What Is an Abandoned Well?

Abandoned well operations in the ocean should ensure that there is no channel for formation fluids to flow inside and outside the well, and that the formation fluids do not penetrate to the bottom of the sea, and the risk of polluting the marine environment.

(1) Abandoned well operations shall be conducted in such a way that there is no channeling of formation fluids inside and outside the well, and there is no risk of formation fluids channeling up to the muddy surface of the sea floor and polluting the marine environment.

(2) Cement or packer should be used to separate the permeable formation and the oil and gas formation to ensure that the formation fluids between different pressure layers do not pass through each other.

(3) At least one cement plug should be injected above the possible production zone, or from the open hole to the wellhead.

(4) Only when the wellbore is safe can the wellhead blowout preventer be removed.

(5) The cutting positions of each layer of casing in the permanent abandoned wells in the territorial sea and the waters within it shall be 4m below the seabed mud surface. Wellhead facilities on the bottom of the sea that are left outside the territorial sea shall not hinder the use of other marine dominant functions.

(6) Production well sections that are no longer used should be discarded in the manner of permanent abandoned wells. ^[1]

1. Casing or stern tube perforation to complete the well

(1) Drilling bridge plugs to pour cement or injecting cement plugs to seal the oil and gas layer within 15m above the top of each group of perforation sections. Within 15m above the top oil and gas layer, the bridge plug should be lowered, pass the pressure test, and be filled with a cement plug with a length of not less than 30m; or a cement plug with a length of not less than 50m, and then set and test the top of the plug and pass the test.

(2) For natural gas wells, wells containing corrosive fluids, or other wells with formation pore pressure equivalent density higher than 1.30g / cm3 (hereinafter referred to as "special wells"), the length of the cement plug when the oil and gas layers are sealed with cement is not It should be less than 30m. When the bridge plug is used for isolation, the top of the bridge plug should be poured with cement. The bridge plug should be drilled within 15m above the top oil and gas layer.

(3) Inject a cement plug with a length of not less than 60m at about 30m below the tail pipe hanger or grading hoop, and wait for the top surface of the cement plug to set.

(4) Inject a cement plug with a length of not less than 50m in the inner casing or in the annulus near the depth of the surface casing shoe. The cement plug length should not be less than 100m in special wells. Top of cement plug.

(5) Keep the wellhead above the water surface, and after completion of the last abandoned well cement plug operation, take anti-corrosion and antifreeze measures above the cement plug; to keep the wellhead below the water surface, the wellhead cap or mudline hanger protective cap should be installed according to Measures such as anticorrosion and waterproofing are required.

(6) Set wellhead markers and safety protection measures in accordance with the requirements of the local government authority.

2. Openhole exploration with open-eye or open-eye sieve

(1) Fill the wellbore section or screen with completion fluid to protect the oil and gas layer.

(2) Set a drillable bridge plug within 30m above the open casing shoe or packer on the top of the screen and pass the pressure test. Put a cement plug with a length of not less than 30m on the bridge plug. Special wells are on the bridge plug. The length of the cement plug mentioned above should not be less than 50m. Wait for setting, test pressure and explore the top surface of the cement plug.

(3) A cement plug with a length of not less than 50m shall be injected upward in the inner casing or in the annulus near the depth of the surface casing shoe. The special well shall be seated with a drillable bridge plug at this position, and the cement plug with a length of not less than 100m shall be injected after passing the pressure test.

(4) Keep the wellhead above the water surface and take anti-corrosion and anti-freeze measures above the cement plug after completing the last abandoned well cement plug operation; if the wellhead is kept below the water surface, the wellhead cap or mudline hanger protective cap should be installed. Measures such as anticorrosion and waterproofing are required.

(5) Set up wellhead markers and safety protection facilities according to the requirements of the local government authority.

3 Non-production development well

(1) Wells that have not been perforated after cementing casing or stern tube in abnormal pressure intervals or oil and gas display intervals should be condensed and qualified for full-wellbore pressure testing. Surface wellheads can monitor wellhead pressure and provide well killing. Wellhead device for the passage. Special wells should run into or suspend temporary tubing strings and block the internal and external channels of the tubing strings, and use wellhead devices that can monitor wellhead pressure and provide well killing channels.

(2) Perforated wells or open-hole completion wells shall be run into the production pipe string, and the oil (gas) tree shall be installed according to the design and the pressure test of the wellhead device shall be qualified. The subsea wellhead can complete the (2) (3) operation of the temporary abandoned well of the exploration well according to the open-eye or open-eye screen pipe.

(3) For subsequent operations, refer to (4) and (5) of the temporary abandoned wells for the completion of exploration wells with open-eye or open-eye sieve tubes as required.

4 Production wells in production

(1) Before the wells that have been put into production are temporarily abandoned, the production system shall be isolated by the pressure system:

Close the layered production sliding sleeve from the spray well, and run down the plugging device to block the passage of the formation fluid to the wellhead. Kill the well, lift out the production string, and enter the packer plug or recyclable packer at the top of the production layer. The pressure test is qualified;

The non-self-jetting wells are closed to produce the sliding sleeve. Kill the well, lift the downhole tubing string, and enter the packer plug or recoverable packer at the top of the production layer. The pressure test is qualified;

Fill the top packer plug or recyclable packer with sand with a height of not less than 2m.

(2) Set a drillable bridge plug within 30m above the depth of the tail pipe hanging, top packer or naked eye and casing joint and pass the pressure test, and put a cement plug with a length of not less than 30m on the bridge plug. The length of cement plug injected into drillable bridge plug for special well shall not be less than 50m. Wait for setting, test pressure and explore the top surface of the cement plug.

(3) A cement plug with a length of not less than 50m shall be injected upward in the inner casing or in the annulus near the depth of the surface casing shoe. The special well shall be seated in this position with a drillable bridge plug, and the cement plug with a length of not less than 100m shall pass the pressure test.

(4) Keep the wellhead above the water surface and take anti-corrosion and anti-freeze measures above the cement plug after completing the last abandoned well cement plug operation; if the wellhead is kept below the water surface, the wellhead cap or mudline hanger protective cap should be installed. Measures such as anticorrosion and waterproofing are required.

(5) Set up wellhead markers and safety protection facilities according to the requirements of the local government authority.

5. Temporary abandoned well operation procedure for underwater wellhead

(1) After injecting anticorrosive liquid or diesel oil at the wellhead, lift out the blowout preventer, and then insert the anticorrosive cap. Coat the anticorrosive cap with white paint, and attach the guide rope about 3m above the running tool. When installing the anticorrosive cap, open the drill string compensator in advance and observe with ROV or underwater TV. After installation, turn it back and send it in. tool.

(2) The guide ropes are loosened, and 4 guide ropes are sequentially recovered by the ROV from the guide posts of the permanent guide base plate. Be careful not to get the ROV in the guide rope.

6. Operation procedure for temporary abandonment of water wellhead with mudline hanger

(1) After the last cement plug is injected, lift the drill pipe to the mudline hanger, and replace the drilling fluid with seawater to lift the drill pipe.

(2) Remove the BOP group and 279.4mm (11 ) sleeve cross.

(3) At the top of the 244.5mm casing, cut a pair of J -shaped grooves, use a drill pipe to connect the T shape tool into the J -shaped groove, lift a certain weight, and lift out a 244.5mm casing card Tile suspension; then turn the casing forward and turn it down from the mudline hanger into the tool.

(4) Run the spear into the casing, or use the T -shaped tool (when strength meets the requirements) to recover the casing and hanger into the tool. (5) Remove the 346.1mm (135/8 ) sleeve tee and recover it. Use the method of recovering 244.5mm sleeve to recover the 339.7mm sleeve above the mud line and the feeding tool.

(6) Run the anticorrosive cap of 339.7mm into the casing and inject anticorrosive liquid or diesel oil to fill the mudline hanger.

(7) Remove the 539.8mm (211/4 ) casing head.

(8) At the top of the 508.0mm casing, cut a pair of J -shaped grooves, use a drill pipe to connect the T shape tool into the J -shaped groove, forward the casing, and feed the tool from the mudline hanger Open up.

(9) Spear under the casing, or cut two holes in the 508.0mm casing, use a high-strength steel wire sleeve to recover the casing above the mud line and the feeding tool.

(10) Invert the buckle tool according to the requirements of the catheter remote connector inversion (if there is no lower remote connector, the diver needs to screw the release screw on the first catheter connector above the seabed).

(11) Cut two holes on the top of the catheter, and use a high-strength steel wire sleeve to recover the catheter and remote control connector.

(12) Connect an anti-corrosion cap to the feeding tool, mark the direction and feed it with a drill pipe. Under the command of the diver, install an anticorrosive cap on the wellhead, open it up and retrieve the delivery tool.

1. Casing or stern tube perforation to complete exploration

(1) Isolation between oil and gas layers. Inject cement plugs upwards not less than 30m from the bottom of each group of oil and gas layers. The cement return height should not be less than 30m above the perforation section. When the interval between layers is short, the bridge plug can be lowered within 15m above the top of the perforation section of the oil and gas layer. Pass the pressure test and pour the cement.

(2) The top of the oil and gas layer is blocked. The cement return height of the uppermost oil and gas layer should not be lower than 100m above the top of the perforation section, waiting for setting, pressure test and exploring the top surface of the cement plug; , And inject a cement plug with a length of not less than 100m on the bridge plug. Natural gas wells, wells containing corrosive fluids or other wells with formation pore pressure equivalent density higher than 1.30g / cm3 (hereinafter referred to as "special wells") should be inserted into the squeeze packer within 15m above the top perforation section. The pressure test is qualified. Cement is squeezed into the oil and gas layer by trial squeeze injection and intermittent squeeze. The minimum squeeze volume designed is not less than 15m. The maximum squeeze pressure is the original formation rupture pressure of the well section. After the cement extrusion is completed, a cement plug with a length of not less than 50m is injected on the cement squeeze packer.

(3) Inject a cement plug with a length of not less than 60m at about 30m below the tail pipe hanger or grading hoop, and wait for the top surface of the cement plug to set.

(4) Inject a cement plug with a length of not less than 100m in the inner casing or in the annulus near the depth of the surface casing shoe, and wait for the setting of the cement plug and test the cement plug surface. The special well shall be seated at this position with a bridge plug, which has passed the pressure test, and a cement plug with a length of not less than 100m shall be injected on it. (5) Cut and recover the casing and casing head layer by layer. A cement plug with a length of not less than 60m is injected about 30m below the cut of each layer of casing. The length of the last abandoned well cement plug (also known as the cement cap) should not be less than 50m, and the top surface of the cement plug is between 40m and 30m below the mud bottom surface.

(6) Remove the remnants of the sea floor according to the requirements of the competent authority of the local government.

2. Openhole exploration with open-eye or open-eye sieve

(1) Isolation between oil and gas layers. Cement plugs are used to block open-hole well sections or to block the flow channels between oil, gas, and water permeable layers of open-hole screen well sections. The length of a single cement plug should not be less than 50m. When plugging the oil, gas, and water layers with a cement plug, it should cover from the bottom of the blocked oil, gas, and water layer below 30m to the top of the blocked layer and not less than 50m.

(2) The top of the oil and gas layer is blocked. Put a cement plug with a length of not less than 50m on the top casing shoe or the packer on the top of the naked eye, and wait for the top surface of the cement plug to set and pass the pressure test. For special wells, a cement squeeze packer should be seated within 30m above the open casing shoe or the top of the screen packer. The pressure test is qualified. The cement is squeezed into the oil and gas layer by test squeeze injection and intermittent squeeze. The minimum squeeze-in volume should not be less than 30m of the wellbore volume, and the highest squeeze-in pressure is the original formation rupture pressure of the well section. After the cement extrusion is finished, a cement plug with a length of not less than 100m is poured on the cement packer.

(3) Inject a cement plug with a length of not less than 100m at about 30m below the tail pipe hanger or grading hoop, and wait for the top of the cement plug to set and explore.

(4) Subsequent completion of (4) ~ (6) of the permanent well abandonment of exploration wells according to casing or tail pipe perforation.

3 Development well

(1) Column recovery. Kill the well and lift the production string downhole.

(2) Interlayer isolation of naked eye segments. Cement plugs are used to block open-hole well sections or to block the flow channels between oil, gas, and water permeable layers of open-hole screen well sections. The length of a single cement plug should not be less than 50m. When plugging the oil, gas and water layers with cement plugs, it should be returned from the bottom of the blocked oil, gas and water layers below 30m to no less than 50m above the top of the blocked layer.

(3) Interlayer isolation of perforation section. Cement plugs shall be injected upwards not less than 30m below the bottom of each group of oil and gas layers in sections, and the cement return shall be no less than 50m above the top of each group of oil and gas layers. The layered pipe string is used for mining or injection, but when the interval between layers is short, the upper sleeve of the layered pipe string can be closed, and the cement can be squeezed downward to block the adjacent production layer. The top surface of the cement plug should be higher than the top of the blocked section. Not less than 50m.

(4) The top oil, gas and water layers are blocked. The cement return height of the top oil, gas, and water layers should be no less than 100m above the top of the plugged layer. Wait for setting, test the top surface of the cement plug, and pass the pressure test. For special wells, a cement squeeze packer should be seated within 30m above the top of the oil and gas layer, casing shoes on the top of the naked eye, or the top of the screen packer. The pressure test is qualified. Squeeze the cement, design the minimum squeeze-in volume should not be less than 30m of the wellbore volume, and the maximum squeeze-in pressure should not exceed the original formation rupture pressure of the well section. After the cement extrusion is completed, a cement plug with a length of not less than 50m is injected on the cement squeeze packer.

(5) Special development wells that cannot fully recover production pipe strings in the well should take the following measures: Avoid couplings to perforate or cut the production pipe string above the unpackable packer or falling fish roof, perform well killing and Well washing operation, cutting and recycling the upper free production pipe string. Squeeze the cement packer at a position of 2 ~ 5m from the drilling or cutting position of the production pipe string. Cement squeeze operation is carried out by using a squeeze squeeze packer and a test squeeze column and intermittent squeeze method. The maximum squeeze pressure does not exceed the highest original formation rupture pressure of the lower well section. After the cement extrusion is finished, a cement plug with a length of not less than 100m is poured on the cement packer.

(6) Inject a cement plug with a length of not less than 100m at about 30m below the tail pipe hanger or grading hoop, and wait for the top surface of the cement plug to set.

(7) Subsequent completion of (4) ~ (6) completion of exploration and permanent abandonment of wells according to casing or tail pipe perforation.

4 Floating Drilling Device Permanent Abandonment

1) Cutting and recovery of 244.5mm and 339.7mm casing by floating drilling equipment

(1) Cutting tool combination.

When cutting 244.5mm casing: 209.6mm cutter body (equipped with C9-8-12 blade arm) + weighted drill rod (5 columns) + underwater rotary head (equipped with 406.4mm support frame) + drill rod.

When cutting 339.7mm casing: 298.5mm cutter body (with C13-8-19 blade arm) + weighted drill rod + underwater rotary head (installed with 406.4mm support frame) + drill rod.

(2) Connect the knife body, install the knife arm in advance according to the cutting position of the casing, and then drive the pump to perform the function test.

(3) Tighten the knife arm, and match the knife arm to the length of the drill of the support frame, and then cut the knife.

(4) Drill down until the underwater rotating head approaches the underwater wellhead, open the drill string compensator, and slowly sit the support frame in the wellhead wear-resistant repair core, and pressurize 20 ~ 50kN.

(5) Rotate first, then slowly turn on the pump. The speed is 60 ~ 70r / min, and the pump displacement is appropriately controlled according to the torque. Note that the torque should not be too large.

(6) Observe the torque change and judge whether the casing is cut. The torque changes from the beginning of the steady state to the continuous change at the time of the cutting, until it is stable after the cutting. During cutting, pay attention to the change of drilling fluid volume to prevent well surge caused by pressure in casing annulus.

(7) After cutting the casing, take out the cutting tool. According to the marks on the cutter arm, determine whether the casing has been cut.

(8) Recycling anti-wear and replenishing heart.

(9) According to the performance of the wellhead device, determine whether the seal assembly needs to be recovered in advance, and if necessary, recover it in advance; if not required, recover it with the casing and its hanger. Run the casing to pick the spear to recover the casing. Before the spear enters the casing, open the drill string compensator. After the casing is caught, use the compensator to lift the casing.

(10) When retracting the casing, the hanger should act as the BOP group and the riser telescopic joint, and should be lifted carefully to prevent scratching.

(11) Remove the casing hanger and recover the casing.

(12) Put cement plugs up and down the casing cut as required.

2) Floating drilling unit from 476.3mm BOP

(1) After pouring cement plugs up and down the 339.7mm casing cut, lift the drill pipe to the wellhead, flush the drill pipe in reverse circulation, and then replace the drilling fluid in the riser with seawater.

(2) Light up the drill rod and shake off the excess drill rod.

(3) Remove the turntable diverter.

(4) Lower the inner tube of the riser telescopic joint and lock it on the outer tube.

(5) Open the wellhead connector and use the ROV or underwater television to check the switch indicating rod.

(6) Lift the blowout preventer group on the drill string compensator and confirm whether the wellhead connector is open.

(7) Take out the riser expansion joint, riser and blowout preventer group.

(8) Fix the BOP group on the base.

3) Cutting and recovery of the floating drilling device 508.0mm casing and 762.0mm conduit operation procedure When two layers of casing are cut and recovered at the same time:

(1) Combined cutting tool: seeker + drill rod + 298.5mm cutter body (with C13-8-42 blade arm) + RSP13 casing spear body (with RSP13-22-2 Kaval spear) + Underwater rotating head + drill collar + weighted drill pipe. It should be noted that the RSP13-22-2 Kavalao spear is sitting on a suspension support ring inside the 476.3mm wellhead, and care should be taken when matching the length of the cutting tool.

(2) After the cutter is assembled, perform a functional test and tighten the knife arm.

(3) Coat the cutter body with white paint.

(4) At about 3m above the cutter body, attach a guide rope to guide the cutter into the wellbore. Before entering the wellbore, open the drill string compensator and observe with ROV or underwater television.

(5) Sitting on the support frame on the suspension support ring in the head of the well, pressurize 40kN, slowly rotate, turn on the pump, and gradually make the speed reach 60 ~ 70r / min. Properly control the displacement of the pump according to the amount of torque. Pay attention that the torque should not be too large.

(6) After the casing is cut, use the spear on the compensator to test and confirm the cut.

(7) Use the guide rope to recover the temporary guide base plate.

5. Permanent abandonment operation during jack-up drilling unit operation

(1) After confirming that the oil and gas layer is sealed and there is no pressure in the annulus of 244.5mm casing, remove the blowout preventer group and 279.4mm (11 ) casing cross.

(2) Combined cutting cutter with 244.5mm casing goes down: 209.6mm cutter body (with C9-8-12 cutter arm) + weighted drill rod + drill rod (as required).

(3) Connect the knife body and the knife arm, and tighten the knife arm after completing the function test. Lower the cutter to the cutting position required by the design, pay attention to avoid the position of the casing coupling, and stop the winch.

(4) Cutting 244.5mm casing: slowly turn the pump first and then gradually increase the displacement. Adjust the pump displacement according to the torque, pay attention that the torque should not be too large. By observing the change in torque, determine whether the casing is cut. Before cutting, open the casing four-way valve so that the pressure that can be trapped in the casing annulus can be released first and the casing cutting can be observed.

(5) After cutting, take out the cutter and check the wear marks to determine whether the casing is cut.

(6) Use a spear to recover the 244.5mm sleeve.

(7) Put cement plugs up and down the casing cut as required.

(8) Remove the 346.1mm (135/8 ) casing cross, and combine 339.7mm casing cutting tool: 298.5mm cutter body (with C13-8-19 blade arm) + weighted drill rod + drill Rod (as needed).

(9) According to the method of cutting and recovering 244.5mm casing, cut and recover 339.7mm casing.

(10) Put cement plugs up and down the casing cut as required.

(11) Remove the 539.8mm (211/4 ) sleeve head.

(12) Combined cutting 508.0mm casing cutter: 298.5mm cutter body (with C13-8-36 blade arm) + 444.5mm stabilizer + weighted drill rod + drill rod (as required).

(13) First perform a functional test on the cutter, then tighten the knife arm and drill.

(14) Lower the cutter to the position required by the design.

(15) Cut the casing. Turn slowly after turning on the pump to gradually increase the displacement. You can adjust the displacement according to the torque. By observing the change in torque, determine whether the casing is cut.

(16) Lift out the cutter. Observe the marks on the knife arm to determine whether the casing is cut.

(17) Cut two holes at the top of the casing, and lift the casing with a wire rope cover.

(18) Before cutting a 762.0mm catheter, tie it with a tether to prevent the catheter from falling after cutting. Cut two holes on the top of the catheter and use a wire rope to hold the shackle properly.

(19) Cutting knife for combined cutting: 298.5mm cutter body (with C13-8-42 blade arm) + 660.4mm stabilizer + weighted drill rod + drill rod (as required).

(20) First perform a functional test on the cutter, and then tighten the knife arm.

(21) Run the cutter to the design position.

(22) The cutting and recovery procedures of 762.0mm catheter are the same as those of 508.0mm casing.

(23) Fill the cement cap. ^[2]

During the operation of the floating drilling device, before and after the completion of the abandoned well operation, the remote submersibles were respectively entered into the seabed around the wellhead (within a radius of 30m) to inspect, photograph and draw the remnants of the subsea wellhead.

For jack-up or fixed drilling installations, if necessary, underwater inspections, photography, and mapping of subsea wellhead relics should be performed.