Yuichi Sugai

Gas Production System From Methane Hydrate Layers by Hot Water Injection Using Dual Horizontal Wells

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 (NaHCO 3 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-Stonel wettability model. Simulations of field production using dual horizontal wells 500 m in length were performed to evaluate cumulative gas production over 3 years of injection with 500 x 10 3 kg/day of hot water, which varied from 5 x 10 6 to 9 x 10 6 std m 3 . The production process appears economical, in view of the expected convective heat transfer from the chamber boundary and buoyancy force on dissociated methane gas.

Chapter 15 Biotechnological approach for development of microbial enhanced oil recovery technique

Publisher Summary This chapter discusses microbial enhanced oil recovery (MEOR) as MEOR is one of the techniques expected to be both economically feasible and environmental friendly, while also considerably increasing oil production. The chapter also discusses the types of MEOR processes and the present stage of MEOR. Biotechnological tools for estimating the behavior of indigenous microbes in the reservoir, as well as injected microbes, were successfully developed. In the chapter, valuable data to demonstrate the MEOR effect were successfully collected, and the results obtained from this research support the theory that MEOR can effectively increase oil recovery. Though the results are seen in only a few cases yet at most, it is believed that this is an example of a successful application of MEOR to a broad range of reservoirs.

CO2 Temperature Prediction in Injection Tubing Considering Supercritical Condition at Yubari ECBM Pilot-Test

The Japanese consortium for CO 2 -Enhanced Coal Bed Methane (ECBM) carried out a pilot project on CO 2 injection from 2002 to 2007 in the city ofYubari, Hokkaido, Japan. However, supercritical CO 2 could not be obtained because of low CO 2 injectivity and heat loss along the deep injection tubing. The absolute pressure and CO 2 temperature at the bottomhole was approximately 15.5 MPa and 28°C, respectively. Therefore, it can be assumed that CO 2 was injected into the coal seam in its liquid phase. Liquid CO 2 is less permeable in the coal seam because of its high viscosity and the resultant swelling of the coal matrix to decrease permeability. This study provides a numerical system to predict CO 2 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 CO 2 in the tubing because the viscosity of supercritical CO 2 is 40% less than that of liquid CO 2 . The CO 2 temperature required to keep CO 2 in its supercritical condition from the surface to the bottom was successfully predicted for various CO 2 injection rates and electric heating powers. Finally, injected CO 2 is expected to be supercritical at an injection rate of over 12 ton/d without any heating.

Modeling microbial-induced oil viscosity reduction: Effect of temperature, salinity and nutrient concentration

ABSTRACT 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.

Physicochemical and microemulsion properties of dimeric quaternary ammonium salts with trimethylene spacer for enhanced oil recovery

Dimeric surfactants, also termed as Gemini surfactants, are regarded as organic materials which have two hydrophilic head groups and two hydrophobic groups in the molecules linked together with a spacer. In this study, dimeric surfactants of quaternary ammonium bromide connected with a trimethylene spacer group (m-3-m) have been investigated as potential micellar solutions for enhanced oil recovery. Static surface tension, interfacial tension as well as optimal salinity characterized their physicochemical and microemulsion properties. Using modeled petroleum fluids, the critical micelle concentration (CMC) was found dependent not only of the chemical architecture of the surfactant but also of the composition in the liquid phase. The nature and/or the length of spacer group participates significantly to the spatial rearrangement of the dimeric surfactants which subsequently altered the surface properties. For the same spacer group, an ultralow interfacial tension was achieved. Encouraging oil solubilization was found for surfactants used with an effect pronounced for longer alkyl chain. Furthermore, both the effects and the presence of metallic divalent ions on the phase behavior were discussed.

Consideration of an effect of interfacial area between oil and CO2 on oil swelling

Oil swelling is an important phenomenon in CO2-EOR. According to various studies in the past, the degree of oil swelling depends on the partial pressure of CO2, temperature, and oil composition. However, we expect that other factors, such as oil saturation, capillary pressure, and grain size of reservoir rock must be also considered in evaluating oil swelling because they may influence the interfacial area between oil and CO2, which affects the dissolubility of CO2 in oil. Therefore, we had made clear the effect of the interfacial area on oil swelling in this study. Oil and CO2 were injected into a small see-through windowed high-pressure cell and oil swelling was observed under a microscope. The swelling factor increased with the increase of the specific interfacial area between oil and CO2. Moreover, oil swelling in porous media was observed using micro-models which had been made of two different diameter glass beads. Swelling factor in fine beads micro-model became larger than that in coarse beads micro-model whose interfacial area between oil and CO2 was smaller than that of fine beads micro-model. Therefore, the swelling factor is expected to be larger with an increase in the interfacial area in porous media. These results suggest that the oil swelling should be expressed as a function of oil saturation, capillary pressure, and grain size of reservoir rock which are related to the interfacial area as well as the partial pressure of CO2, temperature, and oil composition.

A Study on Preventing Spontaneous Combustion of Residual Coal in a Coal Mine Goaf

The effectiveness of grouting scheme has been simulated to prevent the coal spontaneous combustion at a goaf in Haizi Colliery, China. The colliery has been operated for long period over 27 years and has a complex ventilation network including airflow leakages which could possibly lead to the spontaneous combustion of coal at goafs. Firstly, the mine ventilation simulator MIVENA was used to analyze the mine ventilation network airflows to control airflows in and out of working faces and goafs. As the second approach, numerical simulations were carried by the simulator FLUENT in order to predict spontaneous combustion of residual coal with leakage flow in the #3205 goaf. It was cleared that the goaf can be divided into three zones based on oxygen concentration in the goaf area. Finally, the numerical simulation results show that the slurry grouting method is able to be an effective and economical method by reducing porosity in the goaf area to prevent spontaneous combustion of residual coal.

Analysis of Heavy Oil Emulsion-Carbon Dioxide System on Oil-Swelling Factor and Interfacial Tension by Using Pendant Drop Method for Enhanced Oil Recovery and Carbon Dioxide Storage

 Abstract—Heavy oil becomes more interest owing to oil prices and the huge amount of reserves. Steam injection is a common method for heavy-oil production with emulsion formation. Also carbon dioxide injection is applied for viscosity and interfacial tension reduction. CO2 becomes more important because of environmental concerns. CO2 storage in reservoirs like depleted oil wells becomes widespread. Hence, understanding the behavior of CO2 when it encounters emulsive heavy-oil is critical. In this work, the interfacial tension and oil-swelling factors of CO2 in oil and its emulsions are measured at 296 K and pressure from 0.5 to 1.5 MPa with water/oil ratio from 0.00 to 12.27 percent compared to original oil. The results show that the interfacial tension decreases at higher pressure ranging from 3.7 to 16.8 percent and water content from 10.3 to 22.6 percent. Furthermore, oil-swelling factors increase with pressure and water content up to 1.9 percent and 8.0 percent, respectively. These results are explained by absorption processes in that high pressure can serve as high driving force for CO2 solubility.

Measurements of Gasification Characteristics of Coal and Char in CO2-Rich Gas Flow by TG-DTA

Pyrolysis, combustion, and gasification properties of pulverized coal and char in CO2-rich gas flow were investigated by using gravimetric-differential thermal analysis (TG-DTA) with changing O2%, heating temperature gradient, and flow rate of CO2-rich gases provided. Together with TG-DTA, flue gas generated from the heated coal, such as CO, CO2, and hydrocarbons (HCs), was analyzed simultaneously on the heating process. The optimum O2% in CO2-rich gas for combustion and gasification of coal or char was discussed by analyzing flue gas with changing O2 from 0 to 5%. The experimental results indicate that O2% has an especially large effect on carbon oxidation at temperature less than 1100°C, and lower O2 concentration promotes gasification reaction by producing CO gas over 1100°C in temperature. The TG-DTA results with gas analyses have presented basic reference data that show the effects of O2 concentration and heating rate on coal physical and chemical behaviors for the expected technologies on coal gasification in CO2-rich gas and oxygen combustion and underground coal gasification.

Properties and Developments of Combustion and Gasification of Coal and Char in a CO2-Rich and Recycled Flue Gases Atmosphere by Rapid Heating

Combustion and gasification properties of pulverized coal and char have been investigated experimentally under the conditions of high temperature gradient of order 200°C·s−1 by a CO2 gas laser beam and CO2-rich atmospheres with 5% and 10% O2. The laser heating makes a more ideal experimental condition compared with previous studies with a TG-DTA, because it is able to minimize effects of coal oxidation and combustion by rapid heating process like radiative heat transfer condition. The experimental results indicated that coal weight reduction ratio to gases followed the Arrhenius equation with increasing coal temperature; further which were increased around 5% with adding H2O in CO2-rich atmosphere. In addition, coal-water mixtures with different water/coal mass ratio were used in order to investigate roles of water vapor in the process of coal gasification and combustion. Furthermore, char-water mixtures with different water/char mass ratio were also measured in order to discuss the generation ratio of CO/CO2, and specified that the source of Hydrocarbons is volatile matter from coal. Moreover, it was confirmed that generations of CO and Hydrocarbons gases are mainly dependent on coal temperature and O2 concentration, and they are stimulated at temperature over 1000°C in the CO2-rich atmosphere.