Traditional chemical methods for removal of non-aqueous fluid (NAF) filter cake and internal formation damage use acids, solvents and mutual solvents mixed in clear brine. In some cases, this conventional technology gives good results; but, in other instances, the results can be disappointing.

A new generation of single-phase microemulsion stimulation fluids has been developed for removal of filter cake and formation damage in wells drilled with NAF systems. The development work included the design of microemulsion formulations, determination of the destruction rate of the filter cake with additives that prevent massive completion fluid losses, and evaluation of return permeability for injector and production wells.

The driving mechanism of this technology is to obtain a near-zero free energy state between the novel microemulsion and the NAF filter cake or damaged formation face which promotes incorporation of the oil into the microemulsion and spontaneously reverses the wettability of the filter cake particles, disaggregating them so they are no longer damaging. The laboratory results described in this paper show that the novel microemulsion design delays its spontaneous action long enough to permit well completion operations without experiencing massive losses to the formation. Permeability data obtained demonstrate that this new technology is highly effective for enhanced water-injection and productivity.

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