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Borehole Acoustics Characterization in Deepwater
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Petroleum Geoscience Conference & Exhibition 2013, Mar 2013, cp-340-00088
Abstract
The subsurface stress state in deepwater wells is critical for drilling and completion operations due to the reduced litho-static column in the overburden. The vertical stress in this case may not be the major principal stress as would be conventionally assumed in shallow water environment due to a difference in the weight of the overburden. As a result, mud weight windows are narrower and production induced stress changes are more substantial, requiring better predictability of the initial stress state. New techniques have been developed to estimate the maximum and minimum horizontal stress magnitudes using a combination of pore pressure, overburden stress and advanced full-waveform sonic data derived from the shear radial profiles and 3 shear moduli. Knowledge of the wellbore stress state (axial, radial and tangential stresses) along with a non-linear elastic model is used to estimate the principle stress magnitudes. Since deepwater sediments are extremely sensitive for acoustics methods to detect changes in stress, this method is suited to model this lithology. A case study will be presented from a deepwater well in Malaysia where all three principal stresses are determined through evaluation of advanced 3D acoustic characterization of the wellbore.