1         Introduction

This case study presents field development work performed for Hasselmus project using SFACE based on publicly available data and deduced data. The objective of the study is to identify the SURF and SPS CAPEX of the project. This follows a bottoms-up approach, where all the system calculations are performed, equipment configured and costs calculated based on detailed MTO & offshore operations sequence.

This complete exercise after data collection took less than 1 hour of effort in SFACE.

2         Facts about Hasselmus project

The Hasselmus gas discovery is located on the western edge of the Trøndelag platform in the Norwegian Sea, 7 km northwest of the Draugen platform, in production license 093. The development concept is a single subsea well with direct tie-back to the Draugen platform. Production start-up is planned in Q4 2023 with plateau gas production of more than 4,400 barrels of oil equivalents per day gross [1].

No of production trees 1
Flowline length 9km
Flowline type Pipe in Pipe
Water depth 250 m
Production type Gas
Production rate 4400 boe/d = 0.7 Msm3/d=24.7 MMSCFD
Bottom hole temperature 70 °C [4]
Bottom hole pressure 240 bara [4]
SURF+SPS capex 50 – 150 MUSD [3]


Field layout, credit OKEA [2]

2.1        Assumed data

Flowing wellhead pressure 180 bara
Shut-in wellhead pressure 200 bara
Flowing wellhead temperature 50 °C
Sand rate 0.02 lb/MMSCF
Topside arrival pressure 100 bara
Pipeline size

8” ND, 190mm ID, Uvalue 1.0,

CS pipeline + NA625 cladding

Umbilical length 7km


3         SFACE model

The model consists of process system only, controls & chemical distribution is not covered.

3.1        Flow assurance calculations

The first set of simulations were performed with low arrival pressure (~ 20 bara), which resulted in freezing conditions downstream the subsea production choke. From there it was identified that early life arrival pressure has to be ~100 bara, requiring additional choking topside.

3.2        Preliminary flowline design

The cross section and other relevant details for the flowline is presented in the table below. It was identified that 8” ND with SCH60 for flowline inner pipe and 12” ND with SCH60 for outer pipe is required.

Flowline Name Gas Flowline Riser
Length [m] 9000 300
Water Depth [m] 250 250
ND [inch] 8 8
OD [mm] 219.1 219.1
SCH 60 80
Selected_WT [mm] 10.3 12.7
Req_WT [mm] 8.9 11.2
Req_WT_internalPressure [mm] 8.4 10.7
Req_WT_externalCollapse [mm] 4.2 4.2
Req_WT_propBuckling [mm] 8 8
Reeling_WT [mm] 6.6 6.6
Material X65 X65
Clad_Thickness [mm] 3 3
Clad Material SS316L SS316L
Coating_Thickness [mm] 3 3
Pipeline Coating 3LFBE_PP 3LFBE_PP
insulationReq Yes Yes
insulationType Pipe in Pipe Pipe in Pipe
Insulation thk [mm] 13 14
CarrierPipe_ND [inch] 12 12
CarrierPipe_OD [mm] 323.8 323.8
CarrierPipe_SCH 60 60
CarrierPipe_Material X65 X65
CarrierPipe_Selected_WT [mm] 14.3 14.3
CarrierPipe_Req_WT_externalCollapse [mm] 6.2 6.2
CarrierPipe_Req_WT_propBuckling [mm] 11.8 11.8
CarrierPipe_Reeling_WT [mm] 11.8 11.8
Achieved UValue [W/m2-K] 0.72 0.74
Required UValue [W/m2-K] 1 1


3.3       PLET results

Main results for PLET piping are shown in below table.

Pipe_name mainHeader
ND [inch] 6
OD [mm] 168.3
Selected_WT [mm] 7.1
Req_WT [mm] 6.4
Material SDSS-S32750
Sand Mass Rate [kg/s] 2.6E-06
Sand Mean Size [micron] 50
Inlet_Pressure [bara] 122.6
Inlet_Temperature [°C] 36.7
Pipe erosion rate [mm/yr] 4.7E-08
Bend erosion rate (GF2.0) [mm/yr] 4.8E-06
Bend erosion rate (GF4.0) [mm/yr] 9.5E-06
Tee erosion rate (GF2.0) [mm/yr] 9.4E-07
Tee erosion rate (GF4.0) [mm/yr] 1.9E-06


3.4        Subsea Xmas Tree (XT) schematic

Automatically generated by SFACE in native CAD format.

3.5        Capex results


  • 35% margin on equipment cost to arrive at equipment prices
  • Standard project management and engineering
  • All equipment pre-qualified


  • Umbilical and subsea controls distribution systems (equipment and installation)
  • Topside controls equipment
  • Capital spares

Estimated SURF + SPS capex of 70.1 MUSD.

3.6        Concluding remarks

The estimated capex of 70.1 MUSD presented above is without the umbilical and controls distribution equipment. The cost for typical production umbilical & controls distribution would be approx. 10-15 MUSD, which will bring the total capex to 85 MUSD.  All this estimate also assumes standard project management and engineering.

The capex estimated by SAFCE is within the capex bracket available in public domain. Also, it should be noted that all the results presented here were obtained with less than 1hour work. This demonstrates the effectiveness of SFACE.


4         References