No abstract

SUMMARYThe objective of the research is a reference framework set of petrophysical data characterizing the Devonian siliciclastic sediments of the study area. The characterization workflow includes three main stages: the first is the lithological typification from core description, the second is matching of the identified lithotypes with their petrophysical properties and the third is testing the model against wireline logging data. The core from selected wells was described for lithological typification and studied with routine and special core analysis procedures in the laboratory. It is well known that shale content changes the physical properties of the rock, hence the results of the particle size distribution analysis were used to group the samples into classes based on the grain size subject to the ratio of clay material in the rock fabric. The normal trend is observed for increase in shale content with smaller grain size. Based on the lithological description all the samples were grouped into three petrophysical classes then characterized by their own petrophysical relations and constants. This approach is based on the fact that the shave volume as opposed to grain size can be estimated from well logs and then applied to reservoir characterization and differentiation.

SUMMARYThe tasks of the research included detailed description of the core with further distinguishing of lithotypes, examination of geological aspects, generation of lithologic and facies maps. In the work the facies model of Devonian terrigenous stratum isformed; the model was obtained based on description of the core of 30 wells, analyses of 423 thin sections and granulometry data of 440 samples. The basis to distinguish lithotypes is layer-by-layer description of rocks according to lithological composition and fraction size as per granulometry, as well as peculiar textural features.In the result of performed analysis of the deposit core of Devonian terrigenous stratum there are 14 lithotypes, which served as a basis for transition to deposition environment and further distinguishing of facies. To specify depositional conditions regional data were used, according to which deposition of sediments in the period of formation of Devonian terrigenous stratum took place in conditions of shallow sea.According to comprehensive study data of the core and geophysical well logging, in the sections of the key-wells relevant facies were distinguished and facies inhomogeneity maps were generated (from the point of view of cyclic structure of horizons).