Petrophysical Reservoir Characterization of Habiganj Gas Field, Surma Basin, Bangladesh

The previous studies on the petrophysical and volumetric analysis of Habiganj gas field were based on limited well data. As the accuracy of volumetric analysis relies greatly on petrophysical parameters, it is important to estimate them accurately. In this study we analyzed all eleven wells drilled in the Habiganj field to determine the petrophysical parameters. Analysis of the well logs revealed two distinct reservoir zones in this field termed as upper reservoir zone and lower reservoir zone. Stratigraphically, these two reservoir zones are in the Bokabil and Bhuban Formation of Surma Group. Petrophysical analysis shows significant differences between the two zones in terms of petrophysical parameters. Porosity in the upper reservoir zone ranges from 12% to 36%, with an average of 28%. This zone is highly permeable, as indicated by the average permeability of 500 mili Darcy (mD). The average water saturation in this zone is around 18% suggesting high gas saturation. The lower reservoir zone has an average porosity, permeability, and water saturation of 12%, 60mD, and 43%, respectively, indicating poor reservoir quality. An analysis of log motifs indicates that the upper reservoir zone is composed of stacked sands of blocky pattern. The sands in this interval are clean, as indicated by the lower shale volume of 12-15%. The average thickness of this zone is 230m, and the presence of this zone in all the drilled wells suggests high lateral continuity. The lower reservoir zone consists of sand bodies of serrated pattern. The sands have high shale volume and are laterally discontinuous. Overall, the upper reservoir zone has superior petrophysical properties to the lower reservoir zone. Although the reservoir quality of the lower reservoir zone is poorer than that of the upper zone, this zone can be considered as the secondary target for hydrocarbon production. Petrophysical parameters of this study were estimated from all the eleven wells drilled in this field; hence the values are more accurate. The reported values of the petrophysical parameters in this study are recommended to use to re-estimate the reserves in Habiganj field. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 10(1), 2021, P 1-10

Hydrodynamical and Hydrochemical Assessment of Pumped-Storage Hydropower (PSH) Using an Open Pit: The Case of Obourg Chalk Quarry in Belgium

Pumped storage hydropower (PSH) enables the temporary storage of energy, including from intermittent renewable sources, and provides answers to the difficulties related to the mismatch between supply and demand of electrical energy over time. Implementing a PSH station requires two reservoirs at different elevations and with large volumes of water. The idea of using old, flooded open-pit quarries as a lower reservoir has recently emerged. However, quarries cannot be considered as impervious reservoirs, and they are connected to the surrounding aquifers. As a result, PSH activities may entail environmental impacts. The alternation of the pumping–discharge cycles generates rapid and periodic hydraulic head fluctuations in the quarry, which propagate into the surrounding rock media forcing the exchange of water and inducing the aeration of groundwater. This aeration can destabilize the chemical balances between groundwater and minerals in the underground rock media. In this study, two numerical groundwater models based on the chalk quarry of Obourg (Belgium) were developed considering realistic pumping–discharge scenarios. The aim of these models was to investigate the hydrodynamic and hydrochemical impact of PSH activities on water inside the quarry and in the surrounding rock media. Results showed that (1) water exchanges between the quarry and the adjacent rock media have a significant influence on the hydraulic head, (2) the frequency of the pump–discharge scenarios influence the potential environmental impacts, and (3), in the case of chalk formations, the expected impact of PSH on the water chemical composition is relatively limited around the quarry. Results highlight that those hydrogeological and hydrochemical concerns should be assessed when developing a project of a PSH installation using a quarry as a lower reservoir, considering all particularities of the proposed sites.

Impaired left atrial reservoir and conduit strain in patients with atrial fibrillation and extensive fibrosis

Funding Acknowledgements Type of funding sources: None. Background Atrial fibrillation (AF) is associated with profound structural and functional changes in the atria. Timely interventions may decelerate and perhaps reverse this pathophysiologic process and improve clinical outcome. In this regard, detailed characterization of the atrial remodeling process, and understanding of the interplay between structural remodeling and function is essential. Purpose In the present study, we investigated the association between left atrial (LA) phasic function and the extent of LA fibrosis using advanced cardiovascular magnetic resonance (CMR) imaging techniques, including 3-dimensional (3D) late gadolinium enhancement (LGE) and Feature Tracking. Methods Patients with paroxysmal and persistent AF (n = 93) underwent CMR in sinus rhythm. LA global reservoir strain, conduit strain and contractile strain were derived from cine CMR images using Feature Tracking. The extent of LA fibrosis was assessed from 3D LGE images. Healthy volunteers underwent CMR and served as controls (n = 19). Results Significantly lower reservoir strain, conduit strain and contractile strain were found in AF patients, as compared to controls (-15.7 ± 3.9% vs. -21.1 ± 3.6% P < 0.001, -8.6 ± 2.9% vs. -12.6 ± 2.5% P < 0.001 and -7.1 ± 2.4% vs. -8.6 ± 2.2% P = 0.02, respectively) (Figure A, B, C). Patients with a high degree of LA fibrosis (dichotomized by the median value) had lower reservoir strain and conduit strain compared to patients with a low degree of LA fibrosis (-14.7 ± 4.0% vs. -16.8 ± 3.5%, P = 0.02 and -7.7 ± 2.7% vs. -9.5 ± 2.9%, P < 0.01, respectively). In contrast, no difference was found for LA contractile strain (-7.0 ± 2.3% vs. -7.3 ± 2.5%, P = 0.62) (Figure D, E, F). Conclusions This study shows impaired LA reservoir and conduit strain in AF patients with extensive atrial fibrosis. Of interest, LA contractile function was largely unaffected. Future studies are required to study the biologic nature of this association and possible therapeutic implications. Abstract Figure.

MARINE RESERVOIR AGE CORRECTION FOR THE ANDAMAN BASIN

ABSTRACTMarine reservoir age is an important component for correction in radiocarbon (14C) dating of marine and coastal samples. 14C concentration in pre-bomb marine samples of known age are used to derive marine reservoir age of a region. Annually banded coral from Landfall island in the northern Andaman has been analyzed for its 14C concentration during the pre-bomb period 1948–1951. 14C age and reservoir effect (∆R) are reported for these pre-bomb coral samples from the northern Andaman region. The mean 14C age of 331 ± 61 yr BP was obtained for the period 1948–1951 with an average reservoir age correction of –138 ± 61 yr. This reservoir age correction is lowest reported from the northern Indian Ocean. ∆R value of the northern Andaman and the Bay of Bengal appears lower than that of southern Andaman. The ∆R values obtained using mollusk shells and coral from the Andaman region shows large variability. The lower reservoir age correction for the Landfall Island situated in the northern part of the Andaman archipelago, could result due to freshwater flux and reduced upwelling in the region.

Impact of Different Photovoltaic Models on the Design of a Combined Solar Array and Pumped Hydro Storage System

The impact of different photovoltaic models for a combined solar array and pumped hydro storage system was investigated. Al-Wehda dam located in Harta city in the northern of Jordan was used to validate the approach. The two-diode (TD), single-diode (SD), and ideal single-diode (ISD) solar models were evaluated in terms of the solar array size, reliability, and ecological effects. The impoundment of Al-Wehda dam was taken as the upper reservoir of the pumped hydro facility of the proposed renewable energy system. It was found that the PV power is more accurately modelled by considering the recombination loss in the TD solar model. This leads to a more realistic sizing and precise system evaluation. Results were obtained using the particle swarm optimization (PSO) algorithm and the whale optimization algorithm (WOA) for validation purposes. For instance, the PSO results showed that the realistic TD model is reliable, with an index of reliability of 98.558%. Further, it is the most ecological solution with an annual emissions reduction of 21.5198 Gg. The optimized values are 44,840 solar panels and 65.052 M.m3 of the lower reservoir volume for the TD model. The number of PV panels are reduced by 16.67% and 7.93%, respectively, with the ISD and SD relative to the TD model.

Effect of blood viscosity on the performance of virtually wall-less venous cannulas

Aim: This study was designed to quantify the influence of blood as test medium compared to water in cannula bench performance assessment. Methods: An in vitro circuit was set-up with silicone tubing between two reservoirs. The test medium was pumped from the lower reservoir by centrifugal pump to the upper reservoir. The test-cannula was inserted in a silicone tube connected between the lower reservoir and the centrifugal pump. Flow rate and pump inlet-pressure were measured for wall-less versus thin-wall cannula using a centrifugal pump in a dynamic bench-test for an afterload of 40-60 mmHg using two media: blood 10 g/dL and 5.6 g/dL and water 0 g/dL. Results: The wall-less cannula showed significantly higher flows rates as compared to the thin-wall cannula (control), with both hemoglobin concentrations and water. Indeed, for a target volume of 200-250 mL of blood (Hg 10 g/dL) in the upper reservoir, the cannula outlet pressure (P) was −14 ± 14 mmHg versus −18 ± 11 mmHg for the wall-less and control respectively; the cannula outlet flow rate (Q) was 3.91 ± 0.41 versus 3.67 ± 0.45 L/min, respectively. At the same target volume but with a Hg of 5.7 g/dL, P was −16 ± 12 mmHg versus −19 ± 12 mmHg and Q was 4 ± 0.1 versus 4 ± 0.4 L/min for the wall-less cannula and control respectively. Likewise, P and Q values with water were −1 mmHg versus −0.67 ± 0.58 mmHg and 4.17 ± 0.45 L/min versus 4.08 ± 0.47 L/min for the wall-less and control respectively. Conclusion: Walls-less cannula showed 5.6% less pump inlet-pressure differences calculated between blood and water, as compared to that of thin-wall cannula (−21 times). Flow differences were 6% and 10% for the walls-less and thin-wall cannula respectively. We conclude that testing the cannula performance with water is a good scenario and can overestimate the flow by a 10%. However, superiority for wall-less is preserved with both water and blood.

Short-Term Optimal Operation of Cascade Reservoirs Considering Dynamic Water Flow Hysteresis

In making short-term optimal operation schemes of cascade reservoirs, water flow hysteresis between the upper reservoir and the lower reservoir is often considered as constant, which cannot really reflect the hysteresis variation between different water flows and will lead to losses of the optimal operation scheme’s benefit. To depict the water flow hysteresis, a Dynamic Water Flow Hysteresis Method (DWFHM) is proposed, based on the space mapping principle. With the mapping operator in the DWFHM, the lower reservoir inflow can be directly obtained. Besides, the DWFHM is used to deal with the hydraulic relation constraint in the short-term optimal operation model of cascade reservoirs. Then, the improved model is applied to the Jinguan cascade reservoirs in the Yalong River basin and solved by an Improved Progressive Optimal Algorithm (IPOA). The results are as follows. (1) Compared with the traditional Fixed Water Flow Hysteresis Method (FWFHM), the inflow processes of the lower reservoir obtained by the DWFHM are more in line with the actual values, due to full consideration of the attenuation effect. (2) The optimal operation with the DWFHM can effectively increase the generated energy (2827 MW·h and 504 MW·h in the non-flood season and the flood season, respectively). Through the analysis of this case, the DWFHM developed in this study can effectively improve the practicability of the optimal operation scheme and reduce the risk in the operation of cascade reservoirs.

Movement and longitudinal distribution of a migratory fish ( Salminus brasiliensis) in a small reservoir in southern Brazil

ABSTRACT We investigated whether the movement and distribution of the migratory fish, Salminus brasiliensis, were affected by a small reservoir. We also examined how movement and distribution were related to water temperature, flow, and rainfall. In December 2011 and January 2012, 24 individuals were captured downstream from the dam, tagged with radio transmitters and released in the reservoir (5.46 km² total area). After being released in the reservoir, 18 of the 24 tagged fish travelled upstream, taking an average of 16.6 days to leave the reservoir, with daily movements varying from < 5 km/day to > 24 km/day. However, only seven tagged specimens (29.16%) returned to the lower reservoir section, while the rest remained in the intermediate and upper reservoir sections. Longitudinal distributions and movements were positively related to both upstream flow into the reservoir and water temperature. We found evidence that S. brasiliensis can recognize the longitudinal gradient and is able to continue its upstream migration. On the other hand, the reservoir negatively affected downstream movements, possibly because disorientation prevented movement to the lower reservoir section. Based on these results, we suggest that the impact of small reservoirs on migratory fish species should be objectively addressed in environmental impact assessments and management programs.