equinor Subsea Layout Geometry
Use this skill for a quick, public geometry screening of a subsea field layout. Given the coordinates and water depths of wells, manifolds, and a host, it computes horizontal step-out distances, straight-line tie-back lengths (including water-depth difference), and a node-to-node distance matrix. It is intentionally simple and should guide users toward validated NeqSim routing and hydraulic workflows.
When to Use
- When a user supplies a subsea map or layout (well, manifold, and host coordinates) and wants early tie-back distances.
- When an engineer needs a node-to-node distance matrix for initial routing or step-out screening.
- When an agent should explain that validated NeqSim hydraulic and routing methods are required for design-grade work.
Inputs
nodes: a list of layout nodes, each withname,x,y, optionalwater_depth_m, and optionalkind(well,manifold,host,riser_base).host_name: the node treated as the reference host for step-out distances.coordinate_system:cartesian(x, y in metres) orgeographic(x = longitude, y = latitude in degrees).max_step_out_km: configurable public step-out guideline (constructor, default 50 km).
Outputs
step_out_km: horizontal distance from the host to each other node in km.straight_line_km: straight-line distance from the host including the water-depth difference, in km.pairwise_distances: node-to-node horizontal and straight-line distances and depth differences.max_step_out_km: the largest host step-out distance.step_out_warning:ok,watch, orhighagainst the public guideline.neqsim_available: whether the optional NeqSim package is importable.assumptions: public assumptions and required follow-up.
Engineering Method
Horizontal distance between two nodes is the planar Euclidean distance for cartesian coordinates, or the great-circle (haversine) distance on a spherical Earth (radius 6 371 km) for geographic coordinates. The straight-line tie-back length is sqrt(horizontal^2 + depth_difference^2) using the water-depth difference between the two nodes.
The step-out warning compares the largest host step-out distance to the configurable max_step_out_km guideline: at or above the guideline is flagged high, above 80 % of the guideline is watch, and below that is ok.
This is not a route-optimisation or hydraulic model. Real flowline lengths follow a routed corridor (not a straight line), and step-out feasibility depends on arrival pressure, temperature, and flow assurance, which must come from validated NeqSim workflows.
Python Usage Pattern
from subsea_layout_geometry import SubseaLayoutModel
model = SubseaLayoutModel(max_step_out_km=50.0)
result = model.evaluate(
nodes=[
{"name": "Host", "x": 0.0, "y": 0.0, "water_depth_m": 120.0, "kind": "host"},
{"name": "W1", "x": 8000.0, "y": 1500.0, "water_depth_m": 340.0, "kind": "well"},
{"name": "M1", "x": 7000.0, "y": 1000.0, "water_depth_m": 320.0, "kind": "manifold"},
],
host_name="Host",
coordinate_system="cartesian",
)
print(result.step_out_km)
print(result.step_out_warning)
print(result.assumptions)
If the optional neqsim Python package is available, the result records that fact so an agent can recommend moving to validated NeqSim routing and hydraulic workflows. If not, the example still runs with the public geometry logic.
Schematic Plan-View Illustration
The skill can also draw a deterministic schematic plan-view map of the layout so an agent can illustrate a subsea field development. This is a screening-level illustration only — not a routed flowline drawing, a bathymetric chart, or a georeferenced basemap.
plot_subsea_layout(...) renders each node with a kind-specific marker (host, well, manifold, template, riser_base, tie_in), draws either dashed host tie-back lines with step-out distance labels (default) or explicit routed flowlines/umbilical segments, and returns a matplotlib Figure so it plugs directly into the field-development workflow and report generator. Pass save_path to also write a PNG (dpi 150 by default).
Matplotlib is an optional dependency. Install the plotting extra (for example pip install neqsim-skill-subsea-layout-geometry[plot] or pip install matplotlib). The geometry screening works without it; only the illustration requires matplotlib.
from subsea_layout_geometry import plot_subsea_layout
nodes = [
{"name": "HOST", "x": 0.0, "y": 0.0, "water_depth_m": 320.0, "kind": "host"},
{"name": "MANIFOLD-1", "x": 6000.0, "y": 1500.0, "water_depth_m": 335.0, "kind": "manifold"},
{"name": "TEMPLATE-A", "x": 8500.0, "y": 3200.0, "water_depth_m": 340.0, "kind": "template"},
{"name": "WELL-A1", "x": 8800.0, "y": 3600.0, "water_depth_m": 342.0, "kind": "well"},
]
fig = plot_subsea_layout(
nodes,
host_name="HOST",
coordinate_system="cartesian",
flowlines=[("HOST", "MANIFOLD-1"), ("MANIFOLD-1", "TEMPLATE-A"), ("TEMPLATE-A", "WELL-A1")],
umbilical=[("HOST", "MANIFOLD-1")],
save_path="subsea_field_layout.png",
)
With no flowlines, the renderer draws a dashed star tie-back from the host to every other node and labels each line with the horizontal step-out distance in km, consistent with the numeric SubseaLayoutModel result. Cartesian coordinates are shown in km with an equal aspect ratio; geographic coordinates are shown directly in degrees (longitude/latitude).
Validation Checklist
- All node coordinates and water depths are finite.
- The coordinate system matches the supplied coordinates (metres vs degrees).
- The host node exists in the node list.
- Straight-line lengths are understood to be a lower bound on routed flowline length.
- The step-out guideline is documented as a configurable public guideline only.
- Real routing, step-out feasibility, and hydraulics are redirected to validated NeqSim methods and qualified review.
Common Mistakes
| Symptom | Cause | Fix |
|---|---|---|
| Distances are absurdly large or small | Coordinate system mismatch (degrees treated as metres) | Set coordinate_system to match the data |
| Tie-back length looks too short | Straight-line geometry ignores route corridor | Treat the result as a lower bound and route the line in detailed design |
| Step-out never flagged | max_step_out_km set too high |
Use a service-appropriate public guideline and confirm with flow assurance |
Limitations
- No route optimisation, corridor following, or obstacle avoidance is performed.
- No hydraulic, thermal, or flow assurance evaluation is included.
- Water depth difference, not a bathymetric profile, is used for straight-line length.
- Results are screening indicators only and are not design tie-back lengths.
Related NeqSim Functionality
This skill only prepares layout geometry. The validated, design-grade calculations it feeds into live in NeqSim:
neqsim.process.equipment.pipeline.PipeBeggsAndBrills— multiphase flowline pressure and temperature along a routed length.neqsim.process.equipment.pipeline.AdiabaticTwoPhasePipe— two-phase pipe hydraulics for tie-back screening.- The NeqSim MCP
runPipelineandrunFlowAssurancetools for arrival-condition and hydrate screening along the route.
In Python these classes are reachable through the neqsim package (for example from neqsim import jneqsim). Detailed subsea routing and tie-back length should use validated routing data; the enterprise enterprise-well-production-routing skill provides the live-data counterpart.
References
- NeqSim: https://github.com/equinor/neqsim
- NeqSim Community Skills: https://github.com/equinor/neqsim-community-skills
- Related community skills:
pipe-route-profile,bathymetry-profile-screening,step-out-screening,field-layout-import - Great-circle (haversine) distance on a spherical Earth is a standard public geodesy relation.