Plugging thief zones and fractures by in-situ and in-depth crystallization for improving water sweep efficiency of sandstone and carbonate reservoirs

摘要

The present invention relates to methods and compositions that can be used to delay crystallization of a treatment solution so that thief zones or fractures are plugged in subterranean formations at a substantial distance from a wellbore. A supersaturated sodium aluminate solution, or other solutions, is introduced into the reservoir. The solution is relatively stable in the supersaturated state. Crystallization, or de-stabilizing the solution, can be controlled, which in turn plugs the thief zone or fracture at a designed point of time. By controlling the time that crystallization starts, that is, the induction period, thief zones that are located at a substantial distant from the wellbore can be plugged.

主权项

1. A process of treating a subterranean formation such that thief zones or fractures are plugged in the subterranean formation at a substantial distance from a wellbore, the process comprising the steps of:
introducing into the subterranean formation a sodium aluminate solution having a pH in a range of from 8 to 14 consisting essentially of NaAl(OH)4 and a delayed crystallization additive; contacting the subterranean formation at a substantial distance from the wellbore with a supersaturated sodium aluminate solution having a pH in a range of from 8 to 14; and precipitating crystalline gibbsite onto a surface of the thief zones or fractures from the supersaturated sodium aluminate solution; where the sodium aluminate solution is operable to form gibbsite (Al(OH)3 s) within the subterranean formation while the sodium aluminate solution has a pH in a range of from 8 to 14 where the supersaturated sodium aluminate solution forms from the introduced sodium aluminate solution in the subterranean formation, and where the delayed crystallization additive is operable to delay crystallization of the gibbsite in the supersaturated sodium aluminate solution such that the thief zones or fractures are plugged with the crystalline gibbsite precipitated from the supersaturated sodium aluminate solution.