Beneficial Effects Of CO2 Research Articles

Experimental and Numerical Simulation Study on CO2-Assisted Steamflooding in Ultraheavy Oil Reservoirs

Summary Certain ultraheavy oil reservoirs with depths approaching 1000 m feature wide well spacing. After cyclic steam stimulation (CSS), cold oil zones with high residual oil saturation exist between wells. This leads to a high oil saturation at the steam front during the subsequent steamflooding process, which in turn results in a high injection pressure. The simultaneous injection of CO2 and steam into the formation can optimize formation pressure and enhance steam utilization efficiency. A majority of laboratory-based experimental studies have reported favorable outcomes with CO2-assisted steamflooding. However, some field tests of CO2-assisted steamflooding have encountered severe steam channeling problems, resulting in oil recovery and an oil/steam ratio below the expected level. Consequently, this study uses an ultraheavy oil reservoir as a case study and integrates physical simulation with numerical simulation to investigate the impact of CO2-assisted steamflooding on enhanced oil recovery in ultraheavy oil reservoirs. The findings suggest that the beneficial effect of CO2 in reducing oil viscosity and injection pressure plays a significant role in models with smaller thickness, thereby improving oil production rate and recovery factor. However, as the thickness of the model increases, the adverse effect of CO2 exacerbating steam channeling becomes increasingly evident, leading to a decline in the oil recovery factor and a longer duration to reach the maximum recovery factor. Therefore, in field applications, it is essential to consider adjusting the CO2 injection method or using thermosetting plugging agents to achieve superior results.

Climate shifts within major agricultural seasons for +1.5 and +2.0 °C worlds: HAPPI projections and AgMIP modeling scenarios

This study compares climate changes in major agricultural regions and current agricultural seasons associated with global warming of +1.5 or +2.0 °C above pre-industrial conditions. It describes the generation of climate scenarios for agricultural modeling applications conducted as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Coordinated Global and Regional Assessments. Climate scenarios from the Half a degree Additional warming, Projections, Prognosis and Impacts project (HAPPI) are largely consistent with transient scenarios extracted from RCP4.5 simulations of the Coupled Model Intercomparison Project phase 5 (CMIP5). Focusing on food and agricultural systems and top-producing breadbaskets in particular, we distinguish maize, rice, wheat, and soy season changes from global annual mean climate changes. Many agricultural regions warm at a rate that is faster than the global mean surface temperature (including oceans) but slower than the mean land surface temperature, leading to regional warming that exceeds 0.5 °C between the +1.5 and +2.0 °C Worlds. Agricultural growing seasons warm at a pace slightly behind the annual temperature trends in most regions, while precipitation increases slightly ahead of the annual rate. Rice cultivation regions show reduced warming as they are concentrated where monsoon rainfall is projected to intensify, although projections are influenced by Asian aerosol loading in climate mitigation scenarios. Compared to CMIP5, HAPPI slightly underestimates the CO2 concentration that corresponds to the +1.5 °C World but overestimates the CO2 concentration for the +2.0 °C World, which means that HAPPI scenarios may also lead to an overestimate in the beneficial effects of CO2 on crops in the +2.0 °C World. HAPPI enables detailed analysis of the shifting distribution of extreme growing season temperatures and precipitation, highlighting widespread increases in extreme heat seasons and heightened skewness toward hot seasons in the tropics. Shifts in the probability of extreme drought seasons generally tracked median precipitation changes; however, some regions skewed toward drought conditions even where median precipitation changes were small. Together, these findings highlight unique seasonal and agricultural region changes in the +1.5 °C and +2.0 °C worlds for adaptation planning in these climate stabilization targets.

Inorganic carbon physiology underpins macroalgal responses to elevated CO2

Beneficial effects of CO2 on photosynthetic organisms will be a key driver of ecosystem change under ocean acidification. Predicting the responses of macroalgal species to ocean acidification is complex, but we demonstrate that the response of assemblages to elevated CO2 are correlated with inorganic carbon physiology. We assessed abundance patterns and a proxy for CO2:HCO3− use (δ13C values) of macroalgae along a gradient of CO2 at a volcanic seep, and examined how shifts in species abundance at other Mediterranean seeps are related to macroalgal inorganic carbon physiology. Five macroalgal species capable of using both HCO3− and CO2 had greater CO2 use as concentrations increased. These species (and one unable to use HCO3−) increased in abundance with elevated CO2 whereas obligate calcifying species, and non-calcareous macroalgae whose CO2 use did not increase consistently with concentration, declined in abundance. Physiological groupings provide a mechanistic understanding that will aid us in determining which species will benefit from ocean acidification and why.

Short-term interactive effects of ultraviolet radiation, carbon dioxide and nutrient enrichment on phytoplankton in a shallow coastal lagoon

The main goal of this study was to evaluate short-term interactions between increased CO2, UVR and inorganic macronutrients (N, P and Si) on summer phytoplankton assemblages in the Ria Formosa coastal lagoon (SW Iberia), subjected to intense anthropogenic pressures and highly vulnerable to climate change. A multifactorial experiment using 20 different nutrient-enriched microcosms exposed to different spectral and CO2 conditions was designed. Before and after a 24-h in situ incubation, phytoplankton abundance and composition were analysed. Impacts and interactive effects of high CO2, UVR and nutrients varied among different functional groups. Increased UVR had negative effects on diatoms and cyanobacteria and positive effects on cryptophytes, whereas increased CO2 inhibited cyanobacteria but increased cryptophyte growth. A positive synergistic interaction between CO2 and UVR was observed for diatoms; high CO2 counteracted the negative effects of UVR under ambient nutrient concentrations. Nutrient enrichments suppressed the negative effects of high CO2 and UVR on cyanobacteria and diatoms, respectively. Beneficial effects of CO2 were observed for diatoms and cryptophytes under combined additions of nitrate and ammonium, suggesting that growth may be limited by DIC availability when the primary limitation by nitrogen is alleviated. Beneficial effects of high CO2 and UVR in diatoms were also induced or intensified by ammonium additions.

Flavonoids released by carrot (Daucus carota) seedlings stimulate hyphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal CO2 enrichment

Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth ofGigaspora margarita, a vesiculararbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficial effect of CO2 on fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitory (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development ofG. margarita in the presence of optimal CO2 enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two flavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like quercetin and kaempferol are known to have stimulatory effects on hyphal growth ofG. margarita.

Effect of CO₂ enrichment on growth of faba beans at two levels of water supply.

In greenhouse pot trials, Vicia faba was grown at 350 or 700 cmsuperscript 3 CO2/msuperscript 3 from 17 May to 31 Aug. 1982 and water was withheld in early July. CO2 increased photosynthesis and delayed senescence. The beneficial effect of CO2 on growth was maintained during water stress. The effects of additional CO2 and water were multiplicative. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Potential Benefit of CO2 in Oxygen Combustion

Introduction in-situ combustion with oxygen instead of air has high potential for recovering heavy and medium oils. Fig. 1 potential for recovering heavy and medium oils. Fig. 1 illustrates the oxygen combustion process. Among the many advantages is a higher concentration of CO2 ( is greater than 80 %) in the flue gas resulting from the absence of nitrogen. This allows more CO2 dissolution in the oil that helps swell the oil and reduce its viscosity, thus enhancing oil recovery. Although oxygen combustion has been investigated in the laboratory before, the beneficial effect of CO2 has never been demonstrated explicitly. In an attempt to simulate the nitrogen-free environment of oxygen combustion and to study the CO2 effect, we conducted a novel combustion tube run in which a CO2/O2 gas mixture was used in place of air. For comparison, a parallel test was performed that involved use of air at the same operating conditions. Experiment The laboratory apparatus and the experimental procedure have been described previously. A 13.4API [0.9765-g/cm3] California heavy oil and sands from the same reservoir were used. The oil has a viscosity of 6,600 cp [6.66 Pa s] at75F [23.9C] and an atomic H/C ratio of 1.52. The pack properties and operating conditions are listed in Table 1. Both runs were made in the dry combustion mode with about 21 % oxygen in the injection gas. Operations of both tests were smooth and ignition with the CO2/O2 mixture was successful. Results Stabilized combustion was achieved between 2 and 7 hours after ignition for both runs. The burning characteristics averaged over this time period are summarized in Table 1. The reaction temperature, the combustion front velocity, and the product gas composition for both tests were similar, except that the air test had a lower oxygen utilization. The fuel consumptions were practically the same for both runs. This was expected practically the same for both runs. This was expected since the temperature profiles in both runs were nearly identical and the fuel deposition process was largely a function of temperature. The oxygen/fuel ratios were also the same, indicating that the elemental compositions of the fuel were identical. It therefore appeared that substituting N2 in air with CO2 did not change the combustion characteristics for this oil. The oil displacement vs. volume burned is shown in Fig. 2. The fill-in time for the CO2/O2 run was a little longer because of a somewhat higher gas saturation. Once in production, the displacement rates in both runs were almost identical. The injection pressure and pressure drop across the tube are shown in Fig. 3. In pressure drop across the tube are shown in Fig. 3. In both tests, the injection pressure was set at 250 psi [1.7 MPa] by regulating the backpressure. The pressure drop started to increase shortly after ignition, indicating the formation of an oil bank ahead of the thermal front. It reached a maximum at about 2 to 2.5 hours when the oil bank started producing. As seen, the air test had a higher pressure drop that was associated with a bank of oil at the pressure drop that was associated with a bank of oil at the original viscosity, The oil bank in the CO2/O2 run, on the other hand, contained oil at a lower viscosity because of CO2 dissolution. As a result, less pressure drop was required to displace the oil at the same rate. Conclusions The system pressure of the tests was rather low, only 250 psi [1.7 MPa], simulating conditions in a typical psi [1.7 MPa], simulating conditions in atypical California heavy oil reservoir. P. 1137

Effect of CO2 on the germination of conidiospores of Aspergillus niger.

The effect of different concentrations of CO2 on the germination of conidiospores of Aspergillus niger A 5 has been studied using Pardee's buffer mixtures which maintain constant CO2 tensions. The beneficial effect of CO2 on germination is maximum at 0.5% CO2 concentration, when 70–90% of the spores germinate within 6 hours, whereas in controls with air containing 0.03% CO2 there is only 15–20% germination at 6 hours. At higher CO2 concentrations this beneficial effect of CO2 on germination diminishes and at 3% there is a complete inhibition of spore germination.