Sandstone Formation Research Articles

Geological Assessment of Turonian - Coniacian terrestrial sedimentation records during climatic recovery, Moreno Hill Formation, Zuni Basin

Understanding of Upper Cretaceous terrestrial sediments within the Western Interior Basin is advancing; however, the Turonian–Coniacian transition remains enigmatic. Recent chronometry of the Moreno Hill Formation indicates that sediment deposition took place during this interval of geodynamic upheaval and climatic recovery immediately following the peak of the Cretaceous Thermal Maximum (CTM). To decipher these effects, the sedimentary record of the Moreno Hill Formation was reassessed near the type section, and near Quemado, New Mexico (USA) using facies analysis and architectural reconstruction. Seven facies types (thirteen lithofacies codes), eleven architectural elements, and three facies associations were identified. Sedimentation within the floodplain of the lower Moreno Hill Formation was affected by the east-migrating forebulge of the Western Interior Basin. Furthermore, increasingly bedload-rich multi-story channel complexes and a transition from near-coastal to alluvial coals reflect gradual climatic cooling and overall regression of the Western Interior Seaway (with interruption by a regional [T2–R2] transgressive-regressive sequence). This is consistent with more subaerial conditions indicative of continued regression reflected within the floodplain sediments of the upper Moreno Hill Formation. Whilst diversion of westerly fluvial feeder systems by ongoing forebulge migration also affected sediment transport and deposition, a return to more suspended-load-rich single-story channels and thin coals are tied to an intervening (T3) transgression. Repetitive paleosol sequences throughout the Moreno Hill Formation indicate groundwater fluctuation in response to these base level changes. Together with detrital zircon-based geochronology, these slight sedimentary differences support a revised subdivision from three into two members: lower and upper. Beyond feeding the seaward Gallup Delta, the newly defined lower member correlates to the Toreva, Straight Cliffs (Smoky Hollow member), Ferron Sandstone, Funk Valley and Frontier formations (Dry Hollow Member) and the upper member to the Wepo and Straight Cliffs (John Henry Member) formations within the Kaiparowits, Notom, Last Chance and Vernal fluvio-deltaic systems. Landward sediments of the Cardium Formation (Canada) correlate with the lower and upper members of the Moreno Hill Formation.

Fracturing and Groundwater Productivity Linkages in the Koumfab Watershed in Northern Togo

The Koumfab watershed, located in the Dapaong region of northern Togo, overlies the sandstone-pelite formations of the lower megasequence of the Volta Basin and the granito-migmatitic bedrock of the south-eastern edge of the West African Craton. All of these Precambrian formations have a dense network of lineaments or fractures, giving them the characteristics of discontinuous and highly exploited aquifers. The lineament map of the Koumfab watershed, obtained from aerial photographs and the digital terrain model, identifies three main families of fractures running N-S to NE-SW (N0° to N40°), NE-SW to ESE-WNW (N60° to N110°) and ESE-WNW to SE-NW (N120° to N180°). Analysis of the correlation between lineaments and borehole flow rates has enabled us to identify areas with high storage potential. This potential is mainly controlled by lithological and lineament parameters. Boreholes drilled along kilometre-long lineaments underlain by crystalline and sandstone formations are more productive, with generally high flow rates (Q > 5m3/h). The basement formations found throughout the Koumfab catchment are major reservoirs with hydrogeological potential that are already in great demand.

An integrated density correction method of four-detector density logging in cased holes

Density logging is critical to shale oil and gas exploration. In density logging of cased holes, the inelastic gamma count and hydrogen index are closely related to the correction of formation density. Aimed at the problems of obtaining the pure inelastic gamma count and correcting the hydrogen index in density logging, the relevant research is implemented in the four detector logging tool. Firstly, a technique to separate the pure inelastic gamma count for density logging is provided. It is based on the pure count coefficient. Then on the basis of determining the density through the pure inelastic count ratio, the hydrogen index is corrected by the epithermal neutron and thermal neutron count ratio. Finally, the integrated density correction equation is proposed. The accuracy of this method is checked using a Monte Carlo model, which provides a strong experimental foundation. By examining the influencing factors, the results show that while the density after Halliburton correction is significantly impacted by borehole size, lithology, salinity, and borehole fluid, the density after integrated correction is least affected by these variables. Besides, the integrated density correction method is more favorable for large borehole size, low salinity and sandstone formation. Through logging examples, it is discovered that the overall uncertainty of the density log after the integrated density correction is lower than the Halliburton density correction log, with a maximum of only 0.013 g/cm3, indicating that the density results are more reliable. The study's findings offer a correction technique for precisely estimating the density of cased holes.

The Earliest Clastic Sediments of the Xiong’er Group: Implications for the Early Mesoproterozoic Sediment Source System of the Southern North China Craton

The volcanic activity of the Xiong’er Group and its concomitant sedimentation are related to the stretching–breakup of the Columbia supercontinent. The Dagushi Formation overlies the Paleoproterozoic Shuangfang Formation with an angular unconformity. The Dagushi Formation, as the earliest clastic strata of the Xiong’er Group and the first stable sedimentary cover overlying the Archean crystalline basement in the southern margin of the North China Craton, provides tectonic evolution information that predates Xiong’er volcanic activity. By distinguishing lithologic characteristics and sedimentary structures, we identified that the sedimentary facies of the Dagushi Formation were braided river delta lake facies from bottom to top. The U–Pb ages of the detrital zircons of the Dagushi Formation can be divided into four groups: ~1905–1925, ~2154–2295, ~2529–2536, and ~2713–2720 Ma, indicating the provenance from the North China Craton basement. Based on the geochemical characteristics of the Dagushi Formation, we suggest that the sediments accumulated rapidly near the source, which were principally felsic in nature, and were supplemented by recycled materials. The provenance area pointed to the underlying metamorphic crystalline basement of the North China Craton as the main source area with an active tectonic background. The Chemical Index of Alteration (CIA) values of the Dagushi Formation sandstone samples ranged from 60.8 to 76.7, indicating that the source rocks suffered from slight to moderate chemic chemical weathering. The Index of Composition Variability (ICV) values ranged from 0.8 to 1.3, which indicates the first cyclic sediments. The vertical facies and provenance changes of the Dagushi Formation reflect a continuous crust fracturing process that occurred in the North China Craton.

Effect of methylene blue on wetting characteristics of quartz/H2/brine systems: Implication for hydrogen geological storage

Hydrogen (H2) is considered a promising replacement for fossil fuels due to its enormous potential as an environmentally friendly and sustainable option compared to carbon-based fossil fuels. However, storing the vast quantity of H2 required to satisfy the global energy demand on the earth's surface can be difficult due to its compressibility and volatility. The best option for large-scale storage is underground H2 storage (UHS), which can be retrieved when needed. Rock wettability is vital in UHS because it determines the H2 storage capacity, containment security, and potential withdrawal and injection rates. Organic acid inherent in storage formations could make the storage rock H2-wet and reduce the residually trapped H2; thus, recent research efforts have concentrated on modifying sandstone formations contaminated with organic acid through chemical injections, such as nanofluids and methyl orange. However, previous research has not considered applying methylene blue (MB) as a rock wettability modifier to promote successful UHS. In addition, MB is a toxic constituent of wastewater, causing pollution. This research aims to dispose of MB in underground reservoirs to alter the wettability and increase the H2 storage capacity, mitigating anthropogenic carbon dioxide emissions. We assess the application of MB as a chemical agent for altering the wettability of quartz contaminated with stearic acid to promote H2 geological storage. Based on the contact-angle measurements, quartz aged with the optimum concentration of MB (100 mg/L) has the least advancing (θa= 35°), and receding (θr= 32°) angles at 13 MPa and 50 °C, changing the wettability to strongly water-wet. We demonstrate that an injection of MB into geological formations could make the rock water-wet, promoting H2 containment security and assisting in the large-scale implementation of UHS.

A new method in reservoir rock classification in carbonate and sandstone formations

Abstract This study aims to improve rock-type classification by analyzing core data based on the water–oil primary drainage capillary pressure method. A modified empirical equation is proposed using permeability, porosity, and irreducible water saturation to classify rock types based on water–oil primary drainage capillary pressure. We used primary drainage capillary pressure data measured in carbonate and sandstone samples in the Ahvaz Asmari and Mansouri oilfields to evaluate the characterization number (Cn) method. This study consists of two main parts. First, the Cn method is introduced to rock typing, and the permeability is calculated from well log data. In the second part, we present rock-type classification when the water saturation of the formation is more than the irreducible water saturation. The novelty of this work is a simple and efficient technique to rock-type classification using the Cn method. In addition, we present a procedure to assign rock types for the transition zone using the Cn method. Moreover, this study systematically investigates the role of irreducible water saturation in rock typing. The innovation of this work lies in its ability to classify rocks in heterogeneous reservoirs for carbonate and sandstone lithology and allow for the calculation of permeability more accurately from well log data. The comparison results between the Cn method and the flow zone indicator method show the robust clustering ability of the Cn method.

Effect of Physical Properties on Mechanical Behaviors of Sandstone under Uniaxial and Triaxial Compressions.

Mechanical properties of sandstone, such as compressive strength and young's modulus, are commonly used in the design of geotechnical structures and numerical simulation of underground reservoirs using models such as the digital groundwater, equivalent porous medium, and Discrete Fracture Network (DFN) models. A better understanding of the mechanical behaviors of sandstone under different loading conditions is imperative when assessing the stability of geotechnical structures. This paper highlights the effect of the physical properties (i.e., porosity, mean grain size) and environmental conditions (i.e., water content and confining stress) on uniaxial compressive strength, triaxial compressive strength, and young's modulus of sandstone. A series of uniaxial and triaxial compression experiments are conducted on sandstone formations from Wyoming. In addition, experimental data on sandstones from the literature are compiled and integrated into this study. Prediction equations for the compressive strengths and young's modulus of sandstone are established based on commonly available physical properties and known environmental conditions. The results show that the mean Uniaxial Compressive Strength (UCS) decreases as the porosity, water content, and mean grain size increase. Furthermore, a predictive empirical relationship for the triaxial compressive strength is established under different confinements and porosity. The relationship suggests that the mean peak compressive strength increases at a higher confinement and decreases at a higher porosity. The results and recommendations provide a useful framework for evaluating the strength and deformation of most sandstone.

Occurrence and Origin of Nanoscale Grain Boundary Channels Under Diagenetic Conditions

AbstractNatural fractures in shale and sandstone that formed under diagenetic and metamorphic conditions are frequently filled with mineral cement that lack residual fracture porosity visible under the petrographic microscope and that are generally interpreted to be impermeable. Scanning electron microscopy of calcite, dolomite, quartz, and barite fracture cement from low‐permeability, diagenetically altered shale and sandstone formations provides evidence of open and variably connected elongate pores or gaps with apertures of 10–600 nm, referred to as nanoscale grain boundary channels (NGBC). Electron backscatter diffraction of samples prepared using broad ion‐beam milling shows that NGBCs occur along grain boundaries of blocky or columnar fracture cement. Grain boundaries are either faceted or display undulation at the nanometer scale. NGBCs tend to increase in aperture with increasing maximum formation burial temperature, indicating dissolution‐precipitation kinetics influences grain boundary structure. Transmission electron microscopy reveals heterogeneous crystallographic domains with possible amorphous regions bridging across grain boundary channels. We propose a model of dynamic concurrent dissolution‐precipitation along grain boundaries that preserves NGBCs in carbonate and quartz fracture cements that have experienced diagenetic to low‐grade metamorphic conditions. While partially healed, NGBCs may be sufficiently connected to increase permeability of low‐permeability formations containing cemented fractures.

Geological Modeling of Sandstone Formations and Petrophysical Characterization of Hydrocarbon Reservoirs in the Termit Basin, Eastern Niger: Case of the Goumeri Prospect

This study focuses on the geological model of sandstone formations and the petrophysical characterization of hydrocarbon reservoirs in the Termit Basin. The specific objectives are: (1) to establish a geological model visualizing the geometry of reservoir rocks and (2) to visualize the spatial and vertical distribution of the petrophysical parameters (porosity, permeability). The methodological approach integrated the interpretation of lithology data and petrographic parameters from the logs by using Petrel software 17.4 versions. The interpretation of the obtained results shows that: the reservoir formations present in the shape of sand lenses whose thickness varies according to another prospect. The petrophysical parameter models including the porosity and permeability model were used to understand the vertical and spatial distribution of the different reservoir units.

Simulation of sandstone formation damage caused by solid particle invasion

During the drilling and completion process, the invasion of solid particles can have a serious impact on reservoir permeability, but there is a lack of effective prediction models for its impact. We developed a prediction model of solid particle invasion damage in response to the issue of reservoir damage induced by solid particle invasion during the exploitation of sandstone reservoirs. By considering the changes in pore permeability characteristics, particle migration and rock stress-strain state are coupled. The findings reveal that as filtration duration increases, the concentration of suspended particles and sediment particles increases, resulting in a progressive reduction in formation permeability around the wellbore. The greater the filtration coefficient, the greater the quantity of particle deposition, however, this also leads to a slowdown in the growth in deposition quantity. As the diffusion rate increases, particles are more likely to deposit. The concentration of suspended particles decreases progressively as tortuosity increases, as does the concentration of sediment particles. Large saturation sedimentation in the pore throat may cause more suspended particles to deposit, lower the effective seepage channel of the pore throat, and drastically impair formation permeability. The results of the impact factor comparison showed that filtration coefficient and medium tortuosity are the key factors. Improving the temporary plugging effect of solid particles in formations with large tortuosity of pore throats can effectively reduce reservoir damage. The findings of this study can help for optimization design of solid particles in drilling fluid for reservoir protection.

A novel semi-analytical model for pore volume compressibility in oil-bearing sandstone formations

Rock compressibility is an essential parameter in many petroleum engineering applications, specifically in reservoir modeling. It is an independent variable that is not measured in conventional core analysis but can be estimated through correlations or using hydrostatic or triaxial tests (if available). In this research, a new semi-analytical model was reconstructed to estimate the isothermal rock compressibility in sandstone formations. The newly derived model was validated using raw data collected from the upper sandstone member/Zubair formation of several oil fields in southern Iraq.In this research, analytical equations and some empirical correlations were used to formulate a semi-analytical model to predict the isothermal rock compressibility. The derivation started with the equations of dynamic elastic properties of Young's Modulus and Poisson's ratio parameters to derive the static state of these two parameters. Specifically, Johan Fuller's correlation was utilized to find the static Young's Modulus, which was used with Poisson's ratio to compute the static bulk modulus. In the final step of the derivation, the compressibility equation was simplified to be a function of porosity only, which eliminates the effect of the static bulk modulus.The predictions of the derived model were compared with laboratory test measurements of pore volume compressibility, porosity, and elastic rock properties, and an acceptable matching was achieved. To support the accuracy and robustness of the new model, the results were compared with several available empirical correlations, and better matching was obtained by computing the Absolute Percent Error (AAPE), Mean Square Error (MSE), and Absolute Root MSE (ARMSE).Consequently, the new pore volume compressibility equation matches lab-measured data significantly. However, the lab-measured data showed poor compatibility with available equations in the literature. Therefore, this model should be accurate and robust for compressibility estimation in other oil-bearing consolidated and unconsolidated sandstone formations. Additionally, the newly derived equation is simple, uncomplicated, and easy to use.

Study on the Mechanism and Prevention of Frequent Mine Seismic Events in Goaf Mining under a Multi-Layer Thick Hard Roof: A Case Study

Mine seismic events are an inevitable dynamic phenomenon occurring in deep mines. A scientific and rational method is needed to evaluate and understand mine seismicity and its induced disasters. In the Ordos mining area of North China, multiple groups of thick hard-bedded sandstone formations commonly exist in the overlying strata of Jurassic coal seams. In recent years, frequent mine seismic events in many large mines of Ordos have resulted in suspended or limited production, which seriously threatens the safe and efficient operation of 10-million-ton modern mines in China. Therefore, taking the frequent occurrence of mine seismic events in the mining process of goaf working face with a multi-layer thick hard roof in Ordos mine as the research background, this study investigated the mechanism and prevention of mine seismic in goaf working face with the methods of case study, theoretical analysis and field monitoring. The following conclusions are made: when the goaf working face is mined, an “advanced and lateral” L-form roof forms under the coupled influence of the lateral suspension plate formed above the upper working face and the roof of the working face. Due to the common influence from “advanced and lateral” L-form roof activation, the gradually breaking multi-layer thick hard roof, thick hard roof group bending and prying effects, in addition to excessively fast or uneven mining speed, mine seismic events will occur frequently when the exceedance warning index (EWI) is breeched. On this basis, coordinated blasting to break the roof along two roadways and within the working face is put forward as a measure with the purpose of preventing and controlling mine seismic events, and a robust effect on mine seismic reduction and disaster prevention is obtained in field application. The research results can serve as a reference for the development and application of mine seismic mechanism and blasting vibration reduction technology on the working face where there is a multi-layer thick hard roof, thereby supporting a strategy of promoting the resource development and energy security of deep mines.

Volcanoclastic and epiclastic diagenesis of sandstones associated with volcano-sedimentary deposits from the upper Jurassic, Lower cretaceous, Paraná Basin, southern Brazil

The opening of South Atlantic Ocean produced an immense volume of lava that covered an active aeolian system during Lower Cretaceous. The contact of Botucatu Formation sandstones with the Serra Geral volcanic flows generated a variety of volcano-sedimentary features and deposits. During volcanism, the temperature contrast between lava and wet or water-saturated sediments formed volcanoclastic features and related sedimentary deposits. In moments of magmatic quiescence, epiclastic deposits were generated due to the return of sedimentation. Volcanoclastic deposits include volcanic breccias with sandy matrix, and epiclastic deposits include conglomerates and conglomeratic sandstones with intraclasts. Quantitative petrography of the sandy matrix samples of these deposits was analyzed, in order to discuss the paragenesis of volcano-sedimentary interactions. Regular burial diagenetic processes were discussed for epiclastic sandstones and contact diagenesis processes for volcanoclastic sandstones. The original composition of volcanoclastic and epiclastic sandstones is heterogeneous. However, the main difference between them is the presence of textural fluidization indicators found in the volcanoclastic sandstones, along the lava-sediment interface. These textural characteristics indicate that the unconsolidated sediments were probably wet or saturated in water during the interaction with the volcanic flow. Epiclastic sandstones have infiltrated clays and neoformed smectites as their main diagenetic constituent due to alteration of available volcanic lithoclasts. For volcanoclastic sandstones, the formation of opal, chalcedony and megaquartz cements through burial is unlikely, due to the intergranular volume occupied by these cements, indicating near-surface early diagenetic conditions. Therefore, the mechanisms of dissolution and repreciptation of the siliceous fluids, incorporated in the system, formed mainly the chalcedony cementation. Furthermore, zeolite cementation, which occurs along the lava-sediment contact, is another important indicator of contact diagenesis for volcanoclastic sandstones. During telodiagenesis, the formation of secondary porosity by dissolution of volcanic lithoclasts and detrital K-feldspar grains was of great importance in volcanoclastic and epiclastic sandstones.

Localized host-rock porosity near sealed fractures at 7 km depth: Geochemical evidence of deep-seated porosity controls

In Cretaceous Bashijiqike Formation sandstone from 6.5 to 7 km depth in the Kelasu tectonic zone, Kuqa depression thin section observation, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), nano CT scanning and digital core reconstruction reveals localized host-rock porosity near sealed fractures. Primary interparticle pores are the main type, followed by some secondary (dissolved) pores at the edge of grains, interparticle secondary pores, intercrystalline pores and microfractures. Dolomite and calcite are the common fracture-filling minerals, while a few fractures are filled with gypsum and quartz. The phases that exist in fractures are progressively more common farther from the fracture. Thus there is a sort of halo around the fracture that is depleted in the phases that exist in the fracture. Although the types of pores are the same, the farther from the fracture, the tighter the rock, the lower the porosity and average pore size, and the weaker the inter-pore connectivity with local preservation of interparticle pores. We propose a mechanism for how this pore structure arises. This study enhances the understanding of the physical properties and pore-fracture interaction of deep tight reservoirs, and contributes to further accurate evaluation of reservoirs.

The role of methane seepage in the formation of the Northern Adriatic Sea geosites

The northern Adriatic Sea hosts patches of rock formations that have given rise to large biodiversity not otherwise found on the predominantly sandy and flat seabed. Various hypotheses have been invoked concerning the origin of these features, which are widespread in the northern Adriatic Sea and have been intensively studied since the eighteenth century. Here, we provide a significant advancement of knowledge in the lithification process associated with these peculiar rock formations. This study is based on geological, geophysical and mineralogical analyses performed on 45 rock outcrops identified in the study area. A key result of our analysis is the reconciliation of the different models related to the genesis of the northern Adriatic Sea outcrops, i.e., Holocene beach rocks that typically formed in the intertidal zone; cementation of paleo-channel systems, implying a groundwater influence; and methane-derived carbonates. Regardless of the depositional environment, we highlight the relationship between sediments and the processes that led to their evolution into the sandstone formation. We suggest that a common cementation process occurred in the various sedimentary deposits that are representative of different environments of the northern Adriatic Sea and was related to the post depositional precipitation of methane-derived carbonates. Our findings highlight the potential key role of widespread methane seepage from very shallow marine environments into the water column and then, eventually, into the atmosphere as a potential source of an increasing greenhouse gas.

Depositional and diagenetic controls over reservoir quality of tight sandstone and conglomerate in the lower Cretaceous Shahezi formation, Xujiaweizi fault depression, Songliao basin, China

The distribution of high-quality reservoirs restricts the exploration and development of tight gas in the Shahezi Formation in the Xujiaweizi Fault Depression, but the complex sedimentary composition and abundant diagenesis make it difficult to determine which rocks are high-quality reservoirs. In this paper, the petrological, mineralogical, and pore structure characteristics of sandstone and conglomerate were investigated to elucidate how depositional and diagenetic processes jointly control reservoir quality and identify favorable sequences in which high-quality reservoirs are distributed. The results showed that the content and type of matrix and lithic clasts in the sedimentary rock unit controlled the effects of the following diagenetic sequence, which in turn controlled the reservoir porosity, permeability and pore size distribution. Conglomerate and coarse-to medium-grained sandstone, both with a low muddy matrix content and high intermediate–basic volcanic lithic clast content, underwent extensive dissolution or grain fracturing during diagenesis, resulting in a reservoir with pore spaces >0.1 μm in diameter, which is considered as a high-quality reservoir for tight gas exploration. Conglomerate and fine-grained silty sandstone, both with a high muddy matrix content and low intermediate–basic volcanic lithic clasts, or those reservoir units directly adjacent to mudstone often experienced severe mechanical compaction or cementation during diagenesis. This resulted in a reservoir dominated by micropores (<0.1 μm) and therefore formed nonreservoir areas for tight gas exploration. High-quality reservoirs are more likely to be developed in the lacustrine transgressive systems tract and regressive systems tract in sequence four of the Shahezi Formation in the Xujiaweizi Fault Depression.

Ichnology of a Middle Devonian regression: Environment, terrestrialization and true substrate controls on trace fossils of the Hangman Sandstone Formation, SW England

The Eifelian-aged Hangman Sandstone Formation of southwest England is a unit of the ‘Old Red Sandstone’ that has traditionally been considered relatively barren of trace fossils. Following recent investigations, we here show it to contain the most diverse Middle Devonian non-marine ichnofauna known globally. The fluvial-lacustrine facies of its constituent Trentishoe Member contain representatives of 21 ichnogenera including Archaeonassa, Arenicolites, Beaconites, Bifungites, Circulichnis, Cruziana, Diplichnites,?Gluckstadella, Gordia,?Halimededes,?Lockeia, Merostomichnites, Palmichnium, Petalichnus, Planolites, Polarichnus, Rusophycus, Siskemia, Spirophyton, Steinsfjordichnus, and Taenidium, as well as several microbially induced sedimentary structures. The transitional marine-influenced facies of the underlying Hollowbrook Member are less extensively exposed but contain four additional unique ichnogenera in the form of Cochlichnus, Halopoa, Phycodes, and Teichichnus, as well as further examples of Cruziana, Planolites and Taenidium. A revised ichnological assessment of the unit reveals several notable features, including the youngest known example of the arthropod refugia trace, Polarichnus, as well as a transitional trace fossil form of Diplichnites-Beaconites, demonstrating that the latter was produced by arthropods. As the Hangman Sandstone Formation records the culmination of a marine regression, its ichnofauna can be compared with that of the conformably underlying Lynton Formation, which was deposited in a sandy marine shelf setting. The ichnological differences between these units are acute, with 88% of the Hangman Sandstone Formation trace fossils being exclusive to non-marine or transitional facies. This observation sheds light on the terrestrialization process and indicates that the segregation of marine and non-marine trace fossil communities had accelerated by the Middle Devonian. Internal variability in ichnological signatures within the Hangman Sandstone Formation is also pronounced, with greater ichnodiversity and ichnodisparity in distal fluvio-lacustrine facies than in proximal fluvial facies. By viewing the depositional environment of the unit as a regionally extensive distributive fluvial system, this variability can be partly explained by a bias arising from the distribution of true substrates (bedding planes that demonstrably preserve an ancient sediment-air interface) in the unit, with such phenomena being more readily preserved in the lower energy outer reaches of the depositional system.

Numerical Simulations of Carbon Dioxide Storage Efficiency in Heterogeneous Reservoir Models

The U.S. Department of Energy’s National Energy Technology Laboratory (DOE-NETL) has been developing methods and tools (the online Carbon Dioxide Storage prospeCtive Resource Estimation Excel aNalysis (CO2-SCREEN) tool) to estimate carbon dioxide (CO2) storage potential in subsurface reservoirs. The CO2 storage efficiency terms are input in the tool to calculate storage potential in targeted reservoirs. In this effort, two CO2 storage efficiency terms were evaluated: volumetric displacement ( E V ) and microscopic displacement ( E d ). The first term deals with efficiency of CO2 propagation into an accessible reservoir volume, while the second term evaluates effectiveness of native fluid displacement with CO2. The interpreted well logs and core sample measurements were applied to create the heterogeneous reservoir models including geostatistical realizations of porosity and intrinsic permeability fields. Supercritical CO2 was injected over the course of 30 years into brine-saturated reservoir models for clastics, limestone, and dolomite lithologies and deltaic fluvial, aeolian, shallow marine, and reef depositional environments by means of varying reservoir parameters and injection scenarios. The reservoir models providing vertically heterogeneous petrophysical properties and designated as “layered reservoir models” (with homogeneous parameters along each layer of the model) were not determined to be a transition between the homogeneous and heterogeneous models in respect to storage efficiency. Another finding shows that high-efficiency factors do not necessarily mean increased CO2 storage; they rather indicate that the available volume and pore space are more fully utilized. The CO2 storage efficiency factors were evaluated dynamically at the select time points using P 10 ‐ P 50 ‐ P 90 percentiles. The results of this study show that the P 10 ‐ P 90 distribution for volumetric efficiency is wider when compared to the microscopic efficiency. It was found that where dominant buoyancy forces drive the plume to the top of a target formation, the volumetric efficiency is low. Tighter sandstone and carbonate formations show prevalence of capillary forces and better utilization of reservoir volume.

High-resolution calcareous nannofossil biostratigraphy and facies of Nimar Sandstone Formation (Bagh Group), central India and its bearing on Oceanic Anoxic Event 2

It is proposed to consider Narmada Valley Late Cretaceous sequences in three sectors with proper selection of stratotype in each sector: Eastern Sector: comprising of Lameta group of rocks with type area in Jabalpur area, essentially laid down in lacustrine-paedogenic milieu and containing a variety of fossils including dinosaur remains of Late Maastrichtian age. No evidence of sea incursion is available in the Eastern Sector either via the Narmada lineament or the K-G Basin. Central Sector: comprising of the Bagh Group in ascending order of: Nimar Sandstone Formation–Nodular Limestone Formation–Coralline-Bryozoan Limestone Formation, laid down in estuarine complex entirely within Turonian without any evidence of Cenomanian and Coniacian age calcareous nannofossils or other fossils being present. In the western part of Central Sector: Siliciclastic rocks and limestones referred to as Nimar Sandstone Formation curiously lack Late Cenomanian marker species, hence could be of Early Turonian age. Western Sector: comprises of Lacustrine sediments associated with Deccan Flood Basalt. The absence of the Cenomanian/Turonian Boundary and Black shales negates the presence of global OAE2 events in the Narmada lineament, but several OAE events are recognised in the Cauvery Basin, southeastern India. Uranium- and Thorium-rich Lower and Upper Nimar Sandstone Formation overlying crystalline basement are interpreted to have been essentially laid down in a fully marine estuarine milieu with reworked plant, and palynofossils including dinosaur remains. Calcareous nannofossils recovered from Upper Nimar Sandstone Formation over four decades ago and assigned Late Turonian age is revised based on modern data incorporating calcareous nannofossil and planktonic foraminifera datum and now suggest an older age of Early Turonian matching a zone with FAD of Quadrum gartneri at the base and FAD of H. helvetica at the top. It must be emphasised that except for the solitary and unique incursion of Early Turonian (ca. 93.9 Ma) sea along the Narmada lineament reaching eastward (&gt;300 km) up to the present town of Indore, no other marine intrusion ever took place on Indian shield except along collision facing Subathu–Dogadda lineament during Late Maastrichtian. It would be erroneous to suggest that the global eustatic rise of sea level caused the entry of the Turonian sea along the Narmada lineament; instead, it was earlier speculated by me that Large Igneous Province activity of Mahajanga Flood Basalt of Madagascar (ca. 93.9 Ma) could have most probably caused a short-lived Turonian sea to enter Narmada lineament from the west around C/T boundary.

Computed X‐ray Tomography Investigation of Porosity and Permeability of the Liujiagou Formation Sandstone Exposed to CO2‐Saturated Brine

AbstractIn order to improve CO2 capture, utilization and storage (CCUS) to solve carbon emission, sandstone from the Triassic Liujiagou Formation (LF) from the Ordos Basin in China was investigated using permeability tests and computed X‐ray tomography (CT) scanning. The presence of reactive minerals within the geological CO2 sequestration target storage formation can allow reaction with injected CO2, which changes the porosity and permeability of the LF beds, affecting storage effectiveness. To investigate the effect of chemical reactions on the pore structure and permeability of sandstone cores representing the LF CO2 storage, tests were conducted to analyze the changes in porosity and permeability of sandstone cores induced by CO2‐saturated brine at different reaction times (28‐day maximum reaction period). Porosity and permeability of the sandstone increased after reaction with CO2‐saturated brine due to mineral dissolution. The sandstone exhibited an increase in porosity and permeability after 15 days of reaction with CO2‐saturated brine. Moreover, there was an increase in the volume of large pores in the sandstone after the 28‐day period. The pore network of the sandstone was established through CT results, and the porosity calculated based on the obtained pore network was close to that measured in the test, demonstrating the feasibility to use CT to study the evolution of the microstructure of sandstone after long‐time exposure to CO2‐saturated brine.