PTA is a Reservoir Engineering tool when we differentiate dual porosity or, more particularly, natural fracture vs. matrix deliverability. Natural fractures derive from tectonic events: folding and faulting. Permeability in natural fractures is orders-of-magnitude higher than in porous rock matrix. Transient deliverability from natural fractures is thus much higher than steady-state deliverability from the rock matrix. Conversely, volumetric reserves are low in the fractures, high in the matrix, so fractures deplete, leaving the matrix for long term economics. Over-sizing facilities based on high discovery flow rates from fractures can lead to liquidity issues, as BP unfortunately discovered in the BC Sekunka/Bullmoose field, before they sold out and left Canada. Flow regime identification is critical to forecasts in naturally fractured zones, be very wary until the matrix reveals itself. Key to welltesting is drawdown, because a fairly large pressure differential, between fracture and matrix, is required for the matrix to flow.