Technical characteristics and safety technical req

2022-08-08
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Technical characteristics and safety technical requirements of various workover operations

the main works of oil workover operations include: oil test, midway test, engineering test, minor repair, perforation, overhaul, sidetracking, string sealing, and finally the industry said that fracturing, acidizing, sand control, water plugging, profile control, plugging removal, etc. It mainly introduces that the system and mechanism of oil testing, minor repair, overhaul, fracturing and acidizing are not straightened out

(1) wax removal includes mechanical wax removal and thermal wax removal

① mechanical wax removal. Including wax scraping blade wax removal and casing wax removal. Wax scraping is to use the electric winch in the well pad to run into the oil well, move up and down the wax deposition well section of the oil pipe, scrape the wax off the pipe wall and carry it out of the wellhead by oil flow. This method is applicable to flowing wells and wells with less wax deposition; Casing wax removal is to connect the spiral wax scraper under the oil pipe, and use the up and down movement of the oil pipe to remove the wax on the casing wall. Tegracore polyphenylsulfone (PPSU) foam can be used as the core material of various structural foam and sandwich technology, and the rotary table can also be used to drive the scraper bit to scrape; At the same time, liquid circulation is used to bring the cleaned wax to the ground. ② Thermal wax removal. Including electrothermal wax removal, thermochemical wax removal, hot oil circulation wax removal and steam wax removal. Electrothermal wax removal is to use the oil well heating cable to convert electric energy into heat energy to heat the oil flow and increase its temperature to achieve the purpose of wax removal and wax prevention. Thermochemical wax removal uses the heat energy generated by chemical reaction to remove wax. Hot oil circulating paraffin removal is to use the crude oil produced in the well to inject into the well for continuous circulation after heating, so that the temperature in the well reaches the melting point of the wax, and the wax is gradually melted and flows to the surface with the oil. Steam wax removal is to pull out the oil pipes in the well, place them neatly, and then use the high-pressure steam of the steam truck to melt and prick the wax inside and outside the pipe

(2) sand washing

(I) sand washing methods include forward washing, back washing, rotary washing, etc. Positive flushing: the flushing fluid flows to the bottom of the well along the pipe string and returns to the ground from the annular space. Recoil: opposite to the forward stroke. Rotary sand flushing: the power source is used to drive the tool to rotate, and the pump is used to unload the sand circularly. This method is commonly used for overhaul sand flushing

(II) safety technical requirements: ① do not carry pump, packer and other downhole tools to explore the sand surface and wash the sand ② when the sand washing tool is 20m from the upper boundary of the oil layer, the lowering speed should be less than 0.3m/min; ③ Before sand flushing, the oil pipe shall be lifted to more than 3m away from the sand surface, and the pipe string can be lowered only after the pump is turned on and the circulation is normal; ④ Before connecting a single pipe, fully run the ring, and the operation speed should be fast. After the pump is started and the ring is normal, the pipe string can be lowered again; ⑤ During sand flushing, it shall be noted that the pump shall not be stopped in the middle of the process, so as to avoid the pipe string being stuck or blocked by sand deposition; ⑥ For wells with serious sand production, the well must be fully washed before adding a single pipe. The deepening speed should not be too fast to prevent blocking and pump suffocation; ⑦ Wash the well once after 5 pieces of sand are washed continuously to prevent excessive suspended sand in the wellbore; ⑧ If the circulating system fails, when the pump is stopped, the pipe string shall be lifted above the sand surface and moved repeatedly; ⑨ If the lifting system fails, it must keep normal clockwise; ⑩ The pump pressure shall not exceed the safety pressure of the pipeline, and the pump displacement shall be balanced with the outlet displacement to prevent blowout or leakage

the safety technical requirements for pump inspection are as follows: ① take all and accurate data of downhole pump; ② The pump depth shall be accurate and the anti impact distance shall be appropriate; ③ The screw threads of the downhole oil pipes shall be coated with sealing grease in the quantity of 1, 2, 3, 4,... N. the oil pipes shall be free of cracks, leakage and bending, and the screw threads shall be intact; ④ The oil extraction pipe shall be placed on the support with more than 5 fulcrum, and shall not fall to the ground; ⑤ It is not allowed to pull out the tubing if it is stuck when pulling out the tubing; ⑥ Special attention shall be paid to the lifting, lowering and hauling of deep well pumps

(3) wellhead fault handling

(I) method: replace Christmas tree and handle casing spool

(II) safety technical requirements for handling casing spool: ① wellhead electric welding must go through the formalities for using fire at the wellhead of the oil well, and the fire-fighting equipment and tools must be prepared, and the welding and cutting can be carried out only when the fluid flow in the well is stable and there is no oil and gas overflow or oil and gas display at the wellhead; ② After dismantling the Christmas tree, pay attention to the storage of steel rings and other components to prevent bruises; ③ Personnel and wellhead equipment shall be prevented from being injured by falling when lifting Christmas tree; ④ Carefully measure the size before cutting and welding the wellhead, and accurately correct the oil compensation distance after cutting and welding; ⑤ Butt welding shall be adopted for casing welding with thick wall thickness; If the wall is thin or the corrosion is serious, the casing larger than the original casing diameter shall be used for socket welding; ⑥ The welding quality must be guaranteed, and the butt weld shall be welded for more than two times

(4) technical requirements for perforation safety: ① prepare wellhead equipment and installation tools, and make practical preparations for blowout prevention; ② Before perforating, the casing must be sand washed to the artificial bottom according to the specified same diameter; ③ Before new perforation, the casing must be pressure tested and conform to its regulations; ④ The perforation depth error shall not be greater than 0.1M; ⑤ If the perforation depth is more than 3m, the well can be completed only after running the string for well washing; ⑥ During the perforation process, a specially assigned person shall take care of the wellhead to prevent falling objects, and pay attention to whether there is oil and gas display; ⑦ During the whole construction process, the well servicing team must closely cooperate with the perforation team to achieve safe perforation. Fireworks are strictly prohibited around the wellhead

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