Stones - The World's First 15 Ksi Ultra-Deepwater Subsea Pump

Abstract

Stones is a phased development that began producing in September 2016 from two subsea wells tied back to an FPSO. Full-field development includes six additional wells from two connected drill centers, and a subsea boosting system to increase production and extend the life of the field. This paper describes the technology qualification program (TQP) and execution experience, including the development, delivery and installation of the world's first ultra deepwater subsea boosting system. The paper also addresses the lessons learned from the project, from component qualification and engineering through to manufacturing and testing. The Stones field is located in the Walker Ridge area, approximately 200 miles southwest of the Louisiana coast. It consists of eight ultra-deepwater blocks at 9,579 feet water depth. As the operator, with 100% interest in the field, Shell announced its final investment decision in 2013. With reservoirs located at extreme depths, at more than 29,000 feet, subsea boosting was identified in the original project execution plan as a means to enhance recovery due to rapidly decreasing reservoir pressures. Multiple technology gaps were identified to meet the high-pressure, high-temperature (HPHT) design parameters for Stones. With a targeted design pressure of 15,000 psi, design temperature of 300 °F and nearly 10,000 feet of water depth, an extensive Technology Qualification Program (TQP) was executed to close these gaps. Six workstreams were developed to qualify the first article pump; these included valves and connectors, barrier fluid system, power system and controls. This was the start of a close cooperation between the operator and the pump system provider, whose common goal was to deploy the world's first 15 ksi ultra-deepwater pump. Following the TQP, in 2015, an engineering, procurement, and construction (EPC) contract was awarded that included a pump station with two 2.9MW pumps and a topside power drive system. The pump system has been through an extensive execution and test phase that was completed without injuries. The complete system was handed over to the operator and has been partially installed. The Stones boosting system has a daily production capacity of 60,000 bpd and will enable the operator to maintain and extend production at the field. Once the pump system is put into operation, it will significantly increase recovery at the field.