Synthesis of Mesoporous Material from Chrysotile-Derived Silica

Mesoporous MCM-41-type molecular sieves were synthesized using calcined and leached chrysotile and cetyltrimethylammonium bromide as the silica source and structure directing agent, respectively. Powder X-ray diffraction (XRD), N2 isothermal adsorption-desorption, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the samples. The calcined and leached chrysotile can be employed as an inexpensive silica source for the formation of low-order MCM-41 mesoporous materials.

Origin of Quartz Cement in the Paleogene Sandstone Reservoir of Shahejie Formation,Bohai Bay Basin,China

The precipitation of authigenic quartz plays a significant role to reduce the reservoir characteristics and enhance the stiffness of the rock.The Es_(1) sandstone of Shahejie Formation is acting as a significant hydrocarbon producing rock in the Nanpu Sag.Various methods like thin section petrography,cathodoluminescence(CL),scanning electron microscope(SEM,with EDS),and electron microprobe analysis has been used to reveal the origin of quartz cement as well as to evaluate the effect of quartz cement on reservoir quality.The studied sandstone is classified as immature to mature feldspathic litharenite and lithic arkose and consists of quartz,feldspar,rock fragments and micas.Petrographic studies and SEM analysis shows that the authigenic quartz is acting a significant cement that reduces the reservoir quality.Whereas clay minerals(kaolinite and mixed layer illite to smectite)are dominant in the Es_(1) sandstone,that can reduce the reservoir quality.SEM,CL and thin section analysis reveal that there are two stages of quartz cement in the studied samples;that are pore filling authigenic cement and quartz overgrowth cement.Fluid inclusion homogenization temperatures shows that stages of quartz cement were developed with continuous process from 70℃ to 130℃.Quartz cements were generally originated from I/S reaction,feldspar dissolution,conversion of rock fragments and pressure solution.Feldspar dissolution(K-feldspar)and kaolinite to illite reaction is an insignificant silica source for the silica cement which is internally precipitated in a close system with diffusion transporting mechanism.Overall,quartz cement significantly enhance the rock strengthen and brittleness effectively as well as it reduce the overall reservoir quality.

Geochemical characteristics and geological significance of chert nodules in Qixia formation,Pingding Mountain, lower Yangtze Plate

The Permian is an important period for the deposition of siliceous rocks on a global scale,but the genesis of chert is still controversial.To better understand the mechanism of chert nodules deposition from Qixia Formation(P1q)(Lower Yangtze Plate,China),we analyzed the major,trace and rare earth elements of these chert nodule samples(CN)and surrounding rock samples(SR)using Inductively Coupled Plasma Mass Spectrometry(ICPMS)and X-ray fluorescence(XRF)technique.The redox state,siliceous sources and depositional environment analysis show that CN have higher contents of SiO2,Fe2O3 and MnO comparing with SR,and their geochemical properties are different.Trace and rare earth elements characteristics reveal that nodules were deposited under the action of biochemistry in the basin,no terrigenous materials contamination was observed and the contribution of upwelling was emphasized.The Al/(Al+Fe+Mn),Fe/Ti and Al-Fe-Mn discrimination diagram indicated the chert nodules are influenced by hydrothermal action.Evidence from redox-sensitive elements such as Th,U,V and Sc suggests that nodules were deposited in a reducing environment.In the convective mixing of hydrothermal action and normal seawater,excessive dissolved silicon and nutrients are absorbed and precipitated by biological action,and then transported by upwelling to shallow water for deposition.All the evidence comes from the trace elements enrichment characters,Rare earth elements and Y(REY)distribution patterns and La/La^(*),Ce/Ce^(*),Eu/Eu^(*),LREE/HREE,Y/Ho and∑REE characteristics.

Quartz types,genesis and their geological significance within the Wufeng-Longmaxi Formation in north-western Hunan,China

Quartz is an important mineral component in the Late Ordovician–Early Silurian Wufeng-Longmaxi Formation with various forms and sources and has a significant impact on the properties of shale gas reservoirs.In this study,geochemical analysis,scanning electron microscopy(SEM)observation,and rock mechanics testing were performed on shale samples from the Wufeng-Longmaxi Formation in north-western Hunan,South China.Quartz is classified into four types based on morphological features and cathodoluminescence(CL)images under SEM–terrigenous detrital quartz,quartz overgrowths,biogenic skeletal quartz and microquartz.The quartz in Upper Longmaxi Formation is predominantly of terrigenous origin and contains a small amount of quartz formed by clay transformation.The quartz in the Wufeng-Lower Longmaxi Formation is predominantly biogenic.The biogenic quartz has a direct effect on organic matter(OM)abundance,pore structure and brittleness.It is indicated by the positive correlation with TOC content and biogenic Ba content that biogenic quartz-rich strata have high paleoproductivity.The rigid frameworks formed by biogenic quartz during the early diagenesis stage facilitated the preservation of the primary pores.The interparticle pores of biogenic quartz are the space for OM preservation and migration,creating conditions for the development of OM pores.Additionally,the calculated brittleness index(BI)shows a positive correlation with biogenic quartz content,indicating that layers rich in biogenic quartz are more conducive to fracture.Therefore,the Wufeng-Lower Longmaxi Formation has higher OM content,porosity and represents a more favorable exploration and development target.