Interrelationship of Wettability, Initial Water Saturation, Aging Time, and Oil Recovery by Spontaneous Imbibition and Waterflooding

Abstract

Previous studies of crude oil/brine/rock ͑COBR͒ and related systems showed that wettability and its effect on oil recovery depend on numerous complex interactions. In the present work, the wettability of COBR systems prepared using Prudhoe Bay crude oil, a synthetic formation brine, and Berea Sandstone was varied by systematic change in initial water saturation and length of aging time at reservoir temperature ͑88°C͒. All displacement tests were run at ambient temperature. Various degrees of water wetness were achieved and quantified by a modified Amott wettability index to water, the relative pseudowork of imbibition, and a newly defined apparent advancing dynamic contact angle.Pairs of spontaneous imbibition ͑oil recovery by spontaneous imbibition of water͒ and waterflood ͑oil recovery vs. pore volumes of water injected͒ curves were measured for each of the induced wetting states. Several trends were observed. Imbibition rate, and hence, water wetness, decreased with increase in aging time and with decrease in initial water saturation. Breakthrough recoveries and final oil recovery by waterflooding increased with decrease in water wetness. Correlations between water wetness and oil recovery by waterflooding and spontaneous imbibition are presented. Experiments Fluids.A Prudhoe Bay, Alaska, crude oil ͑A'93͒ was used as the oil phase. The crude oil was evacuated before use to reduce the possibility of gas evolution during the course of an experiment. The evacuated crude oil had a viscosity o of 39.25 cP and density o of 0.895 g/cc at 25°C. A refined oil, Soltrol 220, o ϭ3.98 cP, was used to obtain a set of imbibition and waterflood data for very strongly water-wet conditions. A synthetic formation ͑SF͒ brine was prepared: 21.3 g/L NaCl, 0.6 g/L CaCl 2 "6H 2 O, 0.1

A critical review on fundamental mechanisms of spontaneous imbibition and the impact of boundary condition, fluid viscosity and wettability

“…The wettability of cores could be changed by saturating cores with crude oil and aging under high temperature (Buckley et al, 1998;Standnes, 2000;Loahardjo et al, 2010). The different wettability could be obtained by different aging time and temperature (Zhou et al, 2000). Water or surfactant solution is drawn into the core by SI.…”

Wettability and Oil Recovery by Imbibition and Viscous Displacement from Fractured and Heterogeneous Carbonates

“…Zhou et al (2000) showed that with increase in the aging time, the scaled spontaneous imbibition became slower indicating decreased water-wetness. Four cores were used to test the effect of aging time.…”

“…Many parameters such as crude oil properties, initial water saturation, aging time, aging temperature, core preparation procedure, etc., can be adjusted to achieve a spectrum of wettability (Zhou et al, 2000;Xie and Morrow, 2001;Tie et al, 2003).…”

Influence of wettability and permeability heterogeneity on miscible CO2 flooding efficiency

“…Wettability is a major factor that controls multiphase fluid flow, location and distribution of fluids in a reservoir [3]. It has been well recognized that reservoir wettability significantly influences oil production during primary, secondary, and tertiary recovery (enhanced oil recovery) stages [4][5][6].…”