A Theoretical Investigation of Oxidation Efficiency of a Volatile Removal Assembly Reactor Under Microgravity Conditions

Volatile Removal Assembly (VRA) is a subsystem of the Closed Environment Life Support System (CELSS) installed in the International Space Station. It is used for removing contaminants (volatile organics) in the wastewater produced by the space station crews. The major contaminants are formic acid, ethanol, and propylene glycol. The VRA contains a slim packbed reactor (3.5 cm diameter and four 28 cm long tubes in series) to perform catalyst oxidation of wastewater at elevated pressure and temperature under microgravity conditions. In the reactor, the contaminants are burned with oxygen gas (O2) to form water and carbon dioxide (CO2) that dissolves in the water stream. Optimal design of the reactor requires a thorough understanding about how the reactor performs under microgravity conditions. The objective of this study was to develop a mathematical model to interpret experimental data obtained from normal and microgravity conditions, and to predict the performance of VRA reactor under microgravity conditions. Catalyst oxidation kinetics and the total oxygen-water contact area control the efficiency of catalyst oxidation for mass transfer, which depends on oxygen gas holdup and distribution in the reactor. The process involves bubbly flow in porous media with chemical reactions in microgravity environment. This presents a unique problem in fluid dynamics that has not been studied. Guo et al. (2004) developed a mathematical model that predicts oxygen holdup in the VRA reactor. No mathematical model has been found in the literature that can be used to predict the efficiency of catalyst oxidation under microgravity conditions

A Computer Model for Analyzing Volatile Removal Assembly

A computer model simulates reactional gas/liquid two-phase flow processes in porous media. A typical process is the oxygen/wastewater flow in the Volatile Removal Assembly (VRA) in the Closed Environment Life Support System (CELSS) installed in the International Space Station (ISS). The volatile organics in the wastewater are combusted by oxygen gas to form clean water and carbon dioxide, which is solved in the water phase. The model predicts the oxygen gas concentration profile in the reactor, which is an indicator of reactor performance. In this innovation, a mathematical model is included in the computer model for calculating the mass transfer from the gas phase to the liquid phase. The amount of mass transfer depends on several factors, including gas-phase concentration, distribution, and reaction rate. For a given reactor dimension, these factors depend on pressure and temperature in the reactor and composition and flow rate of the influent

Theoretical assessment of CO2 injection into low-temperature water zones for non-leaking storage in hydrate form

Concerns exist about CO2 leaks from conventional supercritical CO2 storage reservoirs. This study investigates injecting CO2 into low-temperature offshore reservoirs to lock it in a solid state, thus preventing potential leaks. An analytical model was developed to predict CO2 injectivity into frac-packed injection wells in these low-temperature reservoirs. While the initial transient flow model was complex with Bessel functions and exponential integral, it was further simplified for practical field application. Sensitivity analysis of the model reveals that injectivity is less sensitive to reservoir permeability but more sensitive to fracture conductivity. The analytical model suggests injectivity is directly proportional to fracture width and fracture permeability. The case study utilizing field data from the South China Sea indicates feasible injection rates ranging from 6 to 17 tons/day depending on fracture conductivity. This work provides an analytical tool to predict injectivity for CO2 storage in frac-packed low-temperature offshore reservoirs, contributing to carbon reduction and neutralization goals.Document Type: Short communicationCited as: Guo, B., Zhang, P. Theoretical assessment of CO2 injection into low-temperature water zones for non-leaking storage in hydrate form. Advances in Geo-Energy Research, 2023, 10(1): 1-6. https://doi.org/10.46690/ager.2023.10.0

Factors affecting the fluid temperature of geothermal energy wells converted from abandoned oil and gas wells

The transition from fossil energy to clean energy is an ongoing trend. Because geothermal energy is buried beneath oil and gas wells, it is desirable to convert abandoned oil and gas wells to geothermal energy wells. The candidate wells can be dry holes in oil and gas exploration or end-of-life oil and gas wells in depleted oil and gas reservoirs. There is a knowledge gap to fill between the oil and gas wells and geothermal wells in the well conversion engineering, that is, factors affecting the performance of the geothermal wells are not fully understood. This work investigated the factors affecting the temperature of produced water of geothermal energy wells converted from abandoned oil and gas wells. Both vertical and horizontal well options were considered. The result of the field case study using the data for a well in the Songliao Basin of Northeastern China shows that, without pipe insulation, the temperature of the returned water is very close to that of the injected water, regardless of vertical or horizontal wells. With pipe insulation, the temperature of the returned water in the horizontal well is higher than that in the vertical well. The temperature of the returned water declines quickly as the thermal conductivity of pipe insulation increases in the low-thermal conductivity region. The temperature of the returned water in horizontal wells is affected by the horizontal hole section length for heat transfer. But this effect levels off after about 1,000 m of horizontal hole section is reached, meaning that 1,000 m of horizontal hole section is adequate for heat transfer from the geothermal zone to the injected water. This paper provides an analytical method for the technical feasibility assessment of converting abandoned oil and gas wells to geothermal energy wells.Document Type: Original articleCited as: Zhang, P., Guo, B. Factors affecting the fluid temperature of geothermal energy wells converted from abandoned oil and gas wells. Advances in Geo-Energy Research, 2023, 9(1): 5-12. https://doi.org/10.46690/ager.2023.07.0

Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method

Natural gas production from marine gas hydrate reservoirs has become attractive to the oil and gas industry in recent years. It is still a great challenge to recover natural gas from hydrate reservoirs efficiently mainly due to sand production and wellbore collapse problems associated with the production scheme of depressurization. The thermal recovery method has not been proven economical due to the high cost of energy consumption. This study focuses on using geothermal energy to assist the depressurization process so that well pressure drawdown can be reduced and thus sand production and wellbore collapse problems can be mitigated. The authors investigated the transfer of heat energy from a natural geothermal zone to a marine gas hydrate reservoir and its effect on gas well productivity using analytical models. The result of our investigation shows that the initial well productivity can be significantly improved using geothermal energy more than 10-fold. This work provides engineers with an analytical tool for the feasibility analysis of using geothermal energy to improve well performance in gas hydrate reservoirs.Cited as: Mahmood, M. N., Guo, B. Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method. Advances in Geo-Energy Research, 2023, 7(2): 90-98. https://doi.org/10.46690/ager.2023.02.0

New Development of Air and Gas Drilling Technology

Gas drilling technology has been widely promoted and applied in recent years. Known for being capable of discovering and protecting reservoirs, improving the penetration rate and avoiding loss circulation, two key issues of gas drilling still need to be addressed. First, a more accurate way of determining the gas injection rate is needful. In this text, we present a modified mathematical model for predicting the optimum range of gas injection rate required to balance the borehole cleaning and well-integrity issues. The optimum gas injection rate should be sought between the minimum value required for hole cleaning and the maximum permissible value to avoid hole erosion. Good consistency between the model prediction and field problem-free nitrogen gas injection rate indicates the reliability of the proposed model. Second, the problem of environmental pollution and wasting of resources caused by direct discharging or combustion of the returned gas is to be solved. To address the latter issue, we introduce a new technology of gas recycling system (GRS). Our research group has carried out a comprehensive investigation, including integration design, technological process, cuttings transport analysis, separation and filter equipment selection, and control system design. The feasibility of GRS has been verified through an open-loop pilot test

An assessment of methane gas production from natural gas hydrates: Challenges, technology and market outlook

Natural gas hydrates are enormous energy resources occurring in the permafrost and under deep ocean sediments. However, the commercial or sustained production of this resource with currently available technology remains a technical, environmental, and economic challenge, albeit a few production tests have been conducted to date. One of the major challenges has been sand production due to the unconsolidated nature of hydrate bearing formations. This review presents progress in methane gas production from natural gas hydrate deposits, specifically addressing the technology, field production and simulation tests, challenges, and the market outlook. Amongst the production techniques, the depressurization method of dissociating natural gas hydrates is widely accepted as the most feasible option and it has been used the most in field test trials and simulation studies. The market for natural gas hydrates looks promising considering the increasing demand for energy globally, limited availability of conventional fossil fuels, and the low carbon footprint when using natural gas compared to liquid and solid fossil fuels. The major market setback currently is cheap gas from shale and conventional oil and gas reservoirs.Cited as: Shaibu, R., Sambo, C., Guo, B., Dudun, A. An assessment of methane gas production from natural gas hydrates: Challenges, technology and market outlook. Advances in Geo-Energy Research, 2021, 5(3): 318-332, doi: 10.46690/ager.2021.03.0

Improved Efficiency of Miscible C02 Floods and Enhanced Prospects for C02 Flooding Heterogeneous Reservoirs

The PRRC-modified DOE pseudomiscible reservoir simulator MASTER was used to conduct a systematic investigation of CO2 flooding using horizontal wells in conjunction with foam. We evaluated the effects of horizontal well radius, length, and location on oil recovery through our testing. This work is necessary to provide field predictions for the use of foam and/or horizontal wells. A number of coreflood tests were performed to examine the effect of foam on oil recovery in heterogeneous porous media. Two coaxial composite cores were used to simulate layered formation systems. The first, an isolated coaxial composite core, was used to simulate a layered formation system of which the layers were not in communication. The second, in capillary contact, simulated layers in communication. Preliminary results suggest that oil displacement is more efficient when surfactant solution is used with CO2 to form CO2-foam. Results from both systems indicate the potential of using foam for improving oil recovery in heterogeneous porous media. Since injectivity loss is a problem in a number of gas injection projects, a preliminary investigation of injectivity loss in WAG was performed. A number of tests were carried out to investigate injectivity loss, indicating that for a given rock the injectivity loss depends on oil saturation in the core during WAG flooding. Higher loss was found in cores with high in-situ oil saturations. No injectivity loss was observed with the naturally fractured carbonate core

Improved Efficiency of Miscible C02 Floods and Enhanced Prospects for C02 Flooding Heterogeneous Reservoirs

The PRRC-modified DOE pseudomiscible reservoir simulator MASTER was used to conduct a systematic investigation of CO2 flooding using horizontal wells in conjunction with foam. We evaluated the effects of horizontal well radius, length, and location on oil recovery through our testing. This work is necessary to provide field predictions for the use of foam and/or horizontal wells. A number of coreflood tests were performed to examine the effect of foam on oil recovery in heterogeneous porous media. Two coaxial composite cores were used to simulate layered formation systems. The first, an isolated coaxial composite core, was used to simulate a layered formation system of which the layers were not in communication. The second, in capillary contact, simulated layers in communication. Preliminary results suggest that oil displacement is more efficient when surfactant solution is used with CO2 to form CO2-foam. Results from both systems indicate the potential of using foam for improving oil recovery in heterogeneous porous media. Since injectivity loss is a problem in a number of gas injection projects, a preliminary investigation of injectivity loss in WAG was performed. A number of tests were carried out to investigate injectivity loss, indicating that for a given rock the injectivity loss depends on oil saturation in the core during WAG flooding. Higher loss was found in cores with high in-situ oil saturations. No injectivity loss was observed with the naturally fractured carbonate core