We also know that water injection began in 1964 and the water cut had reached about 35-37% by 2003---some 15 years ago, and it is almost certainly significantly higher now since more and more water flooding has been going on for the last 15 years. We know from the 2015 technical paper I link to above that the water cut has reached 98% in at least one area of Ghawar. And we know that Saudi Aramco has started a pilot CO2 EOR project to see if they can improve oil recovery----something that is usually done in very mature oil fields where the oil production rate is at risk of dropping.
Well first off, as I said before the EOR flood was conducted in a part of the field that has been completely swept, it has been close to injectors for 50 years. One of the SPE papers mentions that in fact the wells that were re-entered for testing had a zone of high oil saturation at the top of the well, the CO2 injection study is being conducted at the bottom of these wells where water saturation is high but there is still some minor oil saturation that they want to see if they can make mobile.
AlOtaibi, F et al, 2019. Remaining oil saturation measurements for CO2-EOR pilot in Saudi Arabia. SPE 188146 MS
And if you had read what the Saudis who are in charge of the CO2 injection project said you would not be suggesting that they are doing it because they need the extra oil production. As I pointed out above.
from the Kokal et al paper SPE 181729 MS I already mentioned twice
As part of Saudi Aramco's environmental stewardship program (Al-Meshari et al. 2014), the company has recently embarked on its first carbon capture, utilization and storage (CCUS) through a CO2-EOR demonstration project in one of its carbonate reservoirs. It is part of a multi-pronged effort involving the company's strategic carbon management program aimed at finding technological solution to reduce CO2 emissions. It must be emphasized that Saudi Aramco does not require EOR oil at a production level for decades to come, this project is being pursued primarily to demonstrate the feasibility of sequestering CO2 via EOR in the Kingdom.
The amount of water cut is not a number that is useful in determining remaining reserves. As both Rockman and I have pointed out on many occasions fields produce at very high water cuts (above 90% ) for many years, in fact many fields with decades of production history started out at high water cuts due to very high vertical permeability in the reservoir and an adverse mobility ratio.
What we do know is that OOIP by all estimates is somewhere between 190 and 210 Gbbls. And Aramco is pretty adamant that they will see at least 70% recovery from Ghawar. In another thread here somewhere I outlined what the total production from Ghawar had been in 2009 and then projecting the 5 MMB/d forward you end up with a total production number that leaves you with somewhere around 30 years or more at the current production rate. And the other key point is that the two largest reserve auditing firms in the world Gaffney Cline and DeGolyer and MacNaughton have audited all of SA reserves. The comment after the audit was that their assessment is not appreciably different from Aramco's and definitely not smaller. When the IPO enters the market those reserve audits will become public record either through the SEC if they list in New York or the London Stock Exchange if they decide to list there (or possibly both).