No good, you would need an extension at £3.40 single/£4.70 day return except if either leg of the journey is before 0930 M-F in which case £5 day return or if travelling on a weekend in which case £4.40 day return. Cheaper to use Oyster but you would have to come off at Rainham Essex to touch in eastbound and touch out westbound, and would be liable to miss your train.