Alkaline Fluids Research Articles

Chronology and geofluids characteristics of calcite cement in the Upper Triassic Xujiahe Formation tight sandstone reservoir, Western Sichuan Basin, SW China

Geological fluid activities significantly influence diagenesis and hydrocarbon accumulations in reservoir rocks. However, it remains challenging to precisely determine the timing of these activities. This study aims to investigate the chronology and geofluids characteristics of calcite cement that leads to reservoir tightness in the Upper Triassic Xujiahe Formation in the Western Sichuan Foreland Basin, which is a critical exploration target for hydrocarbon resources. We examine calcite cement as a marker of fluid activities, employing petrological analyses, U-Pb dating, and in-situ carbon-oxygen isotope analysis. These methods are integrated with simulations of regional burial and thermal histories to assess pore evolution and hydrocarbon accumulation mechanisms in these tight sandstone reservoirs. Results reveal two main calcite cementation stages within the second member of the Xujiahe Formation (Xu-2 Member): early cements from the Middle Jurassic around 175 ± 11 Ma and late cements from the Late Jurassic between 161 and 156 Ma. Initially, basin-derived alkaline fluids and near-surface atmospheric freshwater supplied the calcium and carbon for early cements during ongoing basin subsidence. Calcium and carbon for the late calcite cements came from the dissolution of carbonate rock fragments by organic acids. The heavier δ13C is primarily associated with in-situ generation and consumption of carbon within the system, while the δ18Ofluid, which is close to modern seawater values, is mainly related to active water-rock reactions induced by processes such as the dissolution of carbonate rock fragments by organic acids. The closed diagenetic system due to calcite cementation in the Late Jurassic led to reservoir tightening. Therefore, basin-scale chronological constraints on calcite cement are of great significance for quantitatively studying sandstone reservoir densification and exploring the mechanism and control factors of hydrocarbon accumulation.

Enhanced pozzolanic reactivity in hydrogen-form zeolites as supplementary cementitious materials

Pozzolans rich in silica and alumina react with lime to form cementing compounds and are incorporated into portland cement as supplementary cementitious materials (SCMs). However, pozzolanic reactions progress slower than portland cement hydration, limiting their use in modern construction due to insufficient early-age strength. Hence, alternative SCMs that enable faster pozzolanic reactions are necessary including synthetic zeolites, which have high surface areas and compositional purity that indicate the possibility of rapid pozzolanic reactivity. Synthetic zeolites with varying cation composition (Na-zeolite, H-zeolite), SiO2/Al2O3 ratio, and framework type were evaluated for pozzolanic reactivity via Ca(OH)2 consumption using ion exchange and in-situ X-ray diffraction experiments. Na-zeolites exhibited limited exchange reactions with KOH and Ca(OH)2 due to the occupancy of acid sites by Na+ and hydroxyl groups. Meanwhile, H-zeolites readily adsorbed K+ and Ca2+ from a hydroxide solution by exchanging cations with H+ at Brønsted acid sites or cation adsorption at vacant acid sites. By adsorbing cations, the H-zeolite reduced the pH and increased Ca2+ solubility to promote pozzolanic reactions in a system where Ca(OH)2 dissolution/diffusion was a rate limiting factor. High H-zeolite reactivity resulted in 0.8 g of Ca(OH)2 consumed per 1 g of zeolites after 16 h of reaction versus 0.4 g of Ca(OH)2 consumed per 1 g of Na-zeolite. The H-zeolite modulated the pore fluid alkalinity and created a low-density amorphous silicate phase via mechanisms analogous to two-step C-S-H nucleation experiments. Controlling these reaction mechanisms is key to developing next generation pozzolanic cementitious systems with comparable hydration rates to portland cement.

Magmatic degassing and fluid metasomatism promote compositional variation from I-type to peralkaline A-type granite in the late Cretaceous Fuzhou felsic complex, SE China

Abstract A-type granites generally have much lower water, higher temperature, and incompatible element concentrations than I-type granitoids. Yet it remains unclear why I-A-type granitic complexes occur in convergent plate margins. Here we conduct geochemical analyses on apatite and mafic minerals from the late Cretaceous I-A-type granitic complex in Fuzhou area, SE China, aiming to decipher differentiation, fluid metasomatism, and degassing that primarily control the compositional diversity of felsic magmas. Apatites in both rock types are F-rich and show large H2O and δD variations, i.e., 341–3892 ppm H2O and –325 to +336‰ δD in I-type granitoids; 67–1366 ppm H2O and –251 to +1439‰ δD in A-type granites. H2O in apatite is negatively correlated with La/Sm and Sr/Y in the I-type granitoids, whereas it is positively correlated with Ce and total rare earth element (REE) concentrations in the A-type granites. Once H2O increases up to hundreds of ppm, both rock types show a rapid decrease of H2O/Ce, an increase of F/Cl, and extensive H isotope fractionation. Arfvedsonite occurs as a late crystallizing mineral in the A-type granite and has much higher contents of Na2O, K2O, F, and high field strength elements (HFSE) than hornblende in the I-type granitoids, indicating the addition of F-HFSE-rich alkaline fluids during its magmatic evolution. The consumption of arfvedsonite and formation of aegirine further indicate the role of fluid metasomatism and H2 degassing via a reaction of 3Na3Fe5Si8O22(OH)2 + 2H2O = 9NaFeSi2O6 + 2Fe3O4 + 6SiO2+5H2. The combined geochemical data demonstrate that the systematic differences in mineral assemblage, whole-rock composition, magma temperature, H2O content, and δD of apatite between the I- and A-type granites are likely attributed to varying degrees of differentiation, fluid metasomatism and magmatic degassing. The I-type granitoids experienced hornblende, biotite, plagioclase, K-feldspar, and apatite fractionation and close-system degassing. The A-type granite was likely formed from the I-type monzogranitic magma that was metasomatized by the mantle-derived F-HFSE-rich alkaline fluids to produce the peralkaline magma, which further experienced K-feldspar + plagioclase + biotite + apatite fractionation and open-system degassing. Further numerical estimation indicates that the primary magma of Fuzhou granitic complex contained ~3.0 wt% H2O, and the lower water content of A-type granite was likely attributed to strong degassing during its emplacement. Our results indicate that some peralkaline A-type granites can be generated from relatively water-poor I-type granitic magmas by fluid metasomatism and degassing.

Research on quantitative analysis method of shale oil reservoir sensitivity based on mineral analysis

Mineral compositions of shale reservoirs are complex and highly influenced by external fluids. At present, there are limited studies on the effect of mineral expansion rate on external fluids, and there is a lack of systematic research on the sensitivity of shale reservoir porosity to external fluids. In this paper, firstly, X-Ray Diffractometer (XRD) experiments were carried out to study the mineral composition of shale reservoirs, revealing the mechanism of shale minerals interacting with acidic/alkaline fluids. Secondly, the sensitivity evaluation experiments of single mineral external fluid immersion were conducted on the main minerals in shale. Finally, a prediction method for the sensitivity of shale reservoir porosity to external fluids (acidic/alkaline fluids, oil slicks) was established. The results show that: (a) Volume expansion of quartz after 48 h of immersion in alkaline fluids at pH = 9 and pH = 11 and the expansion rate is maximum at pH = 9 i.e. 0.16. (b) Volume expansion of chlorite after 48 h immersion in alkaline fluid and maximum expansion at pH = 13 i.e. 0.55. (c) The improvement of total porosity of shale by acid solution is weak. (e) Alkaline solution has a weak damage to the total porosity of shale, and the degree of damage increases and then decreases with the increase of the strength of alkaline solution.

Metasomatism of mafic-intermediate rocks in the Motloutse Complex, Botswana: Effect on ore mineralization and implication for the Paleoproterozoic Large Alkali Metasomatic Province (LAMP) in southern Africa

Alkali metasomatism is a common overprint in Archean medium- to high-grade metamorphic terranes. Since mafic-intermediate rocks are able to host ore mineralization, it is important to understand the effect of metasomatism on its distribution. This study presents field, petrographic, mineralogical, geochemical, and U-Pb/40Ar-39Ar geochronologic characteristics of metasomatized amphibolite, amphibole gneiss and gabbro along a regional E-W section of the southeastern Motloutse Complex in eastern Botswana. The progressive metasomatism accompanies shear deformation and is visually manifested by varying degrees of pinkish discoloration of the host rocks. The metasomatic reactions in amphibolite, amphibole gneiss and gabbro are manifested in replacement of amphibole, clinopyroxene, ilmenite and plagioclase by the assemblages of chlorite, epidote, titanite, magnetite, sericite, albite and K-feldspar, up to near complete albitization and K-feldspathization with few relics of earlier minerals. Mineral compositions reflect the effects of a progressive metasomatic overprint. The metasomatic overprint resulted in the break down and dispersal of primary Cu-Ni sulphides. The pseudosection modelling (PERPLE_X) in terms of lg(aK2O) and lg(aH2O) parameters for representative compositions of leucocratic and melanocratic amphibolites, amphibole gneiss and gabbro indicates that the metasomatic process involved an increase of potassium activity followed by hydration. The modelling explains variable extent of metasomatism in different rock types. Whole-rock compositional variations indicate a general enrichment in Na2O, K2O and SiO2, and depletion in FeO and MgO in rocks during the metasomatism. 40Ar/39Ar amphibole and U-Pb titanite geochronology from metasomatized amphibolite and gabbro gave comparable ages of c.2.01–1.96 Ga. Alkaline fluids producing metasomatism were likely of crustal origin and moved along the reactivated regional c.2.01–1.95 Ga shear zones at the boundaries of the Motloutse-Limpopo complexes with the adjacent Zimbabwe and Kaapvaal cratons. Implications for a Paleoproterozoic Large Alkali Metasomatic Province (LAMP) in southern Africa, and its relation to the Bushveld large igneous province (LIP) is explored.

The wear behavior and lapping performance of fixed abrasive pad for acidity and alkalinity of lapping fluid in lapping quartz glass

The wear behavior and lapping performance of fixed abrasive pad for acidity and alkalinity of lapping fluid in lapping quartz glass

Pyrochlore composition and Sm[sbnd]Nd isotope signature as indicators of magmatic-hydrothermal processes: The case of Ririwai complex, north-Central Nigeria

This study presents a geochemical and SmNd isotopic study on pyrochlore from the Ririwai alkaline complex in north-central Nigeria, aiming to reconstruct the magmatic-hydrothermal history and provide insights into the formation of niobium deposit hosted in alkaline igneous rocks. Three texturally and compositionally distinct types of pyrochlore (Pcl I, II, and III) are identified. Primary Pcl I grains are enriched in Nb2O5 (mean of 60.5 wt%) and other high field strength elements (HFSE), rare earth elements (mean of 17.2 wt% REE2O3), Ca, Na, and F, suggesting that they crystallized in a Nb-rich peralkaline magma. The occurrence of patchy zoning as well as the development of microfractures and pores within these pyrochlore grains indicate two stages of hydrothermal alteration responsible for the formation of Pcl II and Pcl III. The first stage of alteration from Pcl I to Pcl II was induced by high-temperature, alkali-rich, and F-moderate fluids, leading to the removal of Na, Ca, and F while filling the vacant A- and Y-sites with K, Rb, Y, and Zn. The Nb and REE contents in Pcl III (mean of 41.3 wt% and 9.4 wt%, respectively) are lower than those in Pcl I and Pcl II (mean of 58.1 wt% and 17.3 wt%, respectively). Thereby, the second stage of alteration from Pcl II to Pcl III was related to low-temperature, Si- and Al-rich alkaline fluids, which resulted in the leaching of Nb, Ti, Th, U, and REE (mainly LREE) from the A- and B-sites, compensated by the incorporation of Si, Pb, K, Al, Fe, and Mn. The leached elements either precipitated into Nb-bearing minerals such as rutile, thorite, and zircon in alteration assemblages as an in-situ replacement of Pcl II or remobilized locally to form hydrothermal veins of Si, Al, Nb, and CO2-bearing oxides. The comparable εNd(t) values between hydrothermal Pcl II and III (−1.9 to −2.8 and − 1.5 to −3.2, respectively) and magmatic Pcl I (−2.0 to −2.6) indicate that there was only a minimal external contribution to Nd (and by analogy Nb as well) from fluids. Two-stage hydrothermal fluids in the Ririwai alkaline complex have limited effects on Nb mobilization, without significantly enhancing or reducing the Nb grade.

Formation of Natural Magnesium Silica Hydrate (M-S-H) and Magnesium Alumina Silica Hydrate (M-A-S-H) Cement.

Occurrences of natural magnesium alumina silicate hydrate (M-(A)-S-H) cement are present in Feragen and Leka, in eastern and western Trøndelag Norway, respectively. Both occurrences are in the subarctic climate zone and form in glacial till and moraine material deposited on ultramafic rock during the Weichselian glaciation. Weathering of serpentinized peridotite dissolves brucite and results in an alkaline fluid with a relatively high pH which subsequently reacts with the felsic minerals of the till (quartz, plagioclase, K-feldspar) to form a cement consisting of an amorphous material or a mixture of nanocrystalline Mg-rich phyllosilicates, including illite. The presence of plagioclase in the till results in the enrichment of alumina in the cement, i.e., forms M-A-S-H instead of the M-S-H cement. Dissolution of quartz results in numerous etch pits and negative quartz crystals filled with M-A-S-H cement. Where the quartz dissolution is faster than the cement precipitation, a honeycomb-like texture is formed. Compositionally, the cemented till (tillite) contains more MgO and has a higher loss of ignition than the till, suggesting that the cement is formed by a MgO fluid that previously reacted with the peridotite. The M-(A)-S-H cemented till represents a new type of duricrust, coined magsilcrete. The study of natural Mg cement provides information on peridotites as a Mg source for Mg cement and as a feedstock for CO2 sequestration.

Paleoproterozoic hydrothermal overprinting over Neoarchean banded iron formation produced high-grade iron ores in the giant Gongchangling deposit of North China: Evidence from O–S–B isotopes

The Gongchangling iron deposit in North China hosts abundant high-grade (>50 wt% total Fe) magnetite ores and represents one of the largest BIF-hosted magnetite deposits worldwide. These high-grade magnetite ores are generally accepted to be formed by replacement of banded iron formation (BIF) (∼30 wt% total Fe), but the mechanism of iron enrichment remains controversial. Here we report new O–S–B isotope data of BIFs, high-grade iron ores, and related altered wall rocks, from the Gongchangling iron deposit, together with the geological and geochronological data to constrain the formation of the high-grade iron ores, and proposed new genetic model. The high-grade iron ores have positive δ56Fe and negative δ30Si values, similar to the BIFs, whereas the δ18O values of the high-grade iron ores and altered wall rocks are significantly lower than those of the BIFs. The δ34S values of pyrite from the high-grade iron ores are much higher than those of the BIFs. The δ11B values of tourmaline in the altered wall rocks of the high-grade iron ores are anomalously high, which is distinct from those of the BIFs and wall rocks, but similar to those of the evaporites from the Liaohe Group. At ca. 1.85 Ga, intense hydrothermal activity was initiated by post-orogenic extension and uplift with 18O-poor meteoric water circulated along crustal structures. Compositions of Na+, K+, Mg2+, Cl–, CO32–, 34S-rich SO42–, 11B-rich borate, and other soluble salts minerals were leached from the evaporitic rocks of the Liaohe Group, which driving the ore-forming hydrothermal fluids toward slightly alkaline and weakly oxidized as system matures. As the alkaline fluids migrated along the structures and fractures in the BIFs and reacted with the wall rocks, SiO2 was mobilized from the low-grade iron ores and consequently formed chlorite, garnet, and tremolite in the wall rocks due to reactions with clay minerals. These Si-rich hydrothermal fluids was also related to vein type quartz and massive quartz-bearing rocks. Most Fe was retained in situ and resulted in the formation of magnetite-rich iron ores. The SO42– in the hydrothermal fluids was reduced to form pyrite while B in the hydrothermal fluids reacted with the wall rocks to form 11B-rich tourmaline.

Variations of sedimentary environment under cyclical aridification and impacts on eodiagenesis of tight sandstones from the late Middle Jurassic Shaximiao Formation in Central Sichuan Basin

Understanding eodiagenesis is essential to decoding the diagenetic pathways of tight sandstones that act as excellent unconventional oil & gas reservoirs. Great paleoclimate change is capable of influencing eodiagenetic processes of tight sandstones through variations of sedimentary environment. However, it is less noted how climate gradients between the greenhouse and the hothouse conditions impact the eodiagenesis of tight sandstones. We examined eodiagenetic processes that has been operated in the Shaximiao Formation sandstones using petrographic observation, scanning electron microscopy, geochemistry, and XRD analysis to reveal impacts of the transitional climate changes on the differential eodiagenesis and implications for the diagenesis-porosity evolution. Based on sequence stratigraphy, the Shaximiao Formation is divided into four sub-members SXM1, SXM2, SXM3, and SXM4, respectively. Dark sandstones and mudstones mainly occurred in the SXM1 and the SXM2. Grey-green clastic rocks are dominant in the SXM3, whereas red mudstones frequently appear in the SXM4. Paleoclimate indices denote that a cyclical aridification from the warm-humid to hot-semiarid conditions took place from the SXM1 to the SXM4. It could have been caused by the megamonsoon effect and the paleogeographic shift along with the breakup of the Pangaea supercontinent. Combined with the migration of depocenters, the paleoclimate change resulted in transformation of sediment provenances from mafic igneous rocks to quartzose sedimentary rock along with the decreasing textural maturity. Therefore, sedimentary environments varied from the high-saline to low-saline and from low-oxygen to high-oxygen conditions respectively, which had a crucial impact on eodiagenetic cements which were formed in the Shaximiao Formation. Chlorite and laumontite cement precipitation was promoted by high-saline alkaline fluids. Chlorite proportions show an arched trend from the SXM1 to the SXM4, compatible with those of primary and secondary porosities. In contrast, laumontite proportions exhibit a decreasing variation from the SXM1 to the SXM4. High percentages of early cements are favorable to improving resistance to the compaction and preservation of primary pores. However, high chlorite (>5%) and laumontite (>10%) proportions are destructive for the reservoir quality. Large quantities of laumontite cements occupy primary pores and impede diagenetic fluids flowing and are not favorable to the dissolution. By contrast, an excess of chlorite cements can be dissolved to produce secondary pores during the organic acid release. Thus, the SXM2 is potential as a reservoir for oil & gas. Therefore, those eodiagenetic cements can control the late diagenetic evolution and the reservoir quality. Observations made here have implications for understanding tight sandstone reservoirs elsewhere in the world.

Na-Enriched Titanite in Apoquartzite Fenites From Azov Area (Ukraine)

The Na-enriched titanite (up to 3.53 % Na2O) was found in the apoquartzite fenites of the Tunikova gully (Eastern part of the Azov megablock, Ukrainian Shield). It is observed in association with alkaline amphiboles, aegirine, low-Al and high-F phlogopites, rutile, bastnaesite-(Ce), monazite-(Ce), albite, and Ba-enriched potassium feldspar. This mineral association, as well as the agpaitic specificity of apoquartzite fenites (peralkaline index >2), is the result of the influence of undiscovered intrusion of alkaline igneous rocks (silicate or carbonatite) that were the source of alkaline fluids. In general, the Na-enriched titanite contains (wt. %): Y2O3 (up to 3.48), Ce2O3 (up to 0.98), Nd2O3 (up to 1.13), increased F (up to 1.94), but moderate Nb2O5 (0.2-2.8) and negligible content of FeO and MnO, in the almost complete absence of Al2O3. It is assumed that the Na-enriched titanite substitutes the primary rutile of quartzites and reflect high concentration of Na2O, CaO, REE, Y, F introduced by alkaline fluids. The Na → Ca isomorphism was accompanied by parallel substitution Y, REE → Ca, and partially O → F. Other schemes of substitution intrinsic for titanites of alkaline rocks, such as Na+Nb → Ca+Ti or Nb+Fe(Al) → 2Ti, are practically not manifested that obviously due to the low Nb content in the primary rutile and introduced alkaline fluids, as well as the depletion of quartzite in alumina and iron.

Формы переноса РЗЭ фторидно-карбонатно-хлоридными охлаждающимися гидротермальными флюидами в присутствии барита и целестина (термодинамическое моделирование)

A thermodynamic study was carried out in order to determine the forms of transport for the entire series of lanthanides and their ratio with changing parameters of a hydrothermal fluid of moderate concentrations of chloride, carbonate and fluoride components. Hydrothermal solution, cooling from 500 to 100 ∘C, affected barite and celestine, which are used as a source of sulfate sulfur, monazite as a source of rare earth elements (REE) and phosphorus, and calcite as a source of calcium. It has been established that, under weakly acidic (pH about 4.1) conditions, the equilibrium mineral association is represented by rare earth fluorite, monazite, rare earth fluorapatite, and strontiobarite. In the high-temperature region for light and medium REE, the leading is the first chlorocomplex LnCl+2. For heavy REE, the second fluorine complex LnF+2 takes the first place, except for terbium and dysprosium, for which a sharp predominance of the sulfate complex is revealed. A special picture is observed at 100 ∘C: the leading position is occupied by Ln+3 for both light and heavy REE. In the case of a near neutral weakly alkaline fluid (pH about 7.1), the equilibrium mineral association is represented by calcite, monazite, REE-fluorite, REE-fluorapatite, strontiobarite, and strontianite. The appearance of the latter in natural associations may serve as an indication of the increased alkalinity of the ore-forming environment. In an equilibrium weakly alkaline fluid up to 200 ∘C, hydroxocomplexes are prevalent for all REEs with the ratio Ln(OH)03> Ln(OH)+2. The first chloro complex for light REE at 500–400 ∘C, and the second fluoro complex for medium and heavy REEs follow them. At 100 ∘C, the concentration of hydroxocomplexes sharply decreases, and fluorine and carbonate complexes come to the fore. In general, there is an increased stability of the first chlorocomplex in the high-temperature region, and with decreasing temperature, the role of REE fluorocomplexes increases. Two variants of acidity-alkalinity calculations presumably correspond to modeling of two types of fluids: greisenizing – weakly acidic and carbonatite-forming – weakly alkaline.

Diagenetic evolution of tight sandstone and the formation of an effective reservoir in the lower member 3 of the Shahejie Formation, Bohai Bay Basin, East China

Heterogeneity in the physical properties of tight sandstones is mainly caused by complex diagenetic interactions in various combinations during the burial process. The tight sandstone oil in the Linnan Sag of Bohai Bay Basin has great development potential but it is unclear how effective reservoirs were formed, and this is a significant reason why exploration in the deep reservoir is so difficult. Here we studied the diagenetic evolution of the tight sandstone of Lower Member 3 of the Shahejie Formation, Linnan Sag, Bohai Bay Basin, by using cores, thin sections, XRD, SEM, grain-size analysis, high-pressure mercury intrusion porosimetry, fluid inclusions, and carbon and oxygen stable isotopes. Compaction, replacement, cementation and dissolution diagenesis are identified; all four processes mainly occur in the A phase of mesodiagenesis. The interaction of formation burial, thermal evolution of organic matter and dehydration of gypsum leads to the alternating presence of three stages of alkaline fluids and two stages of acidic fluids. The average dissolution porosity of the dissolution sandstone facies is greater than the lower limit of the porosity for the effective reservoir in the study area, which is key to the formation of effective reservoirs. By determining differential diagenetic evolution sequences of tight sandstone reservoirs under the constraints of different lithologies where sandstone is interbedded with mudstone, we are able to elucidate the formation of the effective reservoir as follows: (1) In the eodiagenetic stage, a large amount of early carbonate cement developed in the sandstone adjacent to the mudstone, filling the primary pores and forming a cementation sandstone facies. Smaller amounts of early carbonate cement developed in the interior of the sandstone, which “fixed” the primary pores, and has a positive effect on the formation of a large number of secondary pores in the dissolution stage. (2) In the early stage of mesodiagenesis (A1), due to the filling of primary pores, it is difficult for acidic fluids to enter the cementation sandstone facies adjacent to mudstone, and the dissolution is weak. But dissolution within the sand body was strong, producing a large number of dissolution pores and forming a dissolution sandstone facies that clearly enhanced the physical properties. (3) In a second early stage of mesodiagenesis (A2), dissolution still played a dominant role in the dissolution sandstone facies, due to the development of dissolution pores in the previous stage (it is easy for acidic fluids to enter the dissolution sandstone facies). The physical properties of the dissolution sandstone facies were once again enhanced and an effective reservoir gradually began to form. (4) At the end of mesodiagenesis stages A1 and A2 (26.2–24.6 Ma; 7.5–2.8 Ma), the reservoir experienced two phases of petroleum charging. The charging of the cementation sandstone facies developed at the margins of the sandstones was difficult due to the filling of primary pores. The dissolution sandstone facies are oil-bearing, with higher porosity, which indicates an effective reservoir. By coupling the thermal evolution of organic matter and the dehydration of gypsum with differential diagenetic evolution and the porosity evolution of reservoir, we are able to establish a reservoir genetic model that involves alternating seepage of organic acids and alkaline brines.

Analyzing Electrochemical Sensing Fundamentals for Health Applications

AbstractHumans continuously interact with physical, chemical, and biological environments that influence their health, safety, and quality of life. Sensing devices, such as electrochemical sensors that translate environmental qualities into electrical signals, are crucial for detecting biomarker concentrations in various biofluids. However, the understanding of electrochemical sensing is often incomplete, necessitating further study of chemical reactions and sensor‐electrode interactions for healthcare applications. This review analyzes crucial topics in chemical reactions in electrochemical sensing environments. First, the dynamics of chemical energy, the roles of acidic and alkaline fluids, chemical reaction tendencies, thermodynamic equilibria, Gibbs free energy, water dissociation, and the pH scale are discussed. Sensor materials or biomarkers undergo oxidation and reduction reactions in electrochemical sensing. Oxygen‐derived radicals and nonradical reactive species significantly influence biochemical reactions, cellular responses, and clinical outcomes. Then, the review delves into the impact of oxidation reduction reactions on human pathophysiology, redox reactions in hemoglobin, redox environments in human serum albumin and cells/tissues, and thermodynamics of biological redox reactions. Finally, recent advances in electrochemical techniques are presented and research challenges and future perspectives in electrochemical sensing for health applications are addressed.

Optimization of a bio-based drilling fluid from waste Dacryodes Edulis (local pear) for oil exploration

This study focused on the development and optimization of a bio-based drilling fluid from local pear seed for oil exploration, which can help lessen the environmental impact of oil spills. Local pear seed being a biodegradable material was collected, prepared, its oil extracted, modified and optimized to obtain an eco-friendly and cost-effective drilling fluid. The selected materials used for this study was Local pear oil. The drilling fluid was characterized for proximate parameters and ultimate parameters. The prepared drilling fluid was optimized using response surface methodology (RSM) provided by Design-Expert software 13.0. Central composite design (CCD) was applied to study the variables affecting rheology of drilling fluid. The process factors which include pH (A), viscosity (B), mud density (c), temperature (D), rheology (E) interacted to produce the response (drilling fluid yield) for the studied sample. The optimized drilling fluid yield and the optimum values were obtained through iterations of one hundred (100) solutions and the best yield was selected at iteration number seven (95th solution), at a pH of 1, Viscosity of 119.783cP, mud density of 10.473kg/L, Temperature of 100°C, and Rheology of 76.809s-1, and the optimized drilling fluid yield value was 91.144%. The acidity and the alkalinity of the drilling fluid were measured by the concentration of the 9.5 ion in the fluid. Therefore, the biomaterial studied has demonstrated its optimal effectiveness and potential application as an additive for the development of drilling fluid for oil exploration.

Evolution processes and diagenetic response of paleo-pore fluids in continental rift basin: A case study of Bonan Sag

Evolution and transport processes of pore fluids are accompanying with the burial process of sedimentary basins. Those processes lead to redistribution of materials and energies, and control the distribution of favorable reservoirs in sedimentary basins too. For petroliferous basins, confirming the evolution processes of pore fluids is useful for favorable reservoirs prediction. In this study, formation waters chemistry characteristics, skeleton particle compositions, and diagenetic products of sandstones were all take into consideration. It is to invert the evolution processes of pore fluids in continental rift basin. This study shows the changes of formation waters, diagenetic products and skeleton particle compositions are regularly with depth. The evolution processes of pore fluids are mainly controlled by basin sinking and uplifting, fluids concentration, mudstones compaction, organic matter evolution, diagenesis. The evolution of pore fluids in Bonan Sag have experienced seven stage: firstly, primary lake water; and then alkaline fluids from mudstone, which is caused by compaction; and then acidic fluids with organic acids; and then the alkaline fluids, which is caused by basin uplifting and water-rock interactions; and then acidic fluids with CO2, which is from cracking of organic matters; and then acidic fluids with CO2/H2S which caused by TSR; at last, alkaline fluids caused by deep buried and water-rock interactions. Changes of pore fluids (physical or chemical) lead parts of minerals in sandstones be unstable, and then dissolved by pore fluids. At the same time, part of dissolved particles in pore fluids reacted with each other, and then precipitated as diagenetic products.

The iron oxidation state of Ryugu samples

AbstractThe Hayabusa2 mission sampled Ryugu, an asteroid that did not suffer extensive thermal metamorphism, and returned rocks to the Earth with no significant air exposure. It therefore offers a unique opportunity to study the redox state of carbonaceous Cb‐type asteroids and evaluate the overall redox state of the most primitive rocks of the solar system. An analytical framework was developed to investigate the iron mineralogy and valence state in extraterrestrial material at the micron scale by combining x‐ray diffraction, conventional Mössbauer (MS), and nuclear forward scattering (NFS) spectroscopies. An array of standard minerals was analyzed and cross‐calibrated between MS and NFS. Then, MS and NFS spectra on three Ryugu grains were collected at the bulk and the micron scales. In Ryugu samples, iron is essentially accommodated in magnetite, clay minerals (serpentine–smectite), and sulfides. Only a single set of Mössbauer parameters was necessary to account for the entire variability observed in MS and NFS spectra, at all spatial scales investigated. These parameters therefore make up a fully consistent iron mineralogical model for the Ryugu samples. As far as MS and NFS spectroscopies are concerned, Ryugu grains are overall similar to each other and share most of their mineralogical features with CI‐type chondrites. In detail however, no ferrihydrite is found in Ryugu particles even at the very sensitive scale of Mössbauer spectroscopy. The typical Fe3+/Fetot of clay minerals is much lower than typical redox ratios measured in CI chondrites (Fe3+/Fetot = 85%–90%). Furthermore, magnetite from Ryugu is stoichiometric with no significant maghemite component, whereas up to 12% of maghemite was previously identified in the Orgueil's so‐called magnetite. These differences suggest that most CI meteorites suffered terrestrial alteration and that the preterrestrial composition of these carbon‐rich samples was less oxidized than previously measured. However, it is not clear yet whether or not the parent bodies of CI chondrites were as reduced as Ryugu. Finally, the high spatial resolution of NFS allows to disentangle the redox state and the crystal chemistry of iron accommodated in serpentine and smectite. The most likely polytype of serpentine is lizardite, containing <35% of Fe3+, a fraction of which being tetrahedrally coordinated. Smectite is more oxidized (Fe3+/Fetot > 65%) and mainly contains octahedral ferric iron. This finding implies that these clays formed from highly alkaline fluids and the spatial variability highlighted here may suggest a temporal evolution or a spatial variability of the nature of this fluid.

Study on pore structure and permeability sensitivity of tight oil reservoirs

The tight oil reservoir is rich in microscale pores, which has a significant impact on oil and water distribution and seepage. In this paper, first, the microscale pore-throat structure characteristics of tight oil reservoir is analyzed, and the injection medium sensitivity characteristics of the pore-throat structure is explored. Second, considering the dynamic evolution characteristics of permeability, the injection medium influence mode of permeability in tight reservoirs is elucidate. Results show that: (a). The average porosity ratio of microscale pores and small pores (64.35 %) is higher than that of mesoscale pores and large pores (35.65 %), indicating that there are more microscale pores and small pores developed in the reservoir. (b). The mineral content of reservoir rock is 23.93 % quartz, 8.48 % potassium feldspar, 27.28 % plagioclase, 17.63 % calcite, 5.65 % dolomite and 17.03 % clay mineral. (c). Acidic fluids have a weak improvement effect on the porosity of tight sandstone. The average total porosity change rate after interaction with 3 % HF is 8.06 %. (d). Acidic fluids have weak improvement on reservoir pore structure and strong improvement on reservoir permeability. Alkaline fluids have a strong improvement effect on reservoir fluids, but have a moderate to weak improvement effect on reservoir permeability.

EFFECT OF VARIOUS SUSTAINED RELEASE POLYMERS ON FLOATING TABLETS OF CARVEDILOL PHOSPHATE-A COMPARATIVE STUDY

Objective: This study aimed to develop floating tablets of Carvedilol phosphate containing various excipients such as HPMC K100M, Carbopol, Polyox WSR, HPMC K4M, and sodium bicarbonate to generate gas. Additionally, the impact of DCP, spray dried lactose, and HPβCD on drug release was investigated. Methods: A total of eighteen formulations were prepared using the direct compression method and evaluated for hardness, drug content, friability, floating lag time, floatation time and drug release properties. Results: FTIR analysis confirmed that there were no chemical interactions between Carvedilol phosphate and the excipients used in the formulation of the floating tablets. Most of the Carvedilol phosphate floating tablets, except for F9 and F10, did not disintegrate in water, alkaline fluids (pH 7.4), or acidic aqueous solutions (pH 1.2). These tablets exhibited satisfactory quality attributes in terms of hardness, drug content, and friability, making them suitable for sustained release. The floating lag time of the tablets ranged from 25 seconds to 34 min, while the floating duration varied from 2 to 24 h. The drug release from the tablets was gradual and sustained over 12 h, depending on the composition of the tablets. Polyox WSR (F9 and F10) resulted in a rapid drug release, whereas an increase in the polymer concentration led to a decrease in the rate of drug release across all formulations. Conclusion: The study reveals that the use of hydrophilic polymers enhanced the drug release, whereas hydrophobic polymers decreased the drug release. As such, formulations, F11, F15, and F16, which gave 100% drug release within 12 h are finalized as the optimized formulations of Carvedilol phosphate floating tablet.

Experimental and modelling study of the interaction of bentonite with alkaline water

Compacted bentonite is planned to be used as buffer and backfill materials for the containment of radioactive waste in underground repositories. The performance of these barriers depends on the swelling capacity of bentonite upon hydration. Prolonged interaction between bentonite and alkaline fluids from neighbouring concrete structures can impair the swelling capacity due to profound changes in the chemical composition of bentonite. The coupled hydro-chemo-mechanical behaviour of bentonite under such conditions is at present not well understood. This paper presents for the first time a combined experimental and modelling study that addresses this coupled behaviour with the aim of understanding the key mechanisms leading to swelling pressure loss. Two experiments are presented in which compacted Wyoming bentonite was saturated with either clay or cementitious water, leading to different initial swelling capacities. The samples were subsequently subject to a flow of a KOH-rich cementitious water leading to a slow but sustained decrease in swelling pressure in both tests. The main novelty is the application of a recently developed hydro-chemo-mechanical model for bentonite for interpretation of the experiments. The model accounts for the impact of montmorillonite dissolution, cation exchange reactions, and changes in salinity on the swelling capacity of bentonite. The model results show a relatively good agreement with experimental measurements and suggest that the decrease in swelling capacity of bentonite is driven primarily by an increase in potassium fraction in the interlayer water and by montmorillonite dissolution.