Basic calculations using the Darcy equation reveal three important facts.1 First, gelants and similar fluid blocking agents can penetrate a significant distance into all open zones. Second, an acceptable gelant placement is much easier to achieve in linear flow than in radial flow. Third, if flow is radial, then hydrocarbon-productive zones must be protected during gelant placement. These facts mean that excess channeling and water production problems can be treated much more readily if they are caused by linear-flow phenomena, such as vertical fractures, fractured systems, or flow behind pipe. Even so, placement of blocking agents is very important in linear flow as well as in radial flow. When flow is radial (e.g., unfractured wells), field engineers would be well-advised not to apply blocking-agent treatments in wells with radial flow unless hydrocarbon productive zones are protected during placement of the blocking agent.

A strong need exists for the development of new ideas to optimize placement of gels and other blocking agents, both in linear and radial systems.