Horizontal stress contrast in the shallow marine sediments of the Gulf of Mexico sites Walker Ridge 313 and Atwater Valley 13 and 14 – Geological observations, effects on wellbore stability, and implications for drilling

Subsurface gas hydrates in the northern Gulf of Mexico

“…To provide the highest quality data, the JIP had planned to eliminate the use of shallow casing strings and heavy drilling fluids and operate in a full open hole using sea-water with gel sweeps as needed. However, borehole wall collapse and inefficient cuttings removal during the drilling of the initial well (WR313-G) necessitated periodic backreaming and other drilling measures that degraded the LWD data Birchwood and Noeth, 2012;Cook et al, 2012). As a result, standard drilling plans were modified to include the introduction of heavy drill fluids at roughly 450 m (1500 ft) drilling depth.…”

Gulf of Mexico Gas Hydrate Joint Industry Project Leg II logging-while-drilling data acquisition and analysis

“…Pre-drilling borehole stability modeling by Schlumberger Geomechanics and drilling experience from GOM JIP Leg I (Birchwood et al, 2007;Birchwood and Noeth, 2012) had shown that the thermal and mechanical disturbance of highly concentrated gas hydrate occurrences could adversely affect borehole stability conditions leading to severe washouts and borehole cavings if drilling protocols and fluid temperatures are not properly managed. But upon the completion of the GOM JIP Leg II drilling and the examination of the LWD tool measured downhole drilling fluid temperatures, it was determined that drilling fluid temperatures in all seven wells drilled during Leg II were never great enough to cross the gas hydrate stability phase boundary.…”

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

“…In this case, the stress field close to the borehole can be calculated from the stress concentration around a hole in an infinite, linear elastic, and isotropic plate (e.g., Zoback 2010). However, neglecting the anisotropy for any other orientation, as commonly done in drilling applications (Gaede et al 2012;Khan et al 2011;Birchwood and Noeth 2012), may result in significant errors of stress estimates (Blümling 1986).…”