Oil well casing damage will cause the following hazards to oilfield development:
The production pipe string cannot be normally lowered into the well;
When the bad part of the casing is in the water layer or sand layer position, the oil well will produce a large amount of water or sand;
Oil well stimulation measures cannot be carried out;
Easy to cause casing blowout;
Cause the oil well to be scrapped.
There are several ways to repair the casing and to repair the seam or hole:
Squeeze Cement Slurry
When the pressure of the oil layer is not large, and the cracking and leakage are not serious, the cement slurry can be repaired. The technical method is as follows: firstly, the diameter of the well is 8 to 10 mm smaller than the inner diameter of the casing, and then a suspended occluder (the name of the tool is called bridge plug) at the appropriate position of the fracture, and the well bore below the breach is temporarily sealed off. Then, a certain amount of cement slurry is injected above the bridge plug to solidify into a cement plug. After the cement plug is solidified, the cement plug in the casing is drilled, and the quality of the cement seal is tested by pressure test, and the sealing is confirmed. After the quality is qualified, the suspended occluder (bridge plug) is drilled and sanded to the bottom of the well. The casing repaired by this method can generally withstand a pressure of 40 to 80 MPa, and the high-pressure construction of the well should be protected by a lower packer to avoid the high pressure.
Change the Casing
When the rupture position is in the upper part of the oil well, and the casing above the broken hole can be taken out by the buckle, the casing above the accident section can be all raised up by the reverse buckle method, and the new casing is re-inserted, and the buckle is tightened. The advantage of this method is to ensure the consistency of the inner diameter of the casing, and the downhole tool can be smoothly passed in the future operation; the disadvantage is that the casing thread of the downhole buckle is not as tight as the wellhead.
That is, a thin-walled pipe is attached to the inner wall of the bad casing for the purpose of repair. The principle of the process is: after a special high-pressure rubber cylinder is sleeved with a bellows (thin wall tube) to the damaged position of the well casing, the pressing force causes the rubber cylinder to expand and expand the bellows to make the bellows fit. The casing is damaged at the inner wall, and the sleeve is bonded to the bellows by the adhesive. After the adhesive is solidified, the drill is removed and the high pressure resistant rubber cylinder is taken out. This subsidy process is simple and safe to operate.
The wells broken by the casing were repaired in three cases. The first is broken but not misplaced; the second is broken but the misalignment is not serious; the third is broken and severely misaligned, and even the lower casing cannot be found.
In order to obtain the displacement after the casing is broken, the depth of the fault, the relative distance between the upper and lower sides of the fracture, and whether the fracture is deformed, etc., the situation can be clarified by using lead printing and instrument testing.
For casings that are not broken, they can be repaired by grouting; for casings that are broken but not dislocated, if the casing is allowed to be changed, the casing can be repaired; if the casing is not replaced, the casing can be used. The method of the device is repaired, that is, after the casing of the broken portion is milled and cut off, the upper and lower casings are clamped and pulled by the patching tool in the middle to ensure the normal production of the oil well.
Wells that are severely misaligned after breaking and cannot find the casing of the lower section can be treated by the sidetracking method. That is, the well bore at the breakage is cemented to death, and one well bore is drilled from the lower casing of the upper casing, and the casing is cemented and completed with a smaller casing than the original casing.
9 5/8"(244.48mm) Seamless oil Casing pipe
API-5CT Casing Pipe Steel grade: J55/K55/N80/L80/P110/C95/13Cr/28Cr
Threads: BTC, LTC, STC，PRMIUM CONNECTION
Length range: R1, R2, R3
If you interested in our products, feel free to contact us.
244.48(9 5/8" )
H, J, K
J, K, C, L, N
C, L, N, P
C, L, N, P, Q
C, L, N, P, Q
a: Buttress casing is available with regular, special clearance couplings or special clearance couplings with special bevel.
P= Plain end; S= Short round thread; L= Long round thread; B= Buttress thread.
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