SEQUENCE STRATIGRAPHIC ARCHITECTURE OF LOWER AND MIDDLE EOCENE CARBONATE PLATFORM, SIRTE BASIN, NORTH CENTRAL LIBYA

2019 ◽  
Author(s):  
Muneer A. Abdalla ◽  
◽  
Wan Yang
Author(s):  
Muneer Abdalla

The lower and upper Paleocene reservoir formations, the primary producing formations in the northwest Sirte Basin, north-central Libya have complex structures which have an impact on the performance of the reservoirs. It is extremely crucial to understand the complex relationships between the fault networks and stratigraphy of the area for future field development. However, delineating faults particularly subtle faults is not an easy process due to the low signal-to-noise ratio in the post stack seismic data despite the effort and careful process of the pre-stack data. Seismic attributes are critical tools in detecting and enhancing major and minor fault interpretation beyond the seismic resolution of the conventional seismic dataset. This study utilizes variance, root mean square, and curvature attributes computed from the post-stack 3D seismic data acquired in the northwest Sirte Basin to detect major and minor faults along an isolated carbonate platform. A spectral whitening and median filter were applied to improve the quality of the data and remove random noise resulted from data acquisition and processing steps. Those methods were utilized to provide high-resolution seismic data and better show edges and structural features. Numerous faults have been detected in the study area. Most major faults in the lower and upper Paleocene reservoir formations are located along the margins of the isolated carbonate platform and have a NW-SE trend. Data conditioning and seismic attribute analyses applied on the 3-D seismic dataset effectively enhanced our understanding of the reservoir complexity and improve the detection of the major and minor faults and fracture zones in the study area.


Facies ◽  
2020 ◽  
Vol 67 (1) ◽  
Author(s):  
Franz T. Fürsich ◽  
Matthias Alberti ◽  
Dhirendra K. Pandey

AbstractThe siliciclastic Jhuran Formation of the Kachchh Basin, a rift basin bordering the Malagasy Seaway, documents the filling of the basin during the late syn-rift stage. The marine, more than 700-m-thick Tithonian part of the succession in the western part of the basin is composed of highly asymmetric transgressive–regressive cycles and is nearly unfossiliferous except for two intervals, the Lower Tithonian Hildoglochiceras Bed (HB) and the upper Lower Tithonian to lowermost Cretaceous Green Ammonite Beds (GAB). Both horizons represent maximum flooding zones (MFZ) and contain a rich fauna composed of ammonites and benthic macroinvertebrates. Within the HB the benthic assemblages change, concomitant with an increase in the carbonate content, from the predominantly infaunal “Lucina” rotundata to the epifaunal Actinostreon marshii and finally to the partly epifaunal, partly infaunal Eoseebachia sowerbyana assemblage. The Green Ammonite Beds are composed of three highly ferruginous beds, which are the MFZ of transgressive–regressive cycles forming the MFZ of a 3rd-order depositional sequence. The GAB are highly ferruginous, containing berthieroid ooids and grains. GAB I is characterized by the reworked Gryphaea moondanensis assemblage, GAB II by an autochthonous high-diversity assemblage dominated by the brachiopods Acanthorhynchia multistriata and Somalithyris lakhaparensis, whereas GAB III is devoid of fossils except for scarce ammonites. The GAB are interpreted to occupy different positions along an onshore–offshore transect with increasing condensation offshore. Integrated analyses of sedimentological, taphonomic, and palaeoecological data allow to reconstruct, in detail, the sequence stratigraphic architecture of sedimentary successions and to evaluate their degree of faunal condensation.


2021 ◽  
pp. SP509-2021-51
Author(s):  
J. Hendry ◽  
P. Burgess ◽  
D. Hunt ◽  
X. Janson ◽  
V. Zampetti

AbstractImproved seismic data quality in the last 10–15 years, innovative use of seismic attribute combinations, extraction of geomorphological data, and new quantitative techniques, have significantly enhanced understanding of ancient carbonate platforms and processes. 3D data have become a fundamental toolkit for mapping carbonate depositional and diagenetic facies and associated flow units and barriers, giving a unique perspective how their relationships changed through time in response to tectonic, oceanographic and climatic forcing. Sophisticated predictions of lithology and porosity are being made from seismic data in reservoirs with good borehole log and core calibration for detailed integration with structural, paleoenvironmental and sequence stratigraphic interpretations. Geologists can now characterise entire carbonate platform systems and their large-scale evolution in time and space, including systems with few outcrop analogues such as the Lower Cretaceous Central Atlantic “Pre-Salt” carbonates. The papers introduced in this review illustrate opportunities, workflows, and potential pitfalls of modern carbonate seismic interpretation. They demonstrate advances in knowledge of carbonate systems achieved when geologists and geophysicists collaborate and innovate to maximise the value of seismic data from acquisition, through processing to interpretation. Future trends and developments, including machine learning and the significance of the energy transition, are briefly discussed.


Author(s):  
Yucel Yilmaz

The island of Cyprus constitutes a fragment of southern Anatolia separated from the mainland by left-oblique transtension in late Cenozoic time. However, a geological framework of offset features of the south-central Anatolia, for comparison of Cyprus with a source region within and west of the southeastern Anatolian suture zone, has not yet been developed. In this paper, I enumerate, describe, and compare a full suite of potentially correlative spatial and temporal elements exposed in both regions. Northern Cyprus and south-central Anatolia have identical tectonostratigraphic units. At the base of both belts, crop out ophiolitic mélange-accretionary complex generated during the northward subduction of the NeoTethyan Oceanic lithosphere from the Late Cretaceous until the end of middle Eocene. The nappes of the Taurus carbonate platform were thrust above this internally chaotic unit during late Eocene. They began to move as a coherent nappe pile from that time onward. An asymmetrical flysch basin was formed in front of this southward moving nappe pile during the early Miocene. The nappes were then thrust over the flysch basin fill and caused its tight folding. Cyprus separated from Anatolia in the Pleistocene-Holocene when, transtensional oblique faults with dip-slip components caused the development of the Adana and Iskenderun basins and the separation of Cyprus from Anatolia.


2019 ◽  
Vol 190 ◽  
pp. 1
Author(s):  
Serge Ferry ◽  
Danièle Grosheny

The first two calcarenite units at the base of the Urgonian limestones on the southern edge of the platform bear different depositional geometries depending on place (Cirque d’Archiane to Montagnette and Rocher de Combau). The lower calcarenite unit (Bi5 of Arnaud H. 1981. De la plate-forme urgonienne au bassin vocontien. Le Barrémo-Bédoulien des Alpes occidentales entre Isère et Buëch (Vercors méridional, Diois oriental et Dévoluy). Géologie Alpine, Grenoble, Mémoire 12: 3. Disponible sur https://tel.archives-ouvertes.fr/tel-00662966/document), is up to 200 m thick and shows three different patterns, in terms of accommodation space, from the western Archiane Cirque to the Montagnette to the east. On the western side of the Cirque, the unit begins on slope fine-grained limestone with thin sigmoïdal offlap geometry, suggesting little available space after a relative sea level fall. It is overlain by thick progradational/aggradational, then purely aggradational calcarenite capped by a coral and rudist-bearing bed. This bed is, therefore, interpreted as a maximum (although moderate) flooding facies. The depositional geometry is different on the eastern side of the Cirque, where a progradational pattern in the lower part of the unit is interrupted by a rotational movement affecting the depositional profile. The deformation promoted aggradation updip and retrogradation downdip as a result of starvation. The inferred growth fault updip (thought to be responsible for the change) began to function earlier at the Montagnette, explaining the huge calcarenite clinoforms found there, filling a deeper saddle created in the depositional profile. The same fault probably was reactivated later during the deposition of the overlying, thinner Bi6-1 unit, which appears at Rocher de Combau with an uncommon tidal facies at the base. A rotational bulge, created by the inferred growth fault, would have protected a small area behind it to spare the local calcarenite deposition from the waves for a while. These two examples show that sequence stratigraphic interpretation may differ from one place to the other, and even show opposite trends due to this kind of disturbance.


2020 ◽  
pp. SP509-2019-78
Author(s):  
M. Minzoni ◽  
A. Cantelli ◽  
J. Thornton ◽  
B. Wignall

AbstractRegional and detailed seismic stratigraphic analyses of Early Cretaceous (Aptian) presalt carbonate sections from offshore Brazil reveal the complex stratigraphic architecture of late- and post-rift lacustrine carbonate systems. The lateral and vertical distribution of calibrated seismic facies within this framework highlights the evolution through time of the carbonate system and bathymetry of the host lacustrine basin. Despite the simple, largely abiotic and microbial components, lacustrine carbonate accumulations formed complex geometries that closely resemble those observed from marine systems, suggesting that a downward tapering carbonate production profile must have occurred. The complexity of the stratigraphic architecture reflects lateral variations in subsidence patterns combined with the interference of the basement topography, palaeo-wind directions, and basinal filling patterns. Well-imaged clinoforms several hundred meters high attest to both the existence of significant lake-bottom topography, locally in excess of 800 meters, and the occurrence of deep water at time of deposition. Platform margin trajectory and vertical and lateral architecture of clinoform packages through time reveal distinct sequence boundaries that can be correlated in detail only locally, demonstrating the impact of syndepositional tectonics, and possibly recurrent isolation of smaller lakes during lowstands. Depositional models from this study fill a gap in current understanding of lacustrine carbonate systems and offer a template for exploration and appraisal of the presalt play.


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