Reservoir boundary information is gleaned from a steadyflowrate-drawdown test and/or a subsequent buildup following the steady flow period. Singularities are observed to be present in virtually all transient pressure data that can provide direct information about the limits around a well. Multiple limits can be detected discretely and described by distance from the well and angular shape at the point of contact. The input information required is pressure data acquired while flowing on a fixed choke, petrophysical properties from cores and electric logs, and fluid production rates and compositions during the flow period.