Failure of umbilicals such as leakage or blockage in the hydraulic lines can be a challenge during operation of subsea infrastructures such as Christmas trees. These failures cause loss of redundancy and, in worst case, the operator will lose control of important valve functions on the trees. In that instance, the operator is forced to shut down production to perform costly umbilical repair or replacement prior to resuming operation.
As an alternative to umbilical repair and replacement, Siemens has developed a compact subsea hydraulic power unit (SHPU) for installation close to the subsea tree. The unit is intended as a standardized part of the operators’ toolbox, and is connected to the tree by Subsea Instrumentation Interface Standardization (SIIS) level 2 interfaces. The SHPU will take available electrical power from the existing infrastructure at the well site, and store it in a battery based energy bank. When hydraulic power is needed for valve operations on the well system, it will be provided by a pump driven by an electrical motor. Installation and retrieval of the SHPU can be done using a typical inspection, maintenance and repair (IMR) Vessel with a lift wire and remote operated vehicle (ROV) assistance.
The SHPU may also be used as a building block to develop long step-out developments in a cost-efficient way. By producing the hydraulic power locally at the seabed, it is possible to remove the hydraulic lines of the umbilical and thereby gain significant reductions in investments.