1 Upgrading Unconventional Oil Resources with the EST Process Alberto Delbianco and Salvatore Meli, Eni E&P Division Nicoletta Panariti and Giacomo Rispoli, Eni R&M Division Abstract We strongly believe that unconventional oils will play a much larger role in the growth of supply than is currently recognized. As a matter of fact, whereas the earth’s conventional proven world oil reserves are 1.3 trillion barrels (bbl), extra-heavy plus bitumen resources amount to about 4 trillion bbl. The unconventional oils are characterized by an API gravity lower than 10, high viscosity and an unusual high concentration of poisons such as sulphur, nitrogen, metals, and asphaltenes. For this reason, a key role for the full exploitation of these hydrocarbon resources is played by the downstream processes that are required to upgrade and convert them into valuable products. In this scenario, Eni has developed a novel hydrocracking process (EST: Eni Slurry Technology) which is particularly well-suited for the conversion and upgrading of a variety of “black oil materials”, from conventional vacuum residues up to extra-heavy oils and bitumen. EST employs nano-sized hydrogenation catalysts and an original process scheme that allow complete feedstock conversion to an upgraded synthetic crude oil (SCO) with an API gravity gain greater than 20 and avoid the production of residual by-products, such as pet-coke or heavy fuel oil. Moreover, this leading-edge technology assures both product slate and feedstock flexibility. A Commercial Demonstration Unit (CDP) of 1200 bbl/d capacity is successfully operating in the Eni’s Taranto refinery since November 2005. 2 1. Introduction Bitumen and extra heavy oils constitute the largest component of non conventional oil resources that we can expect to add to the so called conventional ones in the coming decades. The estimated oil in place for these fossil fuels amount to around 4 trillion barrels (bbl). Considering also that the technically recoverable fraction is in the range 15-20%, it is evident that we are talking about enormous quantities if one considers that the whole of the Middle East has resources of about 2,000 billion bbl, of which 743 are considered to be recoverable /1-2/. The greater part of these reserves is concentrated in Canada, in the province of Alberta (tar sands), and in Venezuela in the so called Orinoco Belt. A third country which is rich in non-conventional oil is Russia, even though in this case the deposits are scattered so that the recoverable portions are not quantitatively as large as in the other two countries (Figure 1). Figure 1 - Heavy and non-conventional Oil Recoverable Reserves (billion bbl). Although based on today’s technology, only 10 to 15% of these resources can be considered “recoverable”, this is a huge amount, close to 600 billion bbl. Because the current world oil consumption is about 30 billion bbl per year, this means a potential supply of about 20 years. These numbers highlight the importance of the unconventional oils in the future energy scenario and for these reasons the International Energy Agency (IEA) foresees a growing role for both heavy oil and bitumen in the medium-long term /3/. Nevertheless, we should remember that heavy hydrocarbons are making a robust contribution to the world’s oil supply with a production that is today close to 2 billion bbl per year. This is because new and more efficient technologies have brought down the costs of recovery of Canada’s and Venezuela’s heavy hydrocarbons to within striking range of conventional oil production, so that in 3 the last two decades the synthetic crude oil production cost has been reduced by more than 50% /4- 5/. Looking downstream, there are a variety of processes designed to upgrade these feedstock even if their peculiar physical and chemical properties make this step costly and environmentally unfriendly because of the high energy required and the huge amounts of by-products usually generated. As a matter of fact, extra-heavy oils and natural bitumen represent crude oils which have been severely degraded by microbial action as evidenced by their paucity of low molecular weight saturated hydrocarbons. As a results, there are more heavy hydrocarbons in these materials than in the conventional crude and sometimes, asphaltene and resins may represent the great part of the oil. Generally speaking, heavy oils and bitumens are characterized by having an API gravity lower than 10 as well as a high viscosity (thousands cPoise). The yield and the quality of these oils are usually significantly different if compared to a traditional light crude such as the Arabian Light, as shown in Table 1. Arabian Cold Athabasca Zuata Boscan Maya Light Lake Bitumen Origin S.A. Venezuela Venezuela Mexico Canada Canada API Gravity 33.6 8.5 10.5 21.5 10.2 8.1 Dist. Distribution (wt.%.) Naphtha 20.6 n.a. 4.0 12.9 1.5 n.a. Atm. Gasoil 36.0 14.1 11.6 21.7 14.9 16.1 Vacuum Gasoil 23.2 31.0 20.2 22.2 38.8 31.7 Vacuum Residue (VR) 20.2 54.9 64.2 42.2 44.8 52.2 Table 1 – Comparison of the characteristics of Arabian Light crude vs. typical extra-heavy oils and bitumen. In some cases the total amount of vacuum residue (VR) can be higher than 50%. Moreover, these materials are generally rich in sulphur, nitrogen, heavy metals and asphaltenes. Poisons are concentrated in the distillation residues so that the sulphur and nitrogen level is generally higher than 4 wt.% and 0.5 wt.% respectively, the metal concentration (Ni + V) is in the range of several hundreds ppm while the asphaltene content is normally higher than 20-25% if referred to the VR (Table 2). Because of the huge concentration of high density naphthenes, aromatics and polar compounds, the H/C ratio is very low if compared to the transportation fuels in which they must be converted, i.e. gasoline and diesel oil. 4 Arabian Cold Athabasca Zuata Boscan Maya Light Lake Bitumen TBP cut 530°C+ 500°C+ 350°C+ 500°C+ 340°C+ 300°C+ API Gravity 8.3 2.5 7.2 1.5 7.2 7.8 H/C 1.45 1.41 1.47 1.33 1.40 1.43 Sulphur (wt.%) 4.0 4.2 6.0 5.2 4.9 4.6 Nitrogen (wt.%) 0.25 0.97 0.96 0.81 0.70 0.48 Nickel (ppm) 30 154 119 132 107 70 Vanadium (ppm) 110 697 1473 866 210 186 Asphaltene (wt.%) 5.3 19.7 18.2 30.3 12.0 12.4 CCR (wt.%) 18.0 22.1 18.3 29.3 20.8 13.6 Table 2 – Chemical composition of selected residues from extra-heavy oils and bitumen. As a consequence, the main scope of a conversion/upgrading technologies is to: convert the atmospheric & vacuum residues into distillates minimizing the by-products remove poisons such as heteroatoms (i.e. sulphur, nitrogen and oxygen), asphaltenes and metals increase the hydrogen content of the upgraded materials /6/. The increase of the H/C ratio can be made either rejecting carbon or adding hydrogen. The C- rejection processes (such as visbreaking and coking) show very high feedstock flexibility but generate low quality distillates and huge amount of by-products, such as fuel oil and pet-coke, whose market demand is shrinking /7/. On the contrary, the hydrocracking technologies assure good product upgrading but the well known fixed bed or ebullating bed technologies present severe limitations in terms of feedstock flexibility. As a matter of fact, the supported catalysts can be plugged by metals and coke deposits on the porous supports, so that when processing highly polluted feedstock, the state-of-the-art hydroconversion processes must operate at relatively low severity, therefore producing huge amounts of heavy fuel oil /8/. This drawback is less significant in the case of slurry phase hydrocracking processes because of the use of non-supported micro-sized particles of highly active hydrogenation catalysts. The slurry hydrocrackers employ finely dispersed hydrogenation catalysts, such as iron-based additives or micro-sized transition metal sulphides that are usually generated in-situ during reaction, via thermal decomposition of oil-soluble precursors. The use of the dispersed catalysts is very effective in 5 preventing the coke formation while assuring a good control of the sediments precipitation and fouling, even at relatively high conversions /9/. In spite of these advantages, the slurry phase hydrocracking processes have not yet made the necessary hurdle to large-scale commercial demonstration because of the difficulties in matching high conversion with excellent products quality as well as due to the technological problems connected with the catalyst handling. In this scenario, Eni has developed a new process: EST (Eni Slurry Technology), which overcomes these limits and allows almost total feedstock conversion with excellent contaminants removal. 2. Eni Slurry Technology Development Phase The Eni’s R&D activity, aimed at developing a new slurry process to convert the heavy feedstock, was started in the early nineties. The first phase of this work was addressed to investigate the fundamental chemistry aspects of the reactions. Furthermore, catalyst screening evaluation was performed to identify the most suitable one. The results which have been obtained were extremely useful to deepen the knowledge about the problem and to develop an innovative process scheme which allows to overcome the constraints which have prevented the industrial application of the slurry processes /10-11/. The key feature of this new technology may be identified in the arrangement adopted for the recovery and recycling of the catalyst: the solution is extremely simple and relatively cheap (a simplified flow scheme is shown in Figure 2).