Thanks to continuing advances in reservoir characterization, technology and innovative thinking, many oil fields around the globe have “grown larger” in recent decades.
John Sneider, president of Sneider Exploration Inc., documented examples of mature field growth 20 years ago and recently revisited the topic to focus on mature giant fields.
This updated analysis is detailed in chapter 4 of the new AAPG Memoir 125: “Giant Fields of the Decade: 2010 – 2020.”
Companies developing fields typically go after the low-hanging fruit first – reserves that are easiest to exploit, are the most prolific and require the fewest wells. In many cases, there might be large reserves remaining that are more difficult to produce.
Sneider’s original paper saw reserve additions from shallower and deeper pools, lateral extensions, infill drilling of compartmentalized reservoirs and accessing poorly swept or bypassed zones. Fields with low reservoir energy were found to be good candidates for improved oil recovery, he said.
A New Look at Old Data
He said elements essential to adding reserves haven’t fundamentally changed in the last 20 years. The key elements are improved reservoir characterization, the use of new technologies and innovative thinking.
Better reservoir characterization can arise from “looking again with new data gathered over the years … better data … (it) offers a more complete look,” Sneider said.
If you want to find new reserves in a mature field, you need to look at it with a fresh set of eyes, kind of like you are appraising a new field. You must look at what potential remains in the field.
This is helped by the fact that technology is always advancing, Sneider said.
For example, visualization technologies have advanced from 3-D to 4-D seismic, allowing explorers to view changes in fields over time.
“We can see things we never saw before,” he said.
Fiber optics are not a new technology, but their application in the oilfield is expanding. There is a lot of data, and advances in data analytics and artificial intelligence have a lot of potential to help use this data.
In-place monitoring of wells with fiber optics placed in the casing offers a new way of looking at temperature and acoustic changes in real time.
“It’s going to be interesting,” Sneider said.
Other technological improvements have emerged in drilling and completion.
Improved stimulation technologies have allowed operators to produce from tighter and tighter reservoirs. Advances in artificial lift enabled operators to produce at higher water cuts, and better high pressure/temperature equipment has allowed them to drill deeper in existing fields, he said.
Sneider said the third key element is innovative thinking, adding that it’s not a single improvement, but can involve many ways of approaching a problem after first identifying the problem.
At Forties Field, model revisions increased reserves and significantly prolonged production, he said.
One challenging instance there involved using artificial lift and storing enough diesel for the operation. The operator took a challenge – a shallow gas hazard – and turned it into a source of gas to fuel the artificial lift.
It is common to see smaller companies take over mature fields. Creative financing can allow smaller companies access to needed capital to re-develop large fields.
‘Major Revelation’
A key driver for expanding untapped reserves often is a “major revelation or trigger – a change in the status quo,” he said.
This can come about when assets are sold, he said.
When a company gains a new asset, companies typically assign people to restudy the field.
This provides new eyes and a fresh perspective on the field.
In Oman, the challenge was that “they weren’t finding new oil fields, so they had to work with what they have.”
EOR provided way to add “new” reserves in giant fields like Fahud, Marmul and Qarn Alam, Sneider said.
“Despite differences in geology, fluid properties and reservoir quality, these projects found success through common themes of detailed reservoir characterization, innovative thinking, and applying new technologies such as gas- or thermal-assisted gravity drainage, polymer floods, high-resolution stratigraphic studies and probabilistic reservoir characterization,” Sneider said.
“Lessons from analogous fields promoted success and compressed the development timeline of a miscible flood at Harweel Field. At Mukhaizna and Khazzan fields, detailed reservoir characterization and advancing technologies aided in the successful development of giant accumulations previously considered too complex to exploit,” he said.
As technology, techniques, and new ways to apply them in the industry continue to advance, many of these giant fields will continue to “grow,” he said.
The challenge now is to develop these fields in a more sustainable manner. While the world will still need hydrocarbons for many years, there is also a demand for a reduced carbon footprint. The key elements of accurately characterizing the geology, leveraging new technology and thinking creatively will help us meet that challenge.