Simulation and experimental wettability studies on low salinity water injection and CO₂ low salinity water-alternating-gas injection

Ma, Shijia (2022) Simulation and experimental wettability studies on low salinity water injection and CO₂ low salinity water-alternating-gas injection. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Low salinity water injection (LSWI) and CO₂ low salinity water-alternating-gas (LSWAG) injection are promising enhanced oil recovery (EOR) methods with economic and environmental advantages. Wettability alteration is considered as one of the important mechanisms. Over the past decades, there have been studies conducted to model LSWI process using shift in relative permeability curves as an indicator for wettability alteration and understand the changes in wettability induced by CO₂ and low salinity water using contact angle measurements. However, inherent limitation exits in these measurements and linking the measured contact angle to relative permeability curves for oil recovery prediction requires more research. The objective of this research is to examine whether changes in quick contact angle measurements during the injection of low salinity water or CO₂ can be used to predict oil recovery instead of conducting time-consuming core flooding or relative permeability experiments. This will be achieved first by a comprehensive literature review on CO₂ LSWAG injection to understand the mechanisms and the effect of different parameters. Secondly, the effect of temperature and interpolation techniques to relative permeability curves considering different driving forces to wettability alteration is studied. Thirdly, a newly-proposed “displacement” method for measuring contact angle is employed to study the effect of CO₂, low salinity water and injection schemes. Finally, the possibility of linking contact angle to relative permeability curves for oil recovery prediction is explored. It is found that the inclusion of hysteresis in CO₂ LSWAG injection optimization is crucial. Increasing injection temperature in the sandstone block model leads to an increase in oil recovery due to the promotion of chemical reactions with increasing temperature. The proposed “displacement” method is capable of capturing the effect of geochemical reactions and surface forces and can be used for screening optimal brine composition and injection schemes. Linking the measured contact angle to relative permeability curves has a potential for predicting oil recovery.

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