Decline In Pressure Research Articles

Experimental and numerical study on gas production decline trend under ultralong-production-cycle from shale gas wells

It is of engineering interest to explore recovered shale gas composition and its effects on total gas production trend over a long-term extraction period. However, there are previous experimental studies mostly focused on short term development for small scaled cores, which is less convincing to mimic reservoir-scaled shale production process. In addition, the previous production models mostly failed to account for comprehensive gas nonlinear effects. As a result, in this paper, to illustrate the full-life-cycle production decline phenomenon for shale gas reservoir, dynamic physical simulation was performed for more than 3433 days to simulate shale gas transport out of the formations over a relatively long production period. Moreover, a five-region seepage mathematical model was then developed and was subsequently validated by the experimental results and shale well production data. Our findings show that for physical simulation, both the pressure and production declined steadily at an annual rate of less than 5%, and 67% of the total gas in the core was recovered. These test data supported earlier finding that shale gas is of low flow ability and slow pressure decline in the shale matrices. The production model indicated that free gas accounts for the majority of recovered shale gas at the initial stage. Based on a shale gas well example, free gas extraction makes up 90% of produced total gas. The adsorbed gas constitutes a primary gas source during the later stage. Adsorbed gas contributes more than 50% of the gas produced in the seventh year. The 20-year-cumulative adsorbed gas makes up 21% of the EUR for a single shale gas well. The results of this study can provide a reference for optimizing production systems and adjusting development techniques for shale gas wells throughout the combinations of mathematical modeling and experimental approaches.

Predicting dry weight change in Hemodialysis patients using machine learning

BackgroundMachine Learning has been increasingly used in the medical field, including managing patients undergoing hemodialysis. The random forest classifier is a Machine Learning method that can generate high accuracy and interpretability in the data analysis of various diseases. We attempted to apply Machine Learning to adjust dry weight, the appropriate volume status of patients undergoing hemodialysis, which requires a complex decision-making process considering multiple indicators and the patient’s physical conditions.MethodsAll medical data and 69,375 dialysis records of 314 Asian patients undergoing hemodialysis at a single dialysis center in Japan between July 2018 and April 2020 were collected from the electronic medical record system. Using the random forest classifier, we developed models to predict the probabilities of adjusting the dry weight at each dialysis session.ResultsThe areas under the receiver-operating-characteristic curves of the models for adjusting the dry weight upward and downward were 0.70 and 0.74, respectively. The average probability of upward adjustment of the dry weight had sharp a peak around the actual change over time, while the average probability of downward adjustment of the dry weight formed a gradual peak. Feature importance analysis revealed that median blood pressure decline was a strong predictor for adjusting the dry weight upward. In contrast, elevated serum levels of C-reactive protein and hypoalbuminemia were important indicators for adjusting the dry weight downward.ConclusionsThe random forest classifier should provide a helpful guide to predict the optimal changes to the dry weight with relative accuracy and may be useful in clinical practice.

Balanced volatile sedation with isoflurane in critically ill patients with aneurysmal subarachnoid hemorrhage - a retrospective observational study.

In patients with severe aneurysmal subarachnoid hemorrhage (SAH) deep sedation is often used early in the course of the disease in order to control brain edema formation and thus intracranial hypertension. However, some patients do not reach an adequate sedation depth despite high doses of common intravenous sedatives. Balanced sedation protocols incorporating low-dose volatile isoflurane administration might improve insufficient sedation depth in these patients. We retrospectively analyzed ICU patients with severe aneurysmal SAH who received isoflurane in addition to intravenous anesthetics in order to improve insufficient sedation depth. Routinely recorded data from neuromonitoring, laboratory and hemodynamic parameters were compared before and up to 6 days after initiation of isoflurane. Sedation depth measured using the bispectral index improved in thirty-six SAH patients (-15.16; p = 0.005) who received additional isoflurane for a mean period of 9.73 ± 7.56 days. Initiation of isoflurane sedation caused a decline in mean arterial pressure (-4.67 mmHg; p = 0.014) and cerebral perfusion pressure (-4.21 mmHg; p = 0.013) which had to be balanced by increased doses of vasopressors. Patients required increased minute ventilation in order to adjust for the increase in PaCO2 (+2.90 mmHg; p < 0.001). We did not detect significant increases in mean intracranial pressure. However, isoflurane therapy had to be terminated prematurely in 25% of the patients after a median of 30 h due to episodes of intracranial hypertension or refractory hypercapnia. A balanced sedation protocol including isoflurane is feasible for SAH patients experiencing inadequately shallow sedation. However, therapy should be restricted to patients without impaired lung function, hemodynamic instability and impending intracranial hypertension.

Application of the modified capacitance-resistance method to model reservoir pressure maintenance

A pressure maintenance strategy is crucial in reservoir management, especially in single-phase oil reservoirs, to keep the reservoir pressure above the bubble point. Water injection is a common way to prevent pressure decline due to production. Water may be injected into oil zone and/or aquifer. Analytical and semi-analytical methods are applied to analyze the reservoir response and pressure alteration during the water injection and pressure maintenance operation. Capacitance- Resistance Model (CRM) is a well-known semi-analytical method to predict oil production by water flooding.In this work, Static Capacitance- Resistance Model (SCRM) in which time constant parameter is unique value in whole matching duration has been applied to estimate water injection in the reservoirs with charging aquifer; in addition to, our aim is analytical investigation of water injection performance in the aquifer zone. As a matter of fact, SCRM has been coupled for the reservoir and aquifer in which SCRM has been written for a reservoir and an aquifer zone as two independent porous medium. Consequently, SCRM has been developed to estimate pressure maintenance performance in the cases of charging aquifer; moreover, new parameter is defined as pressure difference between aquifer and reservoir transition zone (DP) is added to SCRM tuning parameters that can indicate flow and reverse flow between reservoir and aquifer.This parameter is a water saturation-dependent function considered as another tuning parameter. Two synthetic reservoirs were simulated in this work, including homogenous and streak cases with nine spot patterns. The developed SCRM has shown acceptable accuracy, of which 6.1% of total absolute error was obtained for the homogenous case and 7.5% for the streak case.

Improvement in cardiac function and regional LV strain following intramyocardial injection of a theranostic hydrogel early postmyocardial infarction in a porcine model.

Myocardial infarction (MI) is often complicated by left ventricular (LV) remodeling and heart failure. We evaluated the feasibility of a multimodality imaging approach to guide delivery of an imageable hydrogel and assessed LV functional changes with therapy. Yorkshire pigs underwent surgical occlusions of branches of the left anterior descending and/or circumflex artery to create an anterolateral MI. We evaluated the hemodynamic and mechanical effects of intramyocardial delivery of an imageable hydrogel in the central infarct area (Hydrogel group, n = 8) and a Control group (n = 5) early post-MI. LV and aortic pressure and ECG were measured and contrast cineCT angiography was performed at baseline, 60 min post-MI, and 90 min post-hydrogel delivery. LV hemodynamic indices, pressure-volume measures, and normalized regional and global strains were measured and compared. Both Control and Hydrogel groups demonstrated a decline in heart rate, LV pressure, stroke volume, ejection fraction, and pressure-volume loop area, and an increase in myocardial performance (Tei) index and supply/demand (S/D) ratio. After hydrogel delivery, Tei index and S/D ratio were reduced to baseline levels, diastolic and systolic functional indices either stabilized or improved, and radial strain and circumferential strain increased significantly in the MI regions (ENrr: +52.7%, ENcc: +44.1%). However, the Control group demonstrated a progressive decline in all functional indices to levels significantly below those of Hydrogel group. Thus, acute intramyocardial delivery of a novel imageable hydrogel to MI region resulted in rapid stabilization or improvement in LV hemodynamics and function.NEW & NOTEWORTHY Our study demonstrates that contrast cineCT imaging can be used to evaluate the acute effects of intramyocardial delivery of a therapeutic hydrogel to the central MI region early post MI, which resulted in a rapid stabilization of LV hemodynamics and improvement in regional and global LV function.

Propagation and sealing efficiency of chemical grouting in a two-dimensional fracture network with flowing water

In this study, an orthogonal array experiment is conducted by using a transparent fracture network replica. Image processing and theoretical analysis are performed to investigate the model sealing efficiency (SE), factors influencing SE, and the effect of flowing water on propagation. The results show that grout propagation can be classified into three patterns in the fracture network: sealing off, partial sealing, and major erosion. The factors controlling the SE in a descending order of the amount of influence are the initial water flow speed, fracture aperture, grout take, and gel time. An optimal value for the combination of the gel time and grout take (artificial factors) can result in a good SE. The grouting and seepage pressures are measured, and the results reveal that their variations can indicate the SE to some extent. The SE is good when the seepage pressure at each point increases overall; the frequent fluctuations in the seepage pressure indicate a moderately poor SE, and an overall decline in the seepage pressure indicates a major erosion type. The deflection effect of grouting shows an approximately elliptical propagation with the long axis expanding along the wider fracture opening, demonstrating further application in grouting design.

Relationship between blood pressure and cognitive decline in normal cognitive population: A four‐year follow‐up study in rural Xi'an

AbstractBackgroundHypertension is a modifiable risk factor for cognitive impairment, although the relationship between hypertension and cognitive impairment is not fully understood. The objective of to clarify the relationship between blood pressure and cognitive decline in cognitive normal population through a longitudinal follow‐up study.MethodCognitively normal population was selected from people who lived in the suburbs of Xi’an, China.The mini‐mental state examination (MMSE) and neuropsychological battery were used to assess cognition. Four years later, MMSE was tested again and cognitive decline was defined as a decrease in MMSE scores ≥2 points.The relationship between blood pressure parameters [systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP),] and cognitive impairment was analyzed by logistic regression models using interaction and stratified analysis. Blood pressure and age were regarded as both continuous and categorical data。ResultA total of 1024 participants completed the study, among whom 168 subjects (16.41%) presented cognitive decline.Interaction analysis for the total population showed that SBP (when regarded as continuous data) was positively correlated with cognitive impairment (OR = 1.173 [95% CI,1.030‐1.335] per 10mmHg, P = 0.016); however, the age by SBP interaction term was inclined to be negatively correlated with cognitive impairment (OR = 0.850 [95% CI, 0.711–1.016] per10mmHg×year, P = 0.074), indicating that the relationship between SBP and cognitive impairment was age‐dependent. When the blood pressure and age were considered as binary data, the results were similar to those obtained when they were considered as continuous variables.Stratified multivariate analysis revealed that the relationship between SBP (when regarded as continuous data) and cognitive impairment was positive for patients aged 50‐59 years (OR = 1.209 [95% CI:1.025–1.427] per 10mmHg, P = 0.024).However, positive results were not obtained for DBP and MABP.ConclusionElevated blood pressure is positively correlated with cognitive impairment in the middle age(50‐59), but this positive association declines with increasing age.

Role of Orthostatic Hypotension in the Development of Dementia in People With and Without Cardiovascular Disease.

Orthostatic hypotension (OH) has been associated with elevated risk of cardiovascular diseases (CVDs) and dementia risk. To better understand the OH-dementia association, we assessed the associations of OH with CVD and subsequent dementia in older adults and considered the temporality of CVD and dementia onset. This 15-year population-based cohort study included, at baseline, 2703 dementia-free participants (mean age, 73.7 years) who were divided into a CVD-free cohort (n=1986) and a CVD cohort (n=717). OH was defined as a systolic/diastolic blood pressure decline of ≥20/10 mm Hg after standing up from a supine position. CVDs and dementia were ascertained by physicians or identified from registers. Multistate Cox regressions were applied to assess the associations of OH with CVD and subsequent dementia in the CVD-free and dementia-free cohort. The OH-dementia association in the CVD cohort was examined with Cox regressions. OH was present in 434 (21.9%) individuals in the CVD-free cohort and 180 (25.1%) individuals in the CVD cohort. OH was associated with a hazard ratio of 1.33 (95% CI, 1.12-1.59) for CVD. OH was not significantly associated with incident dementia in the absence of CVD occurring before dementia diagnosis (hazard ratio, 1.22 [95% CI, 0.83-1.81]). In the CVD cohort, individuals with OH had a higher dementia risk than those without OH (hazard ratio, 1.54 [95% CI, 1.06-2.23]). The association between OH and dementia may partly be explained by the intermediate development of CVD. In addition, in people with CVD, those with OH may have a poorer cognitive prognosis.

Effects of Ozone Addition on Multi-Wave Modes of Hydrogen–Air Rotating Detonations

Ozone addition presents a promising approach for optimizing and regulating both combustion and ignition mechanisms. In Rotating Detonation Engines (RDEs), investigating the impact of ozone addition is particularly important due to the fact of their unique operating conditions and potential for improved efficiency. This study explores the influence of ozone concentration, total temperature, and equivalent ratio on the combustion characteristics of a hydrogen–air mixture infused with ozone. Utilizing the mixture as a propellant, the combustion chamber of a continuous rotating detonation engine is replicated through an array of injection ports, with numerical simulations conducted to analyze the detonation wave combustion mode. Our results show that an increase in total temperature leads to an increase in the number of detonation waves. Incorporating a minor quantity of ozone can facilitate the ignition process for the detonation wave. Increasing the ozone content can result in the conversion from a single-wave to dual-wave or multi-wave mode, providing a more stable combustion interface. A low ozone concentration acts as an auxiliary ignition agent and can significantly shorten the induction time. As the total temperature increases, the detonation propagation velocity and the peak heat release rate both decrease concurrently, which leads to a decline in the exit total pressure and an augmentation in the specific impulse. Employing ozone exerts a minimal impact on the detonation propagation and the overall propulsion performance. The requirement for ozone-assisted initiation differs noticeably between rich and lean combustion.

Sex differences in autonomic and cardiovascular responses during lower-body negative pressure

Female adults have a lower tolerance to central hypovolemia, simulated by tilt testing and lower body negative pressure (LBNP; PMID: 26109186). However, the mechanisms responsible for this observation remain unknown. Previous studies investigated sex differences at baseline and presyncope, but the intermediate responses are not fully understood, particularly when expressed as a percentage of tolerance. Therefore, the purpose of this study was to compare autonomic and cardiovascular responses to a simulated hemorrhage between female and male adults at the same relative percentage of their tolerance. We tested the hypothesis that females would have lower blood pressure (BP) and muscle sympathetic nerve activity (MSNA) at the same relative percentage of their tolerance. Eight female (28±8 years old, 171±8 cm, 77±6 kg, BMI: 27±3 kg/m 2 ) and eight male (age: 32±7 years old, height: 178±9 cm, mass: 86±10 kg, BMI: 27±2 kg/m 2 ) adults completed a progressive LBNP protocol that started at -40 mmHg and was further reduced by 10 mmHg every 3 minutes until the participant reached pre-syncope. Presyncope was based on the following criteria: continued reports by the subject of feeling faint and/or nauseous; a rapid decline in blood pressure resulting in systolic blood pressure &lt; 80 mmHg; and/or a relative bradycardia accompanied by narrowing of pulse pressure. LBNP tolerance was quantified as a cumulative stress index (CSI) (mmHg·min) and was compared between sexes using an unpaired t-test. MSNA (microneurography - radial nerve), beat-to-beat blood pressure (BP; Finometer), and heart rate (HR) were obtained at baseline, at 33% and 66% of maximum CSI (60-second averages for both), and the last 30 seconds before 100% CSI (i.e., presyncope). Data were statistically analyzed between the sexes using mixed effects analysis and are presented as mean ± SD. Consistent with prior findings, tolerance to LBNP was lower in females (female: 607±369 vs. male: 960±339 mmHg·min, p = 0.067). There were no differences in systolic, mean, or diastolic BP or HR between the sexes (e.g., main effect of sex, p &gt; 0.199 for all indices) throughout the protocol. MSNA burst frequency (bursts/min) (baseline: 18±8 vs. 25±11; 33% CSI: 30±13 vs. 50±5; 66% CSI: 38±11 vs. 56±4; 100% CSI: 28±10 vs. 40±12; sex: p = 0.004, stage: p &lt; 0.0001, interaction: p = 0.704) and burst incidence (bursts/100 cardiac cycles) (baseline: 29±9 vs. 41±20; 33% CSI: 38±21 vs. 58±10; 66% CSI: 35±18 vs. 52±10; 100% CSI: 32±18 vs. 37±12; sex: p = 0.047, stage: p = 0.022, interaction: p = 0.952) were lower in females than males throughout the protocol, respectively. However, there was no interaction between sexes and relative LBNP stages for MSNA burst frequency or burst incidence. These findings suggest a lack of sex differences in the magnitude of the increase of MSNA throughout LBNP and that lower basal sympathetic activity may be related to reduced tolerance to central hypovolemia. Department of Defense - US Army W81XWH1820012 (CGC) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Looking at the Big picture: Reclassifying water disposal wells into injectors to safeguard field reserves and future potential

The Deep Water Disposal project was initiated in 1995 with the aim of managing excess water output from the primary facility. The injection into a shared deep formation has resulted in a significant boost to the pressure in nearby fields. This effect can be observed through pressure measurements, which demonstrate that the field was in a state of depletion before the commencement of water disposal. However, the pressure stabilized once stable disposal rates were established. Recently, a decline in nearby fields' pressure has been noticed in response to lower disposal rates[5]. The objective of this study is to evaluate the level of pressure support in adjacent areas resulting from the volume of waste disposal and establish the necessary disposal rate needed to sustain the desired pressures. Ultimately, the goal is to reclassify the relevant portion of deep-water disposal volume as proper water injection[1], to avoid any unnecessary decommissioning of the disposal wells and hence losing this energy source to the reservoir. This Novel approach of mixing operational and reservoir data deals directly with the topic of voidage replacement, pressure decline, reservoir behavior, impact of deep water disposal and water injection of performance, and conducting simple forecasting methodology that is fit for purpose to come up with practical results to be directly applied in a real life situation.

Design of Subsea storage tanks for Arctic conditions - heat treatment of materials

The Arctic region contains a plethora of recoverable hydrocarbon wealth in the form of oil and gas in existing conventional wells and other undiscovered fields. The main challenges faced in the Arctic region are both environmental and operational. Some environmental challenges are low ambient temperature, winterization, severity and unpredictability of the weather. However, the issue of multi-phase flow in the current operation coupled with the decline of the reservoir pressure are the major concerns in this gas field. In the early stages of field life, the reservoir pressure is sufficient to allow the natural flow from reservoir formation to surface without additional supporting compression. Unfortunately, the pressure naturally declines throughout the entire life cycle of the field. To achieve a better production profile in the arctic region the idea is to implement a Subsea processing concept employing a Subsea Storage Tank (SST) in order to maximize production from additional infield wells, introducing a novel step in this field development phase that will change the entire oil and gas industry especially for subsea processing field architecture. The incorporation of SST in the subsea system will enhance the production rate as well as it avoids the transportation problems through pipe lines. By this work, the production rate is increased by 50% and decrease the oil spill accidents considerably.

Pump-stopping pressure drop model considering transient leak-off of fracture network

By introducing the coupling flow expressions of main fracture-matrix, secondary fracture-matrix and main fracture-secondary fracture into the traditional main fracture material balance equation, the “main fracture—secondary fracture—matrix” leak-off coupling flow model is established. The pressure-dependent fracture width equation and the wellbore injection volume equation are coupled to solve the pressure-rate continuity problem. The simulation and calculation of the bottomhole pressure drop and fracture network closure after the pump stopping in slickwater volumetric fracturing treatment are realized. The research results show that the log-log curve of pump-stopping bottomhole pressure drop derivative presents five characteristic slope segments, reflecting four dominant stages, i.e. inter-fracture crossflow, fracture network leak-off, fracture network closure and residual leak-off, after pump shutdown. At the initial time of pump shutdown for volumetric fracturing treatment of horizontal well, the crossflow between main and secondary fractures is obvious, and then the leak-off becomes dominant. The leak-off of main and secondary fractures shows a non-uniform decreasing trend. Specifically, the leak-off of main fractures is slow, while that of secondary fractures is fast; the fracture network as a whole presents the leak-off law of fast first, then slow, until close to zero. The influence of fracture network conductivity on the shape of pressure decline curve is relatively weaker than that of fracture network size. The fracture network conductivity is positively correlated with leak-off volume and fracture closure. The secondary fracture size is positively correlated with leakoff volume and closure of the secondary fracture, but negatively correlated with closure of the main fracture. Field data validation proves that the proposed model and simulation results can effectively reflect the closure characteristics of the fracture network, and the interpretation results are reliable and can reflect the non-uniform stimulation performance of each fracturing stage of an actual horizontal well.

Nodal and least-cost analysis on the optimization of natural gas production system constraints to extend the plateau rate of a conceptual gas field

The supply of natural gas in any country is determined by energy demand. Furthermore, supply agreements specify that gas should be supplied at a constant rate for a specified period. However, due to the decline in reservoir pressure as gas fields continue to produce, high constant rate production is usually uncertain, and the plateau may not reach the agreed-upon period. Therefore, this study was conducted to optimize gas production system constraints and extend the production plateau rate of a conceptual dry gas field. The field was made up of the sand packages CF2 upper, CF2 lower, CF1 upper, and CF1 lower. A total of 1316.9 Bscf were assumed to be the estimated gas field reserves, and 423.3 Bcf were assumed to be the remaining economically recoverable gross 2 P sales of natural gas. The field also contained natural gas at the Miocene and five production wells, numbered PW-1, PW-2, PW-3, PW-4, and PW-5. The field's estimated average constant gas production rate as of July 2021 was 85 MMscfd. The field's gas demand was forecasted in three phases, with the third beginning on November 1, 2019, at a rate of 130 MMscfd. After applying Nodal Analysis with the help of Integrated Production Modelling (IPM) and Least Cost Analysis methods, the study found that the gas production plateau of that field started to decline on March 1, 2017, after 1 year and 5 months of production when constrained to 130 MMscfd. However, after modifying the constraints to match various assumed production histories, it was discovered that the plateau would start to decline on June 1, 2023, after 8 years of production. Therefore, eight possible combinations of varying the three production constraints were developed and simulated to examine their effect on extending the field production plateau. These constraints were separator pressure, tubing size, and the number of layers perforated. The best combination was to lower the separator pressure to 725 psia, increase the tubing size to 4 inches, and perforate three more zones (zones I, C, and D). This was the only combination that appeared to extend the production plateau for 8 years until October 1, 2031, as required in the 16 years gas sales agreement (GSA). This approach was economically compared to the options of using a compressor and drilling future wells, and it was found to be 34.05% cheaper than the compressor usage option and 98.25% cheaper than drilling a well. As a result, the operators of this conceptual gas field are advised to adopt this approach to extend the field's plateau.

Determination of Water Drive Mechanism Activation Using Geological Model for Heavy Oil Field in North of Iraq

Most of the productive oil fields around the world are water drive reservoirs where water influx has the potential to improve oil recovery considerably. Verifications are required to illustrate the aquifer activation and this needs assessment programs to include diagnosis, classifications and aquifer characterization using mathematical models for accurate simulation of the aquifer behavior. In Qaiyarah Oil Field, there is a big lack in subsurface data to confirm the aquifer's level of activity although there are some traces of water production from the wells located at the southwest of the field. Based on this fact, a base case simulation has run through making history match for the production and reservoir pressure to confirm the activation of the aquifer. The results showed a fast decline in the reservoir pressure which mismatched the current measured pressure from the field. This led to adopt the option of modelling a simulated properties aquifer to match the production and pressure from the field in a step to confirm the aquifer activation. The simulation had re-run with multi trials to approve the aquifer strength, geological and reservoir properties. Finally, history match showed perfect matching on production and pressure through selecting edge aquifer model that matched with the available subsurface data from the field. The cumulative production till the end of 2021 was calculated to be 47,142,257 bbls and reservoir pressure was 387 Psi, which almost match the measured cumulative production from the field that was 47,100,000 bbls and reservoir pressure of 389 Psi which was considered a very acceptable match.

Trajectories of systolic blood pressure decline in kidney transplant donors prior to circulatory death and delayed graft function.

Kidneys donated after circulatory death suffer a period of functional warm ischaemia before death, which may lead to early ischaemic injury. Effects of haemodynamic trajectories during the agonal phase on delayed graft function (DGF) is unknown. We aimed to predict the risk of DGF using patterns of trajectories of systolic blood pressure (SBP) declines in Maastricht category 3 kidney donors. We conducted a cohort study of all kidney transplant recipients in Australia who received kidneys from donation after circulatory death donors, divided into a derivation cohort (transplants between 9 April 2014 and 2 January 2018 [462 donors]) and a validation cohort (transplants between 6 January 2018 and 24 December 2019 [324 donors]). Patterns of SBP decline using latent class models were evaluated against the odds of DGF using a two-stage linear mixed effects model. In the derivation cohort, 462 donors were included in the latent class analyses and 379 donors in the mixed effects model. Of the 696 eligible transplant recipients, 380 (54.6%) experienced DGF. Ten different trajectories, with distinct patterns of SBP decline were identified. Compared with recipients from donors with the slowest decline in SBP after withdrawal of cardiorespiratory support, the adjusted odds ratio (aOR) for DGF was 5.5 [95% confidence interval (CI) 1.38-28.0] for recipients from donors with a steeper decline and lowest SBP [mean 49.5mmHg (standard deviation 12.5)] at the time of withdrawal. For every 1mmHg/min reduction in the rate of decline of SBP, the respective aORs for DGF were 0.95 (95% CI 0.91-0.99) and 0.98 (95% CI 0.93-1.0) in the random forest and least absolute shrinkage and selection operator models. In the validation cohort, the respective aORs were 0.95 (95% CI 0.91-1.0) and 0.99 (95% CI 0.94-1.0). Trajectories of SBP decline and their determinants are predictive of DGF. These results support a trajectory-based assessment of haemodynamic changes in donors after circulatory death during the agonal phase for donor suitability and post-transplant outcomes.

Mechanical model for geomechanical pumped storage in horizontal fluid‐filled lenses

AbstractPumped subsurface energy storage entails pumping fluid into fluid‐filled lenses in subterranean rock formations during times of peak power production, and then later producing the fluid back to the surface to drive a turbine. A new mechanical model is developed for lens behavior during flowback (production), shut‐in, and inflation (storage) stages. The model couples elastic deformation of the lens with Darcy–Weisbach fluid flow spanning the laminar to turbulent regimes. It includes an energy‐based inlet boundary condition governing fluid flow rate out of the lens and up to the Earth's surface. It also introduces pressure‐dependent leakoff of fluid to the surrounding rock and the impact of intact rock bridges, which can arise from the lens having multiple petals or lobes, on lens compliance. The model is then used to illustrate the transition from early‐time gradual decline in wellhead pressure and flow rate to eventual pinching of the lens width at the wellbore, leading to rapid decline of pressure and flow rate. The model demonstrates the feasibility of efficient storage cycles that generate a desired amount of power over a desired time while avoiding pinching. Maximizing efficiency is shown to have at least two contrasting regimes depending on whether the fluid leakoff rate to the host rock is dependent on the fluid pressure. The development of this model is therefore an essential step in deployment of subsurface energy storage by providing a mechanical basis for storage lens design.

Mean annual intradialytic blood pressure decline and cardiovascular events in Japanese patients on maintenance hemodialysis.

An intradialytic systolic blood pressure (SBP) decline, which defines intradialytic hypotension, may be associated with higher all-cause mortality. However, in Japanese patients on hemodialysis (HD), the association between intradialytic SBP decline and patient outcomes is unclear. This retrospective cohort study included 307 Japanese patients undergoing HD over 1 year in three dialysis clinics and evaluated the association between the mean annual intradialytic SBP decline (predialysis SBP-nadir intradialytic SBP) and clinical outcomes, including major adverse cardiovascular events (MACEs; cardiovascular death, nonfatal myocardial infarction or unstable angina, stroke, heart failure, and other severe cardiovascular events requiring hospitalization) by following up for 2 years. The mean annual intradialytic SBP decline was 24.2 (25-75th percentile, 18.3-35.0) mmHg. In the model fully adjusted for intradialytic SBP decline tertile group (T1, <20.4 mmHg; T2, 20.4 to <29.9 mmHg; T3, ≥29.9 mmHg), predialysis SBP, age, sex, HD vintage, Charlson comorbidity index, ultrafiltration rate, use of renin-angiotensin system inhibitors, corrected calcium, phosphorus, human atrial natriuretic peptide, geriatric nutritional risk index, normalized protein catabolism rate, C-reactive protein, hemoglobin, and use of pressor agents, Cox regression analyses showed that the hazard ratio (HR) was significantly higher for T3 than for T1 for MACEs (HR, 2.38; 95% confidence interval 1.12-5.09) and all-cause hospitalization (HR, 1.68; 95% confidence interval 1.03-2.74). Therefore, in Japanese patients on HD, a greater intradialytic SBP decline was associated with worse clinical outcomes. Further studies are warranted to investigate whether interventions to attenuate the intradialytic SBP decline will improve the prognosis of Japanese patients on HD.

Application of CCUS in India: Designing a CO2 EOR and storage pilot in a mature field

Numerous mature oil and gas reservoirs around the world, along with added financial benefit, present a tremendous benefit of CO2 EOR and storage, especially in the regions where tax benefits and policies related to the CCS is limited. This work presents the first effort of CO2 EOR and storage in a mature oil field in India through a comprehensive application of laboratory study, reservoir static modeling, dynamic simulation, pilot design, and techno-economic sensitivity analyses. Through this case study, the technical feasibility of CO2 EOR and associated storage was assured for the first time through a novel approach of combining various subsurface and surface data with laboratory analyses. Almost no analog was available for CCUS on the same-age rock from a young thrust belt setting. The various vintages of core to seismic scale data posed a great challenge for effective integration. The solution approach to these issues included combining flow physics, fluid chemistry, geological concepts and digital modeling with practical engineering data analyses. Temporal change of oil composition in this reservoir due to the long production history had created some challenges for determination of CO2 miscibility. It was estimated through the lab study and modeling that the miscibility can be achieved near 3000 psi due to its altered oil composition resulted by years of production. To arrest the reservoir pressure decline, a pre-EOR water injection was identified as an immediately need to re-pressurize the reservoir and achieve miscibility of injected CO2. Comprehensive analysis of various subsurface and surface data integrating geoscience and engineering techniques have allowed for a consistent and applicable 3D description of reservoir, which was critical to identify suitable areas with appropriate remaining oil saturation, chemistry, and reservoir pressure. The history matching-calibrated-simulation model was utilized to evaluate the performance of various development scenarios of the identified area. Specifically, CO2 injection in a sector of geological model was performed using Todd-Longstaff miscible flood scheme. Upon comparing the proposed scenarios, a CO2 injection pilot in Pattern-1 was identified, with one injector and three producers over ∼60 acres area. This pilot uses 150 Metric Ton/day (MT/D) of CO2 captured and processed from an existing facility and transported about 70 km to the field location. The CO2 will be injected continuously into this pilot area for 5 years, and the well switches back to water injection afterward. Around 1.1 MMSTB incremental oil will be recovered in next 10 years, corresponding to 11.7% of OOIP in the flooded area. Up to 268,275 MT of CO2 will be sequestered in the reservoir. The learnings from this first ever study of its kind in India set the benchmark for data analysis, integration, and case specific approaches. The success and knowledge base from this endeavor will tremendously help and encourage further expansion of CCUS activities in India.

Significant Improvement in Blood Pressure Levels Among Older Adults With Hypertension in Rural South Africa.

Sub-Saharan Africa is undergoing an epidemiologic transition from infectious diseases to cardiovascular diseases. From 2014 to 2019, sociodemographic surveillance was performed in a large cohort in rural South Africa. Disease prevalence and incidence were calculated using inverse probability weights. Poisson regression was used to identify disease predictors. The percentage of individuals with controlled (<140/90 mm Hg) versus uncontrolled hypertension was compared between 2014 and 2019. Compared with 2014 (n=5059), study participants in 2019 (n=4176) had similar rates of obesity (mean body mass index, 27.5±10.0 versus 27.0±6.5) but higher smoking (9.1% versus 11.5%) and diabetes (11.1% versus 13.9%). There was no significant increase in hypertension prevalence (58.4% versus 59.8%; age adjusted, 64.3% versus 63.3%), and there was a significant reduction in mean systolic blood pressure (138.0 versus 128.5 mm Hg; P<0.001). Among hypertensive individuals who reported medication use in 2014 and 2019 (n=796), the proportion with controlled hypertension on medication increased from 44.5% to 62.3%. Hypertension incidence was 6.2 per 100 person-years, and age was the only independent predictor. Among normotensive individuals in 2014 (n=2257), 15.2% developed hypertension by 2019, with the majority already controlled on medications by 2019. The hypertension prevalence and incidence are plateauing in this aging cohort. There was a statistically and clinically significant decline in mean blood pressure and a substantial increase in individuals with controlled hypertension on medication. The prevalence of cardiometabolic risk factors did not decrease over time, suggesting that the blood pressure decrease is likely due to increased medication access and adherence, promoted by local health systems.