Seismic reservoir characterization of gas-sand deposits in the Kutei basin, Indonesia

Kutei Basin has the second largest hydrocarbon reserve in Indonesia. In addition to the Miocene inversion related structural traps, slope-fan and channel stratigraphic traps are also important traps in this basin. To guide stratigraphic traps explorations in the basin, the seismic stratigraphy, attributes, and AI inversion methods are integrated to identify and map the reservoir seismic facies, porosity, and pore-fluid. Well data indicates that the studied reservoirs are filled by gas. Seismic data shows that there are two main gas-sand reservoirs corresponding to strong amplitude anomaly. Seismic stratigraphy analysis, guided by seismic attributes, shows that these gas-sand reservoirs were deposited in the channel and local fan facies. The AI inversion is applied to identify and map the porosity and pore-fluid of these two sand reservoirs. Future well locations are identified by integrating the facies, porosity, and pore-fluid maps.

The role of inertial instability in cross-hemispheric coupling

Recent studies suggest linkages between anomalously warm temperatures in the winter stratosphere, and the high-latitude summer mesopause. The summer temperature anomaly is manifested in the decline of polar mesospheric clouds. The two-day wave is a strong-amplitude and transient summer feature that interacts with the background state so as to warm the high-latitude summer mesopause. This wave has been linked to a low-latitude phenomenon called inertial instability, that is organized by breaking planetary waves in the winter stratosphere. Hence, inertial instability has been identified as a possible nexus between the disturbed winter stratosphere, and summer mesopause warming. We investigate a sustained occurrence of inertial instability during July 19-August 8, 2014. During this period, stratospheric winter temperatures warmed by about 10 K, while a steep decline in polar mesospheric clouds was reported between July 26–August 6. We present, for the first time, wave driving associated with observed inertial instability. The effect of inertial instability is to export eastward momentum from the winter hemisphere across the equator into the summer hemisphere. Using a primitive equation model, we demonstrate that the wave stresses destabilize the stratopause summer easterly jet. The reconfigured wind profile excites the wavenumber 4 component of the two-day wave, leading to enhanced warming of the summer mesopause. This work supports previous numerical investigations that identified planetary wave-driven inertial instability as a source of the two-day wave.

MJO Teleconnections over the PNA Region in Climate Models. Part II: Impacts of the MJO and Basic State

In an assessment of 29 global climate models (GCMs), Part I of this study identified biases in boreal winter MJO teleconnections in anomalous 500-hPa geopotential height over the Pacific–North America (PNA) region that are common to many models: an eastward shift, a longer persistence, and a larger amplitude. In Part II, we explore the relationships of the teleconnection metrics developed in Part I with several existing and newly developed MJO and basic state (the mean subtropical westerly jet) metrics. The MJO and basic state diagnostics indicate that the MJO is generally weaker and less coherent and propagates faster in models compared to observations. The mean subtropical jet also exhibits notable biases such as too strong amplitude, excessive eastward extension, or southward shift. The following relationships are found to be robust among the models: 1) models with a faster MJO propagation tend to produce weaker teleconnections; 2) models with a less coherent eastward MJO propagation tend to simulate more persistent MJO teleconnections; 3) models with a stronger westerly jet produce stronger and eastward shifted MJO teleconnections; 4) models with an eastward extended jet produce an eastward shift in MJO teleconnections; and 5) models with a southward shifted jet produce stronger MJO teleconnections. The results are supported by linear baroclinic model experiments. Our results suggest that the larger amplitude and eastward shift biases in GCM MJO teleconnections can be attributed to the biases in the westerly jet, and that the longer persistence bias is likely due to the lack of coherent eastward MJO propagation.

Diurnal Cycles of Precipitation and Lightning in the Tropics Observed by TRMM3G68, GSMaP, LIS, and WWLLN

Diurnal cycles of precipitation and lightning are investigated by analyzing rain rates of the TRMM3G68 dataset, consisting of Precipitation Radar and Microwave Imager data only; rain rates of Global Satellite Mapping of Precipitation (GSMaP), for which infrared (IR) data are also used; lightning flash rates observed by TRMM Lightning Imaging Sensor (LIS); and lightning stroke rates of World Wide Lightning Location Network (WWLLN) over the tropics. Diurnal amplitudes relative to averages are generally larger for lightning than for precipitation. Over ocean, relative amplitudes are stronger in the stratocumulus deck region in the southeast Pacific than those over typical ocean regions. The phase of GSMaP is substantially delayed to TRMM3G68 due to the phase-delay problem of IR-based estimation. The diurnal peaks tend to occur between 1400 and 1800 LST over the continent after spatial averaging with a phase leading order of TRMM3G68, LIS, and WWLLN, and between 0000 and 0700 LST over oceanic regions where diurnal cycles are prominent in all datasets. Off-equatorward phase propagations are found in the precipitation in the Pacific and Indian Oceans. Over selected coastal regions, all data exhibit consistent oceanward phase propagation with the longest, medium, and shortest phase propagation distances for TRMM3G68 precipitation, WWLLN lightning, and LIS lightning, respectively, with a phase leading order of LIS, WWLLN, and TRMM3G68. The summertime diurnal cycle over the Gulf Stream also exhibits oceanward phase propagation, but with strong amplitude enhancement over the Gulf Stream. Diurnal cycle amplitude is also enhanced over the Kuroshio in the East China Sea in the baiu–mei-yu rainy season.

Mechanisms and predictability of Sudden Stratospheric Warming in winter 2018

<p>In this study, we investigate the Sudden Stratospheric Warming that took place on 12 February 2018 (SSW2018), its predictability and teleconnection with the Madden-Julian Oscillation (MJO) by analysing ECMWF ensemble forecast initialised on 1 February 2018. Several days prior to that date MJO was in Phase 6 and had a strong amplitude potentially contributing to triggering the SSW. Two wave trains can be identified in the upper troposphere over the northern Atlantic and Pacific regions. Starting from the 3 February, the amplitude of planetary wave with wavenumber 2 (PW2) started to increase and reached record high values, while the PW1 amplitude decreased.</p><p>In order to better understand the sources of uncertainties, we divided the forecast ensemble members into two groups. The first group predicted the SSW onset in time while the second group of ensemble members did not capture the wind reversal at 60°N 10 hPa. The results obtained with the ensemble forecast data were compared with the ECMWF’s reanalysis ERA-Interim (ERA-I). The analysis of the two groups of ensemble forecasts shows that in the first group of forecasts PW2 prevailed with ridges over the Ural and Alaska and troughs over the west Siberia and Canada, as observed. Instead, PW1 is seen in the second group of ensemble members with a broad ridge over Eurasia. Calculations of wave activity fluxes show that there is less zonal wave energy propagation in the second group compared to the first group and ERA-I over Eurasia, which can be associated with the errors in the forecasted location of the Ural high. There is also wave energy propagation towards an area of high pressure over Alaska, as seen in ERA-I. Here, wave energy propagation is similarly underestimated by both groups. Overall, the structure of the geopotential anomalies averaged for 5-7 February for the first group and ERA-I is more consistent with the climatological response from MJO phase 6 taken with lag 5-9 days than that in the second group.</p>

The Seismic Image of The Direct Hydrocarbon Indicators in Offshore Syria

The easternmost Mediterranean Basin is a candidate to be one of the most important hydrocarbon regions in the world, especially after significant gas discoveries in Levantine Basin in 2009. Offshore Syria is one of the easternmost Mediterranean areas which is still an unexplored virgin area. The seismic interpretation results of the study area showed encouraging evidences of considerable hydrocarbon accumulations within different sedimentary successions, which are Direct Hydrocarbon Indicators (DHIs). Indicators such as reflectivity anomalies (flat spots and dim spots) and polarity reversal were found within significant structural highs of Tertiary or/Late Cretaceous and Early Jurassic successions. Also, gas chimney and a lot of bright spots were observed within a Plio-Pleistocene succession above tops and flanks of Messinian Salt diapirs and pinch-outs. The seismic attributes such as instantaneous frequency and phase and reflection strengths were used in this study to improve the seismic interpretation image in the gas-affected area, with the purpose of exhibiting strong amplitude abnormalities and confirming the occurrence of a polarity reversal and the low frequencies within and below some of the structural anticlines. These attributes suggest that there are potential hydrocarbon reservoirs.

Volcanic Clouds from the 1999 Eruption of Shishaldin Volcano: Comparison of Satellite and Seismic Observations

The main ash-producing phase of the 1999 eruption of Shishaldin Volcano, Alaska, occurred on April 19 and ejected ash as high as 16 km asl. High levels of tremor persisted for more than 18 hours, but ash production probably lasted less than 4 hours. The total erupted volume of the April 19 event was estimated to be at least 2.0 x 107 m3 DRE. Upper level winds transported mainly sulfur dioxide to the north above 10 km altitude, and mainly ash to the south below that level. The relationship between seismicity and ash cloud production changed following the April 19 event. Episodes of strong amplitude tremor from April 21 to 24 were associated with strong strombolian activity, but very little ash was produced that could be detected in satellite images. On several occasions in late May, extensive ash plumes were detected in AVHRR and GOES images, but seismic levels during these times of ash production remained at low-levels. Satellite data suggest that the ash produced during the May events contained more fine particles than that produced by the April 19 event.

Modeling Attenuation of Diffusive-Viscous Wave Using Reflectivity Method

Seismic waves in earth materials are subject to attenuation and dispersion in a broad range of frequencies. The commonly accepted mechanism of intrinsic attenuation and dispersion is the presence of fluids in the pore space of rocks. The diffusive-viscous model was proposed to explain low-frequency seismic anomalies related to hydrocarbon reservoirs. But, the model is only a description of compressional wave. In this work, we firstly discuss the extended elastic diffusive-viscous model. Then, we extend reflectivity method to the diffusive-viscous medium. Finally, we present two numerical models to simulate the attenuation of diffusive-viscous wave in horizontal and dip multi-layered media compared with the results of viscoelastic wave. The modeling results show that the diffusive-viscous wave has strong amplitude attenuation and phase shift when it propagates across absorptive layers.

Six new rapidly oscillating Ap stars in the Kepler long-cadence data using super-Nyquist asteroseismology

ABSTRACT We perform a search for rapidly oscillating Ap stars in the Kepler long-cadence data, where true oscillations above the Nyquist limit of 283.21 $\mu$Hz can be reliably distinguished from aliases as a consequence of the barycentric time corrections applied to the Kepler data. We find evidence for rapid oscillations in six stars: KIC 6631188, KIC 7018170, KIC 10685175, KIC 11031749, KIC 11296437, and KIC 11409673, and identify each star as chemically peculiar through either pre-existing classifications or spectroscopic measurements. For each star, we identify the principal pulsation mode, and are able to observe several additional pulsation modes in KIC 7018170. We find that KIC 7018170 and KIC 11409673 both oscillate above their theoretical acoustic cut-off frequency, whilst KIC 11031749 oscillates at the cut-off frequency within uncertainty. All but KIC 11031749 exhibit strong amplitude modulation consistent with the oblique pulsator model, confirming their mode geometry and periods of rotation.