Salt Creep

Forecast salt creep to avoid stuck pipe and other hazards

In the geological time frame salt, owing to its plastic nature, can move extensively within the subsurface creating diapirs and walls. While these structures generate significant traps for hydrocarbons they also present a number of drilling problems. A salt intrusion locally distorts the stress field making wellbore stability impossible to predict using conventional geomechanical models.

Not all salts behave in the same way. Simple salts, such as halite, remain relatively stable during drilling. Complex salts, particularly tachyhydrite, can creep and close around a drillstring very rapidly. Schlumberger has many years of experience in identifying these complex salt types, modeling the complex formation stresses that some salts create and predicting wellbore stability.

Salt modifies the surrounding formation behavior

The disruption to the formations adjacent to salt diapirs gives rise to a number of other stability problems including rubble and fractured zones, reduced fracture gradients, and faulting. Schlumberger experts have extensive operational knowledge of integrating geomechanics into drilling plans to drill through and around salt, avoiding wellbore instability. It is essential to have a contingency plan in case a problem arises with the original well plan when drilling in and around salt.

Data from logging-while-drilling tools (LWD) are used to help identify hazards in the salt section. Important measurements include EcoScope spectroscopy to determine salt composition and seismic-while-drilling measurements that can be used to correlate with existing seismic data to help update geomechanics models and plan salt exit. In addition, resistivity, and sonic-while-drilling for pore pressure modeling, together with formation-pressure-while-drilling provide a measurement of pore pressure immediately above the salt body.

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Potential Drilling Hazards In and Around Salt

Salt Creep
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