A computer implemented method of forming a two-dimensional pressure map with a data processing system of reservoir pressures in a region of interest in a subsurface hydrocarbon producing reservoir partitioned for modeling purposes into a reservoir model partitioned as an array of a grid of cells extending over the three dimensions of the reservoir, the reservoir having a plurality of wells with perforations for fluid passage from the reservoir into the wells, with selected ones of the wells having downhole pressure measurement systems installed therein, the array of a grid of cells of the reservoir model comprising well cells at the locations of the wells and reservoir cells at the remaining cells of the grid, the method comprising the computer processing steps of: (a) obtaining, by way of a downhole pressure measurement system , pressure data for the wells, the downhole pressure measurement system comprising downhole sensors installed in a subset of the wells (G), the pressure data for the wells comprising pressure measurements collected from downhole sensors installed in the subset of the wells; (b) performing simulated pressure calculations on a reservoir simulator in the data processing system for the cells in an array of well cells for an area of interest of the reservoir ; (c) populating well cells at an uppermost perforation of each of the wells with assigned pressure values from the received pressure data ; (d) propagating pressure values for the well cells of the wells below the uppermost perforations and to the reservoir cells of the area of interest to form a three-dimensional grid pressure array for the area of interest ; (e) reducing the three-dimensional grid pressure array to a two-dimensional layer of pressure values for the region of interest ; (f) assembling in memory of the data processing system the two-dimensional layer of pressure values for the region of interest ; and (g) forming an output image map of the two-dimensional layer of pressure values for the region of interest for use in management of the reservoir. (a) obtaining, by way of a downhole pressure measurement system , pressure data for the wells, the downhole pressure measurement system comprising downhole sensors installed in a subset of the wells (G), the pressure data for the wells comprising pressure measurements collected from downhole sensors installed in the subset of the wells; (b) performing simulated pressure calculations on a reservoir simulator in the data processing system for the cells in an array of well cells for an area of interest of the reservoir ; (c) populating well cells at an uppermost perforation of each of the wells with assigned pressure values from the received pressure data ; (d) propagating pressure values for the well cells of the wells below the uppermost perforations and to the reservoir cells of the area of interest to form a three-dimensional grid pressure array for the area of interest ; (e) reducing the three-dimensional grid pressure array to a two-dimensional layer of pressure values for the region of interest ; (f) assembling in memory of the data processing system the two-dimensional layer of pressure values for the region of interest ; and (g) forming an output image map of the two-dimensional layer of pressure values for the region of interest for use in management of the reservoir. <EOS>