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Athabasca Bitumen In Situ Upgrading Reaction Monitoring. Operational Parameters vs. Distillates Nature and Permanent Upgrading Achievable Lante A Carbognani Ortega, Christian Nubar Hovsepian, Carlos E. Scott, Pedro Rafael Pereira-Almao, Robert Gordon Moore, Sudarshan A. (Raj) Mehta, and Matthew G. Ursenbach Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b00578 • Publication Date (Web): 23 Jun 2016 Downloaded from http://pubs.acs.org on June 24, 2016
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Athabasca Bitumen In Situ Upgrading Reaction Monitoring. Operational Parameters vs. Distillates Nature and Permanent Upgrading Achievable Lante Carbognani Ortega, Christian Hovsepian, Carlos E. Scott, Pedro Pereira-Almao, R. Gordon Moore, Sudarshan A. Mehta, Matthew G. Ursenbach Schulich School of Engineering, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
ABSTRACT Athabasca Bitumen upgrading via In Situ Combustion (ISC) and In Situ Upgrading Technology (ISUT) was studied in the present work, addressing three aspects related to these processes: I. Monitoring techniques specially developed for getting distillation characteristics for products and their fractions, II. How distillation properties depend on process set up experimental conditions, III. Assess the permanent upgrading levels achieved for products from both studied processes. High temperature simulated distillation (HTSD) techniques were conceived for getting analysis turnarounds of 1-2 weeks, instead of month spans required when relying on standard physical distillation methodologies. Developed monitoring procedures guaranteed samples integrity, i.e., volatile fractions (545ºC] x100 Feedstock wt% > 545ºC
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Losses derived from the preceding sampling and HTSD analysis protocol were estimated with known samples, being < 1% wt, independent of the jar size and its void headspace (see support Figure S1). 2.2. Physical distillation and samples recombination. The work-up for physical treatment of ISC product aliquots was difficult and time consuming due to the large amount of free and emulsified water routinely found. Physical water removal was performed by mechanical means. Emulsified water was obtained by distillation carried out with a minidistillation unit (short path distilling head P/N 9317-52, ACE Glass, Vineland, NJ-USA, coupled to a three necked (14/20) round bottom flask). The unit was provided with high stirring rate (magnetic bar) and N2 bubbling through the sample bulk. Water and light distillates were recovered together in a cryo-trap (acetone-dry ice). Water was separated afterwards by decantation. The frequency of success for the vapor distillation separation was about 30%, i.e., 1 in 3 runs was successful, because the large amount of water present made it difficult to avoid sudden vapor expansion and contamination of the distillates. Distillation residue is dissolved (CH2Cl2, typically), filtered, solvent distilled and the sample left inside a vacuum oven until constant weight is determined. Physical distillation and recombination of dried distillates plus the treated non-volatile fraction allowed production of representative aliquots for further characterization. The former procedure implies large efforts both in labor and time requiring from three weeks to three months for completion of tests having 10 to 30 aliquots respectively. 2.3 In Situ Upgrading (ISUT) with hot fluid injection; experimental details.
Two
dimensional representation of a reservoir zone was conceived by using two parallel
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horizontal wells, as shown on Figure 2. The interwell represents the catalytic reaction zone from the reservoir. The branches mimic the overlaying and horizontal portions of the reservoir. Vacuum residue, hydrogen and UD-cat were injected into the porous medium through the injection well; the upgraded oil and unconsumed hydrogen were recovered from the bottom well. The rig was assembled with one inch diameter Swagelok tubing, provided with external concentric tubing which maintained adiabatic conditions (vacuumed inter tubing space). All sections from the rig were packed as much as possible with silica sand and impregnated with bitumen, before carrying out ISUT experiments; details on the process10 and units’ operation were recently reported.11 At the end of the experiment described in the present work, the unit was disassembled and the packed sands from each of the three branches and the interwell zone were recovered by mechanical means. As will be described in Section 3.2, three oil sand zones were recovered from each branch / interwell, totaling 12 spent sand samples. After homogenizing the oil sand following three sequential “quartering” procedures as described in analytical chemistry monographs,26 3-5 g of homogenized sands were weighted into 20 mL scintillation vials (appreciation to 0.1 mg). Sand aliquots were extracted with CS2 (Sigma-Aldrich P/N 180173, >99.9%; 5x4 mL). The extracts were transferred into 25 mL volumetric flasks and CS2 added to the mark. Water, if present, floated over the CS2 extracts and was mechanically retrieved. The solutions were filtered directly into 2 mL GC vials, using luer tip syringes coupled to 0.45 µm filters. Sample aliquots were analyzed via HTSD, as described in Section 2.1. Next, CS2 was distilled from a known aliquot from the extracts using a micro-rotaryevaporator (Heidolph model W-Mikro) provided with a N2 stream; aliquots were then kept for 1 hour
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inside a vacuum oven maintained at 80ºC and 20 inches vacuum. Weights of remaining HCs boiling about ≥230ºC (C13+) were determined with an analytical balance (Mettler model XS204). The wt% of materials boiling below ~230ºC was estimated in each case from the corresponding HTSD distillation curve using as input the weight of heavy HCs (≥230ºC) and the weight of CS2 contained in the volumetric flask. Details for the calculations involved will be addressed in Section 3.2.
3. RESULTS
3.1 Athabasca Bitumen In Situ Combustion (ISC) Testing in a 1-D Combustion Pilot rig. This section will address three topics: (1) General aspects on ISC processing, for later discussion of results gathered in this work, (2) The analytical protocol conceived and developed for being able to analyze sample aliquots from ISC tests, (3) Correlation of analytical results and achieved conversion levels with operational set up parameters. 3.1.1 General aspects on ISC bitumen processing. Produced fluids from three ISC tests carried out with Athabasca Bitumen are discussed in this paper. The tests were AICISE #1, #2 and #16. All of these tests involved sand matrix and bitumen from the Athabasca Oil Sands region but the core and operating conditions were not the same. AICISE #1 and #2 were performed on different sand matrix and bitumen samples and at different operating pressures (5.52 MPag) than those for AICISE#16 (3.45 MPag). All three tests involved the injection of dry air (no water coinjected with the air). In addition to the origin of the reservoir samples and operating pressures, the important differences in the individual test operating parameters included: (1) AICISE #1 had uniformly UD-Cat
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carried in the aqueous phase mixed with the original bitumen. A surfactant was used to obtain good mixing between the catalyst and the hydrocarbon phase. (2) AICISE #2 was a traditional ISC test on a re-stored state core, with no catalyst, and (3) AICISE #16 involved a re-combined core but downstream of the core there was a commercial supported HDS catalyst mixed with silica sand that was maintained at a temperature of 325ºC. Bitumen and connate water displaced by the combustion zone flowed through the externally heated catalyst bed and a significant level of upgrading was achieved. Connate water was introduced to the cores during the preparation procedures. On a mass basis, the ratio of connate water to initial bitumen were 0.31, 0.24 and 0.31 g/g for AICISE #1, #2 and #16 respectively. Water produced by the combustion reactions will alter the expected cumulative water/bitumen ratio in the produced fluids but in general, overall produced water/bitumen ratios should approach those in the initial core. The reason for this is that the portion of the core that is swept by the combustion zone is essentially free of residual hydrocarbon or water. Instantaneous water/bitumen ratios change with run time depending on the flow characteristics of the core matrix. The flow characteristics are dependent on the mineralogy of the sand. Production of fines with the liquid samples depends on the presence of clays and fines in the sand matrix as well as emulsification characteristics of the bitumen. The presence of iron containing minerals will lead to rust in the produced samples if the temperatures within the core during the combustion test result in their decomposition. Spent UD-cat catalyst will be present in the produced fluids and depending on the effectiveness of this dispersed catalyst, the catalyst particles may be coated with coke. In general, the properties of the produced fluids are
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important parameters with respect to analyzing the effectiveness of an ISC process in a given reservoir under specified operating conditions. 3.1.2 Conceived analytical protocol for ISC product aliquots’ analysis. Figure 1 illustrates how ISC sample aliquots were taken for further physico-chemical characterization of tests carried in the 1-D combustion tube. Each test usually takes about 10 hours for completion since inert gas injection (Helium) was initiated, followed by compressed air and finally helium again to displace the stored gas from the core. About 10-30 product aliquots were taken during one run. Aiming at understanding how much upgrading could be produced within ISC tests, a protocol was conceived for being able to sample representative aliquots, avoiding volatile losses. The sampling protocol schematic is presented on Figure 3. About six aliquots could be processed and analyzed via HTSD in one labor day (6 aliquots ran in triplicate within a dual channel HTSD analyzer). The former procedures enable that in about 3 labor days, HTSD analysis for a ISC test comprising up to 12 aliquots, could be analyzed. More complex tests (up to 30 aliquots), usually took two weeks for completion. Despite these long analyses turnarounds, HTSD analysis was found to be very convenient for two reasons: I) Volatile losses were controlled to less than 1 wt% (See Figure S1), II) The work-up protocol presented on Figure 3 requires 1/3 to 1/4 less time compared to physical work-up, which span from 1-3 months. ISC products successful analyses following the protocol presented on Figure 3 must comply with two criteria: I) Repeatable triplicate water analysis, II) Repeatable triplicate HTSD analysis, meeting specified precision limits in both cases. Figure 4 illustrates successful emulsified water analysis (KF titration) for one ISC test. If precision
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is better than 10 %RSD, the test is accepted, which in average is the case illustrated in this example. Figure 5 shows the distributions of free/emulsified water and organics for the aliquots correspondind to test AICISE #16. Comparing emulsified wt% water content distributions presented on Figures 4 and 5, suggests that tests AICISE # 1 and #16 were different in this regard, i.e., maxima shifted from late produced aliquots (aliquot 15/22 for test AICISE#1, Fig.4) towards early produced aliquots (aliquot 4/12 for test AICISE#16, Fig.5). It was found that the remainder conducted 24 tests were all different, i.e., the ratios HCs / water contents were different for all of them. Regarding HTSD repeatability, it was found that the greatest deviations routinely occurred beyond AEBPs >500ºC, because water if present, is not detected by the FID detector and appears as non-eluted residue. In addition, beyond AEBP 500ºC, complex thermal cracking effects have been found to affect distillation results for heavy oil components.16,17,27 Figure 6 illustrates typical cases of triplicate HTSD analysis. Panel A shows that successful homogenization and analysis was achieved in this case, indicating good reproducibility for determined distilled fractions at 545ºC (%RSD ≤5). Panel B indicates that one from the three aliquots showed larger water contents compared to the other two; however, analysis precision at 545ºC was found reasonable thus the test was accepted. Results presented in Panel C immediately put in evidence a failed attempt, indicating that this aliquot had to be reprocessed. Results from Panel D were more complex to assess, i.e., three replicas matched while one fourth run deviated from the trend shown by the preceding three; a further point of attention derived from the large differences observed between the distillation curves for this sample and the other
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analyzed aliquots. Repeated homogenization and analysis provided repeatable results found to fall within a reasonable trend within the whole set, thus being accepted. 3.1.3 ISC product distillation mappings correlated to operation parameters and appraisal of permanent upgrading levels achieved. When reviewing Figures 4 to 6, it is important to note that the aliquot number is a reflection of the time at which the sample is taken relative to the total time of the combustion test. Figures 4 and 5 illustrate the general trend that water produced early in the test is normally in the emulsified state while free water is produced as the test approaches the mature state where the combustion zone is approaching the production end of the core. Figure 6 illustrates the changes that occur in the distillation curves of the produced oil at different times during the test. Distillation curves from two tests are shown in Figure 6. Produced bitumen associated with Figure 6A. to 6C. was produced during AICISE #16 which has a supported catalyst bed downstream of the core. Aliquot #2 (Figure 6A) was produced during the period immediately following ignition but before the catalyst bed was up to the design temperature of 325ºC. Aliquot 3, associated with Figure 6C. was collected as the catalyst bed approached the design temperature whereas aliquot 8 (Figure 6B.) was collected when the catalyst bed was at the design temperature but the run has progressed to the state that free water was starting to be produced. Figure 6D. summarizes the change in the produced bitumen distillation characteristics during AICISE #2 which was a standard dry combustion test not involving UD-cat or fixed bed catalysts. One sample failed the tests of consistency (aliquot 15). A review of the temperatures associated with the advancing combustion zone during the period just before this sample was produced shows that the peak temperatures in the two zones from which the oil was mobilized were
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815 and 862ºC as compared to average peak temperatures of 595ºC as observed during AICISE # 1 and #16. It appears that very heavy fractions were mobilized in response to the extraordinary elevated level of the peak temperatures and that these heavy fractions did not blend with the bitumens produced in response to more normal peak temperatures. The remainder from this section will be devoted to present the whole set of results achievable following the proposed analysis work-up and characterization protocol (Figure 3) for one selected ISC test, AICISE#16 (ISC#385). The discussion attempts to show the richness of information provided with the characterization protocol herein discussed. Figure 7 presents the chromatograms and distillation curves determined for the 12 sampled aliquots from test AICISE #16. Panel A shows how the heavy fractions appearing at retention times spanning from about 20-30 min decrease, while the light ends (0-10 min) simultaneously increase as the combustion zone approaches the outlet of the core. The trends clearly show formation of light compounds, meaning cracking reactions for heavy components occurring inside the combustor. These light fractions are located downstream of the combustion zone. Fraction 2 showed slight down-grading (associated with the ignition phase), i.e., showed lower amount of light components, compared to the other studied aliquots and even, compared to the feedstock. If the fractions work-up had followed the practice most oil laboratories have routinely in place, i.e., water azeotropic distillation with toluene, all the light ends (20 pore volumes in 2-D rigs (see Figure 2), the nature of the hydrocarbons remaining within each zone from the rig was investigated. The branches were disassembled and sands mechanically recovered from different zones and stored in capped jars. A schematic for aliquots sampling and the amount of hydrocarbon remaining in each zone, are respectively presented in Figures
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10A and 10B. The findings indicate that HCs are systematically depleted within the three existing branches, following the decreasing order: Top Branch (TB) > Middle Branch (MB) > Lower Branch (LB). The process for determining the former values is unique, relying on HTSD as will be discussed below. Recovery of remaining hydrocarbons after one ISUT test, can only be achieved via solvent extraction, because these fractions are adsorbed/trapped inside the mineral matrix. The problem derived from solvent presence is the impossibility of removing it by distillation, since volatile hydrocarbons (230ºC mass (mg) (from aliquot evaporated) vSol: solution volume (mL) (fixed to 25.0 mL for the present experiments) vA: evaporated aliquot volume (mL) m230C+: mass total HC > 230ºC (in 25.0 mL solution) mT: total hydrocarbon mass (mg) [(HC 230C-) + (HC 230C+)] HTSD%230C-: % distilled to 230ºC determined by HTSD
Knowing the sample mass contained in extracted solutions (mT) and the oil sand mass extracted, the wt% hydrocarbons remaining within each branch-zone from the rig is calculated with the Equation (5): wt% HC /branch-zone = mT x100 / MEOS
(5)
Where MEOS means: Mass Extracted Oil Sand (in mg) From the preceding, the total mass of hydrocarbons in each branch-zone at the end of ISUT processing, is calculated with Equation (6): Mass total HCs/branch-zone = [(wt% HC/ branch-zone) / 100] x MOSB Where MOSB means: Mass oil sand (retrieved from) Branch-zone The mass of hydrocarbons in each branch is calculated with Equation (7): 3
Mass total HCs/branch =
Σ (branch-zone) i i=1
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In the preceding discussion the abundance of the fraction distilling below 230ºC (HTSD230ºC-) was calculated from the HTSD distillation curve using the weight of material boiling >230ºC (m230ºC+) as input. This procedure was deduced from the analysis of several known sample mixtures containing volatile fractions spanning from 10 to 50 wt%. Figure 11 illustrates the procedure for two bitumen/heavy oil samples which contain known amounts of volatile end (
