Per pm - If you have an oilfield with water drive and gas cap, and through gas coning (or gas production if you only had a thin oil rim and this was not the primary target) you produce a significant volume of gas, then the water support can push the oil column up

Please either pm me, or post a question on the forum - but not both in future. Generally I prefer the forum, as everyone then benefits (hence why I repeat my answer here)