ConocoPhillips
Through tubing P and A with bismuth alloys

Abstract:

Method of plugging a hydrocarbon well by a through-tubing technique are described. The method allows the tubing to be left in place. Only a short (<2 m) section is cut, milled, perforated, ruptured and expanded, or combinations thereof. A blocking device is sent downhole to block a bottom of the plug section, and bismuth alloy pellets dropped onto the blocking device. A heater is deployed to melt the bismuth alloy pellets. Next, the alloy liquid is allowed to cool and solidify. During solidification, the alloy expands and fills the section of well to be plugged or a portion thereof. Once primary and secondary barriers are in place, the well can be closed and the Christmas tree removed. A rock-to-rock plug can be set by removing or partially removing the tubular and outer casing, or just inner casing/tubulars can be removed if the exterior cement and casing are of sufficient quality.