Fluid sampling challenges
Obtaining clean samples of undersaturated crude oil near its bubblepoint from undercompacted, weak, low-permeability mudstones in the presence of miscible mud filtrate invasion poses a daunting challenge.
Pressure drawdown must be tightly controlled to avoid both formation erosion and fluid phase transitioning while flow rates must support sufficient cleaning and minimize the risk of tool sticking. The borehole geometry and relatively shallow reservoir depth limit the volume of crude oil that can be allowed into the mud system, further increasing the importance of efficient cleanup.
