Interplay between tectonic inheritance and salt tectonics in the tectono-sedimentary evolution of the Sahel basin (eastern Tunisia): implications for hydrocarbon prospectivity

2021 ◽  
Author(s):  
Wajdi Belkhiria ◽  
Haifa Boussiga ◽  
Imen Hamdi Nasr ◽  
Adnen Amiri ◽  
Mohamed Hédi Inoubli
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Gravity Data ◽  
Hydrocarbon Exploration ◽  
Passive Margin ◽  
Growth Strata ◽  
Tectonic Inheritance ◽  
Sedimentary Evolution ◽  
Structural Style ◽  
Half Graben

<p>The Sahel basin in eastern Tunisia has been subject for hydrocarbon exploration since the early fifties. Despite the presence of a working petroleum system in the area, most of the drilled wells were dry or encountered oil shows that failed to give commercial flow rates. A better understanding of the tectono-sedimentary evolution of the Sahel basin is of great importance for future hydrocarbon prospectivity. In this contribution, we present integration of 2D seismic reflection profiles, exploration wells and new acquired gravity data. These subsurface data reveal that the Sahel basin developed as a passive margin during Jurassic-Early Cretaceous times and was later inverted during the Cenozoic Alpine orogeny. The occurrence of Triassic age evaporites and shales deposited during the Pangea breakup played a fundamental role in the structural style and tectono-sedimentary evolution of the study area. Seismic and gravity data revealed jointly important deep-seated extensional faults, almost along E-W and few along NNE–SSW and NW-SE directions, delimiting horsts and grabens structures. These syn-rift extensional faults controlled deposition, facies distribution and thicknesses of the Jurassic and Early cretaceous series. Most of these inherited deep-seated normal and transform faults are ornamented by different types of salt-related structures. The first phase of salt rising was initiated mainly along these syn-extensional faults in the Late Jurassic forming salt domes and continued into the Early and Late Cretaceous leading to salt-related diapir structures. During this period, the salt diapirism was accompanied by the development of salt withdrawal minibasins, characterized important growth strata due the differential subsidence. These areas represent important immediate kitchen areas to the salt-related structures. The later Late Cretaceous - Cenozoic shortening phases induced preferential rejuvenation of the diapiric structures and led to the inversion of former graben/half-graben structures and ultimately to vertical salt welds along salt ridges. These salt structures represent key elements that remains largely undrilled in the Sahel basin. Our results improve the understanding of salt growth in eastern Tunisia and consequently greatly impact the hydrocarbon prospectivity in the area.</p>

Tectonostratigraphic development and hydrocarbon reservoir quality on a convergent margin: East Coast, North Island, New Zealand

2009 ◽  
Vol 49 (2) ◽  
pp. 600
Author(s):  
Brad Field ◽  
Jan Baur ◽  
Kyle Bland ◽  
Greg Browne ◽  
Angela Griffin ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
East Coast ◽  
Fractured Reservoirs ◽  
Hydrocarbon Exploration ◽  
Passive Margin ◽  
Source Rocks ◽  
Reservoir Quality ◽  
High Porosity ◽  
Hydrocarbon Reservoir ◽  
Reservoir Potential

Hydrocarbon exploration on the East Coast of the North Island has not yet yielded significant commercial reserves, even though the elements of a working petroleum system are all present (Field et al, 1997). Exploration has focussed on the shallow, Neogene part of the succession, built up during plate margin convergence over the last ∼24 million years. Convergent margins are generally characterised by low-total organic carbon (TOC) source rocks and poor clastic reservoir quality due to poor sorting and labile grains. However, the obliquely-convergent Hikurangi subduction margin of the East Coast has high TOC source rocks that pre-date the subduction phase, and its reservoir potential, though variable, has several aspects in its favour, namely: deep-water rocks of high porosity and permeability; preservation of pore space by overpressure; the presence of fractured reservoirs and hybrid reservoirs, where low clastic permeability is enhanced by fractures. The East Coast North Island is a Neogene oblique subduction margin, with Neogene shelf and slope basins that developed on Late Cretaceous-Paleogene passive margin marine successions. The main hydrocarbon source rocks are Late Cretaceous and Paleocene and the main reservoir potential is in the Neogene (Field et al, 2005). Miocene mudstones with good seal potential are common, as is significant over-pressuring. Neogene deformation controlled basin development and accommodation space and strongly-influenced lateral facies development and fractured reservoirs. Early to Middle Miocene thrusting was followed by later Neogene extension (e.g. Barnes et al 2002), with a return to thrusting in the Pliocene. Local wells have flow-tested gas shows.

APPLICATION OF THE DETACHMENT MODEL FOR CONTINENTAL EXTENSION TO HYDROCARBON EXPLORATION IN EXTENSIONAL BASINS

1989 ◽  
Vol 29 (2) ◽  
pp. 99
Author(s):  
M. A. Etheridge ◽  
P. A. Symonds ◽  
T. G. Powell
Keyword(s):  
Thermal Anomaly ◽  
Hydrocarbon Exploration ◽  
Passive Margin ◽  
Source Rocks ◽  
Normal Faults ◽  
Rift Basin ◽  
Wide Range ◽  
Continental Rifts ◽  
Half Graben ◽  
Transfer Faults

The extension of the continental lithosphere that gives rise to continental rifts and eventually to passive continental margins and their basins is considered generally to involve shear on one or more major, shallow dipping normal faults (detachments). The operation of these detachments induces a basic asymmetry into the extensional terrane that is analogous to that in thrust terranes. As a result, the two sides of a continental rift and conjugate passive margin segments are predicted to have contrasting structure, facies development, subsidence history and thermal evolution.The major structural consequence of the detachment model is that half- graben rather than full graben geometry is expected in rift basins, consistent with recent interpretations in a wide range of continental rifts and passive margins. Half- graben geometry dominates in the Bass Strait basins, the Canning Basin and in a number of Proterozoic rifts, and has been observed on most parts of the Australian continental margin. Variations in the along- strike geometry of extensional basins are accommodated by transfer faults or fault zones. Transfer faults are as important and widespread in rifts as the classical normal faults, and they have important consequences for hydrocarbon exploration (e.g. design of seismic surveys, structural interpretation of seismic data, play and lead development).The fundamental asymmetry of extensional basins, and their compartmentalisation by transfer faults also control to a large extent the distribution of both source and reservoir facies. A model for facies distribution in a typical rift basin is presented, together with its implications for the prime locations of juxtaposed sources and reservoirs. Maturation of syn- rift source rocks depends on both the regional heat flow history and the amount of post- rift subsidence (and therefore burial). Both of these factors are influenced, and are partly predictable by the detachment model. In particular, there may be substantial horizontal offset of both the maximum thermal anomaly and the locus of post- rift subsidence from the rift basin. Analysis of deep crustal geophysical data may aid in the interpretation of detachment geometry and, therefore, of the gross distribution of thermal and subsidence histories.

Cenozoic growth of West Kunlun Mountains and tectono-sedimentary evolution of adjacent SW Tarim Basin-New spatial model based on seismic data

2020 ◽  
Author(s):  
Wenhang Liu ◽  
Piotr Krzywiec ◽  
Stanisław Mazur ◽  
Fanwei Meng ◽  
Qingong Zhuo ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Late Miocene ◽  
Seismic Data ◽  
Large Scale ◽  
Tibet Plateau ◽  
Growth Strata ◽  
Kunlun Mountains ◽  
Sedimentary Evolution ◽  
Structural Style ◽  
Bachu Uplift

<p>Kunlun Mountains, SW part of the Tarim Basin and S edge of the Bachu Uplift in central Asia collectively form the northernmost segment of the vast Cenozoic deformation zone and associated depositional areas formed in course of the India – Euroasia collision. Five seismic transects from the SW Tarim Basin (Yechang - Hotan area) calibrated by deep wells were used in order to assess lateral variations of a structural style and syn-tectonic sedimentation in this part of the basin. Pre-Cenozoic substratum of SW Tarim Basin is formed by crystalline basement covered by Paleozoic strata, with important mid-Cambrian evaporites (Awatage Formation) that served as first, deep detachment level. Cenozoic sedimentary infill consists of several kilometers of shallow water to terrestrial clastics with Paleogene evaporites of the Bashiblake Formation at their base. Paleogene evaporites acted as a second, shallow detachment. Mid – late Miocene to Quaternary wedging along the front of the Kunlun Mts., associated with formation of a large-scale duplex consisting of slivers built of Precambrian to Permian rocks, resulted in progressive, laterally variable uplift of the S margin of the Tarim Basin documented by well-preserved growth strata that have been also described in the field. Jade Anticline, large intra-basinal structure that is located in the central part of the Tarim Basin, previously interpreted as a regional wrenching zone, was reinterpreted as a thin-skinned syn-depositional “fish tail” structure, detached in the Paleogene evaporites and formed in Quaternary above local basement elevation. Northernmost late Miocene compressional deformations have been recognized along the S edge of the Bachu Uplift in its Western and central segment. They formed due to complex interplay of thick-skinned basement reverse faulting responsible for regional elevation of basement blocks, and two types of thin-skinned thrusting: southward directed thrusting detached within the mid-Cambrian evaporites and northward directed thrusting detached within the Paleogene evaporites. Compressional deformations along the S edge of the Bachu Uplift are diminishing and eventually disappearing towards the East. All these findings point to significant transfer of compressional stresses into the far foreland of the W Kunlun Mountains and laterally variable tectonic coupling between the Tibet Plateau and central part of the Tarim Basin.</p><p>Seismic data used in this study was kindly provided by China National Petroleum Corporation (PetroChina). IHS Markit is thanked for providing academic license of Kingdom seismic interpretation software.</p>

scholarly journals Towards a nappe theory: Thermo-mechanical simulations of nappe detachment, transport and stacking in the Helvetic Nappe System, Switzerland

2019 ◽  
Author(s):  
Dániel Kiss ◽  
Thibault Duretz ◽  
Stefan M. Schmalholz
Keyword(s):  
Yield Criterion ◽  
Passive Margin ◽  
Stress Concentrations ◽  
Band Formation ◽  
Creep Flow ◽  
Physical Mechanisms ◽  
Tectonic Inheritance ◽  
Horizontal Transport ◽  
Half Graben ◽  
Basal Shear

Abstract. Tectonic nappes are observed for more than a hundred years. Although geological studies often refer to a nappe theory, the physical mechanisms of nappe formation are still incompletely understood. We apply two-dimensional numerical simulations of shortening of a passive margin, to investigate the thermo-mechanical processes of detachment, transport and stacking of nappes. We use a visco-elasto-plastic model with standard creep flow laws and Drucker-Prager yield criterion. We consider tectonic inheritance with two initial mechanical heterogeneities: (1) lateral heterogeneity of the basement-cover interface due to half-grabens and horsts and (2) vertical heterogeneities due to layering of mechanically strong and weak sedimentary units. The model shows detachment and horizontal transport of a thrust nappe and stacking of this thrust nappe above a fold nappe. The detachment of the thrust sheet is triggered by stress concentrations around the sediment-basement contact and the resulting brittle-plastic shear band formation. The horizontal transport is facilitated by a basal shear zone just above the basement-cover contact, composed of thin, weak sediments. Fold nappe formation occurs by a dominantly ductile closure of a half-graben and the associated extrusion of the half-graben fill. We apply our model to the Helvetic nappe system in Western Switzerland, which is characterized by stacking of the Wildhorn thrust nappe above the Morcles fold nappe. The modeled structures and temperature field agree with data from the Helvetic nappe system. The mechanical heterogeneities must generate contrasts in effective viscosity (i.e. ratio of stress to strain rate) of four orders of magnitude to model nappe structures similar to the ones of the Helvetic nappe system.

scholarly journals Where was the Magura Ocean?

2015 ◽  
Vol 65 (3) ◽  
pp. 319-344 ◽  
Author(s):  
Nestor Oszczypko ◽  
Andrzej Ślączka ◽  
Marta Oszczypko-Clowes ◽  
Barbara Olszewska
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Late Jurassic ◽  
Source Area ◽  
Western Carpathians ◽  
Sedimentary Evolution ◽  
Outer Western Carpathians ◽  
Different Parts

Abstract In the Late Jurassic to Early Cretaceous palaeogeography of the Alpine Tethys the term Ocean is used for different parts of these sedimentary areas: eg. Ligurian – Piedmont and Penninic, Magura, Pieniny, Valais and Ceahlau-Severins oceans. The Magura Ocean occupied the more northern position in the Alpine-Carpathian arc. During the Late Cretaceous–Paleogene tectono-sedimentary evolution the Magura Ocean was transformed into several (Magura, Dukla, Silesian, sub-Silesian and Skole) basins and intrabasinal source area ridges now incorporated into the Outer Western Carpathians.

APPLICATION OF THE DETACHMENT MODEL FOR CONTINENTAL EXTENSION TO HYDROCARBON EXPLORATION IN EXTENSIONAL BASINS

1988 ◽  
Vol 28 (1) ◽  
pp. 167 ◽  
Author(s):  
M.A. Etheridge ◽  
P.A. Symonds ◽  
T.G. Powell
Keyword(s):  
Thermal Anomaly ◽  
Hydrocarbon Exploration ◽  
Passive Margin ◽  
Source Rocks ◽  
Normal Faults ◽  
Rift Basin ◽  
Wide Range ◽  
Continental Rifts ◽  
Half Graben ◽  
Transfer Faults

The extension of the continental lithosphere that gives rise to continental rifts and eventually to passive continental margins and their basins is considered generally to involve shear on one or more major, shallow dipping normal faults (detachments). The operation of these detachments induces a basic asymmetry into the extensional terrane that is analogous to that in thrust terranes. As a result, the two sides of a continental rift and conjugate passive margin segments are predicted to have contrasting structure, facies development, subsidence history and thermal evolution.The major structural consequence of the detachment model is that half-graben rather than full graben geometry is expected in rift basins, consistent with recent interpretations in a wide range of continental rifts and passive margins. Half-graben geometry dominates in the Bass Strait basins, the Canning Basin and in a number of Proterozoic rifts, and has been observed on most parts of the Australian continental margin. Variations in the along-strike geometry of extensional basins are accommodated by transfer faults or fault zones. Transfer faults are as important and widespread in rifts as the classical normal faults, and they have important consequences for hydrocarbon exploration (e.g. design of seismic surveys, structural interpretation of seismic data, play and leav development).The fundam* nal asymmetry of extensional basins, and their compartmentalisation by transfer faults also control to a large extent the distribution of both source and reservoir facies. A model for facies distribution in a typical rift basin is presented, together with its implications for the prime locations of juxtaposed sources and reservoirs. Maturation of synrift source rocks depends on both the regional heat flow history and the amount of post-rift subsidence (and therefore burial). Both of these factors are influenced, and are partly predictable by the detachment model. In particular, there may be substantial horizontal offset of both the maximum thermal anomaly and the locus of post-rift subsidence from the rift basin. Analysis of deep crustal geophysical data may aid in the interpretation of detachment geometry and, therefore, of the gross distribution of thermal and subsidence histories.

scholarly journals Structural setting of the Koum sedimentary basin (north Cameroon) derived from EGM2008 gravity field interpretation

2018 ◽  
Vol 48 (4) ◽  
pp. 281-298
Author(s):  
Yves Shandini ◽  
Patrice Arnaud Kouske ◽  
Severin Nguiya ◽  
Mouzong Pemi Marcelin
Keyword(s):  
3D Model ◽  
Sedimentary Basin ◽  
Gravity Data ◽  
Hydrocarbon Exploration ◽  
Geopotential Model ◽  
Basement Complex ◽  
Multi Scale ◽  
Half Graben ◽  
Northern Edge ◽  
Cenozoic Sediments

Abstract This study is a contribution to the planning of hydrocarbon exploration program of the Koum sedimentary basin in North Cameroon. 3D modeling of WGM2012 gravity data derived from EGM2008 geopotential model in the Koum basin was used together with existing geological and spectral analysis information to give structural picture of the basin. The 3D model of the Koum basin confirms that the basin is developed as a half graben bounded by sub-vertical faults. The thickness of the Cenozoic sediments is about 1.5 km in the eastern part and reaches 4.5 km in the western part of the basin. Gravity lineaments computed by multi-scale analysis revealed structural trends in the E–W, NW–SE, NE–WS and N–S directions. The faults in the sedimentary terrain reach 6 km depth and have a predominant NW–SE trend with E–W trending faults along the contact between the sedimentary section and the basement complex in the northern edge.

HALF-GRABEN MODEL FOR THE STRUCTURAL EVOLUTION OF THE FITZROY TROUGH, CANNING BASIN, AND IMPLICATIONS FOR RESOURCE EXPLORATION

1988 ◽  
Vol 28 (1) ◽  
pp. 76 ◽  
Author(s):  
B.J. Drummond ◽  
M.A. Etheridge ◽  
P.J. Davies ◽  
M.F. Middleton
Keyword(s):  
Structural Evolution ◽  
Passive Margin ◽  
Normal Faults ◽  
Canning Basin ◽  
North East ◽  
The North ◽  
Structural Style ◽  
Half Graben ◽  
Resource Exploration ◽  
Transfer Faults

The Fitzroy Trough is a north-west/south-east trending rift along the north-east margin of the Canning Basin. The major crustal extension in the trough occurred in the Middle Devonian to Early Carboniferous. Most idealised cross-sections show down-to-trough normal faults bounding both sides of the trough. In contrast, we show the trough to have a half- graben style, with one side a hinge zone or flexure, and the other side bounded by normal faults. Thus, the basin has marked structural asymmetry. The sense of asymmetry switches several times along strike with the hinged margin on the north-eastern margin in some places and the south-west margin in others. The switching in asymmetry occurs at transfer faults. This structural style is expected in extensional tectonic models where the extension occurs on a detachment surface and is typical of many continental and passive margin rifts. The asymmetry of the Palaeozoic structure has implications for resource exploration because of its influence on facies development in and subsequent structural evolution of the trough. Quite different syn-rift clastic and carbonate facies are expected on faulted and hinged margins of a half-graben. Post-rift subsidence will also be somewhat asymmetric, influencing the carbonate reef geometry in particular. Mesozoic deformation in the basin reactivated many of the Palaeozoic normal and transfer faults, and induced reverse slip up basement surfaces on the hinged margin segments.

Salt tectonics versus delamination of the supra-salt cover during extension and compression – 3D geometry and Mesozoic evolution of the Goleniów salt structure, NW Poland

2020 ◽  
Author(s):  
Łukasz Grzybowski ◽  
Piotr Krzywiec
Keyword(s):  
Late Cretaceous ◽  
Thick Layer ◽  
Early Jurassic ◽  
Late Triassic ◽  
Upper Permian ◽  
Salt Diapir ◽  
Growth Strata ◽  
Basin Inversion ◽  
Salt Structure ◽  
Half Graben

<p>The Goleniów salt structure (GSS) is located in the NW part of the Polish Basin which belongs to a system of Permian-Mesozoic epicontinental sedimentary basins of the Western and Central Europe. Its axial part (so called Mid Polish Trough – MPT) was filled with several kilometres of sediments, mainly siliciclastic and carbonates but also with Zechstein (Upper Permian) evaporites. The Polish Basin was fully inverted in Late Cretaceous-Paleogene. The presence of thick layer of evaporites led formation of diverse salt structures. The study area is located within the SW flank of the MPT, characterized by presence of numerous salt and salt-related structures. One of them is NNW-SSE oriented Goleniów structure which extends over 25 km with the salt diapir (salt wall) in its NNW part. Interpretation of the dense array of 2D seismic reflection profiles allowed for the construction of the 3D model of the GSS and assess its spatial evolution including significant role of delamination of the supra-salt Mesozoic sedimentary cover during both extension (basin subsidence) as well as compression (basin inversion).</p><p>NNW part of the Goleniów structure is formed by a well-developed salt diapir (salt wall). Its evolution started in Late Triassic when regional extension triggered formation of the asymmetric reactive diapir. After Late Triassic-Early Jurassic active piercement, diapir continued its growth as a passive diapir due to a regional extensional tectonic regime. In Middle and Late Jurassic, insufficient amount of salt in the source layer led to diapir burial. Further extension caused diapir to fall. This resulted in Early Cretaceous localised extension within the crestal part of the diapir and formation of a half-graben filled with Lower Cretaceous sediments of increased thickness. The Goleniów structure was significantly re-shaped during Late Cretaceous inversion of the Polish Basin. GSS was rejuvenated and started to growth which led to roof uplift and its partial erosion. This progressive compression-related Late Cretaceous growth is very well documented by growth strata preserved above the diapir. Finally, after completion of inversion of the Polish Basin, salt crest reached in Cenozoic groundwater active circulation zone which in turn caused its dissolution and eventually development of the dissolution-collapse trough filled with Cenozoic sediments with increased thickness.</p><p>The style of the deformation alongstrike changes toward the SSE where, due to smaller amount of evaporites salt diapir did not form and was replaced by a complex zone of thin-skinned deformation detached within Zechstein evaporites. First, thin-skinned half-graben was formed during Late Triassic-Early Jurassic extensional phase. It was then compressionally reactivated during basin inversion and this led to enhanced delamination and then thrusting within the Upper Triassic (Keuper) section. Complex backthrusting and local wedging was related to formation of a secondary detachment level within Keuper evaporites and resulted in formation of "fish tail" structure. Backthrusting was associated with substantial folding of hangingwall strata.</p>

scholarly journals Tectonic inheritance controls nappe detachment, transport and stacking in the Helvetic nappe system, Switzerland: insights from thermomechanical simulations

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 287-305 ◽  
Author(s):  
Dániel Kiss ◽  
Thibault Duretz ◽  
Stefan Markus Schmalholz
Keyword(s):  
Structural Evolution ◽  
Passive Margin ◽  
Stress Concentrations ◽  
Creep Flow ◽  
Tectonic Inheritance ◽  
Horizontal Transport ◽  
Half Graben ◽  
Thermomechanical Processes ◽  
Von Mises ◽  
Basal Shear

Abstract. Tectonic nappes have been investigated for more than a hundred years. Although geological studies often refer to a “nappe theory”, the physical mechanisms of nappe formation are still disputed. We apply two-dimensional numerical simulations of shortening of a passive margin to investigate the thermomechanical processes of detachment (or shearing off), transport and stacking of nappes. We use a visco-elasto-plastic model with standard creep flow laws, Drucker–Prager and von Mises yield criteria. We consider tectonic inheritance with two initial mechanical heterogeneities: (1) lateral heterogeneity of the basement–cover interface due to half-grabens and horsts and (2) vertical heterogeneities due to layering of mechanically strong and weak sedimentary units. The model shows detachment and horizontal transport of a thrust nappe that gets stacked on a fold nappe. The detachment of the thrust sheet is triggered by stress concentrations around the sediment–basement contact and the resulting brittle–plastic shear band that shears off the sedimentary units from the sediment–basement contact. Horizontal transport is facilitated by a basal shear zone just above the basement–cover contact, composed of thin, weak sediments that act as a décollement. Fold nappe formation occurs by a dominantly ductile closure of a half-graben and the associated extrusion of the half-graben fill. We apply our model to the Helvetic nappe system in western Switzerland, which is characterized by stacking of the Wildhorn thrust nappe above the Morcles fold nappe. The modeled structures, the deformation rates and the temperature field agree with data from the Helvetic nappe system. Mechanical heterogeneities must locally generate effective viscosity (i.e., ratio of stress to viscoplastic strain rate) contrast of about 3 orders of magnitude to model nappe structures similar to the ones of the Helvetic nappe system. Our results indicate that the structural evolution of the Helvetic nappe system was controlled by tectonic inheritance and that material softening mechanisms are not essential to reproduce the first-order nappe structures.

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