Experimental study on fracturing of coal body by cyclic injection of liquid nitrogen under in situ stress simulation

Liquid nitrogen is a vital medium during the extinguishing and chilldown process of coal spontaneous combustion in coal mine goafs. In this paper, the heat and mass transfer of liquid nitrogen in a loose medium was investigated. A laboratory system including a temperature sensing system was designed and built to explore the effects of different nitrogen injection positions and angles on the chilldown effect. The results indicate that after liquid nitrogen injection, the temperatures in the liquid nitrogen flow area and the bottom of the model can be quickly reduced to −196 °C, which was the best chilldown effect zone. With the vaporization of the liquid nitrogen, the cryogenic nitrogen gradually diffused. At 20,000 s, the bottom temperature was about –63 °C, the middle was –30 °C, and the upper was 0 °C. When the model angle was 0°, the effective chilldown zone was the largest. As the angle increased, the effective chilldown volume and holding time decreased significantly. The model angle had a greater impact on the chilldown. For the position of nitrogen injection, the inlet was set slightly farther from the gas outlet’s position, leading to a larger coverage for the liquid nitrogen and cryogenic nitrogen chilldown. This study can provide a theoretical basis for the flow and chilldown of nitrogen injection in goafs.

An experimental study on the effect of nitrogen injection on the deformation of coal during methane desorption

Field trials of nitrogen injection enhanced gas drainage in hard-to-drain coal seam by using underground in-seam (UIS) boreholes

In recent years, the use of nitrogen has increased as gas injection to recover oil fluids near the critical point. The behavior of hydrocarbon mixture phases in the critical region shows very interesting complex phenomena when facing a recovery project with nitrogen. Therefore, it is important to have experimental information of the PVTx thermodynamic variable, often scarce, for this type of critical phenomena. This paper reports the experimental measures of the volumetric behavior and phases of synthetic fluid in a nitrogen injection process. The experiment was performed at laboratory scale, and it obtained variations on the saturation pressure, gas oil ratio, density and composition of the hydrocarbon phase when nitrogen was injected at molars of 10, 20, 30 and 40% on different volumetric portions of the mother sample. In addition, the data obtained experimentally was used to demonstrate the capacity of tune to compositional models. The data provided represents a valuable contribution to the understanding of phenomena associated with retrograde and near critical regions, as well as their use in tuning and developing more elaborate models such as Cubic Equations of State (EOS). It is worth highlighting the importance of this data in the potential processes of nitrogen, CO2, and lean gas injection, which require knowledge of the gas-oil ratio, saturation pressures, density and composition of the fluid in current production. The identification of the phenomena shown, represent a potential application to the modeling of displacements and maintaining the pressure in the improved recovery when scaling up the laboratory data to the field / reservoir conditions.

Liquid nitrogen has been working as an important medium in fire extinguishing and prevention, due to its efficiency in oxygen exclusion and heat removal. Such a technique is especially crucial for coal industry in China. We built a tunnel model with a temperature monitor system (with 36 thermocouples installed) to experimentally study heat and mass transfer of liquid nitrogen in non-homogeneous coal porous media (CPM), and expected to optimize parameters of liquid nitrogen injection in engineering applications. Results indicate that injection location and amount of liquid nitrogen, together with air leakage, significantly affect temperature distribution in CPM, and non-equilibrium heat inside and outside of coal particles. The injection position of liquid nitrogen determines locations of the lowest CPM temperature and liquid nitrogen residual. In the deeper coal bed, coal particles take longer time to reach thermal equilibrium between their surface and inside. Air leakage accelerates temperature increase at the bottom of the coal bed, which is a major reason leading to fire prevention inefficiency. Measurement fluctuation of CPM temperature may be caused by incomplete contact of coal particles with liquid nitrogen flowing in the coal bed. Moreover, the secondary temperature drop (STD) happens and grows with the more injection of liquid nitrogen, and the STD phenomenon is explained through temperature distributions at different locations.

Tribological Effect of Lubricated Liquid Carbon Dioxide on TiAl6V4 and AISI1045 under Extreme Contact Conditions

The application of non-hydrocarbon gases with the aim of displacing residual gas from depleted fields is substantiated. Mathematical modeling is carried out of the process of residual gas displacing with nitrogen in the GEM compositional simulating module under the conditions of a hypothetical gas reservoir of circular shape. The said module is a part of the licensed CMG computer program. The effect of the cyclical nature of the aquifer injection nitrogen into depleted gas reservoir at different rates till the final gas recovery coefficient for residual gas is developed. The study concerns different durations of nitrogen injection cycles into the reservoir (6, 12, 18, 24, 30, and 36 months) and various correlations of the rates of nitrogen injection and gas production in reservoir conditions of 1:1; 1.5:1; 2:1. During the nitrogen injection into the reservoir, the output wells stopped; whereas after surcease of the nitrogen injection, they were again exploited until the reservoir pressure reached to 0.1 Pprimary. Then the process of cyclic nitrogen injection into the layer continued, until nitrogen break through into the producing wells and its content in the produced products reached 5% vol. The research results were processed in the form of graphical dependencies of reservoir pressure, gas flow rate and gas recovery coefficient for residual gas at the end of the cycle of nitrogen injection into the reservoir as a function of the number of such cycles. The research results indicate a significant effect on the gas recovery coefficient for the residual gas of the duration of the cycle of nitrogen injection into the reservoir and the ratio of rates of nitrogen injection and gas production, with an increase in which the coefficient of gas output gradually decreases. According to the research results, the optimal parameters of the process of nitrogen injection into the reservoir should be chosen on the basis of technological results, as well as technical and economic calculations.

The main objective of this paper is show the design, implementation and results of a nitrogen + steam pilot implemented in a Colombian heavy oil reservoir. Given that the answer to the cyclic steam injection has declined significantly in some wells of the interest field due to the high number of cycles, a pilot project to assess the feasibility of injecting nitrogen accompanied cyclic steam was raised. The determination of optimum volumes and injection scheme by numerical simulation was performed in a sector model. Eleven schemes of steam plus nitrogen injection were evaluated. In all schemes, it was tested remained constant volume of injected steam, while the volume of nitrogen varied according to the scheme (pre-injection, post-injection, co-injection or a combination of the above). In all cases, it assumed the injection of nitrogen according to real drive capacity 1200 m3/hour (1017072 ft3/day). The best case corresponds to start injecting only one day with nitrogen, followed by five days of co-injection and ending with a single nitrogen day. Under this scheme an incremental production of 5642 barrels of oil a trial period of six months, with average oil production of 53 BOPD in the same period and maximum rate of 142 BOPD. According to the simulation results, it was decided to implement the pilot steam + nitrogen injection, following the best injection scheme given above; that is, a day of pre-injection (nitrogen only), five days of co-injection (steam + nitrogen) and one day post-injection (nitrogen only). The results of the pilot show that oil production has increased compared to previous cycles, reaching similar results to the numerical simulation forecast. A methodology to implement steam injection enhanced with nitrogen is proposal in this paper, which can be applied in any field of heavy crude scheme developed under cyclic steam stimulation.

Gas/Water Flow in Porous Media in the Presence of Adsorbed Polymer: Experimental Study on Non-Darcy Effects

Analysis of rock drainage and cooling experiments for underground cryogenic LNG storage

Generally, a part of transporting liquids are used as the coolant to chill down the transfer line. Minimizing the line chill-down time and the consumption of the cryogenic propellant during the line chill-down is a mainly concerned issue. In this study, the cryogenic line chill-down experiments are conducted on a 12.7 mm outer diameter, 1.25 mm wall thickness and 7 m long stainless steel horizontal pipe with liquid nitrogen (LN2) injection. The pipe is vacuum jacketed to reduce the heat inleak from room temperature to the cryogenic liquid. The temperature and the pressure profiles of the chill-down line are obtained at the location 6 meters away from the pipe inlet under various mass flow rates. The history of the transient temperature, the pressure and the mass flow rate during the line chill-down process are monitored for various cases. The relationship between the line chill-down time and the mass flow rate is analyzed and presented for one representative pipe line geometry.

Liquid nitrogen (LN2) injection was used to against the red imported fire ant (Solenopsis invicta Buren) by taking the advantage of rapid killing, no side effects from residuals, and non-dependence on weather conditions of this method. Red imported fire ants workers were placed in glass bottles and treated by sub-zero temperatures for either two or zero minutes after thermo-equilibrium to determine the lethal low temperature. Fire ant nests were then treated by LN2 and the survival of the ants was monitored. Thus -15 °C was shown to cause 100% of mortality of workers at 24 hours post treatment. Large numbers of ant corpses, which included larvae, pupae and queens, were discovered in the nest after LN2 treatment. In a field experiment, 10 nests were treated by LN2, while 9 were left as controls. The number of active nests significantly decreased to just one nest at the 14th day post LN2 application and none was considered to be functional at the 21st day. These results suggest that LN2 freezing is capable of eliminating individual fire ant nests effectively, and that this treatment is useful for areas of high human activity and for agricultural and other areas that have a low tolerance to conventional pesticides.

Methane hydrate (MH) is one of the potential resources of natural gas in the near future, because it exists in marine sediments or in permafrost regions worldwide. Some extraction methods of MH from the reservoir have been proposed, such as depressurization, thermal stimulation and inhibitor injection. These are all based on the in-situ dissociation process of MH that is transformed into methane gas and water. However, There are some technical and economical problems for operation of these methods. Therefore, we have proposed a new enhanced gas recovery method by nitrogen injection. Nitrogen has the effect as an inhibitor as well as methanol and salts to shift an equilibrium condition of hydrate to high-temperature and low-pressure. In addition, we supposed some advantages for this process compared with conventional ones, such as 1) utilization of inexpensive and high permeable nitrogen, 2) retention of pore pressure to avoid compaction of sediments due to increase of effective stress expected in depressurization process.In this study, to clarify the physical phenomena in the reservoir and gas production behavior during nitrogen injection process, we have carried out the experimental study. The core holder type apparatus to enable observation of temperature change during MH dissociation was developed. Using this apparatus, some experiments for MH dissociation by nitrogen injection were conducted changing nitrogen injection rate as an experimental parameter. From the experimental observations, it was found that dissociation zone extended to the downstream zone of the sand column with time depending on dissociation rate and injection rate. Furthermore, we obtained high dissociated gas production rate in the case of high injection rate due to the multiple effect such as enhancement of dissociation and displacement of methane by nitrogen migration in pore space.

Nowadays, efficiency improvement of the modern gas turbines is usually achieved by increasing the pressure ratio which leads to an increase of the gas temperature in the combustion chamber. As a consequence, the temperature conditions imposed on the first stages of the turbine are well beyond the maximum allowable material of the engine. Therefore, it is necessary to effectively cool on these parts. Some of the highest thermal loading is applied to the nozzle guide vane located just behind the combustion chamber. Its function is to efficiently direct the hot and highpressure gas on the rotor blades of the turbine in order to extract maximum work. From the aerodynamic side, the loss level generated during the hot gas deviation defines the nozzle guide vane efficiency. From the thermodynamic side, an efficient nozzle guide vane is characterized by its cooling protection against the hot gas coming out of the combustion chamber. For this reason, the vane is internally cooled by coolant fluid circulating in channels; but it is also externally cooled by injection of coolant fluid on the surface. This process is usually called film-cooling. If it is well designed, the film efficiently protects the vane airfoil and platforms of the engine; but if badly designed (unfavorable holes injections positions or inadequate blowing ratios), then the overall performance of the engine is reduced. Recently, studies have shown a decrease in the aerodynamic losses for nozzle guide vanes with contoured platforms. Moreover, it has also been noticed that temperature profiles at the exit of the combustion chamber are more and more flattened and consequently require a better cooling of the platforms. The problem is to efficiently film-cool a nozzle guide vane airfoil and its contoured platforms. A numerical approach of this problem is yet not possible as the numerical codes are not accurate enough to take into account all the physics governing such situations. Therefore, an experimental approach is required. So far, many film cooling studies have been performed but on relatively simple geometries (flat plates, cylinders etc.). The innovative part of this present work was to study film cooling on a complex nozzle guide vane geometry equipped with contoured platforms. For this, as well the aerodynamic side and the thermodynamic side related to film cooling were considered. The experiments were divided into two parts. The first part was dedicated to the study of the vane airfoil. The second part was dedicated to the film-cooling study on the contoured platforms. In both cases, heat transfer coefficients and film-cooling effectiveness were determined by transient measurement techniques using liquid crystals. For the vane airfoil, a preconditioning system followed by a rapid insertion was used. This installation was already used during previous projects, but in the frame of this research work, the liquid crystal technique was improved. For this, a new signal analysis and image processing system was developed. For the measurements on the platforms, a new measurement technique based on the use of a thin electrical heater-foil was developed. The innovation of this technique comes from the fact that it can be applied on complex geometries for which inhomogeneous heat fluxes are produced (curved surfaces, introduction of cooling holes). This novel measurement technique was first tested and validated on a simple geometry consisting of a film-cooled flat plate. The same technique was then applied to the film-cooled contoured platform and allowed obtaining interesting results of heat transfer coefficient and film-cooling effectiveness distributions. The latter result was also compared to values obtained from another innovative measurement technique based on Pressure Sensitive Paint with Nitrogen injection. The results obtained in the frame of this experimental work dedicated to film cooling applied on a complex geometry were obtained thanks to the development of novel measurement techniques. These measurement techniques provide the opportunity to perform systematic tests in order to gain further insight into the physics of the film cooling process on complex geometries such as contoured platforms.

OLMAT (Optimization of Liquid Metal Advanced Targets) is a new High Heat Flux (HHF) Facility for testing solid and liquid metallic targets at DEMO-relevant power densities that has been installed, commissioned and first operated at the National Fusion Laboratory in Madrid in 2021 [1] . A Neutral Beam Injector (NBI) is used as a high-power source providing 100 ms pulses at maximum repetition rate of 1p/30s and delivering power densities at the target (Mo, W, liquid Sn) above 50 MW/m 2 [2] . A calibrated survey spectrometer covering the UV-visible-near IR ranges provided information about the impinging hydrogenic species, plasma composition and its microscopic parameters, while a Balmer Ha (656.3 nm) monitor, a 16-Channel PMT array and a fast-frame imaging camera were used for the characterization of particle recycling and the plume’s spatial structure. Moreover, the floating voltage and saturation current developed at the target was monitored on a shot-to-shot basis. In addition to the above, nitrogen injection was performed through a dedicated piezoelectric valve for active spectroscopy. Plasma temperatures between 1 and 2 eV were deduced from the ratios of H Balmer lines, in line with the recorded values of floating potential, but higher, inconsistent values were obtained from the ratio of molecular N 2 and N 2 + bands. The facility and the plasmas therein generated will be described.