Neqsim Reservoir Depletion Screening

Reservoir Depletion Screening

Use this skill for a quick, public screening of how a reservoir develops with time. Given a recoverable volume, an offtake rate, and an initial and abandonment pressure, it produces a year-by-year profile of reservoir pressure, cumulative production, recovery factor, water cut, and hydrocarbon/water rates. It is intentionally simple and should guide users toward the validated NeqSim SimpleReservoir tank model (runTransient) and the NeqSim MCP runReservoir workflow for real depletion behaviour.

When to Use

• When a user wants a first look at how reservoir pressure declines over field life.
• When an early production/decline profile is needed before a reservoir model exists.
• When an agent needs an upstream "reservoir vs time" feed for a production-routing or arrival-pressure screening chain.

Inputs

• fluid_type: gas or oil.
• initial_pressure_bara: reservoir pressure at start of production.
• abandonment_pressure_bara: pressure at which production stops (screening).
• recoverable_volume_sm3: recoverable hydrocarbon volume at standard conditions.
• offtake_rate_sm3_per_day: constant screening offtake (hydrocarbon) rate.
• years: number of years to simulate.
• time_step_years: time-step size (default 1.0 year).
• initial_water_cut_fraction: water cut at start (default 0).
• water_cut_rise_per_year: linear water-cut rise per year (default 0).

Outputs

• steps: per-step year, pressure_bara, cumulative_production_sm3, recovery_factor, water_cut_fraction, hydrocarbon_rate_sm3_per_day, water_rate_sm3_per_day, and depleted flag.
• final_pressure_bara, final_recovery_factor.
• plateau_years: years before production can no longer be sustained (or None).
• years_to_abandonment: first year the reservoir reaches abandonment (or None).
• depletion_warning: ok, watch, or high.
• neqsim_available: whether the optional NeqSim package is importable.
• assumptions: public assumptions and required follow-up.

Engineering Method

Reservoir pressure declines linearly with recovery factor between the initial and abandonment pressure: P = Pi - (Pi - Pabn) * (Gp / Vrec). Cumulative production Gp accrues at the constant offtake rate each step until the recoverable volume is reached or the abandonment pressure is hit. Water cut follows a supplied linear trend, and the water rate is derived from the hydrocarbon rate and the water-cut fraction. The verdict is high once the reservoir is depleted, watch past a configurable recovery-factor threshold, otherwise ok.

This skill performs no PVT, aquifer, injection, or coning physics. It is a transparent placeholder that must be replaced by a validated NeqSim reservoir tank model for any quantitative use.

Python Usage Pattern

from reservoir_depletion_screening import ReservoirDepletionModel

model = ReservoirDepletionModel()
result = model.evaluate(
    fluid_type="gas",
    initial_pressure_bara=300.0,
    abandonment_pressure_bara=80.0,
    recoverable_volume_sm3=20.0e9,
    offtake_rate_sm3_per_day=8.0e6,
    years=15,
    initial_water_cut_fraction=0.05,
    water_cut_rise_per_year=0.03,
)

for step in result.steps:
    print(step.year, step.pressure_bara, step.recovery_factor, step.water_cut_fraction)
print(result.depletion_warning)

Validated NeqSim Path

This screening is a placeholder. For real reservoir-vs-time behaviour use:

• NeqSim SimpleReservoir with addGasProducer / addOilProducer / addWaterInjector / addGasInjector and a runTransient(deltat) time loop.
• NeqSim MCP runReservoir for an orchestrated reservoir tank simulation.
• The enterprise well-production-routing-agent for live-data, IPR + tubing, and Beggs & Brills arrival modelling.

Escalation

Escalate any watch or high verdict, and any quantitative use, to a validated NeqSim reservoir model and qualified reservoir-engineering review.

Validation Checklist

• Inputs are validated and within stated ranges.
• Examples use public data only.
• Screening assumptions are stated explicitly.
• Limitations are respected.
• Quantitative use is escalated to validated NeqSim models.

Common Mistakes

Limitations

• Educational screening only; not a validated design method.
• No confidential data or proprietary methods are included.
• Escalate any quantitative or design use to validated NeqSim workflows.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md