Two-Phase Flow Model for Numerical Investigation of Impact of Water Retention on Shale Gas Production

In this work, a triple-porosity, two-phase flow model was established to fill the knowledge gap of previous models focusing on gas production characteristics while ignoring the impacts of water injection. The proposed model considers the water flow in the fracture systems and clay minerals and the gas flow in the organic matter, inorganic pore, and fracture systems. The proposed model is solved using a finite element approach with COMSOL Multiphysics (Version 5.6) and verified with field data. Then, the evolutions of the intrinsic and relative permeabilities during water injection and gas production are examined. Furthermore, the impacts of water injection time and pressure are investigated. Good verification results are obtained; the goodness-of-fit value is 0.92, indicating that the proposed model can replicate both the water stimulation and the gas production stages. The relative gas permeability declines during water injection but recovers in the gas depletion stage. Furthermore, the intrinsic permeability increases during the water injection stage but decreases during the gas production stage. A higher water injection pressure and longer injection time would enlarge the intrinsic permeability, thus improving flow capacity. However, it would reduce gas relative permeability, thereby hindering gas flow. The shale gas production characteristic is controlled by the two abovementioned competing mechanisms. There exists a perfect combination of water injection pressure and injection time for achieving the maximum profitability of a shale gas well. This work can give a better understanding of the two-phase flow process in shale reservoirs and shed light on the field application of hydraulic fracturing.

Numerical simulation and optimization of CO2 enhanced gas recovery in homogeneous and vertical heterogeneous reservoir models

CO2 enhanced gas recovery (CO2-EGR) is a promising, environment-friendly technology with simultaneously sequestering CO2. The goals of this paper are to conduct simulations of CO2-EGR in both homogeneous and heterogeneous reservoirs to evaluate effects of gravity and reservoir heterogeneity, and to determine optimal CO2 injection time and injection rate for achieving better natural gas recovery by employing a genetic algorithm integrated with TOUGH2. The results show that gravity segregation retards upward migration of CO2 and promotes horizontal displacement efficiency, and the layers with low permeability in heterogeneous reservoir hinder the upward migration of CO2. The optimal injection time is determined as the depleted stage, and the corresponding injection rate is optimized. The optimal recovery factors are 62.83 % and 64.75 % in the homogeneous and heterogeneous reservoirs (804.76 m × 804.76 m × 45.72 m), enhancing production by 22.32 × 103 and 23.00 × 103 t of natural gas and storing 75.60 × 103 and 72.40 × 103 t CO2 with storage efficiencies of 70.55 % and 67.56 %, respectively. The cost/benefit analysis show that economic income of about 8.67 and 8.95 million USD can be obtained by CO2-EGR with optimized injection parameters respectively. This work could assist in determining optimal injection strategy and economic benefits for industrial scale gas reservoirs.

The study of the strongest solar event on a minimum of the 24th solar cycle

The strongest solar flares of the 24th solar cycle erupted on September 6, 2017, and it was the 8th strongest solar flare recorded since 1996. This extreme solar flare occurred at the minimum of the 24th solar cycle. The active region is located in the Western Hemisphere and produced the violent explosion of class X9.3 and X2.2 on September 6, X1.3 on September 7, and X8.2 on September 10, 2017. The injection duration of the solar energetic particles of the solar event was 17 minutes. All data for this solar event was collected from the Advanced Composition Explorer and simulated for particles’ motion using the transport equation and solved by the numerical technique. We obtained the injection time of the solar energetic particle propagation by comparing fitting between the simulation results and the spacecraft data. Injection time taken by high-energy particles to travel from the Sun to the Earth was found to be in the range of 39 to 743 minutes. At the peak of this solar flare, the coronal mass ejection was detected, which increased the injection time. The Kp-index of this solar flare was 4; thus, there was no effect on the Earth. The Kp-index value increased to 8 on September 7-8, 2017, due to another solar event from the same sunspot region, indicating the effect of solar flare and CME, which resulted in the appearance of aurora.

Improved estimation of volcanic SO₂ injections from satellite observations and Lagrangian transport simulations: the 2019 Raikoke eruption

Monitoring and modeling of volcanic plumes is important for understanding the impact of volcanic activity on climate and for practical concerns, such as aviation safety or public health. Here, we applied the Lagrangian transport model Massive-Parallel Trajectory Calculations (MPTRAC) to estimate the SO2 injections into the upper troposphere and lower stratosphere by the eruption of the Raikoke volcano (48.29° N, 153.25° E) in June 2019 and its subsequent long-range transport and dispersion. First, we used SO2 observations from the AIRS (Atmospheric Infrared Sounder) and TROPOMI (TROPOspheric Monitoring Instrument) satellite instruments together with a backward trajectory approach to estimate the altitude-resolved SO2 injection time series. Second, we applied a scaling factor to the initial estimate of the SO2 mass and added an exponential decay to simulate the time evolution of the total SO2 mass. By comparing the estimated SO2 mass and the observed mass from TROPOMI, we show that the volcano injected 2.1 ± 0.2 Tg SO2 and the e-folding lifetime of the SO2 was about 13 to 17 days. The reconstructed injection time series are consistent between the AIRS nighttime and the TROPOMI daytime measurements. Further, we compared forward transport simulations that were initialized by AIRS and TROPOMI satellite observations with a constant SO2 injection rate. The results show that the modeled SO2 change, driven by chemical reactions, captures the SO2 mass variations observed by TROPOMI. In addition, the forward simulations reproduce the SO2 distributions in the first ~10 days after the eruption. However, diffusion in the forward simulations is too strong to capture the internal structure of the SO2 clouds, which is further quantified in the simulation of the compact SO2 cloud from late July to early August. Our study demonstrates the potential of using combined nadir satellite observations and Lagrangian transport simulations to further improve SO2 time- and height-resolved injection estimates of volcanic eruptions.

Optimization of Liquid Accumulation and Gas Injection Duration in Intermitter for Maximizing Production: Case Study

Gas lift is the process of injecting gas into the tubing at a predetermined depth in order to lift the crude oil to the surface. Gas lift is applied to a well when the reservoir pressure falls to such a level that it does not produce without application of external energy. There are mainly two types of gas lift which are Continuous and Intermittent gas lift. This paper deals with the theoretical determination of relationship between liquid accumulation and gas injection duration in an intermittent gas lift well and how this knowledge can be combined with the experience of Engineers to maximize the production of a well. In order to find the relationship between the given durations, a simple mathematical approach with the assumption that the gas injection time is independent of liquid accumulation time is followed. We, then apply various tools of mathematics such as the principles of maxima and minima, Leibnitz theorem, definition of the slope of a line etc. to finally prove the interdependence of liquid accumulation and gas injection time at which the well can produce at its maximum capacity. This interdependence is plotted on a separate graph with the given times on two axis. This curve represents the values at which the reservoir inflow is maximised and hence another curve representing the tubing outflow is drawn on the same graph to intersect the former curve at the optimum value of liquid accumulation and gas injection time. The paper also discusses the physical significance of the cases in which the two curves do not intersect and its possible solutions which vary in accordance with the experience of engineers and conditions of well. Our mathematical calculation led to an astonishing result that the interdependence between the two given durations is elegant and can be easily found without the use of computer in a very short interval of time. The result indicated that if a tangent is drawn from a point representing gas injection time to the graph of accumulation height versus time, it touches the graph at the value of liquid accumulation time at which the production of well is maximized. This novel approach to determine the value of time in an intermitter or time cycle controller in an intermittent well can be proved to be a boon for gas lift optimizers who would otherwise spend a large part of the time in setting the value on hit and trial basis. The graphical method can determine the optimum value in a shorter interval of time and with greater accuracy saving companies from extra man-hours and unscientific approach to optimizing any intermittent gas lift well.

Dietary zinc concentration and lipopolysaccharide injection affect circulating trace minerals, acute phase protein response, and behavior as evaluated by an ear-tag based accelerometer in beef steers

To assess plasma trace mineral (TM) concentrations, the acute phase protein response, and behavior in response to a lipopolysaccharide (LPS) challenge, 96 Angus cross steers [average initial body weight (BW): 285 ± 14.4 kg] were sorted into two groups by BW (heavy and light; n = 48/group), fitted with an ear-tag based accelerometer (CowManager SensOor; Agis, Harmelen, Netherlands), and stagger started 14 d apart. Consecutive day BW were recorded to start the 24-d trial (d -1, 0). Dietary treatments began on d 0: common diet with either 30 (Zn30) or 100 (Zn100) mg supplemental Zn/kg DM (ZnSO4). On day 17 steers received one of the following injection treatments intravenously to complete the 2 × 3 factorial: 1) SALINE (~2-3 mL of physiological saline), 2) LOWLPS: 0.25 µg LPS/kg BW or 3) HIGHLPS: 0.375 µg LPS/kg BW. Blood, rectal temperature (RT), and BW were recorded on d 16 (-24 h relative to injection), and BW was used to assign injection treatment. Approximately 6, 24 (d 18), and 48 (d 19) h after treatment BW, RT, and blood were collected, and final BW recorded on d 24. Data were analyzed in Proc Mixed of SAS with fixed effects of diet, injection, diet × injection; for BW, RT, dry matter intake (DMI), plasma TM, and haptoglobin repeated measures analysis was used to evaluate effects over time. Area under the curve analysis determined by GraphPad Prism was used for analysis of accelerometer data. Body weight was unaffected by diet or injection (P ≥ 0.16), but there was an injection × time effect for DMI and RT (P < 0.05), where DMI decreased in both LPS treatments on d 16, but recovered by d 17, and RT was increased in LPS treatments 6 h post-injection. Steers receiving LPS spent less time highly active and eating than SALINE (P < 0.01). Steers in HIGHLPS spent lesser time ruminating, followed by LOWLPS and then SALINE (P < 0.001). An injection × time effect (P < 0.001) for plasma Zn showed decreased concentrations within 6 h of injection and remained decreased through 24 h before recovering by 48 h. A tendency for a diet × time effect (P = 0.06) on plasma Zn suggests plasma Zn repletion occurred at a greater rate in Zn100 compared to Zn30. These results suggest increased supplemental Zn may alter rate of recovery of Zn status from an acute inflammatory event. Additionally, ear-tag-based accelerometers used in this study were effective at detecting sickness behavior in feedlot steers, and rumination may be more sensitive than other variables.

Injection time related to intraocular pressure using a CO2 driven preloaded injector: An experimental laboratory study

Purpose Experimental study to measure the intraocular lens (IOL) injection time and injection speed at different intraocular pressure (IOP) settings when using the AutonoMe® injector. Methods In this experimental study, following phacoemulsification in porcine cadaver eyes, a trocar was inserted at pars plana with a connected infusion and IOPs of 20, 50 and 80 mmHg were generated by altering the infusion height. Twelve CO2 gas-driven injectors were used to implant an IOL via a corneal incision of 2.2 mm. For each IOP setting, the duration of the IOL injection and the injection speed was measured by analyzing a video recording of the procedure. Results The mean ±SD injection time (seconds) was 4.47±0.50 at 20 mmHg, 4.98±0.55 at 50 mmHg and 5.47±0.20 at 80 mmHg. The mean ±SD injection speed (millimeters per seconds) was 1.36±0.15 at 20 mmHg, 1.22±0.14 at 50 mmHg and 1.10±0.04 at 80 mmHg. There was a significant (p<0.05) difference between the 20 and 80 mmHg groups in mean injection duration and injection speed. Conclusion The CO2 gas driven injector allows a safe IOL injection even at elevated IOP. Although the implantation time is slightly extended at higher IOPs, this does not seem to be clinically relevant. No IOL damage was observed at these pressure settings.