1. Change the Christmas tree
With the continuous improvement of the technological level, there are more and more types of Christmas trees. Due to the different structural models of the Christmas tree, the methods and steps of workover are also different. In order to improve the development effect and realize the mining policy of extracting oil under maintaining pressure, the oilfield site often replaces the Christmas tree without threaded flanges with those with threaded flanges. According to the different types and methods of on-site repair and replacement of Christmas trees, it is mainly divided into the following two methods:
1) Repair method of jackscrew flange Christmas tree
(1) Make construction design. According to the specific conditions of the construction well and the content to be repaired, in accordance with the purpose and requirements of the construction, the specific content, methods and steps of the construction are written. At the same time, technical security measures are written.
(2) Drop the oil pipe plug. First, close the main gate of the Christmas tree, put the plug into the well with the discharge pipe, and hold the pressure with the high-pressure well washing truck. When it is confirmed that the tubing channel has been blocked (sealed), the next process can be carried out.
(3) Lift the wellhead. When it is confirmed that the plugged plug is sealed, take a test release to observe the overflow. When there is no blowout at the wellhead, take the time to remove the Christmas tree wellhead screws and remove the Christmas tree.
(4) Repair or welding. Perform restoration work in accordance with the project required by the construction.
(5) Install Christmas trees. After the wellhead component equipment is repaired, the Christmas tree should be installed as soon as possible. (If the Christmas tree cannot be installed temporarily, the wellhead should also be covered). Be sure to tighten the jackscrew on the jackscrew flange to prevent it from being caused by high pressure in the well. Tubing. Go up to make oil and gas escape and so on.
(6) Salvage the plug. When the wellhead failure is repaired, use power equipment to fish out the plug in the well and resume production.
2) Repair method of Christmas tree without top thread flange
The main difference between an oil production pair with threaded flange and a Christmas tree without threaded flange is: the former can be combined with a snubbing and non-spilling wellhead device to form a snubbing facility, and snubbing operations can be adopted: while the latter is all snubbing. Snubbing operations cannot be used without blowout wellhead installations and facilities. Therefore, the repair methods of the two Christmas trees are different.
The method of repairing and replacing the Christmas tree without top thread flange is determined on-site according to the specific conditions of the well and the equipment and material conditions. Generally, the following two methods are often used.
(1) Kill blowout prevention replacement method.
This method uses the function of killing wells to obtain smooth construction conditions. The specific steps are: kill the well, replace the wellhead and a Christmas tree, replace the blowout and wash the well, and resume production.
The advantage of this method is that due to the use of killing hydraulic wells, the high-pressure liquid in the well is relatively stable during construction, safe and reliable, and is not prone to blowout accidents. But its disadvantage is that the kill fluid (especially high-density kill fluid) is used to kill the well, which not only causes a large amount of material consumption, but also easily injects pollutants into the oil layer, blocks the oil flow channel, and repairs the oil well (or water well). After the oil production (water injection) is reduced.
(2) Packer card seal replacement method.
The principle of using this method to replace the Christmas tree is to use the packing effect of the packer, and cooperate with the internal (tubing work and plug> and the wellhead (wellhead controller) non-snubbing and non-blowing operation device to make the well simpler. The oil and gas inside cannot be ejected temporarily, to replace the compression and operation, and to replace the wellhead Christmas tree.
The advantage of this repair method is that there is no need to kill the well, which not only avoids the immersion of the kill fluid on the oil layer during the kill process, but also saves money. At the same time, there is no need to perform well killing work, so there is no rework and missed work that can suppress and fail to suppress the well, which can shorten the construction time and improve the construction efficiency. However, this method has disadvantages. First, once the packer or hydraulic anchor fails, it will cause a blowout or personal accident. Second, the hydraulic anchor can easily damage the casing when it is stuck on the casing wall. It must be loaded and unloaded twice during construction. No blowout wellhead device is used to kill the well, and the process is complicated.
2. Technology to deal with casing cross
The oil well casing spool is located under the main gate of the Christmas tree. When it is damaged or needs replacement by a baby, the wellhead alone cannot control the flow of oil in the well. Therefore, the treatment and repair method is the same as the treatment method of the unthreaded flange wellhead device. There are two methods: one is to use the kill blowout prevention repair method; the other is to use the packer seal repair method. However, considering that the two methods have potential unsafe and unreliable shortcomings, if this method is used to replace the four-way, if it is not handled properly, it will inevitably cause a major accident. Therefore, a method is generally used when repairing and replacing the casing spool, namely the kill blowout prevention repair method. Especially for oil wells with high formation pressure and high production, this point should be paid special attention to.
The specific construction steps of using the kill blowout prevention repair method to treat the casing spool are:
(1) Well killing, killing fluid and killing method should be determined according to the specific conditions of the well.
(2) Remove the flange screws of the wellhead controller and lift the oil tree.
(3) Lift out the tubing in the well.
(4) Welding and cutting off the flanges that were previously installed with the four-way casing pipes, and replacing them with new ones or flanges with jacks to install new wellheads.
(5) On the newly welded casing flange, install a casing cross with a top wire flange.
(6) Run the completion string (the completion string cannot be used as a substitute for the nozzle string, and the nozzle string should be replaced once before), and the kill fluid in the well is replaced. Then use the snubbing and blowout wellhead device to raise this replacement nozzle string, and then run the completion string.
(7) Sit on the Christmas tree and tighten all the screws, especially the jack thread on the jack flange, to prevent blowout caused by the high pressure oil flow in the well after the blowout and the jacking tubing string.
(8) After the completion string (or the replacement nozzle string under the special authority) is used for the replacement blowout and well flushing, it can be restarted.
3. Matters needing attention in handling the casing cross
(1) Wellhead electric welding must go through the oil well wellhead fire procedures, prepare fire-fighting equipment and tools, and the welding must be carried out when the fluid flow in the well is stable and there is no oil or gas blowout or oil and gas display at the wellhead.
(2) After disassembling the Christmas tree, pay attention to the storage of steel rims and other parts to prevent knocks, and pay attention to screws and small tools that cannot be lost or dropped into the well. When installing the Christmas tree, care should be taken to align it and put it gently to prevent smashing the ring or other parts, causing the wellhead to leak and rework.
(3) When lifting the Christmas tree, prevent it from falling and hurting personnel and wellhead equipment.
(4) If the part that needs to be replaced or the cut and welded part is too low, in order to facilitate the electric welding operation, a round pit should be dug in advance to shorten the working time with fire at the wellhead and to ensure the quality.
(5) The size of the wellhead should be carefully measured before cutting and welding, and the oil compensation distance should be accurately calibrated after cutting and welding.
(6) Butt welding should be adopted for welding of thick-walled casing; for thin-walled or severely corroded casing, a casing larger than the original casing diameter should be used for sleeve welding.
(7) The casing of the selected replacement wellhead has the same inner diameter as that of the original casing. When the rock is larger than the inner diameter of the original casing, a slope should be built on the inner diameter of the original casing to prevent the pipe string and tools from being blocked when running the well. Sudden drilling and injury, causing accidents, etc. The inner diameter of the casing to be replaced shall not be smaller than the inner diameter of the original well.
(8) We must ensure the quality of welding. We should weld more than two times at the butt weld joint, and some reinforcing ribs should be appropriately welded around the weld joint to increase its strength. After welding, it is necessary to carry out well-passing and pressure test inspection, that is, it is required to ensure that the welding is straight and not deviated, and it is qualified to withstand the rated pressure without puncture or leakage.
Name: Yancheng Xiongwei Petrochemical General Machinery Equipment Co., Ltd.
Address: No. 1, Tongcheng Road, Equipment Manufacturing Industrial Park, Funing County, Jiangsu Province