“Second quantitative characterization” and its application in fractured-vuggy carbonate reservoirs

Abstract

The Ordovician fracture-vug carbonate reservoirs of Tarim Basin, are featured by developed vugs, caves and fractures. The strong heterogeneity results in huge uncertainty when these reservoirs are quantitatively characterized using merely static seismic data. The effective quantitative characterization of the reservoirs has been an urgent problem to be solved. This study creatively proposes the “second quantitative characterization” technique with the combination of dynamic and static data based on the primary static quantitative characterization and fully considering lots of key influence factors when conducting characterization. In this technique, dynamic analysis methods such as well testing, production rate transient analysis, dynamic reserve evaluation and dynamic connectivity evaluation are used to get understandings on this kind of reservoir. These understandings are used as statistical parameters to constrain the inversion of seismic wave impedance to improve the relationship between wave impedance and porosity and determine the fracture-vug morphology, calculate dynamic reserves, and then a more accurate fracture-vugmodel can be selected and used to calculate the oil-water contact inversely based on the results of “second quantitative characterization”. This method can lower the uncertainties in the primary quantitative characterization of fracture-vug reservoirs, enhance the accuracy of characterization results significantly, and has achieved good application results in the fracture-vug carbonate reservoirs of Tarim Basin.