Total compressibility
Total compressibility of the rock and its fluids from the saturations and the oil, water, gas and pore compressibilities, and the storativity φ·c_t: inputs to well test interpretation, radius of investigation and diffusivity.
c_t = S_o · c_o + S_w · c_w + S_g · c_g + c_fS_o = 1 − S_w − S_g, β* = φ · c_tThe pore compressibility c_f is per pore volume, as in the Western literature; in Shchelkachev's β* = m · β_l + β_r the rock compressibility β_r is per bulk volume, i.e. β_r = φ · c_f. Below the bubble point the oil compressibility includes the gas coming out of solution (take it from PVT).
Source: Earlougher, Advances in Well Test Analysis, SPE Monograph 5 (1977), ch. 2; storativity: V. N. Shchelkachev
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Usually the connate water, 0.15–0.35.
0 above the bubble point.
Undersaturated oil, from PVT: (0.7–3)·10⁻³ MPa⁻¹ (5–20·10⁻⁶ psi⁻¹).
(3.7–5)·10⁻⁴ MPa⁻¹ (2.5–3.5·10⁻⁶ psi⁻¹).
Needed only when S_g > 0; c_g ≈ 1/p: about 0.05 MPa⁻¹ at 20 MPa.
Per pore volume; from core, usually (4–15)·10⁻⁴ MPa⁻¹ (3–10·10⁻⁶ psi⁻¹).
For the storativity φ · c_t.
Unit converter for this formulaCompressibility · Fraction and percent
- MPa⁻¹1
- bar⁻¹0.1
- atm⁻¹0.101325
- (kgf/cm²)⁻¹0.0980665
- psi⁻¹0.00689476
- S_o — Oil saturation–
- β* — Storativity φ · c_t–
More in Reservoir fluid properties (PVT)
Viscosity of degassed oil at standard conditions from its density, for oil with a density of 0.845 to 0.924 g/cm³, in mPa·s.
Viscosity of degassed oil at standard conditions from its density, for oil with a density of 0.78 to 0.845 g/cm³, in mPa·s.
Viscosity of degassed oil at a given temperature from its laboratory viscosity and the coefficient a, in mPa·s. The coefficient c is chosen from the viscosity: 10 for μ > 1000, 100 for 10 ≤ μ ≤ 1000, 1000 for μ < 10.
Coefficient a for converting the viscosity of degassed oil to another temperature. The coefficients b and c are chosen from the viscosity: b = 0.00252 and c = 10 for μ > 1000; b = 0.00144 and c = 100 for 10 ≤ μ ≤ 1000; b = 0.00076 and c = 1000 for μ < 10.
Viscosity of gas-saturated oil at reservoir conditions from the degassed oil viscosity and the correlation coefficients A and B, in mPa·s.
Coefficients A and B for the viscosity of gas-saturated oil, from the gas-oil ratio at 15 °C and atmospheric pressure.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.