Digital Rock Physics: Discovering How Oil Moves Inside the Rocks May Be Key to Getting More Oil Out of the Ground
Despite the millions of barrels of oil being produced each day in the UAE – about 3 million to be exact – around 60% of the UAE’s oil is still trapped underground. This unrecovered oil is thicker than honey and held within the tiny, almost invisible pores of the carbonate rocks that stretch for miles deep under the country’s surface.
A team of scientists at the Masdar Institute of Science and Technology are determined to help harvest this oil, and to do it, they are studying the porous rocks in which the UAE’s hydrocarbons are stored.
The team, led by Dr. Mohamed Sassi, Interim Dean of Faculty and Professor of Mechanical Engineering at Masdar Institute, is studying how oil moves through the micro- and nano-sized pores of the underground carbonate rocks they are trapped in because, as Dr. Sassi explains, “The more we understand about how oil moves within these heterogeneous rocks, the more oil we can take out.”
While the UAE is focused on achieving sustainable development, and Abu Dhabi has even targeted producing 7% of its energy production capacity from renewable sources by 2020, the oil and gas sector are expected to continue to play an important role in the economy for the next few decades at least.
Given that the current average oil recovery factor worldwide is only about 35%, the UAE is potentially missing out on a significant amount of fuel to help meet rising global energy demand and power the UAE’s ambitious development plans. Last year BP’s Chief Executive Bob Dudley told The National newspaper that even just an additional 1% recovery from the UAE’s reservoirs is worth some $200 billion of value to the country.
In recognition of this untapped wealth, Abu Dhabi has been ramping up its efforts recently to improve the productivity of the country’s oil wells, with ambitious goals to increase oil recovery rates from 35% up to 70%. And Dr. Sassi’s research project may help the government achieve its goal.
The project, sponsored by the Abu Dhabi National Oil Company (ADNOC) and France’s Total, with the Petroleum Institute as a research collaborator, is dubbed ‘Digital Rock Physics.’ It will map the region’s carbonate geological reservoirs in order to produce an extensive archive of rock images at multiple scales.
“These rock images will be examined at the nano-scale level and a simulation will be created to understand the behavior of fluid flow in oil and gas reservoirs. This will lead to an increased knowledge of rock behaviors in the reservoirs and ultimately more effective and energy-efficient oil recovery methods,” Dr. Sassi explained.
More efficient recovery methods mean less energy lost in extracting oil, which is an extremely energy-intensive process. Current extraction methods involve three oil recovery stages: primary, secondary and tertiary or enhanced.
Primary oil recovery methods rely on the natural pressure of the reservoir to push crude oil to the surface, usually recovering up to 10% of oil from the reservoirs. In order to get the rest of the oil out, or as much of it as possible, secondary recovery with water and gas injection is used followed by enhanced recovery methods to achieve up to 70% of the original oil in place. During these recovery phases, steam, gas or chemicals are pumped into the reservoir in order to decrease oil’s viscosity, making it easier for the oil to be displaced and extracted under pressure.
The Digital Rock Physics project poses an energy efficient solution to the challenge of extracting more oil from underground carbonate reservoirs. Instead of pumping more gas or chemicals into the ground in an attempt to force the thick oil to percolate up to the surface, Masdar Institute’s research looks to the root of the problem – the rocks themselves – and has produced the first images of the micro- and nano-level pores in the UAE’s carbonate rocks.
Before the Masdar Institute team could study how fluid flows through the carbonate rocks, they had to first find the many below hair-sized pores. To do this, they injected the carbonate rocks with mercury to show that the carbonate rocks have both micro-sized and nano-sized pores spread throughout.
Using Masdar Institute’s state-of-the-art microscopy facilities, the team was able to image the tiniest of pores. They identified the rock’s pore networks and were able to generate 3-dimensional (3D) images of the rocks, mirroring the pore morphology and pore networks of typical Abu Dhabi carbonate rocks.
“We found pore sizes of 80 micron connected in an intricate network. We also found a distribution of pores below one micron, at 100 nanometers,” said Dr. Mustapha Jouiad, Microscopy Facility Manager and Principal Research Scientist, Mechanical and Materials Engineering Department, Masdar Institute.
Focused ion beam-scanning electron microscopy (FIB-SEM) technology gives an extremely clear 3D image of the microstructure of the porous carbonate rocks sections. FIB-SEM enabled the team to capture high-resolution images at the nanoscale level, helping them identify what is rock and what is pore space. These are images an x-ray machine would not have picked up. The Digital Rock Physics project is the first in the region to use FIB-SEM technology for 3D imaging and reconstructions.
“The behavior of how oil moves inside the rock changes when you are dealing with different size pores,” explains Dr. Sylvie Chevalier, Research Associate, Masdar Institute. “Oil in smaller pores is more difficult to get out, which is why we need to understand the complexity of the rocks and understand how fluid moves in these small pores.”
Once the team recovered the rock pore distribution – at the nano- and micro-level – they could see the pore channels. Then, using a computer simulation, they simulated injecting oil, water, and gas into the imaged rock pore network and observed how the fluids move.
Through the simulation, the team is working to determine the best way to dislodge the trapped oil.
“Hopefully, within the next year and a half, we will determine the most optimal and efficient techniques to displace the oil; techniques that can be scaled up and put to use immediately in UAE’s carbonate reservoirs,” Dr. Sassi stated.
The UAE’s increased oil recovery target is part of its long-term strategy of sustainable national development.
While the country is focused on diversifying its economy away from being hydrocarbon based and has even targeted producing 7% of its energy from renewable sources by 2020, oil and gas will continue to play an important role in the global economy for the next few decades at least. Demand for energy is expected to increase by 35% by 2035, according to the International Energy Agency, an increase likely to be met predominantly by fossil fuels.
“This research leverages Masdar Institute’s materials science and modeling capabilities to help the UAE achieve its ambition to exploit Abu Dhabi’s oil reservoirs to levels beyond the norm — to reach 70% recovery rates. Supporting the UAE’s energy system evolution with our industry and academic partners in this way is a key goal of the Institute,” explained Dr. Steve Griffiths, Vice President for Research and Interim Associate Provost.
Efficiently extracting and utilizing available hydrocarbon resources through the Digital Rock Physics research project and others can provide the UAE with the capital required to fund its sustainable knowledge economy transformation and its research and development into the critical technologies still needed to make renewable energy competitive and sustainable.
Additionally, with the enhanced understanding of the UAE’s oil reservoir through the DRP project, more suitable extraction techniques can be developed and utilized. This will help the UAE recover more of its oil resources with maximally efficient EOR techniques.
“By implementing efficiency throughout its fossil fuel supply chain, the UAE’s oil and gas industry can help steer the country on a more sustainable path,” Dr. Griffiths added.
Responsible stewardship of the country’s natural resources is part of the legacy of the late UAE Founding Father Sheikh Zayed bin Sultan Al Nahyan. He famously said: “We cherish our environment because it is an integral part of our country, our history and our heritage. On land and in the sea, our forefathers lived and survived in this environment. They were able to do so only because they recognized the need to conserve it, to take from it only what they needed to live, and to preserve it for succeeding generations.”
With Masdar Institute’s research efforts to improve oil industry efficiency and others to reduce carbon emissions and conserve precious resources, the UAE is working to keep its environmental and economic needs in balance. Both are crucial to help the country reach the next level of prosperity and progress.
News and Features Writer
16 November 2015