Importance

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Abstract

A latch is adapted to be connected to a tubing string and will snap into a packer disposed in a wellbore. A predetermined first number of pounds is required to snap the latch into the packer and a predetermined second number of pounds, greater than the first number, is required to pull the latch out of the packer in the wellbore. In order to maintain constant the first and second number of pounds, the latch has the following special characteristics. The latch has a plurality of flanges separated, respectively, by a plurality of gaps, that snap into the packer, each flange having external threads disposed around its periphery, each thread including an engaging surface and a disengaging surface, an angle between the surface of each disengaging thread relative to a vertical being in a range from 20 to 28 degrees. An elastomeric barrier occupies the gap between adjacent ones of the flanges. A distance exists between each of the flanges and an adjacent snap latch body, the flanges being adapted to bend and disengage across the distance, the distance being 21/2 to 3 times a particular distance that is required for the flange to snap out of the packer in the wellbore when an operator pulls upwardly on the tubing. The geometry of the flange is selected to minimize a lever arm extending between an axially applied force applied axially to the external threads and a center of gravity of the flange at the base, the lever arm being approximately equal to zero. An outer diameter of each flange of the latch is greater than an inner diameter of an inner mandrel of the packer plus a tolerance stackup. The number of external threads on the periphery of each flange is minimized in order to further minimize the number of disengaging loads created when the latch is pulled out of the packer by the operator at the wellbore surface. This will assist in establishing as a certainty the second number of pounds of pulling force which is required in order to pull the tubing and the snap latch of the present invention out of the packer in the wellbore and the first number of pounds of pushing force required to snap the tubing and the snap latch into the packer in the wellbore.

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First Claim