Using CO2 Enhances Oil Recovery In TT

(Trinidad and Tobago Newsday, 15.Apr.2021) — In February 2021, the Ministry of Energy and Energy Industries (MEEI) announced that Cabinet agreed to establish a carbon capture and carbon dioxide (CO2) enhanced oil recovery (EOR) steering committee, responsible for managing the implementation of a large-scale CO2-EOR project in Trinidad. Potential oilfields identified for this project include those run by Heritage in Point Fortin, Guapo, Gran Ravine and Forest Reserve. The committee comprises members from the MEEI, Heritage, UWI and NGC.

What is EOR, what does it have to do with CO2 and why is this a big deal?

Oil can be produced from the subsurface in three phases: primary (production by natural reservoir pressure or artificial lift devices like pumping jacks), secondary (using water or gas injection to displace oil and push it towards production wells) and tertiary (or EOR, when the first two methods are no longer deemed useful). On average, for onshore Trinidad, primary production only extracts about 15 per cent of the oil in the reservoirs. In terms of secondary production, waterflooding has been used in many fields over the years with varying levels of success. Therefore, billions of barrels of confirmed oil and thus billions of US dollars remains in the ground.

For decades in TT, EOR has been touted as the solution to produce significantly more of the oil that we have already discovered but cannot produce with primary or secondary means. However, the difficult economics and technical challenges involved in these projects, combined with sometimes unpredictable geology, has led to almost no EOR projects in the country.

There are three main types of EOR: thermal recovery, chemical injection and gas injection.

In thermal recovery, steam is injected into the reservoir via wells, to lower the oil viscosity and enable it to flow more easily. This is a major method used in Venezuela and the US, especially for heavy oilfields.

Chemical injection adds complex polymers or surfactants to the reservoirs which in essence, lower the surface tension of oil so it can flow easier. This is the least used method of EOR globally – the techniques are newer, these chemicals are incredibly expensive (compared to water, steam, CO2) and there is always a fear of environmental damage.

Gas injection can introduce natural gas, nitrogen or carbon dioxide (CO2) into the reservoir. The gases increase reservoir pressure, helping push more oil out. CO2 has the added benefit of being somewhat soluble in oil (similar to how CO2 dissolves in a soft drink), which helps reduce its viscosity as well.

In the US, CO2-EOR accounts for over five per cent of oil production (~350,000 barrels per day), and the Department of Energy estimates over 130 billion barrels can technically be recovered with this technique. The graph shows that CO2 has been the EOR technique that has grown the most globally for the last 50 years.

CO2 injection was first used in the 1970s. Right here in Trinidad, during the ’70s and ’80s, it had been tested on fields in Oropouche, Guayaguayare, Brighton, Barrackpore and Forest Reserve, among others. Unfortunately, further development of EOR techniques in Trinidad were stalled for decades for a variety of reasons including complex geology and engineering, unfavourable economics, lack of regulatory incentives and of course, politics.

One of the logical reasons to employ CO2-EOR in Trinidad is that we are one of the highest CO2 emitters per capita, due to the many industrial plants at Pt Lisas, as well as Atlantic LNG. If we could only capture and transport the CO2 produced from these plants, in a safe and cost-effective manner, instead of venting it to the atmosphere, we would have a mutually beneficial solution.

Not only could the CO2 be used to get additional oil out of the ground via EOR, but some of the CO2 that is injected, can remain permanently in the ground, forming a carbon sink. Experimental models have shown that the CO2 emitted from the production of oil could be less than the amount of CO2 injected for EOR, making the process carbon neutral or even carbon negative.

As a signatory to the Paris Climate Change Agreement in 2018, TT committed to reduce its emissions of greenhouse gases. CO2-EOR is a potential win-win to produce more oil and also sequester CO2 that would otherwise end up in the atmosphere.

Hundreds of students at UWI and UTT have studied these topics in detail and many of the lecturers are bona fide experts in this field. However, despite many companies attempting projects in Trinidad over the decades, few have taken off and fewer still have achieved tangible commercial and technical success. This is why the formation of the steering committee instils some much-needed hope for EOR to finally take off in TT’s declining oil sector.

Some recent success has come from Columbus Energy, taking their shot at EOR. In February 2021, they announced the results of a pilot CO2 programme at the Inniss-Trinity Field. They have stated that the project was a technical and commercial success and consider this a successful de-risking of this type of EOR in Trinidad.

Significant challenges still exist in CO2-EOR that the energy community is well aware of:

What makes some fields good candidates? What kind of percentage increase in production can be expected? Where will the CO2 come from? How will the gas be transported to the oilfields – truck, pipeline? If pipelines have to be built, who will pay? Will CO2 pose environmental hazards? If other sources of CO2 are found (such as industrial producers like Massy Gas), does this negate the sequestration effect? Of course, what are the economics like for all these scenarios? What fiscal incentives and oil prices are needed for this to work? And finally, given all the challenges, what is the timeline to realistically conduct a large-scale CO2-EOR project in Trinidad?

As previously offered, the GSTT’s thousands of members and affiliates are capable and willing to freely advise the government on any aspect of EOR. We hope these questions help to prompt the steering committee’s initial conversations.

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Content submitted by the Geological Society of TT, a professional and technical organisation for geologists, other scientists, managers and individuals engaged in the fields of hydrocarbon exploration, academia, volcanology, seismology, earthquake engineering, environmental geology, geological engineering and the exploration and development of non-petroleum mineral resources.