The Oil & Gas industry continues to explore and develop ever more challenging and difficult hydrocarbon prospects. Also Asia is experiencing a push into deeper water, exploring reservoirs with higher pressure and more difficult and complicated formations, i.e. fractured carbonates. These operating conditions results in an increased interest for more novel drilling systems, i.e. offshore managed pressure drilling. But how safe and reliable are these new systems?

A general perception is that new technology introduces more risks, and there are a number of examples of new technology not meeting expectations with respect to reliability and performance. What would be the consequence of a failure in these new drilling systems? To further complicate the situation, the recent Macondo and Montara blowout has put a increased pressure on the drilling industry to demonstrate safe and reliable drilling operations; there is no tolerance for failure.

One of the challenges with this risk adverse perception on new technology is that conventional systems are typically only evaluated on the basis of their past track record, with little or no considerations to the more complicated and challenging operating environments. Consequently, the drilling contractors experience more drilling problems when operating in these new environments, i.e. stuck pipe and lost circulation. These issues result in high operating costs due to loss of drilling mud and non-productive time (NPT), but they also represent a potential safety risk as these drilling events may trigger a well control incidents.

To provide a more realistic risk picture and have a better basis to compare alternative drilling systems, DNV has together with the industry developed a methodology to assess and quantify the risk of blowouts related to a specific well operation. This risk based assessment is based on a systematic assessment of the drilling rig, drilling equipment, operating conditions, sub-surface conditions and drilling and casing program. In this paper the methodology is outlined, and a case example related to a specific drilling operation in a fractured carbonate reservoir of the Eastern coast of Sulawesi, Indonesia, is used to demonstrate the methodology.

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