Abstract: The present invention provides a drop ball sub that may be used to drop a large ball having an outer diameter larger than the inner diameter of a restriction in the wellbore such as the running tool used to run a first casing string through a second casing string. A smaller ball is used to control dropping of the large ball. The smaller ball has an outer diameter smaller than the restriction. The drop ball sub of the present invention may be used to operate any downhole tool that would benefit by receipt of a large ball. By dropping a larger ball, in one use of the invention larger valves can be controlled in the float equipment that provide a larger fluid flow path. A larger fluid flow path reduces surge pressure and enables the system to handle more debris. The present invention provides a system that preferably provides for a diverter tool above the running tool and a diverter tool below the running tool.

Abstract: A velocity sensor is disclosed comprising a housing, a ferromagnetic fluid which substantially fills the housing, and a magnetic proof mass suspended in the ferromagnetic fluid. The magnetic proof mass has a cylindrical center portion and end portions which taper from the central portion to the poles of the proof mass.

Abstract: Method and apparatus are disclosed for use in cementing a tubular member which is run into a borehole using a drill string. A landing collar is attached to the tubular member near the bottom of the tubular member, and the landing collar has an opening at least five inches in diameter. A liner wiper assembly is releasably suspended from the drill string. The liner wiper assembly comprises a lower liner wiper plug comprising float valves and an upper liner wiper plug. With the method and apparatus of the present invention, plugging problems are minimized.