Production Profile Optimisation

To be honest you don’t get many opportunities to challenge the production profile. Even though its not fixed, it is quite often treated as a frozen input in our FA model. However, if the study is still in Concept and/or the Client sees the benefits in slightly changing the profile, you may get the opportunity.

This was just the case in this example. As we were also looking at the economics, we could assess the effects of changing the production profile slightly to obtain the optimum economic solution.

The development consisted of two new WHPs tieing back to an existing CPP. A workflow was established to assess the effect of pipeline sizes on the overall project economics. At the heart of the workflow was a simple IPM model which would allow us to assess the change in production profile required so that smaller pipeline sizes could be utilized.

An initial line sizing was conducted and two pipeline sizes were examined for the longer pipeline to the CPP from Field A (12” and 16”). The effect of changing the pipeline size for Field B to Field A was investigated. From this a 16” Field A and 10” Field B and a 12” Field A and 10” Field B comparison was selected.

A life of field analysis was then performed on the two cases as shown below. It showed that the required reservoir for a 16” pipeline was less than or equal to the available reservoir pressure across the whole of field life. Whereas reducing the line size to 12” meant that the required pressure slightly exceeded the available pressure from Year 8 to Year 11. In a normal study this would have been the end and 16” would be selected. However given there would only be a small reduction in production required and it would be in Year 8 the economics may favour the reduced CAPEX and production deferment.

A simple IPM model was created (with the reservoir modelled as a tank) to deter mine the production profile which could be achieved with the small 12” pipeline. As can be seen below this results in a very minor reduction of the gas recoverable and hence when the economics was performed it was the optimum solution.

Optimising the production profile is not always possible, sometimes there are gas sales agreements in place and the penalties for not meeting the agreements fundamentally changes the economics. However, sizing your pipeline for operation many years later in the fields life, when the field is off plateau, is probably not the optimum design unless there are penalties.