Toe-to-Heel Air Injection Research Articles

A detailed approach to up-scaling of the Toe-to-Heel Air Injection (THAI) In-Situ Combustion enhanced heavy oil recovery process

Toe-to-Heel Air Injection (THAI) is a variant of conventional In-Situ Combustion (ISC) that uses a horizontal production well to recover mobilised partially upgraded heavy oil/bitumen/tar sand. For the promise of THAI to be fully realised, realistic and validated field scale simulations are required to design process operations. Firstly, a brief review of the available laboratory to field up-scaling techniques was presented. Then sequential volume up-scaling was used to obtain larger length scales predictions. It was found that, as with conventional ISC, the kinetics parameters had to be altered to obtain a realistic representation of the physico-chemical processes occurring at larger length scales. Consequently, a new approach, which is grounded in theory, to up-scaling laboratory-scale simulations, already validated against experiment, has been proposed and tested. It is shown for the first time that for the fraction of fuel formed and consumed at laboratory scale to be the same as that at field scale, the Damkhöler number must be the same. From this relationship, it has been shown mathematically that the frequency factor of the reactions must be down-scaled from laboratory values to field values in order for the fuel deposition and consumption at the laboratory scale to be the same as at field scale. This is clearly another key finding in this study that has not been shown before. Therefore, an initial estimate must be made and iterative runs used to determine the value of the down-scaling factor. The new model led to improvements in the key prediction of the distribution of fuel (coke) deposition over previous field-scale works.

Inductive Heating Assisted-Catalytic Dehydrogenation of Tetralin as a Hydrogen Source for Downhole Catalytic Upgrading of Heavy Oil

The Toe-to-Heel Air Injection (THAI) combined with a catalytic add-on (CAPRI, CATalytic upgrading PRocess In-situ) have been a subject of investigation since 2002. The major challenges have been catalyst deactivation due to coke deposition and low temperatures (~ 300 °C) of the mobilised hot oil flowing over the catalyst packing around the horizontal well. Tetralin has been used to suppress coke formation and also improve upgraded oil quality due to its hydrogen-donor capability. Herein, inductive heating (IH) incorporated to the horizontal production well is investigated as one means to resolve the temperature shortfall. The effect of reaction temperature on tetralin dehydrogenation and hydrogen evolution over NiMo/Al2O3 catalyst at 250–350 °C, catalyst-to-steel ball ratio (70% v/v), 18 bar and 0.75 h−1 was investigated. As temperature increased from 250 to 350 °C, tetralin conversion increased from 40 to 88% while liberated hydrogen increased from 0.36 to 0.88 mol based on 0.61 mol of tetralin used. The evolved hydrogen in situ hydrogenated unreacted tetralin to trans and cis-decalins with the selectivity of cis-decalin slightly more at 250 °C while at 300–350 °C trans-decalin showed superior selectivity. With IH the catalyst bed temperature was closer to the desired temperature (300 °C) with a mean of 299.2 °C while conventional heating is 294.3 °C. This thermal advantage and the nonthermal effect from electromagnetic field under IH improved catalytic activity and reaction rate, though coke formation increased.

Detailed analysis of Toe-to-Heel Air Injection for heavy oil production

The Toe-To-Heel Air Injection (THAI) operation at Kerrobert, Saskatchewan proved that commercial oil rate is possible together with production of partially upgraded heavy oil. Despite physical model experimentation and simulation investigations of THAI, no detailed analysis has been conducted on a THAI field operation to resolve recovery mechanisms and the strengths and limitations of the process. Here, we present, for the first time, a detailed evaluation of the Kerrobert THAI field operation to find causal relationships between injectants and production rates, gas composition, and temperature rise within the reservoir and which downhole reactions are key in the process i.e. low temperature oxidation, high temperature oxidation, thermal cracking/thermolysis, coke gasification and aquathermolysis. The results demonstrate that there is a competition between oxygen injection for heat generation via oxidation reactions versus air injection leading to cooling of the system which limits the peak oil rate. General comparisons are made to a neighboring Steam-Assisted Gravity Drainage (SAGD) operation in the same formation. A comparison of THAI and SAGD in the formation indicates that although THAI yields significantly lower normalized oil rates than SAGD, it is more energy efficient than SAGD.

Enhanced Recovery of Heavy Oil Using A Catalytic Process

Oil is a major source of energy around the world. With the decline of light conventional oil, more attention is being paid to heavy oil and bitumen, as a good alternative to light oil for energy supplies. Heavy crude oils have a tendency to have a higher concentration of metals and several other elements such as sulfur and nitrogen, and extraction of these heavy oils requires more effort and cost. Toe-to-Heel Air Injection (THAI) is a novel process of enhanced heavy oil and bitumen recovery and upgrading. In this technique, horizontal well concepts are integrated with the reactions of high temperature oxidation to achieve a potentially high recovery ratio. Since the process works through a short distance displacement technique, the produced oil flows easily toward the horizontal producer well. This direct mobilized oil production and short distance are the major features of this method which lead to robust operational stability and high oil recovery. This technique gives the possibility of a higher recovery percentage and lowers environmental effects compared to other technologies like steam based techniques. A novel well design consisting of two horizontal injectors and two horizontal producers was used in different well configurations, to investigate the potential for improved efficiency of the THAI process on the heavy oil recovery. A 3D dimensional model, employing the CMG-STARS simulator, was applied for this process. Two horizontal injectors and producers were utilised in this project, instead of the conventional horizontal injector and producer used in the Greaves model (the base case model), to investigate the effect of the extra injector and producer on the performance of the THAI process. It was found that the locations of the well injections and the well productions significantly affected the oil production. It was found that the amount of the produced oil rose up to about double of the amount of the oil produced by the original model. For the study of the effectiveness of the catalysts in the oil upgrading process, the CAPRI technique has been simulated to investigate the effect of several parameters, such as catalyst packing porosity, the thickness of the catalyst layer and hydrogen to air ratio, on the performance of the CAPRI process. The TC3 model used by Rabiu Ado [1], which was the same model utilised in the experimental study of Greaves et al. [2], was also employed in this study. The silica-alumina catalyst characterised by Hasan [3] was placed around the horizontal producer in this simulation.

Numerical simulation of the impact of geological heterogeneity on performance and safety of THAI heavy oil production process

The Toe-to-Heel Air Injection (THAI) in-situ combustion process is an efficient way to extract heavy oil and bitumen. However, such reservoirs are often geologically heterogeneous. This work studied the impact of a range of different geological heterogeneities, often found in bitumen deposits, on the performance and safety of THAI. These heterogeneities included random heterogeneity, layered reservoirs, shaly reservoirs, and semi-permeable cap-rocks. A further aim was to also develop potential remedial measures, such as selective well placement. It was found that the degree of symmetry assumed for the reservoir model had a substantial impact on the predicted level of oil production. This is of particular relevance to otherwise apparently symmetrical well placement designs such as staggered line drive. While the presence of impermeable zones resulted in the decrease in the overall oxygen utilisation for shaly reservoirs, compared to simply low permeability reservoirs, there was no evidence of oxygen breakthrough due to preferential channelling into the production well. In layered reservoirs, the development of a rich oil bank during THAI operation depended upon the distribution of permeability around the horizontal producer (HP), and did not occur when there was high permeability just above the HP. It has been shown that the proper representation of the cap-rock in reservoir models for the simulation of THAI is essential in order to accurately mimic the full pattern of heat distribution into the oil zone of the reservoir, and, thence, fuel lay-down. While THAI can operate stably with a permeable cap-rock, vertical permeabilities above ∼1–3 mD led to significant loss of combustion gases from the reservoir.

Analysis of a feasible field THAI pattern by the derivation of scaling criteria and combustion experiments

Abstarct Toe-to-heel air injection (THAI) process is considered as a potential enhanced oil recovery (EOR) method for heavy oil production. For physical simulation of THAI process in laboratory conditions, the simplified scaling criteria of THAI process were derived and a novel three-dimensional cylindrical apparatus was used to construct the new THAI pattern in this study. Equation analysis and dimensional analysis (Buckingham π-theorem) were applied to deduce the whole dimensionless groups, and sensitivity of the coefficients described with their distortion coefficients were used to obtain the influential weights and the simplified scaling criteria. STARS module in Computer Modeling Group (CMG) was used to verify the feasibility of the THAI pattern by two models, which represent the reservoir prototype and the 3D apparatus respectively. With an effective simulation of experimental results, a reasonable data set was obtained, and then those values were upscaled for simulation of field THAI process by the simplified scaling criteria. The experiment results showed that the horizontal well was well protected by a slant distribution of coke zone and the other parameters about oil production (such as the high temperature swept volume, oil production rate and recovery) were still satisfactory. The similarity of variation process of temperature field, oil saturation distribution and production performance between the laboratory results and THAI simulation in reservoir prototype showed the validity of the scaling criteria and indicated that a feasible field THAI process with a large combustion chamber upon horizontal well can be predicted to achieve.

In Situ Catalytic Upgrading of Heavy Crude with CAPRI: Influence of Hydrogen on Catalyst Pore Plugging and Deactivation due to Coke

Heavy crude oil is known to have low hydrogen-to-carbon ratios compared to light oil. This is due to the significant content of carbon-rich species such as resins and asphaltenes; hence their upgrading is commonly through carbon-rejection. However, carbon-rejection promotes rapid fouling of catalyst and pore plugging, yielding low upgraded oil and consequently low fuel distillate fractions when distilled. The roles of hydrogen-addition on in situ catalytic upgrading were investigated at pre-established conditions (425 °C, LHSV 11.8 h−1, and 20–40 bars) using a simulated fixed-bed reactor that mimics the annular sheath of catalyst (CAPRI) surrounding the horizontal producer well of the Toe-to-Heel Air Injection (THAI) process. It was found that with H-addition, the upgraded oil American Petroleum Institute (API) gravity increased to about 5° compared to 3° obtained with N2 above 13° (THAI feed oil). The fuel distillate fractions increased to 62% (N2, 20 bar), 65% (H2, 20 bar), and 71.8% (H2, 30 bar) relative to 40.6% (THAI feed oil); while the coke contents of the catalyst after experiments were 35.3 wt % (N2), and 27.2 wt % (H2). It was also found that catalyst pore plugging and deactivation due to coke was significantly lower under hydrogen than with nitrogen; hence the catalyst is less susceptible to coke fouling when the upgrading reaction is carried out under hydrogen. The coke fouling further decreases with increasing hydrogen pressure while the API gravity of the upgraded oil marginally increases by 0.3° for every 10 bar increase in pressure from 20 to 40 bar.

Effect of pre-ignition heating cycle method, air injection flux, and reservoir viscosity on the THAI heavy oil recovery process

Heavy oil and bitumen reserves can potentially bridge the gap in world energy demand during the transition between conventional hydrocarbon fuels and sustainable energy sources, while the latter are developed. However, the development of efficient extraction methods with low emissions is necessary. The in-situ combustion process, toe-to-heel air injection (THAI), is such a method, but some issues remain in improving its performance. In this paper, the performance of the THAI process has been investigated at the laboratory scale using a validated simulation model. We have studied the effect of pre-ignition heating cycle (PIHC) method, reservoir oil viscosity, and air injection flux, on the stability and operability of the THAI process. It was found that the use of steam, instead of electrical heaters, for the PIHC resulted in an increase in oil recovery. However, use of steam also caused a reduction in oxygen utilisation. The use of a horizontal injector (HI) well, in combination with the steaming during the PIHC, causes some of the oxygen to bypass the combustion front during the early stage of air injection. It is concluded that steaming using a staggered line drive, or 2VIHP well arrangement, is recommended to be used at the field scale. It was also found that THAI operates more stably for higher viscosity oil, albeit at higher operating cost, due to increased cumulative air-oil ratio (CAOR), compared to for a low oil viscosity reservoir. In contrast to previous suppositions, it has been found that oil recovery increases non-linearly with an increase in air flux, which needs to be taken into account on scale-up.

Optimization of well spacing to achieve a stable combustion during the THAI process

Toe-to-Heel Air Injection (THAI) is a great potential in improving energy efficiency for heavy oil/bitumen recovery. A 3D cylindrical combustion model with large size is used to carry out several experiments using Xinjiang (China) crude oil. The evolution of the fire chamber, temperature variation rate, and mass of burned carbon were analyzed using temperature measurements and flue gas composition analysis. Coke zone was quantified in the variation of zone thickness and distribution characteristics. The results reveal that there is a prevailing stable propagation of the combustion front during the first one third of the process for varying injector to producer spacing. Oxygen breakthrough is more susceptible for smaller separations and the combustion zone is reduced in length. Larger combustion fronts with greater relative propagation in the horizontal direction occurs when the well spacing is larger. The distribution of coke is significantly influenced by the injector/producer spacing. For a THAI pattern with greater injector/producer spacing, a smaller inclination angle of the coke zone occurs and the likelihood of oxygen breakthrough to the horizontal production well is lessened. Hence, the injector to producer spacing needs to be considered in designing a safe THAI process for potentially larger efficiency and optimum economics.

Feasibility study on application of the recent enhanced heavy oil recovery methods (VAPEX, SAGD, CAGD and THAI) in an Iranian heavy oil reservoir

ABSTRACTEnhanced oil recovery (EOR) methods assisted by gravity drainage mechanism and application of sophisticated horizontal wells bring new hope for heavy oil extraction. Variety of thermal and non-thermal EOR techniques inject an external source of energy and materials such as steam, solvent vapor, or gas through a horizontal well at the top of the reservoir to reduce in-situ heavy oil viscosity. So, the diluted oil becomes mobile and flows downwards by gravity drainage to a horizontal producer located at the bottom of the reservoir.In this paper, a sector model of an Iranian fractured carbonate heavy oil reservoir was provided to simulate and evaluate capability of some EOR techniques such as Vapor Extraction (VAPEX), Steam Assisted Gravity Drainage (SAGD), Combustion Assisted Gravity Drainage (CAGD), and Toe to Heel Air Injection (THAI) at its reservoir conditions and fluid properties. The simulation results demonstrated that wet CAGD in comparison with other nominated methods could improve heavy oil recovery factor to around 19% much more than each of SAGD, THAI, and VAPEX techniques. It could also reduce the total energy to produced oil ratio index up to 82% with respect to SAGD process in a year.Although lower oil recovery has been gained by VAPEX process, but using a proper vaporized solvent could produce a kind of de-asphalted and upgraded oil with increased API gravity up to 29°API with no considerable solvent loss.

In situ catalytic upgrading of heavy oil using a pelletized Ni-Mo/Al2O3 catalyst in the THAI process

Heavy oil and bitumen are difficult crudes to extract and upgrade, with additional transport and refining costs, because of their high viscosity, low API gravity, high asphaltenes, metals (V, Ni), and heteroatoms (N, S). Combining Toe-to-Heel Air Injection (THAI) with its catalytic add-on (CAPRI), a pelletized catalyst is incorporated along the outside of the horizontal producer well for in situ catalytic upgrading. This downhole upgrading process is one means to produce and partially upgrade heavy oil and bitumen with a reduced environmental footprint. In this study, the effectiveness of pelletized hydrodesulfurisation (HDS) Ni-Mo/Al2O3 catalyst for downhole catalytic upgrading was investigated at 350–425 °C, 20 bar, and 9 h−1 space velocity. The additional upgrading due to the presence of the catalyst was evaluated in terms of API gravity, viscosity, boiling point distribution, and sulfur and metals removals, before and after the experiment. The results indicate that the viscosity of the upgraded oil reduced by 1.7, 3 and 5 times less than the feed oil (0.49 Pa s) depending on the reaction temperature in the range 350–425 °C. The average increase in API gravity was approximately 2 to 5° while the gasoline yield showed an improvement of 2.5–13 wt.% above that of the original oil. There was also a modest reduction in the sulfur and metals (Ni + V) content of 2–8% and 1.3–9.2% (Ni + V), respectively. However, a possible limiting factor of the process was that rapid catalyst deactivation occurred due to coking.

Dynamic Simulation of the Toe-to-Heel Air Injection Heavy Oil Recovery Process

Toe-to-heel air injection (THAI) is a variant of conventional in situ combustion (ISC) that uses a horizontal production well to recover mobilized partially upgraded heavy oil. It has a number of advantages over other heavy oil recovery techniques, such as high recovery potential. However, existing models are unable to predict the effect of the most important operational parameters, such as fuel availability and produced oxygen concentration, which will give rise to unsafe designs. Therefore, we have developed a new model that accurately predicts dynamic conditions in the reservoir and is also easily scalable to investigate different field scenarios. The model used a three-component direct conversion cracking kinetics scheme, which does not depend upon the stoichiometry of the products and, thus, reduces the extent of uncertainty in the simulation results as the number of unknowns is reduced. The oil production rate and cumulative oil produced were well-predicted, with the latter deviating from the experi...

Comparison of the effects of dispersed noble metal (Pd) biomass supported catalysts with typical hydrogenation (Pd/C, Pd/Al2O3) and hydrotreatment catalysts (CoMo/Al2O3) for in-situ heavy oil upgrading with Toe-to-Heel Air Injection (THAI)

Catalyst deactivation due to coke and metals deposition as a result of cracking presents a challenge in heavy oil recovery and upgrading. This is particularly pronounced for in situ upgrading techniques, in which pelleted catalyst is packed around the perimeter of the horizontal producer well of the Toe-to-Heel Air Injection (THAI) process. The fixed bed of catalyst is virtually impossible to regenerate in place, promoting investigation of alternative contacting via the dispersion of nanoparticles. The catalysts studied were finely crushed micro-particulates with average size of 2.6μm and also a catalyst prepared upon a bacterial support. The latter has advantages in terms of ease of preparation of catalysts from recycled metal sources. Heavy oil of API gravity 13.8° and viscosity 1091mPas was used as feed and upgrading was performed in a batch reactor at 425°C, with a catalyst-to-oil ratio of 0.02 (g/g), and at an initial pressure of 20bar. The activity of the Pd/biomass catalyst was evaluated against a number of other catalysts: Pd/Al2O3, Pd/C, Al2O3 and Co–Mo/Al2O3. By using the Pd/biomass catalyst, the produced oil gravity increased by 7.8° API, and its viscosity was reduced to 7mPas. This effect corresponded to an increase in the amount of low-boiling distillate (IBP – 200°C) from 34.6vol.% (original feedstock) to 53–62vol.%, potentially reducing the amount of diluent needed for pipeline transport of bitumen. The coke yields were (wt.%): 13.65 (Al2O3), 9.55 (Pd/Al2O3), 6.85 (Pd/C) and 3.87 (Pd/biomass). The Pd/biomass catalyst showed significantly reduced coke yield compared to thermal cracking and upgrading using Pd/C and Pd/Al2O3 catalysts, which could greatly enhance catalyst survivability in the field.

Analysis of oil production by applying in situ combustion

ABSTRACTThe THAI (toe-to-heel air injection) process is a process of enhanced oil recovery, which consists of integrating the in situ combustion process with technological advances of horizontal wells drilling, and has not yet been applied in Brazil. Motivated by this context, the authors aimed to studying the application of the THAI process in a semisynthetic reservoir, with characteristics similar to those ones found in the Brazilian Northeast. It was analyzed the air injection rate, indicating that there is a limit to reach a good efficiency.

Effectiveness of Different Transition Metal Dispersed Catalysts for In Situ Heavy Oil Upgrading

Ultradispersed particles of a size less than 100 nm for in situ catalytic upgrading have been reported to outperform the augmented catalytic upgrading achieved by incorporating pelleted refinery catalyst to the horizontal production well of the toe-to-heel air injection (THAI) process. Hydroconversion of heavy oil was carried out in a stirred batch reactor at 425 °C, 50 bar (initial H2 pressure), 900 rpm, and 60 min reaction time using a range of unsupported transition metal (Mo, Ni, and Fe) catalysts. The effect of metal nanoparticles (NPs) was evaluated in terms of product distribution, physical properties, and product quality. The produced coke and recovered catalysts were also studied. The levels of API gravity and viscosity of the upgraded oils observed with the NPs was approximately 21° API and 108 cP compared with thermal cracking alone (24° API and 53.5 cP); this moderate upgrade with NPs is due to the lack of cracking functionality offered by supports such as zeolite, alumina, or silica. However,...

Optimization of Heavy Oil Upgrading Using Dispersed Nanoparticulate Iron Oxide as a Catalyst

It has previously been shown that in situ upgrading of heavy oil by toe-to-heel air injection (THAI) can be augmented by surrounding the horizontal production well with an annulus of pelleted catalyst. Despite the further upgrading achieved with this configuration, the accumulation of coke and metals deposits on the catalyst and pore sites, resulting from cracking of the heavy oil, have a detrimental effect on the catalyst activity, life span, and process. An alternative contacting pattern between the oil and nanoparticulate catalysts was investigated in this study, to mitigate the above-mentioned challenges. The Taguchi method was applied to optimize the effect of reaction factors and select the optimum values that maximize level of heavy oil upgrading while suppressing coke yield. The reaction factors evaluated were reaction temperature, H2 initial pressure, reaction time, iron metal loading and speed of mixing. An orthogonal array, analysis of mean of response, analysis of mean signal-to-noise ratio (S/N) and analysis of variance (ANOVA) were employed to analyze the effect of these reaction factors. Detailed optimization of the reaction conditions with iron oxide dispersed nanoparticles (≤50 nm) for in situ catalytic upgrading of heavy oil was carried out at the following ranges; temperature 355–425 °C, reaction time 20–80 min, agitation 200–900 rpm, initial hydrogen pressure 10–50 bar, and iron metal loading 0.03–0.4 wt %. It was found that the optimum combinations of reaction factors are temperature 425 °C, initial hydrogen pressure 50 bar, reaction time 60 min, agitation 400 rpm and iron–metal loading 0.1 wt %. The properties of upgraded oil at the optimum condition are API gravity 21.1°, viscosity 105.75 cP, sulfur reduced by 37.54%, metals (Ni+V) reduced by 68.9%, and naphtha plus middle distillate fractions (IBP: 343 °C) increased to 68 wt % relative to the feed oil (12.8° API, 1482 cP, sulfur content 3.09 wt %, metals (Ni+V) content 0.0132 wt %, and naphtha plus middle distillate fractions 28.86 wt %).

Effect of cyclohexane as hydrogen-donor in ultradispersed catalytic upgrading of heavy oil

The incorporation of catalysts to enhance downhole upgrading in the Toe-to-Heel Air Injection (THAI) process is limited by deactivation due to coking arising from the cracking of heavy oil. This study aims to reduce the catalyst deactivation problems that can occur with upgrading of heavy oils. Ultradispersed catalyst particles could potentially replace pelleted catalysts which may be difficult to regenerate once deactivated during the THAI operation. The dispersed particles could potentially be applied once through, down-hole for in situ upgrading of heavy oil. The catalyst studied was finely crushed pelleted Ni–Mo/Al2O3 catalyst (2.4μm). The product distribution of liquid, coke and gas may be influenced by the presence of a suitable hydrogen source which promotes hydroconversion reactions rather than simple cracking. In order to improve liquid yield whilst suppressing coke formation, the effect of cyclohexane as hydrogen-donor solvent was studied in a stirred batch reactor (100mL) at temperature 425°C, initial pressure 17.5bar, agitation 500rpm, and a short reaction time of 10min. The use of cyclohexane was evaluated against that of hydrogen gas. The reaction under hydrogen atmosphere significantly reduced coke yield by 41.3% compared with a nitrogen environment under the same conditions. Also, the coke decreased by 6.2–45.4% as the cyclohexane:oil ratio increased from 0.01 to 0.08 (g·g−1) relative to 4.67wt.% of coke observed without added cyclohexane in ultradispersed catalytic upgrading under nitrogen environment. As the cyclohexane:oil ratio increases, the produced oil API gravity and middle distillate fractions (200–343°C) increase whilst the viscosity decreases. An estimated 0.073 CH:oil ratio was found to suppress coke formation in a similar manner to upgrading under hydrogen atmosphere at the same conditions.

A comparative study of fixed-bed and dispersed catalytic upgrading of heavy crude oil using-CAPRI

CAtalytic upgrading PRocess In-situ (CAPRI) incorporated with Toe-to-Heel Air Injection (THAI) for heavy oil and bitumen recovery and upgrading was studied for fixed-bed and dispersed catalysts. The extent of upgrading was evaluated in terms of API gravity, viscosity reduction, impurity removal, and true boiling point (TBP) distribution. The test was carried out using Co-Mo/Al2O3 at temperature of 425°C, pressure 20bar, and residence time of 10min. The dispersed catalyst was tested in a batch reactor. However, the residence time, catalyst-to-oil (CTO) ratios as well as the Reynolds numbers of both contacting patterns were kept the same to ensure dynamic similitude. It was found that the produced oil from dispersed ultrafine Co-Mo/Al2O3 catalyst (dp=2.6μm) exhibited superior light oil characteristics and quality than that produced with the fixed-bed of pelleted Co-Mo/Al2O3 (1.2mm diameter×2–5mm length). The API gravity of the feed oil was 13.8° and the produced oil showed an increase of 5.6° in the fixed bed and 8.7° with the dispersed catalyst. Unlike the fixed-bed of pelleted Co-Mo/Al2O3 which may suffer from diffusion limitations, rapid deactivation, and channelling effect, the ultrafine particles presented high surface area to volume ratio, reducing the chances of pore plugging, have more accessible reaction sites per unit mass, and lead to enhanced cracking of macromolecules. Moreover, the reduction of sulphur of 38.6% and (Ni+V) content of 85.2% in the produced oil show greater heteroatom removal compared to 29% (sulphur) and 45.6% (Ni+V) observed in the product from the fixed-bed.

Down-hole heavy crude oil upgrading by CAPRI: Effect of hydrogen and methane gases upon upgrading and coke formation

Heavy oil and bitumen resources will need to be exploited to supplement depleting conventional oils worldwide as they gradually approach their peak production in the forthcoming decades. However, the physico-chemical characteristics of heavy oil and bitumen include high density, low distillates fraction, high viscosity, and high hetero-atom content which make extraction difficult and relatively expensive. The Toe-to-Heel Air Injection (THAI) and ‘add-on’ Catalytic upgrading process in situ (CAPRI) were specifically developed for the recovery and upgrading of heavy oil and bitumen. In this study, the effects of reaction gas media used in THAI–CAPRI were investigated, in particular the effects of using hydrogen, methane, nitrogen, and a blended gas mixture to simulate THAI combustion gases with Co–Mo/γ-Al2O3 catalyst at a reaction temperature of 425°C, pressure 10bar, and gas-to-oil ratio 50mLmL−1. Ex situ regeneration of the spent catalyst by thermal oxidation of the asphaltenes and coke deposits was also investigated. It was found that the average changes in API gravity of the produced oil were 4° using hydrogen, 3° with methane, 2.9° with THAI gas, and 2.7° with nitrogen above the value of 14° API gravity for the feed oil. The viscosity reduction and conversion of hydrocarbons with boiling point 343°C+ into lower boiling distillable fractions followed the same trend as the API gravity. The percentage loss in specific surface areas as a result of coke deposition in the different reaction gases were as follows: 57.2% for hydrogen, 68% for methane, and 96% for nitrogen relative to the surface area of the fresh catalyst of 214.4m2g−1. It was found that the spent catalyst contained 6 and 3wt.% less coke after six hours operation when using hydrogen and methane reaction gases respectively compared to 23.5wt.% coke content in a nitrogen atmosphere. Also, 48.5% of the catalyst specific surface area was recovered after oxidative regeneration.

Optimization of the CAPRI Process for Heavy Oil Upgrading: Effect of Hydrogen and Guard Bed

Toe-to-heel air injection (THAI) and its catalytic version CAPRI are relatively new technologies for the recovery and upgrade of heavy oil and bitumen. The technologies combine horizontal production well, in situ combustion, and catalytic cracking to convert heavy feedstock into light oil down-hole. The deposition of asphaltenes, coke, and metals can drastically deactivate the catalyst in the CAPRI process. A fixed bed microreactor was used to experimentally simulate the conditions in the catalyst zone of the oil well of CAPRI. In this study, oil upgrading and catalyst deactivation in the CAPRI process were investigated in the temperature range of 350–425 °C, pressure of 20 barg and residence time of 9.2 min. Additionally, a guard bed consisting of activated carbon particles prior to the active catalyst in a microreactor and/or the addition of hydrogen to the gas feed were used to minimize coke formation and catalyst deactivation through respectively removing and hydrocracking the coke precursors. It was ...