A method for plugging a safe abandoned well

Abstract

The present invention discloses a plugging method for a safely abandoned well, and belongs to the technical field of oilfield well plugging. The plugging method for a safely abandoned well comprises: separating a plugging layer and a layer to be plugged in the casing; placing a throw-away packer in the casing and arranging it above the plugging layer; injecting cement into the plugging layer; sealing the throw-away packer and pressurizing the cement in the plugging layer so that the cement enters the oil layer of the plugging layer; after the cement in the plugging layer solidifies, opening up the plugging layer and the layer to be plugged, and plugging the layer to be plugged. The plugging method for a safely abandoned well of the present invention can protect the casing, effectively reduce the risk of plugging construction, shorten the construction period, improve the plugging quality, and reduce the construction cost.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield well sealing, and in particular to a safe abandoned well sealing method. Background Art

[0002] At present, the plugging method for abandoned wells in Liaohe Oilfield is from top to bottom. A cement plug is drilled into each plugging layer, and then the plugging is completed. After the pressure test is qualified, the cement plug is drilled out to plug the next layer. This plugging method has a low cost, but it is more dangerous for abandoned wells with a long service life, because each time the casing plugged above the plugging layer has to withstand a large cement injection pressure, so when the plugging layer does not absorb well, it will cause the cement injection pressure to increase, and at the same time greatly increase the risk factor. Once the casing ruptures at this time, it will cause an engineering accident. Summary of the invention

[0003] The present invention provides a safe abandoned well plugging method, which solves or partially solves the technical problem in the prior art that each time the casing above the plugging layer is plugged, the casing has to withstand a large cementing pressure, which increases the risk factor. Once the casing ruptures at this time, it will cause an engineering accident.

[0004] In order to solve the above technical problems, the present invention provides a method for plugging a safely abandoned well, including: separating a plugging layer and a layer to be plugged in a casing; placing a throw-away packer in the casing and arranging it above the plugging layer; injecting cement into the plugging layer; sealing the throw-away packer and pressurizing the cement in the plugging layer to allow the cement to enter the oil layer of the plugging layer; after the cement in the plugging layer solidifies, opening up the plugging layer and the layer to be plugged, and plugging the layer to be plugged.

[0005] Furthermore, the step of separating the plugging layer from the layer to be plugged in the casing comprises: placing a cement plug in the casing and arranging the cement plug between the plugging layer and the layer to be plugged.

[0006] Furthermore, the cement plug is arranged 5-10 meters below the sealing layer.

[0007] Furthermore, placing the release packer into the casing comprises: placing the release packer into the casing through a release string; when the release packer reaches above the plugging layer, pressurizing and sealing the release packer to seal the release packer and the casing.

[0008] Furthermore, the drop-away packer is anchored on the inner wall of the casing through slips; when the drop-away packer is sealed, the drop-away string is pulled out.

[0009] Furthermore, the injecting cement into the plugging layer comprises: passing the squeeze plugging string through the drop-out packer to the bottom of the plugging layer, and injecting cement.

[0010] Furthermore, the sealing of the drop-away packer and pressurizing the cement in the sealing layer include: a sealing core shaft is provided on the extrusion plugging string; the extrusion plugging string is lifted so that the sealing core shaft on the pressurized plugging string reaches the central pipe of the drop-away packer and performs sealing; the cement in the sealing layer is pressurized by the extrusion plugging string so that the cement enters the oil layer of the sealing layer; and when the pressurization is completed, the extrusion plugging string is pulled out.

[0011] Furthermore, after the cement in the plugging layer solidifies, the safe abandoned well plugging method further comprises: inserting a reaming drill bit into the casing; grinding off the solidified cement at the plugging layer in the casing by the reaming drill bit, and performing a pressure test.

[0012] Furthermore, the opening of the blocking layer and the layer to be blocked includes: when the pressure test is qualified, drilling through the cement plug by the reaming drill bit; when the cement plug is drilled through, pulling out the reaming drill bit; and blocking the layer to be blocked.

[0013] Furthermore, when the plugging of the layer to be plugged is completed, the drop-out packer is removed.

[0014] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0015] Since the plugging layer and the layer to be plugged are separated in the casing, the release packer is placed in the casing and arranged above the plugging layer, cement is injected into the plugging layer, the release packer is sealed, and the cement in the plugging layer is pressurized to make the cement enter the oil layer of the plugging layer. Therefore, the high pressure generated by the pressurized cement cannot be transmitted above the release packer, which fully protects the casing above the release packer, effectively reduces the risk of plugging construction, shortens the construction period, improves the plugging quality, and reduces the construction cost. After the cement in the layer to be plugged solidifies, the plugging layer and the layer to be plugged are opened to plug the layer to be plugged. Therefore, the high pressure generated by squeezing cement in the layer to be plugged is blocked by the cement solidified at the plugging layer and will not be transmitted above the plugging layer. Therefore, the casing is fully protected, effectively reduces the risk of plugging construction, shortens the construction period, improves the plugging quality, and reduces the construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the plugging method for a safe abandoned well provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] See also Figure 1A safe abandoned well plugging method provided by an embodiment of the present invention comprises the following steps:

[0018] Step 1: Separate the plugging layer 3 and the layer to be plugged 4 in the casing 2.

[0019] Step 2: Place the drop-out packer 5 into the casing 2 and set it above the plugging layer 3.

[0020] Step 3, injecting cement into the plugging layer 3.

[0021] Step 4: seal the drop packer 5 and pressurize the cement in the plugging layer 3 to allow the cement to enter the oil layer of the plugging layer 3.

[0022] Step 5: after the cement in the blocking layer 3 solidifies, the blocking layer 3 and the blocking layer 4 are connected to block the blocking layer 4.

[0023] In the specific implementation manner of the present application, the plugging layer 3 and the layer to be plugged 4 are separated in the casing 2, the release packer 5 is placed in the casing 2 and arranged above the plugging layer 3, cement is injected into the plugging layer 3, the release packer 5 is sealed, and the cement in the plugging layer 3 is pressurized to make the cement enter the oil layer of the plugging layer 3. Therefore, the high pressure generated by squeezing cement cannot be transmitted above the release packer 5, so that the casing 2 above the release packer 5 is fully protected, the plugging construction risk is effectively reduced, the construction period is shortened, the plugging quality is improved, and the construction cost is reduced. After the cement in the layer to be plugged 3 is solidified, the plugging layer 3 and the layer to be plugged 4 are opened to plug the layer to be plugged. Therefore, the high pressure generated by squeezing cement in the layer to be plugged 4 is blocked by the solidified cement at the plugging layer 3 and will not be transmitted above the plugging layer 3. Therefore, the casing 2 is fully protected, the plugging construction risk is effectively reduced, the construction period is shortened, the plugging quality is improved, and the construction cost is reduced.

[0024] Specifically, separating the plugging layer 3 from the layer to be plugged 4 in the casing 2 includes:

[0025] The cement plug 1 is placed in the casing 2 and arranged between the plugging layer 3 and the layer to be plugged 4. The plugging layer 3 and the layer to be plugged 4 are separated by the cement plug 1. Since the cement plug 1 is low in cost and easy to obtain, the cost can be reduced.

[0026] In this embodiment, the cement plug 1 is arranged 5-10 meters below the plugging layer 3 to ensure that the cement can enter the oil layer of the plugging layer 3.

[0027] In this embodiment, the thickness of the cement plug 1 is 10 meters, which ensures that the plugging layer 3 can be separated from the layer to be plugged 4.

[0028] Specifically, placing the drop packer 5 into the casing 2 includes:

[0029] The drop-away packer 5 is placed into the casing 2 through the drop-away string.

[0030] When the release packer 5 reaches above the plugging layer 3, the release packer is pressurized to seal the release packer 5 and the casing 2, ensuring that the high-pressure release packer 5 can separate the casing at the plugging layer 3 from the casing above the high-pressure release packer 5.

[0031] The drop-away packer 5 is anchored on the inner wall of the casing 2 by means of slips, ensuring that the drop-away packer 5 is securely connected to the casing 2 .

[0032] When the release packer 5 is sealed, the release string is pulled out to prevent the release string from interfering with the subsequent plugging process.

[0033] In this embodiment, the release packer 5 is fixedly arranged on the intact inner wall of the casing 2. The release packer 5 can be a high-pressure resistant large-diameter release packer.

[0034] Specifically, cementing the plugging layer 3 includes:

[0035] The squeeze plugging string 6 is passed through the hand-free packer 5 to reach the bottom of the plugging layer 3, and cement is injected. The squeeze plugging string 6 is used to inject cement into the plugging layer 3, which is easy to operate.

[0036] Specifically, sealing the drop packer 5 and pressurizing the cement in the plugging layer 3 includes:

[0037] A sealing core shaft 7 is provided on the extrusion plugging column 6 .

[0038] The plugging column 6 is lifted and squeezed, so that the sealing mandrel 7 on the pressurized plugging column 6 reaches the central pipe of the drop packer 5 and performs sealing.

[0039] The cement in the plugging layer 3 is pressurized by squeezing the plugging column 6 , so that the cement enters the oil layer of the plugging layer 3 .

[0040] When the pressurization is completed, the squeezed plugging pipe column 6 is removed.

[0041] In this embodiment, the step of allowing cement to enter the oil layer of the plugging layer 3 includes:

[0042] The casing 2 is provided with a plurality of perforations.

[0043] When the squeeze plugging string 6 pressurizes the cement between the hand-off packer 5 and the layer to be plugged 4, the cement enters the oil layer of the plugging layer 3 through the perforations, ensuring that the plugging layer 3 is completely plugged.

[0044] In this embodiment, when the cement in the plugging layer 3 solidifies, the plugging column 6 is pulled out to prevent the plugging column 6 from interfering with subsequent processes.

[0045] Specifically, after the cement in the plugging layer 3 solidifies, the safe abandonment well plugging method further includes:

[0046] A reaming drill bit is lowered into the casing 2 .

[0047] The solidified cement at the plugging layer 3 in the casing 2 is ground off by the reaming drill bit, and a pressure test is performed to test whether the solidified cement at the plugging layer 3 meets the requirements.

[0048] Specifically, opening up the blocking layer 3 and the layer to be blocked 4 includes:

[0049] When the pressure test is qualified, the cement plug 1 is drilled through by the reaming drill bit.

[0050] When the cement plug 1 is drilled through, the reamer drill bit is pulled out to seal the layer 4 to be sealed.

[0051] In this embodiment, when the layer to be blocked 4 is blocked, the squeeze plugging string 6 is passed through the hand-free packer 5 and the blocking layer 3 in sequence to reach the bottom of the layer to be blocked 4, and cement is injected. By pressurizing the cement in the layer to be blocked 4 with the squeeze plugging string 6, the cement enters the oil layer of the layer to be blocked 4 through perforations, ensuring that the layer to be blocked 4 is completely blocked. When the cement in the layer to be blocked 4 solidifies, the squeeze plugging string 6 is pulled out to prevent the squeeze plugging string 6 from interfering with subsequent processes.

[0052] Specifically, when the plugging of the layer 4 to be plugged is completed, the hand-free packer 5 is removed to complete the plugging process.

[0053] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for plugging a safely abandoned well, characterized in that: include: Separating the plugging layer and the layer to be plugged in the casing; placing a drop-out packer into the casing and arranging it above the plugging layer; injecting cement into the plugging layer; The drop packer is sealed and the cement in the plugging layer is pressurized so that the cement enters the oil layer of the plugging layer; After the cement in the blocking layer solidifies, the blocking layer and the layer to be blocked are connected to block the layer to be blocked; Placing the drop-away packer into the casing comprises: Putting the drop-away packer into the casing through a drop-away string; When the release packer reaches above the plugging layer, the release packer is pressed to seal the release packer and the casing, ensuring that the release packer separates the casing at the plugging layer from the casing above the release packer; The step of injecting cement into the plugging layer comprises: Passing the squeeze plugging pipe string through the drop packer to the bottom of the plugging layer, and injecting cement; Sealing the drop packer and pressurizing the cement in the plugging layer includes: The extrusion plugging column is provided with a sealing mandrel; Lifting the squeeze plugging pipe column, so that the sealing mandrel on the squeeze plugging pipe column reaches the center pipe of the drop packer, and performs sealing; The cement in the plugging layer is pressurized by the extrusion plugging column so that the cement enters the oil layer of the plugging layer; When the pressurization is completed, the squeezed plugging pipe column is removed.

2. The method for plugging a safe abandoned well according to claim 1, characterized in that: The step of separating the plugging layer and the layer to be plugged in the casing comprises: A cement plug is placed in the casing and arranged between the plugging layer and the layer to be plugged.

3. The method for plugging a safe abandoned well according to claim 2, characterized in that: The cement plug is arranged 5-10 meters below the sealing layer.

4. The method for plugging a safe abandoned well according to claim 1, characterized in that: The drop packer is anchored on the inner wall of the casing through slips; When the release packer is completely sealed, the release string is pulled out.

5. The method for plugging a safe abandoned well according to claim 2, characterized in that: After the cement in the plugging layer solidifies, the safe abandonment well plugging method further comprises: inserting a reaming drill bit into the casing; The cement solidified at the sealing layer in the casing is ground off by the reaming drill bit, and a pressure test is performed.

6. The method for plugging a safe abandoned well according to claim 5, characterized in that: Opening up the blocking layer and the layer to be blocked comprises: When the pressure test is qualified, the cement plug is drilled through by the reaming drill bit; When the cement plug is drilled through, the reaming drill bit is pulled out; The layer to be blocked is blocked.

7. The method for plugging a safe abandoned well according to claim 1, characterized in that : When the plugging of the layer to be plugged is completed, the drop-out packer is removed.

Images