Fracturing process method for horizontal well to laterally penetrate through mudstone to communicate with oil layer

Abstract

The invention provides a fracturing process method for a horizontal well to laterally penetrate through a mudstone communication oil layer. The fracturing process method mainly solves the problem that due to the fact that an existing sandstone layer section fracturing process method is adopted, the length of a crack formed in mudstone is not enough, and a wellbore and lateral oil-containing sandstone cannot be effectively fractured. The method is characterized by comprising the following steps that S1, a fracturing wellhead is installed, and a fracturing manifold and a vehicle set are connected; s2, performing pressure test on a surface pipeline and a gate until the pressure is qualified; s3, perforation is conducted on the target interval; s4, main fracturing construction is started, and an artificial fracture is formed to communicate with a lateral oil layer; s5, all fracturing construction of the remaining sections of the target horizontal well is completed section by section; and S6, after construction of all designed target layer sections is completed, the well is closed, and flowback is conducted according to design requirements. According to the fracturing process method for laterally penetrating through the mudstone communication oil layer of the horizontal well, it can be ensured that an effective oil flow channel is formed between the shaft and the oil layer, effective utilization of the lateral oil layer is achieved, and the production requirement of the lateral oil layer is met.

Description

Technical Field

[0001] The invention relates to the technical field of oil production engineering, and in particular to a fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer. Background Art

[0002] Due to geological reasons such as river bends, some horizontal wells encounter mudstone sections and sandstone sections in the horizontal section. Oil-bearing sandstones are developed laterally in the mudstone sections. If the mudstone sections are not transformed, it will lead to reserve loss. If the sandstone section fracturing process is used in the mudstone section, the length of the cracks formed in the mudstone will be insufficient, and the wellbore cannot be effectively connected to the lateral oil-bearing sandstone, or after the connection, effective support cannot be formed, and the oil flow channel cannot be guaranteed to be effective in the long term, and the lateral oil layer production needs cannot be met. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the problem in the background technology that if the sandstone layer fracturing process method is used in the horizontal mudstone layer section drilled, the length of the cracks formed in the mudstone will be insufficient to effectively connect the wellbore with the lateral oil-bearing sandstone, and a fracturing process method for a horizontal well to laterally penetrate the mudstone to communicate with the oil layer is provided. The fracturing process method for a horizontal well to laterally penetrate the mudstone to communicate with the oil layer can ensure the formation of an effective oil flow channel between the wellbore and the oil layer, realize the effective mobilization of the lateral oil layer, and meet the production needs of the lateral oil layer.

[0004] The present invention can solve the problem through the following technical solution: The fracturing process of the horizontal well penetrating the mudstone to communicate with the oil layer laterally comprises the following steps:

[0005] S1: Install the fracturing wellhead and connect the fracturing manifold and the train set;

[0006] S2: Test the surface pipelines and gates until they are qualified;

[0007] S3: perforating the target layer;

[0008] S4: Start the main fracturing operation to form artificial fractures to connect the lateral oil layers;

[0009] S5: Complete the fracturing operation of the remaining sections of the target horizontal well section by section;

[0010] S6: After the construction of all the target layers is completed, the well is shut down and flowback is carried out according to the design requirements.

[0011] Furthermore, in step S3, the target layer section is perforated. When the target layer section is drilled into a fracturing reformation section of mudstone and a laterally developed oil layer, a method for selecting a perforation position includes:

[0012] When the target layer is mudstone, perforate at the location with lower GR value and better cementing quality in the horizontal section where fracturing is needed;

[0013] The GR value is preferably at the minimum value, and the cementing quality should be preferably at the position of "excellent" or "qualified".

[0014] Furthermore, when the target layer encounters a mudstone reservoir and an adjacent oil layer is developed on one side, directional perforation is used:

[0015] The perforation direction is the direction of oil layer development. The right side uses three phase perforations of 30°, 90°, and 150°, while the left side uses three phase perforations of 210°, 270°, and 330°.

[0016] Furthermore, when the target layer encounters a mudstone reservoir and oil layers are developed on both adjacent sides, directional perforation on both sides in the horizontal direction is adopted;

[0017] The perforation directions are left and right; the phase angles are 60°, 120°, 240°, and 300°.

[0018] Furthermore, the step S3 requires a method for strictly controlling the number of fractures in a section according to the horizontal distance between the wellbore and the oil layer:

[0019] First, the corresponding geological and mechanical models of the target well are established. When drilling into a mudstone reservoir with oil layers on both sides, simulation software such as kinetiX or Gohfer is used to simulate the effective extension distance of the fractures when there are different numbers of fractures in the section under certain construction displacement and construction scale conditions, to ensure that the fractures can effectively communicate with the oil layers.

[0020] Furthermore, to ensure that the fractures can communicate effectively with the oil layer, for tight sandstone, the relationship between the distance between the oil layer and the wellbore perforation position and the number of clusters in each section is:

[0021] When the distance between the oil layer and the wellbore perforation position reaches 250 meters or more, one cluster of perforations is perforated in each section;

[0022] When the distance between the oil layer and the wellbore perforation position is 150-250 meters, the number of clusters per section is 1-2;

[0023] When the distance between the oil layer and the wellbore perforation position is less than 150 meters, the number of clusters in each section is 1-3.

[0024] Furthermore, the method of performing main fracturing construction in step S4 to form artificial fractures to communicate with lateral oil layers includes:

[0025] 21. Pump in the pre-fluid, preferably a high viscosity liquid as the pre-fluid of the fracturing fluid;

[0026] 22. Pump in the sand-carrying fluid and add the degradable fiber while adding the proppant;

[0027] 23. Pump in displacement fluid to complete the main fracturing construction of the target layer.

[0028] Furthermore, the preferred high-viscosity liquid is guar fracturing fluid or high-viscosity slick water.

[0029] Furthermore, the displacement of the pre-fluid is selected as follows: the displacement of the pre-fluid is increased as much as possible under the conditions of considering the well spacing and the maximum allowable construction pressure of the casing steel grade:

[0030] First, the displacement of the fracturing operation should be increased to avoid penetrating adjacent wells;

[0031] Second, construction should be carried out at the maximum displacement under the highest construction pressure allowed by the casing steel grade.

[0032] Furthermore, the concentration of the added degradable fiber is 0.1-0.2% of the concentration of the added proppant.

[0033] Compared with the above background technology, the present invention has the following beneficial effects:

[0034] The fracturing process method for a horizontal well to penetrate mudstone and communicate with an oil layer laterally, by optimizing the number of clusters in the segment, the perforation direction, the liquid viscosity and the injection of degradable fibers in the horizontal well when the horizontal well encounters a mudstone segment and the oil layer is developed laterally, ensures that the formed artificial fractures can connect the wellbore of the horizontal well with the oil layer, and realizes the effective use of the lateral oil layer. According to the distance between the wellbore and the lateral oil layer, the number of fractures in the segment is reasonably optimized to ensure the fracture extension distance; according to the position relationship between the lateral oil layer and the wellbore, the perforation direction is optimized to promote the fracture to extend toward the oil layer; high viscosity fracturing fluid is preferably used to improve the liquid efficiency, increase the fracture extension distance and the proppant carrying distance; and degradable fibers are used for injection throughout the process to reduce the embedding and sedimentation of the proppant in the cracks of the mudstone reservoir, and ensure the formation of an effective oil flow channel between the wellbore and the oil layer. Compared with the previous sandstone segment fracturing process, the present invention avoids the inability of the mudstone segment fracturing to communicate effectively with the oil layer or to form effective support after communication, ensures the long-term effectiveness of the oil flow channel, and meets the production needs of the lateral oil layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a horizontal well trajectory and sand body development relationship diagram of Example A of the present invention;

[0036] Figure 2 This is a simulation diagram of fracture extension with different numbers of clusters in a horizontal well section A of the embodiment of the present invention;

[0037] Figure 3 Schematic diagram of westward directional perforation of a horizontal well A in Example of the present invention;

[0038] Figure 4This is the downhole microseismic monitoring result of horizontal well fracturing in Example A of the present invention;

[0039] Figure 5 This is a diagram of the oil-water tracer monitoring results after pressure reduction in each section of the horizontal well A in Example of the present invention. Specific implementation method:

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0041] The present invention discloses a fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer, comprising the following steps:

[0042] S1: Install the fracturing wellhead and connect the fracturing manifold and the train set;

[0043] S2: Test the surface pipelines and gates until they are qualified;

[0044] S3: perforating the target layer;

[0045] Perforate the target layer. When the target layer encounters a fracturing zone of mudstone or a laterally developed oil layer, the method for selecting the perforation position includes:

[0046] When mudstone is encountered in the target layer, perforation should be performed at the location with lower GR value and better cementing quality in the horizontal section that needs fracturing. The GR value should be at the minimum value, and the cementing quality should be at the position of "excellent" or "qualified".

[0047] When the target layer encounters a mudstone reservoir and an oil layer is developed on one side adjacent to it, directional perforation is used; the perforation direction is the direction of oil layer development, and three phase perforations of 30°, 90°, and 150° are used on the right side, and three phase perforations of 210°, 270°, and 330° are used on the left side.

[0048] When the target layer encounters a mudstone reservoir and oil layers are developed on both adjacent sides, directional perforation is used on both sides in the horizontal direction; the perforation directions are left and right; the phase angles are 60°, 120°, 240°, and 300°.

[0049] The method to strictly control the number of fractures in a section according to the horizontal distance between the wellbore and the oil layer is as follows:

[0050] First, the corresponding geological and mechanical models of the target well are established. When drilling into a mudstone reservoir with oil layers on both sides, simulation software such as kinetiX or Gohfer is used to simulate the effective extension distance of the cracks when there are different numbers of cracks in the section under certain construction displacement and construction scale conditions to ensure that the cracks can effectively communicate with the oil layers. Generally, the fewer the number of cracks in the section, the longer the effective extension distance of the cracks.

[0051] To ensure that the fractures can communicate effectively with the oil layer, for tight sandstone, the relationship between the distance between the oil layer and the wellbore perforation position and the number of clusters in each section is:

[0052] When the distance between the oil layer and the wellbore perforation position reaches 250 meters or more, one cluster of perforations is perforated in each section;

[0053] When the distance between the oil layer and the wellbore perforation position is 150-250 meters, the number of clusters per section is 1-2;

[0054] When the distance between the oil layer and the wellbore perforation position is less than 150 meters, the number of clusters in each section is 1-3.

[0055] S4: Start the main fracturing operation to form artificial fractures to communicate with the lateral oil layer. The specific method includes:

[0056] 1) Pump in a pre-fluid, preferably a high-viscosity liquid is a pre-fluid of a fracturing fluid; the preferred high-viscosity liquid is a guar fracturing fluid or a high-viscosity slick water.

[0057] The displacement of the pre-fluid is selected as follows: the displacement of the pre-fluid is increased as much as possible under the conditions of considering the well spacing and the maximum allowable construction pressure of the casing steel grade:

[0058] First, the displacement of the fracturing operation should be increased to avoid penetrating adjacent wells;

[0059] Second, the construction is carried out at the maximum displacement under the maximum construction pressure allowed by the casing steel grade. Taking the Fuyu tight oil reservoir in Daqing Oilfield as an example, if the casing steel grade is P110 and the wall thickness is 9.17 mm, the recommended construction displacement is 14-16 cubic meters per minute.

[0060] 2) Pump in the sand-carrying fluid, add the degradable fiber while adding the proppant; the concentration of the degradable fiber added is 0.1-0.2% of the concentration of the proppant added.

[0061] 3) Pump in displacement fluid to complete the main fracturing construction of the target layer.

[0062] S5: Complete the fracturing construction of the remaining sections of the target horizontal well section by section.

[0063] S6: After the construction of all the target layers is completed, the well is shut down and flowback is carried out according to the design requirements.

[0064] The following takes Well A, a new horizontal well in the periphery of Daqing, as an example to explain in detail the fracturing technology of horizontal wells that laterally penetrate mudstone and connect oil layers.

[0065] Example 1

[0066] Well A is a new horizontal well in the periphery of Daqing. Due to the poor reservoir properties, low permeability, and lack of natural fractures, large-scale fracturing transformation is required. The well was drilled at a depth of 2688-2874m and encountered a mudstone reservoir. However, geological analysis showed that an oil layer was developed on the west side of the wellbore, with a distance of 30-160m between the oil layer and the wellbore. The horizontal section of the well is 943m long. If the mudstone at 2688-2874m is not transformed, the actual length of the horizontal well will be only 757m, which will affect the post-fracturing production.

[0067] Well A uses a horizontal well to laterally penetrate the mudstone and connect the oil layer. The fracturing process includes the following steps:

[0068] Step 1: Install the fracturing wellhead and connect the fracturing manifold and the train.

[0069] Step 2: The surface pipeline and gate are tested at a pressure of 70MPa. The pipeline is qualified if there is no puncture, leakage or seepage.

[0070] Step 3: The horizontal well encountered a mudstone reservoir at 2688-2874 m. Geological interpretation showed that oil layers were developed on the west side. Figure 1 As shown in the figure, the distance between the wellbore trajectory and the western oil layer is 30-160m. The wellbore trajectory is designed according to the maximum distance of 160m between the wellbore and the oil layer. A numerical model of the extension of multiple clusters of fractures in the segment is established, and a numerical simulation of fracture extension is carried out. Figure 2 As shown in the figure, the fracture extension simulation results show that: 2 clusters of fractures in a segment can ensure that each fracture can communicate with the oil layer. For this reason, 2 clusters are designed in a single segment, and a total of 3 segments and 6 clusters are fracturing, with an average cluster spacing of about 30m. In the first segment, two locations with low GR values ​​and "excellent" cementing quality are selected for perforation, and directional perforation to the west is used, such as Figure 3 As shown, the perforation phase angles are 210°, 270°, and 330°.

[0071] Step 4: Perform the main fracturing operation on the first section. First, pump in the pre-fluid, using guar fracturing fluid. The casing steel grade of this well is P110 (9.17mm thickness), preferably 14m 3 / min displacement construction, during the construction process, the casing pressure of adjacent wells is monitored in real time to determine whether the adjacent wells are penetrated. Secondly, the sand-carrying fluid is pumped in, and the degradable fiber is added at the same time as the proppant. The concentration of the degradable fiber added is 0.1-0.2% of the proppant concentration. The addition of this concentration of degradable fiber and the proppant can improve the longitudinal laying capacity of the proppant and prevent excessive sedimentation. Finally, the displacement fluid is pumped in to complete the main fracturing construction of the first section.

[0072] Step 6: Complete the fracturing construction of the remaining sections of the target horizontal well section by section;

[0073] Step 7: After completing the construction, close the well and perform backflow according to the design requirements.

[0074] During the fracturing operation, the well carried out downhole microseismic crack morphology monitoring. The monitoring results are as follows: Figure 4 As shown in the dotted box in the figure (the dotted box in the figure corresponds to Figure 1 The monitoring results show that the cracks in the lateral penetration section of the mudstone mainly extend to the west, with a half-length of 240 m, which realizes the effective communication between the wellbore and the oil layer. At the same time, the tracer capacity monitoring was carried out after the well was pressurized. The monitoring results are as follows: Figure 5 As shown, the results also show that the mudstone lateral penetration section has oil production contribution, indicating that the fracture penetrates the mudstone and is effectively connected with the oil layer.

[0075] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Therefore, the content of the present invention is not limited to the examples listed, and any equivalent changes taken by ordinary technicians in the field of the present invention by reading the specification of the present invention to the technical solution of the present invention are all covered by the claims of the present invention.

Claims

1. A fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer, characterized in that: The following steps are involved: S1: Install the fracturing wellhead and connect the fracturing manifold and the train set; S2: Test the surface pipelines and gates until they are qualified; S3: perforating the target layer; S4: Start the main fracturing operation to form artificial fractures to connect the lateral oil layers; S5: Complete the fracturing operation of the remaining sections of the target horizontal well section by section; S6: After the construction of all the target layers is completed, the well is shut down and flowback is carried out according to the design requirements.

2. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 1, characterized in that: Step S3 is to perforate the target layer. When the target layer is drilled into a fracturing reformation section of mudstone or a lateral oil layer, a method for selecting a perforation position includes: When the target layer is mudstone, perforate at the location with lower GR value and better cementing quality in the horizontal section where fracturing is needed; The GR value is preferably at the minimum value, and the cementing quality should be preferably at the position of "excellent" or "qualified".

3. The fracturing process for horizontal wells to laterally penetrate mudstone and communicate with oil layers according to claim 2, characterized in that: When the target layer encounters a mudstone reservoir and an oil layer is developed on one side, directional perforation is used: The perforation direction is the direction of oil layer development. The right side uses three phase perforations of 30°, 90°, and 150°, while the left side uses three phase perforations of 210°, 270°, and 330°.

4. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 2, characterized in that: When the target layer encounters a mudstone reservoir and oil layers are developed on both sides of the adjacent layer, directional perforation on both sides in the horizontal direction is adopted; The perforation directions are left and right, and the phase angles are 60°, 120°, 240°, and 300°.

5. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 1 or 3, characterized in that: Step S3 requires a method to strictly control the number of fractures in a section according to the horizontal distance between the wellbore and the oil layer: First, the corresponding geological and mechanical models of the target well are established. When drilling into a mudstone reservoir with oil layers on both sides, the effective extension distance of the fractures with different numbers of fractures in the section under certain construction displacement and construction scale conditions is simulated by using kinetiX or Gohfer simulation software to ensure that the fractures can effectively communicate with the oil layers.

6. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 5, characterized in that: To ensure that the fractures can communicate effectively with the oil layer, for tight sandstone, the relationship between the distance between the oil layer and the wellbore perforation position and the number of clusters in each section is: When the distance between the oil layer and the wellbore perforation position reaches 250 meters or more, one cluster is perforated in each section; When the distance between the oil layer and the wellbore perforation position is 150-250 meters, the number of clusters per section is 1-2; When the distance between the oil layer and the wellbore perforation position is less than 150 meters, the number of clusters in each section is 1-3.

7. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 1, characterized in that: Step S4 is to perform main fracturing construction to form artificial fractures to communicate with lateral oil layers, which specifically includes: 1) Pump in the pre-fluid, preferably a high viscosity liquid as the pre-fluid of the fracturing fluid; 2) Pump in the sand-carrying fluid and add the degradable fiber while adding the proppant; 3) Pump in displacement fluid to complete the main fracturing construction of the target layer.

8. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 7, characterized in that: The preferred high viscosity fluid is guar fracturing fluid or high viscosity slick water.

9. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 7, characterized in that: The displacement of the pre-fluid is selected as follows: the displacement of the pre-fluid is increased as much as possible under the conditions of considering the well spacing and the maximum allowable construction pressure of the casing steel grade: First, the displacement of the fracturing operation should be increased to avoid penetrating adjacent wells; Second, construction should be carried out at the maximum displacement under the highest construction pressure allowed by the casing steel grade.

10. The fracturing process for a horizontal well to laterally penetrate mudstone and communicate with an oil layer according to claim 7, characterized in that: The concentration of the added degradable fiber is 0.1-0.2% of the concentration of the added proppant.

Images