Borehole stability on Yme

Abstract

The main object of this thesis it to perform an in-situ stress and borehole stability evaluation of the wells in the Yme field. The Inversion technique was used find the maximum and minimum horizontal stresses. The stresses were found for the whole well and for the location around each casing shoe. The field was found to be anisotropic. The outcome of the analysis was used together with data form each well to calculate fracture and collapse gradients for the wells. The fracturing gradient became unrealistic large for several of the wells, and too low for well 9/2 A-8. The cause for this may be data inconsistency from collection of the data from many different sources. Also a geological uncertainty related to the faults and tectonic forces present represents a factor. The effect of azimuth and inclination on the stability is commented by comparing the fracture and collapse gradients for the different wells. Azimuth is observed to have a large effect on the fracturing gradient and a smaller effect on the collapse gradient.