The University of Southampton
University of Southampton Institutional Repository

Numerical modelling of wellbore behaviour in fractured rock masses

Numerical modelling of wellbore behaviour in fractured rock masses
Numerical modelling of wellbore behaviour in fractured rock masses
Wellbore instability problems have been encountered in many gas and oil fields. Fractures and a high differential stress (i.e., a large difference between the principal effective stresses in the horizontal plane) are considered to be major causes of wellbore instabilities, including hole enlargement and high volume caving. This paper describes the results of a series of numerical analyses carried out using UDEC (Universal Distinct Element Code) to obtain a better understanding of wellbore instability. The effects of two different fracture patterns (randomly polygonal fractures and aligned fracture sets) and three different far-field stress conditions have been investigated for various wellbore pressures, corresponding to different mud densities during drilling. It is known that the differential stress has an important influence on wellbore instability. A comparison of the numerical results with the analytical solution for homogeneous elastic behaviour has been carried out. The numerical analysis shows that the effect of a high differential stress is exacerbated by the presence of adversely connected fractures near the bore wall. The drilling mud density significantly affects the deformation of and the mud loss from a wellbore during drilling. It should be chosen carefully in the light of the fracture geometry and far-field stress.
wellbore, drilling, fractures, earth stress, hydraulic pressure
0920-4105
95-115
Zhang, Xing
e92abcc2-6163-40b0-9b53-0a61bdf864d7
Last, Nigel
2209f519-09c4-4b60-a94d-c752b3df01d0
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Harkness, Richard
383fea24-abe2-4faf-b252-734928768804
Zhang, Xing
e92abcc2-6163-40b0-9b53-0a61bdf864d7
Last, Nigel
2209f519-09c4-4b60-a94d-c752b3df01d0
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Harkness, Richard
383fea24-abe2-4faf-b252-734928768804

Zhang, Xing, Last, Nigel, Powrie, William and Harkness, Richard (1999) Numerical modelling of wellbore behaviour in fractured rock masses. Journal of Petroleum Science and Engineering, 23 (2), 95-115. (doi:10.1016/S0920-4105(99)00010-8).

Record type: Article

Abstract

Wellbore instability problems have been encountered in many gas and oil fields. Fractures and a high differential stress (i.e., a large difference between the principal effective stresses in the horizontal plane) are considered to be major causes of wellbore instabilities, including hole enlargement and high volume caving. This paper describes the results of a series of numerical analyses carried out using UDEC (Universal Distinct Element Code) to obtain a better understanding of wellbore instability. The effects of two different fracture patterns (randomly polygonal fractures and aligned fracture sets) and three different far-field stress conditions have been investigated for various wellbore pressures, corresponding to different mud densities during drilling. It is known that the differential stress has an important influence on wellbore instability. A comparison of the numerical results with the analytical solution for homogeneous elastic behaviour has been carried out. The numerical analysis shows that the effect of a high differential stress is exacerbated by the presence of adversely connected fractures near the bore wall. The drilling mud density significantly affects the deformation of and the mud loss from a wellbore during drilling. It should be chosen carefully in the light of the fracture geometry and far-field stress.

This record has no associated files available for download.

More information

Published date: August 1999
Keywords: wellbore, drilling, fractures, earth stress, hydraulic pressure

Identifiers

Local EPrints ID: 74683
URI: http://eprints.soton.ac.uk/id/eprint/74683
ISSN: 0920-4105
PURE UUID: a90d2e45-5ae7-4e35-928f-13efef7809c3
ORCID for William Powrie: ORCID iD orcid.org/0000-0002-2271-0826

Catalogue record

Date deposited: 11 Mar 2010
Last modified: 14 Mar 2024 02:37

Export record

Altmetrics

Contributors

Author: Xing Zhang
Author: Nigel Last
Author: William Powrie ORCID iD
Author: Richard Harkness

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×