The challenge of maintaining unobstructed and undamaged multi-well flowlines in deepwater subsea systems along the brazilian seabed.
With the advent of subsea fields composed of multiple subsea wells, the flows from each well pass through a manifold where they enter a larger flowline commingling with the other flows. This larger flowline containing the commingled flows is then transported to the FPSO.
The problem is maintaining control over the performance of each of these wells without the use of support vessels or platforms (if a hot intervention is needed), which greatly increase operational costs.
A good example of this maze of subsea wells is the Frade subsea field, which is composed of 22 wellheads and 19 subsea trees in 1,330m (4,000 ft) of water, 370km (230miles) offshore in the North Campos basin off the coast of Rio de Janeiro.
The Frade wells are commingled in groups to larger flow lines, which are then transfered to a single FPSO.
What makes the performance control of each of these wells possible is the development and use of proven and reliable instrumentation for flow monitoring of individual wells before commingling into the manifold, this includes the use of multiphase metering of individual wells.
The objective of the field operators is to attain optimal production from the multiwell field without increasing operational costs unnecessarily.
At the same time operators need to understand and have realtime access to information regarding remaining life of components, material decay and other physical problems that may arrise in order to plan and execute efficient interventions.
Another important aspect of flow assurance is the need to monitor these flows before commingling in order to know if there are wells, tieback lines, jumpers, gathering stations and risers, clogged with production decreasing elements such as deposits of paraffin, scale or hydrates.
This is fundamental in order to enable operators to understand and predict flow problems in sufficient time to take mitigating action and also to be able to predict problems in advance in order to be capable of undertaking preventive maintenance.
Conditions that cause flow problems or even impede flow can be pervasive and diverse, therefore no standard solution exists.
Chemical and mechanical solutions may be used, sometimes simply insulating flow lines to preserve flow stream temperatures solves the problem or boosting flowline temperatures using heating elements may suffice and sometimes a combination of these remedies is used.
However, without a closed-loop process that guarantees continuos feedback and analysis of flow obstructions and equipment problems and stress, results will be suboptimal.
Instrumentation and sensors installed along the flow lines offer a complete system of reliable, predictive models for understanding solids deposition, corrosion, wax deposits and various other problems that can occur along and within the flow lines.
This is specially important to deepwater operation along brazilian seabed as the deeper the wells/reservoirs are the more costly it is to make interventions.
Companies such as FMC, Schlumberger, Halliburton and GE Oil & Gas are industry leaders in developing solutions that enhance production and make the whole subsea production and distribution system more reliable.
Fortunately for the deepwater subsea fields in Brazil, the very techniques and technologies developed and implemented to support continuos flow assurance also benefit effective well/reservoir management and optimize production.
Claudio Paschoa
Photo courtesy of FMC Technology