In the 737-300 simulator at max structural take off weight ISA sea level, with engine flameout at V1 and level acceleration height 1000 ft, it takes around 11 miles to reach flaps up single engine clean speed before resuming climb OEI.
Some operators do not assess obstacles more than 15 miles out and runway analysis charts do necessarily state how far the obstacle survey is valid. One European charter operator I worked for stated they expected the pilot to use "Airmanship" beyond the stated survey path
