emulsion fluids present a frustrating cleanup challenge. A water wetting combination of high rate flush of Dow surfactant, glycol ether and specialty solvent followed by a mineral acid, organic acid or chelant can often effectively remove the injectivity barrier created by an invert emulsion mud cake. Reservoir Damage Remediation – Dow surfactant and co-solvent treatments have also been used to lessen the damage caused by loss of whole mud to a reservoir, occurring often in induced fractures in sands. Recycled invert emulsion drilling fluids can contain ultrafine solids that can increase the likelihood of damaging penetration of whole fluid to near wellbore microfractures and higher permeability clastics. The result can be wettability change resulting in essentially difficult-to- penetrate, oil-wet cake within the reservoir. If near wellbore micro-fractures extend to the reservoir far-field, deep damage to otherwise producible rock may occur. Simple glycol-ether “pills” are often used to treat wettability changes; however, more effective Dow formulations are available. A co-solvent combined with a Dow surfactant and specialty solvent will more readily penetrate damaged reservoir rock to restore original wettability, resulting in enhanced well productivity. This technique can be applied to clastics and fractured dolomites, as well as vuggy or karsty limestones. EMBARK ™ Subsurface Cleaning Solutions Assure well productivity and injectivity, and maximize life of production screens Oil, Gas & Mining Well Cleanup Challenges Extended reach and horizontal wells pose unique cleaning challenges to assure well productivity and prevent direct or indirect damage to production screens and reservoirs. The use of invert emulsion fluids and asphaltic crudes can be especially difficult to remove from fracture surfaces and tubulars. Dow’s EMBARK™ Subsurface Cleaning Solutions can help by: • Safely and effectively removing mud cake from reservoirs • Maintaining or restoring wettability characteristics of the rock • Minimizing initial skin development • Removing surfactant-laden oil-wet residue from open hole completions and tubulars • Remaining stable over the broadest possible temperature range • Meeting regional environmental regulatory expectations Oil-Wet Filter Cake Cleanup – Properly designed and formulated invert emulsion muds have been shown to be minimally damaging to most reservoir rock. However, even the best invert emulsion drilling fluids do create oil-wet filter cake that is difficult to penetrate with acids, acid precursors and chelants. Dow surfactants, glycol ethers and specialty solvents quickly convert oil-wet mineral-laden surfaces to a water-wet state for more complete and rapid dissolution by standard cleanup chemicals including hydrochloric acid, organic acids and ester acid precursors, as well as by traditional and low pH chelants and Dow-formulated barite dissolvers. Offshore injector wells that cannot be produced after drilling with invert Assisting Cleanup Operations in Liquid Mud Plants Liquid mud plants, which are common in nearly every working oil field, prepare, maintain and recycle nonaqueous drilling fluids for use in further drilling operations. The invert emulsion drilling fluids prepared by these plants contain rigorously emulsified calcium chloride brine in a mineral oil or synthetic base fluid. The emulsifiers are predominantly combinations of calcium soap and powerful surfactants of crosslinked amidoamines or imidazolines. These surfactants create vigorous oil-wet environments that cannot be easily broken and removed by a simple surfactant wash in the mud plant. EMBARK™ Cleaning Solutions provide effective, fast and predictable cleaning options in the liquid mud plant, keeping screens water-wet and free from residual oil buildup and helping plants run more reliably and efficiently.