Deep aquifer sampling and the use of ball check-valves systems
Abstract
Accurate monitoring of deep aquifers is one of the challenges with CO 2 Storage survey – but this challenge is not restricted to this thematic. Pumping deep waters is often not appropriate as it requires high amounts of water to be purged. Therefore deep sampling is often performed. Several devices exist; the simplest ones are based on the lowering of bottles with opened valves that are closed at the targeted depth. Improvement comes with bottles that are only opened at desired depth, or with bottles having an initial volume equal to zero that is enlarged through the functioning of a moving part that creates space and allows water to flows in. The problem with such bottles is that the volume is limited (from hundreds of mL to several litres) and that the bottle has to be risen up at the surface when filled. This may take much time. This sampling is also problematic if proper characterisation of dissolved gas species has to be done: an appropriate transfer system is required at surface. Sample handling may also modify physico-chemical characteristics of the fluid that may become lesser representative of in-situ conditions – even if it is established that sample retrieval will affect, whatever we do, some parameters (e.g. temperature).
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