Classification and Evaluation of Reservoir Pore Structures Based on Petrophysical Facies: A Case Study on Formation KC in KX Field, Caspian Basin

Abstract

AbstractBased on the observation, study and analysis of core data, thin section, well logging and drilling data, the sedimentary facies, diagenetic facies and fracture facies of the carbonate reservoirs were carried out in Carboniferous Formation KC, KX oilfield, Caspian Basin. In this paper, the petrophysical facies of oil intervals in KC formation were examined to evaluate the pore and fracture structure and to predict zones with high porosity and permeability by classification. The petrophysical facies were divided by the superposition and combination of sedimentary facies, diagenetic facies and fracture facies. And a series of petrophysical facies of KC formation such as the pore-dissolved vuggy, the fracture-pore type, the high-angle connected fracture, were identified in this way. There are four main categories of petrophysical facies (PF-I, PF-II, PF-III and PF-IV), which are characterized based on the constructive and destructive effect of sedimentary facies, diagenetic facies and fracture facies on the reservoir property and pore structure in KC formation. Since the reservoir quality index (RQI) and the limestone structure parameter (LSP) are the important factors for describing the reservoir micro-pore and fracture structure quantitatively, both RQI and LSP values were calculated respectively in the different petrophysical facies. Therefore, the classification and evaluation of KC formation reservoir pore structure in a single well were realized by the classification of petrophysical facies combined with well logging and core data. Finally, the vertical and horizontal distribution of sedimentary micro-facies and diagenetic facies of each single layer of KC formation were plotted, the distribution of favorable petrophysical facies can be used to predict the zones with high porosity and permeability.KeywordsPetrophysical faciesCarbonateFracture faciesPore structureCaspian basin