Sensitivity analysis of viscous properties of salt rocks during oil well drilling

Resumo

This paper presents a sensitivity analysis of viscous properties of salt rocks during well drilling used to

explore and produce oil and gas. The definition of viscous properties of salt rocks is based on triaxial tests per-
formed on samples extracted in-situ. These properties can be difficult to characterize since demand obtaining core

samples and performing laboratory tests. In practical terms, the estimated properties of some pre-salt fields are
commonly extrapolated to others. However, this generalization can generate elevated errors in several cases. An
alternative is to use information about other oil wells already drilled in the same region with similar or equivalent

formations to predict anomalous behavior events. In this context, it is studied in this work the mechanical behav-
ior of oil wells drilled through salt rocks according to the variability of its constitutive parameters. The adopted

methodology includes: a) data collection on viscous properties of Brazilian salt rocks; b) simulations of oil wells

drilled on salt rocks varying the viscous properties of the surrounding formation; and c) calculation of the sensitiv-
ity of the variables related to well borehole radial displacement, aiming the better understanding of the relationship

between the constitutive properties of the salt rocks and the global mechanical behavior. This study can be used
as a startup reference for a retro-analysis to calibrate salt rock constitutive parameters from anomalous behavior
events in correlated oil wells. The main contribution of this work is associated to fitting a regression model to
events in correlated oil wells using a set of simulation results from the range of the constitutive parameters.