Abstract: The Japanese consortium to enhance CO2-ECBM carried out a pilot project on CO2 injection during 2002 to 2007 at Yubari, Hokkaido, Japan. However, supercriticalCO2 could not be obtained because of heat loss along the deep injection tubing. The absolute pressure and CO2 temperature at the bottom hole was approximately 15.5MPa and 28°C, respectively. Therefore, it can be assumed that CO2 was injected into the coal seam in its liquid phase. Liquid CO2 is less permeable in the coal seam because of its high viscosity and the resultant swelling of the coal matrix.
This study provides a numerical system to predict CO2 flow characteristics of pressure, temperature, supercritical or liquid by considering heat transfer from the injector into surrounding casings and strata. This study focused on keeping supercritical CO2 in the tubing because the viscosity of supercritical CO2 is 40% less than that of liquid CO2. The CO2 temperature required to keep CO2 in its supercritical condition from the surface to the bottom was successfully predicted for various CO2 injection rates and electric heating powers.
Finally, injected CO2 is expected to be supercritical at an injection rate of over 12ton/day without any heating.
Abstract: In this study, we investigate a system of gas production from methane hydrate layers involving hot water injection using dual horizontal wells. Physical and numerical models simulating the gas production process from methane hydrate layers within a hot water chamber are proposed.
Experiments with scaled two-dimensional physical models using an imitated hydrate layer (NaHCO3 ice formation) were performed to investigate fluid flow characteristics and production performance. The thermal simulator was used to simulate experimental chamber growth and field production. Numerical simulations for the processes were successfully performed with a two-component (water and oil or methane hydrates), three-phase (water, methane hydrates and methane gas) and three-dimensional model, matching the physical model. Results of the history-matched numerical simulations were in good agreement with data on production and chamber shapes obtained using the Intermediate3-Stone1 wettability model. Simulations of field production using dual horizontal wells 500 m in length were performed to evaluate cumulative gas production over three years of injection with 500×103 kg/day of hot water, which varied from 5×106 to 9×106 std m3. The production process appears economical, in view of the expected convective heat transfer from the chamber boundary and buoyancy force on dissociated methane gas.
Abstract: Coal-fired power plants produce flue gas consisting mainly of nitrogen (around 79%), followed by CO2 (around 10 – 15%), and small amounts of other gases such as H2, NOx and SO2. One of the promising methods for reducing CO2 emission is CO2 sequestration
into deep, unminable coal seams. At present, flue gases exhausted from coal-fired plant must be separated to extract pure CO2 before injecting it into coal seams.
In order to enhance the efficiency of carbon capture and storage (CCS) from a coal-fired power plant, oxy-fuel combustion
technology has been employed. This technology uses pure oxygen to burn the coal, and consequently CO2 concentration in the flue gas is theoretically increased up to 95%.
This study aims to simulate the CH4 replacement mechanism in coal by using pure CO2 and a synthesized flue gas (99% CO2 and 1% SO2) that is similar to the emission gas from the coal-fired power plants. A measurement procedure for gas adsorption is employed which, after establishing methane adsorption equilibrium
of the coal samples, injects pure CO2 or the synthesized flue gas into an adsorption cell in order to investigate CH4 replacement
properties. Coal samples used for the present experiments were taken from the coal seams of Vietnam, Japan, Australia, China and Indonesia. The samples were crushed to particle sizes ranging from 250 μm to 5 mm. The concentration of gases was taken from the adsorption cell and analyzed by using a gas chromatograph.
Adsorption isotherms of CH4, CO2 and SO2 were measured by using the volumetric method apparatus.
This paper discusses the characteristics of methane replacement
by using pure CO2, the synthesized flue gas and the effect of SO2 on adsorption properties of coal.
Abstract: For complex petroleum recovery processes, experimental investigation is usually performed with numerical simulation to study the recovery mechanism(s). In this paper, both physical and numerical simulation of the steam-assisted gravity drainage (SAGD) process were performed. One of the objectives of the numerical investigation was to determine the match between numerical results with data
Abstract: Experiments on initial stages of the steam-assisted gravity drainage (SAGD) process were carried out using two-dimensional scaled reservoir models to investigate production process and performance. The rising or growing process of the initial steam chamber, its shape and area, and temperature distributions were visualized using video and thermal-video pictures. The relationship between isothermal lines and chamber interface was investigated to study the drainage mechanism. The temperature at the interface where the chamber was expanding remained nearly constant at 80 ï‚°C. The effect on oil recovery of vertical spacing between the two horizontal wells was also investigated. For the case of conventional SAGD, oil production rate increased with increasing vertical well spacing; however, the lead time for the gravity drainage to initiate oil production became longer. The results suggest that L can be used as a governing factor to evaluate production rate and lead time in the initial stage of the SAGD process. Based on these experimental results, the SAGD process was modified by adding intermittent steam injection from the lower production well to the continuous steam injection from the upper well (named SAGD-ISSLW). Using the modified process, the time to generate near break-through condition between two wells was shortened, and oil production was enhanced at the rising chamber stage compared with that of the conventional SAGD process.
