Developments to watch at the University of Houston

Oil & Gas Engineering caught up with Dr. Ramanan Krishnamoorti at the University of Houston (UH). Krishnamoorti is chief energy officer at UH, responsible for integrating the educational, research, and industry partnerships that make up the university’s energy initiatives. He spoke about several technologies in development at UH.

Speaking about exploration technology, Krishnamoorti said that on the exploration side of the oil and gas industry within real-time monitoring, there is focus on micro-seismic technologies and seismic signal inversion. These technologies involve sending sound waves into the rock and receiving the acoustic signals that are reflected back to the surface. Doing this provides opportunities to study and analyze what is being reflected back from the subsurface.

This is an open-ended technological investigation. The university has been working on sophisticated algorithms that have become more prevalent and available to understand how reservoirs are changing geospatially as well as over time. Another area of investigation is how reservoirs are changing in relation to geospatial characteristics and recovery characteristics. The university is undertaking this major area of research using its unique facilities and capabilities.

Distributed acoustic sensing

Instead of using sound waves generated from the surface that are reflected within the formation, researchers can now send an acoustic signal through a fiber-optic cable within the well and the reservoirs, examine and analyze the returning signal, and thereby understand more about the reservoir and the integrity of the well from which the oil is being extracted. This is becoming an important technology for the work being done in unconventional fields. With this technology, researchers are able to investigate deeply into these horizontal wells to examine the rock and fluids.

In offshore exploration, a big challenge is understanding well integrity as well as the cementing being done with most of these wells. Another important issue is knowing the state of the cement as it sets and the stresses in the cement throughout the life of the well. Using distributed acoustic and electrical sensing along with smart cement—which becomes highly sensitive to electrical and optical signals because of nanoparticles dispersed in it—is becoming a new paradigm the university is pushing forward.

Using real-time data

On the production side, the university is researching reservoir engineering and stimulation to better understand reservoir management and estimation. Large-scale computers and sophisticated algorithms raise the bar on data management. Until now, companies have been known to extract as much as 3-5 terabytes of data per day from their wells, only to store it away, never to be analyzed or seen again, mainly because the data do not necessarily-or directly-translate to usable information.

Now, data management technology can rapidly convert these data into real-time well monitoring and send actionable information back to the drilling and reservoir engineers so they can make intelligent decisions about where to drill next, and about production methods. This technology can be used in new and mature reservoirs to enhance oil and gas production where extraction is poor due to low permeability and low recovery factors because of a variety of engineering challenges, including thief zones and bypass areas.

Nanotechnology aids production

Another technology that can be employed is nanotechnology, which can enhance reservoir imaging, stimulate wells, and improve tertiary recovery processes. This can be used to enhance recovery, stimulate and reduce viscosity, and profile modifiers within wells and reservoirs. Nanoparticles are simply solid particles, typically 100 nanometers in diameter, or 100 times smaller than the 10-micron-wide tunnels they traverse. Using nanoparticles for enhanced oil recovery has not reached a commercial level, as more research and testing need to be done; however, commercial application should be within 4-5 years.

• Nanoparticles can used in reservoir mapping usually performed by tracers in conventional and unconventional reservoirs. This works by putting a tracer into the well to identify where the oil is, its quantity, and how the pores are connected in the rocks. The nanoparticles are far superior and more robust in providing a quantitative analysis tool than the conventional way of using tracers of either fluorescent or radioactive materials and then watching them come out. This imaging data when combined with the acoustic and seismic data can start to fully characterize how a reservoir is constructed.
• The advantages of the nanomaterials over conventional methods are that they can transport through the rocks effectively and don’t suffer from chemical reactions within the formation as the other tracers would. Furthermore, the integrity of the data is much better. The nanomaterials are better reporters than the conventional tracers because they have been designed with a specific signal, can be pumped into the reservoir in mass quantities, and can be easily re-extracted. Each nanoparticle can be tracked, and when all the particles are added up, the data show the structure of that entire reservoir.
• This can be done with 100-times less material, leaving a smaller environmental footprint in the process.
• Magnetic nanoparticles can also be pumped into the well and used as highly sensitive reservoir imaging tools-much as we use magnetic resonance imaging (MRI) contrasting agents. At that point, we can put an instrument resembling a conventional MRI machine inside the well casing and see exactly where the oil is in the reservoir. This is a new area of research: developing new magnetic nanoparticles that can penetrate deep into the formation, and analytical tools to help quantify the oil and then determine the formation structure.
• For a tertiary recovery method, which is essentially enhanced oil recovery, nanotechnologies can be used to affect the viscosity of the water-make it thicker-and then push out the oil more effectively. The other method is to use water to wet the rock, thereby forcing the rock to release the oil and gas attached to it. Rock usually absorbs and retains oil. This nanotechnology recovery method reverses the retention by becoming a surfactant-acting like soap-but much more effectively and with a lot less material, therefore making the rock tend to absorb water and release oil.

Advantages of using nanoparticles in oil recovery:

• Use as a tracer
• Unaffected by chemical reactions
• Less material injected into the well
• More data
• Smaller environmental footprint
• Can be used in place of water injection  

Smart cement

An emerging technology that would greatly benefit the oil and gas industry is smart cement, which is cement filled with nanoscale particles of calcium, silica, and iron. Other modifiers include polymers, coupling agents, water-reducing agents, particle fillers, and admixtures. These additives turn the slurry into piezomaterials that are able to "talk" to engineers, telling them about the integrity of the well, pressure, volume, and potential problems. Dr. Krishnamoorti and Dr. Vipulanandan, also a professor at UH, have been conducting research on the sensing aspects of this technology. The following is taken from their report, "Smart Cementing Materials and Drilling Muds for Real Time Monitoring of Deepwater Wellbore Enhancement."

Model study

The model was built using a Plexiglas and metal pipe as shown in Figure 1 to simulate the formation and casing. The casing was instrumented with electrical wires to monitor the resistance change. The distance between two sensors was 4 in. and there were six levels of sensors. Different combinations of the sensors were connected to a 300 kHz LCR device (measures the inductance [L], capacitance [C], and resistance [R]) to measure resistance between those sensors.

Monitoring the cement slurry level

The smart cement slurry rise was monitored, and the vertical resistance changes are shown in Figure 2. This observation showed that the rise of cement slurry during the installation can be monitored based on the resistance value while identifying the level of the slurry.

20,000 psi subsea

The real challenge for offshore technologies is that U.S. leadership is starting to falter because of the conservative way it has monitored the safety aspect of new technology, economic constraints, and the fact that the rest of the world is advancing quickly.

The main challenge is the environment: pressure, depth, and temperature. Over the next 10-15 years, wells will be located where there is a pressure of 20,000 psi and the temperature of the well will be about 350 F or higher. "We are looking at this as an unencountered challenge," said Dr. Krishnamoorti. "However, the advantage to this is the fact the reservoirs and the oil reserves are enormous. We want to be able to enable the technologies that are going to revolutionize oil and gas over the next 20-30 years. To do this, the University of Houston is looking at integrating what is going on in the digital world with the physical world as well as collaborating closely with the industry to not only enable best practices to be gathered, but also to educate the next generation of the workforce."

– Dr. Ramanan Krishnamoorti is chief energy officer for the University of Houston. He is also professor of chemical and biomolecular engineering, professor of petroleum engineering, and professor of chemistry at the university. Edited by Eric R. Eissler, editor-in-chief, Oil & Gas Engineering, eeissler@cfemedia.com 

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