A new non-polymer in-situ gelling system has been developed for reservoir water control treatments. This paper includes the results of a series of key laboratory tests in characterizing this system for practical well treatment designs.
The system comprises two to three chemicals which are readily soluble in most field mix waters and seawater. The fluid has a low viscosity close to that of the water, and can be pumped at any rate. The treatment is a simple single slug injection process using ordinary field mixing and injection equipment. In the rock formations, the injected fluid system forms a semi-solid gel which will transform into a solid phase after a time period. Typically, the treated formation permeability reduction is 50 folds or 98%.
The microscopic pore blocking efficiency as tested by core flow experiments can be correlated with the gel strength which is expressed in term of gel extrusion pressure gradient (psi/ft) as measured by a core plug test. This enables the treatment fluid penetration requirement calculations using the near wellbore pressure gradient values during the production or injection as input data instead of a blind assumption on a certain radial penetration.
Excellent fluid flow selectivity in the water-out layer has also been demonstrated by many laboratory bi-core flow experiments modelling a typical two-layer reservoir.