Dealing With Uncertainty—Impact of Scaling Prediction on Concept Selection for Deepwater Production Systems

Concept selection and initial design of deepwater subsea production systems is an exercise whose findings can have a profound impact on evaluation of the commercial viability of a discovery. Although detailed design comes later in the process, the decisions made at this early stage of a project will generally provide the template that is carried through to construction. Scale management can be a significant factor in deciding the outcome of the concept selection phase, particularly for fields that are expected to require seawater injection at some stage in their design life. At this early stage of the project it is common for fluids from only one or two exploration wells to be available and where water samples are often not available, are heavily contaminated, or have been gathered from locations away from the main production targets. This paper outlines the difficulties faced when evaluating the various scale management techniques available to deepwater operators at this early stage in the project design process and in providing fit for purpose design recommendations that are not overly conservative but that still account for the risk posed by having only limited supporting information available. An approach is presented that addresses these risks and uncertainties by applying scale modeling along with a simple probabilistic method to support the selection of appropriate scale management strategies for deepwater subsea fields. Several comparative examples for deepwater projects in the Gulf of Mexico are provided to explain the different outcomes that can result from this process.