Method for determining reservoir bulk volume of hydrocarbons from reservoir porosity and distance to oil-water contact level

摘要

For a formation zone of a well, a method for determining the relationship between bulk volume of oil &phgr;.sub.o as a function of total effective formation porosity &phgr;.sub.E and height h above the oil water contact from capillary pressure data of a core taken from the formation of the well is disclosed. The disclosed relationship of the form,PP&phgr;.sub.0 =C&phgr;.sub.E -K+g log hP Pwhere C, K and g are constants derived from the capillary pressure data of the core and the relationship between h and the capillary pressure is affected by the relative densities of the connate water of the zone and the oil in the zone.PPAccording to an alternative embodiment of the invention, log data may be used to characterize a well according to the relationshipPP&phgr;. sub.0 =C&phgr;.sub.E -K+g log hPPby using sets of data at different depths in the well with statistical regression methods, where the initial oil-water contact level may be determined from said log data. PPAccording to another alternative embodiment of the invention, core data may be used to determine the characterizing relation of a well, where the well does not penetrate the oil-water level of the reservoir asPPh(z)=10.sup.(&phgr;.sub.0 (z)-C&phgr; .sub.E (z)+K)/gPPbut log data of the well exists. From the log data of the well, &phgr;.sub.o and &phgr;.sub.E may be determined as a function of depth. The water level WL=h(z)+z may be determined from the log data and the relationship determined from capillary pressure analysis of the core data. The WL determination as a function of each depth z may be compared to determine reservoir capillary equilibrium or when comparing WL determined for different wells to identify that these wells reside in different reservoirs.