Method for Re-Stimulating Wells with Hydraulic Fractures

摘要

A method for re-fracturing of wells having perforated casing that were previously fractured is provided. The method employs degradable ball sealers having a density near that of the injection fluid such that high seating efficiency of balls on perforations is attained. The balls degrade at varying rates, so that some intervals are opened for fracturing while other intervals are still blocked by ball sealers. After fracturing of an interval, the interval may by shut-off by ball sealers that degrade at a much slower rate or that do not degrade. The method may be applied to proppant fracturing or acid fracturing.

主权项

1. A method for applying a multi-stage hydraulic fracturing treatment in a well having a plurality of perforations in casing, the casing extending through multiple intervals in the well, comprising:
injecting a fluid into the well at a rate above the rate required to reach fracturing pressure in at least one interval of the well; continuing injection of a fluid having a specific gravity and a first number of degradable ball sealers suspended in the fluid, the degradable ball sealers having a first degradation time and a selected specific gravity within a selected range of the value of the specific gravity of the fluid, the first number being selected to seat on and plug the perforations in a stage of a hydraulic fracturing treatment of the well; continuing injection of a fluid having a specific gravity and a second number of degradable ball sealers suspended in the fluid, the degradable ball sealers having a second degradation time and a selected specific gravity within a selected range of the value of the specific gravity of the fluid, the second number being selected to seat on and plug the perforations in a separate stage of a hydraulic fracturing treatment of the well; allowing time for the ball sealers in the first or the second interval to degrade to produce a single perforated interval where at least some of the ball sealers placed in the perforations have degraded; and continuing injection of a fluid so as to hydraulically fracture the interval in the well where ball sealers placed in the perforations have degraded.