Multi-string packers

Abstract

A multi-string packer for anchoring two or more non-concentric through tubes inside a larger pipe or casing (e.g. in an oil well). The packer can be deployed downhole, set, unset, and reset at least once without being withdrawn to the surface, despite the shearing of shear elements on each such operation. A lost-motion mechanism isolates the shear elements for the first packer resetting (the second setting) from packer-setting shear forces applied to the shear elements for the first packer setting, to preserve the second setting shear elements until the packer is actually required to be set for a second time. Similarly, another lost-motion mechanism isolates to shear elements for the second packer unsetting from the packer-unsetting shear forces applied to the shear elements for the first packet unsetting, to preserve the second unsetting shear elements until the packer is actually required to be unset for a second time. As applied to a pump packer for use with a downhole electric pump, the invention enables the pump cable and completion string to be anchored and sealed inside the well casing. In the event of a wellhead fault necessitating unsetting of the packer, the string need only be withdrawn a short distance to access the wellhead fault for its repair, and then returned downhole that short distance only, since the packer can be reset at least once without being withdrawn to the surface. This avoids the need to withdraw the entire string to refurbish the packer for a second setting.