Abstract
Capillary pressure and resistivity index spontaneous imbibition experiments by the porous plate method, in a core holder at elevated temperature and net reservoir stress, are both difficult and time consuming special core analysis measurements to perform. In this type of experiment, low capillary forces act against a low permeable porous plate and only one face of the cylindrical core sample is in capillary contact with the fluid saturated porous plate. In this paper, core samples having different lithology, petrophysical properties and wettability are analysed by counter current spontaneous imbibition, starting at initial water saturation (Swi), at net confining pressure and elevated temperature. Synthetic brine is used as the wetting phase and Isopar L mineral oil as the non-wetting phase. This methodology is applied to investigate and evaluate how to obtain more reliable, more efficient and faster saturation imbibition data combined with electrical measurements, during spontaneous imbibition measurements. Resistivity index (RI), saturation exponent (n) (by single saturation equilibrium point using Archie’s second law RI= Sw-n) and wettability information using representative fluids, confining pressure and temperature are also obtained by applying this specific counter current imbibition technique and improved procedural approach.
Highlights
Spontaneous imbibition is an important recovery mechanism and can occur in either co-current or countercurrent modes
Capillary pressure and resistivity index (PcRI) spontaneous imbibition experiments in a core holder by the porous plate method are performed after the primary drainage cycle by lowering stepwise the Pc of the displacing phase
Initial water saturation was established by capillary pressure primary drainage by the porous plate technique in single core holders at isostatic Net Confining Pressure (NCP) and temperature
Summary
Spontaneous imbibition is an important recovery mechanism and can occur in either co-current or countercurrent modes. The sample is loaded into an electrically insulated core holder during the whole experiment and should remain in the core holder at representative pressure and temperature conditions throughout the spontaneous capillary imbibition process This methodology allows additional wettability information derived from formation resistivity index data and complex impedance measurements to be obtained. Capillary pressure and resistivity index (PcRI) spontaneous imbibition experiments in a core holder by the porous plate method are performed after the primary drainage cycle by lowering stepwise the Pc of the displacing phase (oil). This allows the displaced phase (brine) to imbibe back into the samples through the water-wet porous plate or membrane. Tests of PcRI by countercurrent imbibition by low rate end face flooding have been performed on different sandstone samples (Bentheim, Berea and Parker type) and one carbonate lithology sample (Carbonate V)
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