GT-04 · Aerated Drilling Control

Hole depth 2,846 m MD · Formation: Andesite fractured zone

GT-04 · Four-phase inputs

Editable dummy case
Basis: steady-state screening over 200 depth segments. The four phases are drilling liquid, injected air, generated cuttings, and formation fluid/steam. The model applies ideal-gas expansion, phase-specific slip correction, constant average temperature, user-supplied annular friction, and a loss sink for blind drilling. It is not a transient, field-calibrated production or well-control model.

Calculated operating point

GT-04 base case
PhaseSourceDensitySlipAverage holdupLocal rate
Pore 0.86 sgECD 0.91 sgFrac 1.02 sg
✓
PASS · Four-phase state is inside the blind-drilling envelope

Hydraulic and transport margins are available.

Step-by-step formulas

SI units
1 · Annular areaA = π/4 × (Dₕ² − Dₚ²)

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2 · Phase continuity∂(αₖρₖA)/∂t + ∂(αₖρₖvₖA)/∂z = Γₖ + qₖ,in − qₖ,loss

Steady-state phase rates include injected liquid and air, bit-generated solids, and formation influx.

3 · Slip-corrected phase holdupwₖ = Qₖ/Sₖ; αₖ = wₖ/Σwⱼ; Σαₖ = 1

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4 · Mixture density and momentumρₘ = Σαₖρₖ; ΔP = Σ(ρₘgΔz) + ΔPfric + ΔPacc

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5 · Loss–influx balanceQreturn = max[0, ΣQₖ,bh − Qloss]

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6 · Equivalent circulating densityECD = (ΔPhyd + ΔPfric) / (0.00980665 × TVD)

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7 · Compressor power screeningW = [k/(k−1)] × P₁Q₁/η × [(P₂/P₁)^((k−1)/k)−1]

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Engineering calculation sheet

One-well example
Decision rule: maintain ECD above the pore-pressure equivalent plus the approved operational margin, and below fracture gradient minus the approved loss margin. Stop or re-model when returns, SPP, temperature, gas rate, or formation response departs from the calibrated envelope.