Well injectivity during CO2 storage operations in deep saline aquifers--Part 1: Experimental investigation of drying effects, salt precipitation and capillary forces

Abstract : Carbon Capture and Storage (CCS) is a technique than can potentially limit the accumulation of greenhouse gases in the atmosphere. Well injectivity issues are of importance for CCS because the gas injection rate must be maintained at a high level (a million tonnes of CO2 per year and per site) during the industrial operation period (30-40 years). The risk of altered permeability must therefore be determined in order to guarantee the sustainability and the security of the CO2 geological storage. Injection of dry gas in deep saline aquifers might lead to near wellbore drying and salt precipitation. The solid salt might then reduce the rock permeability by clogging pores or by pore throat restriction. The objective of this paper is to present new experimental results on the drying of rocks induced by continuous injection of large amount of dry gas (N2). The main goal of the study was to understand and model the physical processes that govern the decrease in water saturation in reservoir rocks. Two types of sandstone were used to study slow and fast drying rates and capillary effects on drying. The experimental results evince the main physical parameters that control the key mechanisms. In a companion paper in this issue (André et al., 2013), we show that the continuous approach in the context of a compositional two-phase flow model can fairly well predict the saturation evolution in the near wellbore and the alteration in permeability due to salt precipitation.