SCA2009-20 1/12 ACQUISITION OF CORE CAPILLARY PRESSURE DATA BY IN-SITU SATURATION MONITORING – A COMPARATIVE EVALUATION

Accurate quantification of hydrocarbon saturation (1- Sw), a key volumetric parameter in reservoir characterisation, has a profound impact on the economic development potential of oil and gas fields. Drainage capillary pressure (Pc) data acquired from core are required to model initial water saturation (Sw) distribution in the reservoir as a function of height above the free water level. Imbibition (Sw increasing) Pc is not considered in this paper. Pc data can be acquired from core by a variety of methods – traditionally by ultracentrifuge, porous plate and air-mercury injection. Each technique has its own advantages and disadvantages – in terms of how well the Pc curve is characterised. The ultracentrifuge offers several advantages including achieving higher capillary pressure and much shorter test duration than porous plate. A disadvantage is that the Pc curve is constructed indirectly, based upon Sw calculated from a theoretical model(s)[15]. Although the accuracy of Pc curve modelling improved significantly during the 1990’s based upon the work of such authors as Forbes [6], the capacity to form a robust bu