Shale gas horizontal well small well spacing development fracturing negative interference prevention and control method

Abstract

The invention relates to the field of shale gas exploitation, and discloses a shale gas horizontal well small well spacing development fracturing negative interference prevention and control method, which comprises the following steps: firstly, if the formation pressure of an adjacent well is smaller than the formation pressure of a fractured well, pumping gas or liquid into the adjacent well for pressure supplementation, sealing and closing the adjacent well after pressure supplementation, and then sealing and closing the adjacent well; horizontal well arrangement and fracturing perforation are carried out on a to-be-fractured well, when the pressure of adjacent wells continuously rises, the construction displacement of the fractured well is reduced, a propping agent in the fractured well is replaced, a temporary plugging agent is added, and when the pressure of the adjacent wells does not rise any more, the construction displacement of the fractured well is gradually recovered; and finally, after fracturing of the fractured well is completed, shale gas recovery is conducted on the fractured well, when the pressure in the fractured well is reduced to be equivalent to that of the adjacent wells, recovery is conducted on one or more of the adjacent wells, and the shale gas recovery efficiency is improved through prevention and control over fracturing negative interference of the small well spacing.

Description

Technical Field

[0001] The present invention relates to the field of shale gas exploitation, and in particular to a method for preventing and controlling negative interference of fracturing in the development of shale gas horizontal wells with small well spacing. Background Art

[0002] In the development of shale gas, in order to improve the recovery of gas reservoirs, horizontal well completion in the target layer and small well spacing are used for development. The well distance of shale gas fields in a certain area is maintained at about 200m. Although small well spacing development helps to fully utilize the reserves between wells and can improve the gas recovery rate in the well layout area, it will inevitably be subject to more serious fracturing interference. The negative impact of fracturing interference on the efficient development of well groups has the following aspects: First, due to the high pressure in the fracture of the fracturing well, once the hydraulic fracture communicates with the fracture of the adjacent production well, a large amount of fracturing fluid will enter the fracturing fracture of the production well, and the liquid used to form new fractures in the fracturing well will be greatly reduced, affecting the transformation effect of the fracturing well; second, a large amount of fracturing fluid has entered the fracture of the original production well, which will cause a significant decrease in gas production and a significant increase in water production in the production well. Therefore, how to effectively avoid negative fracturing interference has become a difficult problem that needs to be solved in the development of shale gas horizontal wells with small well spacing. Summary of the invention

[0003] The present invention aims to provide a method for preventing and controlling negative interference of fracturing in the development of shale gas horizontal wells with small well spacing, so as to solve the problem of negative interference of fracturing in the development of shale gas horizontal wells with small well spacing.

[0004] To achieve the above object, the present invention adopts the following technical solution: a method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing, the steps of which are as follows: Step 1: Formation pressure monitoring: Obtain the formation pressure of the fracturing well and adjacent wells, and determine whether the formation pressure of the adjacent well is less than the formation pressure of the fracturing well; Step 2: Replenishing the pressure in the low-pressure area: If the formation pressure of the adjacent well is lower than the formation pressure of the fracturing well, pump gas or liquid into the adjacent well to replenish the pressure, so that the formation pressure of the adjacent well is greater than or equal to the formation pressure of the fracturing well, and seal and close the adjacent well after replenishing the pressure; if the formation pressure of the adjacent old well is higher than the formation pressure of the fracturing well, directly seal and close the adjacent well; Step 3: Keep the adjacent wells sealed and closed, arrange horizontal wells and fracturing perforations for the well to be fractured, the horizontal well of the well to be fractured and the horizontal well of the adjacent well are staggered, and the perforation cluster positions on the two horizontal wells are staggered; Step 4: When the fracturing well communicates with the adjacent well, immediately reduce the construction displacement of the fracturing well, replace the proppant in the fracturing well, and add temporary fracturing plugging agent. When the pressure of the adjacent well stops rising, gradually restore the construction displacement of the fracturing well. When the pressure of the adjacent well continues to rise, end the construction of the fracturing well; Step 5: After the fracturing is completed, shale gas is quickly recovered from the fracturing well. When the pressure in the fracturing well drops to the same level as that of the adjacent wells, one or more of the adjacent wells are resumed.

[0005] The principles and advantages of this solution are: During the fracturing process, the pressure changes of adjacent wells will be an important basis for judging whether the fractures of the fracturing wells are connected with the well itself. Electronic pressure sensing equipment is installed at the adjacent wellheads around the well to be fracturing, and the signal is transmitted to the fracturing well site, so that the fracturing site commander can grasp the pressure changes of adjacent wells in real time. By judging the pressure changes of adjacent wells, it can be judged whether the shale gas well being fractured is connected with the adjacent wells.

[0006] In order to avoid the current fracturing wells from communicating with adjacent wells, in terms of perforation location selection, the perforation cluster location selection of the well to be fractured should be staggered with the perforation cluster location of the adjacent wells. In addition, if natural fractures are developed between the well to be fractured and the old well, the fracturing construction scale should be reduced and the fracturing construction displacement should be controlled. Through software simulation, the half-length of the fracturing crack in the natural fracture development section should be controlled at 70% of the non-natural fracture development section, and the maximum construction displacement in the natural fracture development section is 80% of the non-natural fracture development section.

[0007] When communication with adjacent wells occurs, during the fracturing process, the pressure changes of adjacent wells are monitored in real time, and whether communication occurs is determined by the degree of pressure increase of adjacent wells. Taking a 200m well spacing as an example, when a fracturing well is fracturing under this condition, if the pressure increase rate of the adjacent well exceeds 0.15MPa / min, it is considered that communication has occurred. At this time, the construction displacement is reduced, the proppant in the wellbore is immediately replaced, and a temporary fracturing plugging agent is added at the same time to force the hydraulic fracture to turn and curb the momentum of fracture communication. After the temporary plugging is completed, if the pressure of the adjacent well no longer rises, the fracturing construction will continue; if the pressure of the adjacent well still rises rapidly, it means that the temporary plugging and diversion has not played a good control role, and the pump should be stopped immediately to end the fracturing construction of this section.

[0008] After the current fracturing well is completed, shale gas is quickly recovered from the fracturing well. When the pressure in the fracturing well drops to the same level as that of the adjacent wells, one or more of the adjacent wells are resumed for production.

[0009] This method improves the scientific treatment of communication between adjacent wells during shale gas extraction by preventing and fracturing the shale gas collection process at small well spacing, thereby improving gas extraction efficiency.

[0010] Preferably, before carrying out the fracturing construction, a small fracturing test is used to obtain the formation pressure of the fracturing well, and a pressure gauge is placed downhole to obtain the formation pressure of the adjacent wells of the fracturing well. By obtaining the bottom pressure of the fracturing well itself and the surrounding area, the pressure changes of the fracturing well and the adjacent wells can be grasped in real time, providing a basis for judging whether there is communication between the fracturing well and the adjacent wells in the later stage.

[0011] Preferably, in step 2, the adjacent wells are pressurized by gas injection. The adjacent wells are pressurized so that a pressure balance is formed in the fracturing wells during the fracturing process, thereby reducing the transmission of communication.

[0012] Preferably, in step 2, the gas used to supplement the pressure of the adjacent wells is natural gas or nitrogen, and the liquid used to supplement the pressure is clean water or fracturing fluid. Whether the pressure supplement method is gas supplement or liquid supplement should be selected according to the on-site conditions.

[0013] Preferably, between step 2 and step 3, it also includes detecting the presence of a natural fracture development section between the well to be fractured and the old well. If a natural fracture development section exists, the half-length of the fractured crack in the natural fracture development section is controlled to be 70% of that in the non-natural fracture development section, and the maximum construction displacement of the natural fracture development section is 80% of that in the non-natural fracture development section. By detecting the natural fracture development section, the fracturing gas production process can prevent the natural fracture development section in advance, avoiding the communication of adjacent wells caused by excessive construction displacement in the natural fracture development section.

[0014] Preferably, in step 4, the distance between adjacent wells is less than or equal to 200 meters, and the method for judging whether the fracturing well communicates with the adjacent well is: installing a pressure sensor at the wellhead of the adjacent well, and observing the pressure value of the pressure sensor, if the pressure rise rate of the adjacent well exceeds 0.15MPa / min, it is considered that the fracturing well communicates with the adjacent well. Through actual measurement, when the rise rate exceeds 0.15MPa / min, the adjacent wells must communicate.

[0015] Preferably, the temporary plugging agent used is degradable particle gel DPGs. DPGs has good adaptability and meets the requirements of diverting fracturing in hydraulic fractures.

[0016] Preferably, during the process of resuming production of adjacent wells, if the wellbore is flooded and drainage is difficult, a foam rod is added to the wellbore, and after standing for reaction, the adjacent well is restored to production by gas lift drainage. After the foam rod contacts and dissolves with the accumulated water in the wellbore, a large amount of low-density water-containing foam is formed by the stirring of the natural gas flow, which changes the gas-water flow state in the wellbore, reduces liquid "slippage", and improves the vertical lifting capacity and liquid carrying capacity of the gas flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the positional relationship between the fracturing well and adjacent wells.

[0018] Figure 2 Schematic diagram of the staggered fracturing perforation settings between adjacent wells and the fracturing process in four time periods. DETAILED DESCRIPTION

[0019] The following is further described in detail through specific implementation methods: As attached Figure 1 As shown, taking the shale gas exploitation with horizontal wells with small well spacing as an example, where the distance between adjacent wells is less than 200 meters, the shale gas well to be exploited in the gas production area A is called fracturing well 1, and the fracturing well adjacent to the fracturing well and which has already produced gas is called adjacent well 2.

[0020] The methods for opening new fracturing wells for the above-mentioned gas production wells to prevent negative interference from fracturing include the following: Step 1: Formation pressure monitoring: Use a small-scale fracturing test to obtain the formation pressure of fracturing well 1, obtain the formation pressure of adjacent well 2 by inserting a pressure gauge downhole, and draw a formation pressure distribution map around the fracturing well; determine whether the formation pressure of adjacent well 2 is less than the formation pressure of fracturing well 1.

[0021] Step 2: Replenish pressure in low-pressure areas: Based on the formation pressure monitoring results, the formation pressure difference between the fracturing well and the adjacent well is determined. If the difference reaches 0.1 MPa, gas or liquid is pumped into the adjacent well to replenish pressure, so that the formation pressure of the adjacent well is greater than or equal to the formation pressure of the fracturing well. After the pressure is replenished, the adjacent well is sealed and closed; if the formation pressure of the adjacent old well is greater than the formation pressure of the fracturing well, the adjacent well is directly sealed and closed. Considering the recovery of production after drainage and gas production after fracturing, this embodiment adopts gas injection to replenish pressure.

[0022] Keep the adjacent well sealed and closed, install an electronic pressure sensor 3 on the adjacent well 2, transmit the signal to the fracturing well site, and grasp the pressure changes of the adjacent well in real time.

[0023] like Figure 2 As shown, step three, in the arrangement of the horizontal well 4 and the fracturing perforations 5 in the fracturing well, the horizontal well 4 of the fracturing well and the horizontal well of the adjacent well are staggered, and the positions of the fracturing perforations 5 on the two horizontal wells are staggered; thus, the fracture connection caused by the advance of a single cluster of fractures is reduced.

[0024] Through understanding of geological data, if there are natural fractures between the well to be fractured and the adjacent wells, the scale of fracturing construction should be reduced and the fracturing construction displacement should be controlled. The half-length of the fracturing crack in the natural fracture development section should be controlled at 70% of the non-natural fracture development section, and the maximum construction displacement in the natural fracture development section is 80% of the non-natural fracture development section.

[0025] Step 4: During the fracturing process, the pressure changes of adjacent wells are monitored in real time, and the degree of pressure increase of adjacent wells is used to determine whether communication has occurred. In this embodiment, when the fracturing well is fracturing under the condition of a well spacing of 200 meters, if the pressure increase rate of the adjacent well exceeds 0.15 MPa / min, it is considered that communication has occurred.

[0026] When the fracturing well is connected with the adjacent well, the construction displacement of the fracturing well is immediately reduced, the proppant in the fracturing well is replaced, and temporary fracturing plugging agent is added. When the pressure of the adjacent well no longer increases, the construction displacement of the fracturing well is gradually restored.

[0027] Because the bottom pressure of the fracturing well after fracturing is higher than that of adjacent wells, if gas is not produced in time after fracturing, the high-pressure fluid in the fracturing well may still slowly spread to adjacent wells. Therefore, after the fracturing well is completed, it is quickly put into production according to the process of "blowing-drilling plug-lowering oil pipe completion-production". If the fracturing well cannot rely on its own energy to remove shale gas, gas lift drainage is used in the fracturing well to produce gas.

[0028] Step 5. When the pressure in the fracturing well drops to the same level as that of the adjacent wells, one or more of the adjacent wells will be resumed. If the adjacent wells are flooded or have difficulty draining fluid during the resumption of production, add a foam rod into the wellbore. After standing for reaction, use gas lift to drain fluid to resume production.

[0029] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing, characterized by: The steps include: Step 1: Formation pressure monitoring: Obtain the formation pressure of the fracturing well and adjacent wells, and determine whether the formation pressure of the adjacent well is less than the formation pressure of the fracturing well; Step 2: Replenishing the pressure in the low-pressure area: If the formation pressure of the adjacent well is lower than the formation pressure of the fracturing well, pump gas or liquid into the adjacent well to replenish the pressure, so that the formation pressure of the adjacent well is greater than or equal to the formation pressure of the fracturing well, and seal and close the adjacent well after replenishing the pressure; if the formation pressure of the adjacent old well is higher than the formation pressure of the fracturing well, directly seal and close the adjacent well; Step 3: Arrange horizontal wells and fracturing perforations: Keep the adjacent wells sealed and closed, arrange horizontal wells and fracturing perforations for the wells to be fractured, the horizontal wells of the wells to be fractured and the horizontal wells of the adjacent wells are staggered, and the perforation cluster positions on the two horizontal wells are staggered; Step 4: Handling of the communication between the fracturing well and the adjacent wells: When the fracturing well communicates with the adjacent wells, immediately reduce the construction displacement of the fracturing well, replace the proppant in the fracturing well, and add temporary fracturing plugging agent. When the pressure of the adjacent wells stops rising, gradually restore the construction displacement of the fracturing well. When the pressure of the adjacent wells continues to rise, end the construction of the fracturing well; Step 5: Fracturing and gas production: After the fracturing of the fracturing well is completed, shale gas is quickly recovered from the fracturing well. When the pressure in the fracturing well drops to the same level as that of the adjacent wells, one or more of the adjacent wells are resumed for production.

2. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 1, characterized in that: Before carrying out fracturing construction, a small-scale fracturing test is used to obtain the formation pressure of the fracturing well, and at the same time, a pressure gauge is lowered downhole to obtain the formation pressure of the adjacent wells of the fracturing well.

3. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 2, characterized in that: In step 2, gas injection is used to supplement the pressure of adjacent wells.

4. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 3, characterized in that: In step 2, the gas used to supplement the pressure of the adjacent wells is natural gas or nitrogen, and the liquid used to supplement the pressure is clean water or fracturing fluid.

5. The method for preventing and controlling negative interference of fracturing in shale gas horizontal well development with small well spacing according to claim 4, characterized in that: Between step 2 and step 3, it also includes detecting whether there is a natural fracture development section between the well to be fractured and the old well. If there is a natural fracture development section, the half-length of the fracturing crack in the natural fracture development section is controlled to be 70% of that in the non-natural fracture development section, and the maximum construction displacement of the natural fracture development section is 80% of that in the non-natural fracture development section.

6. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 5, characterized in that: In step 4, the distance between adjacent wells is less than or equal to 200 meters. The method for determining whether the fracturing well communicates with the adjacent wells is as follows: a pressure sensor is installed at the wellhead of the adjacent well, and the pressure value of the pressure sensor is observed. If the pressure rise rate of the adjacent well exceeds 0.15 MPa / min, it is considered that the fracturing well communicates with the adjacent well.

7. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 6, characterized in that: The temporary plugging agent used is degradable particle gel DPGs.

8. The method for preventing and controlling negative interference of fracturing in shale gas horizontal wells with small well spacing according to claim 7, characterized in that: During the process of resuming production of adjacent wells, if the wellbore is flooded and drainage is difficult, add bubble rods into the wellbore. After standing for reaction, gas lift drainage is used to resume production of the adjacent wells.

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