Eric O. Ansah | The University of Queensland, Australia (original) (raw)

Conference Presentations by Eric O. Ansah

There is a possibility of metal contamination and dietary overload associated with the grinding m... more There is a possibility of metal contamination and dietary overload associated with the grinding mechanism which results in surface interaction between the milled food stuffs and the metal grinding discs. This research was carried out on maize and cassava samples due to the high intake of dishes such as banku, akple, eba, kenkey, etc. by almost 90% of Ghanaians on daily basis. The research was aimed at ascertaining metal contamination and deducing the extent of contamination. Iron levels in dry maize, wet maize, dry cassava and wet cassava processed by the grinding disc in the Tarkwa Municipality were 12.04 mg/kg, 14.86 mg/kg, 14.98 mg/kg and 17.15 mg/kg respectively, and the corresponding levels in a wooden mortar and pestle were 5.11 mg/kg, 7.11 mg/kg, 7.11 mg/kg and 9.11 mg/kg. This corresponds to 135,109,110 and 88 percentage rise in the mortar and pestle values respectively. Comparing the iron levels in samples processed by the grinding disc and those processed at the lab, there was an increase in iron content resulting from the contribution of iron from the grinding disc to the food samples. There is a higher risk of metal overload in males aged 19 years to 50 years than their female counterparts given the average daily required intake of 8 mg/kg in males and 18 mg/kg in females. Health issues associated with iron overload such as hemochromatosis, cirrhosis, heart failure, bronze pigmentation of the skin and excessive fatigue necessitates immediate action to remediate the problem.

Papers by Eric O. Ansah

Minerals Engineering, 2024

Copper (Cu) extraction from low-grade ores is limited by the formation of secondary minerals that... more Copper (Cu) extraction from low-grade ores is limited by the formation of secondary minerals that can passivate the surfaces of Cu-sulphide minerals in these ores. Hence, a novel approach utilizing AlCl3 as a lixiviant was developed to modify coupled dissolution-reprecipitation processes at the mineral interface. The formation of Al-rich phases instead of Fe-hydroxysulphates enhanced Cu extraction through combined ferric-iron and proton-promoted dissolution. AlCl3 accelerated chalcopyrite and bornite dissolution by forming soluble intermediate Cu-phases (e.g., covellite) at consistently high Eh (550–650 mV) and acidity due to the Lewis acid property of AlCl3. X-ray diffraction analysis revealed that Na-bearing jarosite [(K0.61Na0.41) Fe3(SO4)2(OH)] and sideronatrite [Na2Fe(SO4)2(OH)(H2O)] formation in lixiviants without AlCl3 decreased Fe3+(aq) availability for Cu-sulphide minerals dissolution. In contrast, significant amounts of AlSO4+(aq) formed in the AlCl3-rich lixiviant at pH 1–3, which reduced the sulphate activity and decreased the saturation state of the Fe-hydroxysulphates. Further, AlCl3 promoted the formation of amorphous, porous Al-rich phases, facilitating quick Fe diffusion through the passivating layer and improving Cu recovery compared to lixiviants containing CaCl2, NaCl, or acid-only.

Minerals Engineering, Oct 31, 2023

Chalcopyrite is an abundant source of copper, which can be extracted from low-grade ores in heaps... more Chalcopyrite is an abundant source of copper, which can be extracted from low-grade ores in heaps. The dissolution of chalcopyrite is relatively slow partly because of the formation of secondary minerals at the chalcopyrite surface also referred to as surface ‘passivation’. Although the passivation mechanism has been extensively studied, present models do not adequately account for it. Hence, a surface-passivate model (SPM) was used in a reaction path model (RPM) to examine and illustrate how passivation limits copper recovery from chalcopyrite. In addition, the role of different gangue minerals and different chalcopyrite dissolution mechanisms were assessed by incorporating rate equations from Kimball et al. (2010) and Rimstidt et al. (1994) into the RPM, and the state of saturation was determined for various minerals to constrain limiting conditions for copper recovery. RPM with different rate laws describing proton-promoted, ferric-iron promoted, and combined ferric-iron-proton promoted chalcopyrite dissolution in the presence of gangue minerals in chloride system were used. Ferric-iron promoted chalcopyrite dissolution was the fastest reaction mechanism leading to the highest copper mobilization. However, copper mobilization was limited by the formation of iron-hydroxy sulphates (e.g., jarosite), and iron oxide (e.g., hematite) and different gangue minerals, pointing to the importance of accurate representation of primary and secondary reactions, their co-location, and their reaction kinetics. The SPM was capable to simulate surface coverage of the chalcopyrite surface by jarosite, thereby lowering the reactive surface area and consequently suppressing chalcopyrite dissolution. Conversely, the SPM failed to model the incongruent dissolution of chalcopyrite leading to a copper sulfide layer deficient in iron in the form of covellite because covellite was continuously undersaturated in trial models. Further, the presence of gangue minerals like hematite and gypsum may have a positive effect on chalcopyrite dissolution, whereas the presence of silicates (e.g., feldspar and muscovite) have a negative influence. The findings of this study are important as it provides new insights into concurrent reactions controlling the recovery of copper in heaps and how these reactions can be best modelled.

Summary Large volumes of oil sit within our reach primarily of the strong capillary forces, which... more Summary Large volumes of oil sit within our reach primarily of the strong capillary forces, which themselves are subsequent to the attraction between the polar ends of the oil and the surface charges of bearing-matrix. Altering these interactions occurring within tiny pore throats or even more, unveiling the extent to which the geochemistry impacts these interactions can invariably improve the production. Therefore, we evaluated the performance of water-based nanofluid for oil production with the respect to the geochemistry. Alumina-silica nanocomposite (Al/Si-NP), synthesized by plasma-method, was used as primary material. Functionalized by dispersing 0.25 wt.% lyophilized NP into the formation water (TDS=4301 ppm) water under carbon dioxide bubbling. The nanofluid, NF, obtained therefrom, was then used for coreflooding tests, which aim at displacing a dead heavy oil (ρ =0.854 g/cm3) from a waterflooded Berea sandstone. The ionic composition of the effluent fluids was tracked and further used for modeling the geochemical interactions. The latter considered mineral precipitation and dissolution as well as ion adsorption and desorption. Model calculations were performed using the transport algorithm in PHREEQC. The experimental results from coreflood tests showed that Al/Si-NP, injected into a waterflooded sandstone, could displace up to 11% of the oil trapped, which was 10 times higher if no nanofluid as injected. Ionic tracking further revealed that the dissolution of albite along with anorthite weathering; both mechanisms concurred to the logjamming of Al/Si-NF. Furthermore, the geochemical modeling revealed weak and reversible cation exchange between sodium (Na+) and calcium (Ca2+). Also, we found that the pH of the preflush should be mildly basic with for controllable anorthite and albite precipitation plus silica cementation, from which derive Al-Si-NF aggregation. These points were further verified experimentally when the ionic composition was altered accordingly to the geochemical modeling, leading to the conclusion that albite, anorthite and silicate precipitation promotes high recovery, due to high Na+ and K+ ions. Silica cementation was proven to increase formation rock wettability.

Petroleum Science and Technology, 2018

This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe a... more This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe action and metabolites; predicted hydrogeochemical reactions involved with nutrient-brine interaction in reservoirs. PHREEQC was used to simulate reactions between the reservoir brine and nutrient minus microbe. Hitherto, UTCHEM was employed for the enhancement of oil viscosity by assuming production of gases and by the direct microbe action. The model depicted the precipitation of calcite plus dissolution of k-feldspar combined with the evolution of CO 2 and CH 4 influenced by temperature and pH. Oil recovery was directly proportional to salinity reduction and increasing nutrient concentration.

International Journal of Petroleum Engineering, 2018

Primarily, most oil wells in the West Africa transform region are produced using water or water a... more Primarily, most oil wells in the West Africa transform region are produced using water or water alternating gas. This is believed to be unsustainable going forward. Also, though the region contributes less to global greenhouse emission, global warming effects in the region cannot be undermined. Microbial enhanced oil recovery (MEOR) has been proven worldwide to be environmentally friendly as well as less costly to develop. Despite the advantages of MEOR over other oil recovery methods, operating companies in the region are yet to apply this bespoke technology. Therefore, this study reviews the potential applicability of MEOR process to West African oil fields comparing the geology and physiochemical properties to major oil fields in South America (where MEOR has been previously applied). Applying MEOR in the region could be a major step towards improving production of new oil wells and enhancing sustainability of old oil wells.

Journal of Petroleum Science and Engineering, 2018

The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as A... more The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as AR80) for MEOR with the further objective to quantify the uncertainty of production forecast in terms of the cumulative probability distribution. A series of core flood experiments conducted in water-flooded Berea sandstone showed that up to 51% of initial oil-in-place was recovered when the plugs were treated with AR80 and shut-in for 14 days. Mainly, the oil recovery mechanisms were attributed to viscosity enhancement, wettability changes, permeability and flow effects. Matching the laboratory data using artificial intelligence: the optimized cumulative oil recovery could be achieved at an enthalpy of 894.2 J/gmol, Arrhenius frequency of 8.3, residual oil saturation of 20%, log of capillary number at microbe flooding stage of-1.26, and also depicted a history match error less than 3%. Therefrom, a sensitivity analysis conducted on reservoir shut-in period effect on oil recovery revealed that a relatively shorter shut-in period is recommended to warrant early incremental oil recovery effect for economical purposes. In addition, MEOR could enhance the oil recovery significantly if a larger capillary number (between 10 −5 and 10 −3.5) is attained. Per probabilistic estimation, MEOR could sustain already water-flooded well for a set period of time. This study showed that there is a 20% frequency of increasing the oil recovery by above 20% when a mature water-flooded reservoir is further flooded with AR80 for 2 additional years. Lastly, it was demonstrated herein that increasing the nutrient (yeast extract) concentration (from 0.1-1% weight) had less or no significant effect on the oil viscosity and subsequent recovery.

Egyptian Journal of Petroleum, 2017

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, an... more Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30°C/ min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20-227°C), stage 2 (SII): combustion of heavy hydrocarbon (227-527°C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502-877°C). The results showed that the rate of change of the oil sand conversion with time da dt À Á was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30°C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min À1 , while the activation energy, E a , was 11.2-12.5 KJmol À1 (the percentage weight loss, W t , was 0-3.6 %w/w; and the conversion, a, was 0-0.2.). At SII, the values of A and E a were 2.1-5.5 min À1 and 17.6-19 KJmol À1 , respectively (W t = 3.1-15.88 %w/w; a = 0.17-0.86.). The value of A at SIII was 5.5E11-1.1E13 min À1 , while E a was 160-200 KJmol À1 (W t = 15.33-17.99 %w/w; and a = 0.84-0.99).

Journal of Dispersion Science and Technology, 2019

We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geoc... more We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geochemistry inherent. Two microemulsion (ME) formulations were prepared from Gemini surfactant, heavy oil (API 16.6) and saline water and further injected in a Berea sandstone. Monitoring the ionic composition of the effluent water showed that the emulsion cut and the sludge deposition were both subsequent to the degradation of the formulation, owing to the dissolution of feldspar due to the water acidity. As per the modeling study, a weak and reversible cation exchange between sodium (Na þ) and calcium (Ca 2þ) was highlighted. Herein was shown that Na þ could prevent and/or mitigate the heightened adsorption of ME to the rock surface. A mildly basic pH for controllable anorthite and albite precipitation plus silica cementation due to sludge formation. We hypothesized that feldspar alteration has an antagonistic effect on the oil expulsion efficiency and ME adsorption. Anhydrite alteration affects CEOR negatively due to high divalent ions causing high ME degradation due to adsorption. Whereas, albite, anorthite and silicate precipitation promotes high recovery and less ME adsorption, due to high Na þ and K þ ions. Silica cementation was proven to increase formation rock wettability. Hence, to achieve high oil recovery and minimal surfactant loss due to adsorption, we propose a high and stable Na þ presence.

SPE Annual Technical Conference and Exhibition

Journal of Petroleum Exploration and Production Technology

This study is intended to expand the scope of microbial enhanced oil recovery (MEOR) simulation s... more This study is intended to expand the scope of microbial enhanced oil recovery (MEOR) simulation studies from 1D to field scale focussing on fluid viscosity variation and heterogeneity that lacks in most MEOR studies. Hence, we developed a model that incorporates: (1) reservoir simulation of microbe-induced oil viscosity reduction and (2) field-scale simulation and robust geological uncertainty workflow considering the influence of well placement. Sequential Gaussian simulation, co-kriging and artificial neural network were used for the petrophysical modelling prior to field-scale modelling. As per this study, the water viscosity increased from 0.5 to 1.72 cP after the microbe growth and increased biomass/biofilm. Also, we investigated the effect of the various component compositions and reaction frequencies on the oil viscosity and possibly oil recovery. For instance, the fraction of the initial CO 2 in the oil phase (originally in the reservoir) was varied from 0.000148 to 0.005 to promote the reactions, and more light components were produced. It can be observed that the viscosity of oil reduced considerably after 90 days of MEOR operation from an initial 7.1-7.07 cP and 6.40 cP, respectively. Also, assessing the pre-and post-MEOR oil production rate, we witnessed two main typical MEOR field responses: sweeping effect and radial colonization occurring at the start and tail end of the MEOR process, respectively. MEOR oil recovery factors varied from 28.2 to 44.9% OOIP for the various 200 realizations. Since the well placement was the same for all realizations, the difference in the permeability distribution amongst the realizations affected the microbes' transport and subsequent interaction with nutrient during injection and transport.

Journal of Dispersion Science and Technology, 2019

We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geoc... more We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geochemistry inherent. Two microemulsion (ME) formulations were prepared from Gemini surfactant, heavy oil (API 16.6°) and saline water and further injected in a Berea sandstone. Monitoring the ionic composition of the effluent water showed that the emulsion cut and the sludge deposition were both subsequent to the degradation of the formulation, owing to the dissolution of feldspar due to the water acidity. As per the modeling study, a weak and reversible cation exchange between sodium (Na+) and calcium (Ca2+) was highlighted. Herein was shown that Na+ could prevent and/or mitigate the heightened adsorption of ME to the rock surface. A mildly basic pH for controllable anorthite and albite precipitation plus silica cementation due to sludge formation. We hypothesized that feldspar alteration has an antagonistic effect on the oil expulsion efficiency and ME adsorption. Anhydrite alteration affects CEOR negatively due to high divalent ions causing high ME degradation due to adsorption. Whereas, albite, anorthite and silicate precipitation promotes high recovery and less ME adsorption, due to high Na+ and K+ ions. Silica cementation was proven to increase formation rock wettability. Hence, to achieve high oil recovery and minimal surfactant loss due to adsorption, we propose a high and stable Na+ presence.

The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as A... more The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as AR80) for MEOR with the further objective to quantify the uncertainty of production forecast in terms of the cumulative probability distribution. A series of core flood experiments conducted in water-flooded Berea sandstone showed that up to 51% of initial oil-in-place was recovered when the plugs were treated with AR80 and shut-in for 14 days. Mainly, the oil recovery mechanisms were attributed to viscosity enhancement, wettability changes, permeability and flow effects. Matching the laboratory data using artificial intelligence: the optimized cumulative oil recovery could be achieved at an enthalpy of 894.2 J/gmol, Arrhenius frequency of 8.3, residual oil saturation of 20%, log of capillary number at microbe flooding stage of −1.26, and also depicted a history match error less than 3%. Therefrom, a sensitivity analysis conducted on reservoir shut-in period effect on oil recovery revealed that a relatively shorter shut-in period is recommended to warrant early incremental oil recovery effect for economical purposes. In addition, MEOR could enhance the oil recovery significantly if a larger capillary number (between 10−5 and 10−3.5) is attained. Per probabilistic estimation, MEOR could sustain already water-flooded well for a set period of time. This study showed that there is a 20% frequency of increasing the oil recovery by above 20% when a mature water-flooded reservoir is further flooded with AR80 for 2 additional years. Lastly, it was demonstrated herein that increasing the nutrient (yeast extract) concentration (from 0.1 to 1% weight) had less or no significant effect on the oil viscosity and subsequent recovery.

This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe a... more This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe action and metabolites; predicted hydrogeochemical reactions involved with nutrient – brine interaction in reservoirs. PHREEQC was used to simulate reactions between the reservoir brine and nutrient minus microbe. Hitherto, UTCHEM was employed for the enhancement of oil viscosity by assuming production of gases and by the direct microbe action. The model depicted the precipitation of calcite plus dissolution of k-feldspar combined with the evolution of CO2 and CH4 influenced by temperature and pH. Oil
recovery was directly proportional to salinity reduction and increasing nutrient concentration.

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, an... more Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30 °C/ min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20–227 °C), stage 2 (SII): combustion of heavy hydrocarbon (227–527 °C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502–877 °C). The results showed that the rate of change of the oil sand conversion with time da dt À Á was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30 °C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min À1 , while the activation energy, E a , was 11.2–12.5 KJmol À1 (the percentage weight loss, W t , was 0–3.6 %w/w; and the conversion, a, was 0–0.2.). At SII, the values of A and E a were 2.1–5.5 min À1 and 17.6–19 KJmol À1 , respectively (W t = 3.1–15.88 %w/w; a = 0.17–0.86.). The value of A at SIII was 5.5E11–1.1E13 min À1 , while E a was 160–200 KJmol À1 (W t = 15.33–17.99 %w/w; and a = 0.84–0.99).

Minerals Engineering, 2024

Minerals Engineering, Oct 31, 2023

Petroleum Science and Technology, 2018

International Journal of Petroleum Engineering, 2018

Journal of Petroleum Science and Engineering, 2018

Egyptian Journal of Petroleum, 2017

Journal of Dispersion Science and Technology, 2019

SPE Annual Technical Conference and Exhibition

Journal of Petroleum Exploration and Production Technology

Journal of Dispersion Science and Technology, 2019

We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geoc... more We evaluated the performance of microemulsions for a heavy oil reservoir with respect to the geochemistry inherent. Two microemulsion (ME) formulations were prepared from Gemini surfactant, heavy oil (API 16.6°) and saline water and further injected in a Berea sandstone. Monitoring the ionic composition of the effluent water showed that the emulsion cut and the sludge deposition were both subsequent to the degradation of the formulation, owing to the dissolution of feldspar due to the water acidity. As per the modeling study, a weak and reversible cation exchange between sodium (Na+) and calcium (Ca2+) was highlighted. Herein was shown that Na+ could prevent and/or mitigate the heightened adsorption of ME to the rock surface. A mildly basic pH for controllable anorthite and albite precipitation plus silica cementation due to sludge formation. We hypothesized that feldspar alteration has an antagonistic effect on the oil expulsion efficiency and ME adsorption. Anhydrite alteration affects CEOR negatively due to high divalent ions causing high ME degradation due to adsorption. Whereas, albite, anorthite and silicate precipitation promotes high recovery and less ME adsorption, due to high Na+ and K+ ions. Silica cementation was proven to increase formation rock wettability. Hence, to achieve high oil recovery and minimal surfactant loss due to adsorption, we propose a high and stable Na+ presence.

The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as A... more The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as AR80) for MEOR with the further objective to quantify the uncertainty of production forecast in terms of the cumulative probability distribution. A series of core flood experiments conducted in water-flooded Berea sandstone showed that up to 51% of initial oil-in-place was recovered when the plugs were treated with AR80 and shut-in for 14 days. Mainly, the oil recovery mechanisms were attributed to viscosity enhancement, wettability changes, permeability and flow effects. Matching the laboratory data using artificial intelligence: the optimized cumulative oil recovery could be achieved at an enthalpy of 894.2 J/gmol, Arrhenius frequency of 8.3, residual oil saturation of 20%, log of capillary number at microbe flooding stage of −1.26, and also depicted a history match error less than 3%. Therefrom, a sensitivity analysis conducted on reservoir shut-in period effect on oil recovery revealed that a relatively shorter shut-in period is recommended to warrant early incremental oil recovery effect for economical purposes. In addition, MEOR could enhance the oil recovery significantly if a larger capillary number (between 10−5 and 10−3.5) is attained. Per probabilistic estimation, MEOR could sustain already water-flooded well for a set period of time. This study showed that there is a 20% frequency of increasing the oil recovery by above 20% when a mature water-flooded reservoir is further flooded with AR80 for 2 additional years. Lastly, it was demonstrated herein that increasing the nutrient (yeast extract) concentration (from 0.1 to 1% weight) had less or no significant effect on the oil viscosity and subsequent recovery.

This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe a... more This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe action and metabolites; predicted hydrogeochemical reactions involved with nutrient – brine interaction in reservoirs. PHREEQC was used to simulate reactions between the reservoir brine and nutrient minus microbe. Hitherto, UTCHEM was employed for the enhancement of oil viscosity by assuming production of gases and by the direct microbe action. The model depicted the precipitation of calcite plus dissolution of k-feldspar combined with the evolution of CO2 and CH4 influenced by temperature and pH. Oil
recovery was directly proportional to salinity reduction and increasing nutrient concentration.

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, an... more Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30 °C/ min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20–227 °C), stage 2 (SII): combustion of heavy hydrocarbon (227–527 °C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502–877 °C). The results showed that the rate of change of the oil sand conversion with time da dt À Á was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30 °C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min À1 , while the activation energy, E a , was 11.2–12.5 KJmol À1 (the percentage weight loss, W t , was 0–3.6 %w/w; and the conversion, a, was 0–0.2.). At SII, the values of A and E a were 2.1–5.5 min À1 and 17.6–19 KJmol À1 , respectively (W t = 3.1–15.88 %w/w; a = 0.17–0.86.). The value of A at SIII was 5.5E11–1.1E13 min À1 , while E a was 160–200 KJmol À1 (W t = 15.33–17.99 %w/w; and a = 0.84–0.99).