The field development plan includes the total layout of the field. The total layout is first divided into pieces, building blocks. With a Multi Criteria Analysis the three best concepts are identified and further analysed to before choosing the the final concept.

6.1. Three Concepts

This section presents the 3 best concepts from the MCA.

6.3.1 Concept A: Jacket at 100 meter water depth

Concept  A comprises of a subsea system, tied back to a steel platform that is located 25 km west of the field. The water depth at the location of the proposed platform is 100 m, which is significantly shallower compared to the 250 m water depth at the location of the field. The flow is processed and exported to the NCS2 pipeline via a two-phase pipeline.

Offshore-Jacket-and-tie-in

Key Risks: Because both the flowlines and the export pipeline are very long, flow assurance problems can occur. Another risk is that in case of territorial dispute and armed conflict, the assets can not be moved.

Advantages Disadvantages
Well-established technology
High local content
Subsea tieback – Flow assurance
Hard to decommission
Wet tree (maintenance difficult)

6.3.2 Concept B: Gravity base structure at 40 m water depth

Concept B comprises of a subsea system, tied back to a GBS that is located 70 km for the field at water depth of 40 m. The GBS has storage capacity of 300’000 bbl. Oil and gas are separated. Gas is exported to the shore via a new built 300 km gas pipeline. Oil is offloaded to shuttle tanker.

offshore-gravity-base-platfrom

The pipeline and flowlines are very long, so flow assurance problems can occur.  Another risk is that in case of territorial dispute and armed conflict, the assets can not be moved.

Advantages Disadvantages
Well-established technology
Oil storage
High local content
Can serve an expansion strategy (easy to increase topside weight)
Subsea tieback – Flow assurance
Wet tree
Decommissioning unproven technology

6.3.3 Concept C: FPSO

The third option is an FPSO in combination with subsea wells. The production liquids are comingled and finally brought up to the FPSO via risers. The subsea facilities are divided into drill centers with well clusters that are connected by manifolds. The flowlines and risers then transport the hydrocarbons to the FPSO.

When producing hydrocarbons the oil, gas and residuals are separated. The oil is offloaded to shuttle tankers after initial storage on the FPSO. The gas is transported through a pipeline.

offshore-subsea-development-with-FPSO

Key risksThe first key risk for the FPSO concept is just like the other concepts flow problems for the long distance pipeline. The FPSO will be somewhat less resistant to typhoons. However, a disconnectable turret can be used to eliminate this drawback.

Advantages Disadvantages
Well-established technology
Reusable
Decommissioning easy
Disconnectable
Subsea tieback – Flow assurance
Wet tree
Low local content

 

6.4. Economic Evaluation

An economic analysis was conducted to assess the three concepts. The results are shown in the tables below

  Jacket GBS FPSO
NPV (@10%DC) 700.27 542.10 714.94
VIR 0.36 0.23  0.42
UTC (gas)  2.50 2.63 2.65
IRR 16.8% 14.7% 17.9%

Table 1 Economics 3 concepts compared

It is clear that the FPSO has the highest NPV, which means the most profitable. However, investigations from PVN show that in the future the market labor costs and consumables’ cost, might drastically increase. In other words, the OPEX will increase. For the next economic analysis the labor costs increases every year with more than 10%, the result is show in table XXXX.

  Jacket GBS FPSO
NPV (@10%DC) 659.75 509.47  662.16
VIR 0.34 0.22  0.39
UTC (gas)  2.60 2.72 2.79
IRR 16.6%  14.5% 17.8%

Table 1 Economics 3 concepts compared with rising OPEX

In this case the FPSO still has the highest NPV of the three concepts.

6.5 Final concept choice

The final concept is chosen taking the MCA, key risks and the economics into consideration. The final concept chosen is the FPSO.

The main reasons for choosing an FPSO are as follows

  • Highest profits (highest NPV)
  • Flexibility (Removable in case of political issues, and it can incorporate nearby fields)
  • Production flexibility (In case of low scope of recovery, the FPSO can later used elsewhere)
  • Future possibilities (The FPSO can be used after the current field is depleted)