Core analysis information is considered one of the cornerstones of formation evaluation. However, there seems to be general consensus that more could be done with it, both in the scope of the petrophysical data obtained and how it is used. In recognition of this, a suite of methods have been developed that provide a ‘new’ extended core data set, and software has been designed expressly for the interpretation of core data.
Historically, there has been a gap in the services provided by core analysis laboratories. Routine core analysis (RCA) provides core plug measurements such as porosity, permeability, fluid saturations, grain density and whole core gamma at high sample frequency and low cost. However, this data has limited interpretative potential. On the other hand, special core analysis (SCAL) provides a range of information with high interpretative potential, but at a low sampling frequency, primarily due to the cost and extended time frames associated with gathering the data.
A new data set was designed to compliment the current (RCA) data set, significantly extending its interpretative potential. The additional measurements performed are total, effective and furnace porosity, capillary pressure versus water saturation curve, surface area, core plug spectral gamma and an extended sample description. This new information fills the gap that currently exists between RCA and SCAL data, by providing significant interpretative potential at a high sampling frequency and in a reasonable time frame.
The computation of core-based or core-enhanced petrophysical interpretations has also been hampered by the lack of software designed expressly for modeling core data. Most petrophysical packages are decidedly log-centric, which has limited the effective integration of core and log data. Much core data processing is performed using spreadsheets, with inherent data integration and transfer limitations. To redress the balance, a core interpretation module designed to handle both the new data suite and existing core data, has been developed within a main-stream log analysis software package.
Applications using the new data suite include calibration of petrophysical parameters, the estimation of Qv profile from surface area data, the independent assessment of water saturation through the reservoir, and the estimation of initial reservoir flow properties at production start-up. The final outcome is that core analysis becomes truly a parallel formation evaluation discipline. In order to illustrate the core-log integration capabilities of the package, case studies are presented.