Thru Tubing Electrical Submersible Pumps Failures Analysis: Insights and Recommendations from Installations Offshore Malaysia

Thru Tubing Electrical Submersible Pump (TTESP) is a relatively new and impressive technology in which high-speed slim pumps are installed inside the existing tubing using completely rigless techniques. Two new TTESP installations were done in a brownfield located off the coast of Sarawak in Q2 2022, which suffered downhole re-circulation within a month of installation. Exhaustive data acquisition was done during the troubleshooting process including simulation in a test well. This paper will discuss the data acquired, investigation results and lessons learnt for the two wells. Both the installation operations were successful, and the wells were commissioned at the designed liquid rate of 1400 bpd with very stable ESP parameters. However, one month after the installation, both the pumps stopped producing fluid to surface after a pump trip event. The trips were initiated by a facilities shutdown and underload condition for the two wells respectively. Subsequent efforts by the Operator to troubleshoot and revive the well included extensive pump data analysis, bullheading from surface, test well simulation, dynamic modelling, and nodal analysis. The inability of the pump to develop head along with other pump parameters such steady rate of motor temperature increase, constant motor load during start-up etc indicated a potential re-circulation. However, since both the pumps were fully stable during the first month after installation and the problem was noticed only after the trip event in both wells, further troubleshooting was required to determine possible causes and remediation measures. Fluid bullheading from surface was done to record the ESP and surface pumping parameters followed by a transient simulation modeling. Analysis of data and modeling results indicated that stinger of the pump assembly had been "un-stinged" in both the pumps during the trip event. Simulation of events in a test well was done using same TTESP and downhole assembly and this exercise successfully confirmed the recirculation hypothesis. All the acquired data and modeling work done during the troubleshooting exercise along with test well simulation details will be shared in the paper. Based on the above troubleshooting outcome, the future plan for both wells is to retrieve and re-install the TTESPs with a check-valve below the TTESP assembly and also incorporate additional locking mechanism at the stinger. TTESP is a high impact technology in the artificial lift section since the cost of installation is only 10 per cent of a rig-based ESP installation. As such, it is very suitable for brown offshore fields with limited gas lift supply. This paper will be extremely useful for all operators planning TTESP technology for artificial lift since potential infant failure causes, novel troubleshooting technique for TTESP along with TTESP design and installation improvements will be discussed in the paper.