A matrix-calculation-based algorithm for numerical change propagation analysis

Engineering changes (ECs) are raised throughout the lifecycle of engineering products. A single change to one component produces knock-on effects on others necessitating additional changes. This change propagation significantly affects the development time and cost and determines the product's success. Predicting and managing such ECs is, thus, essential to companies. Some prediction tools model change propagation by algorithms, whereof a subgroup is numerical. Current numerical change propagation algorithms either do not account for the exclusion of cyclic propagation paths or are based on exhaustive searching methods. This paper presents a new matrix-calculation-based algorithm which can be applied directly to a numerical product model to analyze change propagation and support change prediction. The algorithm applies matrix multiplications on mutations of a given design structure matrix accounting for the exclusion of self-dependences and cyclic propagation paths and delivers the same results as the exhaustive search-based Trail Counting algorithm. Despite its factorial time complexity, the algorithm proves advantageous because of its straightforward matrix-based calculations which avoid exhaustive searching. Thereby, the algorithm can be implemented in established numerical programs such as Microsoft Excel which promise a wider application of the tools within and across companies along with better familiarity, usability, practicality, security, and robustness. © 1988-2012 IEEE.

Numerical study on hydrate bearing sediments during gas production

The fully coupled methane hydrate model developed in Cambridge was adopted in this numerical study on gas production trial at the Eastern Nankai Trough, Japan 2013. Based on the latest experimental data of hydrate soil core samples, the clay parameters at Eastern Nankai site were successfully calibrated. With updated clay parameters and site geometry, a 50 days gas production trail was numerically simulated in FLAC2D. The geomechanical behaviour of hydrate bearing sediments under 3 different depressurization strategies were explored and discussed. The results from both axisymmetrical and plane-strain models suggest, the slope of the seabed only affects mechanical properties while no significant impact on the dissociation, temperature and pore pressure. For mechanical deformation after PT recovery, there are large settlements above the perforation zone and small uplift underneath the production zone. To validate the fully coupled model, numerical simulation with finer mesh in the hydrate production zone was carried out. The simulation results suggest good agreement between our model and JOE's results on history matching of gas and water production during trial. Parameter sensitivity of gas production is also investigated and concluded the sea water salinity is a dominant factor for gas production.