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Conventional thinking within many companies dictates that any additive used in a drilling or completion fluid system to drill the reservoir section must be 100% soluble in the hydrochloric acid (HCl) typically used in the post-drilling well cleanup. Specifically, as any solids added to the fluid system invade into the permeability of the rock being drilled, pumping acid is a common approach to reduce the damage all-too-frequently resulting from the invasion of calcium carbonate (CaCO3) bridging agents and other solids.
A Different Approach
Wellbore Shielding® offers a field-proven alternative to maintaining formation integrity. This non-damaging technology comprises an ultra-low invasion additive that prevents solids in the fluid system from invading the permeability.
While safeguarding the formation’s permeability, our Wellbore Shielding additives also are more than 60% soluble, are resistant to shear degradation, and maintain their size and shape. Wellbore Shielding additives are mixed in the active mud system at concentrations significantly lower than CaCO3 and other bridging agents. During the drilling process, the uniquely formulated additive quickly deposits a thin, tough and impermeable barrier through that greatly reduces formation damage. As confirmed in independent lab tests, our Wellbore Shielding additives deliver high return permeability with low flow initiation pressures in both solids-free and weighted fluid systems.
The Wellbore Shielding Mechanism
Well productivity depends on protecting the rock permeability to allow maximum hydrocarbon flow. Reservoir pores, however, often become saturated with mud filtrate or plugged by drilled solids or even the bridging materials intended to prop them open, resulting in formation damage and restricted production capacity.
Alternatively, as overbalance pressure induces wellbore fluids to enter rock pores or existing and induced microfractures, the ultra low-permeability layer of plates or “shields” laid down by Wellbore Shielding additives reduces any further invasion of solids or fluid. Since the shields are deformable, as the pressure rises, the plates become increasingly compressed, further reducing the barrier permeability. The benefits of this approach are magnified with the commencement of production, as the inflow of the well causes the filter cake to pin-hole and lift off the wellbore with extremely low differential pressure.
Lab data and field results demonstrate the FLC 2000® and Star Shield® families of wellbore stabilizers provide lower fluid invasion than conventional fluids, including those incorporating sized calcium carbonate. The broad size distribution and compressibility of these specialized additives are proof positive that one product can seal a wide range of pore sizes and microfractures. Consequently, unlike with calcium carbonate, the standard requirement to modify the particle size distribution (PSD) of the product as drilling progresses from one formation with one type of permeability to another, is no longer needed.
Numerous independent formation damage studies likewise have confirmed that this approach achieves exceptional return permeability. The “shielding” methodology differs remarkably from the plugging approach of CaCO3 and other solids used to seal the wellbore. What’s more, since acid clean-up jobs are not required to remove the Wellbore Shielding material, well costs and the time to commence initial production are reduced appreciably.