‘Open Forum - Question and Answers’ session at the end of the presentation by David Kaye of BP Exploration Operating Company Ltd
Mark Richardson – Apache. The riser that you recovered, have you done destructive testing and assessment on it, having removed it?
David Kaye – BP (Presenter). That particular riser the answer is not yet but we will do. We did recover another riser which I didn’t include in this presentation a couple of years ago. In fact it was the riser that I mentioned when we took out, replaced six bent stiffeners and there was one riser that we completely replaced and that one has been subject to great detailed dissection work in Letrave by Technip and we intend to do something similar for that RH riser that we took out.
Mark Richardson – Apache. Have you any assessment of how close it is to your modelling?
David Kaye – BP (Presenter). Yeah yeah I thought that question would come and I tried not to answer it! (laughter). Its very difficult because obviously when we do fatigue assessments, what the calculation actually says is that the probability of a fatigue failure is above the level that the industry perceives to be acceptable. So in other words it doesn’t actually mean we’ll see anything unfortunately. So therefore when you do the dissection - we did see some things which were interesting but we didn’t see any cracks which would indicate that we could validate the fatigue calculation.
Phil Duncan - Ionic Consulting. Did you look at the effect of corrosion inhibitor in the annulus on the corrosion fatigue life?
David Kaye – BP (Presenter). Yeah yeah. I’d skip through that little bit quickly during the presentation. When we did the actual testing we did the testing for specific conditions for that riser so in other words it was with the appropriate sour environment. It was with the inhibitor in place and it was for the relevant wires taken from representatives of stock for that structure. We also did some tests and had some previous data in non-sour conditions but with the same inhibitor and we do have some data for in-air conditions if you like with no inhibitor and no sour conditions as well. In terms of your question, between air and inhibited conditions I actually couldn’t tell you off the top of my head what the difference is. There is some difference. It’s not huge. At the time we were actually more concerned in terms of the difference between flushed sweet and flushed sour so you would need to look at the H2S effect.
Charlie Smith – Shell. Yeah it’s a bit of a follow up to the last question there when you did the sour service testing based on the conditions you expected in the annulus. Was that the calculated annulus conditions or were they actual measured because some of the earlier presentations maybe cast a bit of doubt on the accuracy of some of the calculations?
David Kaye – BP (Presenter). Yeah it was based on calculated - using obviously measured bore conditions and then calculated annulus conditions using the technique moulding model in order to make the, if you like the transition in terms of the annulus condition. We didn’t measure actual annulus conditions. It would have been interesting to have been able to do that check in order to verify what the model was predicting to be honest.