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Reservoir EngineeringThermal Gradients

Volumetric Heat Capacity of a Reservoir Formula

Mr=(1ϕ)Ms+ϕSoMo+ϕSwMw+ϕSg[fgMg+(1fg)(LvρsΔT+ρsCw)]M_r=(1-\phi)M_s+\phi S_oM_o+\phi S_wM_w+\phi S_g\left[f_gM_g+(1-f_g)\left(\frac{L_v\rho_s}{\Delta T}+\rho_sC_w\right)\right]

Volumetric Heat Capacity of a Reservoir calculates volumetric heat capacity of reservoir for thermal gradients workflows in reservoir engineering.

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How engineers use this formula

Use this formula when the listed inputs (M_s, phi, S_o, M_o, S_w, M_w, S_g, f_g, M_g, rho_s, C_w, Delta_T, L_v) are known and the assumptions behind the cited thermal gradients relationship match the engineering case being checked.

Assumptions

  • Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
  • The declared units match the field-unit constants used in the formula.
  • The cited formula applies to the selected petroleum engineering workflow.

Limitations

  • The calculation does not replace a full engineering model or operating procedure.
  • Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.

Common mistakes

  • Mixing unit systems without converting the inputs.
  • Using default example values as field recommendations.
  • Applying the formula outside the source assumptions.

Default example

Using the default inputs, M_r equals 38.2115 BTU/(ft3*deg F).

M_sBTU/(ft3*deg F)

35

phifraction

0.25

S_ofraction

0.6

M_oBTU/(ft3*deg F)

45

S_wfraction

0.3

M_wBTU/(ft3*deg F)

62

S_gfraction

0.1

f_gfraction

0.2

M_gBTU/(ft3*deg F)

1

rho_slbm/ft3

2.65

C_wBTU/(lbm*deg F)

1

Delta_Tdeg F

100

L_vBTU/lbm

950

Inputs

M_s

BTU/(ft3*deg F)

Volumetric Heat Capacity of Rock Solids

phi

fraction

Porosity

S_o

fraction

Oil Saturation

M_o

BTU/(ft3*deg F)

Volumetric Heat Capacity of Oil

S_w

fraction

Water Saturation

M_w

BTU/(ft3*deg F)

Volumetric Heat Capacity of Water

S_g

fraction

Gas Saturation

f_g

fraction

Fraction of Non-Condensable Gas

M_g

BTU/(ft3*deg F)

Volumetric Heat Capacity of Non-Condensable Gas

rho_s

lbm/ft3

Source Density Term Used in the Condensable-Gas Heat Capacity Contribution

C_w

BTU/(lbm*deg F)

Isobaric Specific Heat of Water

Delta_T

deg F

Temperature Differential

L_v

BTU/lbm

Latent Heat of Vaporization

Outputs

M_r

BTU/(ft3*deg F)

Volumetric Heat Capacity of Reservoir

M_s

BTU/(ft3*deg F)

Volumetric Heat Capacity of Rock Solids

Source and review

reviewed

Thermal Recovery, Prats, M. (1986)

Prats, M. 1986. Thermal Recovery, Society of Petroleum Engineers, Chapter 12, Page 164.

source conflict
Source

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