Presence Of Free Gas Research Articles

Frequency of Small Bowel Perforation among Neonates Presented with Pneumoperitoneum: A Cross Sectional Study

Background: Neonatal pneumoperitoneum, characterized by the presence of free gas within the peritoneal cavity, is a critical condition often signaling intestinal perforation. While necrotizing enterocolitis (NEC) has been predominantly associated with this condition, various other etiologies contributing to neonatal intestinal perforations necessitate further exploration. The management of such conditions, particularly in resource-limited settings, remains a challenge, often resulting in significant morbidity and mortality. Objective: This study aims to investigate the frequency of small bowel perforation among neonates presenting with pneumoperitoneum and to examine the association between neonatal weight and the occurrence of small bowel perforation. Methods: A cross-sectional study was conducted at Shaukat Khanum Memorial Cancer Hospital, Lahore, Pakistan, from July 2023 to December 2023. Seventy neonates aged 5 to 25 days presenting with radiological evidence of pneumoperitoneum were included. Demographic details were collected, and the infants underwent primary peritoneal drainage followed by exploratory laparotomy if necessary. Data analysis was performed using SPSS version 25, employing Chi-Square tests for categorical variables, with a significance level set at p < 0.05. Results: Of the 70 neonates, 20 (28.6%) were diagnosed with small bowel perforation. A significant association was found between small bowel perforation and neonatal weight; 13 (65%) of the perforation cases were among neonates weighing less than 2.5 kg (p = 0.0001). The overall mortality rate observed was 35%, with 20 neonates succumbing shortly after peritoneal drain insertion due to sepsis. Conclusion: Small bowel perforation is a significant complication in neonates with pneumoperitoneum, with a higher incidence observed in those with lower birth weights. This study highlights the critical need for immediate diagnosis and intervention in such cases, particularly in under-resourced settings, to improve outcomes.

Diagnostic value of identifying location and amount of free gas in the abdominal cavity by multidetector computed tomography in patients with acute gastrointestinal perforation

Objective: To evaluate the relationships between the location and extent of diffusion of free intraperitoneal air by multi-slice spiral CT (MSCT) and between the location and size of acute gastrointestinal perforation. Methods: This was a descriptive case series. We examined abdominal CT images of 33 patients who were treated for intraoperatively confirmed gastrointestinal perforation (excluding appendiceal perforation) in the Department of General Surgery, Nanfang Hospital between January and September 2022. We identified five locations of intraperitoneal air: the subphrenic space, hepatic portal space, mid-abdominal wall, mesenteric space, and pelvic cavity. We allocated the 33 patients to an upper gastrointestinal perforation (n=23) and lower gastrointestinal perforation group (n=10) base on intraoperative findings and analyzed the relationships between the locations of free gas and of gastrointestinal perforation. Additionally, we established two models for analyzing the extent of diffusion of free gas in the abdominal cavity and constructed receiver operating characteristic (ROC) curves to analyze the relationships between the two models and the size of the gastrointestinal perforation. Results: In the upper gastrointestinal perforation group, free gas was located around the hepatic portal area in 91.3% (21/23) of patients: this is a significantly greater proportion than that found in the lower gastrointestinal perforation group (5/10) (P=0.016). In contrast, free gas was located in the mesenteric interspace in 8/10 patients in the lower gastrointestinal perforation group; this is a significantly greater proportion than was found in the upper gastrointestinal perforation group (8.7%, 2/23) (P<0.010). The sensitivity of diagnosis of upper gastrointestinal perforation base on the presence of hepatic portal free gas was 84.8% and the specificity 71.4%. Further, the sensitivity of diagnosis of lower gastrointestinal perforation base on the presence of mesenteric interspace free gas was 80.0% and the specificity 91.3%. The rates of presence of free gas in the subdiaphragmatic area, mid-abdominal wall, and pelvic cavity did not differ significantly between the two groups (all P>0.05). Receiver operating characteristic curves showed that when free gas was present in four or more of the studied locations in the abdominal cavity, the optimal cutoff for perforation diameter was 2 cm, the corresponding sensitivity 66.7%, and the specificity 100%, suggesting that abdominal free gas diffuses extensively when the diameter of the perforation is >2 cm. Another model revealed that when free gas is present in three or more of the studied locations, the optimal cutoff for perforation diameter is 1 cm, corresponding to a sensitivity of 91.7% and specificity of 76.2%; suggesting that free gas is relatively confined in the abdominal cavity when the diameter of the perforation is <1 cm. Conclusion: Identifying which of five locations in the abdominal cavity contains free intraperitoneal air by examining MSCT images can be used to assist in the diagnosis of the location and size of acute gastrointestinal perforations.

Numerical investigation of production characteristics and interlayer interference during co-production of natural gas hydrate and shallow gas reservoir

The coexistent system of natural gas hydrate and shallow gas (NGH-SG) enhances stability compared to single resource reservoirs, rendering it a promising target for co-production and commercial exploitation. In this study, we established a reservoir model of the NGH-SG system based on actual geological conditions. Subsequently, a long-term production simulation was performed to contrast the production behaviors of three exploitation methods: co-production of NGH-SG (CP), single production of hydrate-bearing layer (SP-HBL), and single production of shallow gas layer (SP-SGL). The study revealed that the presence of free gas in SGL can significantly increase the overall gas production capacity, with SGL contributing over 85% of the total gas production during the entire co-production period. On the 5000th day, the cumulative gas production of CP exceeded that of SP-SGL by 1.07 times and surpassed SP-HBL by 9.60 times. Furthermore, the study extensively investigated the impact of interlayer permeability on production behaviors. Lower interlayer permeability was found to be more conducive to releasing the natural gas production capacity from the reservoir. Notably, the phenomenon of interlayer interference should be carefully considered during CP. The influence degree of interlayer interference during CP becomes increasingly pronounced with increasing interlayer permeability. Fundamental contributors to interlayer interference encompass heat transfer, pressure diffusion, and interlayer cross-flow. As interlayer permeability rises, mass transfer between the layers intensifies, thus promoting pressure diffusion. Interlayer pressure difference and permeability are critical factors that affect interlayer cross-flow. For NGH-SG reservoirs with higher interlayer permeability, the advantages of CP are more obvious during the early production period. The implementation of the findings of this study may improve production efficiency and contribute to the development of effective management strategies for offshore NGH-SG reservoirs.

Methane-flow system within the Nyegga pockmark field, offshore mid-Norway

We investigated fluid seepage within the Nyegga pockmark field (600–900 m water depths) off mid-Norway from Remotely Operated Vehicle dives at the so-called CNE sites (CNE01 to CNE17). The seafloor morphology of some of these features corresponds to pockmarks and adjacent ridges, with the latter being the focus of present seepage activity. These structures are underlain by chimneys above a gas-charged zone with, in some cases, a substantial body of hydrate-invaded sediment (down to 1.3 s in two-way travel time at CNE03). Present-day methane-rich fluid seepage through the seabed is indicated by chemosynthetic fauna, in particular Siboglinidae polychaetes (Oligobrachia haakonmobiensis webbi and Sclerolinum contortum), microbial mats and associated Rissoidae gastropod (Alvania sp.) grazers, and confirmed by measured in situ bottom-water methane anomalies, up to 2,130 nL/L. No free-gas bubble emissions were observed or acoustically identified. The presence of authigenic carbonates reveals past seepage with very low δ13C values (down to −58‰) indicating that the major source of carbon was methane carried by the venting fluids. The ages of major periods of methane venting are provided by vesicomyid bivalve shells (Isorropodon nyeggaensis) present in two sedimentary layers, 14,930 and 15,500 14C yr BP (ca. 17,238 and 17,952 cal yr BP), respectively, corresponding to the time of Melt Water Pulse IA. The seafloor morphology and pattern of seepage -chemosynthetic fauna and microbial mat distribution and dissolved methane concentration-are remarkably heterogeneous. Pore-water chemistry profiles in a gravity core taken only 40 m from major seepage sites indicate no seepage and anaerobic methane oxidation at a sub-bottom depth of about 2 m. Present-day seepage from the studied pockmark-chimney fluid-flow system charged with gas hydrate is dominated by the advection of methane solution in pore water. Some of this methane could result from the dissolution of hydrate in the chimney, most of which would have formed during an earlier period (post-LGM times) of history of the chimney, when it was venting free gas. However, the presence of free gas beneath this chimney is probably why the water entering the chimney is already saturated with methane and the process of hydrate formation in the chimney continues today.

Clinical Profile and Management of Perforation Peritonitis in a Tertiary Care Centre, Kerala, India

Peritonitis, an inflammation of the peritoneum and peritoneal cavity, is often brought on by a localised or systemic infection. Primary and secondary peritonitis are the two types of peritonitis. Once the clinical diagnosis of peritonitis is made, rapid institution of both physiologic support and aggressive anti-infective therapy are imperative. The objective was to study the frequency of perforation peritonitis in relation to various parameters ,and to study the post-operative complications and mortality. Cross-sectional study was conducted during the time period of 1 year. Findings were noted intra-operatively, patients were followed up until discharge or death. It was found that males were more affected than females, and majority was in the 21-35 years age group. Most common perforation was appendicular perforation followed by gastric and small intestine perforation. Diagnosis is made clinically and confirmed by presence of free gas under diaphragm. Mortality was 10% and the most common post-operative complication was wound infection.

Gastroinstestinal Fistula in Acute Necrotising Pancreatitis with Septicaemia: A Case Report

Acute Pancreatitis (AP) is an inflammatory condition with cumbersome side effects. Gastropancreatic (GI) fistula is a rare complication seen in cases with infected pancreatic or peripancreatic necrosis. GI fistulas can result in severe haemorrhage and septicemia. Hereby, the authors present a case of 36-year-old male with a chief complaint of abdominal pain associated with abdominal distension and non bilious vomiting after binge consumption of alcohol for the past 10 days. Computed Tomography (CT) scan showed the presence of free gas in the abdomen. Contrast-Enhanced CT (CECT) imaging revealed diffuse enlargement affecting the head, uncinate process, body, and tail of the pancreas. There were also a few necrotic peripancreatic fluid collections with extensive peripancreatic fat stranding. Based on these findings, the diagnosis of acute necrotising pancreatitis was suggested. Despite treatment with antibiotics and necrosectomy with drainage of the abscess collection, the patient showed no improvement. A repeat CECT examination was performed due to the deterioration of the patient’s clinical condition, which showed a complete non enhancing pancreas. Additionally, a large defect measuring approximately 16 mm was observed in the posteroinferior wall of the stomach at the middle third of the body, with extravasation of contrast material into the pancreatic collection, suggestive of fistula formation. Subsequently, the patient underwent pancreatic necrosectomy with closure of the gastric perforation using feeding jejunostomy. A follow-up CT examination was performed four days later due to the deteriorating status of the patient, as well as new onset haematemesis and bloody discharge from the surgical drain. The CT scan revealed a few peripancreatic soft tissue infiltrates adjacent to the pancreatic head. Persistent collections were noted along the anterolateral surface of the right psoas, extending to the adjoining right anterior pararenal space and the left anterolateral abdominal wall in the left hypochondriac region. Thickening of the bilateral lateroconal fascia and anterior and posterior renal fascia was observed, likely due to inflammation. Following this, the patient underwent another surgery, and percutaneous drainage was performed with antibiotic coverage. The patient showed a significant reduction in the collection and improved clinical condition after 10 days. Imaging plays a crucial role in diagnosing such complications, enabling early detection and reducing mortality in these patients.

Mathematical Modeling of Gas Hydrates Dissociation in Porous Media with Water-Ice Phase Transformations Using Differential Constrains

2D numerical modeling algorithms of multi-component, multi-phase filtration processes of mass transfer in frost-susceptible rocks using nonlinear partial differential equations are a valuable tool for problems of subsurface hydrodynamics considering the presence of free gas, free water, gas hydrates, ice formation and phase transitions. In this work, a previously developed one-dimensional numerical modeling approach is modified and 2D algorithms are formulated through means of the support-operators method (SOM) and presented for the entire area of the process extension. The SOM is used to generalize the method of finite difference for spatially irregular grids case. The approach is useful for objects where a lithological heterogeneity of rocks has a big influence on formation and accumulation of gas hydrates and therefore it allows to achieve a sufficiently good spatial approximation for numerical modeling of objects related to gas hydrates dissociation in porous media. The modeling approach presented here consistently applies the method of physical process splitting which allows to split the system into dissipative equation and hyperbolic unit. The governing variables were determined in flow areas of the hydrate equilibrium zone by applying the Gibbs phase rule. The problem of interaction of a vertical fault and horizontal formation containing gas hydrates was investigated and test calculations were done for understanding of influence of thermal effect of the fault on the formation fluid dynamic.

Monitoring the 2021 Mw 8.2 Alaska Earthquake by an Offshore Seismic and Fluid Pressure Observation Network and Implications for Ocean‐Crust Dynamic Coupling

AbstractGround shaking caused by earthquakes is accompanied by seafloor and sub‐seafloor formation fluid pressure variations in offshore areas, but there have been few collocated observations of these signals. In this work, we report seismic and high‐sampling‐rate fluid pressure records of the 2021 Mw 8.2 Alaska earthquake by the Ocean Networks Canada (ONC) NEPTUNE observatory at an epicentral distance of ∼2,200 km in the northeast Pacific Ocean. The system comprises observatory nodes in various tectonic environments, with each node including buried broadband seismometers, seafloor pressure sensors, and, at two nodes, borehole pressure sensors. Seismic and tsunami waveforms of the Mw 8.2 earthquake were documented in detail. Seismic seafloor pressure variations (Psf) were dominated by Rayleigh waves of periods between 5 and 50 s, with peak amplitudes of 3–4 kPa at most sites. Waveform similarity and the linear scaling between Psf and vertical ground acceleration indicate forced acceleration of the water column being dominant in governing Psf during long‐period surface‐wave arrivals, with an additional component of elastic oscillation occurring at higher frequencies (&gt;0.1 Hz) causing extra pressure signals. Analysis of formation pressure variations due to various types of ocean loading of distinctly different frequencies (e.g., tides, tsunami, and infragravity waves) shows stable one‐dimensional vertical loading efficiencies that depend on lithology at each borehole site, with loading response being strongly influenced by the presence of free gas at shallow depths within the Cascadia accretionary prism. Inter‐site comparisons of seismic and seafloor pressure waveforms demonstrate a key role of sediment thickness in the amplification of surface wave amplitudes.

Ocean Dynamics and Methane Plume Activity in Tatar Strait, Far Eastern Federal District, Russia as Revealed by Seawater Chemistry, Hydroacoustics, and Noble Gas Isotopes

This investigation presents methane, noble gas isotopes, CTD, and stable isotopic data for water samples collected in Niskin bottles at Tatar Strait during the spring seasons of 2015 and 2019 onboard the Russian R/V Akademik M.A. Lavrentyev. The results are compared to previous research carried out in 1999 in a nearby portion of the Strait and demonstrate that salinity and temperature can change appreciably. The CTD data from 1999 shows warm surface waters underlain by cold subsurface waters. In contrast, the 2015 data show the CTD data that show warm temperatures and high salinity extending down from the surface well into intermediate waters, while the 2019 data show cold surface waters underlain by even colder subsurface waters. CTD data collected above active gas plume sites along Sakhalin Island’s western shore show no substantial difference in temperature or salinity from the non-plume sites, and the methane concentrations at all of the measured sites are significantly above saturation, even in the shallow waters. Hydroacoustic data also suggest the presence of free gas and gas hydrate–coated methane bubbles from the seafloor at least to the base of upper intermediate waters. All of the intermediate and deep Japan Sea Proper waters in Tatar Strait still retain tritiogenic3He, similar to that observed throughout much of the Japan Sea, indicating limited vertical exchange between these layers and surface waters. An analysis of the δ13C of dissolved inorganic carbon in the seawater shows that positive values are limited to surface waters and that the waters become progressively more depleted in13C with depth. The results are consistent with research over the past several decades which has shown that ventilation of intermediate and deep Japan Sea Proper water is somewhat limited, while both the temperature and salinity of surface and subsurface water layers within the strait are sensitive to the balance between cold, less saline waters contributed by the Amur River/Primorye Current from the north and warm, saline waters contributed by the Tsushima Current from the south.

Investigation of the influence of the drive shaft speed on the characteristics of a submersible pump when pumping out a gas-liquid mixture

The article presents the results of small size ESP (electrical submersible pump) tests at a speed of 6000-8500 rpm in the presence of free gas at the inlet to the device. The submersible centrifugal pump is quite sensitive to the presence of free gas in the pumped gas-liquid mixture. Depending on the amount of free gas, the actual characteristics of the pump are deformed, and at a certain gas content, the pump stops supplying the gas-liquid mixture. Stable operation of the ESP is carried out with a free gas content at the pump inlet ranging from 5% to 25%, depending on the pump size. There are several ways to deal with gas in wells operated by ESP: from running the pump into the zone where the intake pressure ensures optimal pump flow and stable operation to the use of separating and dispersing devices at the intake. Results represent pump flow characteristics along with different inlet free gas contents.

New correlations for predicting two-phase electrical submersible pump performance under downhole conditions using field data

AbstractElectrical Submersible Pump (ESP) is one of the major Artificial Lift methods that is reliable and effective for pumping high volume of fluids from wellbores. However, ESP is not recommended for applications with high gas liquid ratio. The presence of free gas inside the pump causes pump performance degradation which may lead to problems or even failure during operations. Thus, it is important to investigate effect of free gas on ESP performance under downhole conditions. At present, existing models or correlations are based on/verified with experimental data. This study is one of the first attempts to develop correlations for predicting two-phase gas–liquid pump performance under downhole conditions by using field data and laboratory data. Field data from three oil producing wells provided by Strata Production Company and Perdure Petroleum LLC. as well as experimental data obtained from experimental facility at Production and Drilling Research Project—New Mexico Tech were used in this study. Actual two-phase pump differential pressure per stage is obtained from experiments or estimated from field data and was normalized using pump performance curve. The values are compared to pump performance curve to study the relationships between pump performance and free gas percentage at pump intake. Correlations to predict ESP performance in two-phase flow under downhole and experimental conditions was derived from the results using regression technique. The correlation developed from field data presented in this study can be used to predict two-phase ESP performance under downhole conditions and under high gas fraction. The results from the experimental data confirm the reliability of the developed correlation using field data to predict two-phase ESP performance under downhole conditions. The developed correlation using the laboratory data predicts quite well the two-phase pump performance at the gas fraction of less than 15% while it is no longer reliable when free gas fraction is more than 15%. The findings from this study will help operating companies as well as ESP manufacturers to operate ESPs within the recommended range under downhole conditions. However, it is recommended to use the proposed correlation on reservoirs with conditions similar to those of the three presented wells.

Growth pattern of dispersed methane hydrates in brine-saturated unconsolidated sediments via joint velocity and resistivity analysis

Although the different morphologies of methane hydrates have been identified in pore spaces, their growth mechanism has not yet been fully resolved. In this study, we performed two sets of experiments using dissolved methane in brine-saturated unconsolidated sediments composed of 95.5 wt% quartz sand and 4.5 wt% kaolin to simulate the formation of dispersed marine gas hydrates. The in situ ultrasonic velocities (VP and VS), electrical resistivity, and methane hydrate saturation (Sh) were simultaneously measured and were jointly analyzed and compared to elastic and electrical rock physics models of various hydrate morphologies in pore spaces to quantify the invisible dynamic evolution of the hydrates’ morphologies. The results indicate that the hydrate growth pattern is characterized by distinct stages as Sh increases. During the first set of experiments, the frame-strengthening morphology was dominant in all of the stages, the contact-cementing morphology occurred infrequently when Sh > 8%, and the pore-filling morphology gradually became identifiable when Sh > 25%. It is proposed that the frame-strengthening hydrates primarily grow on grain surfaces when Sh < 25%, then they extend toward the center of the pore, and finally they begin to plug the pores when Sh > 35%. In the second set of experiment, the geophysical responses were significantly affected by the presence of free gas, and the observed hydrate growth behavior was differed from that observed in the first set of experiments.

Assessing Spatio‐Temporal Variability of Free Gas in Surficial Cohesive Sediments Using Tidal Pressure Fluctuations

AbstractFrom a geohazard assessment perspective, the distribution, content, and dynamics of free gas in surficial sediment were addressed by imaging and monitoring the upper 15 m beneath the shelf offshore Nice, France. Based on high‐resolution seismic data covering three sites where pore pressure was recorded over three and a half years, the presence of free gas was determined in the upper 2.75–14.75 m of cohesive, silty clay. Seismic velocity changes delineate two layers with gas volume fractions ranging from 0.12% to 1.89%. By considering the tidal response recorded by eight pore pressure sensors, estimates of gas volume fractions vary from 0.26% to more than 9.4% on a spatio‐temporal scale which cannot be achieved with seismic data. To depict spatio‐temporal patterns three types of free gas occurrence (FGO) were distinguished. Type 3 FGO uniquely showed sawtooth fluctuations in overpressure of 27%–45% of the hydrostatic effective stress as evidence of bubble growth and rise. The other two types showed long‐term overpressure trends indicative of a situation whereby bubble growth has ceased. Type 1 FGOs are distinguished from type 2 by their gas volume fraction lower than 9.4% and ratios of overpressure to hydrostatic effective stress lower than 0.3. Values higher than this threshold are considered sufficient for shear failure to initiate from the steep shelf edge (&gt;20°). Beyond site‐specific insights, the distinction of FGO from their overpressure levels yields testable implications for the dynamics of methane in sediments.

Identification of gas hydrates and bottom-simulating reflectors in far-offset seismic images

The presence of marine gas hydrates is routinely inferred based on the identification of bottom simulating reflectors (BSRs) in common-depth-point (CDP) seismic images. Additional seismic studies such as amplitude variation with offset (AVO) analysis can be applied for corroboration. Although confirmation is needed by drilling and sampling, seismic analysis has proven to be a cost-effective approach to identify the presence of marine gas hydrates. Single-channel far-offset seismic images are investigated for what appears to be a more reliable and cost-effective indicator for the presence of BSRs than traditional CDP processing or AVO analysis. A nontraditional approach for processing seismic data is taken to be more relevant to imaging the gas/gas hydrate contact. Instead of applying the traditional CDP seismic processing workflows from the oil industry, we more carefully review the significant amount of information existing in the data to explore how the character of the data changes as offset angle increases. Three cases from different environments are selected for detailed analysis. These include (1) stratigraphy running parallel with the ocean bottom, (2) a potential BSR, running parallel to the ocean bottom, and cross-cutting dipping reflections, and (3) a suspected thermal intrusion without a recognizable BSR. This investigation considers recently collected multichannel seismic data from the deep waters of the central Aleutian Basin beneath the Bering Sea, the preprocessing of the data sets, and the methodology for processing and display to generate single-channel seismic images. Descriptions are provided for the single-channel near- and far-offset seismic images for the example cases. Results indicate that BSRs related to marine gas hydrates, and originating due to the presence of free gas, are more easily and uniquely identifiable from single-channel displays of far-offset seismic images than from traditional CDP displays.

In-situ borehole temperature measurements confirm dynamics of the gas hydrate stability zone at the upper Danube deep sea fan, Black Sea

Coring, geophysical logging, and in-situ temperature measurements were performed with the MARUM-MeBo200 seafloor rig to characterize gas hydrate occurrences in sediments of the Danube deep sea fan, off Romania, Black Sea. The new drilling data showed no evidence for significant gas hydrate saturations within the sediments but the presence of free gas at the depth of the bottom-simulating reflector (BSR). In-situ temperature and core-derived geochemical data suggest that the current base of the gas hydrate stability zone (BGHSZ) is ∼20 m shallower than the BSR. Investigation of the seismic data around the drill sites shows several locations where free gas previously trapped at a former BGHSZ migrated upwards forming a new reflection above the BSR. This shows that the gas hydrate system in the Danube deep sea fan is still responding to climate changes initiated at the end of the last glacial maximum.

Effects of gas occurrence pattern on distribution and morphology characteristics of gas hydrates in porous media

Natural gas hydrates have attracted much attention in recent years. It is important to investigate the effects of gas occurrence pattern on hydrate growth habits since distribution and morphology characteristics of gas hydrates have significant effects on physical properties of hydrate-bearing reservoirs. In this work, the differences in distribution and morphology properties of gas hydrates under two gas occurrence patterns have been analyzed via the X-ray computed tomography for the first time. Experimental results reveal direct correlations between the hydrate growth habit and the gas occurrence pattern. In the presence of free gas, grain-attaching hydrates are formed at the arc-shaped contact surface of gas and water, and mass transfer at the gas-water interface is the key controlling factor in hydrate formation process. In the presence of dissolved gas, dispersed and dendritic hydrates are formed in liquid phase as the result of gas solubility change, and gas diffusion is the crucial factor that influences the growth habit and morphology of gas hydrates during hydrate formation from dissolved gas. Besides, the maximum saturation of dendritic hydrates formed from dissolved gas is limited by the gas solubility. These conclusions are valuable in the improvement of prediction accuracy of gas production from hydrate-bearing sediments.

Characterization of gas accumulation at a venting gas hydrate system in the Shenhu area, South China Sea

Bottom-simulating reflections (BSRs) in seismic data have been widely accepted to indicate the base of the methane gas hydrate stability zone (MGHSZ), and free gas was thought to exist only below it. However, real geologic systems are far more complex. We have evaluated the results of 3D seismic, logging while drilling, in situ, and coring measurements at a venting gas hydrate system in the Shenhu area of the South China Sea. Our studies reveal that free gas has migrated upward through the thermogenic gas hydrate stability zone into the MGHSZ and become a part of the gas hydrate system. Seismic amplitude anomalies and core results suggest the presence of free gas above the base of MGHSZ at 165 mbsf and the presence of thermogenic gas hydrates below it in well SC-W01. Analyses of P-wave velocity, S-wave velocity, density, and porosity logs reveal that free gas occurs above and below the MGHSZ as well. Integrating log and core analysis with seismic interpretation suggests that the variation in seismic amplitude within the chaotic zone is associated with variable gas saturations, and a large amount of methane and thermogenic gases accumulate near the complex BSRs. We suggest that relative permeability likely plays a significant role in the free-gas distribution and the formation of gas hydrates within a venting gas hydrate system, whereas the effect of dissolved gas short migration is not ignored. Our results have important implications for understanding the accumulation and distribution of gas hydrates and free gas in the venting gas hydrate system and seeps at the seafloor.

Study of factors affecting mortality and morbidity in patients presenting with peritonitis due to duodenal ulcer perforation

Background: Peptic ulcer disease in the general population had lifetime prevalence of 5-10% with incidence of 0.1–0.3% per year. Despite the tremendous improvement in preventive therapies, the rate of complication of this disease is still high and is burdened by high morbidity and mortality. In present study, we aimed to study factors affecting mortality and morbidity in patients presenting with peritonitis due to duodenal ulcer perforation at our tertiary hospital. Material and Methods: Present study was single-center, prospective, observational study conducted in patients admitted, diagnosed with duodenal ulcer perforation and surgically treated at our hospital. Results: In present study period total 56 patients were studied. All were male, most common age group was 51-60 years (37.5%) followed by 41-50 years (23.21%). Duration from onset of symptoms to admission was &gt;24 hours (30.36%) in most of patients followed by 12-24 hours (28.57%). Most commons symptoms were pain in abdomen (100%), vomiting (100%). Anaemia (37.5%), LRTI and Pulmonary complications (19.64%), Diabetes mellitus (12.5%) and Hypertension (10.71%) were common comorbidities noted. Associated risk factors were previous history of PUD (41.07%), Alcohol use (64.29%), Cigarette smoking (51.79%) and Use of NSAIDs (12.5%). Presence of free gas under diaphragm was noted in 83.93% patients. Intraoperatively duodenal perforation diameter was 1–5 mm (60.71%) in most of patients followed by 6–10 mm (23.21%). Only 1 patient had duodenal perforation diameter was &gt; 20mm. Common postoperative complications were wound infection (37.5%) and pulmonary infection (21.43%). In present study mortality within 1 month was noted in 13 patients (23.21%). Most common factors related to mortality were delayed presentation &gt; 24 hours (61.54%), age &gt; 60 years (46.15%), diabetes mellites (38.46%), Size of perforation &gt; 1 cm (38.46%) and septicaemic shock (23.08%). Conclusion: Delayed presentation &gt; 24 hours, age &gt; 60 years size of perforation &gt; 1 cm were common factors related to mortality in duodenal ulcer perforation patients.

Widespread Subcutaneous Emphysema After J-Plasma Therapy

Subcutaneous emphysema refers to the abnormal presence of free gas within the subcutaneous tissue. Its cause can be broadly classified into 3 main causes: (1) infection by gas-forming microorganisms, (2) visceral perforation of luminal organs, and (3) spontaneous alveolar rupture. We report a case of a 48-year-old lady who developed extensive subcutaneous emphysema after undergoing VASER-assisted liposuction and J-Plasma® therapy at a local cosmetic clinic. The patient was admitted to our tertiary plastic surgery department where she was managed conservatively and discharged at day 3 without any complications. Subcutaneous emphysema is a known but rare complication of liposuction. While subcutaneous emphysema is usually self-limiting, fatal complications can occur. As such, patients considering these procedures should be informed of its risks and benefits to allow them to make an informed decision. This report highlights the importance of meticulous surgical technique in liposuction and its postoperative assessment.

Effect of cavitation and free-gas entrainment on the hydraulic performance of a centrifugal pump

An experimental study on gas–liquid two-phase flow characteristics in a low-specific-speed centrifugal pump is presented via employing multiple investigation techniques, such as visualization observation, measurements of acoustic emission and vibration, etc. Specially, three different flow conditions were inspected, namely gas locking initiation, critical cavitation with/without free-gas presence, etc. For gas locking, the drastic deterioration of the pump performance and the disrupted balance of shaft were observed. Especially, at low rotational speeds, the gas locking accompanied with intermittent or churn flow can be triggered by even lower inlet gas volumetric fractions. When it came to the cavitation flow, a small amount of gas entrainment could induce the rapid deterioration of cavitation and stimulate much higher amplitude in low-frequency band of shaft rotation. The relationship between the gas bubble trajectory and the vibration level under the backflow is discussed. The results reveal that the combined effect of the free-gas entrainment and cavitation on the pump instability is much stronger than that under natural cavitation or free-gas entrainment flow, whose fault diagnosis can be determined by the data manifested in different spectral segments.