Nahai Cao
PETE Undergraduate Student 
Summer Intern (May-Sept. 2014) 

Research subject: Wettability Alteration of Heavy-Oil/Bitumen Containing Carbonates Using Solvents, high pH Solutions and Nano/Ionic Liquids

Winner of Dean's Research Award-2014

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Nahai's research focuses on contact angle measurements as a means to evaluate the wettability alteration on mineral plates and porous rock samples.  Imidazolium ionic liquids were tested at different concentrations. To study the effect of pH on wettability, sodium chloride and sodium borate were used at different concentrations. The composition of divalent ions was varied due to their possible use with low/high salinity water as wettability alteration agent. Unmodified and surface modified silica, zirconium, and alumina nanoparticles were also tested.  

Contact angle measurements were performed initially on mica, marble, and calcite plates. Experiments were repeated on polished surfaces of Berea sandstone, Indiana limestone, and -cleaned- Grosmont carbonate cores. Oils (pure and solvent mixed crude oils) with different viscosities and densities were used to test the effect of oil type on the process.  The images were obtained by an SLR camera at different temperatures ranging from 25 to 80C. By testing with different concentrations, the optimum chemicals were found for different mineral plates/porous rock systems.  Then, the results were cross-checked with the imbibition tests performed on the same samples to validate the contact angle measurement observations. 

Thermal stability tests were also performed in case of their use during or after a thermal method. For the thermal stability tests, contact angle experiments were conducted in a high pressure and high temperature (up to 200C) cell.  It was shown that certain ionic liquids and nanofluids are stable at high temperatures and can be efficiently used at low concentrations. 

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Publications:

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1. Cao, N., Mohammed, M. and Babadagli, T.: “Wettability Alteration of Heavy-Oil/Bitumen Containing Carbonates Using Solvents, high pH Solutions and Nano/Ionic Liquids,” accepted for publication in SPE Res. Eval. and Eng., 2016.

2. Cao, N., Mohammed, M. and Babadagli, T.: “Wettability Alteration of Heavy-Oil/Bitumen Containing Carbonates Using Solvents, high pH Solutions and Nano/Ionic Liquids,” OTC 26028, 2015 Offshore Technology Conf. (OTC), Rio de Janeiro, Brasil, 27-29 Oct.

3. Babadagli, T. and Cao, N.: “An Experimental Study to Determine Optimal Injection Strategies for Water-Alternating-Solvent Process in Green and Brown Fields,” SPE 187020, 2017 SPE Asia Pacific Oil and Gas Conf. and Exh. (APOGCE), Bali, Indonesia, 17-19 Oct.

4. Babadagli, T. and Cao, N.: “Optimal Design of Solvent Injection as a Cost Effective and Low Carbon Emission Application for Light and Heavy-Oil Recovery Considering Different Oil and Rock Characteristics,” 2017 SPE Asia Pacific Prod. and Cost Opt. Symp., Kuala Lumpur, Malaysia, 7-8 Nov.

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