Connate Water and Rock Expansion Term Formula
Connate Water and Rock Expansion Term calculates connate water and rock expansion term for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (B_ti, c_w, S_wi, c_f, Delta_p) are known and the assumptions behind the cited material balance and production 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, E_fw equals 0.0264 RB/STB.
1.25
0.000004
0.25
0.00001
1440
Inputs
B_ti
RB/STBInitial Two-Phase Formation Volume Factor
c_w
1/psiWater Compressibility
S_wi
fractionInitial Water Saturation
c_f
1/psiFormation Compressibility
Delta_p
psiCumulative Pressure Drop
Outputs
E_fw
Connate Water and Rock Expansion Term
B_ti
Initial Two-Phase Formation Volume Factor
c_w
Water Compressibility
S_wi
Initial Water Saturation
c_f
Formation Compressibility
Delta_p
Cumulative Pressure Drop
Source and review
reviewedPetroleum Office. Material Balance Overview; expansion terms in Havlena-Odeh notation.
Source