Shale Instability of Deviated Wellbores in Southern Iraqi Fields


Wellbore instability problems are the cause for the majority of nonproductive time in the southern Iraqi field developments. These drilling difficulties pose potential problems such as mud losses in weak or vugular formations, stuck pipe in shales or unconsolidated formations. This paper focuses on the most severe problem in terms of effort and disbursement which is referred to pipe sticking in Tanuma shale formation. Examining the drilling data revealed that this phenomenon was mostly related to shear failure of the wellbore, which caused an immediate increase in the stand pipe pressure with no drilling fluid returns when circulating. In this regard, a geomechanical analysis for southern Iraqi field was performed on field data from 45 deviated. The analysis identified the following areas of improvement. First, the mud weight being used was not changed properly with respect to variation in wells azimuth and inclination. Secondly, anisotropic effects of this shale formation caused by the bedding planes should be considered in wells trajectory design. Due to the lack of published studies regarding wellbore problems in southern Iraqi fields, this paper could serve as case history for similar fields in that region.

Meeting Name

50th US Rock Mechanics / Geomechanics Symposium (2016: Jun. 26-29, Houston, TX)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Deflected Boreholes; Drilling Fluids; Oil Field Equipment; Rock Mechanics; Shale; Well Drilling; Anisotropic Effects; Field Development; Non-Productive Time; Potential Problems; Shale Instability; Trajectory Designs; Unconsolidated Formations; Wellbore Instability; Boreholes

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2016 American Rock Mechanics Association (ARMA), All rights reserved.

Publication Date

01 Jun 2016