| When a well is drilled, a filter cake is formed from solid materials such as carbonate (drilling fines or material added to reduce fluid loss to the formation and control mud weight) and polymers used to viscosify the fluid and control fluid loss. The filter cake significantly reduces permeability at the wellbore face and impedes flow. In the diagram on the right, a cross section of the filter cake is shown. The formation is shown in grey and the filter cake shown as a mixture of carbonate (white) lining the inside of the wellbore closely associated with polymer (lilac). |
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| Effective clean up of filter cake is required to permit the well to perform at its maximum potential. Acidizing with mineral acids (illustrated on the right) generally produces wormholing but still leaves significant damage due to residual polymer and carbonate. It is very difficult to effectively treat long horizontal wellbores with mineral acids because of poor zonal coverage and wormholing. |
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Enzyme breakers alone can effectively remove polymers
(see diagram to right) and restore some permeability but will not dissolve
carbonate weighting material or carbonate fines produced by the drilling
process. Residues of this material will still coat the inside of the
wellbore.
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Use of Arcasolve™ alone can
effectively remove drilling fluid damage. For some drilling fluid systems,
incorporation of enzyme breakers may be beneficial. Some matrix stimulation
of the formation leading to a negative skin may occur at the same time. The
diagram on the right illustrates how Arcasolve™
treatment can lead to the effective removal of carbonate material resulting
in an undamaged wellbore.
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