Abstract: Through Tubing Rotary Drilling (TTRD) technology a cost efficient infill drilling technique commonly applied in matured field. Offers means of prolong use of existing completion by exploitation of isolated marginal reserves from single (multiple) drainage point(s) either by concurrent commingled or sequential production as technically and economically feasible. The inherent negative aspects of TTRD drilling on existing main-bore completion and expected continuous use of it beyond its designed functional requirement suggest re-completion. When should this be executed? The critical aspects been relatively exhaustive, justifying the need for re-completion was utilized by applying decision analysis to model when to re-complete the well from a deterministic view. The first decision tree solution adopts optimizing segmented quarterly re-completion time and the other accounts for flexibility in time of re-completion by properly depicting subsequent alternate decisions to be taken from the planned exploitation of more by-passed marginal accumulation from a specific well within technical limits.