Imported from equinor/neqsim-community-skills (skills/subsea/surf-field-layout-design/SKILL.md). Install upstream with npx skills add equinor/neqsim-community-skills --skill surf-field-layout-design. Copyright stays with the author.

SURF Field Layout Design

Use this skill to turn a well count, a reservoir footprint and a water depth into a placed and routed subsea layout: drill centres, wells, Xmas trees, templates and manifolds, PLEMs, riser bases, the host, and every flowline, riser and umbilical between them — each line sized on velocity and each item carrying a latitude and longitude so the result drops straight into a map or a GIS.

It is the design counterpart to neqsim-subsea-layout-geometry, which screens a layout that already exists. Use this skill first to create the layout, then that skill to screen step-outs, and neqsim-pipe-route-profile to put the routes on a real seabed profile.

When to Use

• A concept study needs a subsea architecture before any layout drawing exists.
• The number of drill centres, templates and Xmas trees must follow from the well count and the slots per template.
• The host has to be placed relative to the field, and the riser base with it.
• A flowline architecture must be chosen: a round-trip-piggable dual loop, one dedicated line per drill centre, or a daisy chain.
• Flowline, riser and injection-line sizes are needed at a screening level.
• Total flowline, riser and umbilical lengths are needed for a SURF cost estimate.
• The layout must be georeferenced — on a licence block, on a map, as GeoJSON.
• A production-network or flow-assurance model needs node positions and segment lengths.

Do not use it for detailed routing, crossing design, on-bottom stability, free-span, expansion, installation or mooring analysis.

Inputs

Rates are actual volumetric rates at the flowing condition, not standard volumes. Convert a standard rate with the formation volume factor before passing it in, or the sizing is wrong by that factor.

Outputs

• nodes — wells, Xmas trees, templates/manifolds, PLEMs, riser base and host, each with a tag, local east/north, latitude, longitude and water depth.
• lines — every flowline, injection line, umbilical and riser, with its service, type, endpoints, length and selected size.
• summary — drill-centre and tree counts, architecture, maximum step-out, and total flowline, umbilical and riser lengths.
• to_geojson() — a WGS84 FeatureCollection of points, lines and the reservoir outline, ready for any map or GIS.
• warnings and assumptions — what was assumed and what a reviewer must check.
• render_field_illustration(...) — a presentation-grade reservoir-to-host cutaway carrying the study's headline numbers (see below).

Presentation Illustration

plot_reservoir_3d is the engineering view — labelled axes, a schematic reservoir box. render_field_illustration is the communication view: the block diagram for a decision-gate slide. It draws the sea, the water column, the seabed, the subsurface, a real gridded structural horizon coloured by depth, every well from its tree to its drain, the flowlines, the host and its risers.

The point of the function is that the picture and the analysis cannot drift apart. Headline numbers are passed as KeyFact objects, each carrying the calculation that produced it, and are rendered as a grouped callout column. If a number changes in the model it changes on the slide, and the slide says where it came from.

from surf_field_layout_design import (
    KeyFact, Seabed, horizon_from_model_grid, render_field_illustration,
)

horizon = horizon_from_model_grid(
    top_surface_values,            # flattened reservoir grid, x fastest
    nx=70, ny=30, dx_m=100.0, dy_m=100.0,
    origin_east_m=-5650.0, origin_north_m=0.0,
    axis_bearing_deg=78.2,         # true bearing of the model +x axis
    contact_depth_m_tvdmsl=3054.8, # draws the hydrocarbon closure
    attribution="OPM Flow structural model",
)

render_field_illustration(
    layout, well_paths, "field.png",
    horizon=horizon,
    seabed=Seabed(east_m=e, north_m=n, depth_m=d, attribution="EMODnet DTM"),
    key_facts=[
        KeyFact("Gas initially in place", "6.12", "GSm3",
                "OPM Flow structural model", "RESERVOIR"),
        KeyFact("Flowline size", "8 in", "",
                "46% of the API RP 14E limit", "SURF"),
    ],
    title="Brime / Nokken to Gullfaks C",
)

horizon_from_model_grid rotates a reservoir model grid onto a true bearing using the same axis convention as the layout: for a field-axis bearing $b$,

$$ \text{east} = \ell \sin b + a \cos b, \qquad \text{north} = \ell \cos b - a \sin b $$

with $\ell$ along-axis and $a$ across-axis. Getting this backwards silently mirrors the field; the unit tests assert the along-axis run reproduces the requested bearing.

Open Map and Sea Data

geodata registers openly licensed sources and plans read-only requests. It never opens a connection of its own: execute returns the plan as a manifest unless the caller supplies its own fetch adapter, so the same code runs in a sandbox and on a connected workstation.

from surf_field_layout_design import plan_layout_data_package, execute, attribution_block

plan = plan_layout_data_package(west=24.0, south=73.0, east=26.0, north=74.0)
manifest = execute(plan)                       # offline: returns the plan only
manifest = execute(plan, fetch=my_read_only_get)   # connected: retrieves it
print(attribution_block(["emodnet_bathymetry", "sodir_factmaps"]))

Reproduce the attribution lines on any map you publish.

Norwegian blocks

quadrant_bounds("7324") returns the quadrant box, which is exact north of 62 degN: the label is the latitude of the southern edge and the longitude of the western edge, spanning one degree by two. block_bounds("7324/8") divides that into twelve 15-by-40-arc-minute blocks — but the numbering direction is a documented assumption, not a calculation, and the returned dictionary says so. Take the real position from the open Sodir wellbore layer and use the block box only for orientation.

Engineering Method

Drill centres. Wells of each service are grouped into templates of slots_per_template slots, and the resulting drill centres are spaced evenly over 70 % of the reservoir length along the field axis. Water injectors are offset down one flank and gas injectors up the other by injector_offset_km. This is geometry, not a sweep study.

Host and riser base. The host sits host_offset_km from the field centre on host_bearing_deg; the riser base PLEM sits riser_base_offset_m short of it on the reverse bearing. Riser length is the straight riser-base-to-host distance with a 25 % lazy-wave allowance.

Architecture. dual_loop runs two legs through the production drill centres in opposite order, giving a round-trip pigging loop. single_line gives one dedicated line per drill centre. daisy_chain runs one line through them all and is flagged as not round-trip piggable.

Line sizing. The smallest standard nominal size whose velocity stays under both the target velocity and the API RP 14E erosional velocity,

$$ v_e = \frac{1.22,c}{\sqrt{\rho}} $$

with $v_e$ in m/s, $\rho$ in kg/m³ and $c = 100$ for continuous service. Inner diameter follows a fixed diameter-to-wall ratio of 20; that is a screening geometry, not a pressure-containment design.

Python Usage Pattern

from surf_field_layout_design import design_surf_layout, plot_layout_map

layout = design_surf_layout(
    field_name="Example field",
    centre_latitude_deg=73.375,
    centre_longitude_deg=25.0,
    water_depth_m=400.0,
    producers=8,
    water_injectors=6,
    gas_injectors=2,
    slots_per_template=4,
    reservoir_length_km=6.0,
    reservoir_width_km=3.1,
    field_axis_bearing_deg=30.0,
    host_offset_km=2.5,
    host_bearing_deg=270.0,
    production_architecture="dual_loop",
    design_liquid_rate_m3_per_s=28500.0 / 86400.0,
    design_water_injection_rate_m3_per_s=20000.0 / 86400.0,
    design_gas_injection_rate_am3_per_s=0.63e6 * 0.012 / 86400.0,
)

print(layout.summary["drill_centres"], layout.summary["flowline_length_km"], "km")
plot_layout_map(layout, "layout_map.png")
open("layout.geojson", "w").write(json.dumps(layout.to_geojson()))

Handing the layout on

• Flow assurance and hydraulics. Each Line gives the endpoints, length and inner diameter that neqsim.process.equipment.pipeline.PipeBeggsAndBrills needs; take the elevation profile from neqsim-pipe-route-profile or an open bathymetry grid rather than the flat default.
• Production network. Drill centres map to a Mixer manifold and wells to WellFlow inflow, as in neqsim-production-network-routing.
• Cost. flowline_length_km, umbilical_length_km, riser_length_km and the tree, template and PLEM counts are the quantity take-off a SURF cost estimate needs.
• Screening. Feed the node list to neqsim-subsea-layout-geometry for step-out and tie-back distance checks.

Validation Checklist

• The field position comes from an open wellbore or discovery record, not from the block-grid assumption.
• Design rates are actual volumetric rates at the flowing condition.
• Every line size is inside the target velocity and the erosional limit, or the deviation is explained.
• The flowline architecture matches the pigging and shutdown philosophy.
• The seabed is a real bathymetry grid, not the flat default, before any route length or riser length is used for cost or hydraulics.
• The host offset respects the safety zone and the drill-centre envelope.
• Wall thickness has been replaced by a real pressure design.
• Every number on a published illustration is a KeyFact with its source, and matches the calculation it claims to come from.
• A qualified subsea engineer has reviewed the layout.

Common Mistakes

Limitations

• Screening geometry only: straight-line routes, no obstacle avoidance, no crossings, no corridor or approach design.
• Drill-centre placement is geometric spacing, not a well-placement or sweep optimisation.
• No on-bottom stability, free-span, expansion, buckling, installation, mooring or riser-response analysis.
• Wall thickness follows a fixed D/t ratio and is not a pressure design.
• Line sizing is a velocity check only; no pressure-drop, slugging, erosion-rate or thermal calculation.
• Met-ocean sources are registered but the host heading is not calculated.
• The illustration is a communication aid: well trajectories are screening geometry, the host is a glyph, and matplotlib's 3D engine does not depth-sort intersecting surfaces, so read positions from the data, not off the picture.
• No proprietary or confidential data is used.

Related NeqSim Functionality

The screening geometry this skill produces is meant to be replaced by real calculations. These are the classes that do it.

• neqsim.process.equipment.pipeline.RouteProfile — turns a survey into the mesh either pipe model wants. fromDepths handles the sign convention, withRiser appends the riser, resample gives a uniform mesh, and getLowPointKp returns the terrain-slug traps.
• neqsim.process.equipment.pipeline.TwoFluidPipe — mechanistic two-fluid flowline and riser hydraulics. Prefer it over PipeBeggsAndBrills for a wet-gas tie-back: the Beggs & Brill two-phase friction multiplier is extrapolated well below its calibration floor at low liquid fraction and over-predicts the pressure drop. Always assert isSteadyStateConverged() and getSteadyStateIterationsUsed() > 1.
• neqsim.process.equipment.pipeline.PipeBeggsAndBrills — correlation check. CalculationMode.CALCULATE_INLET_PRESSURE with setOutletPressure(...) solves the tie-back question directly: what inlet does the host's arrival pressure demand? Read the answer from getSolvedInletPressure().
• neqsim.process.mechanicaldesign.subsea.FlowlineSizeSelector — replaces this skill's velocity screen with a full API RP 14E candidate table. Evaluate it at the arrival condition, where the mixture is least dense.
• neqsim.process.equipment.subsea.SubseaWell.calculateShutInWellheadPressure — the static-column pressure that sets the flowline design pressure.
• neqsim.process.equipment.reservoir.WellFlow — well inflow at each tree.
• neqsim.process.mechanicaldesign.pipeline.DnvStF101PipelineDesignCalculator — replaces this skill's D/t screening geometry with a real pressure design.
• neqsim.process.mechanicaldesign.subsea.TiebackThermalDesign — sweeps wall thickness against insulation together, because the steel is part of the cooldown thermal mass: a thinner wall needs more insulation for the same no-touch time.
• neqsim.pvtsimulation.flowassurance.SurfCooldownAnalyzer — no-touch time. A fluid with no water reports NO_HYDRATE_RISK with an unbounded no-touch time, which is right for a dry gas and indistinguishable from a wet line whose file is missing water. Check isWaterPresent(), or setRequireWater(true) to make it a gate. Add water with EclipseFluidReadWrite.read(file, true), and never call setMixingRule after read (it wipes the file's BIC block).
• neqsim.process.mechanicaldesign.subsea.SURFCostEstimator — turns the quantity take-off into a CAPEX estimate.
• The NeqSim MCP runPipeline and runFieldEconomics tools.

Related Skills

• neqsim-subsea-layout-geometry — screens step-outs and tie-back distances for the layout produced here.
• neqsim-pipe-route-profile — turns the routes here into an elevation profile.
• neqsim-bathymetry-profile-screening — processes the open bathymetry grid this skill plans the request for.
• neqsim-production-network-routing — takes the drill centres and wells through manifolds and flowlines to an arrival pressure.
• neqsim-step-out-screening — checks the tie-back distance and arrival pressure.
• neqsim-reservoir-model-builder — supplies the well count and the plateau rate.
• neqsim-capex-opex-screening — turns the quantity take-off into a cost.

References

• API RP 14E, Design and Installation of Offshore Production Platform Piping Systems — erosional velocity.
• DNV-ST-F101 Submarine pipeline systems and DNV-RP-F109/F105 for the design checks this skill deliberately does not perform.
• EMODnet Bathymetry: https://emodnet.ec.europa.eu/en/bathymetry
• GEBCO: https://www.gebco.net/
• Norwegian Offshore Directorate FactMaps: https://factmaps.sodir.no/
• Natural Earth: https://www.naturalearthdata.com/
• Copernicus Marine Service: https://marine.copernicus.eu/
• MET Norway NORA3 hindcast: https://thredds.met.no/
• NeqSim: https://github.com/equinor/neqsim