Embedding Automatic Risk-Level Estimation and Performance Analysis in Drilling Plans

Fig. 1—Three-dimensional representation of the admissible drilling-parameter set. For a given drill depth and confidence parameter, the safe combinations of flowrate, drillstring rotational speed, and WOB are represented by the red volume. Although quantified information is difficult to obtain from such a representation, it is clear from the comparison of the two volumes that the configuration on the left provides more safety with respect to the analyzed risks than the one on the right.

It is not unusual that the difficulties encountered during a drilling operation can be tracked to choices made during planning. However, generating a robust drilling-operation plan is not easy because substantial uncertainties are often associated with the actual geological context. To address this problem, this paper presents a method that quantitatively evaluates the risk levels of a drilling-operation plan as a function of the underlying uncertainty associated with its description.


A drilling operation is always subject to operational risks (e.g., formation-fluid influx, lost circulation, borehole instability, packoff, stuck pipe, or drillstring failure). The chance of occurrence of some of those threats may be small in a particular well design. But, in other configurations, it may be known already at the planning stage that potential drilling problems are likely, because of tight operational margins for instance. The drilling challenges also may be aggravated by uncertainties in the geological context.

Making a robust drilling-operation plan is a challenge, and there are many reasons for this. One of them is connected to the difficulty in evaluating quantitatively, at the planning stage, the effect of uncertain information on the effective risk levels that may prevail during well construction. Quantitative risk assessment with management of uncertainty has been described for specific tasks, such as choosing a mud weight as a function of an uncertain geopressure window. The more risks that are simultaneously evaluated within the expected uncertainty of the coming operation, the greater the chances are that the proposed drilling-operation plan will be robust.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181018, “Automatic Performance Analysis and Estimation of Risk Level Embedded in Drilling-Operation Plans,” by Eric Cayeux, SPE, and Benoît Daireaux, SPE, IRIS; Mohsen Karimi Balov, Statoil; Stein Haavardstein, ConocoPhillips; Leif Magne Stokland, Wintershall; and Arild Saasen, SPE, Det Norske, prepared for the 2016 SPE Intelligent Energy International Conference and Exhibition, Aberdeen, 6–8 September. The paper has not been peer reviewed.
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Embedding Automatic Risk-Level Estimation and Performance Analysis in Drilling Plans

01 September 2017

Volume: 69 | Issue: 9


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