scholarly journals Petrofacies investigations of the Cretaceous Pab Formation Rakhi Gorge Eastern Sulaiman Range Pakistan - Implication for reservoir potential

2021 ◽  
Vol 72 ◽  
pp. 37-46
Author(s):  
Mubashir Mehmood ◽  
◽  
Shahid Ghazi ◽  
Abbas Ali Naseem ◽  
Muhammad Yaseen ◽  
...  
Keyword(s):  
Total Porosity ◽  
Secondary Porosity ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Medium Reservoir ◽  
Primary Composition ◽  
Diagenetic Minerals ◽  
Reservoir Potential ◽  
Petrographic Study ◽  
Good Medium

Petrologic investigations of the sixty representative thin sections from the Pab Formation within Rakhi Gorge section Eastern Sulaiman Range Pakistan have been used to characterize different diagenetic patterns, identification of primary composition and reservoir characters. Sublithic, lithic and quartzose sandstones have been the principal constituents of the formation. The processes responsible for the late-stage alteration and diagenetic processes identified during the petrographic study include compaction of lithic fragments and mud clasts, formation of quartz overgrowth structures, feldspar replacement and alteration, cementation, and replacement of grains by clay minerals other ferrous elements and diagenetic minerals. The study shows that the initial porosity has been primary intergranular, but the secondary porosity has been originated in the rocks as a result of the alteration of the primary and secondary constituents, as well as fracturing. These facies characters replicate the reservoir quality including, good, medium, low-quality, and non-reservoir. Samples displaying average total porosity greater than 10 % have been declared as good quality. While rocks samples having 7 % or greater porosity are grouped as a medium reservoir. Those samples consisting of porosity values between 1 and 4% are considered as a low quality reservoir while those samples having porosity ranges low than 1% have been called non-reservoir. Based on the investigated parameters the studied samples from the Pab Formation displayed the characters of a medium reservoir that may hold significant hydrocarbon. This different quality including good and low quality zonation can be attributed to the facies and diagenetic change in the formation.

scholarly journals Integrated Porosity Classification and Quantification Scheme for Enhanced Carbonate Reservoir Quality: Implications from the Miocene Malaysian Carbonates

2021 ◽  
Vol 9 (12) ◽  
pp. 1410
Author(s):  
Hammad Tariq Janjuhah ◽  
George Kontakiotis ◽  
Abdul Wahid ◽  
Dost Muhammad Khan ◽  
Stergios D. Zarkogiannis ◽  
...  
Keyword(s):  
Total Porosity ◽  
Depositional Environments ◽  
Carbonate Reservoir ◽  
Pore System ◽  
Secondary Porosity ◽  
Rock Classification ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Wide Range ◽  
Pore Types

The pore system in carbonates is complicated because of the associated biological and chemical activity. Secondary porosity, on the other hand, is the result of chemical reactions that occur during diagenetic processes. A thorough understanding of the carbonate pore system is essential to hydrocarbon prospecting. Porosity classification schemes are currently limited to accurately forecast the petrophysical parameters of different reservoirs with various origins and depositional environments. Although rock classification offers a way to describe lithofacies, it has no impact on the application of the poro-perm correlation. An outstanding example of pore complexity (both in terms of type and origin) may be found in the Central Luconia carbonate system (Malaysia), which has been altered by diagenetic processes. Using transmitted light microscopy, 32 high-resolution pictures were collected of each thin segment for quantitative examination. An FESEM picture and a petrographic study of thin sections were used to quantify the grains, matrix, cement, and macroporosity (pore types). Microporosity was determined by subtracting macroporosity from total porosity using a point-counting technique. Moldic porosity (macroporosity) was shown to be the predominant type of porosity in thin sections, whereas microporosity seems to account for 40 to 50% of the overall porosity. Carbonates from the Miocene have been shown to possess a substantial quantity of microporosity, making hydrocarbon estimate and production much more difficult. It might lead to a higher level of uncertainty in the estimation of hydrocarbon reserves if ignored. Existing porosity classifications cannot be used to better understand the poro-perm correlation because of the wide range of geological characteristics. However, by considering pore types and pore structures, which may be separated into macro- and microporosity, the classification can be enhanced. Microporosity identification and classification investigations have become a key problem in limestone reservoirs across the globe.

scholarly journals Linking Depositional Environments and Diagenetic Processes to Porosity Evolution and destruction in the Arab Formation reservoirs, Offshore oilfields of Qatar

2020 ◽  
Author(s):  
Fadhil N. Sadooni ◽  
Hamad Al-Saad Al-Kuwari ◽  
Ahmad Sakhaee-Pour ◽  
Wael S. Matter
Keyword(s):  
Depositional Environments ◽  
Oil Reservoir ◽  
Secondary Porosity ◽  
Future Directions ◽  
Thin Sections ◽  
Intergranular Porosity ◽  
Porosity Evolution ◽  
Diagenetic Processes ◽  
Exploration And Production ◽  
The Impact

Introduction: The Jurassic Arab Formation is the main oil reservoir in Qatar. The Formation consists of a succession of limestone, dolomite, and anhydrite. Materials and methods: A multi-proxy approach has been used to study the Formation. This approach is based on core analysis, thin sections, and log data in selected wells in Qatar. Results: The reservoir has been divided into a set of distinctive petrophysical units. The Arab Formation consists of cyclic sediments of oolitic grainstone/packstone, foraminifera-bearing packstone-wackestone, lagoonal mudstone and dolomite, alternating with anhydrite. The sediments underwent a series of diagenetic processes such as leaching, micritization, cementation, dolomitization and fracturing. The impact of these diagenetic processes on the different depositional fabrics created a complex porosity system. So, in some cases there is preserved depositional porosity such as the intergranular porosity in the oolitic grainstone, but in other cases, diagenetic cementation blocked the same pores and eventually destroyed them. In other cases, diagenesis improved the texture of non-porous depositional texture such as mudstone through incipient dolomitization creating inter-crystalline porosity. Dissolution created vugs and void secondary porosity in otherwise non-porous foraminiferal wackestone and packstone. Therefore, creating a matrix of depositional fabrics versus diagenetic processes enabled the identification of different situations in which porosity was either created or destroyed. Future Directions: By correlating the collected petrographic data with logs, it will become possible to identify certain “facio-diagenetic” signatures on logs which will be very useful in both exploration and production. Studying the micro and nano-porosity will provide a better understanding of the evolution and destruction of its porosity system.

scholarly journals Petrography And Diagenetic History Of The Kometan Formation (Upper Cretaceous) In The Imbricated Zone, Iraqi Kurdistan Region

2020 ◽  
Vol 70 (1) ◽  
pp. 195-208
Author(s):  
Irfan Sh. Asaad ◽  
◽  
Sardar M. Balaky ◽  
Keyword(s):  
Upper Cretaceous ◽  
Planktonic Foraminifera ◽  
Kurdistan Region ◽  
Thin Sections ◽  
Iraqi Kurdistan ◽  
Diagenetic Processes ◽  
History Of ◽  
Diagenetic History ◽  
Petrographic Study ◽  
Late Stages

The petrography and diagenetic history of Upper Cretaceous Kometan Formation is investigated from its type locality in Kometan Village, Imbricated Zone, Kurdistan Region, Northeastern Iraq. The formation comprised 44 m of white weathered, light grey, thin to medium bedded fractured limestones with chert nodules and lenses in the upper part. The petrographic study of the formation is based on 50 thin sections and showed that the majority of limestones microfacies are carbonate mud (micrite). The skeletal grains include planktonic foraminifera, oligostegina, calcisphers, ostracods, pelecypods, larvae ammonoids and echinoderms. Non-skeletal grains include peloids only. The Kometan Formation has been subjected to several diagenetic processes such as: micritization, dolomitization, cementation, neomorphism, compaction, silicification, solution, phosphatization, glauconitization and fracturing. All these occurred during marine phreatic shallow burial stage and activated during intermediate to deep burial and uplifting in the late stages. The paragenetic history of the Kometan Formation has passed through four diagenetic environments including; marine, meteoric, burial and uplifting.

scholarly journals Depositional, diagenetic and stratigraphic aspects of Macaé Group carbonates (Albian): example from an oilfield from Campos Basin

2015 ◽  
Vol 45 (2) ◽  
pp. 243-258 ◽  
Author(s):  
Juliana Okubo ◽  
Ricardo Lykawka ◽  
Lucas Veríssimo Warren ◽  
Julia Favoreto ◽  
Dimas Dias-Brito
Keyword(s):  
Deep Water ◽  
Carbonate Rocks ◽  
Facies Analysis ◽  
Sedimentary Facies ◽  
Fair Weather ◽  
Thin Sections ◽  
Carbonate Sedimentation ◽  
Diagenetic Processes ◽  
Campos Basin ◽  
Facies Associations

<p>Carbonate rocks from the Macaé Group (Albian) represent an example of carbonate sedimentation related to the drift phase in Campos Basin. This study presents depositional features, integrating them with diagenetic and stratigraphic aspects of the Macaé Group carbonates including the upper part of the Quissamã Formation and the lower part of the Outeiro Formation. Macroscopic analyses in cores and microscopic ones in thin sections allowed the recognition of eleven sedimentary facies - nine of them corresponding to the Quissamã Formation and two of them representing the Outeiro Formation. These facies were grouped into five facies associations. Oolitic grainstones and oncolitic grainstones are interpreted to be deposited in shallow depth probably in shoals above the fair weather wave base. The interbanks between shoals were formed in less agitated waters and characterized by deposition of peloidal bioclastic packstones and wackestones representative of sedimentation in calm waters. Bioclastic packstones and oolitic packstones/wackestones represent allochthonous deposits related to the beginning of the regional drowning that occur in upper Quissamã Formation. Pithonellids wackestones and bioclastic wackestones with glauconite are related to deep water deposits, characteristics of the Outeiro Formation. Post-depositional features revealed the action of diagenetic processes as, micritization, cimentation, dissolution, compaction, dolomitization and recrystallization occurred during the eo- and mesodiagenesis phases. Vertical facies analysis suggests shallowing upward cycles stacked in a sequence progressively deeper towards the top (from the Quissamã Formation to the Outeiro Formation).</p>

scholarly journals Petrographic Study of Sedimentary Iron Ore in Shendi -Atbara Basin, River Nile State, Sudan.

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Abubaker A. M. A. Abasher ◽  
Sadam H.M.A. Eltayib ◽  
El Sheikh M. Abdelrahman ◽  
Mohammed M.A. Amlas
Keyword(s):  
Chemical Weathering ◽  
Iron Ore ◽  
Field Work ◽  
Chemical Precipitation ◽  
Office Work ◽  
River Nile ◽  
Stratigraphic Sequence ◽  
Thin Sections ◽  
Geological Conditions ◽  
Petrographic Study

This paper presents the results of petrographic study of sedimentary iron ore from surface strata of the Shendi -Atbara Basin, River Nile State, Sudan. The aims of this study are to investigate the geological behavior and geological conditions affecting precipitation of sedimentary iron ore. The methodologies have been used to realize the objectives of this study included; field work, office work and labrotary work include thin sections and polished sections analysis. According to field observation sedimentary iron ore can broadly be considered as occurring in three major classes: Ferribands iron, ferricrete iron and oolitic iron ores. The modes of occurrence of iron ore was described at the outcrops and vertical sedimentary profiles revealed that the iron occurred in study area at different types in stratigraphic sequence such as cap, beded and interbeded conformable with Shendi Formation. Petrographic study of iron ore in collected samples using polarized microscope and ore microscope includes study of the textures and structures of ores to obtain ore history. The main types of textures and structures in studied samples are oolitic, granular, lamellar and bands. According to these results the origin of iron ore is formed by chemical precipitation during chemical weathering of surrounding areas in continental lacustrine environment. The iron ore in study area is potential for future mining works and steals industry.

A petrographic study of the Rotliegendes Sandstone reservoir (Lower Permian) in the Rough Gas Field

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 459-477 ◽  
Author(s):  
M. W. Goodchild ◽  
J. H. McD. Whitaker
Keyword(s):  
Sedimentary Facies ◽  
Mineral Dissolution ◽  
Lower Permian ◽  
Secondary Porosity ◽  
Gas Field ◽  
Thin Sections ◽  
Fine Grained ◽  
Groundwater Movement ◽  
Marked Variability ◽  
Sandstone Reservoir

AbstractThe diagenetic history of the Rotliegendes Sandstone reservoir in the Rough Gas Field was studied using thin-sections, XRD analyses and SEM. The Rotliegendes comprises a sequence of fine-grained fluvial sheet-flood sandstones and coarse, gravelly, low-sinuosity channel sandstones, with thin aeolian interbeds, overlain by a sequence of aeolian dune and interdune sandstones. Early, environmentally-related diagnesis (eogenesis) shows a marked variability with sedimentary facies. Within aeolian sandstones, poikilotopic anhydrite and fine, rhombic dolomite are preserved. Fluvially-derived sandstones typically contain infiltrated detrital clays and early authigenic mixed-layer clays, together with coarse, framework-displacive dolomite. Feldspars show varying degrees of alteration within all facies. These eogenetic features reflect patterns of groundwater movement during the Rotliegendes and early Zechstein. Mineral dissolution and precipitation were controlled by the chemistry of the groundwaters. Burial diagenetic (mesogenetic) features are superimposed on eogenetic cements. Authigenic clays have been converted to illitic clays. In addition, mesogenetic chlorite has formed and quartz and strongly ferroan dolomite cements are recognized. These minerals may be related to clay diagenesis within the underlying Carboniferous Coal Measures. Early, framework-supporting anyhdrite, and both phases of dolomite, have been partially dissolved, creating secondary porosity. This is attributed to the action of acidic porewaters, generated by the maturation of organic material within the Carboniferous. Post-dissolution kaolinite, gypsum and minor pyrite infill secondary pores. Gas emplacement from the Late Cretaceous onwards effectively halted further diagenetic reactions.

Reduction and prediction of sandstone reservoir potential, Jurassic , North Sea

1985 ◽  
Vol 315 (1531) ◽  
pp. 187-202 ◽  
Keyword(s):  
North Sea ◽  
Burial Depth ◽  
Pore Waters ◽  
Secondary Porosity ◽  
Depth Data ◽  
General Decline ◽  
Mineral Compositions ◽  
The Difference ◽  
Detrital Mineral ◽  
Reservoir Potential

Porosity, permeability, mineralogical and depth data for two North Sea Jurassic sandstone sequences were analysed. Both sequences show statistically significant negative correlations between present burial depth and porosity. The influence of secondary porosity creation is subordinate to that of the general decline in porosity. For a given burial depth , sequence A is, on average, a little more porous (about 3%) than B. However, for a given porosity sequence A displays a permeability 1—3 orders of magnitude greater than B. The large permeability difference between A and B is a function of authigenic mineralogy. The only significant cement within the reservoir intervals of sequence A is quartz . Sequence B contains authigenic clays, quartz and subordinate carbonate. The abundant authigenic clay in B severely reduced permeability. In both instances, the cements are products of burial and were precipitated from pore waters expelled from shales during compaction. The expelled pore waters were both acidic and rich in solutes; a product of reactions between maturing organic matter, clays and iron oxides. The difference in authigenic mineralogy between the sequences was caused by the reaction between pore waters and sandstones with different detrital mineral compositions. Thus the present reservoir quality is a product of burial and of the reactions between evolving pore fluids and minerals in the sandstone.

Research on Diagenetic Facies Based on Diagenetic Effect in the Low Permeability Sandstone Reservoir - A Case from C81 Reservoir in Huanjiang Region, Ordos Basin

2014 ◽  
Vol 522-524 ◽  
pp. 1274-1279
Author(s):  
Chun Wang ◽  
Zhi Guo Jin ◽  
Cheng Zhi Liu
Keyword(s):  
Physical Properties ◽  
Ordos Basin ◽  
Physical Property ◽  
Low Permeability ◽  
Thin Sections ◽  
Diagenetic Minerals ◽  
Calcite Cementation ◽  
Diagenetic Facies ◽  
Pore Types ◽  
Feldspar Dissolution

The research is carried out on diagenetic minerals, pore types and its impact on the physical properties in Huanjiang C81reservoir of Ordos basin, which is based on reservoir physical property test, thin sections observation and scanning electron microscopy. Several minerals closely associated with reservoir physical properties are identified from diagenetic effect views. It results in that a classification is proposed for the diagenetic facies, consisting of four kinds of diagenetic facies: ferroan calcite cementation facies, hydromica/kaolinite cementation facies, chlorite coating facies and feldspar dissolution facies. The study of C81reservoir in Huanjiang region shows that this scheme is favorable to estimate low permeability reservoir, the result shows fairly good consistency with the distribution of physical property of wells.

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