{
  "version": 1,
  "topic": "MB04",
  "title": "Net to gross gross thickness and net pay in volumetrics",
  "createdAt": "2026-10-24",
  "case": {
    "title": "Gross thickness to net thickness",
    "premise": "160 acres and 100 ft gross thickness; φ = 0.15, Sw = 0.25, Bg = 0.005 ft³/scf. NTG is applied once.",
    "formula": "hnet = 100 NTG; G = 43,560 A hnet φ(1 − Sw)/Bg",
    "variables": "NTG is a fraction under a stated interpretation cutoff, not another porosity factor.",
    "steps": [
      {
        "label": "Define the baseline",
        "calculation": "Net-to-gross (fraction) = 0.5",
        "explanation": "160 acres and 100 ft gross thickness; φ = 0.15, Sw = 0.25, Bg = 0.005 ft³/scf. NTG is applied once."
      },
      {
        "label": "Select the relation",
        "calculation": "hnet = 100 NTG; G = 43,560 A hnet φ(1 − Sw)/Bg",
        "explanation": "NTG is a fraction under a stated interpretation cutoff, not another porosity factor."
      },
      {
        "label": "Substitute the values",
        "calculation": "100 × 0.5 = 50 ft net; G = 7,840,800,000 scf on the baseline rock and fluid inputs",
        "explanation": "Retain intermediate precision. The displayed values are rounded only after evaluation."
      },
      {
        "label": "Read the result",
        "calculation": "Net thickness (ft) = 50; Gas in place (scf) = 7840800000",
        "explanation": "Do not apply NTG again if the supplied thickness is already net pay."
      }
    ],
    "result": "Net thickness (ft) = 50; Gas in place (scf) = 7840800000",
    "interpretation": "Do not apply NTG again if the supplied thickness is already net pay.",
    "control": "Net-to-gross (fraction)",
    "columns": [
      "Net-to-gross (fraction)",
      "Net thickness (ft)",
      "Gas in place (scf)"
    ],
    "rows": [
      [
        0.25,
        25,
        3920400000
      ],
      [
        0.4,
        40,
        6272640000
      ],
      [
        0.5,
        50,
        7840800000
      ],
      [
        0.75,
        75,
        11761200000
      ],
      [
        1,
        100,
        15681600000
      ]
    ],
    "baseline": 2,
    "rowNotes": [
      "Net-to-gross (fraction) = 0.25. Net thickness (ft): 25; Gas in place (scf): 3920400000.",
      "Net-to-gross (fraction) = 0.4. Net thickness (ft): 40; Gas in place (scf): 6272640000.",
      "Net-to-gross (fraction) = 0.5. Net thickness (ft): 50; Gas in place (scf): 7840800000.",
      "Net-to-gross (fraction) = 0.75. Net thickness (ft): 75; Gas in place (scf): 11761200000.",
      "Net-to-gross (fraction) = 1. Net thickness (ft): 100; Gas in place (scf): 15681600000."
    ],
    "provenance": "Original synthetic teaching calculation. Equations and fixed controls are stated here; these are not field measurements.",
    "questions": [
      {
        "question": "Reproduce the baseline Net thickness (ft) without rounding intermediate values.",
        "answer": "100 × 0.5 = 50 ft net; G = 7,840,800,000 scf on the baseline rock and fluid inputs. Net thickness (ft) = 50. Do not apply NTG again if the supplied thickness is already net pay."
      },
      {
        "question": "Compare the first and last recorded scenarios. Which input changes?",
        "answer": "Net-to-gross (fraction) changes from 0.25 to 1. Other controls remain as stated in the premise. Net thickness (ft) changes from 25 to 100."
      },
      {
        "question": "What would be needed to apply this example to a different physical system?",
        "answer": "Replace the synthetic controls with compatible documented inputs and check the relation's assumptions. NTG is a fraction under a stated interpretation cutoff, not another porosity factor. Do not apply NTG again if the supplied thickness is already net pay."
      }
    ]
  },
  "recorded": null
}