Porosity Loss Research Articles

Abaloparatide prevents immobilization-induced cortical but not trabecular bone loss after spinal cord injury.

Spinal cord injury (SCI) causes severe and resistant sublesional disuse bone loss. Abaloparatide, a modified parathyroid hormone related peptide, is an FDA approved drug for treatment of severe osteoporosis with potent anabolic activity. The effects of abaloparatide on SCI-induced bone loss remain undefined. Thus, female mice underwent sham or severe contusion thoracic SCI causing hindlimb paralysis. Mice then received subcutaneous injection of vehicle or 20 μg/kg/day abaloparatide for 35 days. Micro-computed tomography (micro-CT) analysis of the distal and midshaft femoral regions of the SCI-vehicle mice revealed reduced trabecular fractional bone volume (56%), thickness (75%), and cortical thickness (80%) compared to sham-vehicle controls. Treatment with abaloparatide did not prevent SCI-induced changes in trabecular or cortical bone. However, histomorphometry evaluation of the SCI-abaloparatide mice demonstrated that abaloparatide treatment increased osteoblast (241%) and osteoclast (247%) numbers and the mineral apposition rate (131%) compared to SCI-vehicle animals. In another independent experiment, treatment with 80 μg/kg/day abaloparatide significantly attenuated SCI-induced loss in cortical bone thickness (93%) when compared to SCI-vehicle mice (79%) but did not prevent SCI-induced trabecular bone loss or elevation in cortical porosity. Biochemical analysis of the bone marrow supernatants of the femurs showed that SCI-abaloparatide animals had 2.3-fold increase in procollagen type I N-terminal propeptide, a bone formation marker than SCI-vehicle animals. SCI groups had 70% higher levels of cross-linked C-telopeptide of type I collagen, a bone resorption marker, than sham-vehicle mice. These findings suggest that abaloparatide protects the cortical bone against the deleterious effects of SCI by promoting bone formation.

Diagenetic Facies and Their Controls on the Quality of Tight Sandstone Reservoirs: A Case Study from the Upper Paleozoic Gas Reservoir in the Eastern Ordos Basin, North China

Diagenetic facies play a significant role in the evaluation and prediction of reservoirs as they comprehensively reflect the spatial distribution characteristics of deposition, diagenesis, and petrophysical properties. Based on the petrographic observation and considering pores, lithology, and diagenesis types, the diagenetic facies types were identified, and the pore evolution process and its influence on the quality of low permeability tight gas reservoirs were analyzed. The results show that six types of diagenetic facies were identified, including siliceous cementation intergranular pore facies (A), carbonate dissolution pore facies (B), matrix dissolution pore facies (C), clastic dissolution pore facies (D), matrix filling and strong compaction tight facies (E), and carbonate cementation and metasomatism tight facies (F). The evolution process of porosity shows that the restored original porosity is indicated to be between 34.2% and 36.0%. The average porosity loss caused by compaction was 17.1%, while the average porosity loss caused by cementation is 14.1%. The average porosity increased by 2.5% on diagenetic facies B, C, and D due to dissolution. Consequently, diagenetic facies A with weak compaction and diagenetic facies B, C, and D with strong dissolution are effective reservoirs with porosity greater than 6.6% and permeability greater than 0.25 − 0.6 × 10 − 3 μm2. The distribution areas of A, B, C, and D are favorable areas for tight gas exploration and are important indicators for the prediction of tight gas in the Upper Paleozoic Shanxi Formation in the eastern Ordos Basin. This study provides a new petrographic method for reservoir prediction and exploration of natural gas, which has practical value and economic significance.

Diagenetic controls on pore structure variations in fan deltaic sandstones of the Eocene Shahejie Formation, Bohai Bay Basin, China: Implications for reservoir quality and oiliness heterogeneities

The fan deltaic sandstones in the third section of the third member of the Eocene Shahejie Formation (Es33) are important hydrocarbon exploration targets in the northern Nanpu sag, Bohai Bay Basin, China. The Es33 sandstones are characterized by highly variable pore structures. A total of 364 Es33 sandstone samples were measured by a series of petrological and petrophysical analyzes to investigate these variations and their controls on reservoir quality and oiliness heterogeneities. The heterogeneity of Es33 sandstone can be manifested by type I, type II and type III pore structures. Primary intergranular pores and dissolution pores were the main storage spaces for type I sandstones, while dissolution pores and intercrystalline pores were the main storage spaces for type II and type III sandstones, respectively. These results indicate that compaction is the main factor in the loss of primary intergranular porosity, with an average loss of 78%. The grain size controlled the preservation of primary pores in Es33 sandstones with a carbonate cement content of less than 6%. The different types of clay minerals have various effects on the pore structure. Chlorite plays an active role in the preservation of intergranular pores and the improvement of reservoir quality, while mixed layers of illite and smectite greatly reduced the pore size and connectivity and lowered the reservoir quality. The Es33 sandstones have undergone a more open diagenetic system. Dissolution significantly increased the porosity of type I and type II sandstones with more primary intergranular pores, but exerted a minor role in contributing to the permeability. Furthermore, a pore‐throat radius of approximately 0.4 μm is considered to be the threshold for oil accumulation in Es33 fan deltaic sandstones.

Rock acoustics of CO2 storage in basalt

SUMMARY We simulate variations in the P- and S-wave velocities due to CO2 injection in basalt, caused by water replacement and mineralization in the form of carbonate cements. Carbonization can be monitored with seismic data on the basis of changes in velocity. We consider basalts composed of (Fe, Ca and Mg) minerals mainly, and the pore space is assumed to be initially saturated with water. The mineralization is based on a model that estimates the volume of precipitated cement and resulting porosity loss, and the velocities as a function of injection time are calculated with a patchy cement model. In the example, there are two stages: 1 week of CO2 injection and 29 weeks of frame cementation. After 1 week, water has been replaced by CO2, where density and P-wave velocity decrease, and cementation implies an increase in bulk density, P-wave velocity, whereas porosity and surface area are reduced. To our knowledge there are no models relating the effects of carbon mineralization on seismic properties. The present model can be applied to other rocks, where CO2 injection induces mineralization and storage.

Main controlling factors and oil-bearing potential characteristics of a tight sandstone reservoir: A case study of southwest Ordos Basin

Clarifying the main controlling factors of reservoirs and their oil-bearing potential is vital for predicting tight sandstone reservoirs. The Chang 8 reservoir in the southwest of Ordos Basin is a typical tight sandstone reservoir and is widely distributed. Observation description and sampling analysis of cores, the grain size analysis, casting thin section, scanning electron microscope, mercury pressure, nuclear magnetic resonance, and conventional physical analysis are used to clarify the main controlling factors and oil-bearing potential characteristics of the Chang 8 reservoir in southwest Ordos Basin. The results show that delta front subfacies are mainly developed in Chang 8 member, including distributary channel, natural dike, estuary bar and distributary bay. The main rock type of reservoir is lithic feldspathic sandstone, followed by feldspathic lithic sandstone. The types of reservoir space are mainly intergranular pores and intragranular dissolved pores, with a small amount of clay-related pores and micro-fractures. The average porosity and permeability of the reservoir are 11.67% and 0.52 × 10−3μm2, respectively. The reservoirs with high oil saturation are mainly distributary channels and thicker mouth bar sand bodies. Compaction is the main factor of reservoir compaction (porosity loss rate is 55.73%), followed by cementation (porosity loss rate is 29.23%). The favorable diagenesis is the dissolution of feldspar grains and some cement. The Chang 8 tight reservoir contains various nano-scale pore-throat. For tight reservoirs with similar physical properties, the pore-throat structure controls the oil saturation of the tight reservoir. Favorable conditions for tight sandstone reservoirs oil saturation include favorable sedimentary environment (distributary channel or thick mouth bar) and suitable microscopic pore characteristics.

Depositional and diagenetic controllers on the sandstone reservoir quality of the late cretaceous sediments, Gulf of Suez Basin

The complex depositional, burial, and diagenetic histories of the Late Cretaceous Nezzazat Group sandstones in Northeastern Africa present the main challenges with regard to reservoir quality. The quality of commercial reservoirs is maintained despite deep burial and the associated high temperature and pressure. The study presents an optimum integration of different data sets to address reservoir quality and reservoir performance controllers. The data set includes measured porosity and permeability, petrographic point-counting data, grain-size analysis, X-ray diffraction data, scanning electron microscopy, and porosity loss by compaction. The depositional controls on the reservoir quality are the facies, whereas the higher quality is found in the channel and upper shoreface settings. The coarse-grained sandstone is associated with better reservoir quality. The large intergranular porosity is the main porosity controlling the fluid flow. The massive and laminated sandstones are the best quality facies. The labile grains (feldspars and mica) control the permeability distribution. Whereas the secondary diagenetic controllers are the carbonate cementation that inhibited the effects of compaction. The siderite cementation has resulted in a micropore dominated and highly tortuous pore system. Total porosity has largely been preserved in the siderite-cemented sample but virtually eliminated in the dolomite cemented. A low volume of illite is associated with better reservoir quality. Whereas the better reservoir quality is associated with the abundant quartz cementation that protected the primary porosity from compaction. Compaction acts as a significant porosity loss factor during diagenesis. Authigenic kaolinite does not significantly affect the reservoir quality. The reservoir sensitivity to formation damage comes from the potential for fines (kaolinite, illitic clays, siderite, and pyrite) migration within the pore system that is readily mobilized by the fluid flow.

Impact of magmatic intrusion on diagenesis of shallow marine sandstones: An example from Qasim Formation, Northwest Saudi Arabia

Igneous intrusions are common in sedimentary basins, and their occurrence can significantly affect the diagenesis and reservoir quality evolution of sandstones, thereby strongly impacting their hydrocarbons-, geothermal-, and CO2-storage potentials. The Qasim sandstones in the Tabuk region (NW Saudi Arabia) experienced shallow burial diagenesis (<2 km) when the Tertiary magma intruded to form basaltic sills (0.4–4 m thick). The sedimentology, tectono-stratigraphic framework, provenance, and chemostratigraphy of the Qasim Formation have been extensively covered in the literature. However, the impact of the magmatic intrusion on diagenesis and reservoir quality evolution of the sandstones remains enigmatic. This study employed thin-section petrography, QEMSCAN, XRD, SEM, and energy-dispersive spectrometer analyses to investigate the role of magmatic intrusion on diagenesis and reservoir quality of the Qasim sandstones. The results of the study indicate that reservoir porosity is principally influenced by primary depositional characteristics (grain size and sorting), diagenetic alterations, and magmatic intrusions. Sandstones with coarser grain size and better sorting have the best intergranular porosity and vice versa. The “normal” diagenetic processes that have significantly affected the reservoir porosity of the sandstones occurred during both shallow burial (eodiagenesis) and uplift (telodiagenesis). The eogenetic alterations include mechanical compaction, early diagenetic cementation by calcite, pyrite, and kaolinite, whereas the telogenetic alterations include the formation of kaolinite, goethite, hematite. Overall, mechanical compaction is the main driver for porosity loss in the sandstones. The intrusion-related diagenetic processes include the dissolution of quartz grains, rounded quartz overgrowths, and calcite cement, and the transformation of kaolinite into dickite and chlorite. Detrital quartz and rounded quartz overgrowths have undergone dissolution due to acidic pore fluids from magma and high temperature. The transformation of kaolinite into dickite occurred in a dissolution-recrystallization fashion, and the amounts of kaolinite and dickite increase in fine-grained sediments away from sill contact due to hydrodynamic processes that deposited muscovite (which form kaolinite) in low energy environments. The chloritization of kaolinite was localized, and the magma-induced dissolution of goethite likely supplied the requisite high Fe content. Additionally, the intrusion has resulted in the dissolution of the early calcite and increase in porosity towards the sill contact. However, values for compactional porosity loss have relatively remained similar both at and away from the sill contact, as the sill is too thin to exert significant vertical loading. This study has relevance to understanding hydrocarbon exploration and exploitation in sediment-lava sequences, and to understanding the development of sediment-lava systems.

Non-solvent post-modifications with volatile reagents for remarkably porous ketone functionalized polymers of intrinsic microporosity

Chemical modifications of porous materials almost always result in loss of structural integrity, porosity, solubility, or stability. Previous attempts, so far, have not allowed any promising trend to unravel, perhaps because of the complexity of porous network frameworks. But the soluble porous polymers, the polymers of intrinsic microporosity, provide an excellent platform to develop a universal strategy for effective modification of functional groups for current demands in advanced applications. Here, we report complete transformation of PIM-1 nitriles into four previously inaccessible functional groups – ketones, alcohols, imines, and hydrazones – in a single step using volatile reagents and through a counter-intuitive non-solvent approach that enables surface area preservation. The modifications are simple, scalable, reproducible, and give record surface areas for modified PIM-1s despite at times having to pass up to two consecutive post-synthetic transformations. This unconventional dual-mode strategy offers valuable directions for chemical modification of porous materials.

The importance of facies, grain size and clay content in controlling fluvial reservoir quality – an example from the Triassic Skagerrak Formation, Central North Sea, UK

Clay-coated grains play an important role in preserving reservoir quality in high-pressure, high-temperature (HPHT) sandstone reservoirs. Previous studies have shown that the completeness of coverage of clay coats effectively inhibits quartz cementation. However, the main factors controlling the extent of coverage remain controversial. This research sheds light on the influence of different depositional processes and hydrodynamics on clay-coat coverage and reservoir quality evolution. Detailed petrographic analysis of core samples from the Triassic fluvial Skagerrak Formation, Central North Sea, identified that channel facies offer the best reservoir quality; however, this varies as a function of depositional energy, grain size and clay content. Due to their coarser grain size and lower clay content, high-energy channel sandstones have higher permeabilities (100–1150 mD) than low-energy channel sandstones (<100 mD). Porosity is preserved due to grain-coating clays, with clay-coat coverage correlating with grain size, clay-coat volume and quartz cement. Higher coverage (70–98%) occurs in finer-grained, low-energy channel sandstones. In contrast, lower coverage (<50%) occurs in coarser-grained, high-energy channel sandstones. Quartz cement modelling showed a clear correlation between available quartz surface area and quartz cement volume. Although high-energy channel sandstones have better reservoir quality, they present moderate quartz overgrowths due to lesser coat coverage, and are thus prone to allowing further quartz cementation and porosity loss in ultra-deep HPHT settings. Conversely, low-energy channel sandstones containing moderate amounts of clay occurring as clay coats are more likely to preserve porosity in ultra-deep HPHT settings and form viable reservoirs for exploration. Supplementary material: of data and technique used in this study are available at https://doi.org/10.6084/m9.figshare.c.6438450

Integrating Self-Partitioned Pore Space and Amine Functionality into an Aromatic-Rich Coordination Framework with Ph Stability for Effective Purification of C2 Hydrocarbons.

A great demand for high-purity C2 hydrocarbons calls for the development of chemically stable porous materials for the effective isolation of C2 hydrocarbons from CH4 and CO2. However, such separations are challenged by their similar physiochemical parameters and have not been systematically studied to date. In this work, we reported a cadmium-based rod-packing coordination framework compound ZJNU-140 of a new 5,6,7-c topology built up from a custom-designed tricarboxylate ligand. The metal-organic framework (MOF) features an aromatic-abundant pore surface, uncoordinated amine functionality, and self-partitioned pore space of suitable size. These structural characteristics act synergistically to provide the MOF with both selective recognition ability and the confinement effect toward C2 hydrocarbons. As a result, the MOF displays promising potential for adsorptive separation of C2-CH4 and C2-CO2 mixtures. The IAST-predicted C2/CH4 and C2/CO2 adsorption selectivities, respectively, fall in the ranges of 7.3-10.2 and 2.1-2.9 at 298 K and 109 kPa. The real separation performance was also confirmed by dynamic breakthrough experiments. In addition, the MOF can maintain skeleton intactness in aqueous solutions with a wide pH range of 3-11, as confirmed by powder X-ray diffraction (PXRD) and isotherm measurements, showing no loss of framework integrity and porosity. The excellent hydrostability, considerable uptake capacity, impressive adsorption selectivity, and mild regeneration make ZJNU-140 a promising adsorbent material applied for the separation and purification of C2 hydrocarbons.

Diagenetic Evolution and Its Impact on Reservoir Quality of Tight Sandstones: A Case Study of the Triassic Chang-7 Member, Ordos Basin, Northwest China

The Upper Triassic Chang-7 Member of the Ordos Basin contains typical tight sandstone reservoirs. Reservoir quality is affected by diagenesis, which is a critical factor in tight oil exploration. In this study, the Chang-7 Member tight sandstones were studied by a variety of experimental methods, including thin sections, scanning electron microscopy (SEM), and X-ray diffraction (XRD), to determine the reservoir characteristics and diagenesis and discuss their influences on the reservoir quality. The Chang-7 Member sandstones are mainly lithic arkose and feldspathic litharenite with an average porosity and permeability of 7.17% and 0.13 mD, respectively. The pore type is mainly primary intergranular pores, and the secondary pores are feldspar dissolved pores, which are relatively developed, with pore radii of 2–20 µm. Diagenesis of Chang-7 Member tight reservoirs mainly includes compaction, quartz cementation, carbonate cementation, clay mineral cementation, and dissolution. The diagenetic stage develops into Mesodiagenesis A. The average porosity loss from compaction and cementation of sandstone in the Chang-7 Member is 15.93% and 18.67%, respectively. With the increase in burial depth, the porosity and permeability of the reservoir gradually decrease. In mesodiagenesis, the authigenic illite and carbonate cementation compacts the reservoir. The acid fluid carried by the two stages of oil and gas filling during diagenesis dissolved feldspar and carbonate cement, which plays a certain role in transforming the tight reservoir.

A novel approach for fracture porosity estimation of carbonate reservoirs

AbstractThe quality of carbonate reservoirs is linked to their rock properties and surrounding stress settings which can play a vital role in their production optimization and development programs. Imposing various stresses can increase porosity and permeability by creating joints and cracks across the rock mass. Therefore, developing methods to identify and accurately evaluate fractures in carbonate reservoirs is very significant in reservoir characterization. To deal with this necessity, we developed a fracture porosity estimation method using empirical and analytical solutions based on the wireline data considering stress conditions. The proposed methodology was applied to a carbonate reservoir as the case study. As fracture porosity is sensitive to stress, experimental tests were conducted on the core samples using triaxial hydrostatic tests. These tests are needed to simulate reservoir conditions to investigate the relationships between fracture volume fraction and the applied stress. A substantial porosity loss was observed during the hydrostatic test, which can be linked to the crack porosity closure. The reliability of our results was validated by thin section, computed tomography–scan images, velocity deviation method, elastic boundary laws, and image logs. Eventually, we introduced an equation to estimate in situ fracture porosity from the relationship between porosity and effective confining pressure. We verified the repeatability and generality of our proposed methodology using a blind well, and the results indicate a comparable level of accuracy. Our findings are applicable for estimating crack porosity for rock physics modelling purposes of detecting fracture zones in the absence of image logs and core data. Moreover, by calibrating and optimizing the constant parameters in our proposed relationship, one may further estimate crack density in any other given carbonate reservoirs.

The effect of clay and contacts between sand grains on the elastic properties of sandstones

AbstractHigh‐porosity sandstones are important for hydrocarbon production, underground CO2 storage, extraction of geothermal energy and freshwater aquifers. Porosity of sandstones may be estimated using elastic wave velocities, but these depend also on fluid saturation, clay content, pore shape and contacts between sand grains. An understanding of how elastic properties of sandstones depend on these factors is important for characterizing their storage potential and for geomechanical issues, such as sanding, borehole stability, reservoir compaction and fracturing. Ultrasonic velocity measurements in clay‐bearing sandstones indicate that much of the clay in shaly sandstones is non‐load‐bearing. This enables a simple approach for modelling the elastic properties of shaly sandstones that includes the effect of pore concavity and agrees with ultrasonic P‐ and S‐velocities measured in the laboratory. Despite this agreement, some clay may reside within the contacts and may act to inhibit the development of quartz cement, thus reducing porosity loss and helping to preserve storage volume. This appears to be the case for the Lower Mt. Simon Sandstone, a target formation for underground storage of CO2 in the Illinois Basin, for which the bulk moduli agree with the predicted bulk moduli, but the shear moduli are lower than predicted. This appears to result from an increase in a shear compliance of the grain contacts that may enable sliding along the grain contacts and increase the tendency to shear failure.

ZIF-8 Pellets as a Robust Material for Hydrogen Cryo-Adsorption Tanks.

Cryoadsorption on the inner surface of porous materials is a promising solution for safe, fast, and reversible hydrogen storage. Within the class of highly porous metal-organic frameworks, zeolitic imidazolate frameworks (ZIFs) show high thermal, chemical, and mechanical stability. In this study, we selected ZIF-8 synthesized mechanochemically by twin-screw extrusion as powder and pellets. The hydrogen storage capacity at 77 K and up to 100 bar has been analyzed in two laboratories applying three different measurement setups showing a high reproducibility. Pelletizing ZIF-8 increases the packing density close to the corresponding value for a single crystal without loss of porosity, resulting in an improved volumetric hydrogen storage capacity close to the upper limit for a single crystal. The high volumetric uptake combined with a low and constant heat of adsorption provides ca. 31 g of usable hydrogen per liter of pellet assuming a temperature-pressure swing adsorption process between 77 K - 100 bar and 117 K - 5 bar. Cycling experiments do not indicate any degradation in storage capacity. The excellent stability during preparation, handling, and operation of ZIF-8 pellets demonstrates its potential as a robust adsorbent material for technical application in pilot- and full-scale adsorption vessel prototypes.

The secondary pore development model of coarse-grained deposition: A case study of the Xiazijie Formation in the Northwestern Margin of the Junggar Basin

The coarse-grained glutenite rock mass of the proximal fan delta is characterized by the blocky texture, mixing of gravels with varied sizes, high mud content, and low porosity and permeability, leading to difficulties in assessment and exploration of oil and gas enrichment regularities of tight glutenite. The Permian Xiazijie Formation in the northwest margin of Junggar Basin has a set of tight glutenite reservoirs, and the reservoir quality is an important controlling factor for oil and gas enrichment. Based on three-dimensional earthquake, casting thin sections, rock physical property, geochemistry, the sedimentary facies division, petrologic features, physical property regularities, pore types and diagenesis of Xiazijie Formation were analyzed. This research develops the pore evolution model of the coarse-grained deposition via the quantitative analysis of porosity evolution. First, during the rapid compaction, intensive mechanical compaction results in reduction of the original porosity from 29.8% to 15.1%. Secondly, the cement formed during the eodiagenesis destructs the reservoir space and leads to an average porosity loss of 6.5%. Third, dissolution effectively improves reservoir quality. It mainly dissolves the zeolite cement, and the porosity grows to 12.1% from 8.6%. The dissolution occurs during the main hydrocarbon expulsion stage of the source rock, which is in favor of hydrocarbon emplacement. Fourth, during the telodiagenesis with the deepening burial and intensifying pressure solution, siliceous and carbonate cement precipitate, the reservoir physical property is degraded again, the porosity loss is about 3.4%. After a series of complex diagenetic processes, the current tight glutenite reservoir comes into being, with the porosity of about 8.7%. The research results provide theoretical reference for coarse-grained glutenite reservoir prediction.

Controls on anomalously high porosity/permeability of Middle Jurassic deeply buried tight sandstones in the Taibei Sag, Turpan-Hami Basin, northwestern China: Implications for reservoir quality prediction

The lower member of the Middle Jurassic Xishanyao Formation (J2x1+2) sandstones are significant exploratory targets for hydrocarbon resources in the Taibei Sag of the Turpan-Hami Basin, northwestern China. Formation of anomalously high porosity/permeability in deeply buried J2x1+2 sandstones and reservoir quality prediction were investigated using a variety of petrographic analyses. These results show that the J2x1+2 sandstones are mostly feldspathic litharenites and litharenites, which are characterized by moderate-to good sorting, silty to medium granularity, and point- to long grain contacts. The J2x1+2 sandstone has low porosity (avg 6.0%) and permeability (avg 1.12 mD), but shows anomalously high porosity/permeability at depth interval of 3850–4050 m. There is a noticeable variation in pore types and sizes from intergranular-intragranular dissolution pores with a size mode of 2.0 μm in anomalously high porosity (AHP) sandstones, to major intragranular dissolution pores with a size mode of 0.5 μm in normally high porosity (NHP) sandstones, to most micropores with a size mode of 0.25 μm occurred in the normally low porosity (NLP) sandstones. The compaction is the main cause of porosity destruction, resulting in an average porosity loss of 89.6%. However, the authigenic minerals have relatively little influence on reservoir quality. The combination of nappe tectonics and well-sorted particles alleviated the compaction and thus preserved more intergranular pores in the AHP sandstones. Dissolution further increases the porosity and eventually forms the AHP sandstones. The strong carbonate-cemented facies (SCC), tightly compacted facies (TC), moderately compacted with moderate dissolution facies (MCMD), and weakly compacted with strong dissolution facies (WCSD) are determined in the J2x1+2 sandstones. The sandstones with SCC and TC are recognized as the NLP reservoirs. The MCMD and WCSD correspond to the NHP and AHP reservoirs, respectively. The reservoir quality predicted using the constructed diagenetic facies charts is in good agreement with the photomicrograph observations and physical property tests. Additionally, the AHP reservoirs are still developed in the deeply buried sandstones with depths larger than 4000 m.

How petrophysical properties influence the seismic signature of carbonate fault damage zone: Insights from forward-seismic modelling

Seismic imaging is the most common tool to detect subsurface structures in continental and marine settings. Despite technological advancement, seismic analysis of carbonates is still challenging because they are strongly influenced by petrophysical heterogeneities, being this even more difficult when further heterogeneities are added by the presence of faults. In this work, unmigrated forward-seismic models are developed to understand the seismic response changes related to carbonate-bearing fault systems and their deformation behaviour. We focus on the carbonate ramp of the Majella Massif (central Italy), that is characterised by the presence of porous and faulted carbonate lithologies. This carbonate system represents an analogue of carbonate reservoirs worldwide. Field and laboratory data of fault rocks sampled at increasing distances from the slip planes highlight a damage zone/fault core architecture with a decreasing porosity approaching fault planes. This observation is also confirmed by the thin sections analysis and the calculation of the shear modulus. Seismic images of fault rocks presenting lower porosity than the host rock show weak diffraction hyperbolas while diffraction hyperbolas are more evident in the forward-seismic models of fault rocks with greater porosity than the host rock. Moreover, factors such as the variation in the dip angle of the fault or the thickness of the damage zone can enhance or reduce the hyperbolas. Performing the migration process to stacked sections would not provide evidence of increased porosity in the damage zone due to the suppression of the diffractive component. The presence of weak hyperbolas in unmigrated seismic images is thus interpreted as evidence of a lower porosity damage zone with respect to the host rock. This can be related to deformation mechanisms leading to porosity loss in the damage zone for porous rocks as observed in the study area. However, this could also be related to the confining stress or fracture filling that counteract the fracture-related porosity increase when faults are hosted by tight rocks.

Chemistry of zipping reactions in mesoporous carbon consisting of minimally stacked graphene layers.

The structural evolution of highly mesoporous templated carbons is examined from temperatures of 1173 to 2873 K to elucidate the optimal conditions for facilitating graphene-zipping reactions whilst minimizing graphene stacking processes. Mesoporous carbons comprising a few-layer graphene wall display excellent thermal stability up to 2073 K coupled with a nanoporous structure and three-dimensional framework. Nevertheless, advanced temperature-programmed desorption (TPD), X-ray diffraction, and Raman spectroscopy show graphene-zipping reactions occur at temperatures between 1173 and 1873 K. TPD analysis estimates zipping reactions lead to a 1100 fold increase in the average graphene-domain, affording the structure a superior chemical stability, electrochemical stability, and electrical conductivity, while increasing the bulk modulus of the framework. At above 2073 K, the carbon framework shows a loss of porosity due to the development of graphene-stacking structures. Thus, a temperature range between 1873 and 2073 K is preferable to balance the developed graphene domain size and high porosity. Utilizing a neutron pair distribution function and soft X-ray emission spectra, we prove that these highly mesoporous carbons already consist of a well-developed sp2-carbon network, and the property evolution is governed by the changes in the edge sites and stacked structures.

Optimization of friction stir welding process parameters using MCDM method

Friction Stir Welding (FSW) is categorized into a solid-state welding process which is preferred to join aluminum-based materials effectively. Generally, aluminum-based materials are welded using solid state welding than fusion-based welding due to the chance of hot cracking, loss of elements and porosity. Process parameters and its selection in FSW process are important and it leads to efficient of weld quality. Taguchi concept is a standard optimization procedure but it has a limitation of not capable to solve multi objective problems simultaneously. Multi Criteria Decision Making (MCDM) method can be used for solving multiple objectives simultaneous effectively. Al-6061 T6 alloy is used as workpiece and carbon steel, H13 tool steel and high carbon high chromium steel is used as tool materials. The important process parameters considered are rotational speed of tool and welding speed. Response parameters selected are tensile strength and microhardness of welded joints. Process parameters are optimized using MCDM method and the optimum values obtained are rotational speed of 700 rpm and welding speed of 35 mm/min. It is understood that better tensile strength and microhardness of FSW joints at optimized condition due to adequate material flow, fine grain size and pulsating action. MCDM method has simple calculation procedure and easier solving methodology for machining parameters optimization.

The effect of fault-induced compaction on petrophysical properties of deformation bands in poorly lithified sandstones

Although it is well documented that during faulting there is an overall fault zone porosity loss in porous sandstone, little is known about the effect of shear-induced compaction on subsequent deformation bands petrophysics. We studied the impact of fault-induced compaction on deformation band's petrophysical properties developed in poorly lithified sandstones of the Rio do Peixe Basin, Brazil. We compared undeformed sandstone and deformation bands associated with syn-rift normal faults and post-rift strike-slip faults by integrating structural, petrophysical, mineralogical and uniaxial compressive strength (UCS) measurements. The sealing behavior was interpreted from capillary pressure obtained from mercury injection porosimetry and in situ air permeability. Host rock consists of poorly lithified sandstone with 25–30% porosity, permeability of 1.3 Darcy, capillary pressure of 5 psi, and UCS of 20 MPa. The normal faults developed from soft-sediment conditions with moderate to intense cataclasis, and resulted in an overall fault zone compaction (deformation bands and zones between deformation bands) with localized porosity and permeability loss in deformation bands (10% and 12 mD) and rock volumes between deformation bands (20% and 0.7 Darcy). Compared to syn-rift deformation bands, the strike-slip deformation bands show similar porosity (12–13%), but lower permeability (1–10 mD) and greater capillary pressures (up to 114 psi). XRD analysis on clay minerals indicates that both syn-rift and post-rift faults formed under similar shallow burial depths (<1–2 km). Therefore, we propose a model that quantifies fault-induced compaction and may predict fault sealing in structurally complex, deformation bands-dominated sandstone reservoirs affected by multiple tectonic stages.