“Cantarell and Ku-Maloob-Zaap are like unique jewels,” says Edgar Rangel Germán, Commissioner at the CNH. “The fields in these areas originate from a meteor strike that hit the Earth 65 million years ago, which made extremely interesting geological formations. The meteorite fragmented into thousands of tiny pieces. This has led to a geology in Mexico’s shallow water basins that is extremely tight, with millions of fractures and high permeability. This is what has caused the production rate at Cantarell to be so high for so long. More than 30 years after production began at Cantrarell, new wells drilled there today will reliably produce 3,000 to 4,000 bbl/day.”
Rangel Germán says that there are most likely around 15 billion barrels remaining at Cantarell, and around a quarter of this will be retrievable with current technology. He explains that in the early years of Cantarell, oil was produced from the rock fractures, but now much of the remaining oil is trapped in the solid rock, from which it will be difficult to extract using current techniques. However, he believes that modern enhanced oil recovery (EOR) techniques such as thermal recovery, gas injection, CO2 injection and chemical processes will help Pemex to find the correct recovery solution in the years to come. “There’s a lot of oil still remaining, but it is difficult to recover it from the matrix system. However, once the correct techniques are defined, there will be a big jump in the Cantarell recovery factor.” Rangel Germán goes on to explain that there is an ongoing debate between the CNH, Pemex and the reserve certification companies about exactly which potential resources at Cantarell can be incorporated into the NOC’s reserves. This issue stems from Pemex’s need to prove that EOR techniques will work at Cantarell through pilot projects and studies. Once these have been presented, additional reserves from Cantarell will be able to be incorporated into the NOC’s books.
In CNH figures on the current investment levels at the Cantarell field, the regulator asserts that Pemex will spend 25% of its allocation to exploration activities. Given the maturity of the field, it seems strange that Pemex is spending so much on exploratory activities, but Gustavo Hernández García, Subdirector for Planning and Evaluation at Pemex E&P, explains why the figure is so high. “In this case, exploration means going deeper into the formations at Cantarell. When exploring the original Cantarell formation, we found another reservoir at a greater depth, which has the same reservoir pressure and the same oil as the original formation. We expect to delineate this entire new block and start producing from there soon.” Hernández García explains that there are three stages to exploring this area: assessing the potential of the reservoir, incorporating the reserves, and finally delineating the reserves. Work being done at Cantarell is mainly in this final stage, which is probably why the CNH classifies it as exploration.
Hernández García has a different interpretation of how much oil is remaining in Cantarell, saying that Pemex currently has 3 billion barrels certified by the certification companies, but that the NOC disagrees with their results, believing that there is more recoverable oil at Cantarell than the certification companies by around 9.5%. However, Hernández García says that this is a standard divergence for the industry.
According to Hernández García, more than 80% of Cantarell’s 3P reserves are classified as proven. By concentrating on adding more volume to the existing reserves by perfecting EOR techniques, he believes that the size of the recoverable reserves can be increased by between 5% and 10%, while production remains stable at between 400,000 bbl/day and 500,000 bbl/day. He believes that this will be the biggest challenge at Cantarell for the years to come.
Q: What is your perspective on how much oil is still remaining in Cantarell, and how much of it can be produced?
A: “We have so far recovered 42% of the original oil in place, and the projections that we have allow us to establish that we are going to recover more than 50%. There is still around 10%, which is around 3.5 billion barrels of oil, which will be produced in the next 20 years or so.” - Carlos Morales Gil, Director of Pemex E&P