Sealing by ball sealers

摘要

In downhole treatments in the oilfield, ball sealers seated in perforations may not fully seal and may leak fluid through gaps and asperities between the balls and the perforations. A method is given for improving the sealing of ball sealers in perforations by adding a sealing agent that forms a plug in the gaps and severely restricts or eliminates fluid flow. The sealing agent is preferably degradable or soluble, malleable fibers slightly larger than the gaps. Optionally, the particles may be non-degradable, rigid, of different shapes, and smaller than the gaps but able to bridge them. Mixtures of sealing agents may be used. The sealing agent may be added with the ball sealers, after the ball sealers, or both.

主权项

1. A method for sealing holes in a casing in a cased well penetrating a subterranean formation, comprising:
injecting ball sealers and a separate sealing agent comprising particles into the casing of the cased well so as to form a plug including a combination of a ball sealer and particles that inhibit fluid flow through a hole in the casing in which the ball sealer is seated, wherein the particles comprise fibers having a length from 5 to 25 mm; wherein the sealing agent is injected at a rate between 0.013kg/perforation and 0.076 kg/perforation and wherein at least a portion of the sealing agent is injected with the ball sealers; and, wherein some or all of the particles have at least one dimension smaller than a gap between an outer boundary of the ball sealer and the casing, or, some or all of the particles have at least one dimension larger than a gap between an outer boundary of the ball sealer and the casing.