Kinematic linkage between minibasin welds and extreme overpressure in the deepwater Gulf of Mexico

2014 ◽  
Vol 2 (1) ◽  
pp. SB69-SB77 ◽  
Author(s):  
Niven Shumaker ◽  
Daniel Haymond ◽  
Joe Martin
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Velocity ◽  
Large Degree ◽  
Data Sets ◽  
Seismic Velocities ◽  
Burial History ◽  
Well Control ◽  
Deep Blue ◽  
Exploration Well ◽  
Primary Section

A geopressure interpretation technique known as the seismic velocity method is a common workflow in which shale compaction functions are characterized at offset control wells, matched to interval seismic velocities, and then used to predictively calculate geopressure away from well control. The seismic velocity method is used to interpret the expected geopressure profile at the Deep Blue subsalt exploration well in Green Canyon 723 in the deep water Gulf of Mexico. The Deep Blue prospect is distinct from other prospects in the play fairway in that the prospective section is overlain by a salt withdrawal minibasin, whereas the offsetting fields are positioned either along the flanks of minibasins or under a thick allochthonous salt canopy. Predrill geopressure interpretations using numerous tomographic imaging velocity data sets shows a large degree of consistency with the magnitude of geopressure encountered in offsetting supra salt and subsalt fields. Results from the Deep Blue 1 exploration well indicate the predrill geopressure interpretation from interval seismic velocities failed to anticipate the extreme degree overpressure encountered in the subsalt section of the well due to poor deep velocity resolution and an “unloaded” compaction signature. The magnitude of overpressure in the primary section is attributed to the emplacement of an unconformable halokinetic sequence over the primary subsalt basin. An interpretive paradigm is described in which the Deep Blue pressure cell is created through two halokinetic episodes: (1) rapid progradation of a salt canopy followed by (2) subsequent salt withdrawal and emplacement of an overlying minibasin. The linkage between halokinetic sequences, burial history, and the development of overpressure can be used to predictively characterize subsalt geopressure environments.

Integration of seismic and gravity data — A case study from the western Gulf of Mexico

2015 ◽  
Vol 3 (4) ◽  
pp. SAC99-SAC106 ◽  
Author(s):  
Irina Filina ◽  
Nicholas Delebo ◽  
Gopal Mohapatra ◽  
Clayton Coble ◽  
Gary Harris ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Gravity Field ◽  
Gravity Model ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Public Domain ◽  
Gravity Modeling ◽  
Data Sets ◽  
Gardner Equation ◽  
Well Data

A 3D gravity model was developed in the western Gulf of Mexico in the East Breaks and Alaminos Canyon protraction areas. This model integrated 3D seismic, gravity, and well data; it was constructed in support of a proprietary seismic reprocessing project and was updated iteratively with seismic. The gravity model was built from seismic horizons of the bathymetry, salt layers, and the acoustic basement; however, the latter was only possible to map in seismic data during the latest iterations. In addition, a deep layer representing the Moho boundary was derived from gravity and constrained by public-domain refraction data. A 3D density distribution was derived from the seismic velocity volume using a modified Gardner equation. The modification comprised imposing a depth dependency on the Gardner coefficient, which is constant in the classic Gardner equation. The modified coefficient was derived from well data in the study area and public-domain velocity-density data sets. The forward-calculated gravity response of the composed density model was then compared with the observed gravity field, and the mismatch was analyzed jointly by a seismic interpreter and a gravity modeler. Adjustments were then made to the gravity model to ensure that the resultant salt model was geologically reasonable and supported by gravity, seismic, and well data sets. The output of the gravity modeling was subsequently applied to the next phase of seismic processing. Overall, this integration resulted in a more robust salt model, which has led to significant improvements in subsalt seismic imaging. The analysis of the regional trend in the observed gravity field suggested that a stretched continental crust underlay our seismic reprocessing area, with an oceanic-continental transition zone located to the southeast of our reprocessing region.

scholarly journals Deriving seismic velocities on the micro-scale from c-axis orientations in ice cores

2018 ◽  
Author(s):  
Johanna Kerch ◽  
Anja Diez ◽  
Ilka Weikusat ◽  
Olaf Eisen
Keyword(s):  
Seismic Anisotropy ◽  
Seismic Velocity ◽  
Ice Core ◽  
Ice Cores ◽  
Core Sample ◽  
Data Sets ◽  
Seismic Velocities ◽  
Crystal Anisotropy ◽  
Orientation Distributions ◽  
Ice Sheet Dynamics

Abstract. One of the greatest challenges in glaciology, with respect to sea level predictions, is the ability to gain information on bulk ice anisotropy in ice sheets and glaciers, which is urgently needed to improve our understanding of ice-sheet dynamics. Therefore, we investigate the effect of crystal anisotropy on seismic velocities in a glacier. We revisit the framework which is based on fabric eigenvalues to derive approximate seismic velocities by exploiting the assumed symmetry. In contrast to previous studies, we calculate the seismic velocities using the exact c-axis angles describing the orientations of the crystal ensemble in an ice-core sample. We apply this approach to fabric data sets from an Alpine (KCC) and a polar (EDML) ice core. The results allow a quantitative evaluation of the earlier approximative eigenvalue framework. Additionally, our findings highlight the variation in seismic velocity as a function of the horizontal azimuth of the seismic plane, which can be significant in case of non-symmetric orientation distributions and results in a strong azimuth-dependent shear-wave splitting. For the first time, we assess the change in seismic anisotropy that can be expected on a short spatial scale in a glacier due to a strong variability in crystal-orientation fabric. Our investigation of seismic anisotropy based on ice-core data contributes to advancing the interpretation of seismic data, with respect to extracting bulk information about crystal anisotropy without having to drill an ice core and with special regard to future applications employing ultrasonic sounding.

scholarly journals Physics-Based Relationship for Pore Pressure and Vertical Stress Monitoring Using Seismic Velocity Variations

2021 ◽  
Vol 13 (14) ◽  
pp. 2684
Author(s):  
Eldert Fokker ◽  
Elmer Ruigrok ◽  
Rhys Hawkins ◽  
Jeannot Trampert
Keyword(s):  
Pore Pressure ◽  
Seismic Velocity ◽  
Pressure Head ◽  
Groundwater Table ◽  
Surface Velocity ◽  
Seismic Velocities ◽  
Stress Monitoring ◽  
Near Surface ◽  
Velocity Variations ◽  
Velocity Changes

Previous studies examining the relationship between the groundwater table and seismic velocities have been guided by empirical relationships only. Here, we develop a physics-based model relating fluctuations in groundwater table and pore pressure with seismic velocity variations through changes in effective stress. This model justifies the use of seismic velocity variations for monitoring of the pore pressure. Using a subset of the Groningen seismic network, near-surface velocity changes are estimated over a four-year period, using passive image interferometry. The same velocity changes are predicted by applying the newly derived theory to pressure-head recordings. It is demonstrated that the theory provides a close match of the observed seismic velocity changes.

scholarly journals Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: A case study for the COSC-1 borehole, Sweden

2020 ◽  
Author(s):  
Felix Kästner ◽  
Simona Pierdominici ◽  
Judith Elger ◽  
Christian Berndt ◽  
Alba Zappone ◽  
...  
Keyword(s):  
Seismic Anisotropy ◽  
Seismic Velocity ◽  
Metamorphic Rocks ◽  
Seismic Velocities ◽  
Mafic Rocks ◽  
Seismic Properties ◽  
The Core ◽  
Nappe Complex ◽  
Thrust Zone ◽  
Mountain Belts

<p>Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply-eroded orogens like the Scandinavian Caledonides allow to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications for a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can help to constrain the origin of this reflectivity. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The core and downhole velocities deviate by up to 2 km/s. However, velocities of mafic rocks are generally in close agreement. Seismic anisotropy increases from about 5 to 26 % at depth, indicating a transition from gneissic to schistose foliation. Differences in the core and downhole velocities are most likely the result of microcracks due to depressurization of the cores. Thus, seismic velocity can help to identify mafic rocks on different scales whereas the velocity signature of other lithologies is obscured in core-derived velocities. Metamorphic foliation on the other hand has a clear expression in seismic anisotropy. To further constrain the effects of mineral composition, microstructure and deformation on the measured seismic anisotropy, we conducted additional microscopic investigations on selected core samples. These analyses using electron-based microscopy and X-ray powder diffractometry indicate that the anisotropy is strongest for mica schists followed by amphibole-rich units. This also emphasizes that seismic velocity and anisotropy are of complementary importance to better distinguish the present lithological units. Our results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.</p>

Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment) – II. Sardinia’s margin

2015 ◽  
Vol 186 (4-5) ◽  
pp. 331-351 ◽  
Author(s):  
Alexandra Afilhado ◽  
Maryline Moulin ◽  
Daniel Aslanian ◽  
Philippe Schnürle ◽  
Frauke Klingelhoefer ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Passive Margin ◽  
Data Sets ◽  
Wide Angle ◽  
Seismic Velocities ◽  
The West ◽  
Reflection Seismic ◽  
Gulf Of Lion ◽  
Deep Crustal Structure ◽  
Domain Iii

Abstract Geophysical data acquired on the conjugate margins system of the Gulf of Lion and West Sardinia (GLWS) is unique in its ability to address fundamental questions about rifting (i.e. crustal thinning, the nature of the continent-ocean transition zone, the style of rifting and subsequent evolution, and the connection between deep and surface processes). While the Gulf of Lion (GoL) was the site of several deep seismic experiments, which occurred before the SARDINIA Experiment (ESP and ECORS Experiments in 1981 and 1988 respectively), the crustal structure of the West Sardinia margin remains unknown. This paper describes the first modeling of wide-angle and near-vertical reflection multi-channel seismic (MCS) profiles crossing the West Sardinia margin, in the Mediterranean Sea. The profiles were acquired, together with the exact conjugate of the profiles crossing the GoL, during the SARDINIA experiment in December 2006 with the French R/V L’Atalante. Forward wide-angle modeling of both data sets (wide-angle and multi-channel seismic) confirms that the margin is characterized by three distinct domains following the onshore unthinned, 26 km-thick continental crust : Domain V, where the crust thins from ~26 to 6 km in a width of about 75 km; Domain IV where the basement is characterized by high velocity gradients and lower crustal seismic velocities from 6.8 to 7.25 km/s, which are atypical for either crustal or upper mantle material, and Domain III composed of “atypical” oceanic crust. The structure observed on the West Sardinian margin presents a distribution of seismic velocities that is symmetrical with those observed on the Gulf of Lion’s side, except for the dimension of each domain and with respect to the initiation of seafloor spreading. This result does not support the hypothesis of simple shear mechanism operating along a lithospheric detachment during the formation of the Liguro-Provencal basin.

Quaternary sodic and potassic intraplate volcanism in northeast China controlled by the underlying heterogeneous lithospheric structures

Geology ◽  
2021 ◽  
Author(s):  
Xingli Fan ◽  
Qi-Fu Chen ◽  
Yinshuang Ai ◽  
Ling Chen ◽  
Mingming Jiang ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Northeast China ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Subcontinental Lithospheric Mantle ◽  
Seismic Velocities ◽  
S Wave ◽  
Crust And Upper Mantle ◽  
Potassic Volcanism

The origin and mantle dynamics of the Quaternary intraplate sodic and potassic volcanism in northeast China have long been intensely debated. We present a high-resolution, three-dimensional (3-D) crust and upper-mantle S-wave velocity (Vs) model of northeast China by combining ambient noise and earthquake two-plane wave tomography based on unprecedented regional dense seismic arrays. Our seismic images highlight a strong correlation between the basalt geochemistry and upper-mantle seismic velocity structure: Sodic volcanoes are all characterized by prominent low seismic velocities in the uppermost mantle, while potassic volcanoes still possess a normal but thin upper-mantle “lid” depicted by high seismic velocities. Combined with previous petrological and geochemical research findings, we propose that the rarely erupted Quaternary potassic volcanism in northeast China results from the interaction between asthenospheric low-degree melts and the overlying subcontinental lithospheric mantle. In contrast, the more widespread Quaternary sodic volcanism in this region is predominantly sourced from the upwelling asthenosphere without significant overprinting from the subcontinental lithospheric mantle.

Numerical Insights into the Formation and Stability of Cratons

2021 ◽  
Author(s):  
Charitra Jain ◽  
Antoine Rozel ◽  
Emily Chin ◽  
Jeroen van Hunen
Keyword(s):  
Continental Crust ◽  
Seismic Velocity ◽  
Potential Temperature ◽  
Crustal Material ◽  
Spinel Lherzolite ◽  
Seismic Velocities ◽  
Geophysical Research ◽  
Thermal Buoyancy ◽  
Depleted Mantle ◽  
Cratonic Mantle

<div>Geophysical, geochemical, and geological investigations have attributed the stable behaviour of Earth's continents to the presence of strong and viscous cratons underlying the continental crust. The cratons are underlain by thick and cold mantle keels, which are composed of melt-depleted and low density peridotite residues [1]. Progressive melt extraction increases the magnesium number Mg# in the residual peridotite, thereby making the roots of cratons chemically buoyant [2, 3] and counteracting their negative thermal buoyancy. Recent global models have shown the production of Archean continental crust by two-step mantle differentiation, however this primordial crust gets recycled and no stable continents form [4]. This points to the missing ingredient of cratonic lithosphere in these models, which could act as a stable basement for the crustal material to accumulate on and may also help with the transition of global regime from "vertical tectonics'' to "horizontal tectonics''. Based on the bulk FeO and MgO content of the residual peridotites, it has been proposed that cratonic mantle formed by hot shallow melting with mantle potential temperature, which was higher by 200-300 °C than present-day [5]. We introduce Fe-Mg partitioning between mantle peridotite and melt to track the Mg# variation through melting, and parametrise craton formation using the corresponding P-T formation conditions. Using self-consistent global convection models, we show the dynamic formation of cratons as a result of naturally occurring lateral compression and thickening of the lithosphere, which has been suggested by geochemical and petrological data. To allow for the material to compact and thicken, but prevent it from collapsing under its own weight, a combination of lithospheric strength, plastic yielding, dehydration strengthening, and depletion-induced density reduction of the depleted mantle material is necessary.</div><div> </div><div> [1] Boyd, F. R. High-and low-temperature garnet peridotite xenoliths and their possible relation to the lithosphere- asthenosphere boundary beneath Africa. In Nixon, P. H. (ed.) <em>Mantle Xenolith</em>, 403–412 (John Wiley & Sons Ltd., 1987).</div><div>[2] Jordan, T. H. Mineralogies, densities and seismic velocities of garnet lherzolites and their geophysical implications. In <em>The Mantle Sample: Inclusion in Kimberlites and Other Volcanics</em>, 1–14 (American Geophysical Union, Washington, D. C., 1979).</div><div>[3] Schutt, D. L. & Lesher, C. E. Effects of melt depletion on the density and seismic velocity of garnet and spinel lherzolite. <em>Journal of Geophysical Research </em><strong>111</strong> (2006).</div><div>[4] Jain, C., Rozel, A. B., Tackley, P. J., Sanan, P. & Gerya, T. V. Growing primordial continental crust self-consistently in global mantle convection models. <em>Gondwana Research</em> <strong>73</strong>, 96–122 (2019).</div><div>[5] Lee, C.-T. A. & Chin, E. J. Calculating melting temperatures and pressures of peridotite protoliths: Implications for the origin of cratonic mantle. <em>Earth and Planetary Science Letters</em> <strong>403</strong>, 273–286 (2014)</div>

scholarly journals The Elastic Properties of β-Mg2SiO4 Containing 0.73 wt.% of H2O to 10 GPa and 600 K by Ultrasonic Interferometry with Synchrotron X-Radiation

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 209
Author(s):  
Gabriel D. Gwanmesia ◽  
Matthew L. Whitaker ◽  
Lidong Dai ◽  
Alwin James ◽  
Haiyan Chen ◽  
...  
Keyword(s):  
Finite Strain ◽  
Seismic Velocity ◽  
Strain Analysis ◽  
Data Sets ◽  
Third Order ◽  
Data Set ◽  
Earth’S Mantle ◽  
Ultrasonic Interferometry ◽  
Linear Fit ◽  
Derivatives Of

We measured the elastic velocities of a synthetic polycrystalline β-Mg2SiO4 containing 0.73 wt.% H2O to 10 GPa and 600 K using ultrasonic interferometry combined with synchrotron X-radiation. Third-order Eulerian finite strain analysis of the high P and T data set yielded Kso = 161.5(2) GPa, Go = 101.6(1) GPa, and (∂Ks/∂P)T = 4.84(4), (∂G/∂P)T = 1.68(2) indistinguishable from Kso = 161.1(3) GPa, Go = 101.4(1) GPa, and (∂Ks/∂P)T = 4.93(4), (∂G/∂P)T = 1.73(2) from the linear fit. The hydration of the wadsleyite by 0.73 wt.% decreases Ks and G moduli by 5.3% and 8.6%, respectively, but no measurable effect was noted for (∂Ks/∂P)T and (∂G/∂P)T. The temperature derivatives of the Ks and G moduli from the finite strain analysis (∂KS/∂T)P = −0.013(2) GPaK−1, (∂G/∂T)P = −0.015(0.4) GPaK−1, and the linear fit (∂KS/∂T)P = −0.015(1) GPaK−1, (∂G/∂T)P = −0.016(1) GPaK−1 are in agreement, and both data sets indicating the |(∂G/∂T)P| to be greater than |(∂KS/∂T)P|. Calculations yield ∆Vp(α-β) = 9.88% and ∆VS(α-β) = 8.70% for the hydrous β-Mg2SiO4 and hydrous α-Mg2SiO4, implying 46–52% olivine volume content in the Earth’s mantle to satisfy the seismic velocity contrast ∆Vs = ∆VP = 4.6% at the 410 km depth.

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