Improvements in Downhole Fluid Identification by Combining High Resolution Fluid Density Sensor Measurements with New Processing Methods; Saudi Aramco Field Case Study

Palmer, Richard³
 Silva, Andre³
 Saghiyyah, George³
 Rourke, Marvin²
 Engelman, Bob¹
 van Zuilekom, Tony¹
 Proett, Mark¹
 Silvan, Adrienne¹

Accurate chemical and physical properties of hydrocarbon and formation water are required for efficient reservoir and production management. Frequently during exploration and field development a sample of formation fluids is required. One method to obtain reservoir fluid samples is with a pumpout wireline formation tester (PWFT) where the objective of sampling is to collect a representative fluid sample with minimum rig time. Sampling mixed phases or immiscible fluids has been a long standing challenge for fluid identification (FID) using pumpout wireline formation testers (PWFT). The mixing of fluids that are flowing inside the tool increases sensor noise making interpretation of fluid type and amount of contamination difficult if not impossible. Consequently these noisy sensor readings are often ignored and attributed to a transitional phase of sampling. This erratic behavior has been observed with most sensors including resistivity and optical sensors. With the introduction of a new high resolution fluid density sensor and improved data handling techniques, it is now possible to identify more precisely these mixed fluid flow regimes of hydrocarbon and water. The new fluid density sensor quickly and reliably monitors the change of frequency of a vibrating tube that is filled with the fluid sample. As a consequence of the high accuracy of this technique, it is possible to determine additional fluid properties such as density, water salinity and fluid compressibility. Furthermore, the new processing methods provide a clearer understanding of the flow behavior enabling more accurate estimates of fluid contamination. Data from the tool can also be used to observe changes in fluid properties over depth intervals and aid in identifying fluid interfaces and compartments.