Method and multi-purpose apparatus for control of fluid in wellbore casing

Abstract

A downhole apparatus is described as having an upper mandrel shearably connected to a lower mandrel by a first set of shear pins. Each of the mandrels has an elastomeric cement plug formed around the mandrels. A sleeve is shearably connected within the lower mandrel. The operation of the apparatus, which includes a method for controlling the flow of fluid out of the end of a tubular string, involves dropping a first small diameter ball from the earth3 s surface. The ball is sized such that it travels through the upper mandrel and settles into the sleeve which is connected within the lower mandrel. By increasing pump pressure at the earth's surface, the lower mandrel is separated from the upper mandrel by shearing the first set of shear pins. After the separation of the lower mandrel from the upper mandrel, by further increasing the pump pressure at the earth's surface, a second set of shear pins are sheared and the lower mandrel can be pumped down to the bottom of the tubular string against a float collar or other plug landing surface. This enables the fluid within the tubular string to be pumped out of the lower mandrel into the earth borehole. When it is desired to separate the upper mandrel from the tubular string, the second, larger ball is dropped from the earth's surface and is seated within the upper mandrel. By further increasing the pump pressure, the upper mandrel is separated from the tubular string and can be pumped down against the lower mandrel.