Geomechanical Modeling of In-Situ Stresses Around a Borehole
In this paper, we present a modelling of the in-situ stress state associated with the severe hole enlargement of a wellbore. Geomechanical information is relevant to assure wellbore stability, i.e., to prevent damages in the formation and later on, the casing. Many of the drilling parameters, as...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Technical Report |
| Published: |
Massachusetts Institute of Technology. Earth Resources Laboratory
2011
|
| Online Access: | http://hdl.handle.net/1721.1/67848 |
| _version_ | 1811083315348766720 |
|---|---|
| author | Grandi, Samantha Rao, Rama V. N. Toksoz, M. Nafi |
| author2 | Massachusetts Institute of Technology. Earth Resources Laboratory |
| author_facet | Massachusetts Institute of Technology. Earth Resources Laboratory Grandi, Samantha Rao, Rama V. N. Toksoz, M. Nafi |
| author_sort | Grandi, Samantha |
| collection | MIT |
| description | In this paper, we present a modelling of the in-situ stress state associated with the severe hole
enlargement of a wellbore.
Geomechanical information is relevant to assure wellbore stability, i.e., to prevent damages in the
formation and later on, the casing. Many of the drilling parameters, as mud weight or the optimal
orientation of the borehole, require some knowledge of the mechanical behaviour of the rock. The lack of
these kind of data in exploratory areas, where there are usually insufficient constraints for the geological
model, increases even more the risk, hence the costs.
The present model uses the concepts of poroelasticity theory to compute the stationary 2D, brittle
response of the formation around a borehole that is submitted to effective compressive horizontal stresses.
The numerical solution is obtained using a finite element approximation.
The initial stress state at the far field was estimated combining a frictional-failure theory with the
observations of dipmeter caliper in a particular borehole that presents elongations in a preferential direction.
The direction and relative extension of the observed breakouts at a particular depth are modelled
successfully using formation realistic parameters and dimensions, although the exact shape of the borehole
(at all angles) was unknown. For the particular case study, the orientation of the breakout is NE-SW, at
about 82 degrees azimuth. Therefore, the maximum horizontal stress lies at approximately 350 degrees
azimuth. The ratios of horizontal principal stresses to vertical stress that best honor the observations
are SHmax = 2.3Sv and Shmin = 1.7Sv. The compressive strength necessary for the rock to fail, as
indicated by the caliper data under this stress field, is about 140 MPa. |
| first_indexed | 2024-09-23T12:31:06Z |
| format | Technical Report |
| id | mit-1721.1/67848 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T12:31:06Z |
| publishDate | 2011 |
| publisher | Massachusetts Institute of Technology. Earth Resources Laboratory |
| record_format | dspace |
| spelling | mit-1721.1/678482019-04-11T09:00:59Z Geomechanical Modeling of In-Situ Stresses Around a Borehole Grandi, Samantha Rao, Rama V. N. Toksoz, M. Nafi Massachusetts Institute of Technology. Earth Resources Laboratory Grandi, Samantha Rao, Rama V. N. Toksoz, M. Nafi In this paper, we present a modelling of the in-situ stress state associated with the severe hole enlargement of a wellbore. Geomechanical information is relevant to assure wellbore stability, i.e., to prevent damages in the formation and later on, the casing. Many of the drilling parameters, as mud weight or the optimal orientation of the borehole, require some knowledge of the mechanical behaviour of the rock. The lack of these kind of data in exploratory areas, where there are usually insufficient constraints for the geological model, increases even more the risk, hence the costs. The present model uses the concepts of poroelasticity theory to compute the stationary 2D, brittle response of the formation around a borehole that is submitted to effective compressive horizontal stresses. The numerical solution is obtained using a finite element approximation. The initial stress state at the far field was estimated combining a frictional-failure theory with the observations of dipmeter caliper in a particular borehole that presents elongations in a preferential direction. The direction and relative extension of the observed breakouts at a particular depth are modelled successfully using formation realistic parameters and dimensions, although the exact shape of the borehole (at all angles) was unknown. For the particular case study, the orientation of the breakout is NE-SW, at about 82 degrees azimuth. Therefore, the maximum horizontal stress lies at approximately 350 degrees azimuth. The ratios of horizontal principal stresses to vertical stress that best honor the observations are SHmax = 2.3Sv and Shmin = 1.7Sv. The compressive strength necessary for the rock to fail, as indicated by the caliper data under this stress field, is about 140 MPa. Massachusetts Institute of Technology. Borehole Acoustics and Logging Consortium Massachusetts Institute of Technology. Earth Resources Laboratory 2011-12-21T19:03:09Z 2011-12-21T19:03:09Z 2002 Technical Report http://hdl.handle.net/1721.1/67848 Earth Resources Laboratory Industry Consortia Annual Report;2002-06 application/pdf Massachusetts Institute of Technology. Earth Resources Laboratory |
| spellingShingle | Grandi, Samantha Rao, Rama V. N. Toksoz, M. Nafi Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title | Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title_full | Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title_fullStr | Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title_full_unstemmed | Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title_short | Geomechanical Modeling of In-Situ Stresses Around a Borehole |
| title_sort | geomechanical modeling of in situ stresses around a borehole |
| url | http://hdl.handle.net/1721.1/67848 |
| work_keys_str_mv | AT grandisamantha geomechanicalmodelingofinsitustressesaroundaborehole AT raoramavn geomechanicalmodelingofinsitustressesaroundaborehole AT toksozmnafi geomechanicalmodelingofinsitustressesaroundaborehole |