The Centre of Petroleum Studies at Imperial College London has been involved in research in well test analysis since 1997, sponsored mainly by consortia of oil companies. The work has already resulted in significantly improved understanding of complex well test behaviours, particularly in gas condensate and volatile oil reservoirs; in reservoirs with complex geological features; and in multilateral wells. The ability to interpret well tests has also been greatly enhanced by the development of a stable deconvolution algorithm which has now been implemented in all dominant well test analysis softwares. The aim of this proposal is to expand the work performed to-date in three main areas: (1) deconvolution of pressure and data from interfering wells in developed reservoirs (multiwell deconvolution) (2) analysis of shale oil and gas well production data (from nano-scale to Darcy-scale) (3) well test analysis in complex systems The objective is to develop new, practical analysis methods for calculating well and reservoir parameters, for estimating reserves, and for predicting and improving well productivity in complex reservoir-fluid-well systems. Limitations and uncertainties in the analyses as a function of the data available will also be a focus of the research.