The influence of elastic anisotropy on seismic wave propagation is often neglected for the sake of simplicity. However, ignoring anisotropy may lead to significant errors in the processing of seismic data and ultimately in a poor image of the subsurface. This is especially true in wide-aperture Vertical Seismic Profiles where waves travel both vertically and horizontally. Anisotropy has been neglected in wavefront construction methods of seismic ray-tracing until Gibson (2000), who showed they are powerful tools to simulate seismic wave propagation in three-dimensional anisotropic subsurface models. The code is currently under development using a C++ object oriented programming approach because it provides high flexibility in the design of new components and facilitates debugging and maintenance of a complex algorithm. So far, the code was used to simulate propagation in homogeneous or simple heterogeneous anisotropic velocity models mainly designed for testing purposes. In particular, it has never been applied to simulate a field dataset. We propose here an analytical method involving little algebra and that allows the design of realistic heterogeneous anisotropic models using the C++ object oriented programming approach. The new model class can model smooth multi-layered subsurface with gradients or models with many dip variations. It has been used to model first arrival times of a wide-aperture VSP dataset from the Gulf of Mexico to estimate the amount of anisotropy. The proposed velocity model is transversely isotropic. The anisotropy is constant throughout the model and is defined via Thomsen’s parameters. Values in the final model are e = 0.055 and d = -0.115. The model is compatible with the a priori knowledge of the local geology and reduces the RMS average time difference between measured and computed travel times by 51% in comparison to the initial isotropic model. These values are realistic and are similar to other measurements of anisotropy in the Gulf of Mexico.

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The Shattuck Sandstone Member of the Guadalupian age Queen Formation was deposited in back-reef environments on a carbonate platform of the Northwest Shelf (Permian Basin, New Mexico, USA) during a lowstand of sea level. At Mesa Queen Field, the Shattuck Sandstone is a sheet-like sand body that averages 30 ft (9.1 m) in thickness. The Shattuck Sandstone includes deposits of four major siliciclastic environments: (1) fluvial sandflats, (2) eolian sand sheets, (3) inland sabkhas, and (4) marine-reworked eolian sands. Fluvial sandflat deposits are further subdivided into sheetflood, wadi plain, and river-mouth deposits. Dolomites, evaporites, and siliciclastics that formed in adjacent coastal sabkha and lagoonal environments bound the Shattuck Sandstone from above and below.

The Shattuck Sandstone is moderately- to well-sorted, very fine-grained subarkose, with a mean grain size of 98 mm (3.55f). Eolian sand sheet, wadi plain, and marine-reworked eolian facies comprise the productive reservoir intervals. Reservoir quality reflects intragranular and intergranular secondary porosity formed by partial dissolution of labile feldspar grains, and pore-filling anhydrite and dolomite cements.

Vertical successions and regional facies patterns support previous interpretations that these deposits formed during a sea-level lowstand and early stages of subsequent transgression. Facies patterns across the shelf indicate fluvial sandflats prograded over coastal and inland sabkhas, and eolian sand deposition became more common during a sea-level fall and lowstand. During subsequent transgression, eolian sediments in the upper portion of the Shattuck Sandstone were reworked as coastal and lagoon environments became reestablished on the inner carbonate platform.

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New, rapid techniques to quantify the different pools of soil organic matter (SOM) are needed to improve our understanding of the dynamics and spatio-temporal variability of SOM in terrestrial ecosystems. In this study, total organic carbon (TOC) and oxidizable organic carbon (OCWB) fraction were calibrated and predicted by mid- and near-DRIFT spectroscopy in combination with partial least squares (PLS) regression method. PLS regression is a multivariate calibration method that can decompose spectral data (X) and soil property data (Y) into a new smaller set of latent variables and their scores that best describe all the variance in the data. Oxidizable organic carbon content was measured by a modified Walkley-Black method, and total organic carbon was measured by the carbon analyzer.

The floodplain and Blackland Prairie soils in Texas were used for prediction of TOC and OCWB using mid- and near-DRIFT spectroscopy. Floodplain soil is mainly composed of quartz and kaolinite, whereas Blackland Prairie soils contain high concentrations of smectitic clays and low to high concentrations of carbonate minerals. The total organic carbon of 68 soil samples from two Texas sites varied between 0.19 and 4.36 wt.% C, and the oxidizable organic carbon of 26 samples from floodplain soils was in the range of 0.05 to 1.33 wt.% C.

TOC and OCWB of soil were successfully calibrated and predicted by the PLS regression method using mid- and near-DRIFT spectroscopy. The correlation using mid-IR spectra for TOC (r = 0.96, RMSEV = 0.32 for calibration; r = 0.93, RMSEP = 0.44 for prediction) was about the same as the near-IR result (r = 0.95, RMSEV = 0.37; r = 0.93, RMSEP = 0.42). Therefore, we can also use mid-infrared region for quantification of total organic carbon in soils. The PLS1 regression model (r = 0.92) for prediction of OCWB using mid-IR spectra was more accurate than the PLS2 regression model (r = 0.90). PLS models showed better correlation with spectral data than the univariate least square regression method(r = 0.83) with TOC measured by the carbon analyzer.

This study shows that the partial least squares (PLS1) method using mid-and near-IR spectra of neat soil samples can be used to predict both total organic carbon and oxidizable carbon fraction as a fast and routine quantitative method.

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During the Late Pliocene to Middle Pleistocene Ages, sediments of the study area were deposited in the intra-slope salt withdrawal basin where sand-prone sediments deposited as turbidite lobes and channel fills are the main reservoirs of the Northern Gulf of Mexico. The main purpose of this study was to identify and characterize these sand-prone sediments. Sequence stratigraphic analysis of well logs, biostratigraphic data, and 3-D seismic data provided a chronostratigraphic framework of the study area, within which seismic facies analysis was carried out. Each sequence was subdivided into separate seismic bodies characterized by specific amplitude, coherence of reflectors, and shape of reflectors. The descriptions of each seismic facies combined with well logs were compared with turbidite facies models to infer their geological information. Five turbidite elements were identified: depositional channel fills and overbank deposits, erosional channel fills, turbidite lobes, mud turbidite fills and sheets and hemipelagic and pelagic drapes. Depositional channel fills are usually deposited in lower parts of interpreted sequences, surrounded by shale-prone overbank deposits. The lateral variation of these turbidite elements was revealed by horizon slices, in which depositional channels are generally trending NE-SW or NNE-SSW with elongated sinuous forms. Well logs indicate that depositional channel fills usually consist of bell or cylinder type sand-prone sediments. Turbidite lobe was found only in the 1.1-0.8 Ma sequence, in which it laps out onto the underlying sequence boundary and shows high-amplitude and a high-continuity mound shape. This facies is interpreted as sand-prone facies, but wells available penetrated only the marginal parts of this facies and showed poor reservoir qualities. Horizon slices could partly reveal its lapout boundary due to the limitation of vertical seismic resolution. Mud turbidite fills and sheets are the most dominant turbidite facies, which usually occurred in the upper parts of sequences and overlain by hemipelagic and pelagic drapes. Hemipelagic and pelagic drapes were deposited very widely, wrapping down the previous topography with consistent thickness throughout the basin. Erosional channel was observed only in the 0.8-0.7 Ma sequence where it cut into the underlying sequence and was filled by shale-prone sediments. Depositional channel fills and turbidite lobes are the main reservoir facies in the study area. Seismic facies analysis using vertical seismic sections and horizon slices combined with lithology data made it possible to identify and systematically describe these sand prone turbidite elements in intra-slope salt withdrawal basin.

Delamination of the lower crust and lithospheric mantle has occurred in several orogens during convergence, most notably the Alps and Pyrenees. The factors responsible for initiating the delamination are not clear. Some workers suggest this process to be mechanically similar to tectonic wedging and triangle-zone development, well known at the scale of kilometers in fold and thrust belts.

In a search for controlling factors, >35 convergent orogens explored by deep geophysical techniques were examined. No correlation between crustal composition and a propensity for delamination is evident. Delamination of subducting passive margins is more common than tectonically and/or volcanically active over-riding margins.

Estimates of lithospheric density show that the lithospheric mantle of a cool passive margin may contain greater net negatively buoyant mass than a warmer active margin. The top of the lower lithospheric layer with the greatest net negatively buoyant mass is aligned with a weak zone in the lithosphere near the Moho. A greater net negatively buoyant mass indicates a propensity for delamination to initiate in a passive margin versus an active margin during a subsequent collisional event.

For delamination to initiate above the Moho, the lower crust must be subducted or depressed to eclogite grade conditions. Transformation of the mafic lower crust to mafic eclogite also generates a lower lithospheric layer containing net negatively buoyant mass aligned with a weak zone in the lithosphere.

Scaled physical models with a model continental crust weakly coupled to a lithospheric mantle containing net negatively buoyant mass delaminate during shortening. In contrast, weakly coupled models containing net positively buoyant mass within the model lithospheric mantle exhibit no tendency for delamination or wedging, despite a weak horizon at the base of the model crust. This contrast in behavior indicates that the mass distribution within the model lithosphere is a primary control on the process of syn-collisional delamination.

Syn-collisional delamination is likely to occur in response to an increase in the lateral tectonic stress on a weak horizon already stressed by net negatively buoyant mass in the lower lithosphere. Thus, delamination and tectonic wedging is not a similar mechanical process at all scales.

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Mixtures of bacterial and thermogenic methane are found both at vents at the seafloor and in reservoirs in the deep subsurface of the Gulf of Mexico continental slope. The C1-C5 gas that most recently charged reservoirs of Jolliet (GC 184), Genesis (GC 160/161) and Petronius (VK 786) fields is estimated to include 17%-28%, 31%-51%, 31%-49% bacterial methane, respectively.

Geochemical assessment of the reservoir gas in the fields show that the gas may be the product of thermal cracking of Upper Jurassic crude oil before final migration to the reservoirs. The gas from three different fields is of similar thermal maturity levels. In contrast to oil in reservoirs in the fields, which shows biodegradation effects, the C1-C5 reservoir gas is unaltered by biodegradation. Late gas migration may have occurred at or near present burial depth and flushed the reservoir system of previously biodegraded hydrocarbon gas to include any previous bacterial methane.

Molecular and isotopic properties of reservoir gas and oil suggest that bacterial methane mixed with thermogenic hydrocarbon gas before entering the reservoirs. Thus the source of the bacterial methane is logically deeper than the present depth (>~4 km) and temperatures of the reservoirs. High sedimentation rate and low geothermal gradient may offer conditions favorable for generation and preservation of bacterial methane in deep subsurface petroleum system of the Gulf slope. Bacterial methane dispersed across the large drainage areas of the deep subsurface petroleum system may have been swept by migrating fluids at >4 km, and then charged both vents (GC 185, GC 233 and GC 286) at the seafloor and reservoirs in the deep subsurface. The volume of bacterial methane from geologically significant depth in rapidly subsiding basins may be underestimated.

The late Permian Queen Formation (115 m thick) is a succession of mixed clastics, carbonates and evaporites deposited in the northeastern margin of Central Basin Platform of the Permian Basin, west Texas, USA. Depositional facies, stacking patterns of cyclic facies associations and statistical correlation of rock property variations define geologic controls on reservoir rock properties. Textural, compositional, petrophysical and diagenetic variations within lithofacies exhibit systematic changes with stratigraphic position, which can be related to base level changes that were controlled by high-frequency, low-amplitude, sea level fluctuations during a greenhouse period.

Ten lithofacies record variations in clastic input, shallow marine carbonate production, and evaporate precipitation in sabhkas and salinas. Four different types of lithofacies associations define: (1) transgressive deltaic deposits; (2) upward-shallowing evaporite and carbonate tidal-flat deposits; (3) transgressive beach ridge and sand flat deposits; and (4) upward-shallowing evaporite salina-sabhka deposits. Stacking patterns of lithofacies associations define sixteen depositional cycles that can be grouped into eight cycle sets. Cycle sets in turn are grouped to define two high-frequency sequences. Sequence 1 progresses from fluvial to carbonate tidal flat cycles. Sequence 2 consists of salina-dominated upward-shoaling cycles. Lateral continuity of cycles indicates restricted sedimentation on low-accommodation inner platform areas updip of prograding highstand platform-margin carbonate buildups, and a long-term trend of accommodation decrease. The Queen Formation contains two reservoir types; (1) siliciclastic reservoirs capped by evaporites and (2) layer-cake carbonate reservoirs. Of the four reservoir zones identified, R11 in lowstand fluvial-deltaic deposits has relatively little cement and the best reservoir characters.

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A lack of planning techniques and processes on long, linear, cut and cover-tunneling route transportation systems has resulted because of the advancement of transportation systems into underground corridors. The proposed methodology is tested in Texas on a shallow cut and cover-tunneling corridor for a high-speed freight transportation system. Different surface (landform, geology, soils) and subsurface (hydrogeology, soil and rock properties) properties, as well as waste disposal and similar conditions along the corridor influence this methodology. Because this long distance cut and cover route is a new transportation concept, a new methodology must be developed to provide preliminary route selection information. The objective of this project was to develop a new methodology for transportation planning so that it can be used for transportation projects in the future. The technique that performs a preliminary investigation of an area is completed by studying the aspects of the environment and determining any fatal flaws along the corridor. Then a preliminary ranking system and evaluation can be conducted using other site evaluation techniques that aid in conducting a comparison of area and the selection of areas that appear to be most favorable for the facility. This methodology was applied to an area, roughly 400 miles long, along I-35 between Laredo and Dallas, Texas, where the Texas Transportation Institute, TTI, is considering a shallow cut and cover-tunnel corridor for a high-speed freight transportation system. The test successfully completed each objective and confirmed that this new methodology works. The results indicate that three main parameters, topography, demography, and rock mass, have the greatest impact on the underground corridor in this project.

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