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Catalysis and Kinetics
Improving the Efficiency of THAI-CAPRI process by Nano-Catalysts Originated from Rock Minerals Milad Karimian, Mahin Schaffie, and Mohammad Hassan Fazaelipoor Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02289 • Publication Date (Web): 23 Oct 2018 Downloaded from http://pubs.acs.org on October 27, 2018
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Energy & Fuels
Improving the Efficiency of THAI-CAPRI process by Nano-Catalysts Originated from Rock Minerals
Milad Karimian* Department of Petroleum Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Jomhouri Blvd., Kerman, Iran.
[email protected] Mahin Schaffie Department of Petroleum Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Jomhouri Blvd., Kerman, Iran.
[email protected] Mohammad Hassan Fazaelipoor Department of Chemical and Polymer Engineering, Faculty of Engineering, Yazd University, University Blvd., Safayieh, Yazd, Iran
[email protected] Keywords: THAI-CAPRI process, in-situ combustion, nano-catalyst, thermal analysis, kinetic modeling
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ABSTRACT: Toe-to-Heel Air Injection (THAI) method is a modified pattern in situ combustion (ISC) which is applicable for the recovery of heavy oil reservoirs. A fixed bed of catalyst around the production well can improve performance and quality of the produced oil, however, pilot tests revealed rapid deactivation of the catalyst bed. Dispersion of fine catalyst particles (ideally nano particles) around the production well by carrier fluids may reduce the deactivation problem. In the first step of this study, three nano particles namely calcite, montmorillonite (MMT) and Cloisite 20A were dispersed in a heavy oil as candidate catalysts and subjected to simultaneous thermal analysis (STA). Kinetic parameters of different reaction zones were obtained by Coats and Redfern model and it was observed that 0.5 wt.% of the MMT more effectively catalyzed the combustion reactions. In the second step, selected sample was subjected to multiple heating rate experiments to study detailed kinetic effects. Results were analyzed by Vyazovkin isoconversional kinetic modeling and mechanism of different steps were determined. Results showed that all reaction regions follow nucleation-growth models. It was found that low temperature oxidation (LTO) reactions follow power law model (n=1/3) which means an acceleratory nucleation process. Nanoclay did not changed the reactions mechanism of both fuel deposition (FD) and high temperature oxidation (HTO) regions (both followed A3) but E0 and A0 in the FD step were increased from 187.3±19.0 kJ/mol and 51.2±3.4 min-1 to 235.0±21.8 kJ/mol and 59.7±3.3 min-1, respectively. In contrast to FD, Nanoclay decreased E0 and A0 of HTO from 100.1±17.2 kJ/mol and 34.6±2.1 min-1 to 81.3.0±18.5 kJ/mol and 31.0±2.3 min-1, respectively. In other words, MMT intensified LTO and catalyzed FD step and consequently altered the residual coke. It also decreased energy barriers and changed mass loss pattern of HTO which could be caused by change of reactant (coke) and resistance of MMT nucleation sites to heat in contrast to ingested nucleation sites of residual coke. Altogether, MMT improved LTO and prevented formation of excessive fuel; at the same time, MMT catalyzed HTO step and caused more uniform temperature profile which could sustain combustion.
x INTRODUCTION Depletion of light oil reservoirs has directed oil production towards unconventional resources such as heavy oil and bitumen reservoirs [1, 2]. Heavy oil contains a high level of macromolecules, metals and heteroatoms, and its density and viscosity are rather high. Heavy oil and bitumen are mainly extracted using thermal methods of enhanced oil recovery (EOR). Thermal methods of EOR could be divided into steam injection and In-Situ Combustion (ISC)
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methods. Commonly applied steam methods are Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS). The main drawback of these methods is large energy consumption for steam generation [3]. In Situ Combustion (ISC) methods are capable of in-situ generation of energy by oxidizing a part of reservoir oil. The heat generated by combustion reduces viscosity, and enhances heavy oil flow. It also upgrades the quality of oil via chemical reactions [4]. Many heavy oil reservoirs are proper candidates for ISC. In-situ combustion methods include conventional ISC, modified pattern methods like Toe-to-Heel Air Injection (THAI), and hybrid processes which combine other EOR methods (e.g. stem injection) with ISC. These methods enhance the recovery of heavy oil and bitumen significantly [5]. In order to improve upgrading capability of ISC, researchers proposed a catalyst-added version of THAI named as “Catalytic upgrading Process In-situ” (CAPRI). In this Process a fixed bed of catalyst is placed around the horizontal production wellbore to catalyze upgrading reactions of hot crude oil passing through [610]. Studies have shown that the fixed bed of catalyst deactivates fast due to the adsorption of macromolecules, residual coke, heavy metals and heteroatom on the surface of the pelleted catalysts during production [9, 11]. Dispersion of catalysts could be an alternative solution. Some investigators proposed injection of soluble salts of metallic catalysts dispersed in water into production wells [12, 13], while others preferred dispersion of ultrafine (i.e. micro or nano sized) catalyst in a transferring fluid [14, 15]. Nano-catalysts have advantages of large surface to volume ratio, more reaction sites, and less chance of pore plugging. Nano-catalysts were mostly chosen from transition metals (e.g. Mo, W, Co, or Ni) considering successful application of these metals in refinery units. For the injection of these metallic nano-catalysts to the reservoirs, however, recovery and reuse of the catalysts are of great concern. It might be a good practice to search for alternative nanoparticles originated from reservoir rock minerals which exhibit similar catalytic characteristics compared to known metallic additives. Such catalysts are more environmental and reservoir friendly and, after production, they can be treated as other fine particle migrated out of the reservoir. Many investigators used Thermal Analysis (TA) to investigate catalytic combustion of crude oil. Tadema [16] was the first one who studied crude oil combustion by differential thermal analysis (DTA). Drici and Vossoughi [17] analyzed the effect of surface area on oxidation by Thermogravimetric Analysis (TG) and Differential Scanning Calorimetry (DSC) , and reported changes of average activation energy. Effect of different mineralogy on pyrolysis and combustion of several crude oils showed that clay minerals of the reservoir rock can catalyze the oxidation of
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crude oil [18-20]. Most thermal analysis of crude oil combustion reveals three distinct reaction regions after initial vaporization. These regions are low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) [21-23]. Qualitative results of TA need to be transformed into quantitative results by kinetic models to investigate catalytic effects. Various kinetic models were proposed for catalytic combustion of crude oil [24-26] which could be generally classified as model-free and model-based methods. Model-based methods, like Coats-Redfern, presume a reaction model prior to calculations whereas model-free methods, e.g. isoconversional methods, bypass such assumption. Kovscek et al. were the first to introduce isoconversional kinetic models in ISC [27]. Some researchers believe that improving oxidation in crude oil is due to catalytic effects of NPs, while the others state that NPs promote oxidation of adsorbed crude oils to asphaltenes through surface exposure [28, 29] In this study TG/DTA analysis was performed by NETZSCH STA 409 PC to study catalytic effects of three types of nano particles. The aim of study is to select the best candidate nano-catalysts, its proper concentration, and its kinetic effects and mechanism of catalysis. Candidate nano catalysts where selected from reservoir rock minerals. Kinetic Modeling was performed with modified Coats-Redfern (CR) model and advanced isoconversional methods. CR model obtains kinetic parameters and enables quantitative study of catalyzed oxidation reactions while advanced methods evaluates variation of Arrhenius parameters and determines reaction model. x EXPERIMENTAL SECTION Crude oil samples were chosen from a heavy oil reservoir in Iran. Crude oil properties including weight percent of SARA (Saturated, Aromatic, Resin, and Asphaltene) fractions and crude oil composition are presented in Table 1 and Table 2, respectively.
Table 1: Heavy oil properties and SARA test results. Property
Quantity
Bubble point Pressure, Pb (kPa) Specific Gravity, sp. gr. API gravity (°API) Viscosity at Pb, μob (cP) Formation volume factor, Bo (bbl STB-1) Saturates wt.(%) Aromatics wt.(%) Resins wt.(%) Asphaltene wt.(%)
6308 0.9806 12.8 1654 at 323K 1.05 at 6308 kPa 12.3 21.7 51.3 14.7
Table 2: Partial Fractions of the heavy oil sample Components
H2S
N2
CO2
C1
C2
C3
iC4
nC4
iC5
nC5
C6
C7+
Heavy oil
0.0
0.7
0.2
10.4
2.4
1.9
1.6
4.0
3.6
2.3
2.7
70.2
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Crude oil density was measured according to ASTM D4052 and weight percent of saturated, aromatic, resin and asphaltene (SARA) components obtained according to ASTM D-2007. The effect of native limestone matrix on oxidation of heavy oil sample and was studied in our previous work and it was observed that limestone could decrease Arrhenius parameters (Ea & A) [21]. Similar studies were used bulk of clay minerals in different experimental orders which proved the catalytic role of these bulk minerals (unclear); it is expected that the nano particles made from these rock mineral can act as catalysts which can be injected to porous media and therefore improve the efficiency of THA-CAPRI method.
Table 3: Properties of candidate nano catalysts Code
Nano particle
Specific surface area (m2/g)
Average particle size
Density (g/cm3)
Particle Shape
A B C
CaCO3 Cloisite 20A Montmorillonite
32 ± 2 500 750
60 nm
