Personnel location technology on an offshore super-complex in the Persian Gulf
28 August 2019
The Al Nasr super-complex consists of many platforms, towers and facilities off the United Arab Emirates. In this. In this article, Dr Charlotte Richardson of S3 ID discusses the different radio location technologies used on the project and explores the benefits of each.
The Al Nasr oil field is located about 130 km northwest of Abu Dhabi in the Persian Gulf. Adma-Opco, a joint venture of Abu Dhabi National Oil Company (ADNOC – 60%), BP (14.67%), Total (13.33%) and Japan Oil Development Company (Jodco, a subsidiary of Inpex Corporation – 12%) is the operator of the field.
The Al Nasr super-complex includes an accommodation platform, a gas treatment platform, and a separation platform connected by bridges to earlier structures, two wellhead towers and a manifold tower. Five other wellhead towers, utility facilities and thousands of kilometres of pipelines make the oil field’s installations amongst the most extensive in the world.
Locating personnel on large, multiplatform structures is challenging. Personnel can arrive or leave by boat or helicopter, and it is vital to know exactly who is on site at any time. In the event of an emergency, it is important to quickly identify where personnel are, or where they were last seen if they fail to muster.
The challenges of personnel location on supercomplexes
From 2015 to 2018, field development was undertaken to increase production from 22,000 barrels per day to 65,000.
The Nasr Phase II Full Field Development Project was split into three Engineering, Procurement and Construction packages (EPCs). Seven wellhead towers were constructed on EPC 1 along with hundreds of kilometres of pipelines. EPC 2 formed the core facility and part of this was the installation of the Nasr multi-platform super-complex (NSSC). This included an accommodation platform (AP), a gas treatment platform (GTP), and a separation platform (SP) connected by bridges to the structures developed during phase I; two wellhead towers (WHT1 & 2) and a manifold tower (MFT-1). MFT-1 connects to nearby facilities at Abu Bukoosh and Umm Shaif.
Such a large and complex structure presents challenges for personnel location and the evacuation safety case, and requires protection for the assets and personnel on board. Consequently, a system to enhance facility safety and protect people and assets was needed as part of EPC 1 and 2.
The requirements of the safety and security system included control and monitoring of access to the facility. Identifying which platform people are on and when they cross the bridges is particularly significant when allocating lifeboat places. Electronic mustering technology was required for emergency situations.
Additionally, the safety case needed to identify which platform level personnel are located on, and even room occupancy. Room occupation is particularly applicable to battery rooms, where certification requirements are more stringent, and additional hazardous gases may be present, or Local Equipment Rooms (LERs), where access may be restricted to a few authorised personnel.
Selecting technology to overcome the challenges of personnel location on supercomplexes
To overcome the challenges posed by the size of the Al Nasr super-complex, the personnel location system supplied makes use of two different radio technologies, one short range and another longer range proximity system.
All personnel arriving on the super-complex, whether by boat or helicopter, are issued with a tag during a familiarisation briefing in heli-reception. Dual tags are provided with lanyards and are worn by all personnel during their time on the facility. When personnel leave the facility, their tags can easily be de-allocated and re-allocated to new personnel arriving.
At the boat decks, close range RFID technology is installed. The low frequency 125 kHz tags work with a portal layout of readers which makes use of the natural choke points and provides the direction of travel for personnel during embarkation and disembarkation. This technology is ideal for monitoring movement between platforms and remote wellhead facilities. As personnel pass from the facility on to the boats, they are recorded as being in transit.
Given the scale of the super-complex, using 125 kHz throughout would have required installation of a very large number of readers, and so a different technology, S3 ID’s Checkpoint, was used to meet the platform level and occupancy requirements. Larger areas, or zones, are covered by this higher frequency technology. Checkpoints record tags entering into RFID detection zones, which are tuned to approximately 10 metres within the interior of the platform, and larger zones on the periphery.
Detection zones can be visualised as spheres. Readers are located on each platform level, or stairwells and bridges, and personnel location information is monitored during normal working conditions. Bridge tracking capability records the movement of personnel from one platform to another, and ensures that there are sufficient lifeboat places available for those arriving. Personnel recorded in transit on boats arrive at remote wellheads and then disperse. Checkpoints then detect them, and update their locations from in transit to present on the wellheads, or other platforms, for example.
The AP and GTP have designated muster areas. During drills and musters, Checkpoint readers in these areas become more sensitive to ensure that all personnel are detected. Should anyone have forgotten or lost their tag, they can manually muster at the confirmed muster station. The last known location of any missing personnel can be easily identified with this system, enabling rescue teams to minimise their time in danger. Evacuation procedures are then followed to transfer personnel to lifeboats.
Checkpoint technology uses the 433 MHz frequency in the Industrial, Scientific and Medical (ISM) band, which is license free or licensable in many countries. The 433 MHz bandwidth works well in environments cluttered by infrastructure and is not particularly affected by the highly metallic environments offshore, making it a good choice for this application.
Checkpoint uses Received Signal Strength Indication (RSSI) for location. However, RSSI alone can vary quite significantly and so S3 ID’s software was developed to allow a number of other factors to be taken into account. These include several averaging or trending mechanisms to aggregate the data. Thresholds can also be set to ignore readings below a certain level. The flexibility of this approach to the software design is that the system can be uniquely configured for each location, and even for each tag if necessary. For example, a battery room may be quite a small zone when compared to a walkway, and so the settings can be adjusted to account for this. Alternative antenna types can also be used, depending on the range required.
Because of the zonal approach used on Al Nasr, mustering is performed using confirmed muster stations, requiring people to interact with the muster station to confirm their presence and providing visual indication that their tag has been seen.
The challenges of locating personnel on each different level of super-structures and in transit between the different parts of the facility can be overcome by using configurable, zonal location technology.
The performance of this can be improved by the inclusion of short-range mustering technology to monitor precisely personnel movement during evacuation or in emergency situations. The combination of the two technologies provides enhanced security and safety protection for personnel on the Al Nasr super-complex.
About the author
Dr. Charlotte Richardson is the Product Development Manager at S3 ID Ltd and has been with the company since 2009. S3 ID specialises in personnel location systems for hostile and hazardous areas in the oil, gas and energy industries. Prior to working with S3 ID, Charlotte had various engineering roles and also worked as a lecturer teaching Mechanical Engineering.
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