Title page for ETD etd-1023102-142927


Type of Document Master's Thesis
Author Vijapurapu, Chandra S
Author's Email Address cvijap1@lsu.edu, vijapurapu@hotmail.com
URN etd-1023102-142927
Title The Effects of Rock and Fluids Characteristics on Reservoir Wettability
Degree Master of Science in Petroleum Engineering (M.S.P.E.)
Department Petroleum Engineering
Advisory Committee
Advisor Name Title
Dandina N. Rao Committee Chair
Jeremy K. Edwards Committee Member
Zaki Bassiouni Committee Member
Keywords
  • Wilhelmy tehnique
  • dual-drop-dual crystal technique
  • brine dilution
  • optical profilometer
  • interfacial tension
  • surface roughness
  • spreading
  • surfactant
  • rock mineralogy
  • adhesion
  • contact angle
  • wettability
Date of Defense 2002-08-27
Availability unrestricted
Abstract
Wettability is the ability of a fluid to spread or adhere on a rock surface in the presence of other immiscible fluids. Knowledge of wettability is important to decide what production strategy needs to be employed for optimum oil recovery. Wettability is affected by rock mineralogy, rock surface roughness, and brine compositions.

Previous studies have dealt with solid-liquid-vapor systems and those involving wettability characterization in solid-liquid-liquid systems have used contact angle techniques known to have reproducibility problems. In this study, a new technique called the Dual-Drop-Dual-Crystal (DDDC) Technique has been used to characterize wettability in terms of dynamic contact angles. The Wilhelmy Plate technique has also been used to measure contact angles for a comparative evaluation of the DDDC results. In studying the effects of surface roughness, brine dilution and surfactant addition in crude oil-brine-rock systems, the Wilhelmy was found to be insensitive, while the DDDC showed significant effects of mineralogy, roughness, brine dilution and surfactant addition on dynamic contact angles.

Study of the effects of brine dilution on dynamic contact angles was conducted using Yates brine and its diluted mixtures with deionized water in different proportions. In this study, interfacial tension has been measured using the Drop Shape Analysis (DSA) technique and the results have been compared with those obtained using the du Nuoy ring Tensiometer. A parabolic trend in interfacial tension was observed, with an initial decrease with increasing brine percentage in the mixture and then an increase after attaining a certain minimum. An unxpected effect of oil drop spreading on the rock surface yielding large contact angles was observed for certain brine dilutions. This spreading phenomenon was correlated to the receding angle and interfacial tension as discussed (24,36). A similar effect of oil spreading was also observed when using synthetic brine.

This study investigated the effect of a nonionic surfactant on wettability. Initial oil-wet nature of the Yates system was rendered intermediate-wet at certain concentrations of the surfactant. At higher concentrations, the advancing angle decreased to a strongly water-wet angle, indicating the ability of the surfactant to alter the wettability of the crude oil-brine-rock system.

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