Mud-induced damage is highly pronounced in horizontal wells due to the longer period of exposure to drilling mud and low draw-down pressure. Enzyme-based cleanup fluids are preferred for filtercake removal applications, especially in horizontal wells due to their several advantages compared to conventional cleanup fluids. The advantages include low reactivity, less corrosivity, more environmentally safe, polymer-specific enzyme breakers, and ultimately homogenous filtercake removal coverage. Most enzyme-based cleanup fluids are limited to low temperatures.

In this study, extensive lab work was conducted to evaluate an enzyme-based/in-situ generated organic acid cleanup fluid for a water-based mud at a temperature of 250°F. The experimental work included coreflood experiments, HT/HP filter press, and see-through cell. Analytical techniques, including ICP, XRD, EDXRF, IFT, and iodine tests, were used to assess the interaction of the cleanup fluid with filtercake components.

The results showed that the enzyme/in-situ organic acid generated cleanup system was effective at degrading filtercake for a water-based mu field sample, which was reflected in the obtained return permeability of nearly 83%. Iodine tests confirmed that the enzyme was able to degrade the starch present in the filtercake. The surface tension of fluid is generated due to the interaction of the enzyme-based breaker with the filtercake at 250°F and for 48 hours was 31.11 dynes/cm at 22°C, which indicates that this system can help to prevent water blockage problems, especially for gas tight formation. This paper will discuss in detail all experimental results and findings.

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