Water-Soluble Silicate Gelants for Disproportionate Permeability Reduction: Importance of Formation Wetting and Treatment Conditions

摘要

Two commercial water-soluble sodium-silicate-based gelant systems,Systems A and B,were tested for their potential as Disproportionate Permeability Reduction(DPR)agents on Berea outcrop cores. The DPR experiments were conducted using a steady-state,twophase(oil/gelant)placement method to(a)ensure the presence of moveable oil and(b)quantitatively control the placement saturation conditions at which the silicate gel sets. The treatment performance was evaluated using pre-and post-treatment two-phase(brine/oil),steady-and unsteady-state permeability measurements. Bulk and core experiments showed that shrinkage of System B was significant in shortterm tests conducted at various temperatures. System A,on the other hand,formed longlasting,stable,rigid gels at corresponding temperatures. Tests conducted on water-wet long-core samples at relatively low formation watercut(WC)of 22% revealed no positive DPR effect. System A was also tested in oil-wet Berea cores which were treated chemically to alter their wettability. DPR treatments at the same WC as the pre-treatment conditions(22%)resulted in an effective DPR behavior. However,DPR treatments at 22% WC in cores with pre-treatment 78% WC were more effective resulting in a lower oil-phase residual resistance factor(RRFo)compared to the one from cases for which DPR treatments were conducted at the same pre-treatment WC.