An Integrated Approach to Flow Assurance

Flow Assurance is an ever evolving discipline that aims to address a number of threats related to design and operation of any system that conveys hydrocarbon fluid, with consideration also given to ancillary systems, which may include injection or artificial lift. 

​Solids deposits such as wax, hydrates or asphaltenes, and problems associated with multiphase flow behavior, such as slugging, are highlighted as being some of the main challenges facing developments and operations in the industry today, see Figure 1.

In addition, issues such as corrosion and erosion can affect the integrity of the system, particularly if velocities and shear rates are not managed, while sand transport/deposition can exasperate these issues.

Fluid rheology can impact the thermo-hydraulic performance of a system, as too can emulsions, which lead to elevated viscosities at increased water-cuts until the inversion point is reached.
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Although less common, crude oils with a high total acid number (TAN) can lead to the formation of naphthenates, which can foul flowlines and processing equipment.

Figure 1 - Flow Assurance Threats

Furthermore, formation water chemistry and pressure maintenance of the reservoir can lead to a variety of severe scaling issues, while souring can be a major concern and dramatically impact system design and cost.

​I​n order to address the challenges associated with transporting live production fluid, particularly from the wellbore to the host, an integrated approach is required to consider all aspects of the system, so that the production flow path can be maintained over the life of field. 

In general, the core flow assurance strategies are well understood, and vary as a function of developing technology e.g. electrically heat traced pipe-in-pipe. Often, ​a primary strategy will be supplemented by secondary strategies to facilitate safe-out of a system from the various modes of operation. To be the most effective, strategies need to be applied early in the design phase while also giving consideration to material selection and monitoring at key locations, since late additions can have significant impact on cost and schedule, or may be omitted completely.

Figure 2 - Flow Assurance Interfaces

But while strategies may be field specific, the approach to Flow Assurance can be differentiator between success and failure. ​It has to be about more than placing a dependency on steady state and transient simulation tools, which at the end of the day, really are there to facilitate the decision making process. We really need to understand the system as a whole, and the range of key interfaces from subsurface, to hardware and installation, see Figure 2.

All things considered, flow assurance becomes part of the bigger picture, and cannot be performed in isolation, or after the fact.

An integrated approach to Flow Assurance can​ be summarized by the Venn Diagram in Figure 3. With any type of Flow Assurance study, missing a piece(s) from the diagram will create a sub-par product which can lead to unnecessary risk in how the system is designed and operated. From solid deposition in a production system to unwanted liquid drop-out in an export system, it's this multi-pronged effort that creates value for the customer, and helps to generate and maintain operations efficiencies, which at the end of the day, is what we're trying to accomplish.

Figure 3 - Flow Assurance Venn Diagram

​There is certainly an impetus on being risk tolerant rather that completely risk adverse, where layers of conservatism can create cumbersome solutions that penalize any given project.​ But that's more about identifying the threats and strategies, and understanding the various drivers and interfaces, versus assumed risk from not applying an integrated approach.

In understanding the system as a whole, and applying learnings and experience from operations and previous projects, representative simulation models can be created and used to produce the necessary deliverables while minimizing man-hours and costly re-runs. It's a result that everybody should be looking to attain.