E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
E21B 31/12 (2006.01)
Patent
CA 2167851
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 rod, which is extended and recovered from a reel. Both types of rod are currently in use; the continuous elliptical rod is a more recent design and is gradually replacing the more common but older round rod. Occasionally the rod will break and the broken extension must be recovered from the well casing. This is done with a recovery tool which is dispatched down the well casing on the end of a recovery tubing to "fish" out the bottom segment of the broken rod. Present recovery methods use a recovery tool (commonly referred to as an "overshot" or "fishing" tool), which was designed for round rod and is not ideally suited for elliptical rod because the tool gripping mechanism does not conform to the elliptical cross section of the rod. Recovery attempts often fail using the present methods, particularly on elliptical rod. Failures usually mean that the entire well casing may have to be recovered at some considerable expense and down-time for the well. The tool discussed in this application is an improvement on the current tool which makes recovery operations much more reliable and faster. It does not rely on the technological methodology of the present recovery tool, but rather uses a superior concept which assures highly reliable performance under all conditions. It is specifically designed for recovery of elliptical rod, but is also completely suitable for recovery of round rod. The key to the superior performance of this tool is that it provides for equal distribution of tensile force around the diameter of the rod shaft. This prevents breakage of the rod, or the tool, or both, from distortions in the distribution of pulling force. This is achieved through the use of: (1) self-locking "slips" which conform to the diametrical profile of the rod and will not allow release of the rod even if the tool itself fractures from excessive tensile pull, and (2) the use of a shoe guide specifically designed to align the elliptical or round rod within the clenching cavity of the locking slips, and (3) the interchangeability of the guide sleeve and locking slips for recovery of either round rod or elliptical rod.
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