Cylindrical gate valve apparatus and method

Abstract

A safety valve is disclosed which may be installed on an offshore wellhead above the tubing head and below the Christmas tree. The valve has a housing with upper and lower vertical passages and a lateral housing passage. A cylindrical gate is disposed within the lateral passage and includes a 'T' shaped passage therein. The gate may be moved laterally and angularly within the lateral passage. During completion or workover of the well, the gate is moved laterally until the upper and lower vertical passages are in full open communication to run drills, hangers or other large diameter devices into the well via a BOP which may be attached to the top of the housing. During normal production, the gate may be laterally moved into the intersection of the vertical and lateral passages and the small through head part of the 'T' passage serves to provide a vertical flow path through the production bore which is sealed off from the larger upper and lower vertical passages. Flow through side outlets in the housing is possible through the base of the 'T' passage. The gate may be angularly moved to have production to the lateral outlets via the head part of the 'T' when the base part of the 'T' is aligned with production tubing. Should the need arise, the valve may be angularly rotated to a position where the fluid flow path of the production tubing is completely shut in.