Gas Accumulation Research Articles

Extensive glacitectonism and rapid deglacial fluid expulsion in the northeastern Barents Sea

High-latitude regions store large amounts of carbon trapped by ice sheets, permafrost and gas hydrates, yet joint evolution of these climate components is poorly understood. Covered by a cold-based ice-sheet during the last glaciation, the seafloor of the northeastern Barents Sea reveals one of the largest known glacitectonic provinces in the Arctic. Up to 200-m high glacitectonic landforms are cratered and overlie faults associated with ‘bright spots’ indicative of subsurface gas accumulations. However, sediment samples show low pore gas concentrations and no present-day gas seepage. We combine new observations and ice-sheet - hydrate modelling to propose that during the Late Weichselian, glacitectonism was caused by patchy substrate stiffening due to gradual growth of subglacial gas hydrates and permafrost. Ice decay led to rapid destabilisation and full drainage of shallow hydrate reservoirs and permafrost thaw, causing craterisation which was likely accompanied by large fluxes of carbon released into the water column. This study shows that these processes were more widespread across glaciated margins, also highlighting sensitivity and potential for abrupt changes of high-latitude carbon pools in response to complex interactions between the cryosphere, ocean, and solid earth.

Immobilization of carbonic anhydrase on bentonite – chitosan composite and determination of its kinetic parameters and CO2 removal capacity

Greenhouse gas accumulation in the atmosphere resulting from industrialization and human activities is accepted as the main cause of climate change. Increasing temperatures by greenhouse gases have severe effects on meteorological and climatic events along with reduced available water resources. Carbon dioxide (CO2) is known as the most serious anthropogenic greenhouse gas in the atmosphere. In recent years the systems prepared by immobilizing carbonic anhydrase enzymes using CO2 as a substrate on some matrices are predominantly preferred. In this study, the bentonite-chitosan composite material was prepared as immobilization surface. The hCA I purified from human erythrocytes was immobilized onto the composite material by glutaraldehyde-mediated cross-linking technique. Immobilized hCA I retained 87.5 % of its initial activity 30 days of incubation at 4°C. Besides, after 12 cycles of use the relative activity was 89.1 %. In addition, the CO2 removal capacity of immobilized hCA I was found as 7.41±0.95 mg CaCO3/mg hCA I with CaCO3 precipitation method. These results show that our novel composite hold a great potential as a CO2 removal tool.

Origin of horsetail faults in an extensional regime using physical experiments for the Linnan Sag

Horsetail faults and rotational faults, which maintain slight differences, are all important identity markers for strike-slip movement. However, it is difficult to explain why horsetail faults also appear in the extensional regime. Using the Linnan Sag as a reference, physical experiments are conducted to reproduce the formation processes of horsetail faults in the extensional regime. Characteristics of these horsetail faults include: (1) horsetail faults are the product of strain superposition during two phases of noncoaxial extension; (2) preexisting faults generated in the initial stage may reactivate by the combined elongation of dip-slip motion, followed by oblique-slip faulting at the middle-late stage, thus becoming the principal fault of the horsetail faults; this initial distance is obviously less (approximately 46%) than its distance during the middle-late stage; (3) a large number of new dip-slip faults appear at the tip of the principal fault in the middle-late stage, spatially connecting with the principal fault to form the horsetail faults; and (4) other preexisting faults that intersect the principal fault are not necessary for forming the horsetail faults but their presence may make the principal fault prone to segmentation. Therefore, although horsetail faults in the extensional and strike-slip regimes are similar in shape, their formation conditions and fault properties are very different. Understanding the characteristics of the horsetail faults in the extension regime contributes to further study related to oil and gas migration and accumulation in the Petroliferous basin.

The search for petroleum in the Sultanate of Oman – the first 120 years

This is a story of failure and success, of disappointment and elation. World wars, a market glutted with cheap oil and geologists unable to access areas of interest hampered the search. Early expeditions provided the first maps of the mountains and Dhofar, and glimpses of the geology of the interior, but no evidence of oil. Geological and geophysical surveys began in earnest in the 1950s, leading to the first exploratory drilling and the discovery of heavy oil at Marmul. Commercial oil was discovered a few years later at Fahud and Natih. All Oman's largest oilfields were found over the next 20 years based on 2D seismic data. Early concessions were large and ill-defined. More companies became involved as interest grew in exploration offshore and as acreage was relinquished onshore. Although gas was encountered as a byproduct of oil activities, exploration for gas did not begin until 1984 when it became apparent that the known accumulations were insufficient for future needs. Large accumulations of gas and condensate were subsequently discovered in central Oman. Petroleum continues to underpin the economy of the Sultanate as it strives to diversify and decarbonize. Useful lessons can be learned from the search so far.

Geological and geochemical characterization of caprock integrity in the Athabasca oilsands region

Caprocks play a pivotal role in petroleum systems for the accumulation of oil and gas, as well as in processes such as steam injection for heavy oil recovery and geological storage of CO2. In this study, the geological and geochemical characteristics of the caprock from the Cretaceous Wabiskaw Member (Mbr.) and overlying Clearwater Formation (Fm.), situated above the Athabasca oil sand region, were thoroughly examined using core samples obtained from well 1-22-90-14W4. Through HAWK programmed pyrolysis and solvent extraction, the caprock succession was revealed to exhibit limited organic content with total organic carbon content < 2.0 wt% and extractable organic matter (EOM) < 200 ppm. Further analysis using gas chromatography-flame ionization detector and gas chromatography-mass spectrometry on EOM unveiled insights into the mixing dynamics between the underlying oil reservoir and the caprock indigenous materials. Distinct trends in the ratios of low molecular weight (LMW) aromatic hydrocarbons, N-shielded carbazole, benzo[c]carbazole, and concentrations of carbazoles and benzocarbazoles were evident within a 5-m distance from the caprock-reservoir contact, indicating significant fractionation among compounds. Enrichment of these compounds was observed in the shale of the Wabiskaw Mbr., with a reversal of trends occurring within the initial 5 m into the overlying shale of the Clearwater Fm., suggesting limited oil penetration into the shale. The main Clearwater Fm. caprock succession was characterized by a dominance of immature, indigenous terrigenous organic matter, along with background concentrations of carbazole and benzocarbazole and an absence of N-shielded and/or LMW compound preferences. This composition starkly differed from the oil found in the underlying reservoir. The presence of calcareous cements in the Clearwater Fm. shale, approximately 5 m above the base, characterized by high bulk density (with 62% siderite), low porosity, and matrix permeability, contributed significantly to enhancing the sealing capacity of the caprock. The overall results provide compelling evidence that vertical oil leakage from the McMurray Fm. reservoir through the overlying shale of the Clearwater Fm. has not occurred during the post-lithification history with exception of the lower-most 5 m. The clay-rich argillaceous units identified in this study emerge as potential candidates for serving as effective caprock seals for steam injection and CO2 storage.

Application of multicomponent seismic data to tight gas reservoir characterization: A case study in the Sichuan Basin, China

Combining PP and PS waves from multicomponent data is an effective hydrocarbon characterization strategy because these two wave types are sensitive to different subsurface properties. We develop a case study using multicomponent data to characterize tight sandstone gas reservoirs in the Jurassic Shaximiao Formation, the western Sichuan Basin, China. In the study area, with PP data it is difficult to distinguish sandstones, mudstones, and gas sand, whereas recently acquired multicomponent data indicate potential for the joint characterization of lithology, porosity, and gas saturation from the combination of PP and PS reflections. Sandstones and mudstones have small P-wave velocity contrasts and large S-wave velocity contrasts. Thus, PS data provide a more accurate description of sandstones, as a substantial proportion of sandstones are undetectable from PP sections. P impedance is sensitive to sandstone porosity variation, and seismic-predicted porosities based on impedance inversion are in good agreement with log-interpreted porosities. The ratio of P-wave velocity to S-wave velocity is sensitive to gas accumulation, and the ratios derived from joint PP-PS prestack inversion are determined to be better than from PP prestack inversion in terms of their agreements with logs and distinct gas-sand boundaries.

Nephrectomy for emphysematous pyelonephritis in a nonfunctional renal allograft due to rejection after kidney transplantation

BackgroundEmphysematous pyelonephritis represents an acute and necrotizing infection characterized by the accumulation of gas within the kidney. This condition poses a swift progression toward sepsis, leading to a poor prognosis. We experienced a rare case of emphysematous pyelonephritis in a nonfunctioning renal allograft attributed to antibody‐mediated rejection after kidney transplantation.Case presentationA 71-year-old man with diabetes had undergone living-donor renal transplantation from his wife. Unfortunately, the transplanted kidney’s function declined due to antibody-mediated rejection, necessitating the introduction of hemodialysis 12 months post-transplantation. Subsequently, 4 months after initiating hemodialysis, the patient presented with pain and swelling in the right lower abdomen. A computed tomography scan revealed the enlargement of the transplanted kidney and gas formation. This constellation of symptoms led to the diagnosis of emphysematous pyelonephritis, resulting in his hospitalization. Further contrast-enhanced computed tomography scans demonstrated an absence of arterial flow and ischemia within the renal allograft. Despite antibiotic treatment and percutaneous drainage, both the gas and fluid in the renal parenchyma and surrounding tissue displayed minimal reduction. Given these compelling findings, an allograft nephrectomy was performed 20 days into his hospital stay. Pathological examination confirmed complete allograft necrosis, revealing nonviable renal parenchyma. The patient’s postoperative recovery progressed favorably.ConclusionsInstances of emphysematous pyelonephritis within transplanted kidneys are infrequently documented. Among these cases, emphysematous pyelonephritis in a nonfunctioning renal allograft is very rare and may be associated with graft ischemia and the presence of injured tissue. The determination of an immediate diagnosis and surgery is important.

Dynamics of gas and greenhouse gases production during fermentation of barley silage with lactic acid bacteria

Greenhouse gases (GHGs) are generated during fermentation in silages, especially in barley silage. However, little is known regarding the dynamics of GHG production in silages during fermentation. In the present study, GHG accumulation and reduction were assessed in barley silage. Barley was harvested at the milk stage and ensiled without (CK) or with two commercial lactic acid bacterial (LAB) additives (L1 or L2). Gas and GHG (CO2, N2O, and CH4) production, fermentation quality, fermentation weight loss (FWL), and bacterial communities were analyzed at d 0, 1, 3, 6, 15, 35, and 90 after ensiling. Gas and GHG production rapidly increased in CK during the first 3 days and in L1 and L2 during the first day and then decreased (P < 0.05), and these values were higher in CK than in L1 and L2 from d 1 to d 35 (P < 0.05), with the peak production of gas and GHG observed at d 6 in CK and at d 3 in L1 and L2. Gas and GHG production were positively correlated with the count of Coliforms and the abundances of Enterobacter, Klebsiella, and Atlantibacter from d 0 to 6 (P < 0.05) but were negatively correlated with the abundances of Lentilactobacillus, Lactiplantibacillus, and Lacticaseibacillus from d 1 to 35 (P < 0.05). L1 and L2 had increasing pH and acetic acid (AA) and decreasing lactic acid after d 15 (P < 0.05). Lentilactobacillus in L1 and L2 dominated the bacterial communities from d 35 to 90 and correlated positively with pH and AA, and negatively with LA from d 6 to 90 (P < 0.05). FWL had a positive correlation with gas and GHG from d 1 to 35 (P < 0.05). The ensiling fermentation process can be divided into gas accumulation and reduction phases. Inoculation with LAB reduced gas and GHG production. The activities of enterobacteria were the main contributors to gas and GHG accumulation. Lentilactobacillus activity mainly caused deterioration of fermentation quality during the late fermentation phase. The GHGs generated in silage contributed to the FWL during fermentation.Graphical

Dry matter concentration, particle size distribution and sand presence in faeces from horses with and without colic

A study comprising 74 colic and 74 control horses admitted to an animal hospital was performed. Faecal samples were collected and analysed for dry matter concentration, particle size distribution using wet-sieving, and sand presence through a sand sedimentation test. Data on horse breed, age, gender and basic feeding variables was collected and analysed using χ2-tests. Faecal dry matter concentration, particle size distribution and sand score was compared between colic and non-colic horses, and between horses with different colic types, using one-way ANOVA. Results showed that colic and non-colic horse groups were similar in breed, age, gender and basic feeding variables. Faecal dry matter concentration, particle size distribution and sand score were similar among colic and non-colic horses. Horses diagnosed with “unknown colic cause” had higher proportion of particles >0.5 <1.0 mm size compared to horses with colic due to impactions in caecum or colon, torsion or gas accumulation (P<0.05), but this difference was very small and most likely not of biological importance. Faecal dry matter concentration and sand score were similar among horses with different types of colic. Increased knowledge of the composition of particles of different size in equine faeces may enhance our understanding of digesta passage rate in colic and non-colic horses, which is needed to develop preventative measures of certain types of colic.

Molecular Insight into the Processes and Mechanisms of N2 Adsorption and Accumulation at the Hydrophobic Solid/Liquid Interface.

In this study, molecular dynamics (MD) simulations were employed to elucidate the processes and underlying mechanisms that govern the adsorption and accumulation of gas (represented by N2) at the hydrophobic solid-liquid interface, using the GROMACS program with an AMBER force field. Our findings indicate that, regardless of surface roughness, the presence of water molecules is a prerequisite for the adsorption and aggregation of N2 molecules on solid surfaces. N2 molecules dissolved in water can cluster even without a solid substrate. In the gas-solid-liquid system, the exclusion of water molecules at the hydrophobic solid-liquid interface and the adsorption of N2 molecules do not occur simultaneously. A loosely arranged layer of water molecules is initially formed on the hydrophobic solid surface. The two-stage process of N2 molecule adsorption and accumulation at the hydrophobic solid/liquid interface involves initial adsorption to the solid surface, displacing water molecules, followed by N2 accumulation via self-interaction after saturating the substrate's surface. The process and underlying mechanisms of gas adsorption and accumulation at hydrophobic solid/liquid interfaces elucidated in this study offer a molecular-level understanding of nano-gas layer formation.

Overall Design of a Gradient‐Ordered Membrane Electrode Assembly for Direct Liquid Fuel Cells

AbstractThe direct liquid fuel cell (DLFC) constitutes a promising energy conversion system that directly conveys the chemical energy of liquid fuels into electrical energy. In certain DLFCs, gas is produced as a product of electrochemical reactions during operation. However, the accumulation of gas inside the porous electrode can significantly hinder the transport of reactants, leading to the failure of active sites and severe concentration loss. To address this issue, a gradient‐ordered membrane electrode assembly (MEA) is designed and fabricated, consisting of a dual‐gradient diffusion layer that comprises a pore‐size gradient and a wettability gradient as well as a catalyst layer constructed by nanoneedle catalyst. This MEA promptly removes the produced gas and delivers the fresh solution, thereby enhancing the cell power output and stability. The fuel cell with the gradient‐ordered MEA achieves a remarkable peak power density of 177 mW cm−2 and a discharging time of 19 h, which are more than four times and 30 times, respectively, higher than those of the conventional MEA.

Study of Effects on Performances and Emissions of a Large Marine Diesel Engine Partially Fuelled with Biodiesel B20 and Methanol

The impact of fossil fuel utilisation in different combustion systems on climate change due to greenhouse gas accumulation in the atmosphere is rather evident. A part of these gases comes from the large engines used for propulsion in marine applications. In the continuous global effort made by engine manufacturers to mitigate this negative impact, one way is represented by the utilisation of alternative fuels such as biodiesel and methanol, based on dedicated research to fulfil the more stringent regulations concerning pollutant emissions issued by piston heat engines. In this study, a numerical investigation was conducted on a four-stroke large marine diesel engine (ALCO 16V 251C) at several engine speeds and full load conditions. Different blends of diesel–methanol and biodiesel B20–methanol with methanol mass fractions of 10% and 20% were considered for theoretical analysis in two techniques of methanol supply: direct injection mode of a blend of base fuel diesel/biodiesel B20 with methanol and injection of methanol after the intercooler, and direct injection of the base fuel. The results show that, if 10% in power loss can be acceptable, then for diesel–methanol 10%, in the direct injection technology, the NOx emission can be reduced up to 19%, but with a compromise of an 8% increase in SOOT emission, while for biodiesel B20–methanol 10%, with the same direct injection method, the NOx emissions increase by up to 58% with the benefit of reducing SOOT by up to 23% relative to the original diesel fuel operation. For a 20% methanol fraction in blend fuel, the drop in power is more than 10% regardless of the method of methanol supply and the base fuel, diesel, or B20 used.

Characterization and fractal characteristics of nano-scale pore structure in shale gas reservoirs: a case study of the deep Longmaxi Formation, Zigong region, Southern Sichuan Basin, China

Taking the Longmaxi deep-marine shale gas reservoir in Zigong region as the research target, this paper aimed to characterize the nano-scale pore structure and investigate the reservoirs’ heterogeneity based on fractal theory. By conducting a series of experimental studies, mainly including TOC, XRD, gas adsorption (N2 and CH4), we were able to clarify the main controlling factors for the heterogeneity of deep shale pore structure. Our results indicated that the deep marine shale possessed a significant amount of organic matter, as the average TOC value is 3.68%. The XRD analysis results show that quartz and clay were the main mineral types, and the total content of these two minerals averaged 77.5%. Positive correlations were observed between TOC and quartz, while TOC decreases as the clay mineral increases, this discovery indicating that quartz is biogenic. Based on FHH (Frenkele-Halseye-Hill) method, by using the LTNA adsorption isotherms, we took relative pressure P/P0=0.5 as the boundary, then two separate fractal dimension were deduced, D1 and D2 represent the fractal characteristics of small and large pores, respectively. Our study revealed that both D1 and D2 demonstrated positive correlations with N2 adsorption pore volume and adsorption specific surface area, while negatively correlated with the adsorption average pore diameter. Moreover, the two fractal dimensions showed positive associations with TOC and quartz and negative associations with clay. Additionally, D1 and D2 also demonstrated a positive correlation with Langmuir volume. The presence of micropores was found to significantly influence the formation of an irregular pore structure in shale. As the pore size decreased, the adsorption specific surface area increased, resulting in a more intricate pore structure, and the fractal dimension of the pores elevated, ultimately. This intricate structure is beneficial for the accumulation of shale gas. These research findings offer valuable insights for the comprehensive assessment of deep shale gas, and enrich our knowledge of enrichment mechanisms in deep shale gas reservoirs.

A tree peony RING-H2 finger protein, PsATL33, plays an essential role in cold-induced bud dormancy release by regulating gibberellin content.

Bud dormancy is crucial for woody perennial plants to resist low-temperature stress in winter. However, the molecular regulatory mechanisms underlying bud dormancy release are largely unclear. Here, a tree peony (Paeonia suffruticosa) transcript ARABIDOPSIS TOXICOS EN LEVADURA 33 (PsATL33), encoding a RING-H2 finger protein, was selected from previously generated RNA sequencing data of chilling-treated buds. The objective of this study is to investigate the role of PsATL33 in the regulation of cold-induced bud dormancy release. Subcellular localization assay revealed that PsATL33 was localized to the nucleus and plasma membrane. Reverse transcription-quantitative PCR analysis showed that PsATL33 was dramatically upregulated during cold-triggered bud dormancy release. Exogenous treatments with gibberellin (GA3) increased, but abscisic acid (ABA) inhibited the transcription of PsATL33. Ectopic transformation assay indicated that overexpression of PsATL33 in petunia promoted seed germination, plant growth, and axillary bud break. Silencing of PsATL33 in tree peony through virus-induced gene silencing assay delayed bud dormancy release. tobacco rattle virus (TRV)-PsATL33-infected buds exhibited reduced expression levels of dormancy break-related genes EARLY BUD-BREAK 1 (PsEBB1) and CARBOXYLESTERASE 15 (PsCXE15). Silencing of PsATL33 decreased the accumulation of bioactive GAs, GA1 and GA3, rather than ABA. Transcript levels of several genes involved in GA biosynthesis and signaling, including GA20-OXIDASE 1 (PsGA20ox1), GA3-OXIDASE 1 (PsGA3ox1), PsGA3ox3, GA2-OXIDASE 1 (PsGA2ox1), and GA-INSENSITIVE 1A (PsGAI1A), were changed by PsATL33 silencing. Taken together, our data suggest that PsATL33 functions as a positive regulator of cold-induced bud dormancy release by modulating GA production.

Numerical investigation of the influence of the heat exchange structure on the gas-liquid dispersion in a large-scale fermenter

A combination of computational fluid dynamics (CFD) and population balance model (PBM) was used to study the gas-liquid mixing conditions in a fermenter. The effects of the heat exchange structure on the flow structure, gas holdup, agitator power, bubble size distribution and interfacial area were investigated by numerical simulations. The simulation results showed that radial gas dispersion and liquid penetration are strongly hindered by the spiral heat exchanger, as there is no gap between the annular tubes at the circumference. An unstable flow structure, gas accumulation around the shaft and gas leakage, as well as large bubbles around the heat exchange tubes are due to the poor gas distribution. By increasing the spacing of heat exchange tube bundles in circumferential, the gas-liquid mixing in the fermenter is gradually improved with the uniform row heat exchanger, the compact row heat exchanger and the bundle type heat exchanger. The bundle heat exchanger acts as a baffle to suppress the large bubbles and effectively reduce the bubbles sizes and promote gas dispersion, which exhibits the maximum interfacial area and interfacial area per unit power. Compared to the fermenter with a spiral heat exchanger, the interfacial area and interfacial area per unit power of the fermenter with a bundle heat exchanger increase by 36.5 % and 9.1 %, respectively.

Whole petroleum system in Jurassic coal measures of Taibei Sag in Tuha Basin, NW China

Based on the latest results of near-source exploration in the Middle and Lower Jurassic of the Tuha Basin, a new understanding of the source rocks, reservoir conditions, and source-reservoir-cap rock combinations of the Jurassic Shuixigou Group in the Taibei Sag is established using the concept of the whole petroleum system, and the coal-measure whole petroleum system is analyzed thoroughly. The results are obtained in three aspects. First, the coal-measure source rocks of the Badaowan Formation and Xishanyao Formation and the argillaceous source rocks of the Sangonghe Formation in the Shuixigou Group exhibit the characteristics of long-term hydrocarbon generation, multiple hydrocarbon generation peaks, and simultaneous oil and gas generation, providing sufficient oil and gas sources for the whole petroleum system in the Jurassic coal-bearing basin. Second, multi-phase shallow braided river delta–shallow lacustrine deposits contribute multiple types of reservoirs, e.g. sandstone, tight sandstone, shale and coal rock, in slope and depression areas, providing effective storage space for the petroleum reservoir formation in coal-measure strata. Third, three phases of hydrocarbon charging and structural evolution, as well as effective configuration of multiple types of reservoirs, result in the sequential accumulation of conventional-unconventional hydrocarbons. From high structural positions to depression, there are conventional structural and structural-lithological reservoirs far from the source, low-saturation structural-lithological reservoirs near the source, and tight sandstone gas, coal rock gas and shale oil accumulations within the source. Typically, the tight sandstone gas and coal rock gas are the key options for further exploration, and the shale oil and gas in the depression area is worth of more attention. The new understanding of the whole petroleum system in the coal measures could further enrich and improve the geological theory of the whole petroleum system, and provide new ideas for the overall exploration of oil and gas resources in the Tuha Basin.

Evolution of a late Quaternary succession by interpretation of high‐resolution seismic and bathymetric data, Adriatic Sea

AbstractThis paper presents the results of the interpretation of a set of high‐resolution seismic lines integrated with multibeam echosounder data acquired in a coastal area in the Northern Adriatic Sea. The aim of the study was to reconstruct the stratigraphic evolution of a late Quaternary sedimentary succession offshore the town of Bibione, North‐Eastern Italy, by recognising the key unconformities, identifying the main depositional units, dating them and reconstructing the depositional environments in relation to relative sea‐level variations. Specifically, four sedimentary units, separated by erosional unconformities associated with the development of deep channels, were identified and dated based on literature information. By interpreting the seismic data, sedimentary dynamics were reconstructed and palaeoenvironments identified. The lower unit corresponds to a paludal environment, showing abundant gas seeps and accumulations (bright spots); the two intermediate units correspond to fluvial deposits, filling the deep incisions that characterise the bounding surfaces. Finally, the shallowest unit, bounded by a wave‐ravinement surface incised by tidal currents, corresponds to the Holocenic progradation of the coastal wedge. In addition, several vertical gas chimneys were identified, ranging in width from a few metres to 20–30 m. These were present in all units, often reaching the sea floor. Finally, elongated mounds, about 300 m wide, at the sea floor were recognised. The bathymetric and seismic characteristics of these elongated bodies and their relationship to adjacent sedimentary bodies suggest that they are probably methane‐derived carbonate formations known as ‘Trezze’ or ‘Tegnùe’. These names recall the fact that the trawls of the local fishermen were often hindered (‘tegnù’ in the Venetian language) or even cut off by these formations.

Main controlling factors and exploration enlightenment of aluminous rock series gas reservoirs in Ordos Basin, NW China

Based on the data of outcrop, core, logging, gas testing, and experiments, the natural gas accumulation and aluminous rock mineralization integrated research was adopted to analyze the controlling factors of aluminous rock series effective reservoirs in the Ordos Basin, NW China, as well as the configuration of coal-measure source rocks and aluminous rock series reservoirs. A natural gas accumulation model was constructed to evaluate the gas exploration potential of aluminous rock series under coal seam in the basin. The effective reservoirs of aluminous rock series in the Ordos Basin are composed of honeycomb-shaped bauxites with porous residual pisolitic and detrital structures, with the diasporite content of greater than 80% and dissolved pores as the main storage space. The bauxite reservoirs are formed under a model that planation controls the material supply, karst paleogeomorphology controls diagenesis, and land surface leaching improves reservoir quality. The hot humid climate and sea level changes in the Late Carboniferous–Early Permian dominated the development of a typical coal-aluminum-iron three-stage stratigraphic structure. The natural gas generated by the extensive hydrocarbon generation of coal-measure source rocks was accumulated in aluminous rock series under the coal seam, indicating a model of hydrocarbon accumulation under the source. During the Upper Carboniferous–Lower Permian, the relatively low-lying area on the edge of an ancient land or island in the North China landmass was developed. The gas reservoirs of aluminous rock series, which are clustered at multiple points in lenticular shape, are important new natural gas exploration fields with great potential in the Upper Paleozoic of North China Craton.

Влияние мелкозалегающего газа на проектные решения по освоению морских газоконденсатных месторождений на шельфе арк­тических и суб­арк­тических морей

The article discusses issues related to shallow gas influence on design decisions for the development of offshore oil and gas condensate fields. The authors show the presence and distribution of shallow gas accumulations in the upper part of the geological section and its influence on the quality of seismic surveys. The release of shallow gas has caused many serious accidents at offshore drilling rigs and oil and gas production platforms. The main danger of shallow gas deposits is when drilling intervals for the conductor and surface casing due to the lack of blowout equipment at the wellhead. The authors analyze the areal and depth distribution of shallow gas in the Arctic and subarctic seas, and find out that small deposits of several hundred meters in size are most common. The main methods of detecting and studying shallow gas accumulations above gas-bearing structures are high-resolution seismic exploration, drilling of engineering-geological wells and pilot holes with well logging. The researchers reveal the main features of the wave pattern indicating the gas saturation in the upper part of the section. They present the main technical solutions for the development of the Lunsky, Kirinsky and Yuzhno-Kirinsky oil and gas condensate fields located on the self of Sakhalin Island and suggest changes in design solutions during their development in view of the shallow gas presence in the upper part of the geological section. The authors substantiate the need to create Russian software systems and methods of automated design for developing offshore oil and gas fields in the Arctic, taking into account geological and geophysical uncertainty, the shallow gas presence and technical factors.

Vacuum Disc Phenomenon Turned Gassy Disc Herniation: A Case Report

BACKGROUND: The vacuum phenomenon is a radiologic finding that results from gas accumulation within degenerated discs, joints, or vertebrae. This gas can herniate, causing back pain and/or radiculopathy. Asymptomatic imaging abnormalities can be coincidental and/or non-concordant with clinical presentation therefore warranting close evaluation. CASE REPORT: This 45-year-old man, previously diagnosed with lumbar facet arthropathy, returned to the clinic for left-sided axial low back pain. Imaging revealed that a gas filled mass in the right lateral recess was affecting the traversing right L5 and S1 nerve roots. Given the exclusive axial symptoms consistent with lumbar zygapophyseal joint arthropathy, the patient was treated with a repeat L3-4 medial branch and L5 dorsal ramus radiofrequency ablation and experienced subsequent near-complete pain resolution. CONCLUSIONS: Careful consideration must be taken when conducting clinical evaluation, imaging, diagnosis, and treatment of patients with low back pain given the significant frequency of abnormal, often nonconcordant, radiological findings. KEY WORDS: Pneumorrhachis, vacuum disc phenomenon, low back pain, case report