High water production is one of the biggest production problems causing early abandonment of many oil wells. Excessive water production either coning from the bottom of the reservoir or fingering from the edge of the reservoir decrease the oil relative permeability around the wellbore and hence reduces the ultimate oil recovery from the reservoir. High water movement in the wellbore of unconsolidated sandstone reservoirs creates turbulent flow which enhances the dislodgement of formation sand grains causing formation damage to reservoir rock in the vicinity of the wellbore. The objective of this study is to investigate wellbore and reservoir conditions responsible for early water breakthrough in edge water drive mature sandstone oil reservoirs and their effect on oil recovery factor from these reservoirs. This study was conducting by preparing decline curves for several wells in a strong water drive reservoir which were analyzed in order to calculate the recovery factor for the studied reservoirs. Pressure build up test analysis was also conducted in order to calculate and measure the amount of wellbore damage resulted from the mixing of the intrusion edge water and reservoir fluids in the vicinity of the wellbore. The results of this study indicated that the high water movement in all the studied wells in the reservoir was due to the high oil withdrawal rates resulted from improper perforation density. It was observed that the water movement and the resulted damage near the wellbore was severe in open hole completions compared with cased hole completions. Improper well spacing was also another factor which contributes to an even edge water movement into the reservoir. It was concluded that uncontrollable edge water drive was the main cause of low recovery factor in many unconsolidated Libyan sandstone oil reservoirs.