Wellbore Stability

Forecast wellbore stability to avoid drilling-related failures

Many drilling-related failures are caused by unstable boreholes, whether these are caused by lost circulation, poor hole cleaning, or stuck BHA and casing. Schlumberger geomechanics experts pioneered a methodology to model and forecast borehole stability and to use this pre-drill knowledge in real-time, enabling operators to minimize formation-related drilling problems. Real-time drilling geomechanics enables identification of wellbore instability, along with the mode of failure and is critical in correcting and reducing the cost associated with it.

A wellbore stability forecast provides

Stable trajectory design, optimal mud-weight definition, maximum- and minimum-allowed equivalent circulating density (ECD) definition, "solid ground" for casing seat selection, swab and surge limit identification, drilling parameters optimization, preventative and remedial plan preparation.

A focus on shales

A combination of stress and pore pressure conditions around the well bore, related in part to inadequate drilling fluid salinity and type and improper mud weight, cause many costly time-dependent wellbore instability drilling events. This is particularly true while drilling through shale. Many operators and service providers treat shale-related wellbore instability as largely unavoidable. We address this issue by integrating studies of geomechanical wellbore instability with drilling fluid design.

Isotropic or anisotropic

Rocks are typically anisotropic (properties vary with direction) in their mechanical nature. However, it is common to model rock for wellbore stability studies as isotropic (properties do not vary with direction). This is partly for simplicity of modeling and partly because there are few or no measurements to back up an anisotropic approach.

Anisotropic behavior of rock, particularly in shales, can significantly change wellbore stability when drilling, making isotropic modeling misleading. Schlumberger provides a range of measurements based on wellbore acoustics and seismic, as well as laboratory measurements at TerraTek to assess the significance of anisotropic behavior and model the effects on stability.

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Webinar: Introduction to Seafloor Geohazards in Deep Water and Drilling Hazards

Introduction to Seafloor Geohazards in Deep Water and Drilling Hazards Associated with Exploration Around Salt
This webinar focuses on the important step of understanding the geologic origin of various hazards in deep water and around salt by reviewing the geologic origin, characteristics, and behaviors of deepwater hazards and challenges. Watch Webinar