Collapsed tubing occurs when external pressure outside the casing is greater than the pressure inside. There are several circumstances which can lead to a collapse, including high pressure outside the casing during operations such as cement squeeze, pressure testing in the annulus, and when the mud level inside the casing drops due to a loss of circulation.
The well location within the rock formation can also have an impact on the potential for collapsed tubing. Seismic activity can cause significant damage to the casing and tubing so careful well design and strict operating procedures are essential to reduce the risk.
When the issue does occur, it can create a significantly restricted area in the wellbore and often results in failure to gain access below the collapsed area in a wellbore. This, in turn, can cause extensive nonproductive time (NPT) to remediate the issue. Planned drilling or intervention work is halted, and production may be deferred. In the most severe instances when the casing collapses the well is completely abandoned.
While the industry continues to focus on enhancing hydrocarbon recovery from existing wells, these operations must remain economically viable. Therefore, preventing and resolving well integrity and access issues have never been more important.
With advancements in expandable technology, it is now possible to reform the restriction in a tubular, enabling the inner diameter (ID) to be opened. This allows for either reinstatement of production back to surface or access to equipment below, permitting operators to resume operations with minimal NPT.Coretrax recently deployed its ReForm wellbore repair tool when an international oil company experienced collapsed tubing in a remote well off the coast of Papua New Guinea. The solution uses hydraulic pressure applied at surface to reform collapsed, oval, or restricted tubulars.
Overcoming Traditional Limitations
During drilling and production activity, tubing and casing are exposed to a range of axial loads and temperatures as the operator utilizes various methods to reach, and then extract, hydrocarbons from the well. In drilling activity, mud losses can often be encountered through thief zones which leads to a lower mud level. With the consistent pressure outside the casing, the collapse resistance can be affected, resulting in full collapse in the wellbore.
Swaging is a conventional and widely used method of repairing collapsed tubing. The process involves a series of swages run downhole to gradually open the collapsed area. It can be done with specialized swage packers or with a hydraulic expandable swage. Both methods provide a bond to the existing casing once properly prepped. The technique can take a significant amount of time to open the area due to the number of different swages required. Each time a larger size is needed, the operator must use significant rig time to trip out of hole. While it can have successful outcomes for repairing damaged areas of well casing or screens for example, due to the weight required in the pipe to swage, this procedure is not suitable for shallow or lateral wells.
