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On-line processing technology of wellhead tubing and casing threads (wellhead repair without firing)
Product introduction
On-line processing technology of wellhead tubing and casing threads (wellhead repair without firing)
With the aging of production wells and the implementation of gas injection measures, the corrosion and damage of wellhead oil and casing are increasing, and the corrosion of pipe thread has become the main reason for the decline or failure of the actual pressure bearing capacity of the wellhead, which has become a potential safety hazard, seriously threatening the safety of production, personal and national property, and has led to serious accidents. Attention has been paid to the repair of abandoned and rusted wellheads, which is of great urgency.
The environment around the oil production wellhead is highly explosive, so it is very risky to cut and weld the wellhead components with fire. High-temperature welding will change the metal structure of the tubing and casing, reduce the strength and corrosion resistance near the welded junction, and the replacement workload is large and the cost is high. Therefore, the method of using cold working technology to cut the waste pipe section online and then implement pipe thread processing will become the best choice for online rapid repair and renewal of wellhead.
Under the technical guidance of the relevant personnel of China University of Petroleum (East China), based on the relevant standards of the petroleum industry, taking the constraints of the actual construction environment as the background, and aiming at simplicity, practicality, high qua lity and safety, the technical device for on-line turning of pipe threads and the internal and external cold processing of pipe breaking has been developed, which meets the design requirements in various simulations and field experiments. Satisfactory results have been achieved, and the national invention patent has been authorized. Through continuous upgrading and transformation, the design and development of a more functional and stable upgrade technology package has been completed.
Package function
The invention relates to a wellhead on-line repair technology (without fire) suit, which mainly comprises a one-way anchor sealing device in a casing, a hydraulically driven internal cooling pipe cutting device, an external cooling pipe cutting device, a pipe thread on-line turning device, a frequency conversion hydraulic station, a pipe thread tightness detection suit, a series of common buckle gauges, a four-in-one monitoring and early warning instrument and a matched special tool. It undertakes different tasks in different construction stages.The frequency conversion hydraulic station is placed at the side air port or the upper air port of the safety area outside the risk area with the wellhead as the center of the circle as specified by QHSE, and is connected with the soft high-pressure pipeline to drive the pipe cutting device inside the casing, the pipe cutting device outside the casing, the pipe thread online turning machine and other equipment to work.
Construction conditions
Wellhead repair is a complex high-risk construction process, the construction operation and construction quality must be standardized, and the construction process must be carried out in an orderly manner according to the plan. Before construction, clean up the surroundings of the wellhead and establish a good and safe construction environment.
1. Before removing the Christmas tree at the wellhead, the wellbore must be packed. It is recommended to install a bridging plug or a one-way anchor seal at the lower part of the pre-construction pipe section;
2. The earthwork around the wellhead shall be cleared, with the wellhead as the center of the circle, the diameter shall not be less than 2m, and the depth shall not be less than 0.8m below the design construction surface;
3. Dredge the safe passage, do not cross operation, and check whether the harmful gases in the construction environment meet the standards.
Process flow
In order to ensure safe, safe and high-quality construction, site inspection must be carried out first, construction plan and abnormal situation prevention plan shall be formulated according to the actual situation, and construction shall be carried out step by step according to the plan.
1. Bridge plug or one-way anchor sealer;
2. Clean earthwork around the wellhead and establish the construction environment;
3. Check whether the harmful gases in the construction environment are up to the standard;
4. Check whether the equipment set is in good condition;
5. Remove wellhead equipment such as wellhead Christmas tree;
6. Inspect and clean construction object;
7. Monitor the harmful gas in the whole construction process, and report the abnormal shutdown for treatment;
8. Install the internal cooling pipe cutter to cut the oil-string casing and unload the broken pipe;
9. Install the external pipe cutter to cut and chamfer the technical casing or surface casing;
10. Install the pipe thread turning machine, turn the pipe thread according to the design requirements, and spray the cutting fluid;
11. Check whether the newly processed thread is compliant with the buckle gauge of the corresponding specification;
12. Connecting pipe thread tightness detection kit, for on-site pressure maintaining detection of threads;
13. Install the casing head, wellhead Christmas tree and BOP, and apply the pipe thread sealing grease (thread oil);
14. Check the capillary pressure gauge of the one-way anchor in the casing and observe whether the downhole pressure is abnormal;
15. If there is no abnormality, remove the one-way anchor seal and recovery sleeve in the casing, and evacuate from the site after the construction is completed;
16. Establish construction technical files;
On-site construction case
On April 28, 2023, in Zhundong Oil Production Plant of Xinjiang Oilfield, the corroded section of 133/8 "surface casing was cut off and 8 threads/hour round pipe thread was turned for B5004 well in the exploration well operation area. It completed the replacement of casing head and wellhead and resumed production.
On May 3, 2024, in the vicinity of Devil City of Xinjiang Oilfield, the technical casing 95/8 "of FHW7004L small workover well of Fucheng Energy was subject to on-site pipe breaking and 8-thread/hour round pipe thread turning. And that update and repairing work of the case head and the wellhead are perfectly completed.
Since the end of October 2024, the field pipe thread turning repair work of 9 wells has been completed successively in Hongqian Block of Xinjiang Oilfield. Oil string casing thread processing, oil string casing and surface casing construction in the same vehicle, oil string casing, technical casing and surface casing construction in the same vehicle shall be carried out on site, and 8 threads/hour round thread and 5 threads/hour partial ladder thread shall be deployed as required.
