Conference Agenda

An integrated study was developed to characterize the spatial patterns of facies distribution in Maastrichtian age Garzan Formation which is one of the most prolific reservoirs in the southeast of Turkey. The sedimentary architecture of depositional environment and the diagenetic history of this carbonate succession were built by the use of sedimentological analysis of well cuttings and cores, well logs, and three-dimensional seismic data in oilfields A, B, C, and D. A total of twenty wells were examined in detail to construct a 3D carbonate depositional model. The vertical and horizontal facies changes in shallow marine carbonate deposits of the Garzan Formation suggested that the rudist-dominated carbonate successions were built-up in distally-steepened carbonate ramp. The heterogeneity of the Garzan carbonate rocks is greatly influenced by diagenesis which overprints the sedimentary facies and impacts the reservoir properties. The main diagenetic properties defined in petrographic analysis are micritization, neomorphism, dissolution, cementation, compaction, and partial dolomitization. Seismic attribute maps allow estimating different geological properties of the subsurface and determining the stratigraphic heterogeneity. Spectral decomposition is a functional seismic interpretation method providing seismic facies map with distinctive colors. This study provides the correlation of the sedimentological facies to the seismic facies. Another aspect of this study is to reveal the possible mechanisms responsible for the formation of the channels identified on top of the Garzan Formation on the spectral decomposition map. Integration of the seismic data interpretation and sedimentological analysis suggested that these were the tidal channels influenced by bottom currents.

A 9.23 m long core, containing Cretaceous-aged Mardin Group carbonates, was retrieved from well T-3 in the T Production Field of the Southeastern Anatolia Region. This core was scanned using a dual-energy computed tomography (DECT) tool, and detailed image interpretation of the core was performed based on the obtained images. Six distinct flow zones were identified based on porosity-permeability values derived from analyses conducted on 28 core plugs.
These identified zones were then compared with the DECT images, and reservoir properties were evaluated on the images. High-resolution photomicrographs of thin sections prepared from the plug edges were obtained and petrographically analyzed. The facies characteristics, porosity types, depositional environment, and diagenetic variability of the formation were interpreted through these petrographic analyses. The petrographic findings were correlated with the flow zones, and the reservoir properties were examined and interpreted in detail.

An integrated sequence stratigraphic study is conducted to reveal the signals of eustatic sea level change during the Cenomanian-Turonian time interval in Diyarbakır, southeastern Turkey. Depositional sequences typical of Cretaceous greenhouse carbonate systems are defined in the seven wells based on lithofacies, paleontological data and INPEFA log data. The highstand systems tracks contain a greater abundance of grain-dominated shoal lithofacies with various benthic foraminifers while the transgressive systems tracks are represented by pelagic facies with high amount of mud dominated lithofacies containing calcisphaerulids and planktonic foraminifers. Carbon isotope studies are used to detect C-T boundary and OAE-2 and interpreted together with biostratigraphy, microfacies and INPEFA logs. Oxygen isotope studies are used to define parasequences and major stratigraphic surfaces together with the other tools. During the early Cenomanian time interval carbonate content increases with the decreasing rate of relative sea level and causes negative δ¹⁸O values at the bottom of the Derdere Formation. Other negative shifts detected on the oxygen isotope curves during the Turonian time interval can be related to the meteoric diagenesis. A depositional model for the highstand deposition on the Derdere ramp platform and diaganetic mechanisms generated during sea level fluctuations is proposed. At the time of the deposition of the highstand systems tracts, facies deposited on the inner ramp depositional setting were subaerially exposed and meteoric water infiltration caused dissolution and dolomitization. Dolomites, which are associated with the highstand systems tracts and meteoric diagenesis, enhances reservoir quality of the formation.

Early concepts of inversion tectonics relied on a model of half-graben bounded by deeply rooted listric fault that is subsequently reactivated as reverse fault, and as a result half-graben infill is uplifted and eroded. However, this model explains inversion of relatively small depocenters associated with uplift of relatively small crustal blocks, and it doesn’t include syn-inversion flexural subsidence of basin’s flanks, important during inversion of large sedimentary basins and uplift of large crustal block. Flexure of flanks of inverted basin implies specific thickness and facies distribution of syn-inversion strata, similar to foreland basin depositional system, with regional thickening of inversion-related succession towards the inversion axis, and presence of coarse-grained deposits in vicinity of basement blocks uplifted during inversion. The Late Cretaceous evolution of the Polish Basin provides excellent example of such flexural inverted basin. Its most subsiding axial part, the Mid-Polish Trough, was in Late Cretaceous transferred into the Mid-Polish Anticlinorium – major anticlinal structure that extends for approximately 1000 km from SW Baltic Sea towards the SE Poland and W Ukraine. Due to the large size of this structure, loading along the flanks of inverted basin axial part led to a regional flexure of its footwall. As a result, Upper Cretaceous syn-inversion succession is characterized by regional thickening towards the Mid-Polish Anticlinorium. Seismic data imaged Upper Cretaceous progradational wedges, localized thickness reductions, local unconformities and contourites that developed along the edges of crustal blocks uplifted during inversion.

This study was supported by NCN grants 2017/27/B/ST10/02316 and 2018/29/B/ST10/02947.

The study area lies in the central part of the Carpathian Foreland in southern Poland. The interval encompasses mixed carbonate-clastic facies of the Upper Cretaceous and the topmost part of the Lower Cretaceous –Upper Jurassic complex. The motivation for the research was to reconstruct the spatial orientation of faults concerning the major tectonic processes that took place in the area and to find the temporal and spatial relation with the sedimentation process. For this purpose, the novel interpretation tools of the colour-processing technique were applied for processing 3D seismic data. The idea behind the technique is to transfer the data into a new coordinate system that respects individual colour saturation. This result enables a new level of detail for structural interpretation, highlighting lineations within the seismic cube. Further validation of the proposed structural model was compared with the results of paleoenvironmental analysis, which is the result of the chronostratigraphic image and Wheeler diagram analysis. The techniques applied to the high resolution seismic data enabled better insight into the paleoenvironmental studies of the Late Cretaceous sedimentary basin in the research area. The resulting paleoenvironmental model is built based on seismic sequence stratigraphy, seismic attribute analysis and tectonostratigraphic analysis. The methodology allowed validation and modification of the previous tectonic model and allowed tracing of faults that continue into the Cenozoic formations. The work is founded by National Science Center Recognition of the depositional architecture of the Upper Cretaceous sedimentary basin in the central part of the Carpathian Foreland, 2021/43/D/ST10/02728.

Northern Central Europe is a key area for the Late Cretaceous intraplate deformation that is characterized by a tectonic inversion phase with the transformation of former extensional features into contractional structures. This inversion was distinct along the northern and southern margin of the Central European Basin System e.g., at WNW-ESE striking structures like the Sorgenfrei-Tornquist Zone, the northern Harz boundary fault and the Osning thrust. It is remarkable that so far, the best evidence for neotectonic activity in northern Central Europe and Denmark comes from these areas. It has also been shown that historic earthquakes, which were observed over the last 1200 years cluster at Late Cretaceous reverse faults like the Osning thrust, the Halle fault, the Haldensleben fault or the Gardelegen fault. These structures have in common that they penetrate large parts of the crust, partly down to the Moho. Therefore, they represent stress-sensitive, first-order lithospheric features, where past, present, and potentially future seismic events are manifested. Repeated reactivation of these structures might have caused large-scale fatigue processes that have weakened the faults and made them prone to stress release and neotectonic movements and enhance the potential for a reactivation due to glacial isostatic adjustment (GIA) related stress field changes. This has implications for the seismic hazard assessment of northern Central Europe.