Coupled aquifer-borehole simulation

Area of Science:

• Hydrogeology
• Fluid Dynamics
• Numerical Modeling

Background:

• Accurate simulation of fluid flow in wells and aquifers is crucial for groundwater resource management.
• Existing models often simplify or neglect the complex interactions between borehole flow and aquifer inflow.
• Understanding head losses and flow dynamics within the wellbore is essential for efficient well performance.

Purpose of the Study:

• To develop and validate a coupled numerical model for fluid hydraulics in a borehole and aquifer system.
• To investigate the influence of wellbore screen inflow on vertical fluid flow and head variation within the borehole.
• To integrate this enhanced wellbore flow model into a widely used groundwater flow code (MODFLOW-2000).

Main Methods:

• Development of a one-dimensional, steady-state model for vertical borehole flow coupled with radial aquifer flow.
• Incorporation of conservation of momentum principles, considering both laminar and turbulent flow regimes.
• Inclusion of wellbore screen inflow effects using Siwoń's (1987) relation and iterative linearization of nonlinear momentum equations.
• Integration of the borehole model into MODFLOW-2000 by calculating conductance terms for vertical wellbore flow.

Main Results:

• The coupled model accurately predicts vertical head variation, accounting for inflow through the wellbore screen.
• Inflow through the wellbore screen can reduce predicted vertical head variation by up to 15% compared to models without this effect.
• The model demonstrates favorable agreement with previously published results when adjusted to match their assumptions.
• The study quantifies the impact of fluid acceleration and friction losses (Colebrook-White formulation) in the wellbore.

Conclusions:

• The developed coupled model provides a more realistic representation of fluid flow dynamics in wells and aquifers.
• Accounting for wellbore screen inflow significantly impacts head loss calculations and overall well performance predictions.
• The integration into MODFLOW-2000 offers a practical tool for enhanced groundwater resource assessment and management.
• This approach improves the accuracy of groundwater modeling by capturing complex wellbore-aquifer interactions.