Study of Waterflooding Process in Naturally Fractured Reservoirs from Static and Dynamic Imbibition Experiments,” paper

Imbibition plays an important role in oil recovery from the naturally fractured Spraberry Trend Area. Therefore, understanding matrix-fracture transfer and the key parameters associated with the imbibition process are important. We examined these issues by performing static and dynamic imbibition experiments. Oil recoveries from both experiments were matched and the imbibition processes were investigated by developing a numerical finite difference scheme and utilizing a commercial simulator. Static imbibition experiments, followed by waterflooding, were performed at reservoir conditions to investigate rock wettability. A two-phase and 2-D, fully finite-difference implicit scheme was developed to solve non-linear diffusion in the static imbibition equation. The numerical results that matched satisfactorily with the spontaneous imbibition data were applied to investigate the effect of key variables on the imbibition rate. We found that the measurement of Amott wettability index and the capillary pressure result suggested that the Spraberry rock matrix is weakly water-wet. Dynamic imbibition experiments were performed using artificially fractured Berea and Spraberry cores at reservoir conditions to illustrate the actual process of waterflooding in naturally fractured reservoirs. A commercial numerical simulator was used to match these experiments to generate matrix capillar