Provided are systems and methods for developing a hydrocarbon reservoir including determining properties of a well including a wellbore extending into a tested layer of a multi-layer hydrocarbon reservoir including a barrier located between the tested layer and an adjacent layer of the multi-layer hydrocarbon reservoir, determining a point in time at which a value of a rate of influx of production fluid across the barrier from the adjacent layer and into the tested layer corresponds to a production contribution tolerance value for the well, determining a derivative of a profile of pressure in the targeted layer as a function of radial distance from the wellbore of the well at the point in time, and determining a drainage radius for the well corresponding to the derivative of the profile of pressure in the targeted layer and a pressure derivative tolerance value.