LoFS stands for Life of Field Seismic, i.e. a system with the intent to delivering values over the lifetime of a field
LoFS is mainly a development of how one applies existing seismic methods utilized in the industry for a number of decades. This development means the seismic sensors are installed permanently in the seabed covering a reservoir area of particular interest, often an entire field.
From a user point of view, a LoFS system offers some new features that support maximized reservoir utilization. Some important advantages are as follows:
– The resolution of reservoir images is very high, which ultimately supports operations and the drilling team’s planning and execution work.
– There is repeatability between surveys, i.e. generated images can be put on top of each other providing a graphical animation of the field’s physical development over time, allowing detailed monitoring of the various movements of oil, gas and water in reservoirs, and of course in the overburden in general.
– Seismically obscured areas are made accessible with LoFS, which can be installed also inside platform exclusion zones.
– A repeat survey can be organised quickly should it be required. New data and images may be generated within weeks if determined necessary.
LoFS is in relative terms a new type of system for the oil and gas companies. Historically seismic services are contracted as stand-alone services by geophysicists from the seismic service providers, not requiring the involvement of internal expertise by the engineers and projects department.
While LoFS is a permanent installation involving a significant number of interfaces, the road from pre-appraise and feasibility to execution requires LoFS to be treated as a regular oil and gas investment project, adjusting it to each specific oil company’s and asset’s processes and procedures for approvals through all their defined stages.
The main technical development is that LoFS sensors are permanently installed, remaining in their original installation location, and preferably for reliability reasons permanently connected to an energy source and a seismic data storage system. This not only allows the user to continually monitor the system’s functionality, but also allows passive monitoring to take place, and not the least it allows the system to be used within short notice, equal to the time it takes to mobilize the shot array.
There are two main LoFS technologies available. The traditional electrical systems based on technology having been around for several decades, also used in non-permanent applications (Nodes, OBC, towed streamers etc.). Then there is the fibre optical technology that conceptually is used exactly the same way electrical systems are, but does not include electronics subsea, having all the electronics topside.
From an operational perspective, LoFS means an add-on in terms of responsibility for the geophysical community in the oil and gas companies. They become the owners of a system, which mainly consists of the equipment on the topside, in the seabed and an array for seismic shooting.
Often the permanent part of the systems are possible to remote operate, avoiding the need for personnel being on board topside during data acquisition. However, it requires a service arrangement with the LoFS system supplier.
The system may be continuously powered to passively record seismic events, but to allow acquiring a regular LoFS survey, the shot array should be available on a relatively short notice, and the same equipment specification should be used for every survey to ensure consistency and high data quality.
Ideally, a LoFS system is integrated in existing preventative maintenance programs such that it is treated by operations the same way other equipment is.
Commercially LoFS requires taking a life-of-field perspective. To commit to one technology for the lifetime of a field, is a new concept in the seismic community. Irrespective of the commercial arrangement for LoFS, a solid business plan is needed, containing as much tangible information as possible, demonstrating the reasons for investing in this long-term commitment.
From 2002 through 2014, with limited variations, the most common commercial arrangements include outright purchasing of the LoFS permanent equipment, combined with a number of service contracts for installation, maintenance and operation.
Alternative arrangements are possible, such as leasing, where local tax regimes may determine which commercial model is advantageous for each specific asset.
The LoFS system needs a dedicated owner responsible for keeping the system healthy: monitoring its functioning, budget, maintenance, operation and applicable service contracts.
Some spareparts should be considered being available, preferably consigned to the system supplier such that availability and functionality is guaranteed. The philosophy may differ between the topside and the subsea equipment, while the topside equipment can be accessed on a relatively short notice, where intervention activities can be organised in the matter of days. The subsea equipment is designed to last for many years without maintenance, and repair should only be required in case of physical damage to the system. Organising repair of the subsea system may take several months, depending on the arrangements provided on beforehand. Should this be determined unacceptable, a stand-by solution can be set up.