# Dynamic Response of Drill Floor Considering Propagation of Blast Pressure Subsequent to Blowout
## 1 Introduction  
Research studies have been carried out on fires and explosions caused by oil and gas leakage in Floating Production Storage Offloading (FPSO) as an offshore facility [1; 2; 3; 4; 5]. The drilling operation is essential for oil and gas production, and there are risks from accidental blowout as well as from induced fire and explosion. The key function of a drill floor is to hold the drilling equipment and to support derrick and drilling operating loads. However, only a few studies on explosions and fire related to drilling have been reported [6], and no observations of the structural response of the drilling unit have been made when experiencing an explosion. This is the reason why this study focuses on the drill floor. This study contributes to the investigation of the structure response of the drill floor of a drilling unit and suggests a new approach for blast pressure application based on the observation of blast pressure propagation. The drill pipe is connected to the drill hole in a seabed from the top drive on a drill floor, and the oil and gas mixture can be blown out in the case of failure in the Blowout Preventer (BOP) system during drilling operation. Leakage of oil and gas mixture is expected in the connections over and under the drill floor; therefore, structural integrity of the drill floor is critical for the entire facility when it experiences an accident. Quantitative risk analysis of oil and gas drilling has been introduced based on Risk Influence Factors (RIFs) and Human and Organizational Factors (HOFs) for the Deepwater Horizon blowupt case [7]. Several safety barrier models were illustrated to mitigateand control the blowout accident, and event tree analysis was used to analyze the possible consequence chains [8]. The blast wave propagation of an explosive detonation can cause disastrous damage on various structures, and the computed results were found to be in agreement with the theoretical and experimental data [9]. Simplified blast pressure estimation is not sufficient to describe the explosion and blast wave propagation in complex facilities. The use of Computational Fluid Dynamics (CFD) for blast wave predictions present a more precise estimation of the energy and resulting pressure of the blast wave, and provides the ability to evaluate non-symmetrical effects caused by realistic geometries, gas cloud variations, and ignition locations; however, the main challenge in applying CFD is that these models require more information about the actual facility, including geometry details and process information [10]. This study fully reflects the geometry and process information of a typical drilling facility. A combined blast pressure approach was presented for a case in which the design blast pressure was specified for engineering purposes using Flame Acceleration Simulator (FLACS) software. This showed that the global blast pressure could result in an overly conservative design, if the maximum explosion loads on each item are summed simultaneously [11]. This approach is quite practical to use in the design and engineering of each component of oil and gas facilities, such as the structure, piping, and electricals; however, this approach considers that blast pressure effects on all facilities at the same time regardless of the distance from each facilities to a location of the ignition. The relationships between blast pressure and impulse of FPSO topside blast walls has been developed and a practical procedure for nonlinear structural response analysis of FPSO topside blast wall under explosion loads was introduced. One was computed using time-domain nonlinear finite element analysis, while the other was performed using a single degree of the freedom method based on resistance function. Direct application of blast pressure from CFD analysis through a consequence exceedance curve has been introduced [12; 13].