Patent CA-2227125-A1 (CA)
Inventor: SCOTT ROBERT LINDSAY
IPC: E21B31/12
Filed: 1998-03-27
Abstract: The pump jack at a producing petroleum well actuates a steel rod which extends down the length of the well tubing to a bottom hole pump. There are two types of rod; (1) non-continuous round rod which is assembled in 32 foot lengths, and (2) continuous tapered elliptical or round rod, which is extended and recovered from a reel. This application is for a tool which will service the non-continuous round rod only. When round rod is installed in a well tubing, plastic "centralizers" are heat-bonded to the shaft of the rod at specified intervals. These centralizers serve two purposes; (1) they act as a spacer between the rod shaft and the well tubing, keeping the rod centred and preventing it from contacting the tubing, (2) they act to clean the wall of the tubing whenever the rod is installed or dismantled from the well. The centralizes consists of an inner cylinder heat-bonded to the round rod, and an outer cylinder which rides flush against the wall of the well tubing. Joining the inner and outer cylinders are four vanes. There are gaps between the vanes to allow passage of gases and fluids as the rod is raised or lowered inside the tubing. Occasionally round rod will break and the broken extension must be recovered from the well tubing. This is done with a recovery tool which is dispatched down the well tubing on the end of a recovery tubing to "fish" out the bottom segment of the broken rod.  Should the rod break, conventional recovery methods use a recovery tool (commonly referred to as an "overshot" or "fishing" tool), designed to recover the round rod by grasping the rod at a point just below the break and thereby pulling the broken extension up and clear of the tubing. However, when a break occurs at or very close to the upper rim of the centralizes, the length of rod shaft available upon which the fishing tool can obtain a purchase is insufficient. Without the tool described in this application, the normal practice is to remove the well tubing itself and recover the broken rod. This is both time consuming and expensive. The tool discussed in this application is a new design specifically applicable to the situation described. Instead of a self locking grip mechanism which is used on the conventional rod recovery tool, this tool has four equally spaced fingers, with delta shaped heads. As the tool is lowered over the centralizes, it is slowly rotated. The fingers drop into the spaces along the longitudinal axis of the centralizes, until they have completely penetrated the length of the centralizes. At that point an outer sheath consisting of four locking fingers are dropped over the penetrating fingers, forming a closing action that locks the inner fingers so that the hooks on the end of the fingers are firmly positioned on the bottom diameter of the inside cylinder of the centralizes. Upward force is exerted on the tool, and the centralizes with the pump rod attached is slowly lifted up about two feet. At that point the full weight of the remaining pump rod is now held by the centralizer. The heat bond breaks, and the centralizer is now clear of the pump rod. It is then removed from the well, and the exposed well rod can now be removed with a conventional tool.