A soft treatment method for shale oil and gas horizontal well fracturing sand plug

Abstract

This invention belongs to the field of oilfield production engineering technology, specifically relating to a soft treatment method for sand blockage in shale oil and gas horizontal well fracturing. This invention solves the problem of sand blockage and overpressure shutdown of the fracturing pump truck during the fracturing process of shale oil and gas horizontal wells. The invention includes the following steps: 1) Timely control of the blowout using an 8-12mm nozzle through the choke manifold until sand is discharged from the outlet; 2) Using slickwater at a low flow rate to displace the blockage until the pressure stabilizes, establishing a small flow rate; 3) Controlling the pressure to increase the flow rate to the maximum fracturing flow rate; 4) Alternating use of high-viscosity gel slugs and slickwater until the pressure drops steadily or decreases, while simultaneously displacing sand from the wellbore; 5) Using low-sand-ratio slugs to grind and treat the fracture opening, and gradually increasing the flow rate according to the pressure drop to resume continuous sand addition. This invention has the advantages of reducing time and costs, successfully unblocking the blockage, and quickly resuming fracturing operations without using coiled tubing for sand flushing.

Description

Technical Field

[0001] This invention belongs to the field of oilfield production engineering technology, specifically relating to a soft treatment method for sand plugging in horizontal shale oil and gas wells after fracturing. Background Technology

[0002] Currently, sluice-type or continuous sand addition is used in horizontal well fracturing operations for shale oil and gas. This method is prone to causing sand blockage due to drastic pressure changes. Several factors contribute to this: First, the reservoir characteristics are highly sensitive to the sand ratio, and the ratio may not be adjusted in time during fracturing. Second, equipment malfunctions during sand addition, such as those involving sand mixing trucks or pump trucks, can reduce the discharge rate, leading to high sand concentrations and sand blockage. Third, severe leaks in surface manifolds and pipelines during fracturing can prevent complete displacement, further contributing to sand blockage. Ultimately, sand blockage can cause casing deformation and termination of fracturing operations. Using continuous oil flushing increases operating costs and delays the main fracturing process. Summary of the Invention

[0003] This invention provides a soft treatment method for sand blockage in shale oil and gas horizontal well fracturing. This invention addresses the sand blockage phenomenon that occurs in shale oil and gas horizontal well fracturing by taking a series of measures to unblock the blockage and achieve the goal of quickly resuming construction.

[0004] The technical solution of this invention is: a soft treatment method for sand plugging in fracturing of shale oil and gas horizontal wells, comprising the following steps:

[0005] Step 1: Promptly control the release of the spray by using an 8-12mm nozzle through the throttling manifold until sand is discharged from the outlet;

[0006] Step 2: Use slickwater with a low displacement to replace the extruder until the pressure is stable, and establish a small displacement.

[0007] Step 3: Control the pressure and increase the displacement to the maximum fracturing displacement.

[0008] Step 4: Use a high-viscosity gel slug and slickwater alternately until the pressure drops steadily or decreases, while simultaneously displacing the wellbore until there is no sand inside.

[0009] Step 5: Use a low-abrasion-ratio slug to grind the joint, and gradually increase the discharge rate according to the pressure drop to resume continuous sand feeding.

[0010] Furthermore, the specific procedure of step 1 is as follows: under the premise of ensuring well control safety, the pressure difference between the formation and the wellbore is used to release the fluid through the perforation hole. During the release process, the fluid in the formation carries a certain amount of proppant back into the wellbore until it returns to the wellhead. If the proppant visible at the wellhead is sand plugged, formation proppant is injected. Finally, it is determined whether the same pressure system is formed between the wellbore and the formation.

[0011] Furthermore, the specific procedure for step 2 is as follows: After the formation is opened, a large amount of proppant will settle in the horizontal wellbore. Then, low-friction slickwater is injected at a low rate, generally 0.6-0.8 cubic meters per minute, until there is an injection volume in the formation and the construction pressure is stable.

[0012] Furthermore, in step 3, the specific method is as follows: during the process of gradually increasing the discharge rate from a low rate, in order to avoid the proppant in the wellbore being pushed to the joint opening and causing sand blockage again, the difference in discharge rate under controlled pressure should not exceed 0.5 cubic meters per minute.

[0013] Furthermore, the specific implementation of step 4 is as follows: after establishing the large-scale construction, a high-viscosity gel plug with good sand-carrying capacity is used to carry sand into the formation, and then a large-volume slickwater is used to clean the wellbore. Finally, the construction discharge required by the design is established, while simultaneously meeting the requirements of the next stage of pumping bridge plug perforation construction.

[0014] Furthermore, the specific implementation of step 5 is as follows: Although a large-volume construction was established in the early stage, the crack width near the borehole and in the near-well zone is small, making it unsuitable for direct sand addition construction with a medium-high sand ratio. Instead, a low-sand-ratio slug should be used to grind and treat the crack opening, and the discharge rate should be gradually increased according to the pressure drop to resume continuous sand addition construction.

[0015] The advantages of this invention are:

[0016] The method of this invention is reasonably designed, simple in process, convenient to operate, safe and reliable, and has high processing efficiency. It can be applied to all shale oil and gas horizontal well fracturing and sand plugging removal technologies. This invention is conducive to the rapid resumption of fracturing operations, reducing downtime, and avoiding the use of large amounts of fluid and the investment of a lot of manpower, material resources, equipment, raw materials, well tools, etc. in continuous tubing sand flushing operations, which would increase the cost of single-well construction and delay the overall construction progress. Attached Figure Description

[0017] Figure 1 This is the unblocking curve of the 7th segment of Well H19-3 in Example 1; Figure 2 The unblocking curve of the 32nd segment of well Ning 209H36-3 in Example 2. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments; a soft treatment method for sand plugging in fracturing of shale oil and gas horizontal wells includes the following steps:

[0019] Step 1: Promptly control the release of the spray by using an 8-12mm nozzle through the throttling manifold until sand is discharged from the outlet;

[0020] Step 2: Use slickwater with a low displacement to replace the extruder until the pressure is stable, and establish a small displacement.

[0021] Step 3: Control the pressure and increase the displacement to the maximum fracturing displacement.

[0022] Step 4: Use a high-viscosity gel slug and slickwater alternately until the pressure drops steadily or decreases, while simultaneously displacing the wellbore until there is no sand inside.

[0023] Step 5: Use a low-abrasion-ratio slug to grind the joint, and gradually increase the discharge rate according to the pressure drop to resume continuous sand feeding.

[0024] The specific procedure for step 1 is as follows: Under the premise of ensuring well control safety, the pressure difference between the formation and the wellbore is used to release the fluid through the perforation hole. During the release process, the fluid in the formation carries a certain amount of proppant back into the wellbore until it returns to the wellhead. If the proppant visible at the wellhead is sand plugged, formation proppant is injected. Finally, it is determined whether the same pressure system is formed between the wellbore and the formation.

[0025] The specific procedure for step 2 is as follows: After the formation is opened, a large amount of proppant will settle in the horizontal wellbore. Then, low-friction slickwater is injected at a low rate, generally 0.6-0.8 cubic meters per minute, until there is an injection volume in the formation and the construction pressure is stable.

[0026] The specific procedure for step 3 is as follows: In order to avoid the proppant in the wellbore being pushed to the joint opening and causing sand blockage again during the process of gradually increasing the discharge rate from a low discharge rate, the difference in discharge rate under controlled pressure should not exceed 0.5 cubic meters per minute.

[0027] The specific procedure for step 4 is as follows: After establishing the large-scale construction, a high-viscosity gel plug with good sand-carrying capacity is used to carry sand into the formation, and then a large-volume slickwater is used to clean the wellbore. Finally, the construction discharge required by the design is established, while also meeting the requirements for the next stage of pumping bridge plug perforation construction.

[0028] The specific procedure for step 5 is as follows: Although a large-volume construction was established in the early stage, the crack width near the borehole and in the near-well zone is small, making it unsuitable for direct sand addition construction with a medium-high sand ratio. Instead, a low-sand-ratio slug should be used to grind the crack opening, and the discharge rate should be gradually increased according to the pressure drop to resume continuous sand addition construction.

[0029] Example 1:

[0030] During the seventh stage fracturing operation of the Changning H19-3 shale gas well, the ceramsite sand concentration was 120 kg / m³ during the sand addition process. 3 The pressure suddenly rose to 85 MPa, causing sand blockage. The pump was immediately stopped at a pressure of 50 MPa. While ensuring well control safety, the following measures were taken promptly according to the unblocking procedure:

[0031] First, the gas testing personnel controlled the venting by using a 10mm nozzle through the choke manifold. The wellhead pressure changes were observed and recorded in the data recovery room. At the same time, a special person was assigned to observe the dynamics of the outlet return fluid and proppant. Sand was seen at the outlet after about 10 minutes. Subsequently, the sand concentration increased and a large amount of proppant was returned to the wellhead, indicating that the formation and the wellbore are under the same pressure system.

[0032] Secondly, after controlling the flow of water for one hour, test extrusion using a low-volume slickwater flow, typically 0.7-1.6 m³ / h. 3 / min, displacement is adjusted according to pressure;

[0033] Third, due to the large amount of sediment in the wellbore, the pressure rose to 90MPa during the low-displacement process, and the first unblocking attempt failed.

[0034] Fourth, use a 10mm nozzle again to control the release spray, and after 10 minutes, shut off the release spray process and continue using a 0.9mm nozzle. 3 Initially test extrusion at a small displacement of 8m³ / min, gradually increase the displacement while controlling the pressure. 3 A speed of / min indicates successful unblocking;

[0035] Fifth, replace the high-viscosity gel slug with a high-viscosity one-way valve and increase the displacement to 11.2 m³ / s based on the pressure. 3 The / min sand removal rate indicates that the wellbore cleaning is complete, and the subsequent pumping of the bridge plug is normal. This invention is safe and reliable, and can effectively improve the efficiency of handling complex fracturing sand blockage conditions.

[0036] Example 2:

[0037] The 32nd stage of fracturing in the Ning 209H36-3 shale gas well was carried out, with a ceramsite sand concentration of 180 kg / m³ during the sand addition process. 3 The pressure suddenly increased, and the sand was stopped to replace 35m. 3 After the slickwater flow reaches an overpressure of 96MPa, sand blockage occurs. The pump is stopped at a pressure of 36MPa. Under the premise of ensuring well control safety, the following measures should be taken promptly according to the unblocking procedure:

[0038] First, the testing personnel controlled the venting using a 12mm nozzle through the choke manifold. Changes in wellhead pressure were observed and recorded in the data recovery room. Simultaneously, a dedicated person observed the dynamics of the outlet flowback fluid and proppant. Sand was observed at the outlet after approximately 40 minutes, and the outlet fluid volume increased significantly after 49 minutes, indicating nozzle damage. The venting process was immediately shut down, and the well was restarted using a 0.6-1.7m... 3 During the variable displacement test, the pressure dropped suddenly, and later the pressure became too high, and the unblocking was unsuccessful.

[0039] Second, the nozzle was replaced with an 8mm nozzle to control the blowout. A small amount of sand was seen at the outlet after 25 minutes, and a large amount of sand was seen after 53 minutes. The sand concentration increased afterward, and a large amount of proppant was returned to the wellhead, indicating that the formation and the wellbore are under the same pressure system.

[0040] Third, the spraying process should be shut off. After 73 minutes of spraying, a slickwater system should be used, with a typical discharge rate of 0.76-5.9 m³. 3 / min, displacement is adjusted according to pressure; 0.76m 3 Initially test extrusion at a small displacement of 5.9 m³ / min, gradually increase the displacement while controlling the pressure. 3 A speed of / min indicates successful unblocking;

[0041] Fourth, replace the high-viscosity gel slug and increase the discharge rate to 14m³ according to the pressure. 3 The / min sand removal indicates that the wellbore cleaning is complete; this invention is safe and reliable, and can effectively improve the timeliness of handling complex fracturing sand blockage conditions.

Claims

1. A method for soft treatment of sand plugging in fracturing of shale oil and gas horizontal wells, characterized in that: Includes the following steps: Step 1: Promptly control the release of the spray by using an 8-12mm nozzle through the throttling manifold until sand is discharged from the outlet; Step 2: Use slickwater with a low displacement to replace the extruder until the pressure is stable, and establish a small displacement. Step 3: Control the pressure and increase the displacement to the maximum fracturing displacement. Step 4: Use a high-viscosity gel slug and slickwater alternately until the pressure drops steadily or decreases, while simultaneously displacing the wellbore until there is no sand inside. Step 5: Use a low-abrasion-ratio slug to grind the joint, and gradually increase the discharge rate according to the pressure drop to resume continuous sand feeding.

2. The soft treatment method for sand plugging in fracturing of shale oil and gas horizontal wells according to claim 1, characterized in that: The specific procedure for step 1 is as follows: Under the premise of ensuring well control safety, the pressure difference between the formation and the wellbore is used to release the fluid through the perforation hole. During the release process, the fluid in the formation carries a certain amount of proppant back into the wellbore until it returns to the wellhead. If the proppant visible at the wellhead is sand plugged, formation proppant is injected. Finally, it is determined whether the same pressure system is formed between the wellbore and the formation.

3. The soft treatment method for sand plugging in fracturing shale oil and gas horizontal wells according to claim 1, characterized in that: The specific procedure for step 2 is as follows: After the formation is opened, a large amount of proppant will settle in the horizontal wellbore. Then, low-friction slickwater is injected at a low rate of 0.6-0.8 cubic meters per minute until there is an injection volume in the formation and the construction pressure is stable.

4. The soft treatment method for sand plugging in fracturing shale oil and gas horizontal wells according to claim 1, characterized in that: The specific procedure for step 3 is as follows: during the process of gradually increasing the displacement from a low displacement, the difference in displacement increment under controlled pressure should not exceed 0.5 cubic meters per minute.

5. The soft treatment method for sand plugging in fracturing shale oil and gas horizontal wells according to claim 1, characterized in that: The specific procedure for step 4 is as follows: After establishing the large-scale construction, a high-viscosity gel plug with good sand-carrying capacity is used to carry sand into the formation, and then a large-volume slickwater is used to clean the wellbore. Finally, the construction discharge required by the design is established, while also meeting the requirements for the next stage of pumping bridge plug perforation construction.

6. The soft treatment method for sand plugging in fracturing shale oil and gas horizontal wells according to claim 1, characterized in that: The specific procedure for step 5 is as follows: use a low-sand ratio slug to grind the joint, gradually increase the discharge rate according to the pressure drop, and resume continuous sand addition.

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