Reservoir Monitoring (ReM) System

System Description

The Reservoir Monitoring (ReM) system is an open architecture subsea sensor network, designed for permanent deployment on the sea floor. The system is intended to enable the use of 4-component (4C) seismic data in reservoir management and integrate this with 3rd party sensors and subsea infrastructure. With the ReM system, a permanently installed seismic data acquisition becomes a standard item in the reservoir development plan. Once it has been installed, the system is used to perform repeated active (time-lapse / 4D) seismic surveys of the reservoir as required to control the development of the reservoir. It is also used for safety and environmental monitoring, by monitoring the integrity of the reservoir, caprock and subsea environment continually through the use of passive seismic methods.

The ReM system uses 4C sensor nodes with a 3-axis VectorSeis® MEMS accelerometer assembly and a hydrophone. The VectorSeis® sensors provide improved frequency response, lower self noise & distortion, and superior vector-fidelity (cross-axis isolation) compared to competing sensor technologies. The VectorSeis ® sensor has been proven though many years of reliable field operations, both in land seismic (ION Geophysical Scorpion) and 4C ocean bottom (ION Geophysical VecorSeis ® Ocean) systems.

Architecture

The system can be divided in two main parts, the Topside Equipment and the In-water Equipment. The Topside Equipment consists of computers and other hardware and software for recording of the seismic data, and for powering and controlling the In-water equipment. The In-water Equipment consists of a number of sensor Receiver Blocks, composed of a number of Receiver Array lines, and associated cables to connect it to the Topside Equipment.

The recording system software is developed in cooperation with Concept Systems (part of the ION Geophysical Corporation) and is based on existing industry standard components with a proven track record.

The in-water part of the system is designed with focus on reliability and redundancy, in addition to best-in-class sensor response and low cost. The ReM system’s unique by-pass method, bidirectional power & data transmission, and patented penetrator design are all key elements in the industry’s most reliable and robust system of its kind on the market.

The system is modular, consisting of smaller building blocks that can be combined in different configurations to meet the requirements for each installation.

Main System Specifications

The following are the main specifications for the system.

Maximum Water depth >2000 m
Fiber-optic umbilical length 10 km
Number of sensors/receivers No limit
Design life system 25 years
Sensor/receiver array length 24 km (@50 m sensor/receiver spacing)
Sample rate 1,2,4 ms
Timing accuracy <10 μs
Power dissipation Depend on system size
Power dissipation Depend on system size
Temperature °C requirements/subsea installed equipment Operation: -4 to 40
Storage: -18 to 50
Sensor frequency range 0 to 375Hz
Accelerometer sensitivity 40ng/bit
Hydrophone sensitivity 13.4 Pa/s/bit