Oman’s portfolio of mature assets and complex oil and gas reservoirs in some of the world’s oldest, hardest rocks, means enhanced oil recovery (EOR) is vital to maximising the economic recovery of its reserves.
Petroleum Development Oman (PDO), which accounts for more than 70% of the Sultanate’s oil production and nearly all of its natural gas supply, says improved oil recovery technologies such as primary depletion and water injection add up to 25% to the recoverable fraction of its oil.
“This is simply too low and we are making a big effort to increase it substantially through enhanced oil recovery technologies,” said Raoul Restucci, managing director of PDO. “Our EOR team aspires to double PDO’s overall recoverable oil volume fraction to above 50%.”
In 2014, EOR will account for 11% of PDO’s production, but this is expected to triple to 33% by 2023. It is currently executing four EOR projects, and designing, engineering or testing a further 12 technologies covering the full spectrum of thermal, chemical and miscible recovery methods. A further six projects are under concept review.
Extensive analysis of PDO’s portfolio of fields has revealed substantial volumes of oil that can still be recovered through EOR, Restucci said.
“To turn this into reality, current EOR efforts with respect to research and development, field and pilot testing, and implementation of successful technologies will continue with the ultimate goal of providing all of PDO’s fields with a suitable EOR development.”
Thermal processes currently dominate this EOR portfolio, but rely on burning natural gas to produce steam for injection into the reservoir, which heats Oman’s heavy oil and reduces its viscosity.
“More and more projects will require thermal processes, in turn requiring more and more fuel gas,” Restucci warned. “This is unsustainable, especially bearing in mind the value of gas, the pervasive and increasing demand across Oman and the increasing shortfall of regional supply. We will not only have to discover new alternatives to gas, but also build on other EOR mechanisms.”
In one high profile example of innovation, PDO has successfully used solar heat in trials to generate low-cost, energy-efficient steam for thermal EOR at Amal West as an alternative to gas. The technology from the US’ GlassPoint Solar (pictured above) uses mirrors to focus sunlight onto heat receivers, all located and protected inside a glasshouse, converting this into heat for producing steam from water.
‘Solar EOR is likely to play an important role in the mix of EOR technologies (in Oman),’ according to a report from international accountants EY, published in January 2014.
Restucci reckons that proven technologies could help PDO reach an overall recoverable oil volume of around 40%. This figure could be further raised by other technologies under development.
Specific proven technologies included in field development plans (FDPs) – and currently in operation – include steam flooding in Amal and polymer flooding in Marmul. Others are in the process of being matured into FDPs – such as steam flooding in Amin and in Habur.
Restucci stressed that PDO still faces staff and supply chain challenges as EOR is both capital and labour intensive, and needs high technical expertise.
“We must also ensure that the benefits of our EOR strategy are spread across Oman through the supply chain. That means ensuring that key technologies, services, materials and components required for EOR are ‘Omanised’ as much as possible, while ensuring quality and cost; competitiveness,” he added.
PDO talks constantly to potential partners who can help it to execute its EOR strategy safely, reliably, efficiently and sustainably. Research and development for each of its EOR technologies is steered and pursued by its team through its partnership with Shell, universities, joint industry ventures and strategic alliances with relevant parties.
The asset integrity challenge posed by the risk of corrosion in EOR projects is substantial. The injectants PDO uses to extract oil are very aggressive and can produce highly corrosive compounds.
“The technical know-how offered by companies such as DNV GL is valuable in helping us to progress, so that we can identify those technologies and techniques which are best suited to our operations,” Restucci said.
“Currently, we have a contract with DNV GL, and the company has helped us on a number of important projects such as integrity assessments of all our gas facilities. It has also worked on assessing and providing solutions for Duplex Flow Lines and issues with insulation joints, and has provided competent staff to conduct some corrosion control, monitoring plans, material selection and pipeline integrity works.”
Which EOR solution?
“We place a premium on EOR solutions which underpin the robustness of our long-term surface and subsurface development and infrastructure plans,” Restucci explained. So what might new EOR technologies, or refinements to existing technologies, be needed for?
“Each field has its own characteristics and we are constantly assessing which is the best applicable technique, taking into consideration rock properties and mechanics, viscosity of oil, and the depth, pressure and temperature of the reservoir and so on,” he said.
“It is only by methodical data gathering, analysis and testing that we can decide on the best technology to be deployed in each case. Sometimes, it will be necessary to modify our approach and, on other occasions, to move beyond the boundaries of conventional EOR wisdom.”
In one example, PDO has been running a special chemical test following earlier steam trials in its Habhab ultra-heavy oil field. “This chemical has never been used before in our industry, but we believe it could lead to much increased yields from complex heavy oil and tight reservoirs. Several studies were conducted relating to material selection, environmental management and special chemical handling,” Restucci said.
“PDO experts are also working on several other ‘promising’ and ‘emerging’ EOR technologies,” he added. The promising category comprises technologies not yet ready for application on a full field scale and are tested in field pilots or injectivity trials in the field. Examples include an alkaline surfactant polymer pilot at Marmul and a chemical enhanced waterflood pilot in Lekhwair.
The emerging EOR technologies remain in early phase laboratory testing. These have been evaluated as high-potential additions to the proven and promising ones in terms of cost-effectiveness and efficiency.
“It must be emphasised that extracting residual oil is an expensive process so we are concurrently driving ‘lean’ continuous business improvement practices across all our operations and key processes,” Restucci said.