1. A method of performing a numerical model study to accurately forecast a production of a well in a reservoir, comprising: determining, a property distribution of the reservoir using a digital 3D structure and property model for providing an estimate of a 3D structure, wherein the estimate of the 3D structure includes the property distribution; determining a grid system, including a grid and layering mechanism that is superimposed on said 3D structure and said property distribution associated with the digital 3D structure and property model, using a 3D simulator grid system; and determining a rock model using an initial 3D reservoir simulator in response to the estimate of the property distribution associated with the digital 3D structure and property model and the grid system associated with the 3D simulator grid system, wherein the rock model is used to accurately forecast the production of the well in the reservoir.