Construction Steps
◆Select the appropriate casing scraper according to the casing inner diameter.
◆Connect the casing scraper to the bottom of the pipe string. When conditions permit, the lower end of the scraper can be connected to the liner to increase the weight when entering the well, so as to compress and retract the blades and knives.
◆Operate smoothly when running the string, and control the speed of running the string to 30 pieces/h. When it reaches 50 meters in front of the skiving section required by the design, the lowering speed is controlled at about 5m/min. Start the pump and cycle 1-5m above the designed scraping section. After the circulation is normal, slowly lower the pipe string while slowly rotating it in the direction of tightening the thread. Then lift the pipe string and scrape it repeatedly. Continue to lower the pipe string after normal suspension.
If you encounter obstacles halfway, stop running the pipe string when the hanging weight drops by 20- 30KN, and do not hit hard. The pipe string should be rotated while washing the well and scraped repeatedly until the hanging weight is normal, and then the pipe string should be continuously pulled down, generally scraping the pipe to 10m below the perforated interval.
◆After scraping, a large displacement reverse circulation must be used to wash the well for more than one week to wash the scraped dirt out of the ground.
◆After the well cleaning is completed, pull out all scraping pipe strings in the well and the scraping operation is completed.
Operation requirements for casing scraping
◆Select the appropriate casing scraper. When scraping casing, it is necessary to prevent the scraper from rotating the shackle in the direction of the blade. It is best to choose a scraper with the blades arranged in different directions.
◆Before running the casing scraper into the well, carefully check whether its external size (outer diameter, length, blade extension) can meet the scraping requirements to ensure the scraping quality.
◆The scraping string should be lowered smoothly. Under normal circumstances, the scraping string should be lowered by the weight of the scraping string and the scraper should be pressurized for scraping. If you encounter any obstruction during the scraping process, you should gradually pressurize it. Under normal circumstances, the pressure should be 10- 20KN, and the maximum pressure should not exceed 30KN.
◆When scraping the perforated interval, a special person must be assigned to command. Start the pump and cycle 2 meters above the designed scraping interval. After the circulation is normal, slowly lower the pipe string while slowly rotating the pipe string in the direction of tightening the thread, and then lift the pipe string repeatedly. Scrape it multiple times, and then continue to run the pipe string after normal suspension.
◆Scraping times: Generally, scrape once in the unperforated part, and the number of scraping times in the sealing position should meet the design requirements; lift and lower the scraping times in the perforating position three times without encountering obstruction, and the hanging weight is normal (or the scraping times meet the design requirements).
◆Scraping and flushing: Under normal circumstances, after scraping to the design depth, a large displacement is required to fully wash the well and clean the dirt in the well. In addition, many well cleaning plans are formulated according to specific conditions during the scraping process, and segmented well cleaning methods can be adopted.
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