petrophysics · water saturation
Bulk Volume Hydrocarbon
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Inputs
fraction
fraction
Description
Computes the bulk volume of hydrocarbon — the fraction of total rock volume occupied by hydrocarbon — as the product of porosity and hydrocarbon saturation (1−Sw). It is the direct complement of Bulk Volume Water (BVW=φ×Sw): the same two inputs, split the other way, giving a quick per-depth screen of hydrocarbon volume rather than water volume.
Variables
| Symbol | Unit | Description |
|---|---|---|
| BVH | fraction | Bulk Volume Hydrocarbon |
| φ | fraction | Effective or total porosity at the depth of interest — use the same porosity curve used for the Sw calculation. |
| Sw | fraction | Water saturation from Archie or another Sw model at the same depth as the porosity value. |
Assumptions
- Porosity and Sw used together come from the same depth and are internally consistent (same porosity definition)
- Sw already reflects the appropriate saturation model for the formation (Archie for clean, a shaly-sand model otherwise)
- Rock type (grain size, sorting) is reasonably uniform across the interval being compared
Limitations
- A trivial product of two other calculated quantities — errors in either φ or Sw propagate directly and multiplicatively into BVH
- Not itself a producibility indicator the way BVW is (BVW's near-constant-at-Swirr signature has no BVH analog) — use alongside BVW/net pay cutoffs, not as a standalone pay flag
- Does not account for hydrocarbon type (oil vs. gas) or formation volume factor — this is a rock-volume fraction, not a stock-tank or standard-condition volume
Use Cases
- → Quick relative pay-quality ranking: Compare BVH across depths or zones to rank hydrocarbon volume per unit rock without a full volumetric (area × thickness × recovery factor) calculation.
- → Sanity-check against OOIP/GIIP inputs: Cross-check the φ×(1−Sw) term used inside Reservoir's OOIP/GIIP volumetrics before combining it with area and thickness.
- → BVW/BVH pair QC: Confirm BVW+BVH sums to the same porosity value used for both — a mismatch signals an inconsistent φ or Sw was used between the two calculations.
Related Calculations
Region Notes
Permian Basin
Wolfcamp/Spraberry tight sands/carbonates: BVH in the 0.08-0.14 range at typical Sw≈0.3-0.4 and φ≈0.10-0.20 marks solid pay; lower BVH intervals are usually cut by the net pay Sw/φ thresholds anyway.
Gulf of Mexico
Higher-porosity unconsolidated sands with low Sw can show BVH above 0.15-0.20 — always cross-check against BVW to confirm the Sw used is realistic rather than an artifact of a poorly calibrated Rw.
Global
Because BVH and BVW always sum to φ, plotting both together (or BVH alone) across a log interval is a fast way to visually spot where hydrocarbon volume is concentrated without re-deriving Sw and φ mentally at each depth.
References
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