Analysis of drilling-induced tensile fracture initiation in porous, permeable media considering fluid infiltration

Document Type

Conference Proceeding

Publication Date

1-1-2019

Abstract

Drilling-induced tensile fractures (DITFs) are located orthogonally from wellbore breakouts and are observed from image logs obtained during drilling operations. Fully analytical criteria for the orientation of DITFs initiating from vertical and horizontal wellbores in porous, permeable media are derived considering fluid infiltration using Biot’s theory of poroelasticity. This goes beyond previous studies that have used linearly-elastic media - the novelty of this work lies in considering fluid infiltration. Independent variables are discussed and expressions for the initiation pressures are presented for each well configuration. Dimensionless plots are used to indicate the region of the possible stress state at a given DITF orientation and the in-situ stress regime. Parameters that affect the size of this region and hence the magnitude range of components of the local stress tensor is discussed. Subsequently, the diagnostic power of DITFs is demonstrated under different scenarios, where the DITF orientation relative to the wellbore can be used to constrain the local in-situ stress tensor. For vertical and horizontal wells, the magnitude of SHmax can be constrained with closed-form analytical solutions for the corresponding upper and lower bounds of the SHmax magnitude. If the DITF initiation location is near the casing shoe, numerical modeling is necessary for determining the DITF orientation.

Publication Source (Journal or Book title)

53rd U.S. Rock Mechanics/Geomechanics Symposium

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