The results of complex interpretation of seismic survey and well data in Gurgan Deniz area

Abstract

As a result of combined analysis of seismic surveys conducted in Gurgan-deniz and neighboring areas and logging data as well, the geological structure of the studied area was specified, various seismic attributes (both as by seismic cubes and by separate seismic surfaces) were calculated. To have a clear insight about the lithofacies variability of the studied area, corresponding 3D models have been developed.  With the purpose of restoring the sedimentation conditions, a facies analysis of the area based on the visual study of the length and configuration of seismic reflections, as well as seismic amplitudes has been carried out, the changes of the power of separate intervals in which we are interested have been studied and the logging of the facies conducted. To define the connection between the dynamic parameters of seismic records and geological properties of the area in the promising intervals, several attributes (Sweetness, RMS, Instantaneous Frequency, Variance etc.) have been calculated and analyzed. The calculation have been conducted in a large diapason for all productive horizons (marked as potential reservoir). Sharp changes in the composition of rocks in the studied area are associated with a periodic transgression and regression, as well as with the fluviation. Three types of geological phenomena may occur during specific periods of cycle turns of rising and lowering of sea level: progradation and regression (recession of the sea), retrogradation or transgression (sea movement towards shore) and aggradation (comparatively stable state of sea level). In the view of sharp variation of lithologic composition of the sediments, predominantly in the bottom of Productive Series (PT), we can conclude that highlighted facies are characteristic for specific parts of the studied area. When highlighting the facies, the direction of sedimentation material brought by the rivers and source of nourishment has been revealed. According to the results obtained, we suppose that almost each lithofacies type has its own distribution area. Therefore, the fluviation plays a significant role in the distribution of the facies in the studied area of the Caspian basin, as well as in the accumulation of hydrocarbons. Complex research surveys carried out enabled to mark specific perspective oil-gas bearing objects in Gurgan-deniz and neighboring areas.