The tail production in oil and gas fields usually means that CO2 emissions expressed as kg/bbl increase as production decreases. Frankly, tail production, with very high emissions per barrel, should be avoided to improve energy efficiency and limit CO2 emissions. Using CO2 for increased recovery, which to a large extent will remain stored in the reservoir, may be a better choice, and at the same time the infrastructure for CO2 storage can also be established.
Most people agree that we need to reduce carbon gas emissions now for our future generations. With this in mind, Carbon Capture Utilisation & Storage (CCUS) stands out as an important solution, if we want to keep our standards of living and mitigate climate change impact. More than 60 different CCUS projects are in progress in Europe. Worldwide, regulators follow the Paris Accord on climate changes and facilitate CCS financially representing business opportunities for the heavy industry in general and particularly within oil and gas. So, if we have the method to accelerate meeting net-zero target, why are we still moving forward slowly?
Carbon Capture and Storage (CO2 storage) Challenges
In the latest article in the OGV Energy magazine, our Advisor Geology, explained.
“There are several challenges to overcome when it comes to CCS:
1. Capturing of CO2 is technically challenging and costly task. If we are going to be successful in carbon capture and storage (CO2 capture and storage), large-scale emissions must be captured from cement factories, energy production, refineries and ship engines to mention but a few.
2. Creating the infrastructure to make CCS economic should largely depend on use of the current oil and gas infrastructure. The re-use of appropriate facilities, however, requires detailed further studies.
3. The safe storage of CO2 in adequate aquifers at sufficient depth and reasonable distance from pumping stations is vital. Offshore storage is preferred, but some countries may opt for onshore storage.
While the options #1 and #2 involve great challenges, option #3 has already been tested and is actually widely used already.
A recently launched Norwegian multidisciplinary research effort (180 mNOK LinCCS) aims to solve the CCS challenges and could offer cost efficient solution for the entire carbon capture and storage supply chain. A collaboration between a number of operators, research institutions and service providers aims to meet the expectations of the Paris accord. A multi-disciplinary project is essential, since the challenges are complex, and the number of disciplines are great. In addition, the desire to store clean energy, such as hydrogen, ammonia and natural gas, only adds to the complexity.
Turning North Sea into carbon storage tank
Looking into the future, we can expect great demand for CO2 storage offshore. A plethora of saline aquifers commonly associated with oil and gas production are to be found on the Norwegian Continental Shelf (NCS), offering significant CO2 storage capabilities. The challenge is to find the best opportunities for storage in terms of injectivity, capacity, facility and end of field life.
Key drivers for carbon storage are the size of aquifer; and the large depositional systems with significant clastic input that means accumulation of massive sands. Such reservoirs have yielded long term production of oil and gas and are in some fields at the end of production life, offering safe storage in the vicinity of significant infrastructure, such as pipelines and huge GBS platforms, that can serve for many years to come.
In the North Sea, there are three massive depositional systems representing different ages of deposition and containing many fields at different stages of depletion. These are:
1. Statfjord – Brent reservoirs; Statfjord-, Gullfaks-, Oseberg-, Snorre fields, Early to middle Jurassic deposition from south to North
2. Sognefjord, Fensfjord Fm late Jurassic delta building great depositional thickness of clastics from east to west, based on Caledonide denudation.
3. Andrew, Forties, Frigg/ Tay and Alba sequences constitutes a huge depositional system from the west into Central and Northern North Sea during Paleocene and Eocene.
Each drilled structure reveals a find or not, and with a nearly complete coverage of 3D seismic across the North Sea, this means that there is a very good control of saline aquifer reservoirs. The Norwegian Petroleum Directorate (NPD) has mapped and published thicknesses of different depositional clastic sequences, which could qualify as CO2 storage.
Equinor together with Shell and TotalEnergies is operating the first CO2 storage facility incorporating the Johansen Fm saline aquifer. This is a costly project and heavily subsidised and without reuse of oil and gas facilities.
The re-use of facilities may provide more cost-effective solutions. In Denmark, Ineos is working on CO2 storage in the Nini West field, which is at the final tail end of production, however without a final investment decision to date. The project is known as Project Greensand and is financially backed both by the government and consortium of international companies and research institutes.
Carbon storage for improved oil & gas recovery
Increased recovery has been a measure of economic success throughout oil and gas’s history, and vast efforts have been put into different methods. Pressure support, water and gas injection, extended reach wells and horizontal wells, have all increased recovery from 30% in the 1950’s to 60% in recent years. Since the 1970’s CO2 has been used for displacing oil to increase recovery in the US, with CO2 at reservoir conditions having similar fluid density as oil, and in certain conditions becoming miscible, therefore making it ideal for displacing the oil.
An economic game changer can be found if we allow Improved Oil Recovery (IOR) as a part of the CO2 storage project. The use of CO2 for displacing oil will increase recovery by 7% as a rule, representing a very good economic return.
Norwegian Petroleum Directorate and Operators on the Norwegian Continental Shelf have been very successful in increased recovery, gaining record breaking results – positive when considering resource utilization where an IOR Award is presented to the best company every year. However, maybe this should be reconsidered when 95% or more is water coming out of the production wells – something which is common.
To conclude, we see great opportunities for profitable CCUS, combining existing infrastructure in areas of extensive oil and gas production, where huge saline aquifers are located and opportunities exist for CO2 injection as an IOR technique.