5th EAGE St.Petersburg International Conference and Exhibition on Geosciences - Making the Most of the Earths Resources

Reservoirs of Jurassic complex in the Barents Sea sediments were formed under transgressive-regressive regime of sedimentation in the midst of the marine basin’s general transgression. In Jurassic time eastern and western sectors of the Barents Sea basin developed as a single basin under calm tectonic environment. This gives the possibility to identify general sedimentation cycles within the limits of this region.

The Cenozoic regional uplift remains very poor investigated for the Russian part of the Barents Sea. Several methods were used to estimate magnitude of the uplift and erosion for the Eastern Barents Sea. First method was related with using of generalized porosity-depth trends. Geophysical well logging data from the Russian Barens Sea (about thirty deep offshore wells) were compiled and processed. The joint interpretation of sonic, gamma-ray, resistivity, spontaneous potential logs were used to calculate porosity and shale fraction for siliciclastic rocks. Comparison of smoothed exponential porosity-depth curves from different wells reveals the rate of compaction for the different kinds of sediments (sands, silts and shales) and different level of erosion. Similar results were obtained with Magara’s approach for sonic logs of shales. We used vitrinite reflectance data for the independent evaluation of the uplift and for calibration. Combining the data on wells we have determinated uplifts ranging from 300 m in the south (Pechora Sea) to 700 m in the central part of the South-Barents deep and to 2 km in the Franz-Joseph Land. The magnitude of erosion increase eastward as well. Seismic profiles and structural maps were used to trace and interpolate the estimates of uplift between wells.

Present evaluation of Lower-Upper Permian and Triassic clastic deposits in the Russian Barents Sea shelf are based on detailed geological and seismostratigraphic interpretation of regional seismic lines acquired by MAGE in 2007-2009. Active uncompensated subsidence of South Barents and pre-Novaya Zemlya depressions in Early-Late Permian and sea level changes led to the formation of three sequences in which low-stand, transgressive and high-stand system tracts were identified. Low stand system tracts infill central parts of the basin and contain high-amplitude discontinuous reflections which may indicate sandstones of basin fans. High-stand system tracts are characterized by sigmoid progradational reflection pattern with high-amplitude facies at clinoform bends corresponding to perspective shallow-water reservoirs. Pemian-Triassic erosion unconformity is well-traced at the basin margins. Triassic strata in the study area were formed in deltaic, coastal and shallow-marine conditions under constant compensation of basin subsidence with large volumes of sediments. They are characterized by hummocky high-amplitude reflection configuration at basin margins and low-amplitude sub-parallel discontinuous seismic pattern in the central parts. Bright, parallel, continuous reflections in the Middle Triassic correspond to sea level rise and shale deposition. Structural and stratigraphic traps were identified in Triassic complex.

The article discribes the main stages of the section hydrocarbon productivity forming. It is based on the generation and migration processes and their evolution during the geological history. The main result of the project is the new objects for exploration studies and phase composition prediction for the possible hydrocarbon deposit.

With growing interest in the hydrocarbon potential of the circum-Arctic, increasing attention is turning to the frontier shelves of the East Arctic such as the Laptev Shelf. No deep wells have been drilled offshore, with stratigraphic predictions based on study of onshore outcrops, including the Taimyr Peninsula, northern mainland Siberia and New Siberian Islands. The discovery of hydrocarbon fields in Jurassic-Early Cretaceous clastics of the Yenisey-Khatanga and West Siberian basins, and in Permian-Triassic clastics of the Lena-Anabar Basin, highlight Late Palaeozoic-Mesozoic potential in the neighbouring offshore. Early Cretaceous post-orogenic and Late Cretaceous-Palaeogene syn-rift coal-bearing clastics could represent the most significant source rocks. Marine organic-rich facies of the PETM and Middle Eocene “Azolla” event may constitute oil-prone source rocks in restricted grabens. Oligocene-Early Miocene sandstones and Late Miocene-Pliocene marine shales could represent regional reservoirs and seals respectively. We have conducted a study of the region using a global sequence stratigraphic model, drawing on data available in the public domain. This interpretation allows enhanced understanding of the shifting distribution of transgressive and regressive reservoir facies. When placed in a regional palinspastic framework, models of source rock deposition can be developed, and used to better predict timing and extent of deposition.

Our approach consists in 1. constraining the evolution of rifted shelf with the age of magnetic chrons in the Eurasia basin, and interpret a break-up unconformity that correlates in time with the emplacement of the oldest oceanic crust in the Eurasia Basin 2. Differentiate on seismic the sedimentation patterns from greenhouse conditions from those of icehouse conditions, as documented by the ACEX well drilled on Lomonossov Ridge. 3. Correlate nearshore structural cross sections, calibrated on deep wells with shallow water seismic data 4. Compare the basement structure prepared from magnetic records with the acoustic basement interpreted from seismic data 5. Calibrate older seismic data against newer, acquired with long-streamer, to better define the base of the rift infill and its relation to regional structural styles existing from Verkoyansk to Annabar.

The uplift of cretaceous reflecting horizons revealed earlier in a sea direction, has allowed to suggest presence of structures not defined earlier, located in a coastal zone which could be perspective objects for searches of hydrocarbonic raw materials. A neogene – upper cretaceous deposits are perspective here according to prospecting--production drilling. The second regional stage of inspection of southern Foothill Dagestan which has included inspection of a coastal and shoaly zone of the Dagestan part of Caspian sea was finished in 2007-2008. Newly interpreted received results of regional seismic operations, in inspecting the South Dagestan bow area, have allowed to specify a structural and tectonic construction on a neogene- upper cretaceous deposits, to substract in a coastal and shoaly zone 14 new structures perspective for searches of oil and gas and to give them a resource estimation

В работе представляются результаты новой серии региональных сейсмических профилей, пересекающих всю Черноморскую впадину и отработанных с использованием современных технических средств и технологий спустя 30 лет после проведения здесь первой серии подобных исследований. Полученные материалы позволяют по новому представить ряд аспектов геологического строения, тектоники, истории формирования впадины и её современной геодинамики.

A modified approach of AVA analysis is presented in this paper. It is AVO screening technology which combines AVO analysis and statistical rock physics study for gaining insight into the hydrocarbon reservoir.This workflow is time-efficient and allows for the analysis of large seismic volumes with limited or no well control.

The Common-Reflection-Surface (CRS) method may improve seismic processing beyond imaging, e.g. in an enhanced Amplitude Versus Offset (AVO) analysis. Various applications have shown that the more realistic subsurface assumptions, and the increased fold of the CRS imaging allow to extend AVO analysis into noise zones and to deep targets with low signal quality. Extreme fluctuations of AVO parameters are removed, and AVO anomalies are enhanced. The CRS method assumes subsurface reflector elements with dip and curvature, which implies large-fold stacking surfaces extending both across offset, and across neighboring CMP locations. The extension across neighboring CMPs defines a CRS gather at the central CMP location, comprising data from a multitude of traces. The CRS moveout correction compensates for the local dip across these neighboring CMPs, thus contrasting to conventional AVO super-gathers based on NMO correction that collect dipping events horizontally at varying phase. The presented case studies show that CRS-AVO attribute stacks are produced with a much higher signal-to-noise ratio from CRS gathers than from CMP gathers in conventional AVO. The CRS-AVO attribute sections clearly distinguish anomalies at known or expected gas-bearing reservoirs.