Sweep Improvement and Profile Modification Using Foams and Gels: Technology, Recent Advances, and a Critical Assessment of Field Case Histories
Braddock, Jonathon Lyall
Engineering Honours Degree 2007
University of Adelaide
Following a discussion of foams and gels with regard to their basic properties, their utility to the concepts of sweep improvement and profile modification are evaluated in a reservoir engineering perspective. A review of real world experiences provides valuable insight into the issues.
Three principles infuse the discussion:
1. Reservoir engineering is ultimately pressure management: most reservoir Key Performance Indicators have pressure at their heart.
2. In the context of sweep and profile, practical means are required to allow the engineer to diagnose and respond to the problem(s) mitigating profitable hydrocarbon production.
3. Marginal benefits of any treatment applied to a reservoir must exceed its marginal costs, with any treatment evaluated on a whole of operation basis.
Sweep and profile issues may arise at the well itself, in the near well-bore region, or deeper in the reservoir. Foams and gels are each useful deeper in the reservoir, but closer to the well where the stresses increase, strong gels are needed.
Initial uses of foams and gels were as blocking agents: the foam or the gel took position and stood dumb guard against the advancing fluids. To be selective about which fluid was blocked required careful attention to placement.
Injection well treatments hazard an injection well but require a detailed knowledge of the reservoir and suffer from cross-flow.
Cross-flow within the reservoir is an issue that needs further research to develop treatments of practical use.
Mobility modification with foams and gels applied via an injection well aims to improve the sweep of fluids within the reservoir.
Production well treatments require less detailed information on the deep reservoir environment but run the risk of immediate loss of production if things go wrong.
Disproportionate Permeability Reduction (DPR) gels offer some hope of blocking the unwanted fluids from entering the production well, while allowing the passage of valuable oil.
Fractures have most commonly been treated with gels but lately, foam gels have provided a cheaper alternative.
It is found that foams and gels offer economically attractive means of increasing oil recovery.