scholarly journals The impact of diagenesis on the reservoir quality of the early Cretaceous Lower Goru sandstones in the Lower Indus Basin, Pakistan

2021 ◽  
Author(s):  
Qamar UZ Zaman Dar ◽  
Renhai Pu ◽  
Christopher Baiyegunhi ◽  
Ghulam Shabeer ◽  
Rana Imran Ali ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Pore Space ◽  
Hydrocarbon Exploration ◽  
Indus Basin ◽  
Coarse Grained ◽  
Rock Properties ◽  
Reservoir Properties ◽  
Diagenetic Processes ◽  
Lower Indus Basin ◽  
The Impact

AbstractThe sandstone units of the Early Cretaceous Lower Goru Formation are significant reservoir for gas, oil, and condensates in the Lower Indus Basin of Pakistan. Even though these sandstones are significant reservoir rocks for hydrocarbon exploration, the diagenetic controls on the reservoir properties of the sandstones are poorly documented. For effective exploration, production, and appraisal of a promising reservoir, the diagenesis and reservoir properties must be comprehensively analyzed first. For this study, core samples from depths of more than 3100 m from the KD-01 well within the central division of the basin have been studied. These sandstones were analyzed using petrographic, X-ray diffraction, and scanning electron microscopic analyses to unravel diagenetic impacts on reservoir properties of the sandstone. Medium to coarse-grained and well-sorted sandstone have been identified during petrographic study. The sandstone are categorized as arkose and lithic arkose. Principal diagenetic events which have resulted in changing the primary characters of the sandstones are compaction, cementation, dissolution, and mineral replacement. The observed diagenetic processes can be grouped into early, burial, and late diagenesis. Chlorite is the dominant diagenetic constituent that occurs as rims, coatings, and replacing grains. The early phase of coating of authigenic chlorite has preserved the primary porosity. The recrystallization of chlorite into chamosite has massively reduced the original pore space because of its bridging structure. The current study reveals that diagenetic processes have altered the original rock properties and reservoir characteristics of the Lower Goru sandstone. These preliminary outcomes of this study have great potential to improve the understanding of diagenetic process and their impact on reservoir properties of the Lower Goru sandstone in the Lower Indus Basin and adjoining areas.

scholarly journals Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

2021 ◽  
Vol 80 (3) ◽  
pp. 1963-1980
Author(s):  
Solomon Adomako ◽  
Christian John Engelsen ◽  
Rein Terje Thorstensen ◽  
Diego Maria Barbieri
Keyword(s):  
Los Angeles ◽  
Crystal Size ◽  
Grain Shape ◽  
Mechanical Performance ◽  
Pore Space ◽  
Construction Material ◽  
Engineering Properties ◽  
Coarse Grained ◽  
The Impact ◽  
The Relationship

AbstractRock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-Deval tests. It was found that high content of primary minerals in rocks (e.g. quartz and feldspar) is a significant parameter for performance evaluation. Traces of secondary and accessory minerals also affect the performance of rocks, although in many cases it is based on the percentage. Furthermore, some studies showed that the effect of mineralogic composition on mechanical strength is not sufficient to draw final conclusions of mechanical performance; therefore, the impact of other textural characteristics should be considered. The disposition of grain size and crystal size (e.g. as result of lithification) showed that rocks composed of fine-grain textural composition of ≤ 1 mm enhanced fragmentation and wear resistance than medium and coarse grained (≥ 1 mm). The effect of grain shape was based on convex and concave shapes and flat and elongated apexes of tested samples. The equidimensional form descriptor of rocks somehow improved resistance to impact from LA than highly flat and elongated particles. Lastly, the distribution of pore space investigated by means of the saturation method mostly showed moderate (R = 0.50) to strong (R = 0.90) and positive correlations to LA and MD tests.

scholarly journals Diagenetic Processes and Reservoir Heterogeneity in Salt-Encased Microbial Carbonate Reservoirs (Late Neoproterozoic, Oman)

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Stephan Becker ◽  
Lars Reuning ◽  
Joachim E. Amthor ◽  
Peter A. Kukla
Keyword(s):  
Carbonate Reservoirs ◽  
Salt Diapir ◽  
Strong Impact ◽  
Field Scale ◽  
Reservoir Properties ◽  
Heterogeneous Distribution ◽  
Near Surface ◽  
Porosity Reduction ◽  
Diagenetic Processes ◽  
The Impact

A common problem in dolomite reservoirs is the heterogeneous distribution of porosity-reducing diagenetic phases. The intrasalt carbonates of the Ediacaran-Early Cambrian Ara Group in the South Oman Salt Basin represent a self-sourcing petroleum system. Depositional facies and carbonate/evaporite platform architecture are well understood, but original reservoir properties have been modified by diagenesis. Some of the carbonate reservoirs failed to produce hydrocarbons at acceptable rates, which triggered this study. The extent of primary porosity reduction by diagenetic phases was quantified using point counting. To visualize the distribution of diagenetic phases on a field scale, we constructed 2D interpolation diagenesis maps to identify patterns in cementation. The relative timing of diagenetic events was constrained based on thin-section observations and stable isotope analyses. Near-surface diagenesis is dominated by reflux-related processes, leading to porosity inversion in initial highly porous facies and a patchy distribution of early cements. This strong diagenetic overprint of primary and early diagenetic porosity by reflux-related cements leads to a reduction of stratigraphic and facies control on porosity. Calcite was identified as a burial-related cement phase that leads to an almost complete loss of intercrystalline porosity and permeability. Bitumen is an important pore-occluding phase and time marker of the deep-burial realm. The stratigraphic position of the dolomite reservoirs embedded at the base of a salt diapir had a strong impact on its diagenetic development. The salt isolated the dolomites from external fluids, leading to a closed system diagenesis and the buildup of near lithostatic fluid pressures. In combination, these processes decreased the impact of further burial diagenetic processes. The study highlights that cement distribution in salt-encased carbonate reservoirs is mainly related to early diagenetic processes but can be very heterogeneous on a field scale. Further work is needed to implement these heterogeneities in an integrated numerical reservoir model.

Diagenetic Evolution and Reservoir Quality of Sandstones in the North Alpine Foreland Basin: A Microscale Approach

2015 ◽  
Vol 21 (5) ◽  
pp. 1123-1137 ◽  
Author(s):  
Doris Gross ◽  
Marie-Louise Grundtner ◽  
David Misch ◽  
Martin Riedl ◽  
Reinhard F. Sachsenhofer ◽  
...  
Keyword(s):  
Foreland Basin ◽  
Gas Production ◽  
Coarse Grained ◽  
Reservoir Quality ◽  
Reservoir Properties ◽  
The North ◽  
North Alpine Foreland Basin ◽  
Alpine Foreland ◽  
Alpine Foreland Basin ◽  
The Impact

AbstractSiliciclastic reservoir rocks of the North Alpine Foreland Basin were studied focusing on investigations of pore fillings. Conventional oil and gas production requires certain thresholds of porosity and permeability. These parameters are controlled by the size and shape of grains and diagenetic processes like compaction, dissolution, and precipitation of mineral phases. In an attempt to estimate the impact of these factors, conventional microscopy, high resolution scanning electron microscopy, and wavelength dispersive element mapping were applied. Rock types were established accordingly, considering Poro/Perm data. Reservoir properties in shallow marine Cenomanian sandstones are mainly controlled by the degree of diagenetic calcite precipitation, Turonian rocks are characterized by reduced permeability, even for weakly cemented layers, due to higher matrix content as a result of lower depositional energy. Eocene subarkoses tend to be coarse-grained with minor matrix content as a result of their fluvio-deltaic and coastal deposition. Reservoir quality is therefore controlled by diagenetic clay and minor calcite cementation.Although Eocene rocks are often matrix free, occasionally a clay mineral matrix may be present and influence cementation of pores during early diagenesis. Oligo-/Miocene deep marine rocks exhibit excellent quality in cases when early cement is dissolved and not replaced by secondary calcite, mainly bound to the gas–water contact within hydrocarbon reservoirs.

scholarly journals Testing geologic assumptions and scenarios in carbonate exploration: Insights from integrated stratigraphic, diagenetic, and seismic forward modeling

2018 ◽  
Vol 37 (9) ◽  
pp. 672-680 ◽  
Author(s):  
Cyprien Lanteaume ◽  
François Fournier ◽  
Matthieu Pellerin ◽  
Jean Borgomano
Keyword(s):  
Spatial Distribution ◽  
Forward Modeling ◽  
Reservoir Properties ◽  
Modeling Approaches ◽  
Diagenetic Processes ◽  
Stratigraphic Architecture ◽  
Carbonate Deposition ◽  
Seismic Models ◽  
Seismic Reflectors ◽  
The Impact

Carbonates are considered complex, heterogeneous at all scales, and unfortunately often poorly seismically imaged. We propose a methodology based on forward-modeling approaches to test the validity of common exploration assumptions (e.g., chronostratigraphic value of seismic reflectors) and of geologic interpretations (e.g., stratigraphic correlations and depositional and diagenetic architecture) that are determined from a limited amount of data. The proposed workflow includes four main steps: (1) identification and quantification of the primary controls on carbonate deposition and the prediction of the carbonate stratigraphic architecture (through stratigraphic forward modeling); (2) identification of diagenetic processes and prediction of the spatial distribution of diagenetic products (diagenetic forward modeling); (3) quantification of the impact of diagenesis on acoustic and reservoir properties; and (4) computation of synthetic seismic models based on various scenarios of stratigraphic and diagenetic architectures and comparison with actual seismic. The likelihood of a given scenario is tested by quantifying the misfit between the modeled versus the real seismic. This workflow illustrates the relevance of forward-modeling approaches for building realistic models that can be shared by the various disciplines of carbonate exploration (sedimentology, stratigraphy, diagenesis, seismic, geomodeling, and reservoir).

scholarly journals Hydrothermal-metasomatic systems as the most important factor for the formation of elements of the oil and gas-bearing complex in the Bazhenov-Abalak sediments

Georesursy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 142-151
Author(s):  
Evgenia V. Karpova ◽  
Aleksey O. Khotylev ◽  
Ekaterina A. Manuilova ◽  
Aleksandr A. Mayorov ◽  
Elizaveta A. Krasnova ◽  
...  
Keyword(s):  
Carbonate Rocks ◽  
Oil And Gas ◽  
Pore Space ◽  
Structural Elements ◽  
Mineral Formation ◽  
Reservoir Properties ◽  
Thin Sections ◽  
The Impact ◽  
Gas Bearing ◽  
Scanning Electron

A model of the activity of hydrothermal-metasomatic systems confined to certain structural elements is proposed in the present article. The model is based on the analysis of a large volume of traditional studies: measurements of porosity coefficients, permeability, pyrolytic measurements - together with specific measurements: isotopic composition of carbonate rocks, temperature of homogenization of gas-liquid inclusions, studies of the composition of rocks with a scanning electron microscope, a description of petrographic thin sections. The model allows to generalize the results of the impact of hydrothermal-metasomatic systems on the reservoir properties of the rocks of the Bazhenov-Abalak complex: constructive – leaching processes and increasing reservoir properties, and destructive – massive mineral formation that fills the pore space, up to the formation of secondary seals.

The effects of azimuthal anisotropy on 3D and 4D seismic amplitude variation with offset responses

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. C251-C267
Author(s):  
Lisa J. Gavin ◽  
David Lumley
Keyword(s):  
Feasibility Studies ◽  
Azimuthal Anisotropy ◽  
Pore Fluid ◽  
Hydrocarbon Exploration ◽  
Rock Properties ◽  
Reservoir Properties ◽  
Amplitude Variation ◽  
North West ◽  
Fluid Saturation ◽  
4D Seismic

Seismic reflection amplitude variation with source-receiver offset (AVO) is an important tool in hydrocarbon exploration and reservoir monitoring, due to its sensitivity to elastic rock properties that are affected by changes in pore-fluid saturation and pressure. In most cases, 4D seismic feasibility studies and interpretation analyses assume that the earth is isotropic. This assumption can be problematic because it is becoming increasingly apparent that anisotropic rocks are quite common. Furthermore, the presence of even small amounts of anisotropy can have significant effects on AVO, and in the presence of azimuthal anisotropy the AVO will vary with azimuth. We determine that if 4D seismic surveys are acquired with different survey azimuths in the presence of azimuthal anisotropy, it is likely that 4D AVO interpretations will be significantly affected, leading to incorrect or nonphysical interpretations. This possibility is especially apparent in the context of the North West Shelf, Australia, where significant stress-induced azimuthal anisotropy is prevalent in sandstone formations that form the reservoir rocks. We model 4D AVO responses with and without azimuthal anisotropy effects for a variety of pore-fluid saturation and pressure change scenarios using average reservoir properties from the Stybarrow field, Australia. We found that azimuthal anisotropy does not affect the small reflection angles of the 4D AVO response, but it has a significant effect on larger reflection angles when comparing 4D surveys acquired at different acquisition azimuths. This azimuthal behavior leads to what we call an “apparent 4D effect” when reservoir properties do not change and a “contaminated 4D effect” when reservoir properties do change. We found real data examples in which we determine that the 4D AVO response must incorporate azimuthal anisotropy to be explained correctly. Our results further emphasize the importance of repeating survey acquisition azimuths whenever possible and/or accurately accounting for azimuthal anisotropy effects.

Charakterystyka utworów czerwonego spągowca w aspekcie badań rentgenowskiej mikrotomografii komputerowej i mikroskopii optycznej

Nafta-Gaz ◽  
2020 ◽  
Vol 76 (11) ◽  
pp. 765-773
Author(s):  
Marek Dohnalik ◽  
◽  
Konrad Ziemianin ◽  
Keyword(s):  
Pore Space ◽  
Mercury Porosimetry ◽  
Mineralogical Composition ◽  
Effective Porosity ◽  
Hydrocarbon Exploration ◽  
Core Material ◽  
Reservoir Properties ◽  
Average Value ◽  
Full Characterization ◽  
Single Well

The article presents the results of microtomographic and petrographic investigations of Rotliegend sandstones collected from core material from wells located in the area of the Fore-Sudetic Monocline in its central and northern parts and also on the border of the Fore-Sudetic Monocline and the Mogilno - Łódź Synclinorium. Three areas were selected for the study: Czarna Wieś–Parzęczewo (19 samples), Środa Wielkopolska–Kromolice (21 samples) and Siekierki–Miłosław (21 samples). The aim of the petrologic and microtomographic studies was to investigate how the different reservoir properties of sandstones will be reflected in the results of the methods used. Strong differences between samples from the region of Środa Wielkopolska–Kromolice and the other studied areas have been demonstrated. In the case of this area several key factors were noticed: the highest average value of effective porosity; the highest average content of pores belonging to class VII (pore volume subsystem classification); three times higher average value of the CT porosity coefficient and the largest length of the average chord. Also in terms of petrography (composition of grains, cement type) it is a region where major differences, especially compared to the region of Czarna Wieś–Parzęczewo, can be seen. Based on the obtained results, it was possible to rank the examined regions in terms of their reservoir properties – from the worst (Czarna Wieś–Parzęczewo) to the best (Środa Wielkopolska–Kromolice). These conclusions are also confirmed by other petrophysical analyses (eg. mercury porosimetry, permeability analysis). Combination of the obtained microtomographic and petrographic results allowed to obtain a full characterization of the investigated samples – both in terms of the mineralogical composition of grains, as well as the development of the pore space. These data, especially in combination with the results of density and porosity analyses (helium pycnometry and mercury porosimetry), open up a number of possibilities to carry out different types of modeling (porosity, permeability) both on the scale of the sample itself, as well as the scale of a single well or even the whole basin, which is crucial for creating a hydrocarbon exploration strategy.

scholarly journals Evaluation of Gas Potential in Early Cretaceous Shale Lower Indus Basin, Pakistan

2020 ◽  
Vol 11 (1) ◽  
pp. 123-129
Author(s):  
Bilal Ahmed ◽  
Mohibullah Mohibullah ◽  
Sadiq Jalal ◽  
Shabeer Ahmed Abbasi ◽  
Abdul Salam Khan ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Vitrinite Reflectance ◽  
Empirical Relation ◽  
Indus Basin ◽  
Peak Oil ◽  
Gas Generation ◽  
Geochemical Parameters ◽  
Lower Indus Basin ◽  
Lower Goru Formation ◽  
Gas Potential

The shale gas potential of the early Cretaceous Talhar shale member of the lower Goru Formation in lower Indus basin of Sanghar district, Sindh province, has been evaluated using 2D seismic and well logs data. Graphical and empirical techniques were applied to calculate various geochemical parameters for the evaluation of shale plays. Total Organic Carbon (TOC) is calculated by Passey's (∆LogR) Overlay technique and its values are about 2.44 wt.%. Vitrinite Reflectance (Ro) is estimated by graphical and empirical relation and the value lies between 0.95-1.0 which implies that the Talhar shale member is in peak oil and initial gas generation phase. Log-derived Maturity Index (LMI) is calculated by NPHI, RHOB or density log and uranium logs. The average value is about 0.55 which reflects that the formation is probably in the initial maturation phase. Kerogen Volume (Vk) is estimated by empirical relation using RHOB log as input and it is about 13 wt. % which reflects that the formation has enough potential of oil/gas expulsion. The results are compared and validated with a study of the adjacent field of the same basin. This study reveals that Talhar member of lower Goru Formation could be the future probable potential unconventional reservoir for exploration in lower Indus basin of Pakistan.

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