Petrography, diagenesis and reservoir characteristics of the Pre-Cenomanian sandstone, Sheikh Attia area, East Central Sinai, Egypt

Deeply buried Lower Cretaceous Bashijiqike sandstones are important gas exploration targets in the Kelasu thrust belt, Kuqa Depression of Tarim Basin in China. The sandstones are characterized by low porosity, low permeability and strong microscopic heterogeneity due to diagenesis during their geologic history. Mineralogical, petrographic, and geochemical analyses combined with high-pressure mercury injection analysis have been used to investigate the diagenesis, diagenetic minerals, and their impact on reservoir quality. This article addresses the controls exerted by depositional parameters and diagenetic modifications on pore-network characteristics (porosity, pore types, sizes, shapes, and distribution), with the aim to unravel the formation mechanisms of this complex pore structures, and to improve the characterization and classification evaluation for the Bashijiqike sandstone reservoirs. The Bashijiqike sandstones are dominated by lithic arkoses and feldspathic litharenite. The pore system consists of intergranular macropores, intergranular micropores, and intragranular pores. Framework grains are generally heavily compacted. Authigenic quartz, authigenic feldspar, clay minerals and carbonates are the major pore-filling constituents. The pore structure is characterized by small pore radius and poor interconnectivity. Entry pressure reflects the microscopic pore network and macroscopic reservoir property characteristics. Pore structure characteristics are linked to the depositional parameters, type and degree of diagenesis. Clays do not control reservoir pore networks alone, and pores and pore throats are wider in coarser grained sandstones. Entry pressure decreases with the content of the rigid quartz. Compaction and cementation continue to decrease the pore-throat size, while dissolution enlarges pores and pore-throats radius. Considerable amounts of microporosity associated with clay minerals and altered grains contribute to the high entry pressure. Comprehensive Coefficient of Diagenesis (CCD), which considers the integrative effect of diagenesis, shows strong statistical correlations with entry pressure. CCD is an integrative modulus of diagenesis and physical property, and generally the higher the values are, the better the pore structure. It is suitable for quantitatively characterizing pore structure in tight gas sandstones. The results of this work can help assess pore-network characteristics like the Bashijiqike sandstones which had experienced strong diagenetic modifications during their geological history.

show abstract

“…Where RQI is reservoir quality index (μm); K is the permeability (mD), φ is the porosity (Lai et al, 2013a;Kass et al, 2014).…”

Section: Pore Structure Of the Bashijiqike Formationmentioning

confidence: 99%

Depositional and Diagenetic Controls on Pore Structure of Tight Gas Sandstone Reservoirs: Evidence from Lower Cretaceous Bashijiqike Formation in Kelasu Thrust Belts, Kuqa Depression in Tarim Basin of West China

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The source of studied microtektites is attributed to the melting of a sandstone rich in clay and organic matter. Siliciclastic rocks of the Paleozoic period in west central Sinai typified the characteristics of such target rock [28] [35] [36]. The high content of FeO in the glass microspherules may be explained by admixture with projectile matter [37].…”

Section: Discussionmentioning

confidence: 99%

“…Abundance of detrital grains and cement overgrowth of iron and silica in the sandstone points to a diagenetic history. The source of iron oxide mainly attributes to intra-stratal change of iron bearing detrital silicates after deposition [28]. The topmost part of the white sandstone section, quartzite beds, consists of coarse grained, closely packed and recrystallized quartz grains.…”

Section: Microscopic Observationsmentioning

confidence: 99%

Microspherules-Bearing White Sandstone: Implication of Cosmic Impact Event near Jurassic-Cretaceous Boundary in West Central Sinai, Egypt

Badawy¹,

Zayed²,

Shahien³

2016

GEP

View full text Add to dashboard Cite

The presence of glass microspherules enclosing relict grains, shattered quartz and silicon carbide in white sandstone beds near the Jurassic-Cretaceous boundary in west central Sinai indicates a cosmic impact event. Characterization of the impact microspherules and proposing a reasonable scenario for their origin are the aims of this work. Field observations, optical, binocular, scanning electron and high-resolution transmitted electron microscopy investigations and chemical analyses were carried out. The study revealed that glass microspherules have high Al2O3 and FeO contents and low CaO and MgO contents. The high content of Al2O3 indicates that the source of microtektite-like microspherules is attributed to the melting of a clay-rich sandstone and carbonaceous matter, while the high content of FeO indicates admixing with projectile matter. The reaction between silica and carbon was carried out under conditions of high temperature (T > 1000˚C) and carbon (C/Si > 1) which resulted in the production of silicon carbide with microdiamond intergrowth. Consequently, this intergrowth is in accordance with the impact origin via rapid condensation and growth within a vapor phase. In spite of the fact that no source crater has been recognized to date in the study area, the authors propose at least a single cosmic impact event scenario for the recorded glass microspherules in west central Sinai. The impact excavated the Paleozoic siliciclastic sedimentary rocks and then the glass microspherules showered the area of study. The deposition of microtektite-like glass particles within the white sandstone beds of the Malha Formation took place in the fluvial plain terrestrial environment. This setting precluded severe post-depositional reworking, yielding preservation of the glass particles in a primary layer. Eventually, lateral migration of the braided channels led to the reworking of the microspherules layer and the spatial dispersal of the shattered quartz. H. S. Badawy et al.54

show abstract

“…3f), feldspar and lithic grains. Late diagenetic stage dissolution is indicated by dissolution of authigenic calcite cements [9] . In the present study a few detrital grains of quartz, feldspar and biotite were found to be partially or completely altered.…”

Section: Dissolution and Alterationmentioning

confidence: 99%

Diagenesis of Sandstones in a Part of the Tichna Structure of Tripura Fold Belt, India

2017

IJCRR

View full text Add to dashboard Cite

Aim:The aim of the present research work is to study the petrography and diagenesis of the sandstones in a part of the Surma Group of the Tichna field located in the western part of the Tripura Fold Belt. Methodology:The standard petrographic microscope and Scanning Electron Microscope (SEM) were used for studying the rock thin sections and in identifying the various diagenetic imprints in the sandstones. Result:The study reveals that the samples are fine to medium grained, sub-angular to sub-rounded, mostly moderately sorted to well sorted and belong to sublithic-arenite, lithic arenite to feldspathic-arenite varieties. Quartz is the dominant mineral in all the samples followed by rock fragments and feldspar. Authigenic clay minerals observed are Illite, Chlorite, Kaolinite and mixed clay types. Important diagenetic changes include compaction, cementation and dissolution of detrital grains.Discussion: Compaction of the framework grains lead to the development of different type of grain contacts, bending of flexible mica flakes and fracturing of detrital grains. Quartz cementation is observed by the development of euhedral secondary overgrowths of quartz. Authigenic clay minerals either form coating over the detrital grains or occupies the intergranular pores. At restricted depth intervals, calcite cement completely fills the pore spaces. The study shows several detrital grains including quartz, feldspar and lithic grains undergoing dissolution and subsequent replacement either partially or fully. Conclusion:The analysed sandstones are mostly composed of quartz, rock fragments and feldspar. Compaction effects indicated by bending of mica flakes, grain fracturing, pressure solution and quartz overgrowth; clay authigenesis, cement precipitation, partial dissolution and replacement are the diagenetic signatures observed from thin section and Scanning Electron Microscope analyses.

show abstract

Petrography, diagenesis and reservoir characteristics of the Pre-Cenomanian sandstone, Sheikh Attia area, East Central Sinai, Egypt

Cited by 32 publications

References 21 publications

Depositional and Diagenetic Controls on Pore Structure of Tight Gas Sandstone Reservoirs: Evidence from Lower Cretaceous Bashijiqike Formation in Kelasu Thrust Belts, Kuqa Depression in Tarim Basin of West China

Depositional and Diagenetic Controls on Pore Structure of Tight Gas Sandstone Reservoirs: Evidence from Lower Cretaceous Bashijiqike Formation in Kelasu Thrust Belts, Kuqa Depression in Tarim Basin of West China

Microspherules-Bearing White Sandstone: Implication of Cosmic Impact Event near Jurassic-Cretaceous Boundary in West Central Sinai, Egypt

Diagenesis of Sandstones in a Part of the Tichna Structure of Tripura Fold Belt, India

Contact Info

Product

Resources

About