Sustainable enhancement

Enhanced oil recovery or EOR is sustainable, let there be no doubt about that. Sustainable business has been defined in the following way: “Sustainability is related to the integration of environmental, economic, and social dimensions towards global stewardship and responsible management of resources.”

This article will explain why EOR is a sustainable and necessary phase in the world’s energy supply. By now it is common knowledge that it is no longer possible to obtain easy oil. Recent exploration is not nearly as successful as it was 50 years ago as all the big fields have already been found and presently, most of them are even on the decline. It is also well known that alternative energy sources and wide scale unconventional developments are not yet technically, socially or economically viable to be able to compete on the same level as oil. EOR fills the gap for the coming fifty years until these technologies have become competitive enough to replace fossil fuels.

EOR cares for the responsible management of resources in the following four ways:

• It gets more reserves out of existing fields and extends the production
• The components (like CO₂ or water) are recycled as much as possible
• EOR cannot succeed without the development of local talent
• The fields can be developed faster and long tails of high water cut oil production are eliminated

Get more reserves and extend the production from existing fields

This concept may seem obvious, but it is a crucial one that is more complex than it appears. The abandonment of an oilfield is a strategic decision. Because the cost of EOR is quite high, making the choice to utilise EOR and get more oil out of an existing field is not an easy one. The cost per EOR barrel is significantly more than that of a ‘greenfield barrel’. If chemical EOR is chosen, chemicals, facilities (e.g. water treatment, pumping, mixing, emulsion breaking) and in some cases even the financing of more wells will be required. In the case of Thermal EOR, construction of new production facilities will be needed in addition to water treatment and heaters. Finally with miscible EOR, new CO₂ resistant flow-lines and compressors come into play to create the largest expense. Once these investments have been made it will then take longer to get the ‘EOR oil’ out of the ground, because of the amount of time it takes for the flood to reach the producers. All in all, the economics of an EOR development are generally more challenging than that of a greenfield development. That being said, there are many upsides and fewer subsurface uncertainties in choosing chemical EOR than in an exploration venture. This makes it is easier for the operators to see where their money is going.

Figure 1. Project approach for EOR. All elements are being de-risked starting in the laboratory, coreflooding, field testing and piloting. only once a phase has successfully been completed, the next phase can begin.

Use produced water for cleanup and injection

EOR developments are being designed more and more often as closed systems so that as elements of the development, like water, are recycled as much as possible. The produced water is being cleaned, treated and even used for re-injection. This ensures minimal impact to shallow aquifers or surface water like rivers, lakes and seas. In the case of a miscible flood, the CO₂ is also separated from the production stream and re-injected after several years. This must also be taken into account when the project has a carbon capture and a storage element.

Because most EOR developments are executed on mature fields, there is an aim to gear up for a clean abandonment, and to be as environmentally conscious and friendly as possible.

Local talent and resources capability enhancement

An additional factor and upside to EOR is that it is much more labour intensive than a greenfield development. An EOR development requires more operators for quality control and system management. So far, EOR service providers have been training the local talent for challenging jobs, such as chemists, operators, analysts and process engineers that are needed in chemical EOR. Furthermore, there is a larger logistical side that must also be staffed. Altogether there is significantly more manpower required in an EOR development than in a greenfield development. Because of the relatively large incremental EOR reserves, it is still worthwhile for the operator to embark on these developments albeit the culture in such a company must sometimes change and shift its focus to quality instead of quantity.

Shortened development time

EOR developments increase the reserves in the field, but because of the flood approach to the development, it also accelerates the tail production. Production that was first trickling in at a high water cut in the final years of the field life is now swept during the flood. An EOR flood can take anywhere between three and nine years depending on the method, well spacing and fluid properties, among other things. For a lot of operators the choice between production in the coming nine years versus production in fifteen years time, which will be the case with greenfield development, is an easy one to make.

The EOR method of oil recovery is also more thorough; once the EOR flood has been finalised, there is virtually nothing left in the field that can be extracted, unless it were to be mined. Therefore, the operator can plan for a proper abandonment, assured that the field has indeed been properly produced to its maximum.

Figure 2. Chart portraying the spectrum of chemical EOR possibilities. Higher incremental recovery require more complex EOR methods.

Choosing EOR over conventional or greenfield development

So why does not every oil company consider EOR for all of their fields? For starters, EOR is more expensive than greenfield development, and since most companies hope to find a new field, EOR is immediately put on the backburner. The average unit technical costs or UTC’s in EOR are between US$ 15/bbl for polymer floods and US$ 35/bbl for surfactant and thermal developments. When compared to US$ 5/bbl UTC for a conventional development, it is understandable why companies are hesitant to choose EOR. Secondly, the incremental oil production is realised three years later than with conventional developments due to the flooding characteristic of EOR techniques. This hurts economics where early revenue is essential. Furthermore, once a company decides to get involved in EOR, the culture of the development needs to be changed. Because EOR is more about quality and not shear quantity, quality control becomes much more important and manpower has to increase.

All in all the gains of EOR are certainly present, but require a long-term financial commitment combined with a willingness to transform the company for the better. However, once this is achieved, the life of the company is secured for another twenty to thirty years longer than it would be with conventional developments. PDO Oman is a good example of a company that successfully took the ‘EOR plunge’ and is now set up as a first time mover.

Getting specialist support

Luckily, companies do not have to undertake these developments on their own. There are independent EOR service companies that assist and work with the operators to make the changes that are needed as easy and seamless as possible. Azuren is one of these companies. It is an independent EOR technical services and consultancy company that specialises in waterflooding, thermal, miscible and chemical EOR.

The company works with clients to develop the best EOR development. This often starts with a screening of all the fields in an oil company’s portfolio in order to determine what EOR methods are possible. Heavy oil fields are more responsive to thermal and polymer EOR, while light oil fields are better suited for CO₂, miscible, surfactant or water flooding. Once the EOR method has been determined, more detailed screening can take place. This can be done in the laboratory by running phase behaviour, core-flooding and compatibility experiments. Once a recipe or, in other words, an EOR method has been determined in the lab it is ready for the field trial, which usually consists of a one-well test using small volumes. As soon as this is accomplished, a small or partial development can be planned. Operators are partial to pilots, but it often advised that the pilot be able to pay for itself with the incremented oil from the field trial in order to facilitate and set in motion the change in culture within the company. Expensive pilots that produce only data and no revenue are seen as a burden by management and are not a suitable way to extend the life of the field or company.

Once the partial development is successful, it can be scaled up to a fully phased field. This phasing often is essential to the economic success of the project.

EOR is an exciting and technologically challenging future for many assets. It can bring significant value, stability and quality to the companies that are willing to take the ‘EOR plunge’. This ‘plunge’ does not have to seem daunting, because, fortunately this exciting risk can be taken and realised with the service of specialist companies and all the skill and expertise they bring to the table.

Written by Jan Nieuwerf, Azuren http://www.azuren-eor.com, the Netherlands

Read the article online at: https://www.oilfieldtechnology.com/drilling-and-production/27122013/enhanced_oil_recovery_operations_a_sustainable_phase_in_securing_global_energy_supply/