Oil Pipe Salvage Technology

Abstract: During production, there are downhole accidents caused by the erosion of harmful substances that cause the inner wall of oil pipes to become thinner and perforated and fall off the well; there are also downhole accidents caused by downhole tools. Downhole accidents occur when oil pipes and downhole tools are stuck in the well and need to be disposed of; there are also downhole accidents caused by oil pipes falling into the well due to other reasons. This article makes a simple summary of the salvage technology used to salvage downhole oil pipes in well workover construction in Western Sichuan in recent years.

Subject heading: Summary of salvage technology of downhole oil pipe salvage tools

[1. Causes of accidents

(1) During the production and transportation process of downhole oil pipes, On the one hand, harmful substances (such as CO, CO2, HS2, etc.) in formation fluids will continue to corrode the oil pipes; on the other hand, the high-speed flowing air will also continuously flush the oil pipes. After a long period of mining, the inner wall of the oil pipe gradually becomes thinner, causing local perforations. When the local tensile strength is weakened under tension, the lower oil pipe falls off and falls into the well. At this time, the oil and casing pressure will change to a certain extent.

(2) Downhole accidents caused when running downhole tools, such as: the explosive gun got stuck in the well due to perforating the oil pipe; the packer in the fracturing pipe string was not unsealed until it was used. The oil casing pressure is blocked; the lower packer is stuck in the casing; there is a cement ring or crystals on the inner wall of the casing that blocks downhole tools, etc.

(3) Downhole accidents caused by other reasons, such as: the wellbore collapses in the open hole and the pipe string is buried; the oil pipe thread connection strength does not meet the requirements and falls off; the make-up torque is too large and the buckle expands or Underground accidents caused by many reasons such as too small tripping.

2. Introduction of salvage tools

1. Commonly used salvage tools include the following types:

(1) Internal fishing undercut tools: can Retractable fishing spears (LM series), single and double slider fishing spears (HLM series), male cones (GZ series), tubing coupling fishing spears (JKLM series), undercut fishing spears (DLM series), etc.

(2) Overshot tools for external fishing: undershot overshot (DLT series), retractable overshot (LT series), female cone (MZ series), window overshot (KLT series) ), short fish top overshot (LT-DJ series), etc.

2. Special tools

(1) Oil pipe connector: use specially heat-treated oil pipe joints to directly connect the oil pipes, and use the neutral point undercut method to pour out the oil pipes in the well. This tool is suitable for keeping the coupling threads of oil pipes in wells intact.

(2) Integrated tools:

Integrated tool for internal and external diameter trimming of fish top; integrated tool for grinding and milling shoe wire bailer; internal docking device or bailer of the bailer Spear integrated tool; grinding and milling shoe slip integrated tool;

(3), other tools

Inner slide overshot, core claw overshot, various grinding shoes

3. Salvage Technology

During salvage operations, it is particularly important to select fishing tools according to the actual conditions in the well. If external fishing tools can be used, external fishing tools should be used because the tensile and torsional resistance of external fishing tools are stronger than those of internal fishing tools, which can reduce the occurrence of secondary accidents in the well.

(1) Lifting

Directly lower the corresponding fishing tools to catch the fallen fish and lift it out of the well.

(2) Undercutting

If the fish is stuck in the well and cannot be lifted out directly, use a fishing and undercutting tool to catch the fish and undercut it in sections to fish it out of the well. The method for undercutting and salvaging the oil pipe is: lift the hanging weight below the hanging weight at the undercut point (the specific stopping position is determined according to the number of oil pipes), first turn the turntable forward and tighten the upper oil pipe buckle, and then lift it to the neutral point and unload it. button, which will pour out more oil pipe. When using the docking device to buckle, the turntable should be opened intermittently after tightening, so that the torque is intermittently transmitted to the docking point without causing the lower part of the oil pipe to fall off and tighten it.

(3) Coupling grinding and salvage

If the fish caught in the well is stuck and the top of the fish becomes thinner, conventional finished fishing tools cannot salvage and grinding is time-consuming, the top of the fish can be avoided. Use a milling shoe to mill off the coupling and salvage the oil pipe. For example: in a Φ127mm wellbore, the oil pipe in the well is Φ60.3mm and the coupling is Φ73mm. The processing is as shown on the right with a milling shoe to mill out the coupling and rely on the wire fishing ring in the milling barrel to fish out the oil pipe with the coupling removed.

(4) Cutting and fishing

During the fishing process, the top of the fish cannot be lowered into the external fishing tool due to its thin wall, and the internal fishing channel is blocked (such as the male cone is broken on the top of the fish) When the fish top is lowered, the outer cutter can be lowered to cut and salvage the well, or when the inner fishing channel is unobstructed and conventional inner and outer fishing tools cannot be used, the method of cutting and salvaging the well with the inner cutter of the tubing can be used.

(5) Grinding and milling

When technologies such as fishing inside and outside the well and sleeve milling cannot be implemented, grinding and milling technology can only be used. According to the well conditions, cement plugs can be used to fix the fish grinding mill, various shapes of grinding shoes (such as concave, collar, group edge, etc.) can be used, and high- and low-efficiency grinding shoes can be used. In short, during the grinding and milling operation, the grinding and milling technology must be flexibly used according to the well conditions to strictly prevent the drill stuck phenomenon caused by incomplete grinding.