The wireline formation tester (WFT) is a well-developed technology used to collect representative downhole fluid samples. Collecting low-contamination downhole samples in wells drilled with miscible oil-based mud (OBM) is challenging because the process must balance the need to acquire a sample with the desired level of contamination while using the minimum rig time.
The authors introduce a simple but effective method for monitoring WFT sampling when targeting the low levels of contamination needed for asphaltene-onset-pressure analysis.
Introduction
Flow-assurance problems caused by asphaltene deposition are common reasons for lost and deferred production in Gulf of Mexico Miocene reservoirs. High-quality samples are needed to measure the asphaltene-onset pressure and manage related flow-assurance problems. The asphaltene-onset pressure varies with the level of OBM contamination.
