Structural features and formation conditions of mud diapirs in the Andaman Sea Basin

2018 ◽  
Vol 156 (4) ◽  
pp. 659-668 ◽  
Author(s):  
WENGANG HE ◽  
JIANXUN ZHOU
Keyword(s):  
Oil And Gas ◽  
Tectonic Setting ◽  
Geothermal Gradient ◽  
Structural Features ◽  
Andaman Sea ◽  
Accretionary Wedge ◽  
Sedimentation Rates ◽  
Gas Chimney ◽  
Mud Diapir ◽  
Northern Segment

AbstractData from offshore oil and gas explorations have revealed that mud diapirs occur widely not only at continental margins but also in foreland basins and may have played an important role in the entrapment of oil and gas. Although the structural features and formation mechanism of salt diapirs have been extensively investigated, mud diapirs are still not fully understood, largely due to the difficulty of identifying them from seismic data. In this paper, the structural features and main controlling factors of mud diapirs in the Andaman Sea Basin are investigated based on seismic profiles combined with drilling data and regional tectonic settings. The results show that there are five types of mud diapir in the Andaman Sea Basin: turtleback mud diapir, mud dome, piercing mud diapir, mud volcano and gas chimney-like mud diapir. Turtleback mud diapirs mainly occur in the southern segment of the accretionary wedge of the Andaman Sea Basin, which is far from the Bengal Fan and characterized by low deposition rate and strong compression tectonic setting. Piercing mud diapirs exist mainly in the central segment of the accretionary wedge, which is close to provenances of sediments and characterized by rapid sedimentation rates, large mudstone thickness and transpressional tectonic setting. Mud domes and mud volcanoes mainly occur in the northern segment of the accretionary wedge, which is characterized by rapid sedimentation rates, large mudstone thickness and sedimentary wedge growth tectonic setting. The gas chimney-like mud diapirs only occur in the northern segment of the back-arc depression close to the Sagaing strike-slip fault belt, which is characterized by high deposition rate, large mudstone thickness and high geothermal gradient. These features suggest that thick mudstone deposit, rapid sedimentation rates, large geothermal gradient, strong tectonic stress and gravitational spreading and sliding may have prompted the formation of mud diapirs in the Andaman Sea Basin.

The uplift of high-pressure-low-temperature metamorphic rocks

1987 ◽  
Vol 321 (1557) ◽  
pp. 87-103 ◽  
Keyword(s):  
Tectonic Setting ◽  
Geothermal Gradient ◽  
Dominant Mode ◽  
Metamorphic Rocks ◽  
Return Flow ◽  
Accretionary Wedge ◽  
Moderate Amount ◽  
Low Viscosity ◽  
Buoyancy Forces ◽  
Flowing Material

The uplift of high- P -low- T metamorphic rocks has been attributed to buoyancy, diapirism, or hydrodynamically driven return flow. Buoyancy forces can return material subducted into the mantle only if subduction slows or ceases, reducing the downward traction. The buoyancy forces will be reversed within the crust, because of the increased density of high- P assemblages, and therefore can not cause the subducted material to rise beyond the base of the crust. Diapirism and hydrodynamic flow processes require a low-density, low-viscosity matrix, and can only explain the emplacement of relatively small bodies of high- P rock entrained in the flowing material. The tectonic setting of coherent regional high- P —low- T terrains can be explained in terms of the mechanical behaviour of an accretionary wedge with negligible yield strength, where underplating is the dominant mode of accretion. Underplating thickens the wedge from beneath and increases its surface slope. This causes the upper part of the wedge to extend horizontally, even though convergence is continuing. Continued underplating beneath and extension above can allow the oldest high- P rocks to rise to within reach of a moderate amount of erosion on a time scale of the order of 10 Ma. As long as subduction continues beneath the wedge, the geothermal gradient will not relax to a normal value. This process explains (a) the evidence that high- P -low- T rocks are commonly uplifted while convergence is continuing; (b) the absence in many cases of significant overprinting by higher- T assemblages; (c) the position of the oldest and highest pressure rocks in the upper rear of orogenic wedges; (d) the lack of adequate tectonic thicknesses of overlying rock to explain the metamorphism; and (e) the common occurrence of post-metamorphic faults that excise parts of the metamorphic zonation.

scholarly journals New seismological data from the Calabrian arc reveal arc-orthogonal extension across the subduction zone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tiziana Sgroi ◽  
Alina Polonia ◽  
Graziella Barberi ◽  
Andrea Billi ◽  
Luca Gasperini
Keyword(s):  
Lateral Displacement ◽  
Tectonic Setting ◽  
Plate Boundary ◽  
Velocity Model ◽  
Tectonic Deformation ◽  
Accretionary Wedge ◽  
Tectonic Structures ◽  
Plate Convergence ◽  
Seismogenic Layer ◽  
Regional Tectonic

AbstractThe Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

New insights into the Hercynian Orogeny, and their implications for the Paleozoic Hydrocarbon System in the Arabian Plate

GeoArabia ◽  
2009 ◽  
Vol 14 (3) ◽  
pp. 199-228 ◽  
Author(s):  
Mohammad Faqira ◽  
Martin Rademakers ◽  
AbdulKader M. Afifi
Keyword(s):  
Oil And Gas ◽  
Seismic Imaging ◽  
Structural Features ◽  
Source Rocks ◽  
Arabian Plate ◽  
Arabian Shield ◽  
Tectonic Event ◽  
Angular Unconformity ◽  
The North ◽  
Hercynian Orogeny

ABSTRACT During the past decade, considerable improvements in the seismic imaging of the deeper Paleozoic section, along with data from new well penetrations, have significantly improved our understanding of the mid-Carboniferous deformational event. Because it occurred at the same time as the Hercynian Orogeny in Europe, North Africa and North America it has been commonly referred to by the same name in the Middle East. This was the main tectonic event during the late Paleozoic, which initiated or reactivated many of the N-trending block uplifts that underlie the major hydrocarbon accumulations in eastern Arabia. The nature of the Hercynian deformation away from these structural features was poorly understood due to inadequate seismic imaging and insufficient well control, along with the tectonic overprint of subsequent deformation events. Three Hercynian NE-trending arches are recognized in the Arabian Plate (1) the Levant Arch, which extended from Egypt to Turkey along the coast of the Mediterranean Sea, (2) the Al-Batin Arch, which extended from the Arabian Shield through Kuwait to Iran, and (3) the Oman-Hadhramaut Arch, which extended along the southeast coast of Oman and Yemen. These arches were initiated during the mid-Carboniferous Hercynian Orogeny, and persisted until they were covered unconformably by the Khuff Formation during the Late Permian. Two Hercynian basins separate these arches: the Nafud-Ma’aniya Basin in the north and Faydah-Jafurah Basin in the south. The pre-Hercynian Paleozoic section was extensively eroded over the arches, resulting in a major angular unconformity, but generally preserved within the basins. Our interpretation suggests that most of the Arabian Shield, except the western highlands along the Red Sea, is the exhumed part of the Al-Batin Arch. The Hercynian structural fabric of regional arches and basins continue in northern Africa, and in general appear to be oriented orthogonal to the old margin of the Gondwana continent. The Hercynian structure of arches and basins was partly obliterated by subsequent Mesozoic and Cenozoic tectonic events. In eastern Saudi Arabia, Qatar, and Kuwait, regional extension during the Triassic formed N-trending horsts and graben that cut across the NE-trending Hercynian mega-structures, which locally inverted them. Subsequent reactivation during the Cretaceous and Neogene resulted in additional growth of the N-trending structures. The Hercynian Arches had major impact on the Paleozoic hydrocarbon accumulations. The Silurian source rocks are generally preserved in the basins and eroded over the arches, which generally confined Silurian-sourced hydrocarbons either within the basins or along their flanks. Furthermore, the relict Hercynian paleo-topography generally confined the post-Hercynian continental clastics of the Unayzah Formation and equivalents to the Hercynian basins. These clastics contain the main Paleozoic oil and gas reservoirs, particularly along the basin margins where they overlie the sub-crop of the Silurian section with angular unconformity, thus juxtaposing reservoir and source rock.

THE STRUCTURAL DEVELOPMENT AND HYDROCARBON POTENTIAL OF PALAEOZOIC SOURCE ROCKS IN THE ADAVALE BASIN REGION

1984 ◽  
Vol 24 (1) ◽  
pp. 393 ◽  
Author(s):  
V. L. Passmore ◽  
M. J. Sexton
Keyword(s):  
Middle Devonian ◽  
Oil And Gas ◽  
Structural Features ◽  
Source Rocks ◽  
Geochemical Data ◽  
Mature Stage ◽  
Hydrocarbon Generation ◽  
Structural Development ◽  
Seismic Reflection Data ◽  
Basin Region

The Adavale Basin of southwestern Queensland consists of a main depression and several isolated synclinal extensions, traditionally referred to as troughs. The depressions and troughs are erosional remnants of a once more extensive Devonian depositional basin, and are now completely buried by sediments of the overlying Cooper, Galilee and Eromanga Basins. Geophysical and drilling investigations undertaken since 1959 are the only source of information on the Adavale Basin. A single sub-economic discovery of dry gas at Gilmore and a few shows of oil and gas are the only hydrocarbons located in the basin to date.In 1980, the Bureau of Mineral Resources in cooperation with the Geological Survey of Queensland commenced a major, multidisciplinary investigation of the basins in southwestern Queensland. Four long (> 200 km) seismic lines from this study over the Adavale Basin region and geochemical data from 20 wells were used to interpret the Adavale Basin's development and its present hydrocarbon potential.The new seismic reflection data allow the well-explored main depression to be correlated with the detached troughs, some of which have little or no well information. The BMR seismic data show that these troughs were previously part of one large depositional basin in the Devonian, the depocentre of which lay east of a north-trending hingeline. Structural features and Devonian depositional limits and patterns have been modified from earlier interpretations as a result of the new seismic coverage. The maximum sediment thickness is re-interpreted to be 8500 m, considerably thicker than previous interpretation.recognised. The first one, a diachronous Middle Devonian unconformity, is the most extensive, and reflects the mobility of the basement during the basin's early history. The second unconformity within the Late Devonian Buckabie Formation reveals that there were two phases of deformation of the basin sediments.The geochemical results reported in this study show that most of the Adavale Basin sediments have very low concentrations of organic carbon and hydrocarbon fractions. Maturity profiles indicate that the best source rocks of the basin are now in the mature stage for hydrocarbon generation. However, at Gilmore and in the Cooladdi Trough, they have reached the dry gas stage. The maturity data provide additional evidence for the marked break in deposition and significant erosion during the Middle Devonian recognised on the seismic records, and extend the limits of this sedimentary break into the northern part of the main depression.Hydrocarbon potential of the Adavale Basin is fair to poor. In the eastern part of the basin, where most of the data are available, the prospects are better for gas than oil. Oil prospectivity may be improved in any exinite-rich areas that exist farther west, where palaeo-temperatures were lower.

Implications of source overcharge for prospect assessment

2015 ◽  
Vol 3 (2) ◽  
pp. T93-T107
Author(s):  
Richard S. Bishop
Keyword(s):  
Oil And Gas ◽  
Tectonic Setting ◽  
Field Studies ◽  
Fundamental Aspect ◽  
Statistical Distributions ◽  
Free Gas ◽  
Wide Range ◽  
Fault Leakage ◽  
Discrete Values ◽  
Gas Leaks

A fundamental aspect of prospect evaluation is whether the trap volume or the charge volume limits the volume of trapped hydrocarbons. Traps filled to a leak point are full traps, although I rarely describe them as such. I commonly say “full to spill” but rarely do I hear “full to a leak point.” Why not? A summary of literature from fault leakage, seeps, field studies, and theoretical source-yield calculations illustrates the implication that source overcharge (i.e., the charge exceeding the trap volume) occurs in basins that vary widely in age and tectonic setting. Perhaps surprisingly, this is true for oil and gas fields and for a wide range of source rock quality from rich to lean. The most obvious implication from source overcharge is that the volume of trapped hydrocarbons is limited by the absolute volume of the trap. Less obvious is the recognition that if oil and free gas are available to a trap, gas will displace the oil. Thus, if there are no gas leaks, the trap will contain only gas. If there is preferential leakage of gas, then the trap may contain a gas cap and an oil leg. Furthermore, the occurrence of oils saturated with gas likely indicates selective leakage of free gas. Hydrocarbon contacts (whether oil-water, gas-oil, or gas-water) are interpreted to define the leak or spill point or seal capacity. Thus, instead of using continuous statistical distributions to describe all elements of traps, some elements such as area are more appropriately described as discrete values and a full assessment may be a combination of discrete plus continuous statistical distributions. Overcharge may also lead to different interpretations of risk. Interpreting the trap volume, particularly with leak points, leads to the notion that risk evaluation might consider the number and quality of potential leak points.

Three-dimensional Magnetotelluric Crustal Model of High Agri Valley seismic area to identify and to quantify the resistivity variation in depth

2020 ◽  
Author(s):  
Anna Eliana Pastoressa ◽  
Marianna Balasco ◽  
Juanjo Ledo ◽  
Pilar Queralt ◽  
Gerardo Romano ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Regularization Parameter ◽  
Three Dimensional ◽  
Correct Choice ◽  
Structural Features ◽  
Fault System ◽  
Gas Field ◽  
Period Range ◽  
Stress Regime ◽  
Resistivity Variation

<p>The High Agri Valley (HAV) is an axial zone of the Southern Apennines thrust belt chain with a strong seismogenic potential as shown by different stress indicators and space geodesy data that suggest an NE-SW extensional stress regime still active. Moreover, the HAV hosts the Europe’s largest onshore oil and gas field, which give it further strategic importance.</p><p>There is a certain ambiguity concern the causative fault of the large event (M=7.0) occurred in 1857 in Agri Valley, although two well-documented fault systems are recognised as potentially seismogenic: the Monti della Maddalena Fault System (MMFS) and the Eastern Agri Fault System (EAFS).</p><p>With the aim to bring new information on identification and characterization of the principal structures, on the fluids distribution and their possible relationship with the developed of kinematics in upper fragile crust, several multiscale and multidisciplinary surveys are currently running in the HAV. Here we present the first results of a 3D Magnetotelluric (MT) investigation composed of 58 MT soundings in the period range [10<sup>-2</sup> Hz, 10<sup>3</sup> Hz] which cover an area of approximately of 15 km x 30 km. All the 3D results were obtained by using the 3D inversion conde ModEM: Modular EM Inversion Software.</p><p>The work carried out so far has been mainly focused on the definition of the best mesh to adopt, both in terms of cell size and orientation, and on the correct choice of the inversion parameters: resistivity of the starting model, smoothing model parameter, minimum error floor attributed to the data, regularization parameter (trade-off).</p><p>The 3D MT preliminary model obtained shows a good agreement with 2D models previously realized using a part of the same dataset and defines the main geo-structural features of the HAV.</p><p>The resistivity variations in HAV subsurface will be jointly interpreted with accurate seismic data collected by seismic broadband network INSIEME (composed by 8 stations distributed throughout the Agri Valley) and other available geophysical and geological data.</p><p>The interconnection between the conductivity and seismicity information will be useful to implement the knowledge on the role that fluids play in fault zones and in earthquake processes. </p>

scholarly journals Application of Radar Imagery to Tectonic, Structural and Geological Studies in Afikpo Basin, Southeastern Benue Trough, Nigeria

2019 ◽  
pp. 1-9
Author(s):  
Minapuye Isaac Odigi ◽  
Prince Suka Momta
Keyword(s):  
Tectonic Setting ◽  
Field Work ◽  
Structural Features ◽  
Drainage Pattern ◽  
Ground Field ◽  
Transform Faults ◽  
Benue Trough ◽  
Lithostratigraphic Units ◽  
Geological Information ◽  
Radar Imagery

Radar imagery was used to identify geological features and the production of geological maps of the Afikpo basin. The essence of this study was to delineate significant geological and geomorphological features that have not been imaged by the traditional ground field mapping. The application of Radar imagery technique will be relevant to the discovery of subsurface structures that will aid the accumulation or concentration of certain economic minerals or natural resources. It will enhance the identification of significant geological information such as lineaments, geologic structures, drainages, etc, that will serve as a guide to the actual ground field work investigation. Results from radar imageries revealed drainage pattern, major geomorphological units, mega lithostratigraphic units, lineaments and structures. The geology of Afikpo basin consist of Cretaceous, Tertiary and Quaternary rocks are recognizable; the highly deformed Cretaceous rocks are characterized by regional lineaments. Some of the rivers are aligned along the regional lineaments. The NW-SE and NE-SW lineaments truncate one another, suggesting different ages for the lineament groups. A few sinistral tensional movements occur in the eastern sector of the basin.  The major folds in the Afikpo basin have NE-SW and NW-SE trends, and occur as anticlines and synclines. The basement structuring and basin framework suggest a tectonic setting in the southeastern Benue Trough resulting from the Early Cretaceous opening of the South Atlantic Ocean and interpolate movement in Africa. From the evidence currently available we may conclude that the post Santonian Afikpo basin falls within the transtenstional basin categories associated with transform faults. The regional tectonics interpreted from the radar imageries are likely hydrocarbon related structural features.

scholarly journals IMPROVING THE EFFICIENCY OF THE FUNCTIONING OF GAS PIPELINES, TAKING INTO ACCOUNT THE STRUCTURAL FEATURES OF GAS FLOWS

2021 ◽  
Vol 447 (3) ◽  
pp. 34-39
Author(s):  
Elman Kh. Iskandarov
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Structural Changes ◽  
Oil And Gas ◽  
Structural Features ◽  
Transportation Systems ◽  
Gas Condensate ◽  
Gas Flows ◽  
Gas Pipelines ◽  
Processing Depth

The multi-phase and different composition of gas flows during the development of offshore oil and gas-condensate fields leads to high costs of energy in the system of in-field storage and transportation of well products. The analysis of the existing storage and transportation systems of gas-condensate mixtures shows that the geophysical nature and complexity of the internal structure of the transported fluids must be taken into account when choosing the mode parameters and calculation schemes of the pipelines. High-speed gas lines can be operated in a so-called "dry" mode, in which the liquid is carried along with the gas, the pipeline profile is relatively straight, without ups and downs. In this case, the formation of so-called "stagnant zones" in the pipeline is excluded. However, if the processing depth of the gas does not allow it to be transported in a single-phase state, then the condensing gas factor manifests itself. The hydraulic characteristics of vertical ups and downs on offshore pipelines are complicated, and pipelines are often filled with water and condensate. As a result, the pressure in the pipeline increases and the location of the collection point for condensing gases away from the production site can cause major problems. If we characterize oil and gas-condensate flows as a dynamic system in which alternating structural changes take place, the question of whether these systems are fractal is of great scientific interest. Based on the change in the fractal value, it is possible to diagnose structural changes during the transportation of various systems, including condensing gases in the pipelines. In this article the modes of change of basic parameters of a gas flow (pressure, flow rate and temperature) on various lines of a gas pipeline for the purpose of the producing of diagnostic criterion for revealing of liquid inclusions as a part of transported gas are investigated in this article. It is established, that in the presence of liquid inclusions at movement of gas flows there are the structural changes peculiar to fluid systems, systems which can be identified by variations of fractal dimensions of flowcharacteristics. Studies have shown that the study of the dynamics of structural changes in gas flows can play a role in diagnosing the formation of liquid phase embryos in gas pipelines. For this purpose, diagnostics for the movement of gas streams accompanied by liquid deposits in the pipelines has been proposed.

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