pressure limit by limited-entry fracturing, and open the remaining perforation clusters by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to inject temporary plugging agents.

[0027] The beneficial effects of the present invention are:

[0028] The method for improving the effectiveness of cluster fracturing based on limited entry and temporary plugging in the present invention combines the two methods of limited-entry fracturing and dynamic temporary plugging, which helps the fractures in each cluster in the target well section to initiate and expand uniformly, increases the fracturing treatment volume, and improves the post-fracture productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flowchart of the method for improving the effectiveness of cluster fracturing based on limited entry and temporary plugging in the present invention;

[0030] Figure 2 is a relationship diagram of the construction breakdown pressure and the logging natural gamma established in Embodiment 3 of the present invention;

[0031] Figure 3 is a relationship diagram of the construction breakdown pressure and the logging natural gamma established in Embodiment 4 of the present invention;

[0032] Figure 4Graph showing the relationship between the construction fracturing pressure and the natural gamma of well logging established in Example 5 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] The present invention is based on the method of limiting current and temporarily blocking to improve the effectiveness of clustering, and its process is as follows: Figure 1 As shown, the specific steps are as follows:

[0036] Step 1, establishing a fracture pressure calculation model in the target well section; the fracture pressure calculation model is a relationship diagram between the construction fracture pressure and the natural gamma of the mud logging, and the relationship diagram between the construction fracture pressure and the natural gamma of the mud logging is established through the construction fracture pressure data of the fractured well with the same formation properties as the target well;

[0037] Step 2, determining n cluster perforation positions in the target well section, and obtaining the fracture pressure according to the fracture pressure calculation model established in step 1;

[0038] Step 3: Establish a model for obtaining the number of perforations, specifically:

[0039]

[0040] Among them, Q i The flow rate allocated to the i-th perforation cluster, in m 3 / min, n represents the number of perforation clusters, p fi is the hole friction resistance of the ith perforation cluster, in MPa, C d is the flow coefficient, dimensionless, ranging from 0 to 1; ρ f is the fluid density in kg / m 3 ;

[0041] Among them, Q i Satisfy the traffic distribution model:

[0042]

[0043] Q t is the total displacement of the fracturing operation, in 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] Among them, p i represents the initiation pressure of the i-th crack, in MPa; p fi is the hole friction resistance of the ith perforation cluster, in MPa; p i～i+1 represents the friction along the path from the i-th crack to the i+1-th crack, in MPa; p i+1 represents the initiation pressure of the i+1th crack, in MPa; p fi+1 is the perforation friction of the i+1th perforation cluster, in MPa, and each perforation cluster corresponds to a fracture;

[0047] Step 4, solve the model established in step 3, calculate the number of perforations of each cluster for flow-limiting fracturing, and determine whether there is a solution and meets the construction pressure limit requirements. If so, execute step 5. If not, remove the cluster with the highest fracturing pressure and solve the number of perforations of the remaining clusters until a solution is found and the construction pressure limit requirements are met. Specifically:

[0048] First, assume that all n clusters of perforations in the target well section can be opened by flow-limiting fracturing. Then, use the perforation number calculation model in step 3 to solve 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, these n clusters of perforations cannot be opened by flow-limiting fracturing. Then remove the cluster with the highest fracture pressure and solve the remaining n-1 clusters, and so on.

[0049] Step 5, confirm the number of clusters for flow-limiting fracturing and dynamic temporary plugging, specifically: the perforation clusters calculated in step 4 and meeting the operation pressure limit are opened by flow-limiting fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to add temporary plugging agent.

[0050] In this embodiment, since the pipe used in each well has a maximum bearing pressure, the maximum bearing pressure of the oil pipe with steel grade P110 is 70MPa, that is, the wellhead pressure cannot exceed 70MPa, which is the construction pressure limit. Therefore, in step 4, even if the model for obtaining the number of perforations has a solution, if the construction pressure inferred by using the solution is greater than the wellhead construction pressure limit, then the solution is not desirable. Therefore, the construction pressure limit is set as the second constraint condition.

[0051] Example 2

[0052] On the basis of Example 1, the relationship diagram between the construction fracturing pressure and the logging natural gamma in step 1 is a linear relationship diagram or a linear relationship expression between the construction fracturing pressure and the logging natural gamma.

[0053] On the basis of Example 1, the perforation position in step 2 is selected at a position with high gas logging interpretation and small natural gamma, and the perforation position is selected according to the number of perforation clusters in the target well section being 2 to 5 clusters; obtaining the fracture pressure is specifically as follows: after determining the perforation position, obtaining the natural gamma of each cluster according to the logging data, and obtaining the fracture pressure of each cluster by the fracture pressure calculation model established in step 1.

[0054] Example 3

[0055] This embodiment takes a horizontal well in the southeastern Jiangsu area as an example. The horizontal section of the well is 751 meters long and the gas layer section is 521 meters long. The horizontal well cementing completion soluble bridge plug staged fracturing process is adopted. The transformation box has 8 layers and a total of 7 stages of fracturing. In order to improve the effectiveness of the perforation clusters in each stage of the fracturing of the well and improve the post-fracturing production capacity, the method of improving the effectiveness of clusters based on flow limitation and temporary plugging in this patent is used to design the fracturing transformation of the well, as follows:

[0056] Step 1: Establish a fracture pressure calculation model in the target well section. Use the fracture pressure data of the fractured wells with the same formation properties as the target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging. Use the fracture construction data of 10 adjacent wells in the southeastern Jiangsu target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging in this area, as shown in Figure 1. Figure 2 As shown;

[0057] Step 2, determine the n clusters of perforation positions in the target well section, and obtain their fracture pressures according to the fracture pressure calculation model established in step 1, specifically: the position with high gas logging interpretation and small natural gamma should be selected, and the number of perforation clusters in the preferred section is 2 to 5 clusters. The optimization results of this well are shown in Table 1. After the perforation positions are determined, the natural gamma of each cluster is obtained according to the logging data, and the fracture pressure of each cluster is obtained by the fracture pressure calculation model established in step 1. The calculation results of this well are shown in Table 1;

[0058] Step 3, establishing a model for obtaining 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-limiting fracturing. Then, use the perforation number calculation model in step 3 to solve 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, these n clusters of perforations cannot be opened by flow-limiting fracturing. Then remove the cluster with the highest fracture pressure, and solve the remaining n-1 clusters, and so on.

[0060] Step 5, confirming the number of clusters for flow-limiting fracturing and dynamic temporary plugging, specifically: the perforation clusters calculated in step 4 and meeting the construction pressure limit are opened by flow-limiting fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to inject temporary plugging agents. The calculation results of the well in this embodiment are shown in Table 1.

[0061] According to the design parameters in Table 1, the well was remodeled and tested with an open flow rate of 853,400 cubic meters per day, while the average open 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 has a better effect.

[0062] Table 1

[0063]

[0064]

[0065] Example 4

[0066] This embodiment takes a horizontal well in Suzhong District as an example. The horizontal section of the well is 1450 meters long and the gas layer section is 1178 meters long. The horizontal well cementing completion soluble bridge plug staged fracturing process is adopted. The transformation box has 8 layers and a total of 8 stages of fracturing. In order to improve the effectiveness of the fracturing of the perforation clusters in each stage of the fracturing of the well and improve the post-fracturing production capacity, the method of the present invention is used to design the fracturing transformation of the well, as follows:

[0067] Step 1: Establish a fracture pressure calculation model in the target well section. Use the fracture pressure data of the fractured wells with the same formation properties as the target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging. Use the fracture construction data of 10 adjacent wells in the southeastern Jiangsu target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging in this area, as shown in Figure 1. Figure 3 As shown;

[0068] Step 2, determine the n clusters of perforation positions in the target well section, and obtain their fracture pressure according to the fracture pressure calculation model established in step 1, specifically: the position with high gas logging interpretation and small natural gamma should be selected, and the number of perforation clusters in the preferred section is 2 to 5 clusters. The optimization results of this well are shown in Table 2. After the perforation positions are determined, the natural gamma of each cluster is obtained according to the logging data, and the fracture pressure of each cluster is obtained by the fracture pressure calculation model established in step 1. The calculation results of this well are shown in Table 2;

[0069] Step 3, establishing a model for obtaining 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-limiting fracturing. Then, use the perforation number calculation model in step 3 to solve 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, these n clusters of perforations cannot be opened by flow-limiting fracturing. Then remove the cluster with the highest fracture pressure, and solve the remaining n-1 clusters, and so on.

[0071] Step 5, confirming the number of clusters for flow-limiting fracturing and dynamic temporary plugging, specifically: the perforation clusters calculated in step 4 and meeting the construction pressure limit are opened by flow-limiting fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to inject temporary plugging agents. The calculation results of the well in this embodiment are shown in Table 2.

[0072] According to the design parameters in Table 2, the well was remodeled and tested with an open flow rate of 967,700 cubic meters per day, while the average open 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 has a better effect.

[0073] Table 2

[0074]

[0075]

[0076] Example 5

[0077] This embodiment takes a horizontal well in the southeastern Jiangsu area as an example. The horizontal section of the well is 1,376 meters long and the gas layer section is 770 meters long. The horizontal well cementing completion soluble bridge plug staged fracturing process is adopted. The transformation box has 8 layers and a total of 6 stages of fracturing. In order to improve the effectiveness of the fracturing of the perforation clusters in each stage of the fracturing of the well and improve the post-fracturing production capacity, the method of the present invention is used to design the fracturing transformation of the well, as follows:

[0078] Step 1: Establish a fracture pressure calculation model in the target well section. Use the fracture pressure data of the fractured wells with the same formation properties as the target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging. Use the fracture construction data of 10 adjacent wells in the southeastern Jiangsu target well to establish a relationship diagram between the fracture pressure and the natural gamma of the mud logging in this area, as shown in Figure 1. Figure 4 As shown;

[0079] Step 2, determine the n clusters of perforation positions in the target well section, and obtain their fracture pressure according to the fracture pressure calculation model established in step 1, specifically: select the position with high gas logging interpretation and small natural gamma, and the number of perforation clusters in the preferred section is 2 to 5 clusters. The optimization results of this well are shown in Table 3. After determining the perforation position, obtain the natural gamma of each cluster according to the logging data, and obtain the fracture pressure of each cluster according to the fracture pressure calculation model established in step 1. The calculation results of this well are shown in Table 3;

[0080] Step 3, establishing a model for obtaining 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-limiting fracturing. Then, use the perforation number calculation model in step 3 to solve 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, these n clusters of perforations cannot be opened by flow-limiting fracturing. Then remove the cluster with the highest fracture pressure, and solve the remaining n-1 clusters, and so on.

[0082] Step 5, confirming the number of clusters for flow-limiting fracturing and dynamic temporary plugging, specifically: the perforation clusters calculated in step 4 and meeting the construction pressure limit are opened by flow-limiting fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to inject temporary plugging agents. The calculation results of the well in this embodiment are shown in Table 3.

[0083] According to the design parameters in Table 3, the well was remodeled and tested with an open flow rate of 1.0134 million cubic meters per day, while the average open 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 has a better effect.

[0084] Table 3

[0085]

[0086]

[0087] Examples 3-5 show that the method of improving clustering effectiveness based on flow limiting and temporary plugging of the present invention can be used to improve the balanced expansion of perforation clusters, thereby improving the effectiveness of perforation clusters and improving post-fracturing productivity.

Claims

1. Methods to improve clustering effectiveness based on current limiting and temporary blocking, It is characterized in that The specific steps are as follows: Step 1, establishing a fracture pressure calculation model in the target well section; Step 2, determining n cluster perforation positions in the target well section, and obtaining the fracture pressure according to the fracture pressure calculation model established in step 1; Step 3, establishing a model for obtaining the number of perforations; Step 4, solving the model established in step 3, calculating the number of perforations of each cluster of flow-limiting fracturing, and judging whether there is a solution and whether the construction pressure limit requirement is met. If so, executing step 5; if not, removing the cluster with the highest fracturing pressure, and solving the number of perforations of the remaining clusters until a solution is found and the construction pressure limit requirement is met; Step 5: confirm the number of clusters for flow-limiting fracturing and dynamic temporary plugging.

2. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 1, It is characterized in that The fracture pressure calculation model in step 1 is a relationship diagram between construction fracture pressure and logging natural gamma, and the relationship diagram between construction fracture pressure and logging natural gamma is established through construction fracture pressure data of fractured wells with the same formation properties as the target well.

3. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 2, It is characterized in that The perforation position in step 2 is selected at a position with high gas logging interpretation and low natural gamma.

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

5. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 4, It is characterized in that The method of obtaining the fracturing pressure in step 2 specifically comprises: after determining the perforation position, obtaining the natural gamma of each cluster according to the logging data, and obtaining the fracturing pressure of each cluster by the fracturing pressure calculation model established in step 1.

6. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 5, It is characterized in that The specific model for obtaining the number of perforations in step 3 is: Among them, Q i The flow rate allocated to the i-th perforation cluster, in m 3 / min, n represents the number of perforation clusters, p fi is the hole friction resistance of the ith perforation cluster, in MPa; C d is the flow coefficient, dimensionless, ranging from 0 to 1; ρ f is the fluid density in kg / m 3 .

7. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 6, It is characterized in that The Q i Satisfies the following model: Among them, Q t is the total displacement of the fracturing operation, in m 3 / min.

8. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 7, It is characterized in that Said; p fi and p i Satisfies the following model: p i +p fi =p i+1 +p fi+1 +p i～i+1 ,i=1,2,3,…,n-1 Among them, p i represents the initiation pressure of the i-th crack, in MPa; p fi is the hole friction resistance of the ith perforation cluster, in MPa; p i～i+1 represents the friction along the path from the i-th crack to the i+1-th crack, in MPa; p i+1 represents the initiation pressure of the i+1th crack, in MPa; p fi+1 is the perforation friction of the i+1th perforation cluster, in MPa. Each perforation cluster corresponds to a fracture.

9. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 8, It is characterized in that The step 4 is specifically as follows: first, assuming that all n clusters of perforations in the target well section can be opened by flow-limiting fracturing, then the n clusters of perforations are solved using the perforation number obtaining model in step 3; if the perforation number obtaining model in step 3 has no solution, or the wellhead pressure calculated by the obtained solution exceeds the construction pressure limit, it means that the assumption is wrong, that is, none of the n clusters of perforations can be opened by flow-limiting fracturing, then the cluster with the highest fracture pressure is removed, and the remaining n-1 clusters are solved, and so on.

10. The method for improving clustering effectiveness based on current limiting and temporary blocking according to claim 9, It is characterized in that The step 5 is specifically as follows: the perforation clusters calculated in step 4 and meeting the construction pressure limit are opened by flow-limiting fracturing, and the remaining perforation clusters are opened by dynamic temporary plugging; if all perforation clusters meet the requirements, there is no need to add temporary plugging agent.

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