Best Practices for Obtaining Representative Formation Water Samples Using Formation Testers

Abstract

Abstract In the increasingly complex and challenging environments that oil and gas developments have to contend with, understanding of fluid properties is essential in optimizing the concepts that are ultimately used in development. The collection and analysis of downhole hydrocarbon samples have been given top priority, with the associated uncertainties having been dealt with adequately. By contrast, early assessment of formation water properties, has not always received the same level of attention with the reduction of the associated uncertainties generally not as robust. This paper discusses the primary water properties and their impact on field developments. We discuss why it is critical that formation water samples are truly representative of the actual in-situ formation water properties. We then examine the two biggest challenges for formation tester sampling: mud contamination and inadequate conditioning/handling of the samples, particularly in wells drilled with water based mud (WBM). Finally, a case study is presented including the use of a miscible water tracer as well as the use of focused-sampling to obtain water samples with ultra-low mud contamination to emphasize the importance of obtaining reliable decontaminated formation water properties.