Laboratory tests to evaluate and study formation damage with low-density drill-in fluids (LDDIF) for horizontal well completions in low pressure and depleted reservoirs

Abstract

The increasing number of open hole horizontal well completions in low-pressure and depleted reservoirs requires the use of non-damaging low-density drill-in fluids (LDDIF) to avoid formation damage and realize optimum well productivity. To address this need we have formulated new LDDIFS with specific density lower than 1.0 sg (8.34 ppg) specifically to drill and complete low pressure and depleted reservoirs with minimum formation damage and maximum production. These materials exhibit typical drilling fluid characteristics, allowing the well to be safely drilled (0 required well depth but also perform as completion fluids, lessening formation damage to a greater extent than fluids with greater density and higher wellbore pressures. The new LDDIF incorporates low-density hollow glass spheres (HGS) to allow near-balanced drilling in low pressure and depleted reservoirs. The LDDIF uses potassium chloride (KCI) brine as the base fluid because of its low density and inhibition of clay hydration and employs low concentrations of the HGS so that fluid rheology is not altered. We have conducted extensive laboratory testing to compare performance of the HGS LDDIF with that of conventional horizontal well DIFs. Experiments consisted of permeability regain tests on unconsolidated sands with sand control screens. Test variables included temperature, concentration of drill solids cleanup technique and HGS concentration. Test results have shown that the new fluids are up to 50% easier to remove from the wellbore formation faces and provide higher productivity than higher density fluids. Such results indicate that higher well productivity from wells with less impairment would offset any added costs of HGS additives in the fluids.