Production well optimization and modeling is very important in the efficient management of oil and gas production from a well. A major factor contributing to this process is the accurate estimations of the flowing bottom-hole pressure at the formation as it helps in various petroleum production engineering analysis. Some of these analysis include studies on Vertical Lift Performance (VLP) and Inflow Performance. The effective determination of bottom-hole pressure has been a major concern in the industry due to several reasons as it can either be measured or estimated. In the case of measurement, a pressure gauge is needed down-hole, this is very accurate but expensive and time consuming. For this reason, this project will focus on flowing bottom-hole pressure estimation from wellhead pressure and data as it is generally cost effective and it can be easily determined within a short period of time. This will be achieved through the modification of Guo’s (2001) method of simultaneous flow of gas, oil, water and sand particles (4-phase flow) in borehole tubing. Guo’s model will be modified and will only consider the frictional pressure gradient term in the general energy equation and account for only vertical multiphase flow. The result of this work obtained with the use of mat lab when applied to simulation of two phase flow in vertical oil wells and high Gas-Oil ratio wells are relatively accurate. However, low Gas-Oil ratio wells fall short of the model estimation of pressure.