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For all the commentary on intelligent oil fields and 'smart' well-based operations, operators are still struggling to access all the information they need on their subsea operations and subsea well performance.
It is no coincidence that subsea wells still tend to generate up to 15% less average recovery rates than their topside counterparts, with much of this due to a lack of information that can lead to costly subsea interventions.
A lack of pressure and temperature information, for example, can result in the need for well intervention techniques such as logging, perforating, and plug setting, and if not detected in areas behind the well, the casing can be even more damaging.
Similarly, completion components might have to be replaced and wellbore access freed up if sand is not detected early in the wellstream. The dangers from water breakthrough in the wellstream can lead to significant production problems relating to hydrate formation. Furthermore, the stakes are high with an increased focus on subsea operations and growing subsea infrastructures.
Douglas Westwood's "World Deepwater Market Report" forecasts a 90% growth in deepwater expenditure between 2012 and 2016, and Emerson expects the number of new christmas trees coming onstream each year to increase from about 280 in 2011 to around 720 by 2016. These subsea trees also will bring with them associated hardware, such as control modules, wellbore equipment, manifolds, and umbilicals – equipment that will all need monitoring.
The need for intelligence subsea
Today's operators need subsea fields and well architectures to be equipped with the very latest in subsea monitoring and maintenance techniques, with the success of these wells dependent on the vast amount of real-time, fieldwide production information generated. This requires the use of "intelligent solutions" that can provide continuous monitoring, handle and generate value from huge reams of data, and remain proactive throughout the production life cycle.
The bottom line is that today's smarter oil and gas organizations must apply new technologies and processes to capture and transform raw data into actionable insight.
The potential benefits are huge. Shell, for example, estimates that using intelligent technology for monitoring and controlling a field results in around 10% more production of oil and 5% of gas.
Growth in intelligent multiphase meters
The evolution of multiphase meters is a good example of the move toward increased intelligence subsea. Subsea multiphase and wet gas meters generate crucial real-time information on flow conditions in the reservoir and act as an important alternative to traditional well testing. They provide data on flow conditions in the reservoir and track the development of gas coning, water breakthrough, indications of residual oil, and even reservoir zone interconnectivity.
While previously being viewed as standalone products, today they are an integral part of a much broader field management system and come with a variety of intelligent features that negate the need for subsea intervention and maintenance. These include condition monitoring and intelligent self-diagnostics to improve flow computer capabilities, consistency checks, data validation and configuration, alarm systems, and calibration with third-party PVT modules.
The latest subsea multiphase and wet gas meters from Emerson also come with a number of intelligent new features. For example, a soon-to-be-launched subsea wet gas meter comes with new transmission-based technology to extend the operating range, improved accuracy and reduced PVT dependence through multivariate analysis, and a new salinity measurement system.
While such features are crucial in reducing the need for subsea intervention, it is through the interaction of these meters with other subsea instrumentation that they can be used to their full potential and contribute to an intelligent fieldwide production system. In this way, they move away from just being part of the reservoir engineering discipline and adopt a multidisciplinary approach across the reservoir's life cycle.
Such integration can include everything from the wet gas meters identifying water breakthrough and enabling remedial action to be taken via other instrumentation to the combining of multiphase meters with other intelligent downhole pressure and temperature devices.
In this way, crucial decisions such as choke setting or EOR techniques such as artificial lift can be based on all the necessary information. Reconciled well phase flow rates, for example, can be combined with permanent downhole gauge data to calculate predefined production targets and system constraints.
GoM, North Sea examples
In the deepwater Independence Hub field in the Gulf of Mexico (GoM), Emerson's Roxar subsea wet gas meters played a key role in measuring the early onset of formation-water production.
The meters' intelligent measurement capabilities are based on advanced microwave-based dielectric measurements. The meter detects the resonant frequency in a microwave resonance cavity with the resonant frequency depending on the dielectric properties of the fluid mixture present in the cavity.
When water is detected in the well, the meters can provide crucial information to the operator, Anadarko Petroleum, allowing preventative or remedial action to be taken through other subsea instrumentation. This might include chemical distribution and injection systems, which ensure the accurate injection of hydrate inhibitors such as methanol and ethylene glycol.
Another example in the GoM is Petrobras' Cascade and Chinook fields, where Emerson's Roxar subsea multiphase meters are working alongside sand erosion and pressure and temperature sensor systems. The systems are working together intelligently, helping Petrobras meet challenges such as sand erosion and other threats to subsea infrastructure as well as ensuring each well is operating at its peak potential through the multiphase meters.
The final example is from Statoil's Heidrun field on the Norwegian Continental Shelf, where, according to the Norwegian Petroleum Directorate, "continuous efforts are being made to find new methods to increase oil recovery."
While the field does not include Emerson's multiphase meters, it does make extensive use of the company's intrusive corrosion probes and intrusive sand/erosion probes and also has a few locations with combined corrosion and sand/erosion probes to track sand damage and corrosion.
With a recent increase in sand production in the field, Emerson has been working with Statoil to increase the field's sand monitoring capabilities through a new sand management module. The module allows Statoil to respond faster to changes in sand production conditions and establish maximum sand-free production rates for production optimization. A common software platform also allows the operator to monitor and manage both intrusive and nonintrusive sand monitoring equipment and can have a crucial impact on production strategies.
A single, common software platform is vital to any intelligent field monitoring system. Data validation, flow assurance, sand and erosion, corrosion, simulation and production control, virtual flow metering, and hydrate
management all can be coordinated through Emerson's software platform, providing operators with a complete overview of their subsea assets.
Operating intelligently alongside other instrumentation
Today, a chief criterion of any of Emerson's instrumentation is its ability to operate seamlessly and intelligently alongside other instrumentation.
Downhole monitoring systems and HP/HT gauges, for example, are today deployed in production, injection, and observation wells in conjunction with the downhole instrumentation of highly complex multizone intelligent wells.
Such systems also are working closely with subsea corrosion sensors that help prevent subsea leakages, subsea valve actuators that allow for the rapid isolation of wells while reducing the size and weight of the subsea templates, and subsea acoustic sand monitors that enable the operator to immediately respond to increases in sand production.
Furthermore, recent developments in flow systems that now can generate multiphase flow measurements from downhole in the well will ensure a close link with other downhole solutions, with the Roxar Intelligent Downhole Network (IDN) acting as a unifying platform.
The IDN allows operators to install up to 32 instruments on a single cable, all of which provide input to manage a whole range of production wells or separate zones simultaneously. In this way, the intelligent network can act as a hub for downhole choke position indicators, future measurement devices, and third-party sensors and for the transmission of power and data – a subsea intelligent network in action.
As operators' subsea operations continue to grow and as the need for increasing recovery rates become ever more pressing, delivering improved subsea intelligence and integration into reservoir monitoring is likely to remain a key operator focus.
Finally, the whole is proving to be greater than the sum of its parts in intelligent subsea monitoring.