Gas Exploration Research Articles

A novel method to evaluate insulation performance of SF6 alternative gases based on modified GIPF-Local properties model

Abstract The development of structure-activity relationships (SAR) emerges as a crucial strategy to establish the correlations between molecular micro-parameters and the macroscopic dielectric strength, thus markedly improving the gases screening efficiency. However, conventional prediction approaches have failed to characterize the molecule electronegativity accurately, resulting in inadequate prediction precision within extensive gas databases. To address this limitation, we have devised an insulation prediction method that incorporates corrections based on molecular local properties, including local ionization energy and local electron affinity. They enable us to determine both the electron acceptance and donation capacity of the whole molecular orbital electron cloud: a more accuracy assessment of electronegativity. Compared with previous method, our enhanced approach combined local properties with structural and GIPF parameters. It has yielded substantial improvements based on an extensive database comprising 91 gases, as evidenced by an increase in the correlation coefficient from 0.848 to 0.969. Utilizing the modified GIPF-Local properties model, over ten potential gases were found and categorized according to their application. This innovative screening strategy provides crucial insights for exploration and design of new eco-friendly gases as substitute for SF6 used in high-voltage power equipment.

Seismic shear wave noise suppression and application to well tie

Abstract Seismic shear waves have been employed in oil and gas exploration for decades. A 2D seismic shear wave inline was acquired in Sanhu area, located in the Qaidam Basin in western China. Although the acquired shear wave data exhibits high resolution and comparable bandwidth to the compressional wave, it is contaminated by various types of noise, including linear noise, single-frequency noise, and especially internal multiples. Internal multiples seriously compromise the primary reflections at both near-offset and far-offset and are difficult to be suppressed. This paper presents a case study of noise attenuation for the seismic shear wave. Firstly, single-frequency noise and linear noise are attenuated through filtering methods. Then, two methods (the Radon transform and the frequency-wavenumber (F-K) filtering) are evaluated for their effectiveness in multiple suppression and amplitude preservation. The results indicate that both methods successfully reduce long-period multiples at far-offset, enhancing the signal-to-noise ratio. We show that F-K filtering retains the characteristic ‘strong-weak-strong’ amplitude variation in the SV-SV wave data gather, making it preferable for subsequent AVO (amplitude variation with offset) analysis and inversion. Finally, a wave-equation-based MSI (multiple suppression inversion) method is used to suppress near-offset internal multiples. This involves iteratively predicting internal multiples and adaptively subtracting them from the original data. Stacked sections of different offsets are compared to demonstrate de-multiple result, and the result is also validated by the improvement of well calibration with the seismic shear wave data.

Adsorption/desorption characteristics of methane on moist shale under high temperature and pressure: an experimental and molecular simulation study

ABSTRACT The adsorption/desorption characteristics of methane (CH4) on moist shale are of great significance for shale gas exploration and production. However, the influence of moisture on CH4 adsorption/desorption under high temperature and pressure conditions, which is consistent to shale reservoirs (burial depths about 3500−4500 m) in China, remained unclear. In this study, quantitative analysis toward moisture dependence of CH4 adsorption/desorption capability on shales was investigated through experimentation and molecular dynamics simulation under moisture contents of 0%, 0.204%, 0.445%, 0.677%, and 0.965%. Results show that with increasing moisture content, the isothermal adsorption capacity of CH4 decrease, and it reaches 36.80% and 10.00% at moisture content of 0.965% in experimentation and simulation, respectively. Simultaneously, the hysteresis index of CH4 desorption increase by 19.64% and 4.52%. The role of water molecules hindering CH4 desorption under low and high moisture content was clarified. At low moisture content, water molecules are mainly adsorbed on the pore walls, thereby reducing the size of the pore throat and hindering CH4 transport pathways. At high moisture content, many water molecules escape from the original adsorption sites and form clusters in the middle of the pores, blocking the pore throats. Meanwhile, CH4 is re-adsorbed onto the exposed adsorption sites of water, which leads to CH4 desorption hysteresis. The results provide valuable insights for shale gas exploration and production under practical water-bearing shale reservoir conditions.

Numerical optimisation of microbially induced calcite precipitation (MICP) injection strategies for sealing the aquifer's leakage paths for CO2 geosequestration application

Carbon capture and storage (CCS) in deep geological aquifers has shown to be the most viable option for mitigating the greenhouse gas effect of carbon dioxide (CO2) at a large scale. However, the underground formations often possess discontinuities in the caprocks, leaking the stored CO2. Potential leakage paths, such as abandoned wells, have been growing due to excessively unplugged oil and gas exploration wells. The leakage of CO2 from these wells is a major concern, considering their negative impact on the environment and compromising CO2 storage efficiency. Recently, microbially induced calcite precipitation (MICP) technology has proven to be an effective and sustainable method for reducing the permeability of geomaterials. Nevertheless, the MICP process involves intricate interactions among bio-chemo-hydraulics (BCH) domains to comprehend the reactive transport of biochemicals. The complex nature of the MICP process poses difficulties in setting the biochemical injection durations for a particular target distance at the given injection rate. Given this, the present study developed a coupled numerical model and employed it as a workable tool for optimising MICP injections to plug the abandoned well connecting two deep geological aquifers. Following that, the study evaluated the leakage of CO2 using flow migration rates in the untreated and MICP-treated leaky aquifer. The study proposed a novel optimisation strategy for biochemical injections under near and far-field leakage conditions. The sensitivity of biochemical injection durations on the attached bacterial amount and permeability in the leak was also determined. The observations from the present study indicated a complete reduction in the CO2 migration rates from the abandoned well due to a reduced permeability after MICP, thereby indicating the efficacy of the proposed optimisation methodology. Further, a cost analysis of the MICP treatment indicated a rational application cost with the target distance compared to the detrimental effects of CO2 leakage.

Diagenetic evolution and cementation mechanism in deep Carbonate reservoirs: A case study of Dengying Fm. 2 in Penglai, Sichuan Basin, China

The Dengying Formation in the Penglai region of the Sichuan Basin is renowned for hosting high-quality dolomite reservoirs. However, the understanding of their formation mechanisms and spatial distribution patterns remains enigmatic. This study undertakes a comprehensive petrographic analysis of the second member of the Dengying Formation, primarily focusing on its burial history, reservoir characteristics, and an examination of the types, stages, and developmental patterns of cementation within the dolomite reservoir. This is achieved through the application of isotopic geochemistry, inclusion temperature analysis, and laser U-Pb dating. The findings reveal that cements within the second member of the Dengying Formation predominantly occur in pores and fractures, often exhibiting euhedral and subhedral morphologies. These cements also exhibit evidence of replacing original non-skeletal grains and micrites in semi-euhedral and other forms. Broadly, the cements can be classified into four types: calcium cement (the most abundant), dolomite cement, quartz, and pyrite. The formation of calcareous and siliceous cements closely aligns with the sedimentation and burial processes of the Dengying Formation as a whole. The early to late stages of early-middle diagenesis play a crucial role in the formation of dolomite within the second member. Notably, the degree of euhedral dolomite formation directly correlates with the specific diagenetic stage. Our research indicates that the development of high-quality reservoirs in deep-to-ultra-deep microbial dolomites is a result of complex multi-factor interactions and multi-stage discontinuous modifications, leading to strong heterogeneity within the reservoirs. Microbial dolomite carbonates inherently exhibit high initial porosity, with the favorable sedimentary facies serving as the fundamental basis for reservoir development. Dissolution processes during the syngenetic and quasi-syngenetic periods, in conjunction with epigenetic karstification, further augment porosity and expand the reservoir's capacity. During burial and deep burial stages, various acidic fluids play a pivotal role in preserving and modifying the early-formed pores. In the deep environment characterized by high temperature and pressure, microbial dolomite reservoirs undergo intricate diagenetic evolution and possess complex pore preservation mechanisms. Remarkably, even under exceptional ultra-deep conditions, high-quality microbial dolomite carbonate reservoirs can still develop and be preserved, presenting significant potential for oil and gas exploration.

Deformation and fluid flow history of a fractured basement hydrocarbon reservoir below the Sab'atayn Basin, Habban Field, Yemen

Fractured crystalline basement reservoirs are of increasing economic interest for oil and gas exploration and subsurface fluid storage. The successful characterization of these reservoirs is commonly challenged by their structural heterogeneity, complexity in fracture distribution and flow properties at multiple scales, and the difficulty of imaging fractures in exploration seismic. We analyzed the fracture geometry and fracture diagenetic attributes in two oriented cores from the Habban Field in the Late Jurassic Sab'atayn Basin (Yemen) to evaluate the multi-phase deformation history and fracture flow pathway evolution for (hydrothermal) fluids and hydrocarbons. Analyses included petrographic and fluid inclusion analysis of fracture-filling cements, and stable sulfur isotope analyses of fracture-filling pyrite.The Paleoproterozoic basement consists of amphibolite-facies metamorphic ortho- and paragneiss cut by several phases of Neoproterozoic granitoid intrusions. The investigated lithologies in the drill cores comprise (1) epidote quartzite, (2) amphibolite, (3) monzogranite, (4) meta-arkose, and (5) quartz-feldspar porphyry. These lithologies show an inhomogeneous fracture network that is partially cemented. Ediacaran brittle-ductile deformation (D1) recognized only within a Pan-African monzogranite lead to cataclasis and porosity generating alteration. Late Jurassic – Early Cretaceous extension (D2) related to the break-up of Gondwanaland and the formation of the Sab'atayn Basin is found in all lithologies and likely resulted in pervasive quartz cementation. Late Jurassic fractures parallel to the NW-SE trending long axis of the Sab'atayn Basin are best recognized in a strongly foliated amphibolites. Cenozoic extensional fracturing (D3) reactivated older structures, which probably formed during activity of the Neoproterozoic Najd Fault System and caused multi-phased (pyrite-(saddle) dolomite-calcite) fracture cementations. The sulfur isotope compositions of pyrite with δ34S values ranging between −17.4 and + 26.4‰ vs. V-CDT reflects the variability of the fluid source during sulphide mineral formation from hydrocarbon-rich hydrothermal solutions. Fluid inclusions indicate that cementation reactions occurred in a relatively narrow temperature field between 120 °C and 140 °C, ideal for hydrocarbon maturation. Our results demonstrate the potentially complex charge history of basement reservoirs, involving multiple phases of fracture formation and cementation, and fluid charge episodes.

Late Ediacaran to Early Cambrian stratigraphic correlation and its geological implications in the northwestern Sichuan Basin: insights from phosphorus, isotopes, and small shelly fossils

The characteristics of elements, isotopes, and small shelly fossils were investigated for Late Ediacaran to Early Cambrian stratigraphy division and to discuss their geological implications in the northwestern Sichuan Basin. The results reveal that small shelly fossils can be detected in the high-phosphorous section, with the concentration of phosphorus mainly ranging from 2% to 8%, suggesting that this interval belongs to the Early Cambrian, which is also consistent with the carbon isotopic composition results. In addition, the Early Cambrian is denudated in the Sichuan Basin due to tectonic movement, and the characteristics of some isotopes and small shell fossils are different from those in other basins. It can be proposed that P content can support the recognition of lithological boundaries, and the high phosphorus content can be used as a reference to identify the top and bottom boundaries of the Maidiping Formation in the study area. According to the elemental compositions in the Ediacaran Dengying Formation, the variations in Si, Al, Fe, and K contents are similar in the platform area and rift area, suggesting that the third and fourth member of the Dengying Formation are also developed in the Deyang–Anyue Rift. The results suggest that both the Deng-4 member and Maidiping Formation feature contemporaneous deposition of different facies in the northwestern Sichuan Basin. The strata consist of shale intercalated with thin carbonate rock deposits in the Deyang–Anyue Rift, while carbonate rock deposits in the platform. The Deyang–Anyue Rift expanded gradually in the Late Ediacaran and eventually filled in the Early Cambrian. The data in this study illustrate that elemental compositions, isotopes, and small shelly fossils can be combined to correlate the Late Ediacaran to Early Cambrian strata and provide new evidence for Deyang–Anyue Rift evolution. The results offer some new insights for deep oil and gas exploration in the Sichuan Basin and for the tectonic–depositional–environmental–biological synergistic evolution in the Late Ediacaran to Early Cambrian transition.

Source-to-sink processes and genetic mechanism of progradational and lateral accretion submarine fans in the Qiongdongnan Basin, South China Sea

Submarine fan reservoirs are important accumulation zones for oil, gas, and natural gas hydrates, offering significant potential for hydrocarbon exploration. During the deposition period of the Sanya Formation in the southern part of the Changchang Sag of the Qiongdongnan Basin, a large submarine fan developed. However, the internal structure, source-sink system, and formation mechanism of this fan remain poorly understood, posing significant challenges to exploration in this area. This paper examines the source-to-sink sedimentary processes and deposition of submarine fans, using the Changchang Sag, in the Qiongdongnan Basin in the Northern South China Sea, as an example, which will provide valuable general guidance for deep water oil and gas exploration. Based on the theories of seismic stratigraphy and seismic sedimentology, this paper utilizes techniques such as seismic facies analysis, seismic attribute optimization, paleogeomorphology reconstruction, and source-to-sink sedimentary system analysis to analyze the 3D seismic data of the study area. Research indicates that the Sanya Formation in the Changchang Sag of the Qiongdongnan Basin comprises three depositional units: submarine fan, feeder channel, and Semi-deep marine to deep marine mudstone. The submarine fan is a fan formed by the coupling and convergence of submarine fans sourced from the southwest and southeast. Internally, it is divided into three sub-facies: the proximal fan of the sand-rich submarine fan, the main body of the sand-rich submarine fan lobes, and the distal lobes of the sand-rich submarine fan. The submarine fan sourced from the southwest extends nearly north-south and is primarily fed by sediment transported through three large, banded ancient valleys. The sedimentary filling is characterized by three-phase progradation. The submarine fan sourced from the southeast extends nearly east-west and is primarily fed by sediment transported through a single large, banded ancient valley. The sedimentary filling is characterized by two-phase lateral accumulation. During the deposition period of the Sanya Formation, certain areas of the southern uplift belt were exposed for extended periods and subjected to weathering and erosion. Sediments are transported to large ancient valleys through small supply channels. A large number of sediments were transported to the southern slope of the Changchang sag through the provenance channel system such as large ancient valleys and slope belts and deposited in the center of the sag. These make up a complete system of large ancient uplifts and submarine fan source-to-sink sedimentary systems.The sedimentary model is a lobed submarine fan controlled by semi-restricted ancient valleys and expansive basins.

Application of the wavelet transform and Hilbert–Huang transform in stratigraphic sequence division of Jurassic Shaximiao Formation in Southwest Sichuan Basin

Abstract In the southwestern Sichuan Basin, the Jurassic Shaximiao Formation encompasses a multitude of working areas, displaying intricate sedimentary traits. Traditional methods of stratigraphic division based on sequence suffer from inherent subjectivity and limitations. This study employs a combined mathematical approach to use the wavelet transform (WT) and the Hilbert–Huang transform (HHT). It decomposes the natural gamma ray (GR) logging curve into energy spectrum plots and wavelet coefficients at different scales, high and low frequency signals at different frequencies, and a set of intrinsic mode function components and residual functions. The study conducted a detailed stratigraphic division of the Jurassic Shaximiao Formation in the southwestern Sichuan Basin using these methods. The WT offers greater resolution for the periodic changes in the base level, whereas the HHT demonstrates a superior correlation with the positions of stratigraphic interfaces. The combined utilization of the continuous wavelet transform, the discrete wavelet transform, and HHT methods has demonstrated encouraging outcomes in the stratigraphic division of the Jurassic Shaximiao Formation. These methods have been shown to enhance the accuracy of stratigraphic division and to reduce the influence of subjective factors. This study presents new insights and approaches for geological data processing, offering significant theoretical and practical implications and novel technical means for oil and gas exploration and development.

A Comprehensive Review on the Geological Uniqueness and Enrichment Regularity of Shale Gas Reservoirs in China

This paper reviews the geological uniqueness and enrichment regularity of shale gas reservoirs in China, analyzes the patterns of shale gas formation under different geological backgrounds, discusses the main controlling factors affecting the enrichment of shale gas, and proposes potential directions for future exploration and development of shale gas. The study shows that the patterns of shale gas formation in China are diverse and are jointly controlled by multiple factors such as sedimentary environment, diagenesis, and later tectonic movements.

Rhamnolipids Enhance Bioremediation of Petroleum-Contaminated Soil

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215952, “Enhancing Bioremediation of Petroleum-Contaminated Soil Using Rhamnolipids: A Combined Laboratory and Field Study,” by Pan Ni, Lehigh University; Yonglin Ren, SPE, Stepan Oilfield Solutions; and Derick G. Brown, Lehigh University, et al. The paper has not been peer reviewed. _ Hydrocarbon spills can occur at various stages of the oil and gas exploration and production process. Treating these spills onsite to avoid more-expensive excavation and incineration processes would be beneficial. The study outlined in the complete paper aims to optimize the use of rhamnolipid biosurfactants for enhancing the bioremediation of hydrocarbon-contaminated soil. The goal of this work was to explore the effects of rhamnolipid application on hydrocarbon degradation rate under both laboratory and field conditions and to examine the effects of this treatment on the indigenous soil microorganism population. Introduction The authors write that, to the best of their knowledge, previous research studies on rhamnolipid-based soil remediation focused on either laboratory or field tests and that comparison between laboratory-scale and field-scale tests is overlooked but necessary for practical applications. Materials and Methods Materials and Chemicals. The soil used for this work (23 kg for the laboratory test, 10 metric tons for the field test) was obtained from a contaminated site in Longford Mills, Canada. The soil properties are presented in Table 1 of the complete paper. The rhamnolipid stock solution featured 9.8 wt% rhamnolipid blends in deionized water. Another commercial remediation agent (enzyme-based) was used in the field test to compare with the performance of rhamnolipid. Ammonium chloride (NH4Cl) and potassium hydrogen phosphate (K2HPO4) also were used along with sodium hydroxide (NaOH). Experimental Setup. Both laboratory and field tests were ex-situ tests using simulated soil piles. The laboratory test was conducted for 193 days. For the laboratory experiments, an aerobic/anaerobic respirometer system equipped with a low-temperature incubator was used to monitor the in-situ oxygen uptake inside eight reactors (Fig. 1). Each reactor contained 250 g of soil with rhamnolipid doses of 0, 0.1, 0.5, and 1 g/kg. The temperature was set to 25°C. Inside each reactor was placed 10 mL of 4-M NaOH in a 20-mL glass beaker to adsorb the produced CO2. A parallel set of eight reactors was prepared and operated under the same conditions. The nutrients of nitrogen and phosphorous (NH4Cl and K2HPO4) were added at specific times based on the oxygen uptake rate monitored by the respirometer. To avoid the possible inhibition of the microbes in the soil as a result of high ionic strength (greater than 160 mM) in the soil pore water, NH4Cl and K2HPO4 were added so that the molar concentration in the soil pore water did not exceed 100 mM. The field test is being conducted in Longford Mills, Ontario, Canada, and is ongoing at the time of writing. For the field test, 10 metric tons of soil were mixed to achieve homogeneity before the preparation of the soil piles. Five different treatment conditions were examined using duplicate soil piles (10 piles total), with each consisting of 1 metric ton of soil. Nutrient addition was similar to that used in the laboratory tests. Temperature and moisture were monitored every few days at five points in each soil pile, and the pH was monitored once every month at five points.

High‐Resolution Ensemble Modelling of Coral Distributions in the Northern Gulf of Mexico Based on Geomorphometry: Coral Diversity and Benthic Habitat Fragmentation From Oil and Gas Infrastructure to Inform Spatial Planning

ABSTRACTThe northern Gulf of Mexico is home to several species of corals that provide a wide range of ecosystem services to other organisms. Oil and gas infrastructure, such as platforms and pipelines, form an extensive network throughout the northern Gulf of Mexico. Detrimental impacts associated with oil and gas exploration and extraction have been recorded in this area at depths where corals are found. Due to these ecosystems' vulnerability to long‐term impacts, it is necessary to determine areas of interest that would benefit from further exploration and informed spatial planning. This study aimed to identify potential areas of interest for coral studies in the northern Gulf of Mexico. Ensemble species distribution models for 13 species of corals including scleractinians, black corals, and octocorals were produced based on seafloor characteristics and combined to identify areas with relatively higher coral diversity potential than others. The ensemble modelling approach produced robust outputs, as evaluated by the area under the curve, Cohen's kappa coefficient, sensitivity, specificity and the proportion of correct predictions. The proximity of suitable habitat to active and proposed oil and gas infrastructure was evaluated; this spatial analysis showed that oil and gas infrastructures potentially impact 23.5% of all predicted suitable coral habitat in the study area and contribute to benthic habitat fragmentation. Twelve areas of interest greater than 100 km2 and located outside a 4‐km zone of potential influence from oil and gas infrastructure were delineated and deemed of interest for further exploration and spatial planning, and hypothetical prioritization scenarios for spatial planning are presented. The maps produced can inform discussions among stakeholders to reach the best spatial planning outcomes while considering other ecological, social, economic and governance factors.

Application of distributed acoustic sensing technology in deep shale gas exploration

Abstract In the past decade, the exploration and development of deep shale gas usually adopted geophone acquisition for vertical seismic profile (VSP) to improve the accuracy and resolution of seismic data. However, it’s very hard to use the 10-20m level spacing geophones to meet the resolution of 2-5m thin reservoir. Distributed acoustic sensing (DAS) technology has been widely used in the oil and gas field due to its advantages of high density and high efficiency acquisition, especially in vertical seismic profile and dynamic monitoring. We have acquired zero offset VSP by DAS and geophone for the first time in deep shale gas wells at home, and successfully overcome the coupling problem in open-hole sections. Vibrators are used as sources for multiple stacking to improve the signal-to-noise ratio (SNR) of DAS VSP. The records show DAS has significant advantages in frequency, SNR and wavelet consistency. After data processing, the layer velocity characteristics of DAS VSP are more obvious. DAS VSP corridor stack has a high degree of consistency with the synthetic record and seismic profile, and the resolution of the reservoir was higher than geophone.

Natural gas accumulation conditions and exploration directions of Carboniferous clastic rocks in the northeastern margin of Junggar Basin, China

The Carboniferous strata in the northeastern Junggar Basin are an important exploration field for natural gas in the basin. However, volcanic rocks have long been the primary exploration target. In contrast, the exploration and research of clastic rocks associated with source formations have been largely overlooked, resulting in an insufficient understanding of the reservoir forming conditions and exploration potential of Carboniferous clastic rocks. Through the evaluation of Carboniferous source rocks, effective source stove characterization, clastic reservoir evaluation, oil and gas source correlation, and reservoir formation model construction in this region, three key findings have been made. First, the Carboniferous in the northeastern Junggar Basin has developed three sets of high-quality gas source rocks: the Dishuiquan Formation, the Songkalsu B Member, and the Shiqiantan Formation. These formations correspond to three hydrocarbon source centers: the Sannan–Dishuiquan Sag, the Wucaiwan Sag–Dajing area, and the Dongdao Haizi Sag–Baijiahai High. Second, the Carboniferous system in the northeast has developed multiple types of large-scale reservoirs, including sand conglomerates, sandstones, turbidites, dolomitic rocks, and shale. These reservoirs are generally characterized by low porosity to ultra-low porosity and low permeability to ultra-low permeability reservoirs. There is a dissolution pore development zone at depths of 2900–4500 m. Third, a comparison of oil and gas sources reveals that all three sets of gas source rocks contribute to the natural gas found in the northeast, with obvious characteristics of near-source reservoir formation. The Carboniferous clastic rocks host two types of natural gas reservoirs: unconventional and conventional near-source reservoirs. It is predicted that there is an orderly accumulation pattern of shale gas, tight sandstone gas, and conventional natural gas reservoirs. This study reveals that the Carboniferous clastic rock source and reservoir configuration in the northeastern Junggar Basin is highly favorable, and the natural gas reservoirs in source and near-source clastic rocks represent important exploration directions.

Introduction to this special section: The Eastern Mediterranean

With the current focus on clean energy and the role of Eastern Mediterranean gas, and after the organization of the successful SEG Mediterranean Gas Exploration (MEGA) Symposium in Egypt in 2023, it became clear that a TLE special section on the Eastern Mediterranean was needed to present more discussions, more ideas, and more data to a larger audience for the benefit of unlocking the basin's material yet-to-find potential.

Sedimentary dynamics and depositional model for mud accumulation in deep lake basins: A case study in the Upper Triassic Chang-7 Member, Ordos Basin, northern China

Shales in deep lake basins have become the main focus of continental shale oil and gas exploration. In order to highlight the sedimentary dynamics of mud deposition in deep lake basins, a combination of core observation, thin section examination, X-ray diffraction, and QEMSCAN (quantitative evaluation of minerals by scanning electron microscopy) was used to analyze the depositional characteristics of mudrocks in the Chang-7 Member from the Yanchang Formation (Upper Triassic) in Ordos Basin, and to establish a depositional model for mud accumulation in deep lake basins. This study recognizes four mudrock lithofacies in the Chang-7 Member: (1) the laminated silt-bearing mudstone, which generally develops a binary composition of “silt–clay” or a ternary composition of “silt–clay–organic matter”; (2) the graded mudstone, mainly composed of dark gray and gray-black mudstone sandwiched by silt-bearing mudstone; (3) the massive mudstone, internally showing a uniform distribution of quartz, clay, and carbonate minerals, with also a small amount of organic detritus; and (4) the laminated shale, which is generally composed of clay laminae, and organic laminae of the former two. Sediment supply, topographic slope, and flood intensity combine to control the evolution of gravity flows and the transport and deposition of the mudrock in the Chang-7 Member. The influence of orogeny provides terrain gradient, water depth, abundant sediments at source areas, and triggering mechanism for the formation of gravity flows. Floods triggered by wetting events provide the impetus for sediment transport. Mud deposition in the Chang-7 Member was mainly related to the transport and sedimentation of mud by hyperpycnal flows and rapid sedimentation by buoyant plume flocculation. A comprehensive evolutionary model for shale accumulation in the deep lake basin is established by integrating various triggering mechanisms and mud transport sedimentary processes.

An eco-friendly approach to separate emulsified oil from water using all natural materials of chitosan and beach sand

Oil-contaminated water from oil and gas exploration remains the industry’s primary waste stream. The common method of using chemical coagulation/flocculation followed by air flotation has drawbacks such as generating non-biodegradable and toxic sludge and high operational costs. This study presents an eco-friendly alternative utilizing chitosan and beach sand to remove emulsified oil from water. Chitosan acts as a biodegradable flocculant, while beach sand aids in high-density floc formation and accelerates settling velocity. This approach achieved up to 94 % oil removal efficiency and reduced settling time from 90 to 15 min by using 100 mg/L chitosan and 500 mg/L beach sand with a particle size distribution of 50–100 μm. Shorter settling time reduces capital expenditure compared to conventional methods. Additionally, using natural materials like chitosan and beach sand minimizes toxic sludge generation. This eco-friendly approach offers a promising alternative to conventional methods for treating oily wastewater.

A Critical Review on the Advancements in Exploration and Production of Shale Gas

The exploration and production of shale gas have seen significant advancements in recent years, driven by the increasing global demand for clean energy sources. These advancements encompass the understanding of a wide range of areas, including the formation theory of shale gas reservoirs, evaluation methods, well drilling, completion, and simulation techniques. Innovative design, modelling, and field practices have been developed for shale gas well drilling and completion, as well as its production techniques. Furthermore, new simulation techniques, software, algorithms, and other tools have been introduced to improve the modelling and simulation of shale gas production. Experimental and simulation research in shale gas exploration, development, and production using hydraulic fracturing has also seen considerable progress. These advancements are contributing significantly to the global demand for clean energy sources with a promise to achieve sustainable development goals. This review work explores the exploration and exploitation of shale gas with a detailed description of multidisciplinary research efforts, providing valuable insights into shale reservoir/rock characterization and geo-mechanics, fluid-surface interactions, gas adsorption behaviours and single- and multi-phase flow mechanics. These advancements are not only increasing the efficiency and productivity of shale gas extraction but also paving the way to meet the future global energy demand while also contributing to the goal of achieving net-zero carbon emissions. The novelty of the review work is that it exhibits a combined qualitative and quantitative study of recent advancements in the sphere of exploration and production of shale gas reserves and its discoveries around the globe.

Maritime law enforcement concerning offshore energy platforms: Navigating international law constraints and challenges

Offshore energy platforms (OEPs) serve as a crucial frontier in utilizing renewable energy sources to meet energy demands, powering essential maritime operations such as remote island power supply, offshore oil and gas exploration, seawater desalination, and marine renewable energy harvesting. However, the development of OEPs raises significant legal concerns for maritime law enforcement. Employing a policy analysis approach, this research delves into the multifaceted challenges faced by the current international legal framework in regulating enforcement activities pertaining to OEPs. These challenges encompass ambiguity in OEP legal status, difficulties in balancing safety measures with diverse maritime interests, obstacles in environmental assessment and enforcement, and heightened enforcement challenges in areas beyond national jurisdiction. The study explores potential strategies for resolution and collaboration on an international scale. Through this investigation, the study aims to provide valuable insights to promote greater clarity and coherence in maritime law enforcement practices concerning OEPs, thereby enhancing safety, security, and environmental sustainability for OEP operations in maritime environments globally.

Study on the relationship between shale organic matter development and paleowater depth—A new understanding of the condensed section

Recent studies dispute the long-standing belief that highly organic-rich shales are predominantly linked to condensed section (CS) at the maximum flooding surface (MFS), proposing instead that they more commonly develop in shallow waters along basin margins. This hypothesis, however, has not been thoroughly investigated. Our study, focusing on the pivotal regions of the Longmaxi Formation and the Chang 7 Member for marine and continental shale exploration in China, integrates sequence stratigraphy with analyses of total organic carbon (TOC) and elemental geochemistry to pinpoint the environments conducive to the formation of organic-rich shales. The most organic-rich intervals, specifically the bottom of the Longmaxi Formation and the mid-to-lower Chang 73 sub-member, are located within the transgressive systems tract (TST), showing higher TOC levels in the middle to lower TST, compared to the CS of the MFS. The formation of high organic matter shale is related to warm, humid, and dysoxic shallow waters with minimal terrigenous influx and high primary productivity. We found a pronounced inverse relationship between organic matter concentration and water depth, with deeper waters promoting the decomposition and recycling of organic matter during sedimentation, thereby diminishing the TOC content. Moreover, volcanic activity also affected the organic enrichment in the Chang 7 Member. With high primary productivity, organic matter tends to accumulate in dysoxic slope zones. Consequently, high-organic content shale intervals are generally situated in shallow, dysoxic water environments, suggesting that the CS of the MFS may actually represent organic-poor intervals with limited source rock potential. The results of this study are of great significance for shale oil and gas exploration in China, and provide a new direction for the discovery of shale oil and gas sweet spots.