RE: Scott226 Sep 2021 16:25
Your assumptions about pressures offshore in different stratigraphic zones are false. They vary to the same degree that they do on land. Basic physics.
With 100m of water you have 10 bar pressure on the seabed. In 300m of water, you have 30 bar. On land, you have 1 bar. Cascadura high pressure gas is about 280 bar.
Why in the world would a 9 bar or 29 bar or whatever else differential on the surface have anything do do with the pressures that are in the reservoirs of similar depths thousands of meters under overburden Scott22 ?
Answer is, they don’t. You’re just making things up.
It is not super complicated to produce from two separate zones in the same well, but it does cost more, and requires that the casing where the packers and production tubing are run are large enough in diameter to accommodate the double completion. With the low cost and desired simplicity of operations we have on land in Trinidad, it is cheaper and more efficient to just produce one zone at a time from different wells. You can always move up to higher zones also once you decide you will not produce from a lower zone anymore.
During testing, you always start at the bottom, pack off and move up. TXP sets permanent plugs moving up, and as such, it is not possible to go back down and produce from a lower tested zone once a zone above it has been tested. You could always mill a permanent plug in case someone wants to argue this, but this is not something you really want to do, or would plan to do.
We’re on land, all is so easy to drill, it’s super cheap to drill, we take the easy road and make the highest profit. Offshore, you have a limited number of slots, and limited life of production assets before it becomes to expensive to maintain the equipment and therefore may spend more cash upfront on multiple completion designs and solutions.
Google multiple zone completions if you want to understand more about it.