Temperature, surface forces, wettability and their relationship to relative permeability of porous media.

摘要

Accurate modeling of thermal recovery processes requires relative permeability functions and information about the effects of elevated temperature on these functions. Examination of temperature and its relation to relative permeability has been conducted since the 1960's. Controversy over the sensitivity of relative permeability to temperature, and the direction and magnitude of these changes, reflects the complexity of rock-fluid interactions in porous media. In this work, we study the role of temperature on porous media properties from a surface forces perspective. The effects of temperature on rock wettability are examined, because this variable is inherently linked to relative permeability.; This research and field operations indicate that reservoir rock exposed to high temperature undergoes a systematic shift in wettability toward water wetness. Consequently, steam and steam condensate become more effective displacement agents and the rock matrix imbibes water more effectively.; A mechanism is developed where fines mobilization presents one pathway to create fresh water-wet surfaces. Fines detachment, and accompanying thin water-film stabilization, with increasing temperature are conditioned by fluid pH, salinity, mineralogy, and temperature. We find experimentally and theoretically that fine particles are released from pore walls under conditions of elevated temperature, alkaline pH, and moderate aqueous-phase salinity in Berea sandstone and diatomite. The correlation between initial clay content and wettability shift is both confirmed and explained. Experimental and theoretical results agree remarkably well.; Because interpretation methods play an active role in this problem, two reliable techniques are developed for estimation of two-phase relative permeability from the water saturation profile history obtained during spontaneous imbibition experiments monitored using X-ray computerized tomography. Both techniques are validated with synthetic data. The techniques include capillary forces, return arbitrary shaped relative permeability and capillary functions, and allow measurement of relative permeability from a single experiment. Results confirmed that relative permeability and capillary pressure functions for diatomite are nonparametric. Results show that unsteady-state techniques must account for capillary pressure and nonequilibrium effects during the estimation of relative permeability. Finally, it is confirmed that the impact of temperature on relative permeability depends on mineralogy and fluid bulk conditions.