A laboratory study of acid formulation to remove filter cake in Wells

Abstract

Drill-in fluids (DIF) are relatively clean compared to conventional mud systems and are designed to minimize the effects of drilling fluid damage when drilling through the pay zone. Drill-in fluids are typically formulated to deposit a high quality, relatively impermeable filter cake, which seals the wellbore and minimizes fluid leak off into the formation. In theory, such cakes maybe removed by the produced fluids and from sufficient drawdown in the production direction. Typically, the part of the wellbore that has been exposed to the drill-in fluid for the longest period is the most damaged. If left in place, the filter cake can significantly reduce the production rate of the well, cause a poor production profile and reduce the efficiency of the completion. Production complications such as gas or water coning can also arise. Water-based DIF comprised of carbonate particles and polymers are widely used in the industry. Calcium carbonate particles act as a weighting and bridging agent whereas polymers such as starch and xanthan provide appropriate rheological properties to the DIF. Such DIF forms filter cakes containing carbonate, polymers and rock fines arising from drilling.