Large Scale Testing - Development of Advanced CFD Tools for the Enhanced Prediction of Explosion Pressure Development and Deflagration Risk on Drilling and Production Facilities

Abstract

GexCon, who has teamed with SRI, was awarded Subcontract 12121-6403-01 under the Research Partnership to Secure Energy for America (RPSEA), whereby the objective of this project is to improve inherently safer offshore facility designs. As the size of Ultra-Deepwater (UDW) facilities increases in the Gulf of Mexico (GOM), designs must consider the potential adverse effects associated with vapor cloud explosions in large congested areas and understand the potential for more devastating deflagration-to-detonation transitions (DDTs) on these facilities. Gas derived explosions can expand at over 6,000 feet per second, rendering escape to safety virtually impossible. Therefore, it is critical to understand how a facility's geometry or equipment layout can affect explosion consequences and assist in their mitigation and/or prevention. Only recently, post-Macondo, have platform operators placed more emphasis on major explosion barriers between the well head and the people running the very controls needed to control a blowout. Many of the existing drilling platforms have not considered predicting the effects of a small explosion escalating into a major event either in ship design or in prevention, such as what occurred on the Deepwater Horizon. All marine rigs have some fire control method(s), but few have evaluated escalating effects of explosions or DDTs. Designing topsides structures to withstand credible explosion events and to prevent the potential devastating phenomena of deflagration to detonation transitions (DDT) is an essential part of the route towards inherently safer designs for GOM drilling and production facilities. However, there is a lack of data at the large scale to validate the necessary design tools used to predict the risk of DDT. There are two main factors currently inhibiting inherently safer designs: A lack of detailed geometry information in the early design phase, which, when not integrated into facilities designs to identify congestion when performing explosion studies, result in severely underestimated design blast loads. A lack of adequate tools to predict the potential risks of DDT on these large deep water facilities, where the consequences of DDTs can be orders of magnitude larger than typical deflagrations.   One of the main goals of this project is to provide large-scale DDT explosion data and validate the tools necessary to predict vapor cloud explosions in early design phase. The work will also be used to develop guidance documents and recommended practices to facility owners and designers in order to minimize the consequence of explosion incidents. This paper will present the current updates for the large scale testing being conducted in a newly developed test rig of 1,500 m3 (52,000 ft3) gross volume. These tests will involve evaluation of deflagrations and DDTs involving stoichiometric, lean and rich mixtures ethylene, propane and methane. Further phases of the testing will also evaluate the effectiveness of other mitigation measures (e.g., water deluge, solid inhibitor) on the explosion consequences.