I'm a jr. reservoir engineer in an oil company. Our company intends to perform a project to enhance oil recovery in our field. Regarding to that purpose we plan to inject gas to reservoir. This methods have been used before, but now we want to find out about the original/first gas breakthrough, to determine injector to producer flow relationship, quantify the amount gas flowing from the injector to a specific producer and measure flood wide reservoir preferential flow trends. For that purposes we use gas tracers, in this matter we use PFC (perfluoro carbon) and SF6 (sulphur hexafluoride). However, we still have some obstacles which are:
1. When we inject gas + gas tracers to the injector well and the gas + gas tracers produced in the producer well. How can we determine the real gas from the gas injection from the gas comes out from the reservoir? Since, all of the gas from the subsurface will mix together with the tracer (not only the gas injection).
2.  If the producer well use gas lift, how can we calculate the gas lift interference? Or how can we avoid gas lift interference?
3. If in one injector well there are two reservoir that are commingle, should we use different tracers with one-go gas injection or each at a time?
4. If we group the producers wells by distance in three rows, thus we have 1st row (nearest wells from the injector well), 2nd row and 3rd row (furthest from the injector well). When monitoring program is performed, and the gas injection has been running, we plan to open 1st row, first. My question is if we open the 2nd row and shut the 1 st row wells, should we still take samples on the 1st row wells ? If so, what parameters can we get and on what purposes ?