Capillary Pressure

Capillary pressure is a critical parameter for the oil exploration and production industry, and is a common measurement performed in core analysis laboratories. However, traditional techniques such as porous plate, centrifugation and mercury injection are laborious, time consuming and expensive.

The patented GIT-CAP capillary pressure measurement technique uses capillary pressure theory combined with NMR-determined saturation profiles, allowing for the accurate development of capillary pressure curves. With this technique, the core plug is first fully saturated with brine, and is then centrifuged to create a distribution of fluid in the plug which is in turn dependent on capillary pressure.

Typical results are shown in the following figures for two sandstone samples.

 

Figure 1: Saturation profiles for a sandstone sample with a permeability of 20.4 mD and porosity of 5.74%
Figure 2. GIT-CAP capillary pressure curve for the sample of Figure 1.
Figure 3. Saturation profiles for a sandstone with a permeability of 9.7 mD and porosity of 13.7%
Figure 4. GIT-CAP capillary pressure curve for the sample of Figure 3

Capillary pressure measurements using the GIT-CAP method are substantially faster than those made by traditional techniques, particularly for low permeability samples with longer equilibrium times. They also provide significantly more data points, allowing more accurate prediction of additional parameters such as pore throat distributions, wettability, and relative permeability.