Abstract
Wettability in chalk has been studied comprehensively to understand fluid flow mechanisms impacting coreflooding experiments. Wettability becomes paramount in understanding the parameters influencing chalk-fluid interactions. The main objective of this work is to evaluate as to which degree the wettability in chalk core samples can be controlled in the laboratory. Kansas chalk samples saturated with brine (1.1 M/64284 ppm NaCl) and an oil mixture (60% - 40% by volume of Heidrun oil and heptane) were aged at a constant temperature of 90oC with aging time as the laboratory control variable. A multimodal method incorporating contact angle measurements, wettability index via USBM test, and SEM-MLA analysis was applied in evaluating wettability. A systematic approach was applied with the three different methods to quantify the degree of uncertainty linked to a) wettability estimation and b) the aging procedure to control wettability alteration of Kansas chalk. With a comprehensive suite of samples, we were successfully able to alter the wettability of chalk cores.
Highlights
Wettability is the tendency of one fluid to spread on, or adhere to, a solid surface in the presence of another immiscible fluid
Anderson [2] indicated that 1000 hours (40 days) of aging at reservoir temperature is sufficient for wettability equilibrium for sandstones
In order to ensure that brine chemistry are not ignored during the aging process it is important to saturate the core with brine prior to any flooding of oil
Summary
Wettability is the tendency of one fluid to spread on, or adhere to, a solid surface in the presence of another immiscible fluid. Wettability is of paramount importance in oil recovery from low permeability chalk as it controls the flow and distribution of fluids [1]. Numerous studies have indicated a number of factors influencing wettability including the composition of oil, rock mineralogy, fluid saturation, brine composition, temperature, and time of aging [2]. One of the simplest experimental control variables is the aging time. Anderson [2] indicated that 1000 hours (40 days) of aging at reservoir temperature is sufficient for wettability equilibrium for sandstones. In order to ensure that brine chemistry are not ignored during the aging process it is important to saturate the core with brine prior to any flooding of oil
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