INVESTIGATE THE SPONTANEOUS IMBIBITION CHARACTERISTICS OF MARINE AND CONTINENTAL SHALES AND THEIR CONTROLLING FACTORS

Spontaneous imbibition (SI), one of the important factors affecting hydrocarbon recovery from unconventional hydrocarbon reservoirs, is a capillary-force controlled process. The properties of displacing and displaced fluids, pore structure, shale compositions, initial water saturation are the main factors affecting the SI process. We have compared the SI characteristics between marine and continental shale samples from China. Because of the layered characteristic of shale samples, we also conducted imbibition experiments along different directions.

Our results showed that shale samples with different compositions showed different SI behaviors. The reproducibility of water imbibition curves is strongly related to clay content and the continental shale samples with higher clay content exhibit lower water imbibition reproducibility compared with marine shales. The effects of initial water saturation on SI behaviors are different for shale samples with different mineral compositions. Wettability information is indicated by comparing directional imbibition curves. Low pore connectivity to water of both marine and continental shale samples is confirmed by SI experiments.