Downhole gauges for ESP systems typically use the motor power cable for communicating data to surface. This type of gauge technology, also known as “Comms on power,” has been in use for many years and has become a reliable method for monitoring pump and well performance. Downhole data acquisition also delivers benefits in reservoir management where continuous data from the well is required. Any loss of this downhole data has a significant impact to accurately understanding the well performance and reservoir recovery.
Current gauge technology is susceptible to problems when the insulation on the motor cable ages or is damaged. This means that the gauge signal will be lost when a ground fault occurs, even if the ESP motor continues to drive the pump and the gauge itself is undamaged. Current ESP gauges also typically provided slower data rates than permanent gauges that have dedicated instrument lines to surface.
In such situations there are two options to recover the downhole data; conventional data acquisition using wireline or workover to repair the ground fault. Both required additional operational cost. Furthermore, any opportunities to obtain improved ESP monitoring and continuous data acquisition for reservoir management are gone.
Saudi Aramco has been engaged in several years of technology trials carried out in Saudi Arabia leading to a successful field trial of a new downhole sensor system. Saudi Aramco's drive for continuous data when the ESP has experienced a ground fault has been the catalyst for the support given to this system. The system was installed in April 2013 in the Khurais field and is currently still running today — the system was confirmed to be fully functional in ground fault conditions. This paper presents the new technology, the history of trails and the installation, outlining the potential for future use.