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The Investigation of Hydrocarbon Saturation in the Transition Zone with the Capillary Pressure Model

Petrov, Alexander *1; Kozhevnikov, Dmitry A.1; Kovalenko, Kazimir 1; Deshenenkov, Ivan S.1
(1) Gubkin Russian State University of Oil and Gas, Moscow, Russian Federation.

In oilfields development process it is necessary to determine attitude of fluidal contacts performed by the deposit area on the base of geological, geophysical and petrophysical data integration add-in advanced well logging techniques. Hydrocarbon distribution in oil-water transition zone reflects total reservoir properties, which are characterized by dependence of current fluid saturation value on capillary pressure.

There are a lot of capillary pressure models (water saturation value dependences on height above free water level) for the hydrocarbon distribution in transition zone studies. The most widely used models are J-function (Leverett model), Hassler-Brunner model, Brooks-Corey model, etc. All of them describe capillary pressure curves shape not accurately at low and high current water saturation levels. This fact is reflected on quality of the capillary pressure changes account in various ranges of permeability. To overcome this shortcoming we propose new model, controlled by a single parameter that is closely related to reservoir properties (effective porosity and permeability), i.e. the value of this parameter can be determined according to well logging data.

The proposed model allows predict the share of the displaced fluid at a given capillary pressure. Model verification was conducted on the representative core samples collection (over 300 samples) - fine-grained sandstones with complex mineral composition from different fields worldwide (Western & Eastern Siberia, Caspian region, Middle East, Alaska, etc.). The model provides the most accurate description of core laboratory data. It’s relevant for hydrocarbon saturation distribution prediction in the reservoir fluid dynamic 3D models. Such distributions are simulated for Western Siberia and Middle East oilfields.

The advantage of the developed algorithm is the possibility of hydrocarbon saturation reliable prediction in case if resistivity logging is non-informative due to the poor vertical resolution in layers of low width (less than 1,5-2 m) and anisotropic reservoirs.

The model application at the late stages of field development can identify intervals with changed saturation by comparison of the current and established from the model initial hydrocarbon saturation. The proposed model estimates the amount of fluid expulsion in the drainage process. It allows determine the location of column perforation to reduce water production while fields development.


AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain