A New Methodology on Reservoir Modeling in the Fracture-Cavity Carbonate Rock of Tahe Oilfield

Abstract

Abstract Tahe, one of the largest scale oilfields which are discovered in western China recently, in which Ordovician carbonate as the main storage, characterized with deeply embedding and various storage type, mainly are cavities and fractures. It is difficult to describe as its serious heterogeneity and there is rare technical reference regarding the reservoir modeling methodology. Commonly, the geology modeling is based on well logging and seismic data, and the stochastic method is reasonable applied. However, Tahe oilfield has very limited seismic data and poor well logging interpretations, especially for the fracture-cavern section. Furthermore, as it is controlled by paleukarst, the stochastic geological method, which is widely used in the ordinary sedimentary, is unacceptable to Tahe. The volumetric reserves calculation, which is suitable to sandstone but is not applicable to the fracture-cavity reservoir either, as it can not be proved in the severe anisotropy fracture-cavity carbonate formation. Furthermore, the concept of porosity and saturation is less meaningful in this kind of reserves. As a result, there is no applicable modeling method to describe the geological characters of the Tahe carbonate reservoir. A new methodology which is characterized by the fracture-cavity volume is presented in this paper. Accordingly, a new reservoir modeling and a new reserve calculation is built up. Mainly from geology, combined with static and dynamic data, a quantified 3-D reservoir model of Ordovician reservoir is formed, and this modeling methodology is proved practically by the results of history match from the streamline numerical simulation. The result will technically support the exploitation of Tahe oilfield.