In the first stage of this project, studies of imbibition of water to displace gas from the matrix and other properties were performed for Berea Sandstone. The understanding and practice obtained in this stage first stage has been useful in the second stage where the same properties has been measured for diatomite and compared. Thus, a systematic experimental investigation of capillary pressure characteristics and fluid flow in diatomite has begun. Using an X-ray CT scanner and a specially constructed imbibition cell, we study spontaneous water imbibition processes in diatomite and for reference Berea Sandstone and chalk. The mass of water imbibed as a function of time is also measured.
Imbibition is restricted to concurrent flow.
Despite a marked difference in rock properties including permeability and porosity, we find similar trends in saturation profiles and weight gain versus time functions. Imbibition in diatomite is relatively rapid when initial water saturation is low due to large capillary forces. In this study, we study in more detail the properties of the rock and the effects that each of these properties have on the process of spontaneous imbibition. The saturation profile history allows direct computation of the relative permeability for both phases from a single experiment when used in combination with a previously measured capillary pressure curve. Results are unique within experimental error.