Maximising Deepwater Asset Value with Subsea Processing: Employing Synergy on Subsea Fluid Sampling
Authors: Abili Nimi , Duclocher Fabien Dominique , Citi Gianfederico 
Published: March 2015

The acquisition of representative fluid samples from deep and ultra-deepwater field development is crucial for the correct evaluation of oil reserves and for design optimisation of subsea production and processing facilities. Due to regulatory requirements for fiscal allocations, samples collected from topside facilities do not represent the fluid being measured, occasioned by chemical injection downstream the Subsea Multiphase Flowmeter (SMPFM) and possible liquid separation / hold-up, which further complicates these challenges. However, the issue of subsea intervention and transportation of fluid samples present another significant challenge coupled with the cost impact and risk to the subsea environment. Therefore, the synergy to acquire representative fluid samples to determine the right window to employ subsea processing must be sort to realise value on field development projects in maximising oil recovery.

Applications

Acquiring representative fluid samples play a key role in the design optimization of field development, to enable efficient reservoir performance management. Inaccurate and unreliable fluid characterization leads to high uncertainties in hydrocarbon volume estimates, thus negatively impacting ultimate recovery predictions and hence the asset value. With the virtual fluid sampling model developed from a 'Transient Multiphase flow' program, every single fluid component was accounted for throughout the calculation, enabling simulation of scenarios such as start-up and blowdown with a high level of detail and accuracy. Remote Opperated Vehicle (ROV) deployed fluid sampling also play a key role in the representative fluid sample capture at the wellhead or subsea tree for laborary analysis of PVT and fluid compositions.

Results, Observations, and Conclusions

Results from the developed virtual fluid model demonstrates the capability in improving understanding of well flow stream, with a proactive and cost effective fluid sampling operations. Another benefit is the value it adds in deciding when to employ subsea processing to manage water breakthrough as the field matures. This can be achieved through efficient processing of the fluid delivered to the topside facilities or for water re-injection to the reservoir. The acquired results from a deepwater field case study, establish the fact that the virtual model can accurately predict the fluid compositions at the well source and production flowlines. Therefore, this has enabled the development of a predictive tool for advanced subsea intervention operations to test and monitor reservior conditions for the life-of-field.

Significance of subject matter

The developed virtual fluid model does not only bridge the gaps in subsea fluid sampling, it also maximizes value by adding analytical techniques to check and validate present measurement methods of obtaining fluid properties during production well tests. Thus, the virtual model provides a new application and opportunity to optimize individual well testing for Enhanced Oil Recovery (EOR). The present paper explores the synergy in successful application of subsea fluid sampling to maximize value with subsea processing on deepwater field developments.