Using an Analytical Model to Predict Collapse Volume during Drilling: A Case Study from Southern Iraq


Zubair Formation is one of the richest petroleum systems in Southern Iraq. This formation is composed mainly of sandstones interbedded with shale sequences, with minor streaks of limestone and siltstone. Borehole collapse is one of the most critical challenges that continuously appear in drilling and production operations. Problems associated with borehole collapse, such as tight hole while tripping, stuck pipe and logging tools, hole enlargement, poor log quality, and poor primary cement jobs, are the cause of the majority of the nonproductive time (NPT) in the Zubair reservoir developments. Several studies released models predicting the onset of borehole collapse and the amount of enlargement of the wellbore cross-section. However, assumptions involved in these models have limited their applications to very specific scenarios. In this study, an analytical solution for determination of the volume of collapse during drilling is presented based on changes in the geometry of boreholes. The approach can be used in conjunction with different failure criteria to estimate the collapse onset in the presence of formation strengths and principal stresses. The study highlighted how the integration of information from different sources and disciplines were able to estimate the shear failure induced on the borehole wall during drilling.

Meeting Name

53rd U.S. Rock Mechanics/Geomechanics Symposium (2019: Jun. 23-26, Brooklyn, NY)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Boreholes; Infill drilling; Lime; Oil wells; Rock mechanics, Critical challenges; Failure criteria; Logging tools; Non-productive time; Petroleum systems; Principal stress; Production operations; Zubair formations, Well logging

Geographic Coverage


Document Type

Article - Conference proceedings

Document Version


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© 2019 American Rock Mechanics Association (ARMA), All rights reserved.

Publication Date

01 Jun 2019