The concept of stimulated reservoir volume (SRV) provides a link between well productivity, the observed distribution of microseismic events and fracture networks that are created or enhanced during well completion. The SRV dimensions are affected by both reservoir geomechanical properties and hydraulic fracturing parameters. This research focuses on the determination of anisotropic permeability and the estimation of the SRV dimensions by refining the existing 3D linear diffusivity partial differential equation (PDE). The anisotropic permeability and the SRV are both calibrated using the analytical solution, based on determination of microseismic events that are inferred to be connected back to the horizontal wellbore. An improved analytical 3D linear diffusivity PDE model is proposed to simulate the anisotropic permeability and the SRV dimension with higher percentage of microseismic events. In a case study from western Canada, the proposed approach yields improved the prediction of the SRV dimension that consists 90 of microseismic events within the SRV, compared to the existing analytical solution predicts the SRV dimension that consists 70 of microseismic events within the SRV. The SRV anisotropic permeability is also estimated using the proposed model with the average values of 0.1897 mD (SRV length direction), 0.1112 mD (SRV width direction), and 0.0138 mD (SRV height direction) from 12 stages hydraulic fracturing. The simplicity of the proposed model allows the SRV dimensions estimation before hydraulic fracturing operations. © 2018 Elsevier B.V.