Possibility of a more detailed seismic interpretation within the Miocene formations of the Carpathian Foredeep based on the well logs interpretation

摘要

The main aim of the article is to determine the possibility of a more detailed seismic interpretation in the autochthonous Miocene formations on the example of a 3D seismic survey from the Carpathian Foredeep area, based on the comprehensive analysis of well logs. The seismic survey located in the central part of the Carpathian Foredeep was selected for the study. This zone is characterized by the presence of natural gas accumulation in various types of traps. Four boreholes in which formation tests were conducted within the Miocene sediments were selected for the detailed interpretation of the well logs. An important element of the study was the seismic-to-well tie based on available measurements of vertical seismic profiling. The quantitative interpretation of well data was the basis for the distinction of several lithofacial complexes of diverse lithology, reservoir parameters, or the type of reservoir media saturation in the profile of each of the analysed wells. Water and hydrocarbon saturations were estimated based on Montaron's theory. With the defined seismic signature, it was possible to interpret seismic horizons away from the wells. Selected seismic attributes were used during the interpretation and analysis of the seismic image. There was a fairly high correlation between the well logs interpretation and the seismic record. Major lithological changes, thicker claystone interbeds within mudstone, or heterolithic deposits, as well as zones of significant changes in reservoir properties and the type of reservoir media saturation can be interpreted in the seismic image. In contrast, mudstone or heterolithic complexes of a large thickness (about hundreds of meters) in the seismic image are usually characterized by a monotonous low amplitude record and a significantly smaller continuity of reflections. The zones saturated with gas or gas and brine, documented in the analysed wells by the results of formation tests, usually can be identified on the basis of the seismic record. Due to the large variation of lithology and a substantial variability of individual parameters, it is not possible to reliably indicate in the seismic data which of the analysed objects are saturated with natural gas, and which with gas and brine. The results of well logs and integrated seismic interpretation allowed to obtain the complete picture of the Miocene siliciclastic formations diversity in the studied region, as well as a more accurate determination of reservoir properties and reservoir fluid saturation. The series of fine-grained sediments (mainly mudstone or heterolithic) in the lower part of the Miocene profile, within which several prospects were interpreted, was determined as the most interesting for hydrocarbon exploration.