Constant Gas Injection Research Articles

Influence of wellhead pressure and water cut in the optimization of oil production from gas lifted wells

The worldwide increase in energy demand necessitates the development and optimization of marginal oil fields for sustenance. In this regard, effective and economic production of fluids are heavily relied upon the artificial lift techniques as the reservoir's natural energy may not be able to deliver the fluids to the surface. Gas lift is a widely practised and successful method that is suitable for rejuvenating the oil production from such fields. In this study, the influence of critical parameters like water cut, wellhead pressure (WHP) and gas-lift gas injection rate on the output from a gas lifted well was analysed. A significant reduction in the oil production was observed with the increase in water cut. For a fixed gas injection rate of 1 Mmscf/day, the production decreased by 26.90% when the water cut increased from 15% to 30% and further by 50.80% when the water cut reached 45%. An increase in the gas injection rate from 1 Mmscf/day to 8 Mmscf/day resulted in an increase in the production rate by 29.21%, 40.48% and 56.56% for 15%, 30%, and 45% water cut conditions, respectively. It was observed that there is a drop in the oil rate with the increase in WHP for a constant gas injection rate. An increase in the WHP from 100 psi to 300 psi resulted in a drop in the oil production rate by 11.01%, 11.78% and 12.74% for 15%, 30% and 45% water cut conditions, respectively. The study sheds light on the significance of optimizing the critical parameters to maximize the production from a well, with severely affected productivity, using a continuous gas lift system.

Analysis of metallic impurity content by means of VUV and SXR diagnostics in hybrid discharges with hot-spots on the JET-ITER-like wall poloidal limiter

In preparation for the upcoming JET D–T campaign, great effort has been devoted during the 2015–2016 JET campaigns with the ITER-like wall (ILW) to the extension of the high performance H-mode phase in baseline and hybrid scenarios. Hybrid discharges were the only ones that have been stopped by the real-time vessel protection system due hot-spot formation on the outboard poloidal limiter. Generation of hot-spots was linked to the application of high neutral beams injection and ion cyclotron resonance heating (ICRH) power. In tokamaks with high-Z plasma components, the use of ICRH heating is also accompanied by an increased metallic impurity content. Simultaneous control of hot-spot temperature and the core impurity content was crucial due to the fact that the same plasma-wall interaction mechanism is responsible for both phenomena. Impurity data collected by SXR, EUV and VUV diagnostics were able to provide for the first time comprehensive information concerning tungsten and mid-Z impurities such as nickel, iron, and cooper. To determine absolute mid-Z impurity concentrations a new relative calibration technique, compatible with JET-ILW, has been developed based on cross-calibration with a calibrated spectrometer via the quasicontinuum of W in the 200–400 Å wavelength range. In hybrid discharges, it was found that local D2 gas injection, plasma current, separatrix density, and fast ion losses appeared to impact hot-spot temperature and core impurity levels. Analysis showed a reduced maximum hot-spot temperature and impurity concentration at higher gas rate. Changes in the plasma current had a strong impact on the plasma-wall interaction, both via modifications in the edge density and in the fast ion losses. At constant gas injection rate, both the hot-spot temperature and the core impurity content decreased with the separatrix density. The main mechanism responsible for the formation of the hot-spots was found to be linked to the fast ion losses, but RF sheath effects may also be playing a role in the high limiter temperatures observed in these experiments.

Quantifying the reimbibition effect on the performance of gas‐oil gravity drainage in fractured reservoirs: Mathematical modelling

AbstractAs a major oil production mechanism, gravity drainage in fractured oil reservoirs is heavily affected by the reimbibition phenomenon. In this work, a stack of oil‐saturated two matrix blocks surrounded by oil‐saturated fractures are considered as a synthetic fractured reservoir. A mathematical computer program is developed to numerically simulate the fluids’ flow through the matrixes and fractures employing the finely gridded single porosity concept. Simulation results are validated by checking the continuity of the gas volume through the reservoir. The percentage of oil recovered by gravity drainage is determined employing the new material balance equation approach. A new procedure is employed for deactivating the reimbibition phenomenon, introducing the zero transmissibility for the oil phase in the case of oil transfer from the fracture to matrix region. According to the simulation results and considering the proposed model, under the constraints of constant gas injection and oil production rates, fully or partially deactivating the reimbibition phenomenon causes a faster gas movement through vertical fractures. The reason for this is that some of the oil leaving the upper matrix block goes to vertical fractures and causes a faster gas breakthrough in them due to reduced available pore volume to gas. In this case the oil recovered by gravity drainage from the system is decreased. Inactivating this phenomenon in the simulated case study causes a 40 % reduction in oil production by gravity drainage from the matrix blocks until the breakthrough time.

Integrity Assessment of Open-Circuit Respiration Chambers for Ruminant Animal Indirect Calorimetry

Abstract. Open-circuit chambers have been widely applied to gas exchange measurement for indirect calorimetry and greenhouse gas emission. The reliability of these systems is crucial and is commonly evaluated through recovery tests. These tests simulate gas exchanges of animals through the injection or consumption of known quantities of gases, while monitoring the gas flux with the measurement system, and then comparing the difference between the known mass and the measured mass to assess the system integrity. Although the recovery test approach is widely accepted, the method of how to choose recovery tests has rarely been documented, and no single source has been found that summarizes a complete process for evaluating a system and correcting post-evaluation systematic errors. In this study, three recovery methods were applied: (1) the alcohol combustion method (ACM) burns a known amount of pure ethanol to simulate both consumption (O2) and production (CO2); (2) the gravimetric gas injection method (GRAV) directly measures the weight change of a compressed CO2 gas cylinder during the injection process; and (3) the constant gas injection method (CGIM) steadily injects sulfur hexafluoride (SF6) gas into the chamber. An experiment was conducted that included eight repeated trials for each of the three methods in six identical chambers (144 total tests) of the Ruminant Emission Measurement System (REMS) at the Beef Cattle and Sheep Field Laboratory at the University of Illinois in Urbana-Champaign. The recovery percentages of the respiratory quotient for the six ACM chambers varied from 72.58% to 77.76%, indicating that measurement and calculation errors occurred in the system. The CGIM and GRAV methods were used for identifying the errors from ventilation measurement and calculation of exhaust airflow rate. Correction factors were generated from the results and proved effective, as recovery percentages were improved to an acceptable level (100% ±5%) for all chambers. This approach can be applied to other studies and other systems to assist in selecting appropriate integrity tests and applying correction methods. Keywords: Cattle, Emissions, Gas exchange, Metabolism, Recovery method, Tracer gas measurement.

Effect of temperature on foamability using a thermoresponsive polymer

We experimentally examine foam dynamics and foamability using a thermoresponsive polymer, Poly(n-isopropylacrylamide) or PNIPAM. Under a constant gas injection, our results show that temperature significantly affects the foam height produced. A stable foam was observed at room temperature while unstable at temperature above the lower critical solution temperature. Analysis of the foam structure reveals an important increase in the coalescence rate at high temperature, thereby suggesting a change of the air-water interface properties with the temperature. The findings demonstrate the controlling ability of the PNIPAM polymer to produce thermoresponsive foams, offering beneficial applications for foaming processes and mineral flotation.

Photocatalytic degradation of NO/NO2 gas injected into a 10-m3 experimental chamber.

This paper investigates a new test method to assess the photocatalytic activity of plasterboards coated with a TiO2 dispersion under real-world conditions. The degradation of nitrogen oxides NO x (NO and NO2) is studied and the photocatalytic efficiency under UV illumination is evaluated in a 10-m3 room after a constant gas injection. Two ultrafine TiO2 dispersions are used: 0.85% TiO2 and 5% TiO2, and three types of gas are tested: an NO/NO2 mixture (8/8mol-ppm), NO (45mol-ppm) and NO2 (45mol-ppm). The test method presented here is midway between laboratory and real-scale procedures and allows better control of the experimental parameters than a real field experiment. Testing a mixture of NO and NO2 is a way to get closer to real-world conditions as air is polluted by various gases. This study focuses on the degradation of NO and NO2 under UV illumination when two types of TiO2 dispersions are used and highlights the difference in behaviour between these two molecules in terms of photocatalytic degradation. The results show that photocatalytic activity does not appear to be efficient to degrade NO2 molecules. Another mechanism seems to be responsible for the reduction of the concentration of NO2, namely adsorption. Encouraging results are obtained with NO molecules, which can be degraded by photocatalysis. The degradation observed is even greater with the more concentrated TiO2 dispersion.

Plasma isotopic change over experiments in JET under Carbon and ITER-Like Wall conditions

Starting with a wall loaded by H2, change over experiments from H2 to D2 have been carried out in JET-ILW. A series of 13 repetitive pulses (cumulating 215s in divertor configuration) have been performed under conditions of: Ip=2.0MA, BT=2.4T, 〈ne〉=4.5×1019m−3 with a constant gas injection of 3.0×1021Ds−1 and 0.5MW of auxiliary heating by ICRH in L-mode. Gas balance analysis shows that the total amount of H removed from the wall is in the range of 3×1022D compared to 2×1023D for JET-C. This is consistent with the faster decay of the H plasma concentration and the drop of the retention also by a similar factor when removing all the carbon components.Isotopic plasma wall changeover is also demonstrated to allow for removal of some D/T from the device. However, since plasma change over also contributes to long-term retention by codeposition, in ITER, change over in between each discharge might not be effective to reduce the fuel retention on the long-term.

Optimisation of dead-end filtration conditions for an immersed anoxic membrane bioreactor

The optimisation of the energy demand in the application of dead-end filtration in an immersed membrane bioreactor applied to groundwater denitrification has been studied. Filtration cycle length was varied at a set flux to control the amount of foulant deposited at the membrane surface. Physical cleans comprising a simultaneous backflush and gas injection were subsequently instigated and the reversibility of the deposit determined by the residual resistance, R res. Examination of R res versus flux and cycle length variation indicated an operational envelope where limited fouling occurred. The transition from limited fouling to extensive fouling was indicated by a parameter based on the critical accumulated mass, indicating incipient deposit consolidation. The transition between regions became less severe when the solids retention time was increased from 10 to 25 and 40 days. This was apparently related to a shift in bulk physical characteristics. Nevertheless, low residual fouling was observed during long-term filtration when operating below the critical mass, resulting in a 20× reduction in energy demand over that of constant gas injection.

Investigation of the effects of fractured porous media on hydraulic tests—an experimental study at laboratory scale using single well methods

In this paper, a study of detailed pneumatic tests at laboratory scale is presented. The study comprises two different test methods, which were conducted on an unsaturated fractured sandstone block of about 1 m 3 volume. First, a steady-state flow field with constant gas injection pressure and consequently constant gas flow rates was applied to the fractured sandstone block via a vertical borehole. The discharge of the injected gas was measured at the block surface. Second, a constant gas pressure was injected over the borehole and the transient pressure buildup was recorded at the block surface. It was the objective of the study to investigate the effects of the fractured porous system on pneumatic measurements and to provide an insight into processes occurring during flow and pressure buildup in fractured porous media. This is an essential prerequisite for a reliable validation of different modeling approaches, and it can further assist to improve techniques for the determination of the heterogeneity of hydraulic parameters in fractured porous media. The analysis of the distribution of the flow field and the temporal and spatial evolution of pressure buildup during the hydraulic tests shows that the direction and contribution of the flow field is highly depending on the spatial distribution and the characteristics of the fracture network as well as on the position of the observation points with respect to highly conductive structures. Finally, the introduced test methods are suitable tools for the characterization of the heterogeneous nature of fractured porous media and for the interpretation of the effects of the heterogeneous system on hydraulic tests.

Bubble formation at a single orifice in gas-fluidised beds

An earlier developed hydrodynamic model describing dense gas-solid two phase flow has been used to study the bubble formation process at a single orifice. A systematic experimental and theoretical study has been conducted to investigate the effect of particle properties (i.e. particle diameter and density) on the bubble growth process for Geldart type B powders. Theoretical results, obtained for both two-dimensional and three-dimensional geometries, have been compared with experimental data and with predictions from approximate models reported in literature. A comparison of the theoretical results and experimental data shows that the advanced hydrodynamic model gives a satisfactory good description of the bubble growth process for several particle types which makes this model a useful tool to study the bubble formation process in fluidised beds. It appears that the influence of particle size and particle density on bubble formation can be related to the effect of the minimum fluidisation velocity on this process. At a constant gas injection rate through the orifice higher minimum fluidisation velocities result in larger bubbles and decreased leakage. Further, it has been found that coarse particles give rise to the formation of relatively elongated bubbles. The detachment times, on the other hand, seem to be independent of the particle size used.

Nonlinear effects associated with the mutual displacement of two gases in a porous medium

The cyclic bidirectional process of isothermal flow of a binary singlephase compressible gas mixture in a porous medium accompanied by diffusion-dispersion mass transfer is considered. On the basis of the equations of multiphase multicomponent isothermal flow a system of two nonlinear partial differential equations with nonlinear boundary conditions corresponding to a given constant gas injection or takeoff rate is obtained and investigated. A numerical algorithm for solving the boundary-value problem obtained is proposed.

Control of carbon dioxide concentration in glasshouses by the use of conductimetric controllers

A two-rate, on/off conductimetric system of controlling CO 2 concentration in nine separate glasshouses is described and the practical aspects of operating it are discussed. Analysis of monitored CO 2 levels revealed that the mean daily controlled concentration achieved over a period of five months was within ±3 % of the desired value for 84% of the enrichment time and within ±5 % for 95 % of the time. Data are presented showing the relationship between the amount of CO 2 used to maintain concentrations ranging from 600 to 1400 v.p.m. (1·20–2·80 g/m 3 ) and mean wind speed measured outside the glasshouse. Measurement of CO 2 in a glasshouse enriched by the commercial method, i.e. constant gas injection at a rate equivalent to 50 lb acre −1 h −1 (56 kg ha -1 h -1 ) showed that the mean daily CO 2 concentration varied with wind speed outside the glasshouse and fell to 790 and 710 v.p.m. (1·58 and 1·42 g/m 3 ) in February and March respectively in a glasshouse containing November-sown tomato plants.