Highly Dispersive Shale Inhibited by High-Performance Water-Based Fluid System | Schlumberger
Tech Report
Location
Norway, Europe, Offshore
Background

An operator sought to expedite drilling an exploration section in a zone with highly dispersive shale. When drilling an offset well with standard water-based mud, 2 days NPT had been spent cleaning out the 8 1/2-in section before logging. Cuttings samples from the offset well showed clearly a lack of inhibition that worsened with depth.

To solve the problem and reduce NPT for the next well, M-I SWACO recommended HydraGlyde Optima flexible high-performance water-based drilling fluid system based on accretion laboratory test results. The results showed a reduction in accretion of about 50%, from 33% to 18%.

No major challenges or fluid-related problems were encountered drilling the problematic 8 1/2-in section. The fluid viscosity and other fluid parameters remained very stable throughout the section.

Products Used

Highly Dispersive Shale Inhibited by High-Performance Water-Based Fluid System

Optimized inhibition achieved with flexible fluid system, minimizing drilling time and risk through dispersive formation in an environmentally sensitive area

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Top: Cuttings samples from the offset well from left at 4,265 ft [1,300 m] and at right 5,249 ft [1,600 m]. Bottom: Sample from 5,249 ft [1,600 m] in an actual well drilled with the HydraGlyde Optima system.

Overall, cuttings integrity was good and the high-performance system provided sufficient inhibition. As the section drilled also explored the sand reservoir below the troublesome dispersive shale, the inhibition characteristics of the fluid ensured a stable open hole during the static period when logging.
Products Used

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