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Reveal the Cause of Downhole Restrictions by Means of Knowledge Engineering
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Petroleum Engineering and Applied Geophysics.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

Stuck pipe is an example of an unwanted problem that causes high NPT and seems to occur again and again. As 50 % of all stuck pipe incidents occur during tripping, increased knowledge about how to recognize progressing downhole problems are needed. Early warnings of stuck pipe are HKL restrictions, and early warnings of HKL restrictions are symptoms. If the symptoms seen at surface can be related to a HKL restriction type, preventing actions can be initiated at an early stage, and stuck pipe can be avoided. Four main causes of HKL restrictions have been analysed and related to symptoms that can be recognized at the surface. The main causes are accumulating cuttings, mechanically unstable wellbore, chemically unstable wellbore and local dogleg. By means of the Knowledge Model, relationships between the symptoms and the main causes were determined. The strength of the relation between each symptom and the restriction cause was found and proved diversity among the main symptoms of each restriction cause. 21 cases of HKL restrictions were found from drilling reports and RTDD obtained from Statoil. Symptoms interpreted from the drilling reports were used as input for the Knowledge Model which revealed the main cause of the restriction. The model proved that 14 of the 21 restriction cases were caused by the error Reactive Formation. The HKL signature of the 21 cases was interpreted and related to the restriction causes. The interpretation showed that the signature of cuttings accumulating can be separated from the signatures of mechanically instability. Five restriction events were analysed using the Knowledge Model. The main cause of the restriction events were found proving the Knowledge Models ability to de- termine the restriction cause of downhole problems. The analysis proved that Reactive Formation was the most frequent error to cause HKL restrictions, with explanatory strength of 48 % as the highest in average.

Place, publisher, year, edition, pages
Institutt for petroleumsteknologi og anvendt geofysikk , 2013. , 126 p.
URN: urn:nbn:no:ntnu:diva-22907Local ID: ntnudaim:9082OAI: diva2:655057
Available from: 2013-10-09 Created: 2013-10-09 Last updated: 2013-10-09Bibliographically approved

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