An operator in a North Sea field faced the challenge of scale buildup in its wells, a common occurrence for the area. The buildup would slow production in affected wells, so the operator would pump inhibitor downhole as a preventive measure. From 2006 to the end of 2014, the operator performed approximately 630 scale squeezes on about 50 wells in the field, 10 of which had ESP failure within 1 month of a scale squeeze. Although a 0.02% failure rate seems low, the cost of each workover is USD 2 million, which is a significant cost when multiplied by 10 wells.
The SLB dismantle, inspection, and failure analysis (DIFA) team determined that the 10 ESPs that failed experienced electrical failures immediately after the scale squeezes. The DIFA team discovered that the problem was fluid ingress past the AFLAS elastomers. AFLAS elastomers have temperature limitations and are compromised if the temperature reaches below 50 degC [122 degF]. The operator asked SLB for a solution that would help maintain a minimum downhole temperature during scale squeezes to avoid leakage past the seals.
SLB recommended implementing Lift IQ services. The Lift IQ service delivers 'round-the-clock remote surveillance of all artificial lift systems, preventing or resolving ESP downtime, misuse, or failure. Experienced engineers monitor alarms and analyze data transmitted from multiple wells across fields simultaneously in real time, up to 24/7/365 at one of many SLB Artificial Lift Surveillance Centers (ALSCs).
When ALSC engineers receive alarms and alerts, they use their expertise, experience, data resources, and SLB best practices to identify possible causes and remediation options. Some recommendations can be implemented remotely, enabling immediate intervention to prevent shutdowns or restart pumps; others are relayed to field personnel, who can rapidly complete the necessary action because they know the most likely diagnosis before they arrive on the location.
For the wells in the field, SLB engineers used a proactive surveillance plan to remotely monitor downhole temperature data from gauges on the ESPs. ALSC engineers monitored the wells during all scale squeeze operations. If the well temperature dropped below 70 degC [158 degF], the ALSC engineers advised SLB engineers at their offshore control room to reduce the injection rate of the scale squeeze by 15%. If the well temperature hit 50 degC—the low limit threshold of the elastomers—the ALSC engineers would notify SLB to pause the operation until the temperature stabilized to maintain the elastomer integrity and prevent ESP failure.
In the 2 years since the operator began using the Lift IQ service, 54 wells have had 157 scale squeezes with no subsequent ESP failures. Using the averages from 2006 to 2015, at least two ESP failures would be expected. Because of the Lift IQ surveillance and coordination with SLB operations, however, no well has dipped below the minimum acceptable temperature. Every ESP for the operator in the field has started successfully after a scale squeeze since the Lift IQ service was implemented.
