Method and apparatus for surge reduction

摘要

Improvements are disclosed in surge reduction tools for running in casings or casing liners downhole with the ability to restore circulation in the event a tight hole condition is encountered. The improved tool includes among other features 1.) an axial indexing apparatus which allows the valving sleeve to be moved downward in predetermined increments to allow alternate closing and opening of the vent ports, 2.) a camming sleeve and Bellville spring washers which provide the surge reduction tool with a more predictable release pressure than has heretofore been available, 3.) a dart directing sleeve which has a smaller, smoother bore than the drill string and provides the important function of aligning the dart before it lands in the seat so that the dart resistance when passing through the seat is minimized, and 4.) chevron seals arranged in the housing above and below the vent port which reduces the potential for hydraulic lock and provides a seal mechanism that is more reliable while running in downhole conditions.