emulsion fl uids present a frustrating cleanup challenge. A water wetting combination of high rate fl ush of Dow surfactant, glycol ether and specialty solvent followed by a mineral acid, organic acid or chelant can often eff ectively 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 fl uids can contain ultrafi ne solids that can increase the likelihood of damaging penetration of whole fl uid to near wellbore microfractures and higher permeability clastics. The result can be wettability change resulting in essentially diffi cult-to-penetrate, oil-wet cake within the reservoir. If near wellbore micro-fractures extend to the reservoir far-fi eld, deep damage to

otherwise producible rock may occur.Simple glycol-ether “pills” are often used to treat wettability changes; however, more eff ective 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 SolutionsAssure 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 fl uids and asphaltic crudes can be especially diffi cult to remove from fracture surfaces and tubulars. Dow’s EMBARK™ Subsurface Cleaning Solutions can help by: • Safely and eff ectively 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 fl uids do create oil-wet fi lter cake that is diffi cult 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.Off shore 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 fi eld, prepare, maintain and recycle nonaqueous drilling fl uids for use in further drilling operations. The invert emulsion drilling fl uids prepared by these plants contain rigorously emulsifi ed calcium chloride brine in a mineral oil or synthetic base fl uid. The emulsifi ers 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 eff ective, 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 effi ciently.

EMBARK™ SolutionsDow’s EMBARK™ Subsurface Cleaners, which include a range of non-ionic and anionic surfactants, glycol ethers, specialty alcohols and chelants, are ideally suited to address the cleaning challenges imposed by invert emulsion drilling fluids and asphaltic crudes. Applied either alone or in a variety of formulations, these comprehensive solutions can address any subsurface cleaning challenge.

Surfactants – EMBARK™ SF Surfactants alter the wettability of oil mud or crude oil-wet surfaces and make contaminant removal easier and more efficient. Dow also offers surfactants custom-suited for use in harsh environments or that meet stringent HSE and regulatory mandates.

Co-Solvents: Glycol Ethers and Specialty Alcohols – Dow produces the widest variety of mutual solvents in the industry, which, in conjunction with EMBARK™ Surfactants, create powerfully hydrotropic solutions to improve water wetting of oil-laden surfaces.

Supplemental Cleanup Chemistries – For additional cleaning assistance, Dow also offers EMBARK™ CH Cleaners. When used as neat, neutralized salt solutions or as part of a surfactant wash, these supplemental cleaners can remove calcium carbonate or barite and prevent deposition of iron salts without damaging production screens.

Product Line Surfactant Type Attributes and Application

CELLOSOLVE™/ CARBITOL™/ DOWANOL™ Glycol ether Very low surface tension surfactants with low VOC and unsurpassed hydrotropic characteristics. High flash-point coupling agent with 100% water solubility.

isopropanol, n-propanol, isobutanol, n-butanol, n-pentanol, amyl alcohol, methanol, 2 methyl butanol, methyl isobutyl carbinol, 2-ethyl hexanol, diisobutyl carbinol

Alcohol Economical and effective alcohols for various belowground cleaning applications.

Product Attributes and Application

EMBARK™ CH 100 Increases surfactant efficiency by removing calcium and magnesium from dilution water. Non-acidic non-damaging dissolver of insoluble divalent and polyvalent salts. Excellent supplemental cleaner of ferrous metals. Prevents re-deposition of divalent and polyvalent precipitates from hard wash water.

EMBARK CH 120 Highly efficient calcium carbonate dissolver.

EMBARK CH 150 Formulated barite dissolver

The Dow Chemical Company

NOTICE: No freedom from infringement of any patent owned by Dow or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, theCustomer is responsible for determining whether products and the information in this document are appropriate for the Customer’s use and for ensuring that the Customer’s workplace and disposal practices are in compliance with applicable laws and other governmental enactments. Dow assumes no obligation or liability for the information in this document. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

This guide is designed as a general product overview. Please contact your local Dow representative for up-to-date, detailed technical information, including registrations and use limitations, and to discussIndividual applications or requirements.

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