Sandstone Formation Research Articles

Formation damage challenges and solutions in cased hole gravel pack completions in deep offshore unconsolidated laminated sandstone formations in the Sakarya Field

A comprehensive experimental formation damage study for the Sakarya Field was conducted to identify production impairment mechanisms induced by operational fluids. The study reveals that the retention of operational fluids leads to irreversible reductions in gas permeability to a certain degree. This fluid retention is associated with the amount of loss and retention time of operational fluids into the reservoir, as well as the types of clays present in the gas bearing zone. Fluid retention damage is more severe for samples with lower permeability and higher silt content. While sandy plugs typically experience a reduction in permeability of less than 10%, low-permeability silty samples can exhibit reductions as high as 35%. The most effective approach to minimize this damage includes maintaining the lowest possible overbalance pressure, applying completion methodologies with minimal fluid invasion, and ensuring timely and effective cleanup. Another source of damage appears to result from acidic dissolution of native carbonate minerals and destabilization of delicate clays (e.g., chlorite). This leads to slight compaction and associated immediate reduction in permeability, reaching as high as 50% when combined with other operational fluid damage in some cases. In such environments, it is recommended to use a milder alternative acid solution that specifically targets the filter cake and debris around perforations, minimizing the dissolution of native carbonate minerals and interaction with clays. Due to the low uniaxial compressive strength (UCS) of the formation, evidence of sanding and proppant embedment was observed. To mitigate this issue, an optimum gravel pack design and execution during well completion is vital. Additionally, avoiding abrupt bean-up and bean-down during well tests and production will help limit sanding and proppant embedment. The novel experimental methodology and field implications derived from this study may serve as a guideline to solve formation damage challenges in similar fields facing similar issues. Initiating such detailed studies in the early stages of field development is critical to ensure maximum recovery from the least damaged and disturbed reservoirs.

The effect of methylene blue and organic acids on the wettability of sandstone formation: Implications for enhanced oil recovery

The effect of methylene blue and organic acids on the wettability of sandstone formation: Implications for enhanced oil recovery

Impact of Methylene Blue on Enhancing the Hydrocarbon Potential of Early Cambrian Khewra Sandstone Formation from the Potwar Basin, Pakistan.

Significant amounts of hydrocarbon resources are left behind after primary and secondary recovery processes, necessitating the application of enhanced oil recovery (EOR) techniques for improving the recovery of trapped oil from subsurface formations. In this respect, the wettability of the rock is crucial in assessing the recovery and sweep efficiency of trapped oil. The subsurface reservoirs are inherently contaminated with organic acids, which renders them hydrophobic. Recent research has revealed the significant impacts of nanofluids, surfactants, and methyl orange on altering the wettability of organic-acid-contaminated subsurface formations into the water-wet state. This suggests that the toxic dye methylene blue (MB), which is presently disposed of in huge quantities and contaminates subsurface waters, could be used in EOR. However, the mechanisms behind hydrocarbon recovery using MB solution for attaining hydrophilic conditions are not fully understood. Therefore, the present work examines the impacts of MB on the wettability reversal of organic-acid-contaminated Khewra sandstone samples (obtained from the outcrop in the Potwar Basin, Pakistan) under the downhole temperature and pressure conditions. The sandstone samples are prepared by aging with 10-2 mol/L stearic acid and subsequently treated with various amounts of aqueous MB (10-100 mg/L) for 1 week. Contact angle measurements are then conducted under various physio-thermal conditions (0.1-20 MPa, 25-50 °C, and salinities of 0.1-0.3 M). The results indicate that the Khewra sandstone samples become hydrophobic in the presence of organic acid and under increased pressure, temperature, and salinity. However, the wettability changes from oil-wet to preferentially water-wet in the presence of various MB solutions, thus highlighting the favorable effects of MB on EOR from the Khewra sandstone formation. Moreover, the most significant change in wettability is observed for the Khewra sandstone sample that was aged using 100 mg/L MB. These results suggest that injecting MB into deep underground Khewra sandstone reservoirs may produce more residual hydrocarbons.

Aeolian–lacustrine margins: implications for carbon capture and storage within the Rotliegend Group, Southern North Sea

The Southern North Sea Basins of the United Kingdom were renowned for their hydrocarbon resources and exploited extensively from the 1960s to the 1990s. The Permian Leman Sandstone in particular formed an excellent reservoir due to its extensive clean aeolian sediments and was subsequently explored for decades, resulting in a wealth of subsurface data that are now widely accessible. The strata of the Leman Sandstone comprises mixed continental deposits from aeolian, fluvial and lacustrine environments which interfinger with the saline lake deposits of the Silverpit Formation. With the potential reassessment of depleted gas reservoirs in the North Sea for use as sequestration targets for captured carbon dioxide, there is significant renewed interest in the reservoir geology of the Leman Sandstone. A regional study of the sedimentology and petrophysical properties of the Leman Sandstone and Silverpit formations within quadrants 43, 44, 48 and 49 of the Southern North Sea has been conducted. Multiple interactions between the depositional environments are observed, resulting in a complex interplay between aeolian and lacustrine transgressive/regressive events, and migration and expansion/contraction of the fluvial system. In wireline petrophysical data, each depositional environment, along with their transitional environments, form relatively distinct clusters that can be used as a predictive tool for reservoir interpretation in the absence of core, despite extensive sediment recycling between environments.

The Mangking Sandstone Formation of Kuala Tahan to Kampung Bantal: Sedimentology and Depositional Environment

The Mangking Sandstone of Tembeling Group in the Kuala Tahan region records part of the infill of the continental extensional basin formed at the end of the Triassic. Described facies of this formation include sandy matrix conglomerate (that shows evidence of pseudoplastic debris flow and traction-dominated deposition), sandstones with trough, tabular and horizontal stratification, laminated and massive mudstone. Groups of associated facies are arranged into six distinct architectural elements (channel, sandy bedform, crevasse splay, laminated sand sheet, downstream and lateral accretion and floodplain fines), which are constant with a fluvial origin for the succession. The types of architectural elements present and their relationship to each other demonstrate that the Mangking Sandstone preserves a record of a meandering river system.

Facies analysis and sequence stratigraphy of shallow marine, coarse‐grained siliciclastic deposits in the southern Utsira High: The Late Jurassic intra‐Draupne Formation sandstones in the Johan Sverdrup Field (Norwegian North Sea)

AbstractThin, condensed coarse‐grained shallow marine successions can be difficult to describe and interpret, especially in the subsurface since the recognition of finer‐grained intervals, typically associated with sequence stratigraphic surfaces, is challenging. This lack of mudstones and siltstones means that they also typically make excellent reservoir intervals. The Oxfordian to Volgian intra‐Draupne Formation sandstones in the Johan Sverdrup Field, southern Utsira High, represent such a system. This study presents a new sequence stratigraphic model for the Johan Sverdrup Field that unravels the detailed depositional history of the succession and places its formation within a regional Late Jurassic tectonostratigraphic framework. The intra‐Draupne Formation sandstones comprise four parasequences deposited following a regional Kimmeridgian marine flooding event. Sediments were mainly supplied through West‐derived fan deltas from the Haugaland High and NW‐SE‐directed tidal currents reworking the Augvald Graben and the Avaldsnes High at the East. The oldest parasequence shows a distinctive suite of facies consisting of fine‐grained and mud‐rich bioturbated sandstones deposited in a semi‐restricted lagoon. Subsequent parasequences lack fine‐grained sediments and are dominated by bidirectional cross‐stratified, very coarse‐to coarse‐grained sandstones and gravels deposited in a tidal strait. A progressive reduction of fault‐related subsidence in the Middle Volgian along with Late Volgian‐Ryazanian sea‐level rise and inversion of pre‐existing structures promoted backstepping of the feeder systems, sediment starvation and the progressive deposition of the black and green‐red shales of the Draupne and Asgard formations. The results of this study account for features previously unidentified in the Johan Sverdrup Field and which have implications for understanding the deposition of coarse‐grained shallow marine successions around the Utsira High and other transgressed basement highs.

Characteristics and control factors of tectonic fractures of ultra-deep tight sandstone: Case study of the Lower Cretaceous reservoir in Bozi-Dabei area, Kuqa Depression, Tarim Basin, China

The Bozi-Dabei area in the Kuqa Depression host high-quality reservoirs in the Bashijiqike Formation and Baxigai Formation sandstones of the Lower Cretaceous, in which reservoirs yield significant industrial gas flow despite being situated at a considerable burial depth of 8200 m. The geological history of the target formation involves multiple phases of tectonic movements, resulting in the development of multi-genetic fractures that enhance the reservoir's storage and seepage capacity. Based on the results of the drilling core, field profile survey, imaging logging, and experimental analysis, this study presents an analysis of fractures in the Lower Cretaceous dense sandstone reservoir of the Bozi-Dabei area, andclarifies the characteristics and controlling factors of the multi-genesis and multi-period fractures. Additionally, it proposes an effective fracture development model that accounts for geo-stress control. In the Bozi-Dabei area, the prevailing high extrusion stress environment has led to the development of predominantly regional tectonic fractures and fault-related fractures, with relatively gentle deformation-related fractures. The results of a combination of multi-attribute data determination techniques, including fracture filling, inter-cutting relationship, fracture filling isotope, inclusions, and cathode luminescence tests, this study reveals that the reservoir fractures have experienced three major periods of tectonic movement. The regional tectonic fracture development is mainly controlled by stratigraphic lithology and thickness, while the proximity influences fault co-derived fractures to the fault and the relative positions of the upper and lower plates of the fault. The shift in the direction of the late horizontal maximum principal stress leads to the opening or closing of early fractures under different conditions in the Bozi-Dabei area, consequently affecting the degree of fracture opening and effectiveness. Notably, when the horizontal maximum principal stress is deflected to intersect with early fractures at a smaller angle or even superimpose, the fracture effectiveness of the related group system in the deflection direction improves, resulting in an overall coordination. The distribution characteristics of the fracture system in this highly productive reservoir are the result of dominant configurations from multi-phases of geological activities.

Assessment of Potential Potable Water Reserves in Islamabad, Pakistan Using Vertical Electrical Sounding Technique

This study aimed to investigate the potential reserves of potable water in Islamabad, Pakistan, considering the alarming depletion of water resources. A detailed vertical electrical sounding (VES) survey was conducted in two main localities: Bara Kahu (Area 1) and Aabpara to G-13 (Area 2), based on accessibility, time, and budget constraints. A total of 23 VES measurements were performed, with 13 in Area 1 and 10 in Area 2, reaching a maximum depth of 500 m. Geologs and pseudosections were generated to assess lithological variations, aquifer conditions, and resistivity trends with depth. Statistical distribution of resistivity (SDR), hydraulic parameters, true resistivity, macroanisotropy, aquifer depth and thickness, and linear regression (R2) curves were calculated for both areas, providing insights into the aquifer conditions. The results revealed that the study areas predominantly consisted of sandy lithology as the aquifer horizon, encompassing sandstone, sandy clay, and clayey sand formations. Area 2 exhibited a higher presence of clayey horizons, and aquifers were generally deeper compared to Area 1. The aquifer thickness ranged from 10 m to 200 m, with shallow depths ranging from 10 m to 60 m and deeper aquifers exceeding 200 m. Aquifers in Area 1 were mostly semi-confined, while those in Area 2 were predominantly unconfined and susceptible to recharge and potential contamination. The northwest–southeast side of Area 1 exhibited the highest probability for ground resource estimation, while in Area 2, the northeast–southwest side displayed a dominant probability. The study identified a probable shear zone in Area 2, indicating lithological differences between the northeast and southwest sides with a reverse sequence. Based on the findings, it is recommended that the shallow aquifers in Area 1 be considered the best potential reservoir for water supply. In contrast, deeper drilling is advised in Area 2 to ensure a long-lasting, high-quality water supply. These results provide valuable information for water resource management and facilitate sustainable water supply planning and decision making in Islamabad, Pakistan.

Formation damage induced by working fluids sequentially interacting with tight sandstone oil reservoirs

Drilling fluid loss is a frequent downhole incident in the process of deep well drilling and completion. Drilling fluid will damage the formation permeability and affect well production, but some wells with high volume drilling fluids loss can have high production. To investigate the mechanism of drilling fluid loss damage in tight sandstone oil reservoirs, this study selects some core plugs and the working fluids from X field in Ordos Basin, China, conducts the evaluation experiments of drilling fluid damage and working fluid sequential contact damage, and analyzes the well history and well production performance data. Results show that the permeability recovery rate decreases continuously, after different fluid displacement. The permeability recovery rate of rock sample after drilling fluid displacement is 46.21–67.14%, and the permeability recovery rate after different working fluid displacement is 22.92–61.45%. Then well history and production fluctuations are analyzed. It shows the incompatibility of working fluid will cause superimposed damage to hydraulic fractures. The main damage mechanism caused by drilling fluid loss is incompatibility damage and particle invasion. Loss of drilling fluid will improve damage risk of the subsequent stimulation operations, though it doesn't show damage features in initial stage. Formation damage degree is related to the storage space type of reservoir. The results serve as a guide for the drilling fluid design of oil in tight sandstone formation.

Application of ABAQUS Flow-Solid coupling model to evaluate sealing capability of sandstone formation interface based on the cracking behavior of cohesive force units

Estimating the sealing property of the cementing interface is vital for judging the quality of well cementing construction. The main methods currently used to evaluate the sealing property of the cementing interface (hydraulic cementing strength method and shear cementing strength method) are susceptible to the effects of specimen geometric regularity, interfacial cementing condition, and shear damage pressure source, and the measurement results are not stable, making it difficult to use them as effective methods to evaluate the real cementing interface sealing performance. In this paper, based on the cracking behavior of cohesive units, a method to evaluate the sealing performance of the cementing interface by simulating the cracking process of fluid breaking through the cementing interface in ABAQUSTM FEA software was investigated. The research process includes two parts: first, using a self-designed holding stretching device after eliminating the errors caused by non-interface displacement in the conventional stretching method by repeated stretching and subtraction. The real interfacial traction-separation curve and formation cohesion unit parameters were obtained. Secondly, the cohesive unit parameters obtained in the first step were input into ABAQUSTM FEA software to build a fluid–solid coupling model to simulate the cracking process in the interface region when the fluid breaks through the cementing interface, in which obtaining the solid interface cracking sealing pressure and evaluating its sealing performance are finished. And the accuracy and feasibility of this method were verified by a homemade physical sealing model of the cementing interface. In addition, the factors affecting the fluid pressure at the breakthrough of the cemented interface were investigated in this paper, and it was concluded that changing the elastic modulus of sandstone and cement sheath had a more significant effect on the fluid pressure at the breakthrough of the cemented interface than their Poisson's ratios. Furthermore, the results of this paper also indicate that when the permeability of cement sheath and sandstone is in the range of 0.001 mD–10 mD, the fluid pressure at the time of breaking the cemented interface decreases as the permeability of cement sheath and sandstone increases, and beyond this interval, the effect of the sudden change in permeability of cement sheath and sandstone on the fluid pressure at the time of breaking the cemented interface is no longer obvious.

Effect of Methyl Orange on the Wettability of Organic-Acid-Aged Sandstone Formations: Implications for CO2 Geo-storage

Effect of Methyl Orange on the Wettability of Organic-Acid-Aged Sandstone Formations: Implications for CO₂ Geo-storage

Late Silurian event stratigraphy and facies of South Wales and the Welsh Borderland, United Kingdom

AbstractLithofacies and biostratigraphical analysis has enabled the establishment of a stratigraphic event framework for Ludfordian and Pridoli strata in south Wales and the Welsh Borderland. In SW Wales, the Golden Grove Axis acted as a structural hinge separating the shallow marine storm-influenced Cae’r mynach Seaway from a pediment surface above which Ludfordian colluvium (Abercyfor Formation) was deposited. The Axis seeded four NW-derived river-influenced delta progrades of Leintwardinian to early Pridoli age (Tilestones Formation). A NE-sourced early Pridoli wave-influenced delta deposited the Downton Castle Sandstone Formation (DCSF), coeval to the youngest Tilestones prograde, with a lateral interface existing between Mynydd Epynt and the Clun Forest area. Except for the Malverns area, the DCSF is no longer recognized south of the Neath Disturbance. Early Pridoli forced regression promoted widespread subaerial exposure north of the Neath Disturbance, with incision into tracts close to the Welsh Borderland Fault System. The basinward-shift in facies belts resulted in marine erosion and deposition of a phosphatic ravinement pebble lag. The wave-influenced Clifford’s Mesne Sandstone Formation delta subsequently seeded on the Gorsley Axis with tidally influenced Rushall Formation accumulating in a back-barrier setting. The Pwll-Mawr Formation records the easterly advance of coeval coastal deposits on the western side of the remnant Cae’r mynach Seaway. Behind migrating delta coastlines, green muds accumulated on coastal plains (Temeside Mudstone Formation) with better drained red dryland alluvium (Moor Cliffs Formation) charting expansion of Old Red Sandstone lithofacies. Mid-Pridoli incision preserves the Pont ar Llechau Formation estuarine valley fill.

Study Evaluates CO2 Storage Potential During CO2 Mobility-Control Optimization

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 212969, “Evaluation of CO2 Storage Potential During CO2 Mobility-Control Optimization for Enhanced Oil Recovery,” by Alvinda Sri Hanamertani, SPE, Ying Yu, SPE, and Omar El-Khatib, SPE, University of Wyoming, et al. The paper has not been peer reviewed. _ CO2 mobility control through foam technology has enabled better sweep efficiency and, consequently, better oil productivity during enhanced oil recovery (EOR) processes. Along with enhancing oil production, a sound potential exists for in-situ generated foam to enhance CO2 storage. However, the effect of the different in-situ foam generation strategies on the combined goal of maximum oil production and carbon storage is not well elucidated in the literature. In the complete paper, the authors methodically evaluate the simultaneous optimization of CO2 storage and oil recovery using multiple injection strategies. Introduction The current investigation is a continuation of two previous studies that provided a methodology for screening and using foaming agents for optimized CO2 storage in sandstone and carbonate formations. A base case of tertiary CO2 flooding was established for comparison with in-situ foam generation by two approaches: single-cycle surfactant-alternating-gas (SAG) flooding and coinjection of CO2 and surfactant. Additionally, the effect of surfactant concentration on foam efficiency, CO2 storage capacity, and oil recovery were evaluated in both approaches at reservoir conditions. Materials and Methods Fluids and Porous Medium. In this study, a synthetic brine with total dissolved solids of 20 wt% was used as blank brine and laden with a commercial zwitterionic surfactant that was used to prepare surfactant solutions with concentrations of 0.5 and 1 wt% active matter in the synthetic brine. Three core plugs were drilled from an Indiana limestone outcrop block. The cores were then cleaned and oven-dried at 95°C. Experimental Procedure. Vacuum saturation with brine was commenced for the three cores. The porosity of the cores was calculated using their dry and brine-saturated weights. Then, the 100% brine-saturated core was placed in a core holder and loaded into an oven set to 90°C. The pore pressure was fixed at 2,000 psi, and the confining pressure was controlled at 3,000 psi throughout the flooding experiment. The brine permeability of the core samples was evaluated by measuring the pressure drop across the core at different brine-injection flow rates. In the first experiment (IL1), oil drainage with a flow rate of 0.2 cm3/min was performed to establish irreducible water saturation of 46.9%. This total flow rate was kept the same throughout the three experiments. Then, a waterflooding stage was begun and the oil recovery was recorded. After reaching a plateau in oil recovery, supercritical CO2 (scCO2) was injected during the EOR process until the oil production plateaued.

Impact of H2-CH4 mixture on pore structure of sandstone and limestone formations relevant to subsurface hydrogen storage

Subsurface Hydrogen (H2) storage is a promising technology to achieve net-zero carbon emissions. Depleted gas reservoirs can provide safe storage of hydrogen in the long term, and effective recovery during the cycling process. The pre-existing Methane gas (CH4) or its traces in these formations can mix with the injected hydrogen and might cause in-situ geochemical reactions with the storage rock. Despite the recent interest in evaluating H2-rock interactions, the available knowledge on the impact of H2–CH4 mixture on the petrophysical properties of storage rocks is scarce. Motivated by the lack of experimental work that exists on this topic, we provide an experimental investigation on the reactivity of sandstone and limestone formations to H2–CH4 mixture. Samples from Bandera Gray Sandstone and Indiana Limestone samples were aged in H2–CH4 mixture at 75 °C and 1400 psi for 90 days, and Nuclear Magnetic Resonance (NMR) and gas porosity analysis were performed. The results showed limited reactivity of the samples to H2–CH4 mixture, and subsequently, insignificant changes occurred in the petrophysical properties. The average porosity of BG and IL samples decreased by 3.32 % and 1.00 % respectively. NMR analysis indicates no significant changes in T2 distribution times curves, indicating no major alterations occurred in the pore structure or rock geometry. Moreover, the average NMR porosity of BG was reduced by 3 %, while the reduction of IL porosity did not exceed 6 %. We conclude that the potential geochemical reactions (dissolution/precipitation) between the H2–CH4 mixture and rock minerals are very weak within 90 days of H2–CH4 mixture treatment, thus the suitability of sandstone and limestone rocks for hydrogen storage is promising.

Support Optimization of Open TBM Tunneling in Luohe Formation Sandstone by CT Test and Numerical Simulation

As underground engineering extends into the western and deeper regions of China, more and more Luohe Formation sandstone layers will be encountered, which have weak cementation and high water content. It is a significant challenge to apply the open TBM, and the support system is crucial in determining whether TBM can excavate quickly and safely. Therefore, in order to optimize the support scheme, this paper analyzes the pore structure and porosity through CT scanning, the results indicate that the volume percentage of pores ≥34 μm is 2.3% and 1.5%, respectively, the large pore apertures are predominant, the surrounding rock has strong permeability, and there is a high risk of rock burst and roof collapse accidents, hence requiring reinforced support measures. On this basis, numerical simulations were conducted to evaluate the support effectiveness. The results show that replacing the “bolt + mesh” with a “bolt + cable + mesh + steel belt”, and replacing the top three bolts with 7.3 m anchor cables, can better control the deformation and provide sufficient thrust force for the TBM, ensuring excavation speed. After the implementation of this scheme at the Kekegai coal mine in Shaanxi, China, the TBM excavation speed increased by 70%, from the previous 10 m/day to 17 m/d, significantly reducing the project duration and construction costs.

Provenance, diagenesis and reservoir quality of sandstone facies of the Maracangalha Formation, Recôncavo Basin – Northeastern Brazil

Sedimentary composition studies on siliciclastic reservoirs and their relationship with sedimentary provenance have proved to be useful in hydrocarbon exploration, enabling the prognosis of reservoir quality and diagenetic models. However, unconventional terrigenous reservoirs in the Maracangalha Formation, Upper Cretaceous from Recôncavo Basin, have not yet been evaluated regarding sedimentary provenance and its control over reservoir quality. This study aims to define the provenance of the Maracangalha Formation sandstones and its control on the diagenetic processes affecting the reservoir quality. Based on petrography analysis and X-Ray Fluorescence data, it was possible to identify a granite-gneissic terrain under wet climate as the primary source area for quartz-feldspathic sandstones. The granite-gneissic terrains with predominantly felsic minerals, within in the surrounding Precambrian Terrains, represent a major source area for the quartz-feldspathic sandstones found in the Maracangalha Formation. These sources are characterized by significant contributions from recycled sedimentary and metasedimentary rocks, leading to the occurrence of litho and quartzose petrofacies. The high chemical-textural sediment maturity and paleoweathering dispersion, under semi-umid to semi-arid climates, may be a result of paleoclimatic changes and the variable residence times of the sediments in the dispersion routes or temporary storage. The mineral composition and primary texture of sandstones show a clear influence on diagenetic evolution, particularly in terms of mechanical compaction inhibition, by early cementation, and the generation of secondary porosity due to the dissolution of framework grains and early cements. Therefore, understanding the sedimentary provenance, composition, and diagenesis is crucial for predicting the quality of the reservoir and the compartmentalization of the Maracangalha Formation and its analogues.

Revised models for evaluating hydrocarbon saturation of tight sandstone formations based on dielectric dispersion logs

AbstractAccurate estimation of hydrocarbon saturation is significant for log interpreters to evaluate tight sandstone formations. It is difficult to use conventional wireline logs to calculate hydrocarbon saturation in complex reservoirs. Dielectric dispersion logs are processed using dielectric models to obtain accurate saturation assessment, especially in high salinity shaly sand formations. However, the dielectric models consist of complex refractive index method model and shaly sand model ignore the impact of clay effects on complex refractive index method model, and the dielectric dispersion logs generated by them appear several unphysical phenomena in the clay‐bearing formations, such as the permittivity data at the highest frequency are greater than those at the second highest frequency and the conductivity data at the highest frequency are lower than those at the second highest frequency. This paper modifies the dielectric models by introducing a combined conductive phase in complex refractive index method model to correct the unphysical behaviours. Revised models are combined with four permittivity and four conductivity logs acquired by dielectric scanner at 24, 102, 360 and 960 MHz to inverse the water saturation, water salinity, textural index for water‐bearing pore and fraction of clay‐related phase. The complex refractive index method model interprets the logs measured at 960 MHz and shaly‐sand model interprets other dielectric dispersion logs. The particle swarm optimization algorithm is used to search inversion parameters. The results of forward simulation show that the revised models can correct unphysical behaviours of dielectric dispersion logs generated by the original models. Moreover, we apply original models and revised models to laboratory core data. The results of experiments show that the mean relative error values of the original models are 19.38% and 23.60% and of the revised models are 5.54% and 6.28% in two cases. It shows that the revised models are more accurate than the original models to interpret dielectric dispersion logs of tight sandstone reservoirs.

The osteology of the Late Triassic reptile Scleromochlus taylori from μCT data.

Scleromochlus taylori is one of the most enigmatic members of the herpetofauna from the Lossiemouth Sandstone Formation (Upper Triassic) of Elgin (Moray, Scotland). For many years it was thought to be closely related to pterosaurs and dinosaurs, but the anatomy of this animal is difficult to interpret because of the notoriously poor preservation of the six available specimens, which comprise void space in the sandstone after the bones were destroyed by diagenesis. Historically, these fossils have been studied using physical molds, which provide only incomplete, and potentially distorted, information. Due to these uncertainties, interpretations of the anatomy, phylogenetic relationships, and paleobiology of Scleromochlus taylori have remained contentious. Here, we use microcomputed tomographic (μCT) techniques to redescribe and illustrate the osteology of Scleromochlus in detail, building upon a short redescription of keystone features of the anatomy that we recently published. We digitally visualize, describe, and figure previously inaccessible-and thus unaltered-portions of its skeleton, as well as providing new observations on the exposed parts of each specimen. This work reveals many novel features of the skull, mandible, trunk, tail, girdles, forelimb, and hindlimb (particularly of the manus, femur, and pes), demonstrating that historic molding techniques failed, in some cases, to accurately capture the anatomy of Scleromochlus. Our review sheds light on some of the most controversial aspects of Scleromochlus morphology showing that this taxon retains plesiomorphic features of Avemetatarsalia in the postcranial skeleton, alongside a suite of synapomorphies diagnostic of pterosauromorphs (the broad clade of pterosaurs and taxa more closely related to them than dinosaurs), particularly one subgroup, the lagerpetids. Consistent with recent work, our updated phylogenetic analyses (Maximum Parsimony and Bayesian Inference) demonstrate that Scleromochlus taylori is an avemetatarsalian archosaur that is recovered firmly in an early diverging position within Pterosauromorpha, as a member of Lagerpetidae, thus shedding important information on the origin of pterosaurs, the first group of vertebrates to evolve powered flight.

Synergy scenario for renewable energy production, CO2 and H2 storage in the Baltic offshore structure

CO2 Capture, Transport, Use and Storage (CCUS) is one of the core technologies to mitigate climate change. New techno-economic and techno-ecological concept of a synergy of CO2 geological storage (CGS), CO2 use, hydrogen (H2) production from different eco-friendly renewable energy recovery technologies and underground H2 storage (UHS), which we call here Geological Power Bank (Geo-PB), in Cambrian Deimena Formation sandstones in different compartments of the E6 structure offshore Latvia is presented for the first time. A five-phase circular economy concept of E6 geological structure energy and CO2 storage hub was developed in this study. The workflow is techno-ecological, eco-friendly, self-supporting, cost-competitive, and economically feasible. It consists of (1) CO2 transport by ships to the rig, (2) CO2 injection for CGS and CO2 Plume Geothermal technology (CPG), (3) H2 production, (4) Geo-PB, and (5) H2 transport by the same ships to the customers. The concept is supporting a win8 situation - innovative elements of techno-ecological synergy in one site: (1) CGS, (2) CPG, (3) solar energy, (4) wind energy, (5) sea currents energy, (6) H2 production (7) Geo-PB and (8) H2 transport to consumers. The proposed cycle is closed, demonstrating the principles of circular economy, which will increase the total efficiency of the concept. CGS and CPG are planned in the E6-A compartment of the E6 geological structure with an average CO2 storage capacity of 365 Mt in an optimistic approach and Geo-PB is planned in E6-B with an H2 storage capacity of 119 kt.The Baltic offshore scenario is ambitious and innovative, proposed new technologies, synergy with renewable energy (geothermal, solar, wind and sea current), large storage capacity, including CO2 storage and use captured by a CCUS clusters of emission sources from energy production, cement industry and bio-emissions from Estonia, Latvia and Lithuania. The concept aimed to decrease the artificial impact of climate change by avoiding CO2 emissions to the atmosphere and implementing circular economy principles. It will increase public and policymakers’ acceptance of new underground CO2 and energy storage technologies. The proposed synergy solution for CGS and energy storage projects will make such a business economically feasible and attractive for investors. Our study demonstrates a new era, the next generation of cost-competitive, self-supporting conceptual techno-ecological examples of a possible synergy of storage concepts with renewable energies combined using circular economy approaches.

Tracing source and palaeo‐weathering conditions of quartzose sandstone in the Cretaceous Cambay Basin: A combined petrographical, geochemical and geochronological approach

Based on detrital monazite dating, mineral chemistry of tourmaline and rutile, bulk rock geochemistry, modal analysis of petrographic and palaeocurrent data, this study tracks the source of quartzose sandstone within the Cretaceous succession of the Cambay Basin primarily to rocks within the Aravalli‐Delhi Fold Belt. Monazite geochronology shows predominant peaks around 506 ± 11 Ma, 905 ± 12 Ma and a minor peak at 750 ± 20 Ma, 1485 ± 30 Ma relating sediment sources to the Aravalli‐Delhi orogeny and Pan‐African orogeny. The petrographic modal analysis of the moderate‐to‐well‐sorted Himmatnagar Sandstone indicates at least 91% quartz, with minor feldspar and rock fragments. The mineral chemistry of tourmalines in Himmatnagar Sandstone matches with Li‐ and Ca‐poor granitoid, pegmatites, metapelites and quartz tourmaline rocks. The trace element content of rutiles in sandstones corresponds to metapelitic sources. Detrital monazite dates and mineral chemistry of tourmalines and rutiles pinpoint the sediment source to the South Delhi Supergroup of rocks. The dominance of rounded zircons and tourmalines and abraded quartz overgrowth in the Himmatnagar Sandstone indicate the recycling of sediments, possibly from the Marwar Supergroup. Palaeoclimatic proxies based on mineralogy and geochemistry, particularly, the high value (93–97) of mineralogical index alteration, indicate intense chemical weathering of the source rocks under humid climatic conditions. Therefore, the combination of factors, including the quartzo‐feldspathic source rocks, intense chemical weathering under humid climatic conditions and the recycling of sediments facilitated the formation of quartzose sandstone within the Himmatngar Sandstone in the Cambay Basin.