Residual Gas Trapping Research Articles

Site characterisation of a basin-scale CO2 geological storage system: Gippsland Basin, southeast Australia

Geological storage of CO2 in the offshore Gippsland Basin, Australia, is being investigated by the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) as a possible method for storing the very large volumes of CO2 emissions from the nearby Latrobe Valley area. A storage capacity of about 50 million tonnes of CO2 per annum for a 40-year injection period is required, which will necessitate several individual storage sites to be used both sequentially and simultaneously, but timed such that existing hydrocarbon assets will not be compromised. Detailed characterisation focussed on the Kingfish Field area as the first site to be potentially used, in the anticipation that this oil field will be depleted within the period 2015–2025. The potential injection targets are the interbedded sandstones of the Paleocene-Eocene upper Latrobe Group, regionally sealed by the Lakes Entrance Formation. The research identified several features to the offshore Gippsland Basin that make it particularly favourable for CO2 storage. These include: a complex stratigraphic architecture that provides baffles which slow vertical migration and increase residual gas trapping and dissolution; non-reactive reservoir units that have high injectivity; a thin, suitably reactive, lower permeability marginal reservoir just below the regional seal providing mineral trapping; several depleted oil fields that provide storage capacity coupled with a transient production-induced flow regime that enhances containment; and long migration pathways beneath a competent regional seal. This study has shown that the Gippsland Basin has sufficient capacity to store very large volumes of CO2. It may provide a solution to the problem of substantially reducing greenhouse gas emissions from future coal developments in the Latrobe Valley.

Effect of water blending on bioethanol HCCI combustion with forced induction and residual gas trapping

Abstract There is increased interest worldwide in renewable engine fuels as well as in new combustion technologies. Bioethanol is one of the alternative fuels that have been used successfully in spark ignition engines. A combustion technology that currently attracts a lot of interest is the homogeneous charge compression ignition (HCCI) combustion, which has shown potential for low nitrogen oxides emissions with no particulate matter formation. The authors have shown previously that applying forced induction to bioethanol HCCI with residual gas trapping results in an extended load range compared to naturally aspirated operation. However, at high boost pressures, high cylinder pressure rise rates develop. Work by other researchers has shown that direct injection of water can be used as a combustion control method. The present work explores water blending as a way that might have an effect on combustion in order to lower the maximum pressure rise rates and further improve emissions. The obtained experimental results show that in contrast to variable rate direct injection of water, fixed rate water–ethanol blending is counterproductive for the reduction of pressure rise rates at higher loads. In addition, increasing the water content in ethanol results in reduction of the effective load range and increased emissions.

Effect of inlet valve timing and water blending on bioethanol HCCI combustion using forced induction and residual gas trapping

It has been shown previously that applying forced induction to homogeneous charge compression ignition (HCCI) combustion of bioethanol with residual gas trapping, results in a greatly extended engine load range compared to normal aspiration operation. However, at very high boost pressures, very high cylinder pressure rise rates develop. The approach documented here explores two ways that might have an effect on combustion in order to lower the maximum pressure rise rates and further improve the emissions of oxides of nitrogen (NO x ); inlet valve timing and water blending. It was found that there is an optimal inlet valve timing. When the timing was significantly advanced or retarded away from the optimal, the combustion phasing could be retarded for a given lambda (excess air ratio). However, this would result in higher loads and lower lambdas for a given boost pressure, with possibly higher NO x emissions. Increasing the water content in ethanol gave similar results as the non-optimal inlet valve timing.

0540 溶解および残留ガストラップに基づいたCO_2地下貯留に関する研究(S52-2 温室効果ガス排出抑制技術(2),S52 温室効果ガス排出抑制技術)

0540 溶解および残留ガストラップに基づいたCO_2地下貯留に関する研究(S52-2 温室効果ガス排出抑制技術(2),S52 温室効果ガス排出抑制技術)

Heterogeneous saline formations for carbon dioxide disposal: Impact of varying heterogeneity on containment and trapping

Natural gas fields often contain carbon dioxide in their reservoir fluids. Exploitation of these resources requires the removal of carbon dioxide from produced fluids to meet quality standards for sale into a domestic market or for the processing of the gas into LNG. To limit the atmospheric emissions of carbon dioxide, a major greenhouse gas, it has been proposed that one method of abatement could be to inject the CO 2 into deep saline formations. This study shows that the selection process for identifying appropriate saline formations should not only consider their size and permeability but should also consider their degree of heterogeneity. To this end, notional yet realistic geological marine sand models were constructed, on an areal scale of 50 km 2, to examine the effects of reservoir heterogeneity on the migration and storage of a 50 million tonne plume over a time scale of 1000 yrs. The models were identical in geometry and in their distribution of porosity and permeability but were individually populated with facies realisations for different net-to-gross ratios. Standard geostatistical techniques were used to generate the various distributions. With regard to the shale content, the ratio of sand to shale was varied from 100:0 (i.e. homogeneous) to 40:60. A radial shale variogram, with a length of 300 m, was used. The models were up-scaled, using flow-based methods, to make the computation feasible. A set of metrics were developed and used to compare plume migration (both vertically and laterally) and containment (through dissolution and residual phase trapping) between the various scenarios. The study showed that heterogeneity had a significant impact on the subsurface behaviour of the carbon dioxide. Increasing the shale content, corresponding to a gradual decrease in reservoir quality, progressively inhibited vertical flow of the plume whilst promoting its lateral flow. This increase in the tortuosity of the carbon dioxide migration pathways resulted in a reduction in the rate of residual gas trapping through hysteresis effects. Ultimately, however, less carbon dioxide is likely to collect under the seal, thereby reducing the risk of seepage to overlying formations. It is evident that for the time scales of containment being considered here simulation periods of the order of tens of thousands of years, or even longer, will be required to demonstrate the onset of an equilibrium state.

Assessment of a potential storage site for carbon dioxide: A case study, southeast Queensland, Australia

Australia's coal-fired power plants produce about 70% of the nation's total installed electricity generation capacity and emit about 190 million t of CO2/yr, of which about 44 million t come from central and southeast Queensland. A multidisciplinary study has identified the onshore Bowen Basin as having potential for geological storage of CO2. Storage potential has been documented within a 295-km2 (113-mi2) area on the eastern flank of the Wunger Ridge using a simplified regional three-dimensional model and is based on estimating injection rates of 1.2 million t CO2/yr for 25 yr. Paleogeographic interpretations of the Showgrounds Sandstone reservoir in the targeted injection area indicate a dominantly meandering-channel system that grades downdip into a deltaic system. Seismic interpretation indicates a relatively unfaulted seal and reservoir section. The depth to the reservoir extends to 2700 m (8858 ft). CO2 injection simulations indicate that at least one horizontal or two vertical wells would be required to inject at the proposed rate into homogeneous reservoirs with a thickness of approximately 5 m (16 ft) and permeability of 1 d. The existence of intrareservoir shale baffles necessitates additional wells to maintain the necessary injection rate; this is also true for medium-permeability reservoirs. The long-term storage of the injected CO2 involves either stratigraphic and residual gas trapping along a 10–15-km (6–9-mi) migration path and, ultimately, potentially, within updip depleted hydrocarbon fields or trapping in medium-permeability rocks. Trapping success will be a function of optimal reservoir characteristics and the distribution of seals and baffles. This optimization may target specific, as-yet to be determined, permeability ranges.

GIPPSLAND BASIN GEOSEQUESTRATION: A POTENTIAL SOLUTION FOR THE LATROBE VALLEY BROWN COAL CO2 EMISSIONS

Geosequestration of CO2 in the offshore Gippsland Basin is being investigated by the CO2CRC as a possible method for storing the very large volumes of CO2 emissions from the Latrobe Valley area. A storage capacity of about 50 million tonnes of CO2 per year for a 40-year injection period is required, which will necessitate several individual storage sites to be used both sequentially and simultaneously, but timed such that existing hydrocarbon assets are not compromised. Detailed characterisation focussed on the Kingfish Field area as the first site to be potentially used, in the anticipation that this oil field will be depleted within the period 2015–25. The potential injection targets are the interbedded sandstones, shales and coals of the Paleocene-Eocene upper Latrobe Group, regionally sealed by the Lakes Entrance Formation. The research identified several features to the offshore Gippsland Basin that make it particularly favourable for CO2 storage. These include: a complex stratigraphic architecture that provides baffles which slow vertical migration and increase residual gas trapping; non-reactive reservoir units that have high injectivity; a thin, suitably reactive, low permeability marginal reservoir just below the regional seal providing additional mineral trapping; several depleted oil fields that provide storage capacity coupled with a transient flow regime arising from production that enhances containment; and, long migration pathways beneath a competent regional seal. This study has shown that the Gippsland Basin has sufficient capacity to store very large volumes of CO2. It may provide a solution to the problem of substantially reducing greenhouse gas emissions from the use of new coal developments in the Latrobe Valley.

4318 CO_2地下貯留における溶解・残留ガストラップに関する研究(S59-2 温室効果ガス排出抑制技術(2),S59 温室効果ガス排出抑制技術)

4318 CO_2地下貯留における溶解・残留ガストラップに関する研究(S59-2 温室効果ガス排出抑制技術(2),S59 温室効果ガス排出抑制技術)

AN EXPERIMENTAL STUDY OF BIOETHANOL HCCI

ABSTRACT Bioethanol has been successfully used in conventional spark ignition (SI) internal combustion engines. Homogeneous charge compression ignition (HCCI) combustion, a novel combustion method, has shown the potential for low nitric oxides (NOx) emissions with no particulate matter formation. This paper explores two different approaches to achieve HCCI with bioethanol; namely, trapping of internal residual gas and intake temperature heating with a high compression ratio. For naturally aspirated HCCI operation with residual gas trapping on a spark ignition engine, although the NOx emissions were low, the load range was unacceptably small. When inlet manifold pressurisation was employed, a substantial increase in the upper load boundary could be achieved without any substantial increase in NOx emissions. With forced induction, the feasibility of using boost control as the main method of load control for higher engine loads during HCCI operation has been explored with possible methods of utilizing boost control. One possible strategy is a map based strategy where fuelling rates are correlated versus boost pressure and trapped residual amounts. A proof of concept using this strategy showed that transient operation from a low load to a much higher load, using boost control might be possible without engine misfire.

Applying Forced Induction to Bioethanol HCCI Operation with Residual Gas Trapping

With increasing interest in renewable fuels, bioethanol has been successfully used in conventional internal combustion engines. Its application in naturally aspirated homogeneous charge compression ignition (HCCI) engines, however, has shown a much reduced usable load range. The approach documented here applies forced induction to bioethanol HCCI operation on a gasoline type engine, in conjunction with residual gas trapping. This retains the much reduced external heating benefits associated with residual gas trapping. In the present work, the achievable engine load range is controlled by boost pressure, excess air ratio, and trapped residual gas amounts. A substantial increase in load range can be achieved, up to 7.5 bar indicated mean effective pressure (IMEP), while keeping NOx emissions up to 2 orders of magnitude lower than spark ignition (SI) operation. There is, however, a possible fuel penalty of up to 11% at the maximum achievable load.

An investigation into propane homogeneous charge compression ignition (HCCI) engine operation with residual gas trapping

Propane is available commercially for use in conventional internal combustion engines as an alternative fuel for gasoline. However, its application in the developing homogeneous charge compression ignition (HCCI) engines requires various approaches such as high compression ratios and/or inlet charge heating to achieve auto ignition. The approach documented here utilizes the trapping of internal residual gas (as used before in gasoline controlled auto ignition engines), to lower the thermal requirements for the auto ignition process. In the present work, with a moderate engine compression ratio the achievable engine load range was controlled by the degree of internal trapping of exhaust gas supplemented by inlet charge heating. Increasing the compression ratio decreased the inlet temperature requirements; however, it also resulted in higher pressure rise rates. Varying the inlet valve timing affects the combustion phasing which can help to decrease the maximum pressure rise rates. NOx emissions were characteristically low due to the nature of homogeneous combustion.

An Investigation into Bioethanol Homogeneous Charge Compression Ignition (HCCI) Engine Operation with Residual Gas Trapping

Given the increasing interest in renewable fuels, bioethanol has been successfully used in conventional internal combustion engines. However, its application in homogeneous charge compression ignition (HCCI) engines requires various approaches, such as high compression ratios and/or intake charge heating, to achieve auto ignition. The approach documented here utilizes the trapping of internal residual gas (as used previously in gasoline-fueled controlled auto ignition engines) to lower the thermal requirements for the auto ignition process. In the present work, the achievable engine load range is controlled by the degree of internal trapping of exhaust gas, supplemented by moderate intake charge heating. Moderate intake heating extends the narrow auto ignition load window while varying the inlet valve timing extends the upper load range. Nitrogen oxide (NOx) emissions are characteristically low, because of the nature of homogeneous combustion.

Compression Ratio Effect on Methane HCCI Combustion

We have used the HCT (hydrodynamics, chemistry, and transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, burn duration, NOx, production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. intake pressure) with 14:1, 16:1 and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation, which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either two-stroke or four-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50 percent and NOx levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.