Underground transformation and upgrading for improved oil recovery

Abstract

Petroleum refining has entered a significant transition period as the industry moves into the 21st century and the demands for petroleum and petroleum products continue to show a sharp growth in recent years. Refinery operations have evolved to include a range of next-generation processes as the demand for transportation fuels and fuel oil has shown steady growth. The research described in this thesis has been focused on an investigation of hydrothermal processing of hydrocarbons, mainly heavy oils. Experiments were carried out at temperatures from 300 to 380 °C and at a pressure of 220 ± 10 bar in both batch and flow systems separately by using 1/4-inch stainless steel tubing. The experiments were performed by using different reaction systems: toluene/H2O, toluene/H2O2, toluene/H2O/air, and toluene/H2O2/air. A comparative study of these reaction systems spiked with sulphur and metals (nickel, vanadium) were also conducted at the same conditions. Toluene conversion was investigated in a batch reactor at supercritical conditions in the presence of water. The conversion of toluene increases with temperature and steam/carbon (S/C) molar ratio (i.e. H2O to toluene ratio), conditions that provide favourable operating conditions for toluene conversion order to get high content products (gases and liquids). The toluene conversion yields multiple desirable lighter (liquid) hydrocarbons. The major liquid products include benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol and benzoic acid. Progressively larger quantities of these products are possible at higher temperatures and at higher H2O/toluene ratios. The efficiency of toluene conversion into products reaches almost 91% at 380 °C at a H2O/toluene ratio of 3 to 1. The yields improve monotonically as longer reaction times are allowed. Furthermore, when adding H2O2, the yield of the major liquid products benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol, benzoic acid increases with temperature and at higher H2O2/toluene ratios. The efficiency of toluene conversion into products reaches almost 40% at 380 °C at H2O2/toluene ratio equals to 3:1 with 5% H2O2 in 5 min of residence time. The yields improve at longer residence times. In the gas phase, H2 increases with an increasing H2O2 concentration while again, the yield of CH4 is small. The CO content increases up to 40% when between 6% and 8% H2O2 is used at temperatures around 380 °C whereas the CO2 content decreases. The conversion efficiency of toluene converted into liquid and gas products increases with temperature. This increase is accentuated with an increase in the H2O2/toluene ratio. Toluene conversion is slightly higher in the water/toluene mixture (90%) than the H2O2/toluene mixture (just below 90%). This is important, since along with the increased cost associated with the need for H2O2 and hence the increased overall cost of operation, it suggests that the water/toluene system is the more desirable one to consider further. Experimental results also revealed that a maximum of about 90% of the Ni-TPP was converted to intermediate and final Ni-based products at a temperature of 380 °C and after a reaction time of 90 min. Under the same conditions, around 67% of the Ni was removed by the action of supercritical water, proving that supercritical water is capable of removing Ni from Ni-TPP. The same batch reactor system was also used to study vanadium removal. V-TTP (a vanadium-containing compound which was added to the toluene) also reacted with SCW suggestions a pathway for vanadium removal. The effects of reaction time and temperature were investigated, showing that approximately 91% of V-TPP was converted to intermediate and final products at a temperature of 380 °C and reaction time of 100 min. Under the same conditions, approximately 82% of the vanadium was removed. This process was deemed successful since it did not use a catalyst. Finally, the removal of unwanted/undesirable sulphur from the oil was also considered. A gradual increase in the % DBT conversion was found at higher temperatures. The maximum DBT conversion was achieved at the highest investigated temperature, i.e. 380 °C. A maximum DBT conversion of ~ 97% was recorded after 30 min of reaction time. Importantly, and contrary to the findings concerning the conversion of toluene, the introduction of H2O2 lead to a considerable improvement in the metal removal potential.