If the Scots want to go, let them. They too can leave without any deal and let them see how they get on.
paddyann have you heard of Global warming? It is something that the world has known about for several decades, although the news has obviously not got too far north. Global warming has been caused by the indiscriminate and uncontrolled burning of fossil tuels (like oil and gas) and left to increase it could kill all of us. The way to deal with it is to eliminate the use of oil and gas and leave it in the ground. The value of oil and gas in the ground that is never liked to be extracted is precisely £nil.
Speaking as someone who has worked in the oil and gas industry, as has DH. Giving a company a license to explore a certain area of sea, is not the same as saying that any oil or gas is going to be found or exploited.
The process is:
1) a licence is granted. This means that the company can survey the area to see if there are any structures in it which might contain oil and gas, despite research before hand, this can be a very imprecise science. Many of these license areas prove barren and are written off.
2. If there are suitable structures they need to be surveyed to see if they contain any oil and gas and whether they are likely to contain commercial quantities of those products. Many don't, so another clutch of licenses are wasted money. 3. The oil companies then need to work out whether the oil/gas reserves are recoverable at a cost that does not exceed the price the oil/gas can be sold at. Currently reserves being explored are more and more difficult to access and the platforms and technology to do so is more and more complicated and expensive.
So for every 100 licences granted, possibly as few as 10 are developed as operating oil fields.
Oil and gas production peaked in the late 90s and now is on a gentle downhill trajectory. There is now thought to be only one fully unexplored province in the North Sea, and that is Rattray and if you follow the link you will get an idea just how difficult and expensive both exploration and extraction will be, should commercial reserves be found. www.petroleum-economist.com/articles/politics-economics/europe-eurasia/2019/rattray-could-hold-the-last-great-north-sea-oil-reserves
The Scottish government (and you, paddyann) would be very unwise to rely on oil and gas to pad out your revenues.