Method and apparatus for stimulating hydrocarbon wells

A method of completing a hydrocarbon well extending from a surface location and penetrating at least one hydrocarbon bearing zone, comprising cementing a casing string in the well through the at least one zone, the casing string including a series of pipe joints having a predetermined minimum internal diameter and a flapper valve assembly having an internal diameter at least as large as the casing internal diameter and providing a tubular housing comprising part of the casing string and being at a location between the hydrocarbon bearing zone to be stimulated and the surface location, a flapper valve member movable between a first inoperative position allowing upward and downward flow through the casing string and a second operative position preventing downward flow and allowing upward flow through the casing string and a manipulable device for holding the flapper valve member in the first inoperative position;

• stimulating the hydrocarbon bearing zone with the flapper valve member in the first position;
• manipulating the device and positioning the flapper valve member in the second position thereby isolating the stimulated hydrocarbon bearing zone;
• stimulating a hydrocarbon bearing interval closer to the surface location than the flapper valve member;
• and
• placing the well on production and allowing hydrocarbons to pass through the flapper valve assembly to the surface location.

A flapper valve assembly comprising

• a tubular housing having an upper end, a lower end, a pocket between the upper and lower ends for receiving a flapper valve member and an upwardly facing valve seat;
• a flapper valve member mounted for movement between a first valve member position in the pocket for allowing upward and downward flow through the valve assembly and a second valve member position abutting the valve seat and preventing flow toward the lower housing end;
• and
• a shiftable sleeve for holding the flapper valve member in the first position while closing the pocket and for releasing the flapper valve member for movement to the second valve member position, the shiftable sleeve having an end for sealing engagement with the upwardly facing valve seat when the flapper valve member is in the first valve member position, the sleeve and sleeve end sealing the pocket against entry of debris.