This report describes the results of simulation study performed on a single five spot pattern of water injection. The study is intended to analyse the reservoir performance under various injection pattern alternatives that can be considered by infill drilling, i.e. five spot, nine spot (normal and inverted) and line drive pattern, and also to investigate the effect on the areal sweep efficiency when the timing of infill drilling is delayed. The main results are: -Under the five spot pattern case, both production capacity and recovery efficiency at water breakthrough are the highest. The delay of the infill drilling distorts the areal symmetry of the initial flood pattern and thus, cause less recovery efficiency at water breakthrough. Although the above results are to some extent, inferable by an analytical method, reservoir performance under each case have been more quantitatively analysed by a simulation approach in this study, and also a three dimensional description has been utilized to aid in the quick understanding of the behaviour of water front advance under the different injection patterns.