Efficient mud removal, filter cake removal and formation clean-up are critically required for well cementing, production and injection wells drilled with non-aqueous mud. Conventional surfactant clean-up system requires a turbulent flow and large volume to solubilize residue efficiently. Unsuitable surfactant system may cause emulsion blockage and oil-contamination in the completion brine, which consequently leads to a reduction in oil production rate. A new potential method to overcome these problems with higher efficiency to remove non-aqueous mud and filter cake is NanoEmulsion technology. This technology able to reduce the oil-water interfacial tension (IFT) down to < 0.001 mN/m, solubilize much larger amount of oily hydrocarbons without any mechanical stirring needed. This paper elucidates the potential of NanoEmulsion technology in removing non-aqueous based mud and filter cake during wellbore cleaning through laboratory scale set-up at ambient and HTHP conditions. The impact of temperature, pressure, mono- and divalent electrolytes, bridging agent such as calcium carbonate, acidity and polymers (Xanthan Gum and HEC) have been studied. It was found that the NanoEmulsion is effective in removing non-aqueous mud in all studied conditions at tested duration of < 10 minutes. The cleaning mechanism proposed are: (1) instantaneously reducing interfacial tension between oil-water and oil-solid surfaces, (2) emulsify and solubilized oil content, (3) facilitate wettability and allowing water molecules to penetrate in-between oil and solids surfaces, causing the oil to spontaneously repel from the hydrophilic solid surfaces, and (4) separation of oil from water and solids. This enables the recycle of the oil content which is free from solids. NanoEmulsion technology can be incorporate with acid to simultaneously dissolve calcium carbonate bridging agent and solubilize the oil in the filter cake. In addition, it is free from benzene, toluene and xylene (BTX), synthesis from bio-degradable natural sources, non-toxic, easy to handle, and 100% biodegradable.

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