Buildup Pressure for Steam or Gas Flow
Buildup pressure, abbreviated as BHP, is the increase in pressure observed within a wellbore after the flow of steam, gas, or other fluids is restricted or stopped. This is often measured during shut-in periods, when the well is temporarily closed off, allowing pressures to stabilize.
Causes of Buildup Pressure
Thermal Expansion - For steam or gas, heat transfer into surrounding formations can cause expansion, contributing to pressure increases.
Reservoir Recharge - Fluids from the reservoir migrate into the wellbore when flow is restricted.
Compression Effects - For gas or steam, the residual volume compresses, increasing pressure.
Permeability and Porosity Effects - Formation characteristics determine how quickly fluids flow into the wellbore.
Buildup Pressure for Steam or Gas Flow Formula |
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| \( p_b \;=\; \dfrac{ MW \cdot k \cdot h \cdot ( \rho_i^2 - \rho_{ws}^2 ) }{ 0.01291 \cdot q \cdot \eta \cdot Z \cdot T_a } \) | ||
| Symbol | English | Metric |
| \( p_b \) = Buildup Pressure |
- | \(dimensionless \;pressure\) |
| \( MW \) = Molecular Weight | - | \(g \;/\; g -mol \) |
| \( k \) = Effective Permability of Flowing Phase | - | \(D\) |
| \( h \) = Net Formation Thickness | - | \(m\) |
| \( \rho_i \) (Greek symbol rho) = Initial Reservoir Pressure (psi) | - | \(Pa\) |
| \( \rho_{ws} \) (Greek symbol rho) = Shut in Pressure (psi) | - | \(Pa\) |
| \( q \) = Production Rate | - | \(tons \;/\; hr\) |
| \( \eta \) (Greek symbol eta) = Flowing Fluid Viscosity | - | \(cP\) |
| \( Z \) = Real Gas Law Deviation Factor | - | \(dimensionless\) |
| \( T_a \) = Formation Absolute Temperature | - | \(K\) |
