This multiauthor review article aims to bring readers up to date with some of the current trends in the field of process analytical technology (PAT) by summarizing each aspect of the subject (sensor development, PAT based process monitoring and control methods) and presenting applications both in industrial laboratories and in manufacture e.g. at GSK, AstraZeneca and Roche. Furthermore, the paper discusses the PAT paradigm from the regulatory science perspective. Given the multidisciplinary nature of PAT, such an endeavour would be almost impossible for a single author, so the concept of a multiauthor review was born. Each section of the multiauthor review has been written by a single expert or group of experts with the aim to report on its own research results. This paper also serves as a comprehensive source of information on PAT topics for the novice reader.

Offshore deepwater discoveries have driven the development of new compactseparation technologies, a core aspect of subsea processing. Compact separatorsare much smaller than conventional separators and have the potential tosignificantly reduce capital expenditure for deepwater developments. Unfortunately, reducing the size of separators generally reduce the separationperformance and the robustness to handle fluctuations in flow rate andcomposition. It is therefore essential to find an acceptable balance betweenthe realized reduction in overall capital expenditure and reduced tolerance tofluctuating conditions. To maximize the economics of a subsea development, itis important to understand how the technology selection impacts performance, risks, costs, and ultimately the attractiveness of deepwater subsea processing. Proactive technology screening and qualification are required. This paperpresents one of several ongoing joint industry projects to develop and screenseparation technologies for deepwater applications, the DEMO 2000 project: NextGeneration Deepwater Subsea Gas-liquid Separation System. An overview ofavailable technologies for separation in deep water is disclosed, includingcyclonic separators, compact gravity-type separators, and slug dampeningtechnologies. Their characteristics, typical performance and maturity level arediscussed. Finally, the program activities are explained and some highlightsfrom the separation test program are shared. Introduction Value Drivers for Subsea Gas-liquid Separation In recent years, subsea processing, and more specifically subsea separation, has been recognized as one of the most promising technology developments in theoffshore industry. With the recent success at Perdido [Ju et al., 2010], Parquedas Conchas (BC-10) [Iyer et al., 2010; Deuel et al., 2011], and Pazflor[Eriksen, 2012], subsea separation is attracting interest from industry becauseof its ability to increase production, enhance recovery, and improve fieldeconomics on a commercial scale. Subsea separation is, in general, stillconsidered an emerging technology area; therefore the benefits and capabilitiesmust be clearly demonstrated to infuse acceptance and confidence as thepreferred development option. McClimans and Fantoft [2006] and Di Silvestro etal. [2011] have presented a detailed review of the value drivers for subseagas-liquid separation, which is the topic of this paper. In summary, subseagas-liquid separation has proven to provide strong business incentives withenabling capabilities, including (i) more efficient liquid boosting, (ii)longer range gas compression from subsea to onshore, (iii) cost efficienthydrate management, (iv) effective riser slug depression, (v) and access tochallenging field developments that otherwise would be abandoned or notdeveloped (due to their remote location, harsh conditions, longer tie-backrequirements, or low reservoir drive). The main drivers are discussedbelow.

The separation process is the heart of the offshore production system. Conventional technology requires massive equipment to allow for required separation of oil, gas, water and sand. Most separation equipment is based on gravity separation principles that require larger retention times and low fluid velocities. These separators have over several years been subject to further development by introduction of new separation principles. Advanced separator internals have been an important contributor in this respect. During the last decade, Inline Separation Technology has successfully been introduced to several applications. Inline Separation is separation in pipe segments instead of within large vessels. Especially separation by use of cyclonic forces has been important. Inline technologies for separation of gas and liquid, oil and water as well as sand from liquid and multiphase streams have been developed and are already used extensively in retrofit applications to increase the performance and capacity of existing offshore production systems. As the inline technology matures, total production systems can be developed based on use of inline separation technology. This will allow for substantially more compact and cost efficient field developments. It will also enable new applications, such as heavy oil and deepwater subsea applications, which are not feasible to develop with conventional technology. This paper gives an overview of the inline separation technology and how this technology can be used to make improvements to offshore production system designs.

Summary ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program that included performance testing of an inline electrocoalescer device supplied by FMC Technologies (FMC). This paper will summarize the results from these performance tests. Although heavy oil has been processed onshore successfully for many decades, processing heavy oil in deepwater, subsea, or Arctic fields is extremely challenging. One key challenge is oil/water separation, in which physical separation is constrained by the high viscosity of the crude and the narrow density difference between oil and water. Installing conventional electrostatic coalescers or dehydrators is often not economical or is impractical at remote locations. As part of ExxonMobil's subsea program, several different separation technologies have been investigated and tested that could enable development of these fields. One example of such a technology is an inline electrocoalescer device. An inline electrocoalescer device enhances the coalescence of water droplets dispersed in emulsified oils. This technology has the potential to improve the performance of the downstream oil/water separator considerably. By applying an electrical field to an oil/water mixture, the dispersed water droplets become polarized and reorient themselves in the electrical field. As these water droplets approach one another, attractive forces between the individual water droplets lead to coalescence. Larger water droplets that can be separated faster and more easily in the downstream separation equipment are formed. Such a device can be used to increase the throughput, performance, and reliability of existing oil-processing systems, while reducing the energy consumption and/or use of chemical demulsifiers. In new processing systems, either subsea or topside, deployment of such a device has the potential to significantly reduce the size and weight of the downstream separation equipment, thereby lowering the overall capital expenditure. The results presented in this paper are from performance tests that have been carried out on an inline electrocoalescer device at FMC's testing facilities in the Netherlands, with EMURC's involvement. Extensive testing was executed with both medium and heavy crude oils. The operating temperatures were varied in a range representative for subsea processing applications, where heating of the process fluids is difficult. Thus, the performance of the inline electrocoalescer device was evaluated over a range of oil viscosities. Water-in-oil concentration, flow velocity, upstream shear, and electrical-field strength were also varied to investigate their effects on the performance of the inline electrocoalescer device. The results demonstrate that the unit is able to deliver high preconditioning performance to medium- and heavy-crude-oil emulsions, provided that the appropriate process conditions and electrical settings are used.

Several fields on the Norwegian Continental Shelf are in the decline phase with an increasing production of water and gas, often in combination with reduction in production pressure. The available area for installation of new equipment on the platforms is often limited, and it is important to minimize both the operational and capital costs. Compact, inline separation technology could be a key technology for mature fields, and also for subsea fields at large water depths where the weight is critical. Statoil has identified inline separation as an important technology to increase the oil recovery at brown fields. Due to low foot print and low operation cost the technology could be suitable to increase and prolong water production from the reservoir. The technology would also make it easier for tie-in of new fields at existing installations. To utilize the technology there is a need for both inline gas/liquid and inline oil/water separation (dewatering). Statoil has been carrying out a qualification program to develop inline equipment for dewatering. The project has been a co-operation between Statoil and FMC Separation Systems, and has been carried out in the period 2008 -2012. The technology is based on cyclonic separation devices with low or moderate pressure drops. An extensive development program has been performed with different geometries for the inline separators, including Computational Fluid Dynamics (CFD) study and testing activities both in laboratory flow loops and at the Gullfaks field. A full scale DeWaterer with 20 liners has been tested to investigate the effect of gas present. The operational window of the inline technology has been established, and the results show that gas and water can be efficiently separated from the well stream. The results will be presented in the paper. The conclusion from the work is that inline technology has a large potential to replace or reduce the size of conventional gravity separators topside, and also to be utilised for subsea separation at large water depths. The qualification work demonstrated that the dewatering technology for the Gullfaks application could separate water with a water quality of less than 500 ppm Oil-in-Water at low pressure drop (1 bar). Based on the qualification work the technology is considered ready for deployment in Statoil.