(559r) New Nanocatalyst Preparation for Improving Product Quality of in-Situ Upgrading Technology (ISUT)

Authors: 
Ahmadi Khoshooei, M., University of Calgary
Scott, C., University of Calgary
Carbognani, L., University of Calgary
Pereira-Almao, P., University of Calgary
Exploitation of unconventional energy resources, heavy and extra-heavy oils in particular, is of the essence in order to cope with the ever-growing global energy demand. Yet, complex challenges exist on the pathway of converting these raw hydrocarbons into the form of usable energy and fuels. Due to the low H/C ratio, high concentrations of heteroatoms such as nitrogen, sulphur and metals, the quality of heavy oils is poor and therefore further upgrading processes are required. As a result, both the environmental footprint and production cost of these resources increase appreciably, as compared to the conventional oils. In-reservoir upgrading processes could potentially address these challenges by permanently enhancing the quality of produced oil, which in return redeems the necessity for further processing of the product on the surface. A nanocatalytic in-situ upgrading technology (ISUT) has been recently proposed and showed success in producing premium quality oil, which needs no further processing once reaches the surface [Pereira-Almao et al., Patents CA2864788C and CA2810022C]. In the ISUT process, the heaviest fraction of oil, vacuum residue (VR), is separated aboveground and then is co-injected with hydrogen and nanocatalysts into the reservoir. The hydroprocessing reactions taking place downhole in the reservoir permanently upgrade the oil, which is then recovered on the surface. Then again, the VR is separated and injected back to keep the production cycle continuous. In this process, nickel and molybdenum are used as catalysts and are prepared and dispersed online in the VR. The salts of these transition metals are dissolved in water in order to produce transient microemulsions in the presence of VR, employing an intensive mixing method. Then at high enough temperature, 350 °C, and in the presence of a sulfiding agent, the decomposition of the salts leads to production of catalytically active nanoparticles of metals, i.e. metal sulfides.

A new nanocatalyst preparation pathway using ultrasound is investigated in this study. An ultrasonic probe is employed for preparing the microemulsions of the molybdenum solution with VR. The results of catalyst preparation showed that the synthesized NiMo nanoparticles are half the size of the particles prepared conventionally using a high shear mixer. A continuous setup which potentially emulates a patented process (US20180086990A1) for catalyst preparation for the ISUT application to an actual sandstone reservoir was constructed to evaluate the two different batches of nanoparticle suspensions in VR, one using high shear mixers, and one using ultrasonic probe. A reactor was packed with silica-based sand with measured permeability of 15-16 Darcy, which effectively resembles Canadian oilsand reservoirs. In the continuous setup, a comparative study was done to assess the reactivity of the two prepared batches. The VR along with hydrogen and catalyst were injected in the reactor and the residence time was 48 hr for all experiments.

Significant improvement in the product quality was observed once the ultrasound-assisted nanoparticles were used. Using the new preparation approach, lower density and viscosity, lower microcarbon content and greater demetallization and desulphurization extent were achieved for the products. Therefore, it was concluded that employing the ultrasonic pathway for catalyst preparation in ISUT processing improves the overall upgrading efficiency of the process. As well, smaller size nanoparticles ensure that the permeability of the sandstone remains intact since there is less chance of pore impairment in the case of smaller particles. Also, after the experiment, the sandpack was carefully cut in pieces and the sand in each part was characterized in terms of the catalyst concentration and the nature of the remaining hydrocarbon. It was observed that almost all of the catalytic precursors were deposited in the first one-fourth of the reactor. In addition, this first section showed to have heavier hydrocarbons remaining in the reactor.