APPARATUS AND METHODS FOR INHIBITING A SCREEN-OUT CONDITION IN A SUBTERRANEAN WELL FRACTURING OPERATION

摘要

A subterranean well fracturing system comprises a downhole well string having installed therein initially closed upstream and downstream sliding sleeve valve assemblies each openable to provide fracing fluid discharge outlets through well string side ports to an associated subterranean fracing zone. To inhibit an undesirable screen-out condition during formation fracturing, specially designed apparatus and methods are operative to sequentially (1) block the downstream valve seat, (2) open the blocked downstream valve seat using pressurized fracing fluid, (3) partially block the upstream valve seat, (4) open the partially blocked upstream valve seat using pressurized fracing fluid, a portion of which is flowed through the partially blocked upstream valve seat, and then (5) unblock the partially blocked upstream valve seat to permit a full flow of pressurized fracing fluid therethrough. In this manner, pressurized fracing fluid is simultaneously delivered to two fracing zones to inhibit a screen-out condition in the well string.

主权项

1. Apparatus for inhibiting the creation of a screen-out condition in a subterranean well fracturing operation utilizing a downhole tubular well string having, on a sliding sleeve valve assembly installed therein, a seat longitudinally shiftable between open and closed orientations within the well string, the seat having an opening through which pressurized fracing fluid may be flowed, said apparatus comprising:
a valve actuating member being droppable through the tubular well string onto the movable seat in its closed orientation and being constructed and configured to thereafter sequentially:
(1) partially block the seat opening in a manner permitting a limited flow of pressurized fracing fluid therethrough,(2) cause the pressurized fracing fluid to slide the movable seat to its open orientation, and then(3) shear through the movable seat opening to unblock it.