A method for optimal well design, the method comprising: providing a computational model of a well , the computational model comprising a section of wellbore , surrounding formation , and a well completion arrangement positioned between the wellbore and surrounding formation , the well completion arrangement defining fluid paths between the surrounding formation and the wellbore , wherein the fluid paths provide an effective inflow area from the surrounding formation to the wellbore ; and then a. calculating fluid production from the surrounding formation , through the well completion arrangement , to the wellbore ; and b. varying the effective inflow area of the well completion arrangement ; and repeating steps a. and b. so as to determine a profile of well performance for that computational model of the well based on a range of effective inflow areas of the well completion arrangement , and determining an optimal well design having a particular effective inflow area based on the determined profile; and wherein the computational model comprises a plurality of well completion arrangements , axially aligned and connected lengthwise; the plurality of well completion arrangements comprising at least a first well completion arrangement having a first effective inflow area and a second well completion arrangement having a second effective inflow area, the second effective inflow area being different from the first effective inflow area; and the effective inflow area of each well completion arrangement is individually varied in order to determine the optimal well design. providing a computational model of a well , the computational model comprising a section of wellbore , surrounding formation , and a well completion arrangement positioned between the wellbore and surrounding formation , the well completion arrangement defining fluid paths between the surrounding formation and the wellbore , wherein the fluid paths provide an effective inflow area from the surrounding formation to the wellbore ; and then a. calculating fluid production from the surrounding formation , through the well completion arrangement , to the wellbore ; and b. varying the effective inflow area of the well completion arrangement ; and a. calculating fluid production from the surrounding formation , through the well completion arrangement , to the wellbore ; and b. varying the effective inflow area of the well completion arrangement ; and repeating steps a. and b. so as to determine a profile of well performance for that computational model of the well based on a range of effective inflow areas of the well completion arrangement , and determining an optimal well design having a particular effective inflow area based on the determined profile; and wherein the computational model comprises a plurality of well completion arrangements , axially aligned and connected lengthwise; the plurality of well completion arrangements comprising at least a first well completion arrangement having a first effective inflow area and a second well completion arrangement having a second effective inflow area, the second effective inflow area being different from the first effective inflow area; and the effective inflow area of each well completion arrangement is individually varied in order to determine the optimal well design. <EOS>