The geochemical reactions resulting from CO₂ injection into the midale formation, Weyburn oilfield; A laboratory experimental and modelling study

This chapter provides an overview of fluid chemical and mineralogical changes occurring in a series of well-constrained laboratory experiments that have utilized samples of Midale core from the Weybum field and synthetic formation water based upon measured well fluid compositions. Experimental and theoretical studies of the effects of CO ₂ injection into the Midale lithologies indicate variable amounts of carbonate mineral dissolution, some precipitation of gypsum "inhibition" of anhydrite dissolution, and poor (i.e. slow) reactivity of alumino-silicate minerals over the timescale of the experiments. These indications helped develop appropriate hypothesis and approaches to simulate the long term evolution of an ID model representing CO ₂ injection into the host Midale Marly formation. The key objective of the chapter is to investigate the reactions between injected CO ₂, Midale lithologies, and porewaters under temperatures and pressures representative of in-situ conditions. The laboratory studies involved closed system batch experiments reacting samples of Midale reservoir rocks (Midale Marly, Midale Vuggy) and "cap rock" (Midale Evaporite) with synthetic saline reservoir porewaters.