Abstract:

The Ordovician oil pools in Tahe oilfield are of karst fractured-vuggy carbonate reservoirs formed by multiphase tectonic movements and karstificaion.The main reservoir space,composed of pores,cavities,and fractures,is featured by low-porosity and strong anisotropy and heterogeneity.The log interpretation and evaluation of these reservoirs differs greatly from that of sandstone reservoirs.This paper summarizes the main reservoir types that can be identified by FMI logging based on core calibration.It also studies conventional log response characteristics of all types of reservoirs and identification methods of reservoir through log interpretation,and analyzes factors that might affect the identification of reservoirs and methods for differentiating these factors.Based on ca-libration of core and FMI logging data,the paper presents integrated probability model for fracture and dual porosity model,and realizes quantitative assessment of fractured-vuggy carbonate reservoirs with conventional log data.Positive results have been gained by using them in quantitative log assessment of the fractured-vuggy carbonate reservoirs of the Ordovician in Tahe oilfield.

Key words: log characteristics, carbonate rock, reservoir evaluation, Ordovician, Tahe oilfield