Downhole Impulse vs.Downhole Impacts Improve Recovery of Stuck Retrievable Packers

摘要

Stuck retrievable packers are most often fished out of the hole with a jarring string. Essentially, this is a hammer that is used to beat the packer out. The jarring operation proceeds until either the jars quit or the mandrel is jarred out of the packer. In either case, a milling assembly must be run, which can take more than one trip to complete. Experience has shown that recovery of stuck packers by conventional means is very difficult and time consuming. On some deepwater floating rigs with day rates from $200,000 to $500,000, a stuck packer that takes days to recover can have a catastrophic cost. Recent downhole vibration and impulse studies have shown that downhole impulses could be considerably more effective than jarring in retrieving packers and other point-stuck equipment. By imparting - impulses downhole to the stuck object, there is no need for a high-strength work string. The chances of pulling the mandrel out of the packer or sticking the packer tighter in the wellbore are greatly reduced. Impulses work independently from overpull, so it is ideal for horizontal or high-angle wellbores. Another advantage is that the work string does not have to be reciprocated as much as with a jarring string. When pulling out of a wellbore, a packer can get hung up on restrictions such as casing collars. Jarring strings cannot be reset unless the packer can be set down, which allows the jars to close and reset. A downhole impulse tool works only on fluid pumped through the tool, so it can be activated at any time by rigging up a pump line. There is no need to set down the string. This new method has been shown to be an effective alternative to conventional jarring tools. Cost savings can be substantial. This paper focuses on the development, operation, and applications of this technology. Case histories are examined in detail showing advantages over conventional means.